SiC single crystal manufacturing method, SiC single crystal manufacturing apparatus, and SiC single crystal wafer

Abstract

The present invention addresses the problem of providing a new SiC single crystal body in which SiC sublimation is suppressed and internal stress is reduced.　In order to solve the problem, a SiC single crystal manufacturing method according to the present invention has a stress reduction step for reducing the internal stress of a SiC single crystal body by heating the SiC single crystal body at not less than 1800°C under an atmosphere including elements Si and C. In addition, a SiC single crystal manufacturing device according to the present invention is provided with: a body container that is formed from a SiC material and is capable of housing the SiC single crystal body; and a heating furnace that is capable of heating the body container at not less than 1800°C.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a SiC single crystal, an apparatus for producing a SiC single crystal, and a SiC single crystal wafer. [Background technology]

[0002] Silicon carbide (SiC) has superior material properties such as dielectric breakdown strength, thermal conductivity, and radiation resistance compared to silicon (Si), and research and development into it as a material for constructing electronic devices is currently underway.

[0003] Conventionally, the "warping" of SiC single crystal substrates has been recognized as a problem. For example, "warping" is a factor that causes the exposure distance to deviate from the focal length of the optical system during the exposure process, and also a factor that prevents proper wafer chucking.

[0004] To address this issue, a technology has been proposed that reduces the "warpage" caused by processing strain by subjecting the SiC single crystal substrate to an annealing heat treatment. For example, Patent Document 1 describes a technique in which, after double-side lapping, an annealing heat treatment is performed in a non-corrosive gas atmosphere at a temperature of 1300°C to 2000°C, which reduces "warpage" caused by processing strain. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-103650 [Non-patent literature]

[0006] [Non-Patent Document 1] Hiroyuki Matsunami, Tsunenobu Kimoto, Takashi Nakamura, and Noboru Otani (eds.), "Semiconductor SiC Technology and Applications," 2nd Edition, Nikkan Kogyo Shimbun, September 30, 2011, pp. 36-37 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, causes of "warpage" in SiC single crystal substrates include warpage caused by internal stress introduced during ingot growth, in addition to warpage caused by processing strain (the so-called Twyman effect) described in Patent Document 1. Warpage caused by internal stress becomes apparent when the diameter of the SiC single crystal substrate increases.

[0008] To reduce such internal stress, it is necessary to heat the substrate at a temperature close to that during ingot growth. However, heating at this temperature range causes excessive etching and thinning of the SiC single crystal substrate due to the sublimation of SiC.

[0009] In the invention described in Patent Document 1, for example, when a SiC single crystal substrate is subjected to an annealing heat treatment at a temperature exceeding 2000°C, a pyrolysis reaction occurs due to digestion, resulting in significant surface carbonization. This makes it difficult to suitably reduce the internal stress of the SiC single crystal substrate, which is a problem as the diameter increases.

[0010] Non-Patent Document 1 states that controlling the temperature distribution of the crystal reduces internal stress and solves the problem of ingot cracking in 4-inch ingots, but it is expected that the problem of internal stress will become even greater in the case of larger diameter ingots of 6 inches and 8 inches.

[0011] In view of the above-mentioned problems, an object of the present invention is to provide a novel SiC single crystal mass in which the internal stress is reduced while the sublimation of SiC is suppressed. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides a method for producing a SiC single crystal, which includes a stress reduction step of heating a SiC single crystal body at 1800°C or higher in an atmosphere containing Si and C elements to reduce the internal stress of the SiC single crystal body. By adopting such a configuration, the present invention can provide a novel SiC single crystal body in which internal stress is reduced while suppressing SiC sublimation.

[0013] In a preferred embodiment of the present invention, the stress reducing step heats the SiC single crystal body so as to prevent changes in thickness and diameter of the SiC single crystal body. By adopting such a configuration, the present invention can provide a novel SiC single crystal body in which internal stress is reduced while suppressing SiC sublimation.

[0014] In a preferred embodiment of the present invention, the stress reducing step heats the SiC single crystal body in a quasi-closed space. By adopting such a configuration, the present invention can heat the SiC single crystal body in a desired vapor pressure environment.

[0015] In a preferred embodiment of the present invention, the stress reducing step includes heating the SiC single crystal body in an atmosphere containing an inert gas. By adopting such a configuration, the present invention can heat the SiC single crystal body while suppressing SiC sublimation.

[0016] In a preferred embodiment of the present invention, the stress reducing step includes heating the SiC single crystal body to uniformize the temperature of the SiC single crystal body. By adopting such a configuration, the present invention can suppress the generation of internal stress due to temperature distribution in the SiC single crystal body.

[0017] In a preferred embodiment of the present invention, the method further comprises a heat treatment step of heating the SiC single crystal body and the SiC source body at 1400°C or higher in an atmosphere containing Si and C elements, the heat treatment step including an etching step and / or a growth step. By adopting such a configuration, the present invention can perform etching and crystal growth in the SiC single crystal body at a temperature lower than that in the stress reduction step.

[0018] In a preferred embodiment of the present invention, the heat treatment step involves heating the SiC single crystal body and the SiC source body so that the SiC single crystal body is on the high temperature side and the SiC source body is on the low temperature side, and then etching the SiC single crystal body. By adopting this configuration, the present invention can control the temperature difference between the SiC single crystal body and the SiC source body, and etch a SiC single crystal body with reduced internal stress.

[0019] In a preferred embodiment of the present invention, the heat treatment step heats the SiC single crystal body and the SiC source body so that the SiC single crystal body is on the low temperature side and the SiC source body is on the high temperature side, thereby growing the SiC single crystal body. By adopting such a configuration, the present invention can control the temperature difference between the SiC single crystal body and the SiC source body, thereby enabling crystal growth of a SiC single crystal body with reduced internal stress.

[0020] In a preferred embodiment of the present invention, the heat treatment step includes a step of heating the SiC single crystal body and the SiC source body in a semi-closed space in which the atomic ratio Si / C is equal to or less than 1. By adopting such a configuration, the present invention makes it possible to perform etching and crystal growth in a SiC single crystal body in which internal stress is reduced in a SiC-C equilibrium vapor pressure environment.

[0021] In a preferred embodiment of the present invention, the heat treatment step includes a step of heating the SiC single crystal body and the SiC source body in a semi-closed space in which the atomic ratio Si / C exceeds 1. By adopting such a configuration, the present invention makes it possible to perform etching and crystal growth in a SiC single crystal body in which internal stress is reduced in a SiC-Si equilibrium vapor pressure environment.

[0022] In a preferred embodiment of the present invention, the heat treatment step includes a strained layer removal step of etching the strained layer on the SiC single crystal body. By adopting such a configuration, the present invention can simultaneously reduce internal stress in the SiC single crystal body and remove the strained layer caused by mechanical processing or the like.

[0023] In a preferred embodiment of the present invention, the heat treatment step includes a bunching decomposition step of decomposing macrostep bunching on the SiC single crystal body and flattening the surface of the SiC single crystal body. By adopting such a configuration, the present invention can realize a flattened surface on the SiC single crystal body, which is terminated with steps having the height of a full unit in the SiC single crystal.

[0024] In a preferred embodiment of the present invention, the heat treatment step is carried out to reduce the BPD density to <100 / cm 2 By adopting such a configuration, the present invention can achieve both a reduction in internal stress in the SiC single crystal mass and a favorable BPD conversion.

[0025] In a preferred embodiment of the present invention, there is provided a method for producing a SiC single crystal body, which comprises the stress reducing step and the heat treatment step in this order. By adopting such a configuration, the present invention enables crystal growth of a high-quality growth layer on a SiC single crystal body whose internal stress has been reduced by the stress reducing step.

[0026] In order to solve the above problems, the present invention provides a SiC single crystal manufacturing apparatus including a main body container made of SiC material and capable of containing a SiC single crystal body, and a heating furnace capable of heating the main body container to 1800° C. or higher. By adopting such a configuration, the present invention can provide a novel SiC single crystal body in which internal stress is reduced while suppressing SiC sublimation.

[0027] In a preferred embodiment of the present invention, the heating furnace is capable of heating the SiC single crystal body while maintaining a uniform temperature. With this configuration, the present invention can suppress the generation of internal stress due to temperature distribution in the SiC single crystal body.

[0028] In a preferred embodiment of the present invention, the heating furnace has a high-melting-point container capable of accommodating the main container. With this configuration, the present invention can heat the SiC single crystal body in a desired vapor pressure environment.

[0029] In order to solve the above problems, the present invention provides a SiC single crystal wafer having a warpage of less than 30 μm and a diameter of 6 inches or more. By adopting this configuration, the present invention can provide a novel SiC single crystal body in which internal stress is reduced while suppressing SiC sublimation, and can contribute to the production of high-quality SiC devices.

[0030] In a preferred embodiment of the present invention, the SiC single crystal wafer has a BPD density of <100 / cm 2 With this configuration, the present invention can provide a SiC single crystal mass that is expected to reduce internal stress and suppress defect generation, and can contribute to the production of high-quality SiC devices.

[0031] In a preferred embodiment of the present invention, the SiC single crystal wafer has a BPD density of 5000 / cm 2 The substrate has the above structure. [Effects of the Invention]

[0032] According to the present invention, it is possible to provide a novel SiC single crystal mass in which the internal stress is reduced while the sublimation of SiC is suppressed.

[0033] Other objects, features and advantages will become apparent from a reading of the following detailed description when taken in conjunction with the drawings and claims. [Brief explanation of the drawings]

[0034] [Figure 1] 1 shows a schematic diagram of a stress reduction process according to one embodiment of the present invention. [Figure 2] 1 shows a schematic diagram of a stress reduction process according to one embodiment of the present invention. [Figure 3] 1 shows a schematic diagram of an etching process according to one embodiment of the present invention. [Figure 4] 1 shows a schematic diagram of an etching process according to one embodiment of the present invention. [Figure 5]1 shows a schematic diagram of a growth process according to one embodiment of the present invention. [Figure 6] 1 shows a schematic diagram of a growth process according to one embodiment of the present invention. [Figure 7] 1 shows a schematic diagram of a feedstock transport mechanism according to one embodiment of the present invention. [Figure 8] 1 illustrates an example of a combined stress reduction, etching, and growth step according to an embodiment of the present invention. [Figure 9] 1 illustrates an example of a combined stress reduction, etching, and growth step according to an embodiment of the present invention. [Figure 10] 1 illustrates an example of a combined stress reduction, etching, and growth step according to an embodiment of the present invention. [Figure 11] 1 shows an example of a manufacturing apparatus according to an embodiment of the present invention. [Figure 12] 10 shows an explanatory diagram of a method for calculating a BPD conversion rate according to a reference example. [Figure 13] 1 shows an explanatory diagram of a SiC wafer according to a reference example. [Figure 14] FIG. 1 is an explanatory diagram of a SiC wafer according to a reference example. [Figure 15] 1 is an Arrhenius plot according to a reference example. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The technical scope of the present invention is not limited to the embodiments shown in the accompanying drawings, and can be modified as appropriate within the scope of the claims.

[0036] An embodiment of the present invention includes at least a stress reducing step S0.

[0037] 1 , the stress reducing step S0 can be understood as reducing the amount of warpage 0d of the SiC single crystal body 1 by inducing slippage in the SiC single crystal body 1. It can also be understood as reducing the total thickness variation (TTV) of the SiC single crystal body 1.

[0038] The stress reduction step S0 can be understood to equalize the lattice distances of the SiC single crystal body 1, reduce the internal stress of the SiC single crystal body 1, reduce the thermal stress of the SiC single crystal body 1, or reduce the residual stress of the SiC single crystal body 1.

[0039] In addition, the stress reduction step S0 heats at least the SiC single crystal body 1 so as to suppress etching or crystal growth on the surface of the SiC single crystal body 1, so as to prevent changes in the thickness and diameter of the SiC single crystal body 1, so as to prevent changes in the volume of the SiC single crystal body 1, and so as to prevent changes in the dimensions and size of the SiC single crystal body 1.

[0040] As shown in FIG. 2, the stress reducing step S0 is a step of reducing at least the SiC single crystal mass 1 by x C y The heating is performed in an atmosphere containing Si and C elements, such as a silicon-based gas atmosphere. At this time, it can be understood that thermal decomposition, crystal growth, and the like occur successively in the SiC single crystal body 1, and the Si element and the C element circulate between the surfaces 1a and 1b of the SiC single crystal body 1 and the atmosphere containing the Si element and the C element.

[0041] Furthermore, in the stress reducing step S0, at least the SiC single crystal body 1 is heated in a quasi-closed space. In the description herein, the term "quasi-closed space" refers to a space that can be evacuated but that can confine at least a portion of the generated steam.

[0042] In the stress reducing step S0, the SiC single crystal body 1 is heated in an atmosphere containing an inert gas. The "inert gas" in the description herein refers to a known inert gas used in SiC processes, such as Ar gas.

[0043] In the stress reducing step S0, the SiC single crystal mass 1 is heated to a temperature range in which the SiC material sublimes, for example, 1800° C. or higher.

[0044] Furthermore, the stress reducing step S0 involves heating the SiC single crystal body 1 to uniformize the temperature in the SiC single crystal body 1. In the description herein, "uniformizing the temperature in the SiC single crystal body 1" refers to heating the SiC single crystal body 1 so that the temperature difference between the maximum and minimum temperatures in the SiC single crystal body 1 is within an allowable temperature difference, and refers to reducing the temperature gradient in the SiC single crystal body 1. The allowable temperature difference is preferably 50°C or less, preferably 20°C or less, preferably 10°C or less, preferably 5°C or less, preferably 2°C or less, and preferably 1°C or less.

[0045] In addition, Non-Patent Document 1 states that a moderate temperature gradient is necessary to induce crystal growth, but the presence of a temperature gradient inside the crystal leads to residual thermal stress in the crystal itself.

[0046] In addition, Non-Patent Document 1 states that depending on the temperature distribution, residual thermal stress may become excessively large in some areas, and particularly when growing large-diameter single crystals, the large residual thermal stress may cause frequent problems with crystal cracking.

[0047] In addition, Non-Patent Document 1 states that optimizing the temperature gradient in the crystal plane direction during growth to reduce internal stress is necessary to reduce stress components that have a significant effect on crystal cracking.

[0048] In addition, Non-Patent Document 1 states that by reducing the local stress that induces crystal cracking, it is possible to achieve single crystal growth without crystal cracking even in crystals with a diameter of 4 inches.

[0049] Thus, the influence of internal stress caused by temperature distribution in the SiC single crystal body 1 becomes a problem as the diameter of wafers and ingots increases. The effect of the internal stress in the SiC single crystal body 1 can be understood to be problematic, for example, when the diameter (caliber) of the SiC single crystal body 1 is 4 inches, and even more problematic, for example, when the diameter (caliber) of the SiC single crystal body 1 is 6 inches, 8 inches, or 12 inches.

[0050] In the stress reducing step S0, the SiC single crystal mass 1 is heated at a degree of vacuum that suppresses sublimation of the SiC material and raw material transport, which will be described later. The degree of vacuum is preferably 1.0 Pa or less, more preferably 10 -1 Pa or less, more preferably 10 -2 Pa or less, more preferably 10 -3 Pa or less, and more preferably 10 -4 Pa or less, and more preferably 10 -5 The degree of vacuum is preferably 10 Pa or less. -1 Pa or more, more preferably 10 -2 Pa or more, more preferably 10 -3 Pa or more, and more preferably 10 -4 Pa or more, and more preferably 10 -5 Pa or more, and more preferably 10 -6 Pa or more.

[0051] In the stress reducing step S0, the SiC source material 2 may be heated together with the SiC single crystal mass 1 in order to form the atmosphere containing the Si element and the C element.

[0052] In the stress reducing step S0, the SiC single crystal body 1 and the SiC source body 2 are brought close to each other and heated. In the description herein, "bringing close to each other" refers, for example, to reducing the separation distance d1 (not shown) between the SiC single crystal body 1 and the SiC source body 2.

[0053] The separation distance d1 is preferably 2.0 mm or less, more preferably 1.0 mm or less, even more preferably 0.5 mm or less, even more preferably 0.1 mm or less, and even more preferably 10 μm or less. The separation distance d1 is preferably 1.0 μm or more, more preferably 10 μm or more, even more preferably 0.1 mm or more, even more preferably 0.5 mm or more, and even more preferably 1.0 mm or more.

[0054] Furthermore, the stress reducing step S0 heats the SiC single crystal body 1 and the SiC source body 2 to reduce the chemical potential difference or vapor pressure difference between the surfaces of the SiC single crystal body 1 and the SiC source body 2. At this time, the chemical potential difference and vapor pressure difference correspond to the case where source material transport, which will be described later, does not occur.

[0055] Furthermore, the stress reducing step S0 heats the SiC single crystal mass 1 and the SiC source material 2 to reduce the temperature gradient between the SiC single crystal mass 1 and the SiC source material 2. In the description herein, "reducing the temperature gradient between the SiC single crystal mass 1 and the SiC source material 2" refers to, for example, heating the SiC single crystal mass 1 and the SiC source material 2 so that the temperature difference between them is within 10°C.

[0056] In addition, the stress reduction step S0 can be understood as heating the SiC single crystal body 1 and the SiC raw material body 2 so that either the SiC single crystal body 1 or the SiC raw material body 2 becomes the source or destination of raw material transport, and so that an equilibrium relationship is reached between the SiC single crystal body 1 and the SiC raw material body 2.

[0057] It can be understood that the stress reduction step S0 reduces the internal stress of the SiC single crystal body 1 and alleviates strain introduced during the formation of the three-dimensional structure so as to maintain the surface shape of the SiC single crystal body 1 having a three-dimensional structure such as a trench structure. Specifically, the stress reduction step S0 reduces the internal stress and strain of the SiC single crystal body 1 so as to suppress excessive etching (thickness reduction) of the sidewalls and / or bottom surface of the trench structure.

[0058] The SiC single crystal 1 may be a SiC ingot produced by a crystal growth method such as sublimation, or may be a SiC wafer sliced ​​into a disk shape from the SiC ingot. The polytype of the SiC single crystal 1 refers to known polytypes such as 3C, 4H, and 6H.

[0059] The cross-sectional size of the SiC single crystal body 1 is several centimeters square, 2 inches, 3 inches, 4 inches, 6 inches, 8 inches, or 12 inches. There is no limitation on the cross-sectional size.

[0060] The surface of the SiC single crystal body 1 may be configured to have an off-angle of several degrees (for example, 0.4 to 8.0 degrees) from the (0001) plane or the (000-1) plane. In the description of this specification, "-" refers to a bar in the notation of Miller indices.

[0061] The SiC source material 2 may be a SiC ingot produced by sublimation or the like, a SiC wafer sliced ​​into a disk shape from the SiC ingot, or polycrystalline SiC. The SiC raw material 2 may be a SiC single crystal, a SiC polycrystal, a SiC material that forms a semi-closed space, or a SiC material that is exposed within the semi-closed space.

[0062] An embodiment of the present invention further comprises a heat treatment step SX.

[0063] In the heat treatment step SX, the SiC single crystal 1 and the SiC raw material 2 are x C y The heating is performed in an atmosphere containing Si and C elements, such as a silicon-based gas atmosphere.

[0064] Furthermore, in heat treatment step SX, SiC single crystal body 1 and SiC source body 2 are heated in a temperature range lower than that in stress reducing step S0. This temperature range is preferably 1400°C or higher. In the description herein, the term "low temperature range" refers to a temperature range in which the minimum temperature is low.

[0065] Furthermore, the heat treatment step SX includes the etching step S1 and / or the growth step S2, and can be understood as having the effect of the etching step S1 or the effect of the growth step S2.

[0066] In the etching step S1, the SiC single crystal body 1 and the SiC source material 2 are heated so that the SiC single crystal body 1 is at a high temperature and the SiC source material 2 is at a low temperature, and the SiC single crystal body 1 is etched.

[0067] Furthermore, the etching step S1 can be understood to include a strained layer removal step S11 in which the SiC single crystal body 1 and the SiC raw material body 2 are placed in a semi-closed space in which the atomic ratio Si / C is 1 or less, and heated to etch the SiC single crystal body 1, or to have the effect of the strained layer removal step S11.

[0068] Furthermore, the etching step S1 can be understood to include a bunching decomposition step S12 in which the SiC single crystal body 1 and the SiC raw material body 2 are placed in a quasi-closed space in which the atomic ratio Si / C exceeds 1 and heated to etch the SiC single crystal body 1, or to have the effect of the bunching decomposition step S12.

[0069] As shown in FIG. 3, in the etching step S1, the SiC single crystal body 1 and the SiC source body 2 are heated so that the surface 1a of the SiC single crystal body 1 and the surface 2a of the SiC source body 2 are etched and crystals are grown, respectively.

[0070] Furthermore, as shown in FIG. 3, the etching step S1 can be understood as heating the SiC single crystal body 1 and the SiC source material 2 so that the SiC single crystal body 1 and the SiC source material 2 serve as the source and destination of source material transportation, respectively.

[0071] 4, the strained layer removal step S11 etches the strained layer 300 on the surface of the SiC single crystal mass 1. The strained layer 300 may include crystal dislocations 301 and / or damaged regions 302.

[0072] As shown in FIG. 4, the strained layer removal step S11 etches the SiC single crystal body 1 so as to expose a surface having steps 102a and terraces 102b with an elongated terrace length W2, or to expose a bunched surface.

[0073] 4, the bunching decomposition step S12 etches the surface 1a of the SiC single crystal mass 1 having steps 102a and terraces 102b to decompose the MSBs of the surface 1a so as to expose a surface having steps 103a and terraces 103b with a reduced terrace length W3, or to form a flattened bunching-free surface. At this time, the surface 1a is terminated with steps with the height of a full unit in the SiC single crystal.

[0074] As shown in FIG. 5, in the growth step S2, the SiC single crystal body 1 and the SiC source material 2 are heated so that the SiC single crystal body 1 is on the low temperature side and the SiC source material 2 is on the high temperature side, thereby causing crystal growth of the SiC single crystal body 1 and forming a growth layer 10 on the surface of the SiC single crystal body 1.

[0075] As shown in FIG. 5, in the growth step S2, the SiC single crystal body 1 and the SiC source body 2 are heated so that the surface 1a of the SiC single crystal body 1 and the surface 2a of the SiC source body 2 undergo crystal growth and etching, respectively.

[0076] As shown in FIG. 5, in the growth step S2, the SiC single crystal mass 1 and the SiC source material 2 are heated so that the SiC single crystal mass 1 and the SiC source material 2 serve as the source and destination of the source material transport, respectively.

[0077] Furthermore, the growth step S2 can be understood to include an epitaxial growth step S21 in which the SiC single crystal body 1 and the SiC raw material body 2 are placed in a semi-closed space in which the atomic ratio Si / C is 1 or less, and heated to cause crystal growth of the SiC single crystal body 1, or to have the effect of the epitaxial growth step S21.

[0078] Furthermore, the growth step S2 can be understood to include a bunching decomposition step S22 in which the SiC single crystal body 1 and the SiC raw material body 2 are placed in a quasi-closed space in which the atomic ratio Si / C exceeds 1 and heated to cause crystal growth of the SiC single crystal body 1, or to have the effect of the bunching decomposition step S22.

[0079] As shown in FIG. 6, the epitaxial growth step S21 performs crystal growth to form a growth layer 10 having steps 102a and terraces 102b with an elongated terrace length W2 on the surface of the SiC single crystal mass 1 having steps 101a and terraces 101b with a reduced terrace length W1, or to form a growth layer 10 having a bunched surface on the base substrate 11.

[0080] As shown in FIG. 6, the epitaxial growth step S21 is performed at a density of <100 / cm 2 Crystal growth is performed to form at least a portion of growth layer 10 so as to form a growth layer having a basal plane dislocation density (BPD density) of 1000 nm or so as to convert the BPDs in SiC single crystal body 1 into other defects / dislocations including threading edge dislocations (TEDs).

[0081] 6, the bunching decomposition step S22 involves growing a SiC single crystal body 1 so as to decompose the MSBs at the surface 1a, thereby forming a growth layer 10 having steps 103a and terraces 103b with a reduced terrace length W3 on the surface of the growth layer 10 having steps 102a and terraces 102b, or to form a growth layer 10 having a flattened bunching-free surface. At this time, the surface 1a is terminated with steps having the height of a full unit in the SiC single crystal.

[0082] In the description of this specification, the term "flattened bunching-free surface" refers to a SiC surface in which macrostep bunching (MSB) has been resolved. In the description of this specification, "MSB" refers to steps on the SiC surface that bunch to form a height exceeding the full unit of each polytype. That is, an MSB is a bunched step exceeding four molecular layers (five molecular layers or more) in the case of 4H-SiC, and a bunched step exceeding six molecular layers (seven molecular layers or more) in the case of 6H-SiC.

[0083] In the etching step S1, the SiC single crystal body 1 and the SiC source body 2 are heated so that the SiC single crystal body 1 and the SiC source body 2 serve as the source and destination of source material transport, respectively.

[0084] In the stress reducing step S0, the SiC single crystal body 1 and the SiC source body 2 are heated so that the SiC single crystal body 1 and the SiC source body 2 serve as a source and a destination of source material transport, respectively.

[0085] 7, in one embodiment of the present invention, the stress reducing step S0, the etching step S1, and the growth step S2 can be understood as each of the following reactions 1) to 5) occurring continuously. The reaction process of raw material transport for the etching step S1 will be illustrated below.

[0086] 1) SiC(s) → Si(v) + C(s) 2) 2C(s) + Si(v) → SiC2(v) 3) C(s) + 2Si(v) → SiC(v) 4) Si(v) + SiC2(v) → 2SiC(s) 5) SiC(v) → Si(v) + SiC(s)

[0087] Explanation of 1): When the surface 1a of the SiC single crystal 1 is thermally decomposed, Si atoms (Si(v)) are released from the surface 1a. Explanation of 2) and 3): When Si atoms (Si(v)) are desorbed, the C atoms (C(s)) remaining on the surface 1a react with the Si vapor (Si(v)) in the raw material transport space to become Si2C or SiC2, etc., which then sublimates into the raw material transport space. Explanation of 4) and 5): The sublimated SiC or SiC, etc. reaches and diffuses onto the terraces of the surface 2a of the SiC source body 2 due to, for example, a temperature gradient, and when it reaches the steps, it takes on the polymorphism of the surface 2a, and a growth layer 10 is formed while exhibiting a step-flow growth aspect.

[0088] Each of the stress reduction process S0, the etching process S1, and the growth process S2 can be understood to include a Si atom sublimation process in which Si atoms are thermally sublimated from the SiC raw material body 2, and a C atom sublimation process in which C atoms remaining on the surface 2a of the SiC raw material body 2 are sublimated by bonding with Si atoms in the raw material transport space.

[0089] In each of the stress reducing step S0, etching step S1, and growth step S2, the transported Si2C or SiC2, etc., becomes supersaturated on the surface 1a or 1b of the SiC single crystal body 1 and coagulates, thereby causing crystal growth.

[0090] Each of the stress reduction step S0, the etching step S1, and the growth step S2 includes a Si atom sublimation step in which Si atoms are thermally sublimated from the surface 1a or 1b of the SiC single crystal body 1, and a C atom sublimation step in which C atoms remaining on the surface 1a or 1b of the SiC single crystal body 1 are sublimated by bonding with Si atoms in the raw material transport space.

[0091] The stress reduction step S0 can be understood as reducing the temperature gradient between the SiC single crystal body 1 and the SiC source body 2, thereby suppressing source transport between the surface 1a and / or 1b and the surface 2a while maintaining the sublimation of SiC from each of the surfaces 1a, 1b, and 2a.

[0092] Furthermore, the stress reduction step S0 can be understood as reducing the vapor pressure difference at the surfaces of the SiC single crystal body 1 and the SiC source material 2, or as equalizing the vapor pressure difference at the surfaces of the SiC single crystal body 1 and the SiC source material 2, thereby suppressing source material transport between surface 1a and / or 1b and surface 2a while maintaining SiC sublimation from each of surfaces 1a, 1b, and 2a.

[0093] Furthermore, the stress reduction step S0 can be understood as reducing the chemical potential difference at the surfaces of the SiC single crystal body 1 and the SiC source material 2, or equalizing the chemical potential at the surfaces of the SiC single crystal body 1 and the SiC source material 2, thereby inhibiting source material transport between surface 1a and / or 1b and surface 2a while maintaining SiC sublimation from each of surfaces 1a and 2a.

[0094] Furthermore, the stress reduction step S0 can be understood as suppressing the transport of raw materials between surface 1a and / or 1b and surface 2a while continuing the sublimation of SiC from each of surfaces 1a, 1b, and 2a, based on the difference in crystal structure between surface 1a, surface 1b, and surface 2a, the temperature difference between surface 1a and surface 2a, and at least some of the elements that make up the atmosphere.

[0095] Furthermore, the stress reduction process S0 can be understood as, for example, suppressing raw material transport between each of surfaces 1a and / or 1b and surface 2a while continuing SiC sublimation from each of surface 1a, which is the Si-face or C-face, and surface 2a of the SiC raw material body 2, which is SiC polycrystal.

[0096] Furthermore, the stress reduction process S0 can be understood as, for example, suppressing raw material transport between surface 1a and / or 1b and surface 2a while continuing SiC sublimation from surface 1a, which is the Si-face or C-face, and surface 2a, which is the Si-face or C-face, of SiC raw material body 2, which is SiC single crystal.

[0097] In the description of this specification, "preventing raw material transport" and "not causing raw material transport" refer to reducing the increase or decrease in thickness of the source and destination of transport after heating. Therefore, atoms constituting the source and destination of transport can become atoms constituting the source and destination of transport after heating.

[0098] In the description herein, the "Si plane" refers to a surface that is at an off-angle of several degrees (for example, 0.4 to 8.0 degrees) from the (0001) plane. In the description of this specification, the "C-plane" refers to a surface that is at an off-angle of several degrees (for example, 0.4 to 8.0 degrees) from the (000-1) plane.

[0099] The driving force for the transport of the source material between surface 1a and surface 2a in each of etching step S1 and growth step S2 can be understood as the vapor pressure difference between SiC single crystal body 1 and SiC source material body 2 resulting from the formed temperature gradient.

[0100] Furthermore, it can be understood that the driving force for the transport of the raw material between surface 1 a and surface 2 a in each of etching step S1 and growth step S2 is not only the temperature gradient between the respective surfaces of SiC single crystal body 1 and SiC source body 2, but also the chemical potential difference between SiC single crystal body 1 and SiC source body 2.

[0101] In each of the stress reducing step S0, the etching step S1, and the growth step S2, the raw material is transported by supplying a dopant gas into the semi-closed space by a dopant gas supply means, thereby adjusting the dopant concentration of the SiC single crystal body 1. It can be understood that when no dopant gas is supplied, the SiC single crystal body 1 inherits the dopant concentration in the semi-closed space.

[0102] Furthermore, the transport of raw materials in each of the stress reducing step S0, the etching step S1, and the growth step S2 is performed under a desired vapor pressure environment, including a SiC-Si equilibrium vapor pressure environment and a SiC-C equilibrium vapor pressure environment. In the description of this specification, the term "SiC-Si vapor pressure environment" refers to a vapor pressure environment in which SiC (solid) and Si (liquid) are in phase equilibrium via the gas phase. The SiC-Si equilibrium vapor pressure environment is formed by heat-treating a semi-closed space in which the atomic ratio Si / C exceeds 1. In the description of this specification, the term "SiC-C equilibrium vapor pressure environment" refers to a vapor pressure environment in which SiC (solid phase) and C (solid phase) are in phase equilibrium via the gas phase. The SiC-C equilibrium vapor pressure environment is formed by heat-treating a semi-closed space in which the atomic ratio Si / C is 1 or less.

[0103] As shown in FIG. 8, one embodiment of the present invention can be understood to include a stress reducing step S0, a strained layer removing step S11, a bunching decomposition step S12, an epitaxial growth step S21, and a bunching decomposition step S22 in this order.

[0104] As shown in FIG. 9, one embodiment of the present invention can be understood to include a strained layer removal step S11, a bunching decomposition step S12, a stress reduction step S0, an epitaxial growth step S21, and a bunching decomposition step S22 in this order.

[0105] As shown in FIG. 10, one embodiment of the present invention can be understood to include a strained layer removal step S11, a bunching decomposition step S12, an epitaxial growth step S21, a bunching decomposition step S22, and a stress reduction step S0 in this order.

[0106] An embodiment of the present invention may include a strained layer removal step S11, a stress reduction step S0, and a bunching decomposition step S12 in this order. Moreover, one embodiment of the present invention may include an epitaxial growth step S21, a stress reduction step S0, and a bunching decomposition step S22 in this order.

[0107] The order of the steps in one embodiment of the present invention may be determined in any order as appropriate for producing and realizing a SiC single crystal mass 1 having the desired quality.

[0108] As shown in FIG. 11, the SiC single crystal manufacturing apparatus (hereinafter simply referred to as the “manufacturing apparatus”) has a main body vessel 141, a high-melting-point vessel 142, and a heating furnace 143.

[0109] Main container 141 is made of a material containing polycrystalline SiC, for example, and therefore at least a part of main container 141 can serve as SiC source material 2 or a transport source (SiC source material 2) for transporting the source material.

[0110] The environment inside the heated main body container 141 is preferably, for example, a vapor pressure environment of a mixture of gaseous species containing Si element and gaseous species containing C element. Examples of the gaseous species containing Si element include Si, Si2, Si3, Si2C, SiC2, and SiC. Furthermore, examples of gas phase species containing C element include Si2C, SiC2, SiC, C, and the like.

[0111] The dopant and dopant concentration of the main vessel 141 can be selected in accordance with the dopant and dopant concentration of the growth layer 10 that is desired to be formed.

[0112] Furthermore, any structure can be adopted as long as it generates vapor pressure of a gaseous species containing Si element and a gaseous species containing C element in the internal space during heat treatment of main container 141. Examples include a structure in which SiC polycrystal is exposed on a part of the inner surface, and a structure in which SiC polycrystal is separately installed inside main container 141.

[0113] Furthermore, the main body container 141 may be configured to include a setting tool 141a on which the SiC single crystal body 1 and the SiC source body 2 can be set.

[0114] The installation fixture 141a is preferably thinned. The thinned installation fixture 141a installs the SiC single crystal body 1 and the SiC source body 2 so as to bring the SiC single crystal body 1 and the SiC source body 2 closer to each other and reduce the separation distance d1 between the SiC single crystal body 1 and the SiC source body 2. In this case, the plurality of SiC single crystal bodies 1 and SiC source bodies 2 may be arranged alternately.

[0115] Main body container 141 may be configured without installation fixture 141a. In this case, the plurality of SiC single crystal bodies 1 and SiC source bodies 2 may be configured to be arranged alternately.

[0116] Furthermore, main container 141 is a fitting container that includes upper container 141c and lower container 141b that can fit together. A minute gap is formed at the fitting portion between upper container 141c and lower container 141b, and main container 141 is configured to be able to evacuate (vacuum) through this gap.

[0117] Furthermore, main container 141 has a Si vapor supply source. The Si vapor supply source is used for the purpose of adjusting the atomic ratio Si / C in the semi-closed space inside main container 141 to exceed 1. Examples of the Si vapor supply source include solid Si (Si pellets such as Si chips or Si powder) and Si compounds.

[0118] For example, in the case where the entire main body container 141 is made of SiC polycrystal, as in one embodiment of the present invention, it can be understood that the atomic ratio Si / C within the main body container 141 exceeds 1 by installing a Si vapor supply source. Specifically, when a SiC single crystal body 1 and a SiC source material 2 having a stoichiometric ratio of 1:1, and a Si vapor supply source are placed in a main body container 141 of SiC polycrystal having a stoichiometric ratio of 1:1, it can be understood that the atomic ratio Si / C in the main body container 141 exceeds 1.

[0119] The SiC-Si equilibrium vapor pressure environment according to one embodiment of the present invention is formed by heating a semi-closed space in which the atomic ratio Si / C exceeds 1. Moreover, the SiC--C equilibrium vapor pressure environment according to one embodiment of the present invention is formed by heating a semi-closed space in which the atomic ratio Si / C is 1 or less. The main body container 141 may be configured to accommodate predetermined members as appropriate so as to create a SiC—Si equilibrium vapor pressure environment or a SiC—C equilibrium vapor pressure environment.

[0120] The heating furnace 143 is capable of heating so as to reduce the temperature gradient and to make the temperature uniform from the upper vessel 141c to the lower vessel 141b of the main vessel 141. Furthermore, heating furnace 143 is capable of heating to form a temperature gradient such that the temperature decreases or increases from upper vessel 141c to lower vessel 141b of main vessel 141. With this configuration, the temperature gradient in the thickness direction of SiC single crystal body 1 is controlled.

[0121] As shown in FIG. 11, the heating furnace 143 includes a main heating chamber 143c capable of heating the SiC single crystal body 1, etc. to a temperature of 1000°C or more and 2300°C or less, a preliminary chamber 143a capable of preheating the workpiece to a temperature of 500°C or more, a high-melting-point container 142 capable of accommodating the main container 141, and a moving means 143b (moving table) capable of moving the high-melting-point container 142 from the preliminary chamber 143a to the main heating chamber 143c.

[0122] For example, the main heating chamber 143c is formed in a regular hexagonal shape in a planar cross section, and the high-melting-point container 142 is placed inside the main heating chamber 143c. A heater 143d (mesh heater) is provided inside the main heating chamber 143c. In addition, multilayer heat-reflecting metal plates (not shown) are fixed to the side walls and ceiling of the main heating chamber 143c. The multilayer heat-reflecting metal plates are configured to reflect heat from the heater 143d toward approximately the center of the main heating chamber 143c.

[0123] The heater 143d is installed in the main heating chamber 143c so as to surround the high-melting-point container 142 in which the object to be treated is accommodated. At this time, a multilayer heat-reflecting metal plate is installed on the outside of the heater 143d, so that the temperature can be raised in the range of 1000°C to 2300°C.

[0124] The heater 143d may be, for example, a resistance heating heater or a high-frequency induction heating heater.

[0125] The heater 143d may be configured to be able to control the temperature gradient in the high-melting-point container 142. The heater 143d may be configured to be able to reduce the temperature gradient in the high-melting-point container 142. The heater 143d may be configured to be able to form a temperature gradient in the high-melting-point container 142. For example, the heater 143d may be configured so that more heaters are provided on the upper side (or lower side). The heater 143d may be configured so that its width increases toward the upper side (or lower side). Alternatively, the heater 143d may be configured so that the power supplied to it can increase toward the upper side (or lower side).

[0126] The main heating chamber 143c is connected to a vacuum forming valve 143f for evacuating the inside of the main heating chamber 143c, an inert gas injection valve 143e for introducing an inert gas into the main heating chamber 143c, and a vacuum gauge 143g for measuring the degree of vacuum inside the main heating chamber 143c.

[0127] The vacuum forming valve 143f is connected to a vacuum pump (not shown) that evacuates the inside of the main heating chamber 143c to create a vacuum. By using the vacuum forming valve 143f and the vacuum pump, the degree of vacuum inside the main heating chamber 143c is preferably 10 Pa or less, more preferably 1.0 Pa or less, and even more preferably 10 ‐3 The pressure can be adjusted to below Pa. An example of the vacuum pump is a turbo molecular pump.

[0128] The inert gas injection valve 143e is connected to an inert gas supply source (not shown). The inert gas is introduced into the main heating chamber 143c by the inert gas injection valve 143e and the inert gas supply source. ‐5 ~10 4 The inert gas can be introduced in the range of Pa. Ar or the like can be selected as this inert gas.

[0129] The inert gas injection valve 143e is a dopant gas supply means capable of supplying a dopant gas into the main body container 141. That is, by selecting a dopant gas (for example, N2 or the like) as the inert gas, the dopant concentration in the growth layer 10 can be increased.

[0130] The preliminary chamber 143a is connected to the main heating chamber 143c, and is configured so that the high-melting-point container 142 can be moved by a moving means 143b. In this embodiment, the preliminary chamber 143a is configured so that it can be heated by residual heat from a heater 143d of the main heating chamber 143c. For example, when the main heating chamber 143c is heated to 2000°C, the preliminary chamber 143a is heated to about 1000°C, and degassing of the workpiece (SiC single crystal body 1, main container 141, high-melting-point container 142, etc.) can be performed.

[0131] The moving means 143b is configured to be able to place the high melting point container 142 thereon and move it between the main heating chamber 143c and the preliminary chamber 143a.

[0132] The transfer between the main heating chamber 143c and the preliminary chamber 143a by the transfer means 143b can be completed in as little as one minute, making it possible to realize temperature rise and fall rates of 1.0 to 1000°C / min. This allows for rapid temperature rise and fall, making it possible to observe surface shapes that do not have a history of low-temperature growth during temperature rise and fall. In addition, in FIG. 11, the preliminary chamber 143a is installed below the main heating chamber 143c, but the preliminary chamber 143a is not limited to this and may be installed in any direction.

[0133] The moving means 143b according to this embodiment is a moving stage on which the high-melting-point container 142 is placed. The contact portion between this moving stage and the high-melting-point container 142 serves as a heat transfer path. This allows a temperature gradient to be formed within the high-melting-point container 142 so that the contact portion between the moving stage and the high-melting-point container 142 is the low-temperature side.

[0134] In the heating furnace 143 of this embodiment, the bottom of the high melting point container 142 is in contact with the moving stage, so a temperature gradient is created such that the temperature decreases from the upper container 142b of the high melting point container 142 toward the lower container 142a.

[0135] The direction of the temperature gradient can be set in any direction by changing the position of the contact point between the moving stage and the high-melting-point container 142. For example, if a hanging type moving stage is used and the contact point is provided on the ceiling of the high-melting-point container 142, heat will escape upward. Therefore, the temperature gradient can be set so that the temperature increases from the upper container 142b to the lower container 142a of the high-melting-point container 142. Note that this temperature gradient is preferably reduced or formed along the thickness direction of the SiC single crystal body 1 and the SiC source body 2. Furthermore, as described above, the temperature gradient may be formed or reduced by the configuration of the heater 143d.

[0136] The vapor pressure environment of the gaseous species containing Si element in heating furnace 143 according to this embodiment is formed using high-melting-point container 142 and a Si vapor supply material. For example, any method capable of forming an environment of the vapor pressure of the gaseous species containing Si element around main body container 141 can be adopted in the SiC substrate manufacturing apparatus of the present invention.

[0137] The high-melting-point container 142 is preferably configured to contain a high-melting-point material having a melting point equal to or higher than the melting point of the material that constitutes the main container 141 .

[0138] Examples of the high-melting point container 142 include C, a general-purpose heat-resistant material; W, Re, Os, Ta, Mo, which are high-melting point metals; Ta9C8, HfC, TaC, NbC, ZrC, Ta2C, TiC, WC, MoC, which are carbides; HfN, TaN, BN, Ta2N, ZrN, TiN, which are nitrides; HfB2, TaB2, ZrB2, Nb2, TiB2, which are borides; and polycrystalline SiC.

[0139] 11, like main container 141, high-melting-point container 142 is a fitting container that includes upper container 142b and lower container 142a that can fit together, and is configured to be able to accommodate main container 141. A minute gap 43 is formed at the fitting portion between upper container 142b and lower container 142a, and high-melting-point container 142 is configured to be able to evacuate (vacuum) through this gap 43.

[0140] The high-melting-point vessel 142 contains a Si vapor supply material capable of supplying a vapor pressure of a gaseous species containing elemental Si into the high-melting-point vessel 142 .

[0141] The Si vapor supply material may be any material that generates Si vapor in the high-melting-point container 142 during heat treatment, and examples thereof include solid Si (Si pellets such as Si chips or Si powder) and Si compounds.

[0142] The Si vapor supply material is, for example, a thin film that coats the inner wall of the high-melting-point vessel 142 .

[0143] When the high-melting-point vessel 142 is a metal compound such as TaC, the Si vapor supply material is, for example, a silicide material of metal atoms and Si atoms that constitute the high-melting-point vessel 142 .

[0144] High-melting-point container 142, having a Si vapor supply material inside it, can maintain a vapor pressure environment of the gaseous species containing Si element inside main container 141. This can be understood as being because the vapor pressure of the gaseous species containing Si element inside main container 141 and the vapor pressure of the gaseous species containing Si element outside main container 141 are balanced.

[0145] This specification will explain the effects of the present invention with reference to Reference Examples 1 to 3. 《Reference example 1》 Under the following conditions, the SiC single crystal substrate E10 is housed in a main body container 141, and the main body container 141 is housed in a high-melting-point container 142.

[0146] <SiC single crystal substrate E10> Polymorphism: 4H-SiC Board size: width (10 mm), length (10 mm), thickness (0.3 mm) Off direction and off angle: 4° off in the <11-20> direction Growth plane: (0001) plane MSB: None Distortion layer: None

[0147] Material: SiC polycrystalline Container size: diameter (60 mm), height (4.0 mm) Distance between SiC single crystal substrate E10 and SiC material: 2.0 mm Atomic ratio Si / C in the container: 1 or less

[0148] Material: TaC Container size: diameter (160 mm), height (60 mm) Si vapor supply material (Si compound): TaSi2

[0149] The SiC single crystal substrate E10 placed under the above conditions was heat-treated under the following conditions. Heating temperature: 1700℃ Heating time: 300min Temperature gradient: 1.0℃ / mm Growth rate: 5.0nm / min Vacuum degree of main heating chamber 143c: 10 ‐5 Pa

[0150] FIG. 12 is an explanatory diagram of a method for determining the conversion rate of BPDs into other defects / dislocations (TEDs, etc.) in the growth layer E11.

[0151] 12(a) shows the state of the growth layer E11 grown by the heating process. In this heating process, the BPDs present in the SiC single crystal substrate E10 are converted to TEDs with a certain probability. Therefore, unless 100% conversion is achieved, TEDs and BPDs will be mixed on the surface of the growth layer E11.

[0152] Figure 12(b) shows the state of defects in the growth layer E11 confirmed using the KOH dissolution etching method. This KOH dissolution etching method involves immersing the SiC single crystal substrate E10 in molten salt (such as KOH) heated to approximately 500°C, forming etch pits at dislocations and defects, and identifying the type of dislocation based on the size and shape of the etch pits. This method allows the number of BPDs present on the surface of the growth layer E11 to be evaluated.

[0153] 12(c) shows the removal of the growth layer E11 after KOH dissolution etching. In this method, the growth layer E11 is planarized to the depth of the etch pits by mechanical polishing or CMP, and then removed by thermal etching, exposing the surface of the SiC single crystal substrate E10.

[0154] 12(d) shows the state in which defects in the SiC single crystal substrate E10, from which the growth layer E11 has been removed, are confirmed using a KOH dissolution etching method. By this method, the number of BPDs present on the surface of the SiC single crystal substrate E10 is evaluated.

[0155] By comparing the number of BPDs present on the surface of the growth layer E11 (see FIG. 12(b)) with the number of BPDs present on the surface of the SiC single crystal substrate E10 (see FIG. 12(d)) using the sequence shown in FIG. 12, the BPD conversion rate, which is the conversion of BPDs to other defects and dislocations by heat treatment, can be obtained.

[0156] The density of BPDs present on the surface of the growth layer E11 in Reference Example 1 is approximately 0 / cm 2 The density of BPDs on the surface of the SiC single crystal substrate E10 is 1000 / cm 2 In other words, it can be understood that BPDs are reduced or eliminated by heating a SiC single crystal substrate E10, which does not have MSBs on its surface, in a semi-closed space where the atomic ratio Si / C is 1 or less.

[0157] In Reference Example 1, a SiC-C equilibrium vapor pressure environment is formed within the main container 141 so that the atomic ratio Si / C within the main container 141 is 1 or less, and therefore it can be understood that BPDs can also be reduced or eliminated in the growth process S2.

[0158] 《Reference example 2》 Under the following conditions, the SiC single crystal substrate E10 was housed in a main container 141, and the main container 141 was housed in a high-melting-point container 142.

[0159] <SiC single crystal substrate E10> Polymorphism: 4H-SiC Board size: width (10 mm), length (10 mm), thickness (0.3 mm) Off direction and off angle: 4° off in the <11-20> direction Growth plane: (0001) plane MSB: Yes

[0160] Material: SiC polycrystalline Container size: diameter (60 mm), height (4.0 mm) Distance between SiC single crystal substrate E10 and SiC material: 2.0 mm Si vapor source: Si chips The atomic ratio in the container is Si / C: 1 or more

[0161] By storing Si pieces together with SiC single crystal substrates in main body container 141, the atomic ratio Si / C in the container exceeds 1.

[0162] Material: TaC Container size: diameter 160mm x height 60mm Si vapor supply material (Si compound): TaSi2

[0163] The SiC single crystal substrate E10 placed under the above conditions was heat-treated under the following conditions. Heating temperature: 1800℃ Heating time: 60min Temperature gradient: 1.0℃ / mm Growth rate: 68nm / min Main heating chamber 143c vacuum degree: 10 ‐5 Pa

[0164] Figure 13 shows SEM images of the surface of SiC single crystal substrate E10 before the growth of growth layer E11. Figure 13(a) is an SEM image observed at a magnification of 1000x, and Figure 13(b) is an SEM image observed at a magnification of 100,000x. It can be seen that MSBs are formed on the surface of SiC single crystal substrate E10 before the growth of growth layer E11, and steps with a height of 3.0 nm or more are arranged with an average terrace width of 42 nm. The step height was measured using an AFM.

[0165] Fig. 14 shows SEM images of the surface of the SiC single crystal substrate E10 after the growth of the growth layer E11. Fig. 14(a) is an SEM image observed at a magnification of 1000x, and Fig. 14(b) is an SEM image observed at a magnification of 100,000x. It can be seen that no MSBs were formed on the surface of the growth layer E11 of Reference Example 2, and that steps of 1.0 nm (full unit cell) were regularly arranged with a terrace width of 14 nm. The step height was measured by AFM.

[0166] Therefore, it can be understood that by heating a SiC single crystal substrate E10 having MSBs on its surface in a semi-closed space with an atomic ratio Si / C exceeding 1, a growth layer E11 in which the MSBs are decomposed is formed.

[0167] In Reference Example 2, the Si vapor supply source is installed so that the atomic ratio Si / C in main body vessel 141 exceeds 1, and therefore a SiC-Si equilibrium vapor pressure environment is formed in main body vessel 141. Therefore, it can be understood that MSB on the surface of the SiC single crystal substrate can be decomposed also in growth step S2.

[0168] 《Reference example 3》 15 is a graph showing the relationship between heating temperature and growth rate when grown using a method for manufacturing a SiC single crystal substrate according to the present invention. The horizontal axis of this graph is the reciprocal of temperature, and the vertical axis of this graph is a logarithmic representation of growth rate. Circles indicate the results of placing SiC single crystal substrate E10 in a space (inside main body container 141) where the atomic ratio Si / C exceeds 1 and growing growth layer E11 on SiC single crystal substrate E10. Crosses indicate the results of placing SiC single crystal substrate E10 in a space (inside main body container 141) where the atomic ratio Si / C is 1 or less and growing growth layer E11 on SiC single crystal substrate E10.

[0169] In addition, the graph in Figure 15 shows the results of thermodynamic calculations of SiC substrate growth in a SiC-Si equilibrium vapor pressure environment using a dashed line (Arrhenius plot), and the results of thermodynamic calculations of SiC substrate growth in a SiC-C equilibrium vapor pressure environment using a two-dot chain line (Arrhenius plot).

[0170] In this method, the SiC single crystal substrate E10 is grown using a chemical potential difference and a temperature gradient as the growth driving force under conditions where the vapor pressure environment between the SiC source and the SiC substrate is a SiC-C equilibrium vapor pressure environment or a SiC-C equilibrium vapor pressure environment. This chemical potential difference can be exemplified by the partial pressure difference between the gas phase species generated on the surfaces of the SiC polycrystal and the SiC single crystal.

[0171] Here, when the growth amount is the partial pressure difference between the vapor generated from the SiC raw material (transport source) and the SiC substrate (transport destination), the SiC growth rate can be calculated using the following equation 1.

[0172]

number

[0173] where T is the temperature of the SiC raw material side, m i is the gas phase species (Si x C y ) is the molecular weight of the molecule, and k is the Boltzmann constant. 輸送元i -P 輸送先iis the amount of SiC deposited when the source gas becomes supersaturated, and the source gas is assumed to be SiC, Si2C, or SiC2.

[0174] Therefore, the dashed line shows the results of thermodynamic calculations when growing a SiC single crystal using SiC polycrystal as a raw material in a vapor pressure environment where SiC (solid) and Si (liquid) are in phase equilibrium via the gas phase. Specifically, these results were obtained by thermodynamic calculations using Equation 1 under the following conditions (i) to (iv). (i) A constant volume SiC-Si equilibrium vapor pressure environment (ii) The driving force for growth is the temperature gradient within the main vessel 141 and the vapor pressure difference (chemical potential difference) between the SiC polycrystal and the SiC single crystal. (iii) The source gas is SiC, Si2C, or SiC2 (iv) The adsorption coefficient of the raw material adsorbed onto the steps of the SiC single crystal substrate E10 is 0.001.

[0175] The two-dot chain line represents the results of thermodynamic calculations performed when growing a SiC single crystal using SiC polycrystal as a raw material in a vapor pressure environment where SiC (solid phase) and C (solid phase) are in phase equilibrium via the gas phase. Specifically, these results were obtained by thermodynamic calculations using Equation 1 under the following conditions (i) to (iv). (i) A constant volume SiC-C equilibrium vapor pressure environment (ii) The growth driving force is the temperature gradient in the main vessel 141 and the vapor pressure difference (chemical potential difference) between the SiC polycrystal and the SiC single crystal. (iii) The source gas is SiC, Si2C, or SiC2 (iv) The adsorption coefficient of the raw material adsorbed onto the steps of the SiC single crystal substrate E10 is 0.001. The data for each chemical species used in the thermodynamic calculations were taken from the JANAF thermochemical tables.

[0176] 15, it can be seen that the results (marked with a circle) of placing the SiC single crystal substrate E10 in a space (inside the main container 141) where the atomic ratio Si / C exceeds 1 and growing the growth layer E11 on the SiC single crystal substrate E10 agree with the trend of the results of the thermodynamic calculation of SiC growth in a SiC-Si equilibrium vapor pressure environment. Also, it can be seen that the results (marked with an x) of placing the SiC single crystal substrate E10 in a space (inside the main container 141) where the atomic ratio Si / C is 1 or less and growing the growth layer E11 on the SiC single crystal substrate E10 agree with the trend of the thermodynamic calculation of SiC growth in a SiC-C equilibrium vapor pressure environment.

[0177] It can be understood that in a SiC-Si equilibrium vapor pressure environment, a growth rate of 1.0 μm / min or more is achieved at a heating temperature of 1960°C. It can also be understood that a growth rate of 2.0 μm / min or more is achieved at a heating temperature of 2000°C or higher. On the other hand, in a SiC-C equilibrium vapor pressure environment, it can be understood that a growth rate of 1.0 μm / min or more is achieved at a heating temperature of 2000°C. It can also be understood that a growth rate of 2.0 μm / min or more is achieved at a heating temperature of 2030°C or higher.

[0178] The amount of warpage 0d of a SiC single crystal wafer produced according to one embodiment of the present invention is preferably <30 μm, more preferably <20 μm, even more preferably <10 μm, and even more preferably <1.0 μm.

[0179] The diameter of the SiC single crystal wafer produced according to one embodiment of the present invention is preferably 6 inches or more, more preferably 8 inches or more, and even more preferably 12 inches or more.

[0180] The BPD density of the growth layer 10 on the surface of a SiC single crystal wafer produced according to one embodiment of the present invention is preferably <1000 / cm 2 and more preferably <500 / cm 2 and more preferably <100 / cm 2 is.

[0181] The growth layer 10 of a SiC single crystal wafer manufactured according to one embodiment of the present invention has a surface roughness of >1.0×10 17 / cm 3 refers to a grown layer having a doping concentration of

[0182] The BPD density of the base substrate 11 directly below the growth layer 10 on the surface of the SiC single crystal wafer manufactured according to one embodiment of the present invention is, for example, 5000 / cm 2 It can be understood that this is the case. [Explanation of symbols]

[0183] 0d: Amount of warpage 1: SiC single crystal 1a: surface 1b: Surface 2:SiC raw material 2a: surface 10: Growth layer 11: Base substrate 43:Gap 101a: Step 101b: Terrace 102a: Step 102b: Terrace 103a: Step 103b: Terrace 141: Main container 141a: Installation tool 141b: Lower container 141c: Upper container 142: High-melting-point container 142a: Lower container 142b: Upper container 143:Heating furnace 143a: Spare room 143b: Means of transportation 143c: Main heating chamber 143d: Heater 143e: Inert gas injection valve 143f: Vacuum forming valve 143g: Vacuum gauge 300: Strained layer 301: Crystal dislocation 302 :Damage area E10: SiC single crystal substrate E11: Growth layer W1: Terrace length W2: Terrace length W3: Terrace length d1: Separation distance S0: Stress reduction process SX: Heat treatment process S1: Etching process S11: Strained layer removal process S12: Bunching decomposition process S2: Growth process S21: Epitaxial growth process S22: Bunching decomposition process

Claims

1. 1. A method for producing a SiC single crystal, comprising: a stress reduction step of heating a SiC single crystal body at 1800°C or higher in an atmosphere containing Si element and C element to reduce internal stress of the SiC single crystal body, the SiC single crystal body has a front surface and a back surface opposite to the front surface, The stress reduction step is a method for producing a SiC single crystal, in which the SiC single crystal body is housed in a main body container made of SiC material, and the main body container is heated so that the vapor pressure between the main body container and the front and back surfaces of the SiC single crystal body is uniform, thereby circulating Si and C elements between the front and back surfaces of the SiC single crystal body and an atmosphere containing Si and C elements.

2. 2. The method for producing a SiC single crystal according to claim 1, wherein the stress reduction step heats the SiC single crystal body so as to prevent the thickness and diameter of the SiC single crystal body from changing.

3. 3. The method for producing a SiC single crystal according to claim 1, wherein the stress reduction step comprises heating the SiC single crystal body in a quasi-closed space.

4. 4. The method for producing a SiC single crystal according to claim 1, wherein the stress reducing step comprises heating the SiC single crystal body in an atmosphere containing an inert gas.

5. 5. The method for producing a SiC single crystal according to claim 1, wherein the stress reducing step comprises heating the SiC single crystal body to homogenize the temperature of the SiC single crystal body.

6. The method for producing a SiC single crystal according to any one of claims 1 to 5, further comprising a heat treatment step of heating the SiC single crystal body and the SiC source body at 1400°C or higher in an atmosphere containing Si element and C element, the heat treatment step including an etching step and / or a growth step.

7. 7. The method for producing a SiC single crystal according to claim 6, wherein the heat treatment step comprises heating the SiC single crystal body and the SiC source body so that the SiC single crystal body is on the high temperature side and the SiC source body is on the low temperature side, and etching the SiC single crystal body.

8. 8. The method for producing a SiC single crystal according to claim 6, wherein the heat treatment step heats the SiC single crystal body and the SiC source body so that the SiC single crystal body is on the low temperature side and the SiC source body is on the high temperature side, thereby growing the SiC single crystal body.

9. 9. The method for producing a SiC single crystal according to claim 6, wherein the heat treatment step includes a step of heating the SiC single crystal body and the SiC source body in a quasi-closed space in which an atomic ratio Si / C is 1 or less.

10. 10. The method for producing a SiC single crystal according to claim 6, wherein the heat treatment step includes a step of heating the SiC single crystal body and the SiC source body in a quasi-closed space having an atomic ratio Si / C exceeding 1.

11. 11. The method for producing a SiC single crystal according to claim 6, wherein the heat treatment step includes a strained layer removal step of etching a strained layer on the SiC single crystal body.

12. 12. The method for producing a SiC single crystal according to claim 6, wherein the heat treatment step includes a bunching decomposition step of decomposing macrostep bunching on the SiC single crystal body and flattening the surface of the SiC single crystal body.

13. The heat treatment step is carried out so that the BPD density is 100 / cm ２ The method for producing a SiC single crystal according to any one of claims 6 to 12, further comprising an epitaxial growth step of forming a growth layer having a thickness of less than 1000 nm.

14. The method for producing a SiC single crystal according to any one of claims 6 to 13, characterized in that the stress reducing step and the heat treatment step are included in this order.

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