SiC single crystal substrate

Abstract

Provided is a SiC single crystal substrate having characteristics that have not been achieved in an 8-inch SiC single crystal substrate. This SiC single crystal substrate (1) is an 8-inch SiC single crystal substrate having a diameter in the range of 195-205 mm, a thickness in the range of 300-650 [mu] m, an SORI of 50 [mu] m or less, and an in-plane deviation of the substrate thickness of 1.5 [mu] m or less, the in-plane deviation of the substrate thickness being the difference between the maximum value and the minimum value of the substrate thickness at four points on a circumference between the center of the substrate and a half radius of the substrate.

Description

[0001] This application is a divisional application of the Chinese patent application with the application date of June 2, 2023, application number 202310646269.6, and invention name “SiC single crystal substrate”. Technical Field

[0002] The present invention relates to a SiC single crystal substrate. Background Art

[0003] Compared with silicon (Si), silicon carbide (SiC) has an insulation breakdown electric field that is one order of magnitude larger and a band gap that is three times larger. In addition, silicon carbide (SiC) has characteristics such as a thermal conductivity that is about three times higher than that of silicon (Si). Therefore, it is expected that silicon carbide (SiC) will be applied to power devices, high-frequency devices, high-temperature operating devices, etc. Therefore, in recent years, SiC epitaxial wafers are used for semiconductor devices such as the above.

[0004] SiC epitaxial wafers are obtained by stacking SiC epitaxial layers on the surface of SiC single crystal substrates. Hereinafter, the substrate before stacking the SiC epitaxial layer is referred to as SiC single crystal substrate, and the substrate after stacking the SiC epitaxial layer is referred to as SiC epitaxial wafer. SiC single crystal substrates are cut out from SiC single crystal ingots.

[0005] The current market mainstream of SiC single crystal substrates is 6-inch (150mm) diameter SiC single crystal substrates, but the development of mass production of 8-inch (200mm) SiC single crystal substrates is also advancing, and formal mass production is gradually starting. Through the improvement of production efficiency and cost reduction achieved by the large-diameter from 6 inches to 8 inches, we expect the further popularization of SiC power devices, which are the trump card of energy-saving technology.

[0006] When manufacturing the next generation of large-diameter SiC single crystal substrates, even if the manufacturing conditions optimized in the manufacture of the current diameter SiC single crystal substrates are applied, the same degree of quality cannot be obtained. This is because new problems will arise corresponding to the new size. For example, the following problem is recorded in Patent Document 1: When manufacturing a 6-inch SiC single crystal substrate, if the manufacturing technology of a 4-inch SiC single crystal substrate is applied, thermal decomposition of the outer peripheral side of the seed crystal will occur frequently, and the thermal decomposition will cause macroscopic defects, so that a single crystal with high crystalline quality cannot be obtained with a good yield. Patent Document 1 records an invention that solves this problem by using a seed crystal of a predetermined thickness. In this way, it will be necessary to solve the new problems corresponding to the new size while establishing the manufacturing conditions of the SiC single crystal substrate of the new size.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent No. 6594146

[0010] Patent Document 2: Japanese Patent No. 6598150

[0011] Patent Document 3: Japanese Patent Application Publication No. 2020-17627

[0012] Patent Document 4: Japanese Patent Application Publication No. 2019-189499 Summary of the invention

[0013] Problems to be solved by the invention

[0014] The SiC single crystal substrate is obtained through a SiC single crystal ingot manufacturing process and a SiC single crystal substrate process for manufacturing a SiC single crystal substrate from the SiC single crystal ingot. To establish a manufacturing technology for 8-inch SiC single crystal substrates, it is necessary to solve new problems unique to 8-inch substrates in the SiC single crystal ingot manufacturing process and the SiC single crystal substrate process.

[0015] Here, new problems unique to 8-inch substrates also include, for example, obtaining an 8-inch substrate having the same dislocation density as that in a 6-inch substrate during the SiC single crystal ingot manufacturing process. In the case where an 8-inch substrate is manufactured by simply applying the manufacturing technology of SiC single crystal substrates optimized for the manufacture of 6-inch substrates, an 8-inch substrate having a dislocation density greater than that in a 6-inch substrate will be produced. This is because when the size becomes larger, the difficulty of obtaining the same quality will increase significantly. Therefore, when evaluating the manufacturing technology of 8-inch SiC single crystal substrates, the dislocation density of the 8-inch substrate obtained by simply applying the manufacturing technology of SiC single crystal substrates optimized for the manufacture of 6-inch substrates should be used as the starting point, and the technical value should be evaluated based on the degree of improvement achieved by taking the dislocation density at this starting point as a benchmark.

[0016] On the other hand, the yield of mass-produced 8-inch SiC single crystal substrates is determined by the same or more stringent evaluation criteria as those for 6-inch SiC single crystal substrates. Step-by-step improvements have gradually led to the establishment of manufacturing technology for 8-inch SiC single crystal substrates.

[0017] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a SiC single crystal substrate having characteristics that have not yet been achieved in an 8-inch SiC single crystal substrate.

[0018] Technical solutions to solve problems

[0019] The present invention provides the following technical solutions to solve the above problems.

[0020] Solution 1 of the present invention is a SiC single crystal substrate, which is an 8-inch SiC single crystal substrate with a diameter in the range of 195 to 205 mm, a thickness in the range of 300 to 650 μm, a SORI of less than 50 μm, and an in-plane deviation of the substrate thickness of less than 1.5 μm, wherein the in-plane deviation of the substrate thickness is the difference between the maximum and minimum values ​​of the substrate thickness at four points on a circle with a radius of half the substrate and the center of the substrate.

[0021] Aspect 2 of the present invention is the SiC single crystal substrate according to the above aspect, wherein the SORI is 40 μm or less.

[0022] Aspect 3 of the present invention is the SiC single crystal substrate according to the above aspect, wherein the SORI is 30 μm or less.

[0023] A fourth aspect of the present invention is the SiC single crystal substrate according to the above aspect, wherein the SORI is 20 μm or less.

[0024] A fifth aspect of the present invention is the SiC single crystal substrate according to the above aspect, wherein the in-plane variation of the substrate thickness is 1.0 μm or less.

[0025] Solution 6 of the present invention is a SiC single crystal substrate according to the above solution, the micropipe defect density is 1 / cm 2 The total number of etch pits revealed by KOH etching at 550°C for 10 minutes is 5×10 9 Less than .

[0026] Solution 7 of the present invention is a SiC single crystal substrate according to the above solution, wherein the total number of the etch pits is 5×10 8 Less than .

[0027] Solution 8 of the present invention is a SiC single crystal substrate according to the above solution, wherein the total number of the etch pits is 5×10 7 Less than .

[0028] Aspect 9 of the present invention is that according to the SiC single crystal substrate of the above aspect, the density of the etch pits identified as threading dislocations in the etch pits is 2×10 3 Pieces / cm 2 Below, the density of the etch pits identified as basal plane dislocations is 5×10 3 Pieces / cm 2 the following.

[0029] Effects of the Invention

[0030] According to the SiC single crystal substrate of the present invention, it is possible to provide a SiC single crystal substrate having characteristics that have not yet been achieved in an 8-inch SiC single crystal substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1It is a schematic plan view of a SiC single crystal substrate according to the present embodiment.

[0032] Figure 2 It is a conceptual diagram showing the definition of SORI.

[0033] Figure 3 1 is a conceptual diagram showing a process of reducing the depth of the process-induced degradation layer by machining.

[0034] Figure 4 It is a schematic cross-sectional view of a SiC single crystal manufacturing apparatus.

[0035] Figure 5 It is a schematic cross-sectional view of another example of the SiC single crystal production apparatus.

[0036] Fig. 6A This is a schematic cross-sectional view of a driving unit that moves a heat insulating material up and down in a SiC single crystal manufacturing apparatus.

[0037] Figure 6B This is a schematic cross-sectional view of a driving unit that moves a heat insulating material up and down in a SiC single crystal manufacturing apparatus.

[0038] Figure 6C This is a schematic cross-sectional view of a driving unit that moves a heat insulating material up and down in a SiC single crystal manufacturing apparatus.

[0039] Fig. 7A The positional relationship between the lower surface of the heat insulator and the surface of the single crystal, and the relationship between the isothermal surface near the single crystal are shown.

[0040] Figure 7B The positional relationship between the lower surface of the heat insulator and the surface of the single crystal, and the relationship between the isothermal surface near the single crystal are shown.

[0041] Figure 7C The positional relationship between the lower surface of the heat insulator and the surface of the single crystal, and the relationship between the isothermal surface near the single crystal are shown.

[0042] Fig. 8A FIG. 1 is a diagram schematically showing the shape of an isothermal surface near a single crystal during crystal growth.

[0043] Figure 8B FIG. 1 is a diagram schematically showing the shape of an isothermal surface near a single crystal during crystal growth.

[0044] Description of Reference Numerals

[0045] 1SiC single crystal substrate DETAILED DESCRIPTION

[0046] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings as appropriate. In the accompanying drawings used in the following description, in order to make the features of the present invention easy to understand, the parts that will become features are enlarged for convenience, and the dimensional ratios of the various components are sometimes different from the actual ones. The materials, dimensions, etc. illustrated in the following description are only examples, and the present invention is not limited thereto, and can be implemented by appropriately changing within the scope of realizing the effects of the present invention. In addition, in each figure, the components known to those skilled in the art other than the components to be described in the figure are sometimes omitted.

[0047] (SiC single crystal substrate)

[0048] Figure 1 It is a schematic plan view of a SiC single crystal substrate according to the present embodiment.

[0049] Figure 1 The SiC single crystal substrate 1 shown is an 8-inch SiC single crystal substrate with a diameter in the range of 195 to 205 mm, a thickness in the range of 300 to 650 μm, a SORI of 50 μm or less, and an in-plane variation of the substrate thickness of 2.0 μm or less.

[0050] The outer shape of the SiC single crystal substrate 1 is not particularly limited, and various flat plate shapes and thicknesses can be used, and a disk shape is typical. The thickness of the SiC single crystal substrate can be, for example, in the range of 300 to 650 μm.

[0051] The SiC single crystal substrate 1 is preferably 4H-SiC. This is because, although SiC has various polytypes, 4H-SiC is mainly used to manufacture practical SiC devices.

[0052] One side of the SiC single crystal substrate 1 is a surface (primary surface) on which a SiC epitaxial layer is formed, and the primary surface is preferably a c-plane (the (0001) plane of a 4H-SiC crystal) or a surface inclined at an inclination angle (offset angle) greater than 0 degrees and less than 10 degrees relative to the c-plane. It is a 4H-SiC type single crystal wafer. Preferably, the off-angle is greater than 0 degrees and less than 10 degrees relative to the c-plane in the <11-20> direction.

[0053] Since the larger the off angle, the fewer wafers can be obtained from the SiC single crystal ingot, the smaller the off angle is, the better it is from the perspective of cost reduction. The off angle of the SiC single crystal substrate can be, for example, 0.4° to 5°. As an off angle that enables step flow growth, 0.4° is the lower limit.

[0054] The SiC single crystal substrate may contain impurities depending on the application, such as nitrogen (n-type), boron, aluminum (p-type), etc., to adjust the conductivity or resistivity.

[0055] The main surface (hereinafter sometimes referred to as the "front surface") of the SiC single crystal substrate 1 is a mirror surface. This is because the front surface of the SiC single crystal substrate needs to form a SiC epitaxial layer by epitaxial growth of a SiC single crystal in order to manufacture various SiC devices. Therefore, a substrate (a portion that becomes a substrate) is cut from a SiC single crystal ingot manufactured using a sublimation method or the like, and a SiC single crystal substrate is formed by mirror finishing the front surface of the cut substrate.

[0056] The other side (hereinafter sometimes referred to as the "back side") may not be a mirror surface, but a SiC single crystal substrate whose front side is a mirror surface and whose back side is not a mirror surface has the following problem: a difference in residual stress will be generated between the front side and the back side, and the substrate will warp to compensate for the residual stress (Twyman effect). By making the back side also a mirror surface, the warping of the substrate caused by the Twyman effect can be suppressed. A method for producing a SiC single crystal substrate with small warping even when the front side is a mirror surface and the back side is a non-mirror surface has been developed (for example, refer to Patent Document 2).

[0057] The SiC single crystal substrate 1 has a notch 2 serving as an index of crystal orientation, but may have an OF (orientation flat) instead of the notch 2 .

[0058] The SORI of the SiC single crystal substrate 1 is 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and further preferably 20 μm or less.

[0059] SORI is one of the parameters that indicates the warpage state of the substrate, and is expressed by the sum of the normal distances from the least squares plane to the highest point and the lowest point on the substrate surface when the measurement is performed in a manner that the back of the substrate is supported without changing the original shape. The least squares plane is a plane calculated using all the data on the substrate surface by the least squares method. That is, Figure 2 As shown, when the least squares plane of the substrate surface is used as the reference height (least squares plane height), it represents the total value ((a) + (b)) of the distance (a) between the height at the highest point on the substrate surface and the reference height and the distance (b) between the height at the lowest point on the substrate surface and the reference height.

[0060] The thickness of the process-induced degradation layer on both the front and back surfaces of the SiC single crystal substrate 1 is preferably 0.1 nm or less.

[0061] <Relationship between process-induced degradation layer and SORI>

[0062] The SiC single crystal substrate is produced by slicing a SiC single crystal ingot and flattening the surface. If such mechanical processing is performed, processing deformation will be introduced into the surface of the substrate. The portion of the surface of the SiC single crystal substrate that has undergone processing deformation is called a processing deformation layer. In the case where there is a processing deformation layer on the front and back sides, a difference in processing deformation occurs between the front and back sides, and a difference in residual stress also occurs, resulting in warping of the substrate due to the Twyman effect. The shape (warping) of the substrate is determined by the balance of the stress state generated by the processing deformation layers on both sides of the substrate.

[0063] Figure 3 The conceptual diagrams show the process of reducing the depth d (d1, d2, d3, d4) of the processed modified layer by mechanical processing. For example, (a) is a cross section near the surface after the grinding process, (b) is a cross section near the surface after the polishing process, (c) is a cross section near the surface after the fine grinding process, and (d) is a cross section near the surface after the CMP process.

[0064] FIG. 14 of Patent Document 3 shows the relationship between the depth of the process-induced degradation layer and SORI of a single crystal SiC wafer. According to the graph, the deeper the depth of the process-induced degradation layer, the greater the value of SORI. In addition, when comparing a 6-inch SiC single crystal substrate and a 4-inch SiC single crystal substrate, the 6-inch SiC single crystal substrate is more susceptible to the influence of the process-induced degradation layer, and the SORI is greater. Therefore, it is speculated that when comparing an 8-inch SiC single crystal substrate and a 6-inch SiC single crystal substrate, the 8-inch SiC single crystal substrate is further susceptible to the influence of the process-induced degradation layer, and the SORI becomes further greater. Therefore, for an 8-inch SiC single crystal substrate, it is more important to remove the process-induced degradation layer in order to reduce warpage compared to a 6-inch SiC single crystal substrate.

[0065] The in-plane variation of the substrate thickness of the SiC single crystal substrate 1 is 2.0 μm or less. The in-plane variation of the thickness is preferably 1.5 μm or less, and more preferably 1.0 μm or less.

[0066] In the SiC single crystal substrate according to the present embodiment, the in-plane variation in thickness is reduced by polishing using a new polishing slurry.

[0067] In this specification, the thickness of the SiC single crystal substrate is measured at five points (one point at the center and four points at half the radius ( Figure 1 In the figure symbols 1a to 1e), the "in-plane deviation of the substrate thickness" is represented by the difference between the maximum value and the minimum value.

[0068] FIG. 14 of Patent Document 3 shows the relationship between the depth of the process-induced degradation layer, a parameter of the process-induced degradation layer, and SORI. However, when developing an 8-inch SiC single crystal substrate with a high yield, the inventors paid attention to the in-plane deviation of the depth of the residual process-induced degradation layer. It is conceivable that even if the process-induced degradation layer can be almost completely removed by flattening the substrate at the laboratory level and taking sufficient time, some process-induced degradation layer will remain if the flattening process is performed in a practical amount of time. In addition, regarding the residual process-induced degradation layer, in Figure 3 The depth d of the process-induced degradation layer conceptually shown in FIG. 1 is drawn based on an assumed average depth. In reality, it does not remain at a strictly uniform depth. It is considered that the process-induced degradation layer remains thinly over the entire surface with some variation in depth within the surface, or the process-induced degradation layer remains locally within the surface. In this case, it is speculated that the in-plane variation in the depth of the process-induced degradation layer has a greater influence on SORI in the case of an 8-inch SiC single crystal substrate than in the case of a 6-inch SiC single crystal substrate.

[0069] It is considered that the in-plane variation in the substrate thickness of the SiC single crystal substrate 1 reflects the in-plane variation in the depth of the process-induced degradation layer.

[0070] The density of micropipe defects in the SiC single crystal substrate 1 is preferably 1 micropipe defect / cm 2 the following.

[0071] The total number of etch pits revealed by KOH etching of the SiC single crystal substrate 1 is preferably 5×10 9 less than 5×10 8 less than 5×10 7 In this case, KOH etching was performed at 550° C. for 10 minutes.

[0072] It should be noted that the total number of etch pits is equivalent to the total number of dislocations.

[0073] Preferably, the density of the etch pits identified as threading dislocations (TD) in the etch pits of the SiC single crystal substrate 1 is 2×10 3 Pieces / cm 2 Below, the density of the etch pits identified as basal plane dislocations is 5×10 3 Pieces / cm 2 the following.

[0074] The density of the etch pits identified as threading dislocations (TD) is more preferably 1×10 3 Pieces / cm 2 Below, more preferably 5×10 2 Pieces / cm 2 the following.

[0075] The density of etch pits identified as basal plane dislocations is more preferably 2×10 3 per cm 2 or less, and further preferably 1×10 3 per cm 2 or less, and even more preferably 5×10 2 per cm 2 or less.

[0076] Here, a threading dislocation is a dislocation that combines a threading screw dislocation (TSD) and a threading edge dislocation (TED).

[0077] It should be noted that the type of dislocation can be determined using an optical microscope or the like based on the shape of the etch pits revealed by KOH etching, and the number of etch pits per unit area can be counted. Generally, etch pits with a medium hexagonal shape correspond to threading screw dislocations (TSD), etch pits with a small hexagonal shape correspond to threading edge dislocations (TED), etch pits with an elliptical shape (shell shape) correspond to basal plane dislocations (BPD). In addition, etch pits with a large hexagonal shape correspond to microtubes (MP).

[0078] (Method for manufacturing SiC single crystal substrate)

[0079] Regarding the method for manufacturing the SiC single crystal substrate according to the present embodiment, it will be described by dividing it into a process of manufacturing an SiC single crystal ingot and a process of manufacturing an SiC single crystal substrate from the ingot.

[0080] <Process of manufacturing SiC single crystal ingot>

[0081] In the process of continuous in-depth research, the present inventors found that: when manufacturing an 8-inch diameter SiC single crystal ingot, compared with a 6-inch diameter SiC single crystal ingot, more stringent control of the temperature gradient in the radial direction and the vertical direction (crystal growth direction) becomes the key point. And it was found that: by applying the method disclosed in Patent Document 4, more stringent control of the temperature gradient in the radial direction and the vertical direction (crystal growth direction) can be achieved. Specifically, an SiC single crystal manufacturing apparatus having a heat insulating member that can move along the extending direction of a guiding member outside the guiding member for guiding crystal growth can be used. It should be noted that the method for more stringent control of the temperature gradient in the radial direction and the vertical direction (crystal growth direction) is not limited to the method disclosed in Patent Document 4.

[0082] During the transition period of SiC single crystal ingots with larger diameters, the problem of not being able to obtain large-diameter SiC single crystal ingots with the same crystal quality will be encountered when the previous method of making SiC single crystal ingots with the same diameter is applied. During the transition period from 4-inch diameter SiC single crystal ingots to 6-inch diameter SiC single crystal ingots, for example, the following problems arise (see Patent Document 1).

[0083] In the growth of SiC single crystals by the sublimation recrystallization method using a seed crystal, as one of the growth conditions for achieving high crystal quality, it is necessary to make the surface shape of the single crystal ingot during growth substantially convex in the growth direction. <0001> When the SiC single crystal grows roughly parallel to the axis, that is, the c-axis direction of the crystal, the single crystal growth is carried out by the development of spiral steps that are successively sent out from the screw dislocation. Therefore, it is said that by becoming roughly convex, the step supply source on the growth surface becomes essentially one place, which can improve the polymorphic stability. In the case where it is assumed that the growth surface has a concave surface or multiple tops, the supply source of the growth step becomes multiple places, thereby generating parts where different steps successively sent out from each supply source collide with each other. In such a case, not only defects such as dislocations will be generated from the parts that collide with each other, but the atomic stacking state in the c-axis direction unique to the 4H type polytype is also easily disordered, so that heterogeneous polytypes with different stacking structures such as 6H type and 15R type will be generated, and micropipe defects will be generated.

[0084] Therefore, for example, in order to stabilize the 4H polytype suitable for power devices and grow a so-called single polytype crystal consisting only of the 4H polytype, it is important to make the growth surface shape of the growing crystal roughly convex. Specifically, the convex shape of the growing crystal is achieved by optimizing the temperature of the center of the growing crystal and controlling the temperature distribution during growth, that is, the isothermal shape, from the perspective of the growth rate, etc. It is generally believed that the SiC single crystal ingot grown under such growth conditions that achieve a roughly convex isotherm will grow in a manner roughly parallel to the isotherm, which can ensure the above-mentioned polytype stability.

[0085] However, when the diameter of the growing crystal is increased to 150 mm (6 inches) or more, if the temperature of the center of the growing crystal is optimized to the same temperature as the previous 100 mm (4 inches) diameter single crystal growth from the perspective of growth speed, and the temperature gradient during growth is controlled so that the growth surface shape of the growing crystal becomes roughly convex in the growth direction, then the temperature of the peripheral portion of the seed crystal will become higher than that of the small-diameter crystal growth. As a result, the SiC single crystal of the seed crystal itself is easily thermally decomposed at the peripheral portion of its outer peripheral side. With regard to this problem, in Patent Document 1, the problem is solved by using a seed crystal formed of a silicon carbide single crystal with a thickness of 2.0 mm or more as the main solution.

[0086] In the present invention, when manufacturing an 8-inch diameter SiC single crystal ingot, as a method not used in the typical 6-inch diameter SiC single crystal ingot manufacturing method shown in Patent Document 1, a heat insulating member that can move along the extension direction of the guide member outside the guide member that guides crystal growth is used to control not only the radial temperature gradient but also the vertical temperature gradient (crystal growth direction), thereby successfully manufacturing an 8-inch diameter SiC single crystal ingot having characteristics comparable to those of a 6-inch diameter SiC single crystal ingot. The following describes a SiC single crystal manufacturing device and a manufacturing process of a SiC single crystal ingot.

[0087] Figure 4 It is a schematic cross-sectional view of an example of a SiC single crystal production apparatus for carrying out a production process of a SiC single crystal ingot.

[0088] Figure 4 The SiC single crystal production apparatus 100 shown in the figure includes a crucible 10, a seed crystal installation portion 11, a guide member 20, and a heat insulator 30. Figure 4 In FIG. 1 , for easy understanding, a raw material G, a seed crystal S, and a single crystal C obtained by crystal growth on the seed crystal S are shown simultaneously.

[0089] In the following drawings, the direction in which the seed crystal installation portion 11 and the raw material G face each other is referred to as the up-down direction, and the direction perpendicular to the up-down direction is referred to as the left-right direction.

[0090] The crucible 10 surrounds a film forming space K for growing the single crystal C. The crucible 10 can be any crucible used to make the single crystal C by the sublimation method, and a known crucible can be used. For example, graphite, tantalum carbide, etc. can be used. The crucible 10 reaches a high temperature during growth. Therefore, it needs to be formed of a material that can withstand high temperatures. For example, the sublimation temperature of graphite is extremely high at 3550°C, and it can withstand even the high temperature during growth.

[0091] The seed crystal installation portion 11 is provided at a position in the crucible 10 facing the source material G. Since the seed crystal installation portion 11 is provided at a position facing the source material G, the source material gas can be efficiently supplied to the seed crystal S and the single crystal C.

[0092] The guide member 20 extends from the periphery of the seed crystal installation portion 11 toward the source material G. That is, the guide member 20 is disposed along the crystal growth direction of the single crystal C. Therefore, the guide member 20 functions as a guide when the single crystal C grows from the seed crystal S.

[0093] The lower end of the guide member 20 is supported by a support body 21. The support body 21 blocks the space between the lower end of the guide member 20 and the crucible 10, and suppresses the intrusion of the raw material gas into the region outside the guide member 20. If the raw material gas intrudes into this region, polycrystals will grow between the guide member 20 and the heat insulating material 30, and the free movement of the heat insulating material 30 will be hindered.

[0094] The connection between the guide member 20 and the support body 21 is preferably a riveted structure. The riveted structure is a structure designed to tighten the connection between the guide member 20 and the support body 21 when a physical force is applied to the guide member 20. For example, a threaded structure after the connection part is threaded is an example of a riveted structure. The guide member 20 may sometimes physically contact the single crystal C that is undergoing crystal growth, and in this case, the guide member 20 can be prevented from falling off.

[0095] Figure 4 The guide member 20 in the embodiment extends vertically in the up-down direction. The shape of the guide member 20 is not limited to this shape. Figure 5 It is a schematic cross-sectional view of another example of the SiC single crystal production apparatus 101 according to the present embodiment. Figure 5 The guide member 25 in the embodiment is expanded in diameter from the seed crystal installation portion 11 toward the raw material G. By expanding the diameter of the guide member 25 , the diameter of the single crystal C can be enlarged.

[0096] in addition, Figure 4 Although the upper end of the guide member 20 is open, the upper end of the guide member 20 may be connected to the inner surface of the crucible 10 so that the space where the heat insulating member 30 exists becomes a closed space.

[0097] The surface of the guide member 20 is preferably coated with tantalum carbide. The guide member 20 controls the flow of the raw gas and is therefore always exposed to the raw gas. If the guide member 20 is used in a graphite-exposed manner, the graphite reacts with the raw gas and is sometimes degraded and damaged. If degraded and damaged, openings will be generated in the guide member 20. In addition, carbon powder peeled off due to degradation is taken into the single crystal C, which will also become a cause of deterioration in the quality of the single crystal C. In contrast, tantalum carbide can withstand high temperatures and will not react unnecessarily with the raw gas. Therefore, high-quality SiC single crystal growth can be stably performed.

[0098] The heat insulator 30 moves outside the guide member 20 along the extending direction of the guide member 20. By moving the heat insulator 30, the positional relationship between the end surface of the heat insulator 30 on the source material G side (hereinafter referred to as the lower surface 30a) and the surface Ca of the single crystal C can be controlled. Therefore, the temperature distribution near the surface Ca of the single crystal C can be freely controlled, and the surface shape of the single crystal C undergoing crystal growth can be freely controlled.

[0099] During the crystal growth process, the positional relationship between the end surface 30 a of the heat insulator 30 on the source material side and the surface Ca of the single crystal C can be controlled.

[0100] Furthermore, during the crystal growth process, the end surface 30 a of the heat insulator 30 on the source material side can be located within 20 mm from the surface Ca of the single crystal C.

[0101] Furthermore, during the crystal growth process, the end surface 30 a of the heat insulator 30 on the source material side can be arranged closer to the seed crystal installation portion 11 than the surface Ca of the single crystal C.

[0102] In addition, the thickness of the heat insulating material 30 can be set to be less than half of the growth amount of the SiC single crystal ingot to be produced with a thickness of 0.2 mm or more.

[0103] FIG6 is a cross-sectional schematic diagram of a driving unit for moving the heat insulating member 30 up and down. The driving unit is not particularly limited as long as it can move the heat insulating member 30 up and down. Fig. 6A As shown, a driving member 31 extending from the upper portion of the heat insulating member 30 to the outside of the crucible 10 may be provided, and the heat insulating member 30 may be moved by pushing and pulling the driving member up and down. Figure 6B As shown in FIG. 1 , the heat insulating member 30 may be supported from below and a lifting driving member 32 may be provided. Figure 6C As shown, a notch may be provided at a portion of the side surface of the crucible 10 , and a driving member 33 may be provided to extend to the outside of the crucible 10 through the notch, and the heat insulating member 30 may be moved by lifting and lowering the driving member.

[0104] The heat insulating member 30 is preferably made of a material having a thermal conductivity of 40 W / mk or less at a high temperature of 2000°C or more. Examples of materials having a thermal conductivity of 40 W / mk or less at a high temperature of 2000°C or more include graphite members having a thermal conductivity of 120 W / mk or less at room temperature. In addition, the heat insulating member 30 is more preferably made of a material having a thermal conductivity of 5 W / mk or less at a high temperature of 2000°C or more. Examples of materials having a thermal conductivity of 5 W / mk or less at a high temperature of 2000°C or more include felt members having graphite or carbon as a main component.

[0105] The shape of the heat insulator 30 is appropriately designed to match the shape of the region sandwiched between the guide member 20 and the inner surface of the crucible 10. Figure 4 As shown in FIG. 1 , when the distance between the guide member 20 and the inner surface of the crucible 10 is constant, the heat insulating material 30 is arranged so as to fill the space between them. Figure 5 As shown, when the distance between the guide member 25 and the inner surface of the crucible 10 changes, the shape of the heat insulator 35 is designed to match the position where the distance between them becomes the narrowest. By designing in this way, it is possible to avoid the heat insulator 35 being stuck between the guide member 25 and the inner surface of the crucible 10 and becoming unable to move.

[0106] The thickness of the thermal insulation 30 is preferably 0.2 mm or more, more preferably 5 mm or more, and further preferably 20 mm or more. If the thickness of the thermal insulation 30 is too thin, it is sometimes impossible to exert a sufficient thermal insulation effect. In addition, the thickness of the thermal insulation 30 is preferably less than half of the length of the single crystal finally manufactured. Here, the length of the single crystal means the length in the up and down direction of the single crystal C after the crystal growth (the growth amount of the single crystal C). When the growth amount of the single crystal is 100 mm, the thickness of the thermal insulation 30 is preferably less than 50 mm. If the growth amount of the single crystal is 50 mm, the thickness of the thermal insulation 30 is preferably less than 25 mm. If the thickness of the thermal insulation 30 is too thick, it will hinder the movement of the thermal insulation 30. In addition, if the thickness of the thermal insulation 30 is within this range, a temperature difference can be formed in the up and down directions in the single crystal C through the thermal insulation 30. Therefore, it is possible to prevent the recrystallization of the raw material gas on the surface Ca of the single crystal C other than the surface Ca.

[0107] As described above, according to the above-mentioned SiC single crystal manufacturing apparatus, the position of the heat insulating member can be controlled relative to the single crystal undergoing crystal growth. By controlling the position of the heat insulating member, the temperature distribution near the surface of the single crystal C during crystal growth can be freely controlled. Since the single crystal C grows along the isothermal surface, controlling the temperature distribution near the surface of the single crystal C will result in the shape of the single crystal C being controlled.

[0108] When making a SiC single crystal ingot, the above-mentioned SiC single crystal manufacturing apparatus can be used. Figure 4 The case of the SiC single crystal manufacturing apparatus 100 shown in the figure will be described as an example.

[0109] In the manufacturing process of the SiC single crystal ingot, a single crystal C is grown from a seed crystal S set in the seed crystal setting part 11. The single crystal C grows by recrystallizing the raw material gas sublimated from the raw material G on the surface of the seed crystal S. The raw material G is sublimated by heating the crucible 10 by a heating unit provided outside. The sublimated raw material gas is supplied toward the seed crystal S along the guide member 20.

[0110] In the process of producing a SiC single crystal ingot, the positional relationship between the lower surface 30a of the heat insulator 30 and the surface Ca of the single crystal C is controlled during the crystal growth of the single crystal C from the seed crystal S. By controlling their positional relationship, the shape of the surface Ca of the single crystal C can be freely controlled.

[0111] FIG. 7 shows the positional relationship between the lower surface 30 a of the heat insulator 30 and the surface Ca of the single crystal C, and the relationship between the isothermal surface in the vicinity of the single crystal C. FIG. Fig. 7A This is an example of a case where the surface Ca (crystal growth surface) of the single crystal C is flat. Figure 7B This is an example of a case where the surface Ca (crystal growth surface) of the single crystal C is concave. Figure 7C This is an example of a case where the surface Ca (crystal growth surface) of the single crystal C is convex.

[0112] like Figure 7A to Figure 7C As shown in FIG. 1 , the shape of the surface Ca of the single crystal C changes depending on the position of the heat insulating member 30 relative to the surface Ca of the single crystal C. Fig. 7A As shown in FIG. 1 , when the positions of the surface Ca of the single crystal C and the lower surface 30a of the heat insulating member 30 are substantially the same, the surface Ca of the single crystal C becomes flat. Figure 7B As shown, when the lower surface 30a of the heat insulating member 30 is located closer to the raw material G than the surface Ca of the single crystal C, the surface Ca of the single crystal C becomes concave, as shown in FIG. Figure 7C As shown, when the surface Ca of the single crystal C is located closer to the source material G than the lower surface 30 a of the heat insulator 30 , the surface Ca of the single crystal C is convex.

[0113] The shape of the surface Ca of the single crystal C changes depending on the position of the heat insulator 30 relative to the surface Ca of the single crystal C because the shape of the isothermal surface T in the film forming space K changes. Fig. 8 schematically shows the shape of the isothermal surface T near the growing single crystal C. Fig. 8A This is a diagram showing a case where the heat insulating member 30 is not provided. Figure 8B This is a diagram showing a case where the heat insulating material 30 is provided.

[0114] The single crystal C of SiC has a low thermal conductivity and has a heat insulating effect. On the other hand, the thermal conductivity of the guide member 20 is higher than that of the single crystal C. Fig. 8A The isothermal surface T without the thermal insulator 30 is formed to extend from the single crystal C. The crystal growth surface of the single crystal C grows along the isothermal surface T. Therefore, without the thermal insulator 30, the shape of the surface Ca (crystal growth surface) of the single crystal C is fixed to a concave shape.

[0115] In contrast, if Figure 8BWhen the heat insulating member 30 is provided as shown, the shape of the isothermal surface T changes. The shape of the isothermal surface T can be freely designed by controlling the position of the heat insulating member 30 relative to the single crystal C. The shape of the isothermal surface T can be designed with high accuracy by confirming it in advance using simulation or the like. By controlling the position of the heat insulating member 30 relative to the single crystal C in this way, the shape of the surface Ca of the single crystal C can be freely designed.

[0116] Furthermore, if the position of the heat insulator 30 relative to the single crystal C is controlled, there is also an effect of suppressing adhesion of the polycrystal to the guide member 20 and reducing the temperature difference in the in-plane direction within the single crystal C.

[0117] Polycrystals are formed near the crystal growth surface of single crystal C, in the portion with low temperature. Fig. 8A As shown in FIG. 1 , when the temperature difference between the single crystal C and the guide member 20 is large, polycrystals grow on the guide member 20. If the polycrystals grown on the guide member 20 come into contact with the single crystal C, the crystallinity of the single crystal C is disrupted, which may cause defects. Figure 8B As shown, if the heat insulator 30 is present near the surface Ca of the single crystal C, the temperature difference between the single crystal C and the guide member 20 can be reduced, and the growth of the polycrystal can be suppressed.

[0118] In addition, if the temperature difference in the in-plane direction in the single crystal C is large, stress is generated during the growth process of the single crystal C. The stress generated in the single crystal C may cause deformation and displacement of the crystal plane. The deformation and displacement of the lattice plane in the single crystal C may cause fatal defects such as basal plane dislocation (BPD).

[0119] So far, the shape of the surface Ca of the single crystal C can be controlled. The shape of the surface Ca of the single crystal C is preferably flat or convex toward the raw material G. This is because, in the case where the shape of the surface Ca of the single crystal C is concave toward the raw material G, the quality is poor. In order to make the shape of the surface Ca of the single crystal C flat or convex, the positions of the surface Ca of the single crystal C and the lower surface 30a of the thermal insulation member 30 are made substantially the same, or the surface Ca of the single crystal C is set closer to the raw material G side than the lower surface 30a of the thermal insulation member 30.

[0120] Here, "substantially the same" does not mean that the positions of the surface Ca of the single crystal C and the lower surface 30a of the heat insulating member 30 are exactly at the same height, but means a positional shift within a range that allows for little impact on the isothermal surface T. Specifically, if the distance between the lower surface 30a of the heat insulating member 30 and the surface Ca of the single crystal C is within 30 mm, it can be said that the surface Ca of the single crystal C and the lower surface 30a of the heat insulating member 30 are in a substantially the same positional relationship. On the other hand, in order to make the shape of the surface Ca of the single crystal C flat, the positional relationship between the surface Ca of the single crystal C and the lower surface 30a of the heat insulating member 30 is preferably close to exactly the same, and the lower surface 30a of the heat insulating member 30 is preferably at a position within 20 mm from the surface Ca of the single crystal C, more preferably within 10 mm.

[0121] In addition, the surface Ca of the single crystal C is preferably located on the raw material G side with respect to the lower surface 30a of the heat insulating member 30. That is, the lower surface 30a of the heat insulating member 30 preferably exists on the seed setting portion 11 side with respect to the surface Ca of the single crystal C. Even when external factors such as temperature fluctuations in the film formation space K occur, it is possible to suppress the surface Ca of the single crystal C from becoming concave.

[0122] In addition, the position of the heat insulating member 30 is preferably controlled from the start of crystal growth. That is, it is preferable to control the positional relationship between the lower surface 30a of the heat insulating member 30 and the surface of the seed S at the start of crystal growth.

[0123] Just after the start of crystal growth, the seed setting portion 11 exists around the seed S, and the distance between the seed S and the crucible 10 is also short. Therefore, the isothermal surface T in the film formation space K is also affected by the temperatures (thermal conductivities) of these members. That is, the effect of using the heat insulating member 30 is most effectively exerted in the region where the single crystal C has grown more than 30 mm from the seed S. On the other hand, the effect of the heat insulating member 30 is not absent just after the start of crystal growth.

[0124] For example, in the case where the shape of the crystal growth surface of the single crystal C just after the start of crystal growth becomes concave without providing the heat insulating member 30, it is necessary to restore the shape of the crystal growth surface of the single crystal C to convex in the subsequent growth process. If the shape of the crystal growth surface changes from concave to convex during the growth process, stress will accumulate in the single crystal C, and defects will be likely to occur. Therefore, the position of the heat insulating member 30 is preferably controlled from the start of crystal growth. The positional relationship of the heat insulating member 30 with respect to the seed S can be designed in the same manner as the positional relationship between the heat insulating member 30 and the single crystal C during crystal growth.

[0125] <Manufacturing process of SiC single crystal substrate>

[0126] The process of making a SiC single crystal substrate from the obtained SiC single crystal ingot includes a planarization process of grinding using a predetermined grinding slurry and a process-induced degradation layer removal process. In the production of the SiC single crystal substrate, a characteristic slurry can be used for grinding. In addition, a known method can be used for the processing until the SiC single crystal substrate is obtained from the SiC single crystal ingot. The grinding process is described below.

[0127] Next, the polishing slurry that can be used will be described in detail.

[0128] In the processing process of the free abrasive method, for example, a slurry containing water, boron carbide abrasive and an additive for dispersing the boron carbide abrasive is poured between the upper platen and the lower platen, and pressure is applied to the SiC substrate 1 using the upper platen 21 and the lower platen to flatten the surface of the SiC substrate 1. The slurry used in the processing process is, for example, a slurry containing water as a main component. When a slurry containing water as a main component is used, the dispersibility of the boron carbide abrasive can be improved, and secondary agglomeration is not easy to occur in the processing process. In addition, when a slurry containing water as a main component is used, the surface of the upper platen side of the SiC substrate provided with a slurry supply hole is cleaned by direct supply of water, and the surface of the lower platen side without a slurry supply hole is cleaned by water supplied from the gap between the SiC substrate and the carrier. The slurry used in the grinding process is recovered to a tank and supplied again from the tank.

[0129] The modified Mohs hardness (14) of the boron carbide abrasive is slightly larger than the modified Mohs hardness (13) of the SiC substrate to be polished, but smaller than the modified Mohs hardness (15) of diamond. Therefore, by using such a slurry, it is possible to increase the processing speed while suppressing the generation of cracks in the SiC substrate with the modified Mohs hardness (13), and suppress the reduction of the particle size of the boron carbide abrasive.

[0130] The ratio of the boron carbide abrasive in the slurry is, for example, more than 15 mass % and less than 45 mass %, preferably more than 20 mass % and less than 40 mass %, more preferably more than 25 mass % and less than 35 mass %. The ratio of the boron carbide abrasive in the slurry is more than 15 mass %, which can improve the content of the boron carbide abrasive of the slurry and improve the processing speed of the grinding process. In addition, the ratio of the boron carbide abrasive in the slurry is less than 45 mass %, which can suppress the frequency and area of ​​contact between boron carbide abrasives, and easily suppress the reduction of the particle diameter of the boron carbide abrasive and the wear of the boron carbide abrasive.

[0131] The average particle size of the boron carbide abrasive in the slurry used in the processing step is, for example, 15 μm or more and 40 μm or less, preferably 25 μm or more and 35 μm or less. By using the boron carbide abrasive with an average particle size of 15 μm or more, it is easy to increase the processing speed of grinding the surface of the SiC substrate 1, and the additive described later can be fully attached to the surface, which is related to improving dispersibility and suppressing the reduction of particle size. In addition, by making the average particle size below 40 μm, it is easy to obtain the effect of suppressing the generation of cracks in the SiC substrate and the rupture of the SiC substrate, and it is possible to suppress the excessive attachment of the additive described later to the surface, and suppress the decrease in processing speed caused by the decrease in the contact area with the SiC substrate as the workpiece. In addition, by using such a boron carbide abrasive, it is easy to suppress the change of particle size before and after grinding. Here, the average particle size of the boron carbide abrasive is the average particle size of the boron carbide abrasive before processing. Since the ratio of the average particle sizes of the boron carbide abrasive before and after processing is greater than 0.91 and less than 1.2, the average particle size of the boron carbide abrasive after processing is, for example, greater than 14 μm and less than 48 μm, preferably greater than 23 μm and less than 42 μm.

[0132] Here, the average particle size of the boron carbide abrasive is measured based on the particle size distribution measured by laser scattered light measurement using a particle size distribution measuring device Mastersizer Hydro 2000MU (Spectris Corporation) or MT3000II (MicrotracBEL Corporation).

[0133] As additives, polyols, esters and salts thereof, homopolymers and salts thereof, copolymers, etc. can be used. As specific examples, one or more selected from glycerol, 1-vinyl imidazole, sodium methyl taurine of coconut fatty acid, sodium lauric acid amide ether sulfate, sodium myristic acid amide ether sulfate, polyacrylic acid, and acrylic acid-maleic acid copolymer can be used.

[0134] It is believed that these additives can improve the dispersibility of the boron carbide abrasive in the slurry.

[0135] The additive adheres to the surface of the boron carbide abrasive to prevent the boron carbide abrasives from directly contacting each other. Thus, the additive improves the dispersibility of the boron carbide abrasive in the slurry and prevents the particle size of the abrasive from decreasing during the processing step.

[0136] The ratio of the additive in the slurry is, for example, more than 3% by volume and less than 20% by volume, preferably more than 5% by volume and less than 15% by volume, more preferably more than 10% by volume and less than 15% by volume. Here, the ratio of the additive in the slurry refers to the ratio obtained by dividing the volume of additives (additive components) such as glycerol by the volume of the slurry. The additive in the slurry is in the above range, and it is necessary and sufficient to adhere to the surface of the boron carbide in the slurry, and the preferred dispersion of the boron carbide abrasive in the slurry can be obtained, and the particle size of the boron carbide abrasive in the processing step is easily suppressed to reduce.

[0137] For this grinding process, in the processing step, the processing speed of processing the surface of the SiC substrate is, for example, more than 14 μm / h and less than 45 μm / h, preferably more than 16 μm / h and less than 40 μm / h, more preferably more than 18 μm / h and less than 25 μm / h. The processing speed depends on the processing pressure and the average particle size of the boron carbide abrasive previously recorded. By making the processing speed less than 45 μm / h, it is easy to obtain the effect of suppressing the reduction of the particle size of the boron carbide abrasive and the wear of the boron carbide abrasive. By making the processing speed more than 14 μm / h, it is possible to increase the production volume. In the case where the grinding process is divided into multiple times, the processing speed obtained by dividing the total change of the plate thickness of the SiC substrate by the total of the processing time is within the above range, and the processing speed under any timing is preferably within the above range. That is, in the case of being divided into multiple times for grinding, it is preferred that the processing speed calculated in each time is within the above range.

[0138] Here, the processing speed is calculated based on the difference in the thickness of the SiC substrate 1 before and after the grinding process and the processing time. Specifically, the processing speed is calculated by the following method. The positions for measuring the thickness of the SiC substrate 1 are position 1c corresponding to the center of the SiC substrate in the state before the positioning edge OF is formed on the SiC substrate 1, position 1a that is 5 to 10 mm away from the midpoint of the positioning edge OF toward position 1c, position 1b that is on the same straight line c as positions 1a and 1c and is 5 to 10 mm away from the outer circumference of the SiC substrate 1 in the direction of position 1a, and positions 1d and 1e that are on a straight line perpendicular to the straight line c and are 5 to 10 mm away from the outer circumference of the SiC substrate 1 in the direction of position 1a. The thickness of the SiC substrate 1 at these five positions 1a to 1e is measured using an indicator (ID-C150XB, manufactured by Mitutoyo), and the obtained thickness is treated as the thickness of the SiC substrate 1. The machining speed is calculated by dividing the difference in thickness (μm) of the SiC substrate 1 before and after machining obtained in this way by the machining time (h).

[0139] The additive can be attached to the surface of the boron carbide abrasive in the slurry used in the processing step, thereby improving the dispersibility of the boron carbide abrasive and suppressing the contact of the boron carbide abrasive, thereby suppressing the reduction in the particle size of the boron carbide abrasive.

[0140] Specifically, the average particle size of the boron carbide abrasive after processing in the processing step can be more than 0.91 and less than 1.2 to suppress the variation of the particle size of the boron carbide abrasive. Here, the reason that this ratio comprises the numerical value greater than 1 is because: sometimes in the processing step, the boron carbide abrasive secondary agglomeration and the particle size of a part of the boron carbide abrasive can become larger than before processing.

[0141] In the past, the particle size of the boron carbide abrasive in the slurry was greatly reduced by the grinding process. Therefore, when the grinding process was performed again, it was necessary to add abrasive to the slurry each time. In addition, it was necessary to calculate the distribution of the particle size of the abrasive in the slurry depending on the number of times it was used in the grinding process each time, which was complicated management.

[0142] Thus, in this grinding process, the particle size of the boron carbide abrasive can be easily managed and cost reduction can be achieved. In addition, the environmental burden can be reduced and the generation of cracks can be suppressed.

[0143] In addition, in this grinding process, since the particle size of the boron carbide abrasive does not change much, it is possible to suppress the change of the processing speed in the grinding process, and the grinding process can be continued under the same conditions. This grinding process is particularly effective when using boron carbide with a modified Mohs hardness slightly larger than silicon carbide as the object to be ground as an abrasive. Since this grinding process uses such an abrasive and substrate, it is also possible to suppress the cracks that often occur when diamond is used as an abrasive and a SiC substrate is used as the object to be ground.

[0144] In addition, in this grinding process, since the reduction and wear of the particle size of the boron carbide abrasive can be suppressed, the deviation of the particle size of the boron carbide abrasive in the slurry in the grinding process decreases. The processing speed of the grinding process depends on the particle size of the abrasive used. In this grinding process, since the deviation of the particle size of the abrasive can be suppressed, the surface of the SiC substrate as a whole is processed by the abrasive of approximately equal particle size, and the in-plane deviation of the substrate thickness of the processed SiC substrate decreases.

[0145] [Example]

[0146] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

[0147] (Example 1)

[0148] First, use Figure 4A SiC single crystal ingot was produced using the SiC single crystal production apparatus shown in FIG.

[0149] First, as the seed crystal S, a 4H-SiC single crystal with a main surface having a deviation angle of 4° relative to the (0001) plane, a diameter of 200 mm, and a thickness of 5.0 mm was used. At the beginning of crystal growth, the crucible temperature was controlled in such a way that the temperature (Tr) of the side wall of the crucible body near the same height as the seed crystal surface was 30 to 150°C, the temperature (Tg) of the center of the seed crystal when looking down at the outer wall of the crucible cover was 50 to 250°C, and the temperature difference (ΔT) between Tr and Tg was 20 to 100°C. While the heat insulation 30 was moved step by step in coordination with the crystal growth so that the raw material side end face (lower surface) of the heat insulation 30 was closer to the cover side than the surface of the single crystal and the distance between the raw material side end face of the heat insulation 30 and the surface of the single crystal in the growth direction was within 10 mm, the crystal growth was carried out.

[0150] The SiC single crystal ingot thus obtained had a diameter of 208 mm and a height of 20.2 mm.

[0151] Next, the SiC single crystal ingot was processed by a known processing method to obtain an 8-inch SiC substrate having a (0001) plane with an off-angle of 4° and a thickness of 0.9 mm.

[0152] Regarding the SiC substrate, the following measurements were made: Figure 1 The thickness of the SiC substrate at the five positions shown was averaged and taken as the thickness of the SiC substrate.

[0153] Next, the SiC substrate with the thickness measured was placed on the carrier plate of the grinding device and ground. The grinding slurry was obtained by adding a predetermined amount of boron carbide abrasive and AD8 (10 volume %) as an additive to water and dispersing. As the boron carbide abrasive, a particle size of F320 (JIS R6001) was used. Here, the ratio of glycerol (made by Aichemitechno Co., Ltd.) as an additive in the slurry was 6 volume %.

[0154] Polishing was performed by a free abrasive system while supplying the polishing slurry at a supply rate of 16 L / min. The polishing slurry was used in a cyclic manner.

[0155] The driving condition of the grinding device during grinding is a processing pressure of 160g / cm 2 , lower platen speed 16rpm, upper platen speed 5.5rpm, center gear speed 2.8rpm, internal gear speed 6.0rpm, processing time 40 minutes.

[0156] After the grinding process, the particle size distribution of the boron carbide abrasive in the slurry was measured in the same manner as before the process, the plate thickness was measured in the same manner as before the process, and the processing speed was calculated. In the grinding process, the average processing speed of 15 SiC substrates was 18 μm / h.

[0157] After the measurement, the slurry used in the previous polishing process was supplied, and the second polishing process and measurement were performed while the slurry was circulated. In Example 1, this operation was repeated, and the polishing process and measurement were performed a total of 8 times.

[0158] Next, an etching step for removing the process-induced degradation layer and a CMP step for mirror polishing were performed, thereby obtaining the SiC single crystal substrate of Example 1.

[0159] (Example 2)

[0160] A SiC single crystal substrate was obtained under the same conditions as in Example 1, except that the temperature of the highest temperature point of the raw material was increased by 20°C during the production of the SiC single crystal ingot and the driving conditions of the grinding device during the grinding process were adjusted so that the in-plane deviation of the substrate thickness after grinding was smaller than that in Example 1.

[0161] (Comparative Example 1)

[0162] A SiC single crystal substrate was obtained under the same conditions as in Example 1, except that a SiC single crystal manufacturing apparatus without a thermal insulation member 30 was used, a seed crystal with a diameter of 150 mm was used as the seed crystal S, Tr, Tg and ΔT were not controlled during crystal growth, and a grinding slurry that did not contain an additive (AD8) was used in the grinding process.

[0163] (Comparative Example 2)

[0164] A SiC single crystal substrate was obtained under the same conditions as in Comparative Example 1 except that the temperature of the highest temperature point of the raw material was increased by 10°C.

[0165] (Comparative Example 3)

[0166] A SiC single crystal substrate was obtained under the same conditions as in Example 1 except that a SiC single crystal ingot was produced using a SiC single crystal production apparatus without the heat insulator 30 and a polishing slurry containing no additive (AD8) was used in the polishing step.

[0167] (Comparative Example 4)

[0168] A SiC single crystal substrate was obtained under the same conditions as in Comparative Example 3 except that the thickness of the seed crystal was changed to 4.0 mm and the temperature of the raw material maximum temperature point was increased by 80°C.

[0169] (Comparative Example 5)

[0170] A SiC single crystal substrate was obtained under the same conditions as in Comparative Example 3 except that the thickness of the seed crystal was changed to 3.5 mm and the temperature of the raw material maximum temperature point was increased by 70°C.

[0171] (evaluate)

[0172] Regarding the SiC single crystal substrates of Example 1, Example 2, and Comparative Examples 1 to 5, SORI, in-plane deviation of substrate thickness, number of micropipes, total number of dislocations, threading dislocation (TD) density, and basal plane dislocation density were evaluated. The number of micropipes, total number of dislocations, threading dislocation (TD) density, and basal plane dislocation density were evaluated using etch pits revealed by KOH etching at 550°C for 10 minutes. The results are shown in Table 1. The TD etch pit density in Table 1 is the density of the TSD etch pit density and the TED etch pit density combined.

[0173]

Table 1

[0174]

[0175] The microtubule density in Examples 1 and 2 and Comparative Examples 1 to 5 is 1 microtubule / cm 2 the following.

[0176] In Examples 1 and 2, compared with Comparative Examples 1 to 5, both SORI and substrate thickness were significantly reduced.

[0177] In addition, Examples 1 and 2 (8-inch substrates) exceeded the level of Comparative Examples 1 and 2 (6-inch substrates), the total number of etch pits was sufficiently reduced, and the TD etch pit density and BPD etch pit density were also greatly reduced. This result is considered to be the effect of more precise temperature control in Examples 1 and 2.

[0178] In addition, the total number of etch pits, TD etch pit density, and BPD etch pit density of Examples 1 and 2 (8-inch substrates) were significantly reduced compared to Comparative Examples 3 to 5 (8-inch substrates). From this result, it can be seen that in the production of 8-inch SiC single crystal substrates, more precise temperature control has a greater impact than in the production of 6-inch SiC single crystal substrates.

Claims

1. A SiC single crystal substrate, which is an 8-inch SiC single crystal substrate, The diameter is in the range of 195 to 205 mm. The thickness is in the range of 300 to 650 μm. The SORI is 20 μm or less, and the in-plane deviation of the substrate thickness is 1.5 μm or less, where the in-plane deviation of the substrate thickness is the difference between the maximum and minimum values ​​of the substrate thickness at four points on a circle with a radius of half the substrate and the center of the substrate.

2. The SiC single crystal substrate according to claim 1, The SORI is 14 μm or less.

3. The SiC single crystal substrate according to claim 1, The in-plane deviation of the substrate thickness is 1.3 μm or less.

4. The SiC single crystal substrate according to claim 1, The in-plane deviation of the substrate thickness is 1.0 μm or less.

5. The SiC single crystal substrate according to claim 1, The in-plane deviation of the substrate thickness is 0.9 μm or less.

6. The SiC single crystal substrate according to claim 1, The microtubule defect density is 1 / cm 2 The total number of etch pits revealed by KOH etching at 550°C for 10 minutes is 5×10 9 Less than .

7. The SiC single crystal substrate according to claim 6, The total number of the pits is 5×10 8 Less than .

8. The SiC single crystal substrate according to claim 7, The total number of the pits is 5×10 7 Less than .

9. The SiC single crystal substrate according to any one of claims 6 to 8, The density of the etch pits identified as threading dislocations is 2×10 3 Pieces / cm 2 Below, the density of the etch pits identified as basal plane dislocations is 5×10 3 Pieces / cm 2 the following.

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