Silicon carbide single crystal production method and silicon carbide single crystal production device

Abstract

In a method for producing a SiC single crystal by a gas supply method in which a SiC single crystal (3) is grown on a seed crystal (2) using a raw material gas (20) for supplying SiC, the seed crystal (2) is disposed on a susceptor (13), and then the raw material gas (20) is introduced into a heating container (12) through a first gas introduction port (7) disposed below the seed crystal (2). Then, the heating container (12) is heated to 2000 DEG C or higher, the starting material gas (20) is thermally decomposed and supplied to the seed crystal (2), and the SiC single crystal (3) is grown. Furthermore, the heating container (12) is heated to 2000 DEG C or more, and an etching gas (23) is blown onto the growth surface of the SiC single crystal (3) from a second gas introduction port (8) having a gas discharge port (8a) protruding further toward the susceptor (13) than the first gas introduction port (7), thereby performing local etching for reducing the height difference of the growth surface. As a result, the shape of the growth surface of the SiC single crystal can be made good.

Description

Technical Field

[0001] This disclosure relates to a method and apparatus for manufacturing silicon carbide (hereinafter referred to as SiC) single crystals. Background Technology

[0002] Previously, a gas growth method was known in which a SiC raw material gas was supplied to the growth surface of a seed crystal composed of SiC single crystals, causing the SiC single crystal to grow on the seed crystal. In the gas growth method, in addition to the SiC raw material gas, dopant gases such as N2 (nitrogen) used as dopants to adjust the resistivity of the crystal were introduced to manufacture SiC single crystals.

[0003] In the fabrication of SiC single crystals, if the in-plane temperature and gas distribution at the growth surface cannot be properly adjusted, the growth surface of the SiC single crystal will become concave or convex, and the height difference of the growth surface will increase. Therefore, the internal stress of the SiC single crystal increases, which becomes a cause of crystal fracture.

[0004] As a technology to solve this problem, Patent Document 1 proposes a method that includes a narrowed section in the reaction vessel to control the gas flow by concentrating the SiC raw material gas into the center of the SiC single crystal growth surface. Additionally, it proposes a method that optimizes the structure of the components surrounding the SiC single crystal, surrounds the growth surface with a heat-insulating material, and controls the shape of the SiC single crystal by adjusting the temperature distribution of the growth surface.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-132088 Summary of the Invention

[0008] However, even if the deviation in the growth distribution of SiC single crystals is small, the height difference on the growth surface will accumulate and increase over time if the SiC single crystals are grown for a long period of time. Moreover, this problem is difficult to solve in methods that control the flow of gas blown onto the growth surface of SiC single crystals or methods that adjust the temperature distribution on the growth surface by optimizing the structure of the components around the SiC single crystal, thus hindering the scaling up of SiC single crystals.

[0009] The purpose of this disclosure is to provide a method and apparatus for manufacturing SiC single crystals that enable the growth surface of SiC single crystals to have a good shape.

[0010] The first aspect of this disclosure is a method for manufacturing SiC single crystals, which is a SiC single crystal manufacturing method using a gas supply method, wherein the gas supply method supplies SiC raw material gas to grow SiC single crystals on seed crystals.

[0011] The SiC single crystal manufacturing method includes the following steps:

[0012] The seed crystal is disposed on a base, which is disposed within a hollow heating container that constitutes the growth space of the SiC single crystal;

[0013] The raw material gas is introduced into the heating container through a first gas inlet located below the seed crystal;

[0014] The heating container is heated to above 2000°C, the raw material gas is heated and decomposed, and supplied to the seed crystal, thereby causing the SiC single crystal to grow; and

[0015] The device includes a second gas inlet having a gas outlet that protrudes further toward the base than the first gas inlet, and performs at least one of the following steps: heating the heating container to above 2000°C and introducing a carrier gas that also functions as an etching gas from the first gas inlet; and blowing etching gas from the second gas inlet onto the growth surface of the silicon carbide single crystal to perform local etching that reduces the height difference of the growth surface.

[0016] By blowing etching gas onto the growth surface of the SiC single crystal, the growth surface can be locally etched. This allows for control over the amount of protrusion on the SiC single crystal growth surface, reducing the protrusion and preferably controlling the growth surface to be flat. Therefore, a good shape for the SiC single crystal growth surface can be achieved.

[0017] The second aspect of this disclosure is a SiC single crystal manufacturing apparatus using a gas supply method, wherein the gas supply method supplies SiC raw material gas to grow SiC single crystals on seed crystals.

[0018] The SiC single crystal manufacturing apparatus has the following features:

[0019] A first gas inlet supplies the raw material gas to the seed crystal from below;

[0020] A hollow heating container heats and decomposes the supplied gas and forms the growth space for the SiC single crystal.

[0021] Thermal insulation material is disposed around the heating container;

[0022] A base, disposed within the heating container, is used to hold the seed crystals;

[0023] A vacuum container that houses the heating container, the insulation material, and the base;

[0024] A heating device that heats the heating container;

[0025] A gas outlet that discharges exhaust gas, containing unreacted gas from the growth space to the outside of the vacuum container, including the supply gas supplied to the seed crystal; and

[0026] The second gas inlet has a gas outlet that protrudes further toward the base than the first gas inlet, and blows etching gas onto the growth surface of the SiC single crystal.

[0027] Thus, the presence of a second gas inlet specifically for introducing etching gas allows for localized etching of the SiC single crystal growth surface. This enables control over the amount of protrusion on the SiC single crystal growth surface, reducing the protrusion and preferably controlling the growth surface to be flat. Therefore, a favorable shape for the SiC single crystal growth surface can be achieved. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view of the SiC single crystal manufacturing apparatus according to the first embodiment.

[0029] Figure 2A This is a diagram showing the appearance of the growth surface of a SiC single crystal before the introduction of etching gas.

[0030] Figure 2B This is a diagram showing the appearance of the grown surface of a SiC single crystal after etch gas has been introduced and one hour has passed.

[0031] Figure 3 This is a graph showing the relationship between H2 flow rate and etching time and the amount of etching at the center of the growth surface of the SiC single crystal.

[0032] Figure 4 This is a cross-sectional view of the SiC single crystal manufacturing apparatus according to the second embodiment.

[0033] Figure 5 This is a diagram illustrating the change in the position of the gas outlet. Detailed Implementation

[0034] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0035] In the following embodiments, the same or equivalent parts are described with the same reference numerals.

[0036] (First Implementation)

[0037] The SiC single crystal manufacturing apparatus of this embodiment is used to manufacture SiC single crystal ingots by growing SiC single crystals to a long dimension using a gas supply method. This SiC single crystal manufacturing apparatus is an apparatus for realizing a method for manufacturing SiC single crystals with good surface shape during growth.

[0038] First, refer to Figure 1 The SiC single crystal manufacturing apparatus 1 of this embodiment will be described. This SiC single crystal manufacturing apparatus 1 uses... Figure 1 The SiC single crystal manufacturing apparatus 1 is configured such that the top and bottom surfaces of the substrate are aligned with the vertical direction, and SiC raw material gas is supplied to the surface of the seed crystal 2 formed from the SiC single crystal substrate, so that the SiC single crystal 3 grows on the surface of the seed crystal 2. Specifically, the SiC single crystal manufacturing apparatus 1 includes a gas supply unit 4, various gas supply sources 5, an etching gas source 6, first and second gas inlets 7 and 8, a gas outlet 9, a vacuum container 10, a heat insulation material 11, a heating container 12, a base 13, a rotary lifting mechanism 14, and a heating device 15.

[0039] The gas supply unit 4 is located below the SiC single crystal manufacturing apparatus 1, and introduces raw material gas 20, carrier gas 21, and dopant gas 22, which contain various gases that serve as SiC raw materials, from various supply gas sources 5 into the SiC single crystal manufacturing apparatus 1. In addition, the gas supply unit 4 also introduces etching gas 23 into the SiC single crystal manufacturing apparatus 1.

[0040] The gas supply unit 4 includes a raw material gas supply unit 4a for supplying raw material gas 20, a carrier gas supply unit 4b for supplying carrier gas 21, a dopant gas supply unit 4c for supplying dopant gas 22, and an etching gas supply unit 4d for supplying etching gas 23. Although not shown in the figures, each of these gas supply units 4a to 4d is composed of components forming the supply path. The raw material gas supply unit 4a introduces raw material gas 20 from the raw material gas source 5a (described later) into the SiC single crystal manufacturing apparatus 1. The carrier gas supply unit 4b introduces carrier gas 21 from the carrier gas source 5b (described later) into the SiC single crystal manufacturing apparatus 1. The dopant gas supply unit 4c introduces dopant gas 22 from the dopant gas source 5c (described later) into the SiC single crystal manufacturing apparatus 1. The etching gas supply unit 4d introduces etching gas 23 from the etching gas source 6 (described later) into the SiC single crystal manufacturing apparatus 1.

[0041] Various gas supply sources 5 supply gases containing SiC raw material gases from below the seed crystal 2 disposed on the base 13 into the SiC single crystal manufacturing apparatus 1. In this embodiment, the various gas supply sources 5 are configured to include a raw material gas source 5a, a carrier gas source 5b, and a dopant gas source 5c. A first gas inlet 7 is provided at the bottom 10a of the vacuum container 10 (described later). Various gases supplied from the various gas supply sources 5 are supplied to the first gas inlet 7 through each gas supply section 4a to 4c, and introduced into the SiC single crystal manufacturing apparatus 1 from the first gas inlet 7. The first gas inlet 7 is, for example, cylindrical, and its central axis is aligned with the center of the seed crystal 2.

[0042] The raw material gas source 5a supplies SiC raw material gas containing Si and C, such as a mixture of silane-based gases like silane and hydrocarbon-based gases like propane, to the raw material gas 20. The carrier gas source 5b supplies inert gases such as Ar or He, or carrier gases such as H2 that also function as etching gases, to the carrier gas 21.

[0043] Dopant gas source 5c supplies dopant gas 22 such as N2. Although not shown, each of these gas sources 5a to 5c is equipped with a heating device for controlling the temperature of its respective supplied gas and a flow control device for controlling the flow rate, and can control the temperature and flow rate of its respective supplied gas according to the growth status of the SiC single crystal 3.

[0044] In addition, N2, which is an n-type dopant, was used as an example of the dopant gas 22, but other n-type dopants can also be used, or p-type dopants such as TMA (trimethylaluminum) can be introduced.

[0045] Etching gas source 6 supplies etching gas 23, such as H2, for etching the growth surface of the SiC single crystal 3. In this embodiment, etching gas source 6 introduces etching gas 23 from below the SiC single crystal 3 into the SiC single crystal manufacturing apparatus 1 and guides it to the outer edge of the SiC single crystal 3. A second gas inlet 8 is disposed at a different position from the first gas inlet 7 in the bottom 10a of the vacuum container 10 (described later). The second gas inlet 8 protrudes upward from the first gas inlet 7, i.e., towards the base 13 side. Therefore, the gas outlet 8a of the second gas inlet 8 is close to the SiC single crystal 3, making it easy to blow etching gas 23 onto the growth surface of the SiC single crystal 3.

[0046] In this embodiment, the second gas inlet 8 is formed as a cylindrical shape extending linearly in the vertical direction, through which the etching gas 23 is blown out from below the SiC single crystal 3. The central axis of the second gas inlet 8 is offset relative to the central axis of the first gas inlet 7, and the second gas inlet 8 is disposed on the outer periphery of the first gas inlet 7. Therefore, the structure is such that the airflow of various gases supplied from the first gas inlet 7 is not easily obstructed by the second gas inlet 8. The second gas inlet 8 is disposed at a position corresponding to the outer edge of the base 13, that is, at least a portion of it overlaps with the outer edge of the base 13 when viewed from above, enabling the etching gas to be locally blown onto the outer edge of the growth surface of the SiC single crystal 3.

[0047] Gas outlet 9 discharges unreacted gas, carrier gas 21, dopant gas 22, etc. from the raw material gas 20 supplied to seed crystal 2 as waste gas to the outside of SiC single crystal manufacturing device 1.

[0048] The vacuum container 10 is made of quartz glass or the like and has a cylindrical shape with a hollow portion. In this embodiment, it is cylindrical, enabling the introduction and extraction of the raw material gas 20, carrier gas 21, and dopant gas 22. Furthermore, the vacuum container 10 is configured to house the other components of the SiC single crystal manufacturing apparatus 1 and to depressurize by evacuating the internal space. As described above, a first gas inlet 7 and a second gas inlet 8 are provided at the bottom 10a of the vacuum container 10. The raw material gas 20, carrier gas 21, and dopant gas 22 are then introduced into the SiC single crystal manufacturing apparatus 1 through the first gas inlet 7, and the etching gas 23 is introduced through the second gas inlet 8. Additionally, a through-hole 10b is formed in the upper part of the vacuum container 10, specifically above the side wall, and a gas outlet 9 is embedded within this through-hole 10b.

[0049] The heat insulation material 11 is cylindrical with a hollow portion, and in this embodiment, it is arranged coaxially with respect to the vacuum container 10. The heat insulation material 11 is formed into a cylindrical shape with a diameter smaller than that of the vacuum container 10, and by being disposed inside the vacuum container 10, it suppresses heat transfer from the space inside the heat insulation material 11 to the vacuum container 10. The heat insulation material 11 is made of graphite, for example, but it can also be configured with a surface coated with a high-melting-point metal carbide such as TaC (tantalum carbide) or NbC (niobium carbide), making it difficult to be thermally etched. Furthermore, a through-hole 11a is formed in the upper part of the heat insulation material 11, specifically at a position corresponding to the through-hole 10b of the vacuum container 10, and a gas outlet 9 is embedded in this through-hole 11a.

[0050] The heating container 12 is a crucible that forms the growth space of the SiC single crystal 3, and is configured as a cylindrical shape with a hollow portion; in this embodiment, it is cylindrical. The hollow portion of the heating container 12 forms the growth space in which the SiC single crystal 3 grows on the surface of the seed crystal 2. The heating container 12 is made of graphite, for example, but it can also be configured to have its surface coated with a high-melting-point metal carbide such as TaC or NbC, making it difficult to be thermally etched. The heating container 12 is arranged to surround the base 13. Furthermore, unreacted gases and other waste gases in the raw material gas 20 are guided to the gas outlet 9 side through the space between the inner peripheral surface of the heating container 12 and the outer peripheral surfaces of the seed crystal 2 and the base 13. Through the heating container 12, the SiC raw material gas in the raw material gas 20 is decomposed before the raw material gas 20 from the raw material gas supply section 4a is guided to the seed crystal 2. In addition, a through hole 12a is formed at the upper part of the heating container 12, specifically at the position corresponding to the through hole 10b of the vacuum container 10 and the through hole 11a of the heat insulation material 11, and a gas outlet 9 is embedded in the through hole 12a.

[0051] The base 13 is a component used to hold the seed crystal 2. The base 13 has a circular side where the seed crystal 2 is held, for example, in a disk shape. The central axis of the base 13 is coaxially arranged with respect to the central axis of the heating container 12 and the central axis of the axis 14a of the rotating lifting mechanism 14 (described later). The base 13 is made of graphite, for example, but it can also be configured such that its surface is coated with a high-melting-point metal carbide such as TaC or NbC, making it difficult to be thermally etched. The seed crystal 2 is attached to the side of the base 13 on the side of the first gas inlet 7, allowing the SiC single crystal 3 to grow on the surface of the seed crystal 2. Furthermore, the base 13 is connected to the axis 14a on the side opposite to the side where the seed crystal 2 is held, and rotates with the rotation of the axis 14a, allowing it to be lifted upwards onto the paper as the axis 14a is lifted.

[0052] The rotating lifting mechanism 14 rotates and lifts the base 13 via a shaft 14a made of tubing or the like. In this embodiment, the shaft 14a is a straight line extending vertically, with one end connected to the surface of the base 13 opposite to the surface to which the seed crystal 2 is attached, and the other end connected to the main body of the rotating lifting mechanism 14. This shaft 14a may be made of graphite, for example, but it could also be constructed with a surface coated with a high-melting-point metal carbide such as TaC or NbC, making it difficult to thermally etch. With this configuration, the base 13, the seed crystal 2, and the SiC single crystal 3 can be rotated and lifted, allowing the growth surface of the SiC single crystal 3 to achieve the desired temperature distribution, and as the SiC single crystal 3 grows, the temperature of its growth surface can be adjusted to a suitable temperature for growth.

[0053] The heating device 15 is composed of heating coils such as induction heating coils and direct heating coils, and is arranged to surround the vacuum container 10. In this embodiment, the heating device 15 is composed of induction heating coils. Here, the heating device 15 is configured as a single component, but it can also be divided into multiple components. In this case, it is preferable to configure it so that the temperature of the target area can be controlled independently. For example, the heating device 15 can be respectively arranged at a position corresponding to the lower position of the heating container 12 and a position corresponding to the base 13. In this case, the following steps can be performed more optimally and independently: controlling the temperature of the lower part of the heating container 12 by the heating device 15 to heat the SiC raw material gas to decompose it; and controlling the temperature around the base 13, the seed crystal 2, and the SiC single crystal 3 to a temperature suitable for crystal growth.

[0054] Thus, the SiC single crystal manufacturing apparatus 1 is constructed. Next, the manufacturing method of the SiC single crystal 3 using the SiC single crystal manufacturing apparatus 1 of this embodiment will be described.

[0055] First, a seed crystal 2 is attached to one side of the base 13. The seed crystal 2 uses an offset substrate with a predetermined offset angle, such as 4° or 8°, relative to the (000-1)C plane on the side opposite to the base 13, i.e., the growth surface of the SiC single crystal 3. Next, the base 13 and the seed crystal 2 are disposed inside the heating container 12. Then, the heating device 15 is controlled to impart a desired temperature distribution. That is, the SiC raw material gas contained in the raw material gas 20 is heated and decomposed and supplied to the surface of the seed crystal 2, and the SiC raw material gas is recrystallized on the surface of the seed crystal 2, and a temperature distribution with a sublimation rate higher than the recrystallization rate is formed inside the heating container 12. As a result, the temperature of the bottom of the heating container 12 can be set to a high temperature of 2000°C or higher, and the temperature of the surface of the seed crystal 2 can be set to a temperature suitable for the recrystallization of the SiC single crystal 3, which is lower than the temperature of the bottom of the heating container 12. For example, the environment inside the heating container 12 is set to a high temperature of 2000°C or higher, preferably at least a portion of which is 2500°C or higher. For example, the temperature of the bottom of the heating container 12 is set to about 2800±100℃, and the temperature of the surface of the seed crystal is set to about 2500±100℃.

[0056] Furthermore, while bringing the vacuum container 10 to the desired pressure, a raw material gas 20 containing SiC raw material gas is introduced through the raw material gas supply section 4a. Thus, as... Figure 1 As indicated by the arrow, the raw material gas 20 is supplied to the seed crystal 2, and based on this gas supply, the SiC single crystal 3 grows on the surface of the seed crystal 2.

[0057] Furthermore, carrier gas 21 is introduced through carrier gas supply section 4b, and dopant gas 22 is introduced through dopant gas supply section 4c. As a result, carrier gas 21 and dopant gas 22 flow inside the heating container 12, and the N contained in dopant gas 22 is doped into the SiC single crystal 3.

[0058] Then, by rotating the pulling mechanism 14, the base 13, seed crystal 2, and SiC single crystal 3 are rotated via shaft 14a, and pulled accordingly to the growth rate of SiC single crystal 3. As a result, the height of the growth surface of SiC single crystal 3 remains approximately constant, and the temperature distribution of the growth surface temperature can be well controlled.

[0059] Here, as described above, even if the deviation in the growth distribution of SiC single crystal 3 is small, if SiC single crystal 3 is grown for a long time, the height difference on the growth surface will accumulate and increase over time, hindering the scaling up of SiC single crystal 3. Therefore, by introducing etching gas 23 or a carrier gas 21 containing H2 while maintaining a temperature above 2000°C, such as the temperature during crystal growth, the height difference on the growth surface of SiC single crystal 3 can be suppressed. Two methods can be cited as methods for introducing etching gas 23.

[0060] (1) During the growth of SiC single crystal 3, the growth of SiC single crystal 3 is stopped by stopping the supply of various gases such as raw material gas 20 from the first gas inlet 7, and only etching gas 23 is introduced. At this time, the center of SiC single crystal 3 can also be etched simultaneously with or instead of etching gas 23 by using carrier gas 21 containing H2 from the first gas inlet 7.

[0061] (2) During the growth of SiC single crystal 3, while continuously supplying various gases such as raw material gas 20 from the first gas inlet 7 to grow SiC single crystal 3, etching gas 23 is introduced. Either of these methods (1) and (2) can suppress the growing SiC single crystal 3 from becoming excessively convex. Alternatively, (1) and (2) can be combined and implemented together.

[0062] Regarding the introduction of etching gas 23 or carrier gas 21 containing H2 in method (1), it can be carried out at any time during the growth of SiC single crystal 3, or at a regular time. As a regular time, it can be at a certain interval, or at a time determined corresponding to the growth amount of SiC single crystal 3, for example, the larger the growth amount, the shorter the time interval for introducing etching gas 23.

[0063] For example, SiC raw material may adhere to the gas outlet 9, potentially causing blockage. However, the time required to reach blockage can be determined beforehand through experiments. Etching gas 23 or carrier gas 21 containing H2 can be introduced at a time shorter than the time required to reach blockage. This suppresses blockage of the gas outlet 9 caused by SiC raw material adhesion, allowing for further long-size growth of the SiC single crystal 3.

[0064] Furthermore, during the growth of SiC single crystal 3, sometimes three-dimensional nuclei flow into the growth surface, and sometimes polycrystalline formation occurs starting from these three-dimensional nuclei. Therefore, etching gas 23 or carrier gas 21 containing H2 can be introduced at a time interval shorter than the time taken from the start of three-dimensional nuclei flow to polycrystalline formation, so that the three-dimensional nuclei can be removed even if they flow in, before polycrystalline formation occurs.

[0065] Considering both the closure of the gas outlet 9 and the three-dimensional nucleus inflow, the shorter of the two times—the time spent before the gas outlet 9 is closed and the time spent from the start of the three-dimensional nucleus inflow to the point of polycrystalline formation—suffices to be the time before the introduction of etching gas 23 or H2-containing carrier gas 21. Alternatively, if a device capable of monitoring the growth surface of the SiC single crystal 3 is provided, etching gas 23 or H2-containing carrier gas 21 can be introduced at the moment when three-dimensional nucleus inflow is detected.

[0066] On the other hand, regarding the introduction of the etching gas 23 in method (2), the timing of introduction can be set according to the gas supply conditions from the first gas inlet 7 and the temperature distribution of the growth surface of the SiC single crystal 3. At this time, it is preferable that the temperature of the growth surface of the SiC single crystal 3 is higher than before the introduction of the etching gas 23. For example, compared to before the introduction of the etching gas 23, the temperature of the growth surface of the SiC single crystal 3 becomes approximately 50 to 100°C higher when the etching gas 23 is introduced. This provides an etching advantage, preventing the growing SiC single crystal 3 from becoming excessively convex.

[0067] For example, such as Figure 2A As shown, when a SiC single crystal capable of being produced as SiC single crystal 3 with a wafer size of 6 inches is fabricated, the amount of protrusion of the convex shape before the introduction of etching gas 23, i.e., the amount of protrusion of the crystal center (Cc) relative to the crystal periphery (Cp), is 10 mm. In this case, after stopping the growth of SiC single crystal 3, the introduction of etching gas 23 is started, and the amount of protrusion of the convex shape is confirmed after 1 hour from the start of the introduction of etching gas 23. The results are as follows. Figure 2B As shown, the protrusion has been reduced to 5mm. It should be noted that... Figure 2B This is an example of confirming the case where only carrier gas 21 containing H2 is used, so the center of SiC single crystal 3 is etched, but if etching gas 23 is used, the outer periphery of SiC single crystal 3 is locally etched.

[0068] In this way, by introducing etching gas 23 or carrier gas 21 containing H2, the height difference on the growth surface of SiC single crystal 3 can be suppressed. In addition, if the growth is completed, the growth surface of SiC single crystal 3 can be planarized by maintaining the heating container 12 at above 2000°C before cooling SiC single crystal 3, thereby suppressing crystal cracking caused by stress generated during the cooling of SiC single crystal 3.

[0069] Regarding the etching amount and etching time of the SiC single crystal 3, these can be set according to the desired elevation difference of the grown surface. Specifically, it has been confirmed that the etching amount at the center of the SiC single crystal 3 growth surface is proportional to the flow rate of the etching gas 23 or the carrier gas 21 containing H2 and the etching time. For example, through simulation, when H2 is introduced as the etching gas 23, the relationship between the H2 flow rate and the etching rate at the center of the SiC single crystal growth surface is as follows: Figure 3 The results are shown. Additionally, the surface temperature of seed crystal 2 in this calculation is set to 2500°C.

[0070] Regarding the etching rate, it depends on the gas flow rate near the crystal. For example, by controlling the gas flow rate [m / s] near the SiC single crystal 3 to 2 m / s, the etching rate of the SiC crystal can be controlled to 5 mm / h. If it is 1 h, the center of the SiC single crystal 3 can be etched by 5 mm. Therefore, based on the amount of protrusion of the convex shape envisioned at the time of introduction of the etching gas 23 or the carrier gas 21 containing H2, and the amount of etching at the center position of the growth surface of the SiC single crystal 3, the introduction time of the etching gas 23 or the carrier gas 21 containing H2 and the etching time are set in such a way that the amount of protrusion after etching is the desired amount. As a result, the amount of protrusion after etching can be controlled to the desired amount. For example, even if the center position of the growth surface of the SiC single crystal 3 protrudes slightly more than the outer edge, its protrusion can be controlled to be less than 5 mm, and it is preferable to control the growth surface to be a flat surface.

[0071] As explained above, the SiC single crystal 3 manufacturing apparatus according to this embodiment is equipped with a second gas inlet 8 specifically for introducing etching gas 23, enabling localized etching of the growth surface of the SiC single crystal 3. This allows control over the amount of protrusion on the growth surface of the SiC single crystal 3, reducing the protrusion amount, and preferably controlling the growth surface to be flat. Therefore, the shape of the growth surface of the SiC single crystal 3 can be optimized. As a result, the SiC single crystal 3 can be scaled to a larger size.

[0072] (Second Implementation)

[0073] The second embodiment will be described. This embodiment differs from the first embodiment in that the structure of the second gas inlet 8 is modified; otherwise, it is the same as the first embodiment. Therefore, only the parts that differ from the first embodiment will be described.

[0074] like Figure 4As shown, in this embodiment, the second gas inlet 8 is not straight, but is structured as follows: it has a curved portion 8b that bends at a midpoint in the vertical direction, and the gas outlet 8a of the second gas inlet 8 is eccentric relative to the base 8c, which forms the bottom 10a side of the vacuum container 10. In other words, the second gas inlet 8 is formed by connecting the gas outlet 8a, which extends in the vertical direction, and the base 8c using the curved portion 8b that is inclined relative to the vertical direction. A rotating mechanism 30 is connected to the base 8c, which allows the base 8c to rotate. Specifically, the gas outlet 8a, the curved portion 8b, and the base 8c are formed into a circular tube with a circular cross-section. The gas outlet 8a and the base 8c extend in the vertical direction, and the curved portion 8b is inclined relative to the vertical direction. Furthermore, the base 8c is rotated about a line in the vertical direction as its rotation center axis by the rotating mechanism 30, thereby causing the curved portion 8b and the gas outlet 8a to rotate as well. By tilting the curved portion 8b relative to the vertical direction, the gas outlet 8a is eccentric relative to the base 8c, thus... Figure 5 As shown, when the base 8c rotates, the position of the gas outlet 8a changes in a manner that revolves around the base 8c.

[0075] Therefore, by changing the position of the gas outlet 8a, etching gas 23 can be locally blown at the desired location on the growth surface of the SiC single crystal 3. Thus, etching gas 23 can be concentrated on areas that protrude further than others, thereby further planarizing the growth surface of the SiC single crystal 3. Furthermore, even if the gas outlet 8a is located at a position offset from the center of the growth surface of the SiC single crystal 3, because the SiC single crystal 3 is rotated by the rotating lifting mechanism 14, the entire area at the same distance from the center of the growth surface is etched with etching gas 23. The distribution of elevation differences within the growth surface is determined by the distance from the center of the growth surface; therefore, etching gas 23 can be blown uniformly onto the entire area at equal distances, enabling uniform etching.

[0076] (Other implementation methods)

[0077] This disclosure is based on the embodiments described above, but is not limited to these embodiments, and includes various modifications and equivalent variations. In addition, various combinations or methods, further including only one element, or other combinations or methods with one or more but less elements, also fall within the scope or spirit of this disclosure.

[0078] That is, the elements constituting the above embodiments are not necessarily essential, except where they are specifically stated to be necessary or where they are clearly considered necessary in principle. Furthermore, when referring to the number, value, quantity, range, or other numerical values ​​of constitutive elements, this disclosure is not limited to those specific numbers, except where they are specifically stated to be necessary or where they are clearly limited to a specific number in principle. Similarly, when referring to the shape, orientation, positional relationship, etc., of constitutive elements, this disclosure is not limited to those shapes, orientations, positional relationships, etc., except where they are specifically stated to be necessary or where they are limited to a specific shape, orientation, positional relationship in principle.

[0079] For example, in the embodiments described above, the second gas inlet 8 is configured as a circular tube with a circular cross-section, but it may not be circular. Furthermore, there may be only one second gas inlet 8, but there may be two or more. In this case, it is preferable to arrange them at equal intervals in the circumferential direction centered on the first gas inlet 7. However, as in the second embodiment, when the gas outlets 8a, which are designated as the second gas inlets 8, can be moved to the center of the growth surface of the SiC single crystal 3, the gas outlets 8a may come into contact with each other. Therefore, it is preferable to control the rotation mechanism 30 in a non-contact manner. Alternatively, the eccentricity of the gas outlets 8a relative to the base 8c can be adjusted so that the gas outlets 8a do not come into contact with each other.

[0080] In addition, in the first embodiment described above, the raw material gas 20, carrier gas 21, and dopant gas 22 are introduced through the first gas inlet 7, but they can also be introduced through different inlets. Furthermore, the introduction of carrier gas 21 is arbitrary, and only raw material gas 20 and dopant gas 22 may be introduced.

[0081] Furthermore, in the first embodiment described above, the SiC single crystal manufacturing apparatus 1 is exemplified by an upward flow method in which the raw material gas 20 is supplied to the growth surface of the SiC single crystal 3 and then discharged upwards through the outer peripheral surface of the SiC single crystal 3 and beside the base 13. However, it is not limited to this; it could also be a reflux method where the raw material gas 20 is supplied to the growth surface of the SiC single crystal 3 and then returns in the same direction as the supply direction. Alternatively, it could be a side flow method where the raw material gas 20 is supplied to the growth surface of the SiC single crystal 3 and then discharged towards the outer periphery of the heating container 12.

Claims

1. A method for manufacturing silicon carbide single crystals, which is a silicon carbide single crystal manufacturing method using a gas supply method, wherein the gas supply method supplies a raw material gas for silicon carbide to grow silicon carbide single crystals on a seed crystal. The silicon carbide single crystal manufacturing method includes the following steps: The seed crystal is disposed on a base, which is disposed within a hollow heating container that constitutes the growth space of the silicon carbide single crystal. The raw material gas is introduced into the heating container through a first gas inlet located below the seed crystal; The heating container is heated to above 2000°C, the raw material gas is heated and decomposed, and then supplied to the seed crystal, thereby causing the silicon carbide single crystal to grow; and The device includes a second gas inlet having a gas outlet that protrudes further toward the base than the first gas inlet, and performs at least one of the following steps: heating the heating container to above 2000°C and introducing a carrier gas that also functions as an etching gas from the first gas inlet; and blowing etching gas from the second gas inlet onto the growth surface of the silicon carbide single crystal to perform local etching that reduces the height difference of the growth surface.

2. The method for manufacturing silicon carbide single crystals according to claim 1, wherein, During the etching process, H2 is locally blown onto the growth surface as the etching gas.

3. The method for manufacturing silicon carbide single crystals according to claim 1 or 2, wherein, During the etching process, the etching gas is introduced while the introduction of the raw material gas in the process of introducing the raw material gas is stopped.

4. The method for manufacturing silicon carbide single crystals according to claim 1 or 2, wherein, During the etching process, the etching gas is introduced while the introduction of the raw material gas in the process of introducing the raw material gas continues.

5. The method for manufacturing silicon carbide single crystals according to claim 4, wherein, During the etching process, the etching gas is introduced periodically.

6. A silicon carbide single crystal manufacturing apparatus, which is a silicon carbide single crystal manufacturing apparatus utilizing a gas supply method, wherein the gas supply method supplies a raw material gas for silicon carbide to grow silicon carbide single crystals on seed crystals. The silicon carbide single crystal manufacturing apparatus has the following features: A first gas inlet supplies the raw material gas to the seed crystal from below; A hollow heating container is used to heat and decompose the raw material gas and to form the growth space for the silicon carbide single crystal. Thermal insulation material is disposed around the heating container; A base, disposed within the heating container, is used to hold the seed crystals; A vacuum container that houses the heating container, the insulating material, and the base; A heating device that heats the heating container; A gas outlet is provided to discharge exhaust gas, which includes unreacted gas from the growth space to the outside of the vacuum container, containing the raw material gas supplied to the seed crystal. as well as The second gas inlet has a gas outlet that protrudes further toward the base than the first gas inlet, and blows etching gas onto the growth surface of the silicon carbide single crystal.

7. The silicon carbide single crystal manufacturing apparatus according to claim 6, wherein, The base is configured such that one side of the seed crystal is circular. The gas outlet of the second gas inlet is located at a position corresponding to the outer edge of one side of the base, and the etching gas is blown to the outer edge of the growth surface.

8. The silicon carbide single crystal manufacturing apparatus according to claim 6, wherein, The second gas inlet is located at a different location on the bottom of the vacuum container than the first gas inlet, and has: a base extending vertically from the bottom; and a curved portion connecting the base to the gas outlet, wherein the gas outlet is eccentric relative to the base by being tilted relative to the vertical direction. The silicon carbide single crystal manufacturing apparatus also includes a rotation mechanism that changes the position of the gas outlet by rotating the base.

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