Manufacturing method of SiC laminate

Abstract

To enable manufacturing a SiC laminate in which a cubic SiC layer and a hexagonal SiC layer are alternately laminated without a necessity of a strict management of an epitaxial growth condition and a substrate machining profile and a special surface treatment step.SOLUTION: A positive inclined plane and a negative inclined plane that are inclined from a basal plane of a crystal lattice are arranged on a hexagonal SiC surface, and an arrangement of a trail head line, which is a boundary part, is controlled. In addition, a formation of a cubic SiC layer is ensured by providing a trail head line peak protruding in a specific direction. Furthermore, a relative arrangement of multiple trail head line peaks is relatively displaced from an inclination direction and a vertical direction, allowing film thickness control of each SiC layer to be freely performed. Then, a SiC epitaxial growth is performed, allowing to manufacture a SiC laminate in which the cubic SiC layer and a hexagonal SiC layer are alternately laminated.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a SiC laminate that is preferably used as a substrate for semiconductor elements, sensors, integrated circuits, and the like that operate at high temperatures, high power densities, and high frequencies, and in particular to a method for manufacturing a SiC laminate in which a single-crystal hexagonal SiC layer and a single-crystal cubic SiC layer are stacked. [Background technology]

[0002] Rectifiers and switching elements using single-crystal silicon carbide (SiC) as the substrate material have been put to practical use in electric devices such as trains and air conditioners, industrial power supplies, and home appliances. The single-crystal SiC substrates primarily used to manufacture these semiconductor devices have a forbidden band width (E g ) is 4H-SiC. g This results in the breakdown voltage (V b ) and characteristic on-resistance (R on ) and reduces losses during power conversion.

[0003] V in 4H-SiC b The high E g On the other hand, this wide E g For example, in a metal oxide semiconductor field effect transistor (MOSFET) using 4H-SiC as a substrate, the level density (D it ) becomes higher, and the channel resistance (R ch ) increases, preventing the reduction of power loss.

[0004] In addition, E of 4H-SiC g Because the area is so wide, when a metal-oxide-semiconductor structure (MOS structure) is formed, the amount of charge leaking from the 4H-SiC side through the oxide film to the metal side is greater than in a MOS structure on Si, which poses a serious problem of shortening the lifespan of the oxide film.

[0005] On the other hand, cubic SiC (3C-SiC), the only cubic crystal system among the crystalline polymorphs of SiC, has E g shows 2.3 eV, which is about 1 eV narrower than that of 4H-SiC, but this E g Due to the narrowness of the MOS interface, it is about two orders of magnitude lower than that of 4H-SiC. Therefore, using cubic SiC makes it possible to manufacture low-loss, high-speed switching elements.

[0006] In addition, the E of cubic SiC g is approximately 0.9 eV higher than the electron affinity of 4H-SiC, so in a MOS structure, the amount of charge that leaks from the cubic SiC side through the oxide film to the metal side is small, improving the long-term reliability of the oxide film compared to Si.

[0007] Furthermore, the E g When a cubic SiC layer is sandwiched between hexagonal SiC layers with a wide spacing via a matching interface, the high electron affinity of the cubic SiC layer and the spontaneous polarization caused by the hexagonal SiC layer create a two-dimensional region with a high electron concentration (2DEG) and a two-dimensional region with a high hole concentration (2DHG) at the matching interface.In addition, this two-dimensional conduction effect increases the mobility of electrons and holes in the direction parallel to the matching interface, making it possible to achieve low-loss, high-speed transistor operation.

[0008] In a structure in which three or more cubic SiC layers and hexagonal SiC layers are alternately stacked, two or more parallel coherent interfaces are formed. At each coherent interface, the Si-polar and C-polar planes naturally meet. However, if one of the adjacent coherent interfaces has a structure in which the C-polar plane of cubic SiC meets the Si-polar plane of hexagonal SiC (a P-type coherent interface), the other has a structure in which the Si-polar plane of cubic SiC meets the C-polar plane of hexagonal SiC (an N-type coherent interface). In this case, electron conduction occurs at the N-type coherent interface, and hole conduction occurs at the P-type coherent interface, making it possible to fabricate monolithic complementary field-effect transistors using a single SiC stack structure.

[0009] To realize high-performance semiconductor devices that take advantage of the advantages of cubic SiC, Patent Document 1 (Japanese Patent No. 6795805) proposes a method for manufacturing a SiC stack, which includes the steps of: forming a seed surface parallel to the close-packed planes of the crystal lattice (corresponding to the basal planes described herein) on one or more regions of the surface of a hexagonal SiC layer (seed step); providing inclined surfaces inclined at a positive depression angle of 0.5 degrees or more and less than 73 degrees relative to the seed surface on all surfaces adjacent to the seed surface (off step); and generating two-dimensional nuclei of cubic SiC on the seed surface (nucleation step). This method also includes the step of simultaneously epitaxially growing both the two-dimensional nuclei of cubic SiC and the SiC layer exposed on the inclined surfaces in a direction parallel to the close-packed planes of the crystal lattice (horizontal epitaxial step). This method makes all interfaces of the SiC stack coherent heterointerfaces, and allows for flexible placement of semiconductor elements by separating the cubic SiC surface from the hexagonal SiC surface, thereby enabling the production of high-performance semiconductor devices. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 6795805 specification Summary of the Invention [Problem to be solved by the invention]

[0011] The method disclosed in Patent Document 1 is characterized in that a seed surface parallel to the close-packed plane (basal plane) is provided on the surface of hexagonal SiC, and the seed surface abuts against an inclined surface having a positive depression angle with respect to the seed surface, making it possible to stack a single layer of cubic SiC on hexagonal SiC. However, stacking a hexagonal SiC layer on cubic SiC is not easy, and precise control of the conditions for the nucleation process on the cubic SiC surface and the horizontal epitaxial process is required.

[0012] Furthermore, in the method disclosed in Patent Document 1, the extension direction of the ridges of the undulating shape formed on the hexagonal SiC surface must be aligned within 2 degrees from the non-inclined direction, which is perpendicular to the inclined surface. If the error in this orientation exceeds 2 degrees, it is not possible to obtain a cubic SiC layer in the desired location, resulting in a problem of reduced yield during semiconductor device manufacturing. This requires precise shape control in the manufacturing process of the SiC laminate, which has been an obstacle to reducing manufacturing costs.

[0013] Even if the extension direction of the ridges of the undulating shape formed on the hexagonal SiC surface is aligned to within 2 degrees of the non-inclined direction, if the tolerance of the hexagonal SiC surface is large or if the ridges are inclined from the basal plane, hexagonal SiC steps will remain on the seed surface, preventing the nucleation of cubic SiC.

[0014] Alternatively, even if cubic SiC nuclei are formed, they tend to form multiple nuclei, and the resulting cubic SiC nuclei may meet to form a double positioning boundary. (DPB) This generates a problem that reduces the mobility of electrons or holes. Therefore, it is necessary to carry out a surface structure stabilization process after keeping the tolerance of the hexagonal SiC surface to 0.3 degrees or less, and in some cases it is necessary to precisely control the conditions of the horizontal epitaxial process and the nucleation process.

[0015] In view of the above problems, the present invention aims to make it possible to obtain a cubic SiC layer that does not contain DPB in predetermined locations without requiring precise control of the horizontal epitaxial process and nucleation process, a surface structure stabilization process, strict alignment of the extension direction of the ridges of the undulations, or strict management of the hexagonal SiC surface tolerance, and further to make it possible to form a stacked structure of a hexagonal SiC layer on a cubic SiC layer. [Means for solving the problem]

[0016] As a result of extensive research into solving the above problems, the inventors have found that by imposing specific conditions on the shape of the ridges on the inclined planes formed on the hexagonal SiC surface, it is possible to generate cubic SiC mononuclei where necessary and suppress the occurrence of DPBs without the need for strict control of the processed shape on the SiC substrate surface, precise control of the horizontal epitaxial and nucleation processes, or a surface structure stabilization process. In addition, by providing multiple cubic SiC mononuclei generation locations and displacing them in specific directions, Cubic SiC and hexagonal SiC are stacked alternately It was also found that it is possible to manufacture multi-layer SiC laminates.

[0017] The means for solving the problems according to the present invention will be explained below. [1] In a method for manufacturing a SiC laminate in which a single-crystal hexagonal SiC layer and a single-crystal cubic SiC layer are laminated via a coherent interface, the basal plane (P b ) to a positive tilt angle (θ f ) and the positive tilt direction (α f ) inclined plane (P f ) adjacent to the positive inclination surface and facing the positive inclination direction, (α r ) For the base plane (P b ) to a negative tilt angle (θ r ) inclined negative slope (P r ) and forming the positive inclined surface (P f ) and the negative inclined surface (P r The ridge line (J), which is the line where the two lines meet at their top, is the angle formed by the positive inclination direction. j ) is 15 degrees or more and 86 degrees or less, and the ridge line (J) is composed of two or more line segments connected together, and at least one of the bending points of the ridge line, which is the connecting point of the line segments, is in the negative inclination direction (α r ) and the basal plane (P b) and a horizontal epitaxial growth process of epitaxially growing SiC in a direction parallel to the substrate. [2] The method for manufacturing the SiC laminate of [1], wherein two or more ridge line vertices (τ) are provided, and each ridge line vertex (τ) is in the positive inclination direction (α f ) and the non-tilted direction (α p ) in such a manner that they are not in series.

[0018] Normally, when a Miller index indicating the plane orientation of a SiC crystal is a negative value, a horizontal line (bar) should be written above the corresponding number. However, since this is not possible, in this specification and claims, the corresponding number is expressed by adding a minus sign "-" before it. [Effects of the Invention]

[0019] First, to explain the effect of the present invention, the terraces (P x ) and its end face, the step (S x ) microscopic structure. In hexagonal SiC, the close-packed planes are parallel to the basal plane of the crystal. Hexagonal SiC single crystals have many polymorphs, and each polymorph has a structure in which the close-packed planes of the Si-C molecules are aligned in the normal direction (α z ) are stacked while maintaining the inherent periodicity. When the surface of the close-packed plane is Si polar, α z is the

[0001] orientation, and if the surface of the close-packed plane is C polar, α z is the [000-1] direction.

[0020] In addition, the normal tilt direction (α f ) on the inclined SiC surface, terraces (P x ) and the step (S x ) are exposed at roughly equal intervals. x ) is the positive tilt direction (α f) and parallel to the base plane. p ) along the positive tilt direction (α f ) is set to the [11-20] orientation, the non-inclined direction (α p ) is the [-1100] direction. Or, the positive tilt direction (α f ) is the [1-100] direction, the non-inclined direction (α p ) is the [-1-120] direction. Also, the positive tilt direction (α f ) in the negative gradient direction (α r ) direction, the terraces located relatively in the normal dip direction (α f ) than the terrace located in the normal direction (α z ) relative to the basal plane. Normal direction (α z ) terraces and steps located relatively higher are called the upstream side, Terraces or steps located relatively lower are called downstream sides, and the phenomenon in which upstream steps grow laterally downstream is called flow in this specification. This flow phenomenon corresponds to the atoms supplied to the crystal surface during epitaxial growth being incorporated into stable step edges by surface diffusion, causing the steps to move step by step.

[0021] As shown in Patent Document 1, by providing a seed surface parallel to the basal plane and an inclined inclined surface on the surface of a hexagonal SiC layer, two-dimensional nuclei of cubic SiC formed on the seed surface can be expanded laterally on the inclined surface, and a cubic SiC layer can be formed on the hexagonal SiC layer. For example, as shown in FIG. 2(a), h ) on the surface of the basal plane (P b ) to the positive tilt direction (α f ) at a constant positive tilt angle (θ f ) inclined positive slope (P f ) and furthermore, the positive tilt direction (α f ) in the opposite direction to the negative tilt angle (θ r ) and the base plane (P b ) and the negative slope (P r ) is provided, the positive tilt direction (α f ) and the non-tilted direction (α p ) is formed, and a ridge line (J) is formed along the basal plane (P b) is grown in a direction parallel to the positive inclined plane (P f ) and negative slope (P r ) is the normal direction (α z ) and the basal plane (P b ) along the positive tilt direction (α f ) to the seed surface (P s ) expands.

[0022] Next, as shown in Figure 2(c), the seed surface (P s The width of the critical width (w) of two-dimensional nucleation is determined by the temperature of the horizontal epitaxial process described later. c ), two-dimensional nuclei (γ) of cubic SiC are generated near the center of the seed surface, and the flow at the edge of the nuclei causes the seed surface (P s ) and the cubic SiC layer expands on the hexagonal SiC layer (L h ) on which a cubic SiC layer (L c Even if many two-dimensional nuclei (γ) of cubic SiC are simultaneously generated by multinucleation, the seed surface (P s ) surface is the basal plane (P b ), the stacking order of the two-dimensional nuclei (γ) of each cubic SiC is the same, and the resulting cubic SiC layer (L c ) does not include DPB.

[0023] However, as shown in Figure 3(a), the positive tilt direction (α f ) relative to the ridge line deflection angle (φ j ) is below 88 degrees, the slope from the ridge line (J) to the non-sloping direction (α p ) also step (S x ) flow occurs, and the seed surface (P s ) is defined as the critical width (w c ) or less. As a result, as shown in Figure 3(b), the two-dimensional nucleation (γ) of cubic SiC is prevented, and a cubic SiC layer cannot be obtained. This phenomenon is shown microscopically in Figure 4, where the ridge line (J) forms a terrace (P x) from upstream to downstream, the upstream step flows continuously downstream. s ) expansion is hindered.

[0024] In contrast, in the method for manufacturing a SiC laminate provided by the present invention, as shown in FIG. 5(a), the line segments constituting the ridge line (J) are in the positive inclination direction (α f ) and a line parallel to it, and the included angle φ is between 15 degrees and 86 degrees. j1 , φ j2 The intersection point of each line segment, the ridge line vertex (τ), is in the negative gradient direction (α r ) orientation.

[0025] The ridge line apex (τ) is in the normal direction (α z ) and as shown in Figure 5(b), the ridge line vertex (τ) is used as the starting point, and the seed surface (P s ) expands and the seed surface (P s ) The diameter is w c The virtual circle (C γ ) can now be drawn. At this point, the seed plane (P s The two-dimensional nuclei (γ) of cubic SiC are generated near the center of the ridge line apex (τ) located at the upstream of the flowing step. s ) expansion is not hindered, and the generation of two-dimensional nuclei (γ) of cubic SiC is maintained. As a result, as shown in Figure 5(d), a cubic SiC layer (L c ) is formed. The critical width (w c ) is determined by the conditions of the horizontal epitaxial process, such as the temperature, source gas concentration, C / Si ratio, and crystal growth rate, regardless of the arrangement of the ridge line (J). These conditions are determined by the seed surface (P s ) on the seed surface (P s ) and consequently the critical width (w c ) is reduced. In other words, once the conditions for the horizontal epitaxial process are determined, the critical width (w c ) is determined, it is possible to geometrically determine the arrangement of ridge lines (J) and ridge line inflection points (τ) to generate two-dimensional nuclei (γ) of cubic SiC at predetermined locations. As a result, the locations where two-dimensional nuclei (γ) are generated are determined, which corresponds to the number of ridge line inflection points (τ), and the cross-sectional structure of the epitaxial layer formed by the horizontal epitaxial process (the number of layers and the thickness of each layer) is also determined.

[0026] Furthermore, in the method for manufacturing a SiC laminate provided by the present invention, the two-dimensional nuclei (γ) of cubic SiC formed on the seed surface are always mononuclear, so DPBs do not occur in the cubic SiC layer that expands from there. In contrast, in the method for manufacturing a SiC laminate provided by Patent Document 1, it is not always possible to obtain mononuclear two-dimensional nuclei of cubic SiC on the seed surface. The reason for this is explained with reference to Figure 6. The two-dimensional nuclei (γ) of cubic SiC have a ridge line (J) that expands parallel to the basal plane and has a critical width (w) for two-dimensional nucleation. c ) is generated when the seed plane (P s ) with a diameter of (w c ) is an imaginary inscribed circle (C γ ) can be drawn, then its inscribed circle (C γ This means that a two-dimensional nucleus (γ) of cubic SiC is generated at the center of the crystal.

[0027] In the method for manufacturing a SiC laminated body provided by Patent Document 1, as shown in FIG. 6(a), the seed surface is tilted in the negative direction (α r The ridge line (J) corresponding to the end of the non-inclined direction (α p ) and the positive tilt direction (α f ) end also in the non-inclined direction (α p ) is terminated by a matching interface that is strictly parallel to the seed surface (P s ) is the critical width for two-dimensional nucleation (w c ), the seed surface (P s ) on which there are several inscribed circles As a virtual circle (C γ ) can be drawn simultaneously. Therefore, the two-dimensional nucleation (γ) of cubic SiC results in multi-nucleation, and if the tolerance of the surface is large, the seed surface (P s ) of all two-dimensional nuclei (γ) generated on stacking order does not match, and the Surface structure stabilization process Unless this is done, DPBs will occur within the cubic SiC layer. In other words, in the method for manufacturing a SiC laminate provided by Patent Document 1, the non-inclined direction (α p ) is not limited in width, and the critical width (w c ) based on the seed surface (P s ) shape control is not possible, so the non-inclined direction (α p ) direction along the seed plane (Ps ) is the critical width for two-dimensional nucleation (w c ), and no matter how the epitaxial growth conditions are adjusted, the multi-nuclear growth cannot be eliminated.

[0028] In contrast, in the method for manufacturing a SiC laminate provided by the present invention, the seed surface (P s ) is in the non-inclined direction (α p ) and corresponds to a ridge line (J) that contains one or more ridge line vertices (τ), so as shown in Figure 6(b), the seed plane (P s ) expands to the critical width (w c ), the seed surface (P s ) on multiple (C γ ) cannot be drawn, and the two-dimensional nuclei (γ) of cubic SiC are always generated as a single nucleus, which suppresses the occurrence of DPB in the cubic SiC layer. This is because the ridge line apex (τ) is in the negative gradient direction (α r ) by having a specific shape protruding from the seed surface (P s ) starts from the ridge line apex (τ) and moves in the positive dip direction (α f ) and gradually expands. In other words, the degree of supersaturation increases progressively, which prevents unintended multi-nucleation and ensures mononuclear generation. In particular, the ridge line deflection angle (φ j ) is in the range of 15 degrees to 86 degrees, so the seed surface (P s ) in the non-inclined direction (α p ) while suppressing excessive spreading to the critical width (w c ), it is possible to effectively prevent multiple nuclei from being generated simultaneously. By appropriately controlling the conditions of the horizontal epitaxial process (e.g., wafer temperature, source gas flow rate, pressure, etc.), the seed surface (Ps) expansion rate and critical width (w c ) relationship, it is possible to always induce mononuclear generation. For example, c ) is narrowed down to the seed plane (P s ) can be increased by lowering the wafer temperature or increasing the gas pressure during the horizontal epitaxial process. Alternatively, the tolerance of the horizontal epitaxial process conditions is narrow and the critical width (w c If it is not possible to increase the ridge line deflection angle (φ j ) to reduce the seed surface (P s ) can be prevented from expanding in width, thereby preventing multi-nuclear growth.

[0029] Furthermore, in the method for manufacturing a SiC laminate provided by the present invention, the shape of the expanding cubic SiC layer is determined by the arrangement of the ridge lines, the positive inclination angle (θ f ), ridge line deflection angle (φ j ), and is uniquely determined by the thickness of the SiC film grown in the lateral epitaxial process, so that a cubic SiC layer that matches the required design of a semiconductor device can be obtained with good reproducibility.

[0030] In the present invention, as shown in FIG. 7, it is also possible to provide a plurality of ridge line vertices (τ) on the ridge line (J). In this case, a plurality of cubic SiC layers (L c ) and multiple hexagonal SiC layers (L h ) can be alternately stacked to produce a SiC stacked body.

[0031] In addition, each ridge line vertex (τ) is in the non-inclined direction (α p ) are arranged so that they are not in series with each other, so that multiple seed faces (P s ) is the normal direction (α z ) are displaced relative to the basal plane. Therefore, from the two-dimensional nuclei (γ) of cubic SiC formed on each seed plane, multiple cubic SiC layers (L c ) do not associate on the same basal plane, which can reliably suppress the occurrence of DPB.

[0032] As described above, the method for manufacturing a SiC laminate provided by the present invention ensures the formation of a cubic SiC layer contained in the SiC laminate, and since DPBs do not occur in the formed cubic SiC layer, SiC laminates suitable for high-performance semiconductor elements can be manufactured with high reproducibility.

[0033] Furthermore, the present invention makes it possible to manufacture SiC stacks with any multilayer structure by arranging multiple ridge line vertices (τ), and by utilizing the 2DEG and 2DHG that occur at the interfaces, or by utilizing the quantum well structure formed by a cubic SiC layer sandwiched between hexagonal SiC layers on the top and bottom, it is possible to obtain even more multifunctional semiconductor elements. [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 is a perspective view illustrating the microscopic structure of terraces and steps formed by the close-packed planes of Si—C molecules. [Figure 2] 2(a) to 2(d) are cross-sectional views and surface views for explaining the steps of a conventional method for manufacturing an SiC laminate. [Figure 3]3(a) and 3(b) are a surface view and a cross-sectional view that explain why a cubic SiC layer is not formed in a conventional method for manufacturing an SiC laminate. [Figure 4] FIG. 4 is a perspective view of a microstructure that explains why a cubic SiC layer is not formed in a conventional method for manufacturing an SiC laminate. [Figure 5] 5(a) to 5(d) are surface views and cross-sectional views showing the step of forming a cubic SiC layer on a hexagonal SiC layer in the method for producing an SiC laminate provided by the present invention. [Figure 6] 6(a) and 6(b) are plan views of microstructures showing the difference in the two-dimensional nucleation process of cubic SiC between the conventional method for manufacturing an SiC laminate and the method for manufacturing an SiC laminate of the present invention. [Figure 7] 7(a) to 7(d) are plan views and cross-sectional views illustrating the process of forming a laminate structure in which cubic SiC layers and hexagonal SiC layers are alternately stacked in the method for producing an SiC laminate provided by the present invention. [Figure 8] 8(a) to 8(d) are plan views showing the manufacturing process of the SiC stack according to the second embodiment of the present invention. [Figure 9] FIG. 9 is a cross-sectional view showing the stack structure of the SiC stack formed in the second embodiment of the present invention. [Figure 10] FIG. 10 is a plan view showing the arrangement of positive inclined surfaces and ridge lines in the third embodiment of the present invention. [Figure 11] FIG. 11 is a cross-sectional view showing the stack structure of an SiC stack formed in the third embodiment of the present invention. [Figure 12] FIG. 12 is a cross-sectional view showing a manufacturing process of a negative inclined surface and a ridge line in an embodiment of the present invention. [Figure 13] FIG. 13 is a plan view showing the element shape of a ridge line in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, several embodiments of the method for manufacturing a SiC stack disclosed in this specification will be described.

[0036] [Embodiment 1] When manufacturing SiC laminates, single-crystal hexagonal SiC wafers can be used as substrates. 4H-SiC and 6H-SiC wafers are commercially available as single-crystal SiC wafers, but the E of 3.2 eV is suitable for manufacturing high-voltage power semiconductor devices. g It is desirable to use a 4H—SiC wafer having this property, since it allows the manufacture of high-voltage power semiconductor devices.

[0037] Furthermore, the basal plane (P b ) is used, the surface of the 4H-SiC wafer is tilted at a certain angle from the (0001) plane. (P f ) It can be used as a positive slope (P s ) manufacturing process can be omitted. In this case, the polarity of the substrate surface can be selected from either the Si face or the C face depending on the application, but it is preferable to use the Si face, which is most suitable for manufacturing power semiconductors. However, if one is deliberately trying to obtain a 2DEG at the interface between the cubic SiC layer and the hexagonal SiC layer, it is also possible to use the C face.

[0038] The tilt angle of the surface relative to the basal plane of the 4H-SiC wafer is a positive tilt angle (θ f ), and the effect of the present invention can be obtained if this value is in the range of 0.5 degrees or more and less than 54 degrees. f The lower the tilt angle (θ), the greater the surface area of ​​cubic SiC formed in the horizontal epitaxial process described later. f ) is below 0.5 degrees, the positive slope (P f )The step spacing on the surface becomes 50 μm or more, and two-dimensional nucleation of cubic SiC occurs even on terraces with a positive inclination plane, making it difficult to obtain a coherent interface between cubic SiC and 4H—SiC. Furthermore, in order to keep the film thickness error of cubic SiC obtained by the horizontal epitaxial process within 5%, it is more desirable to set the angle of inclination to 1 degree or more and less than 30 degrees. Therefore, in this embodiment, the positive inclination angle (θ) is set to 4 degrees, which is widely used in commercially available 4H—SiC wafers. f )

[0039] Positive tilt direction (α f The effect of the present invention can be obtained by selecting either the [1-100] orientation or the [11-20] orientation for the negative tilt direction (α r ) is in the [-1-120] direction, and the non-inclined direction (α p ) is the [1-100] direction.

[0040] Next, the positive slope (P s ) is processed into a part of the negative slope (α r ) is formed. r ) to obtain the positive tilt direction (α f ) in the negative gradient direction (α r ) inclined partial surface must be formed. r In forming the partial surface corresponding to the negative inclination surface (P r ), but it is necessary to consider the reproducibility of the processed shape, the dimensional accuracy, and the negative tilt angle (θ r In view of the controllability of the process, it is most desirable to form a groove by a combination of photolithography and dry etching and use the sidewall of the groove.

[0041] Specifically, a photoresist pattern is formed by photolithography to form a desired positive inclination surface (P f) on the substrate, and then, using this photoresist pattern as a mask, a groove is formed on the 4H—SiC substrate by dry etching, and the sidewalls of the groove are turned into negatively inclined surfaces (P r ) for dry etching. A parallel plate plasma etching device or an inductively coupled plasma etching device is used to form grooves by ionizing fluorine-based gases such as SF6 or CF4 and irradiating them onto the SiC substrate. During this process, by adjusting the difference in etching speed between the photoresist and SiC, a negative tilt angle (θ r ) can be adjusted.

[0042] The deeper the groove formed by the dry etching, the more negatively inclined the surface (P r ) area is enlarged, it is possible to increase the thickness of the SiC layer formed in the horizontal epitaxial process described later. However, as the dry etching time increases, not only does the shape error of the ridge line (J) increase, but also the negative slope (P r ) increases the roughness of the surface, so it is desirable to keep the groove depth to 2 μm or less.

[0043] In the above process, the sidewalls of the etched grooves are formed into negatively inclined surfaces (P r ), and the depression angle from the base to the side wall is a negative inclination angle (θ r ) and the positive slope (P f ) and negative slope (P r The line where the two lines meet on the substrate surface corresponds to the ridge line (J). This is the line where the negative inclination direction (α r ) side end. Here, the negative tilt angle (θ r ) should be 54 degrees or more, but in this embodiment, the negative tilt direction (α r ) is used to suppress the expansion of the seed surface to the negative tilt angle (θ r ) is set as close to 90 degrees as possible. For this reason, grooves with sidewalls perpendicular to the surface of the SiC wafer are formed.

[0044] The effect of the present invention is exerted, and DBP In order to obtain cubic SiC that does not containf ) and negative slope (P r The shape of the ridge line (J) formed by the intersection of the tops of the ridges must be controlled as follows: First, if the ridge line (J) is in the positive dip direction (α f ) and a line parallel to the ridge line deflection angle (φ j1 ,φ j2 ) must be greater than or equal to 15 degrees and less than or equal to 86 degrees. The ridge line deflection angle mentioned here is the acute angle when the ridge line intersects with a line parallel to the positive slope direction. If the ridge deflection angle is less than 15 degrees, it becomes difficult to generate two-dimensional nuclei (γ) of cubic SiC. This is because the seed plane (P s ) diameter w c In order to fit the virtual circle, the width of the seed surface along the tilt direction (w s ) is w c This is because the horizontal epitaxial process requires a long time, since it is necessary to divide the value by the sine of the ridge line deflection angle (approximately 0.25). Also, even if two-dimensional nuclei (γ) of cubic SiC are generated, the non-tilted direction (α p The expansion rate of the seed surface in the positive tilt direction (α f ) direction is suppressed by multiplying the tangent of the ridge line deflection angle (approximately 0.27), φ j1 , φ j2 It is more desirable that both of these angles be 30 degrees or greater. On the other hand, if the ridge line deflection angle exceeds 86 degrees, the ridge line (J) may become partially parallel to the non-tilted direction due to the alignment error in the photolithography process described above, increasing the possibility of polynucleation of two-dimensional nuclei (γ) of cubic SiC. For this reason, it is desirable to set the upper limit of the ridge line deflection angle to 82 degrees. Also, the ridge line bending angle (φ τ ) is φ j1 and φ j2 The minimum value is 30 degrees and the maximum value is 172 degrees. τ ) narrows, the distance from the ridge line apex (τ) to the point where the two-dimensional nuclei (γ) of cubic SiC are generated increases. This distance is determined by the number of seed planes (P s ) positive tilt direction (α f ) (i.e., a longer horizontal epitaxial step). Therefore, the ridge line bending angle (φ τ If the gap between the substrate and the substrate is too narrow, a longer horizontal epitaxial step is required to form the desired two-dimensional nuclei (γ) of cubic SiC.

[0045] For example, the ridge line deflection angle (φ j1 ,φ j2 ) is set to 78.7 degrees, and when a SiC epitaxial growth layer with a thickness of 5 μm is formed in the horizontal epitaxial process described later, the positive tilt angle (θ f ) is a 4 degree positive inclination surface (P f )The surface of the cubic SiC epitaxial growth layer expands upward, but its width is f ) and the maximum is 72 μm in the non-tilted direction (α p ) up to 1440 μm.

[0046] In the method for manufacturing a SiC laminate provided by the present invention, a horizontal epitaxial step is performed after forming the ridge line (J), and this horizontal epitaxial step can be performed using vapor phase growth, solution growth, or sublimation. However, in consideration of the reproducibility of epitaxial growth conditions, the controllability of the supersaturation degree on the seed surface, the ease of designing the ridge line arrangement, the controllability of the film thickness of the SiC layer obtained by epitaxial growth, and the controllability of the impurity concentration, it is most desirable to perform the horizontal epitaxial step using vapor phase growth.

[0047] To perform the horizontal epitaxial growth process using vapor phase epitaxy, a commercially available vapor phase epitaxy system is used. The 4H-SiC wafer with the inclined surface is placed on a SiC-coated graphite susceptor, which is then placed in a quartz reactor. The susceptor is then induction-heated from outside the reactor to heat the 4H-SiC wafer to a predetermined temperature. The source gases are then introduced into the reactor, allowing for epitaxial growth of SiC. The source gases can be a combination of silane-based gases such as SiH4 and Si2H6, chlorosilane-based gases such as SiHCl3 and SiCl4, hydrocarbon gases such as CH4, C3H8, and C2H2, and organosilane-based gases such as (CH)3SiH and (CH)SiH3. By maintaining a constant wafer temperature between 1400°C and 1700°C during epitaxial growth, the SiC single crystal grows epitaxially parallel to the basal plane. In particular, when the wafer temperature is set in the range of 1450°C to 1550°C, two-dimensional nuclei of cubic SiC are easily generated on the seed surface, and a high-quality single-crystal SiC layer can be obtained.

[0048] For example, the wafer temperature is set to 1500°C, and the carrier gas H2 is maintained at a flow rate of 5 slm. The SiH4 flow rate is 50 sccm, and the C3H8 flow rate is 13 sccm. The pressure inside the reaction chamber is set to 300 hPa, resulting in a 4-degree positive tilt angle (θ f ) with a positive slope (P f ), the step flows at a rate of 171 μm / hour, resulting in a flow perpendicular to the basal plane (α z ) can be grown at a rate of 12 μm / hour. As a result, the epitaxial film growth rate of the seed surface (P s ) a cubic SiC epitaxial layer with a thickness of 5 μm can be obtained. f ) has a maximum width of 72 μm.

[0049] As described above, according to the method for manufacturing a SiC laminate of this embodiment, single nuclei of cubic SiC are generated on the seed surface whose position is specified by the ridge line apex. The cubic SiC layer undergoes step flow in the positive tilt direction according to the positive tilt angle and the thickness of the SiC epitaxial growth layer formed in the horizontal epitaxial process, and also expands in the non-tilt direction along the ridge line, which is the boundary between the positive tilt surface and the negative tilt surface. This makes it possible to obtain a single cubic SiC layer containing no DBP on the hexagonal SiC epitaxial growth layer with the designed shape and thickness. This enables the reproducible manufacture of low-loss, highly reliable power semiconductor devices such as vertical power MOSFETs.

[0050] [Embodiment 2] By providing multiple ridge line apexes on a continuous ridge line, it is possible to alternately stack hexagonal SiC and cubic SiC. However, if the protrusions are arranged in a non-inclined direction, the seed planes will expand on the same basal plane, originating from different ridge line apexes, making it impossible to obtain the desired multilayer structure. In addition, not all of the two-dimensional nuclei of cubic SiC generated on multiple seed planes will necessarily form the same layered structure. Cubic SiC layers expanding on the same basal plane may merge, causing DPBs, making it difficult to achieve the effects of the present invention.

[0051] On the other hand, in the method for manufacturing a SiC laminate provided by the present invention, different ridge line vertices can be arranged so that they are not in series in a non-inclined direction, so that the cubic SiC layers expanding from each ridge line vertex do not meet on the same basal plane, but are always separated by hexagonal SiC layers, thereby suppressing the occurrence of DPBs within the cubic SiC layers.

[0052] The shape of each ridge line vertex in this embodiment is the same as in embodiment 1, but in order to specify the positional relationship and film thickness of the hexagonal SiC layer and cubic SiC layer in the stacked structure, the relative positions of the multiple ridge line vertices must be accurately determined as described below.

[0053] The method for manufacturing a SiC laminate provided by the present invention can obtain the same number of cubic SiC layers as the number of ridge line vertices formed on the hexagonal SiC. Figure 8 is a plan view showing an embodiment of the process for manufacturing a SiC laminate including a two-layer structure of cubic SiC. As shown in Figure 8(a), a positive inclined plane (P f ) and negative slope (P r ) is set, and two ridge line vertices (τ1, τ2) are set on the ridge line (J). In addition, ridge line valley points (ν1) are also formed as bending points of the ridge line extending in the positive gradient direction from each of the ridge line vertices τ1 and τ2, which orient the vertices in the positive gradient direction.

[0054] Multiple ridge line vertices (τ1, τ2) are in the non-inclined direction (α p ), so τ1 and τ2 are arranged so that the lengths of the perpendicular lines from a straight line (S1) that passes through the ridge line valley point (ν1) and is parallel to the non-tilt direction to the respective ridge line vertices are different. In this embodiment, the length of the perpendicular line from S1 to τ1 is a1, and the length of the perpendicular line from S1 to τ2 is a2, and a2 is a value larger than a1. Therefore, τ2 is located upstream of τ1. When the horizontal epitaxial process is performed here, as shown in Figure 8(b), two seed planes (Ps1, Ps2) are aligned in the positive tilt direction (α f )

[0055] By continuing the horizontal epitaxial process, the P s1 and P s2 Two-dimensional nuclei (γ1, γ2) of cubic SiC are formed on the P s1 The above cubic two-dimensional nucleus is γ1,P s2 Let the above two-dimensional kernel be γ2.

[0056] The steps corresponding to the edges of the two-dimensional nuclei (γ1, γ2) of each cubic SiC crystal are in the positive tilt direction (α f ) direction and along the ridge line (J) in the positive and negative non-inclined direction (α p ) and as shown in Figure 8(d), the positive slope (P f ) two layers of cubic SiC are obtained on the surface. Here, the cubic SiC layer originating from τ1 is c1 The cubic SiC layer originating at τ2 is called L c2 As shown in Figure 9, the cross-sectional structure of the resulting SiC laminate is a cubic SiC layer (L c2 ) is a cubic SiC layer (L c1 ) and each cubic SiC layer (L c1 and L c2 ) is a hexagonal SiC layer (L h2 ) is isolated.

[0057] where L c1 and L c2 The relative positional relationship of the positive tilt angle (θ f ) and the displacement of the ridge line apex in the negative direction (a1, a2), and L in Fig. 9 c1 From the bottom of L c2 The distance (d2) to the bottom of the f ) For example, the positive tilt angle (θ f ) is 4 degrees, a2 is 14 μm, and a1 is 10 μm, then d2 is determined as 0.28 μm. c1 The thickness of the layer, d1, is determined as d1=d2×a1 / a2, so d1 is 0.2 μm, and Lc1 and L c2 L, a hexagonal SiC layer sandwiched between h2 Since the thickness of the layer is d2-d1, it can be determined to be 0.08 μm.

[0058] As described above, the present invention enables not only the formation of a cubic SiC layer on a hexagonal SiC layer, but also the formation of a hexagonal SiC layer on a cubic SiC layer, and the spacing between the SiC layers constituting the stack is set at a positive inclination angle (θ f ), and the placement of the ridge line vertex (τ).

[0059] The method of selecting the SiC wafer used in this embodiment, the method of processing the negative inclined surface, and the conditions of the horizontal epitaxial process are the same as those in the first embodiment, and therefore the description thereof will be omitted.

[0060] [Embodiment 3] In this embodiment, as shown in FIG. 10, a plurality of positive inclined surfaces (P f1 ,P f2 ,P f3 ) are provided and their ends are connected (note that negative inclined surfaces are not shown in FIG. 10). As a result, multiple ridge lines (J1, J2, J3, J4) are formed discontinuously. The ridge line J1 has three ridge line apexes (τ 11 ,τ 12 , τ 13 ) are placed on the ridge line J2. 21 ,τ 22 ) are placed on the ridge line J3. 31 ,τ 32 ) is placed. However, if multiple ridge line tops are in the non-inclined direction (α p ) in series. Also, the ridge line deflection angle (φ j ) must be above 30 degrees and below 82 degrees.

[0061] If a horizontal epitaxial process is performed here, P f1 On the ridge line (J1) adjacent to Ridge line apex (τ 11 ,τ 12 , τ 13) from each of P f2 Three cubic SiC layers (L c11 ,L c12 ,L c13 ) expands. P f2 On the ridge line (J2) adjacent to Ridge line apex (τ 21 ,τ 22 )of From each L c13 Two cubic SiC layers (L c21 ,L c22 ) is the positive inclined surface P f3 Expand upwards. f3 On the ridge line (J3) adjacent to Ridge line apex (τ 31 ,τ 32 ) from each of c22 Two cubic SiC layers (L c31 ,L c32 ) is the positive inclined surface P f4 Zoom in above.

[0062] As a result of the horizontal epitaxial process, the cross section at the position corresponding to M1 in FIG. 10 shows the L layer of hexagonal SiC from the bottom layer, as shown in FIG. 11(a). h13 layer, cubic SiC L c13 Layer, hexagonal SiC L h12 layer, cubic SiC L c12 Layer, hexagonal SiC L h11 layer, cubic SiC L c11 In addition, as shown in FIG. 11(b), the cross section at the position corresponding to M2 in FIG. 10 shows that the L layer of hexagonal SiC is located below the laminated structure of the cross section of M1. h22 layer, cubic SiC L c22 Layer, hexagonal SiC L h21 layer, cubic SiC L c21 Furthermore, in the cross section at the position corresponding to M3 in Fig. 10, as shown in Fig. 11(c), a hexagonal SiC L layer is formed under the laminated structure of the cross section of M2. h32 layer, cubic SiC L c32 Layer, hexagonal SiC L h31 layer, cubic SiC L c31 A layered structure is formed, which is the positive inclined surface Pf4 Zoom in above.

[0063] As described above, by causing the structure appearing at the steps of the positive inclined surface on which the multilayer SiC stacked structure is formed to flow onto the downstream positive inclined surface, it is possible to form an even more multilayered SiC stacked structure.

[0064] Here, each positive slope (P f1 , P f2 , P f3 ) is narrowed, the more easily basal plane dislocations (BPDs) contained in the SiC layer epitaxially grown upstream are expelled to the edge of the positive inclined surface of the lower layer, making it possible to obtain a SiC stack with a lower BPD density downstream.

[0065] In addition, the selection method of the SiC wafer used in this embodiment, the negative inclined surface (P r ) processing method, conditions for the horizontal epitaxial process, and the arrangement of each ridge line (J) and the shape of the ridge line apex (τ) are the same as those in the first embodiment, and therefore descriptions thereof will be omitted. [Example]

[0066] (Hexagonal SiC substrate) A commercially available 6-inch diameter single crystal 4H-SiC wafer is used as the substrate. However, the surface is inclined 4 degrees from the (0001) plane (Si surface) to the [11-20] direction. In addition, a first orientation flat parallel to the (1-100) plane at the 6 o'clock direction from the center of the 4H-SiC wafer and a second orientation flat parallel to the (11-20) plane at the 9 o'clock direction are processed. The surface of this wafer is called a positive inclined plane (P f In this case, the [11-20] direction parallel to the first orientation flat is the normal tilt direction (α f ), and the opposite [-1-120] direction is the negative tilt direction (α r ), and parallel to the second orientation flat [-1100] direction Non-tilted direction (α p ) However, the tolerance of each orientation flat and surface is allowed up to 0.5 degrees.

[0067] (Negative slope machining process) Using Fig. 12, we use the negative slope (P r The process of forming the ridge line (J) and the positive inclined surface (P) of the 4H-SiC wafer (Wf) is shown. f A resist pattern is formed to cover the area corresponding to the (0001) plane (Si plane) and the (11-20) direction. The area covered by the resist pattern corresponds to a surface tilted 4 degrees from the (0001) plane (Si plane) to the [11-20] direction. f ) is 4 degrees. In this process, as shown in Figure 12(a), a positive photoresist (Res) is spin-coated on the surface of the 4H-SiC wafer (Wf) to a film thickness of 2 μm. Next, a laser lithography system (DWL2000 GL manufactured by Heidelberg Instruments) is used to create a positive inclined surface (P f ), the photoresist (Res) is exposed and developed except for the area corresponding to the positive inclined surface, thereby forming an opening in the photoresist (Res) except for the area corresponding to the positive inclined surface, as shown in Figure 12(b).

[0068] The opening is then etched using an ICP-RIE device (MUC-21) manufactured by Sumitomo Precision Products Co., Ltd. For etching, CF4 gas at 400 sccm and O2 gas at 100 sccm are introduced, and an ICP output of 1 kW is applied to excite the plasma. A 0.8 μm dry etching is performed in 15 minutes to form a groove. The photoresist (Res) on the 4H-SiC wafer (Wf) is then removed using a mixed acid of hydrogen peroxide and sulfuric acid. The sidewalls of this groove are at an angle of 80 to 83 degrees to the wafer surface, and the positive inclination angle (θ f ) plus 4 degrees, the negative slope (P r ) negative tilt angle (θ r ) and the positive inclined surface (P f ) and negative slope (P r ) functions as a ridge line (J).

[0069] (Shape of the ridge line) The shape of the element patterns constituting the exposed shape is as shown in Figure 13. The element patterns are translated in the non-tilt direction and the positive tilt direction so that the ridge line valley (ν1) at the upper end coincides with the ridge line valley (ν1) at the lower end, forming a ridge line that is continuous from the lower end to the upper end of the 4H-SiC wafer (Wf). However, the width of the positive tilt surface abutting each element pattern is 50 μm or more.

[0070] The positional relationship and ridge line deflection angles of the ridge line apexes (τ1, τ2) constituting the element patterns shown in FIG. 13 are as shown in Table 1. Element patterns No. 1 to No. 3 are in accordance with the manufacturing method of the SiC laminate provided by the present invention, and the ridge lines have ridge line deflection angles (φ j1 , φ j2 , φ j3 , φ j4 ) in the positive tilt direction (α f ) and the two ridge line apexes (τ1, τ2) on the ridge line are in the non-inclined direction (α p ) are arranged so that they are not in series.

[0071] In element pattern No. 4, the ridge line has a ridge line deflection angle of 71 degrees to 76 degrees (φ j1 , φ j2 , φ j3 ,φ j4 ) in the positive tilt direction (α f ) form an included angle with the ridge line. However, the two ridge line crests (τ1, τ2) on the ridge line are in the non-inclined direction (α p ) in series, and therefore does not fall under the method for manufacturing a SiC laminate provided by the present invention.

[0072] In element pattern No. 5, the two ridge line apexes (τ1, τ2) on the ridge line are arranged so that they are not in line in the non-inclined direction, but the ridge line is aligned with a ridge line deflection angle (φ j1 , φ j2 , φ j3 ,φ j4 ) in the positive tilt direction (α f ) and therefore does not fall within the method for producing a SiC laminate provided by the present invention.

[0073] In element pattern No. 6, the two ridge line apexes (τ1, τ2) on the ridge line are arranged so that they are not in line in the non-inclined direction, but the ridge line has a ridge line deflection angle of 89 degrees (φ j1 , φ j2 , φ j3 ,φ j4 ) in the positive tilt direction (α f ) and therefore does not fall within the method for producing a SiC laminate provided by the present invention.

[0074] In element pattern No. 7, a1, a2, a3, and a4 are zero, and no ridge line apex is formed, as in the manufacturing method of the SiC laminate provided by Patent Document 1. In addition, the ridge line deflection angle (φ j1 , φ j2 , φ j3 ,φ j4 ) is 90 degrees and the ridge line (J) is in the non-inclined direction (α p ) is parallel to the SiC stack. Therefore, this does not fall under the method for producing a SiC laminate provided by the present invention.

[0075] In element pattern No. 8, the ridge line deflection angle (φ j1 ) is 84 degrees and the ridge line (J) is in the non-inclined direction (α p ), but a2, a3, and a4 are zero, and no ridge line apex is formed. Therefore, this does not correspond to the method for producing a SiC laminate provided by the present invention.

[0076] [Table 1]

[0077] (Horizontal epitaxial process) After forming the ridge lines consisting of the above eight different element patterns on the same 4H-SiC wafer, epitaxial growth of SiC is carried out as a horizontal epitaxial process. At this time, the wafer temperature is set to 1500°C, and the carrier gas H2 flow rate is maintained at 5 slm. SiH4 flow rate is 50 sccm, and C3H8 flow rate is 13 sccm introduced into the vapor phase growth apparatus, and the pressure inside the reaction chamber is set to 300 hPa to carry out epitaxial growth of SiC. At this time, a positive tilt angle (θ f) positively inclined surface (P f ) The step flows at a rate of 171 μm / hour on the top, and the flow direction is perpendicular to the basal plane (α z ) the epitaxial film grows at a rate of 12 μm / hour. As a result, the epitaxial film grows at a rate of 12 μm / hour on the seed surface (P s ) on the substrate, a 5 μm thick epitaxial layer of 3C-SiC is obtained. f ) has a maximum width of 72 μm.

[0078] (Structural evaluation of SiC laminates) After the lateral epitaxial growth process, the surface and cross-sectional structure of the SiC epitaxial growth layer were observed using a scanning electron microscope (SEM) and a transmission electron microscope (TEM), and the crystal structure distribution of the SiC was observed using electron backscatter diffraction (EBSD). These observations were used to measure the condition of the 3C-SiC surface and DPB density for each element pattern, as well as the cross-sectional structure of the SiC stack. In particular, the cross-sectional structure of the SiC stack was compared with the structure shown in Figure 9 to determine the thickness (d1) of the 3C-SiC layer and the spacing (d2) of the 3C-SiC layer separated by the 4H-SiC layer. These are summarized in Table 2.

[0079] [Table 2]

[0080] As shown in Table 2, when element patterns No. 1 to No. 3 were used, a continuous 3C-SiC layer in the non-inclined direction was found on the surface of the SiC laminate, and it was confirmed that it did not contain DPB. In addition, a multilayer structure of 3C-SiC with a 4H-SiC layer interposed was found, and the spacing (d2) between adjacent 3C-SiC layers was (a2 - a1) × TAN(θ f ) relationship is maintained. In addition, the thickness (d1) of the 3C-SiC layer below the 4H-SiC layer is almost equal to the value derived from d2 × a1 / a2. 。

[0081] Although the presence of continuous 3C-SiC in a non-tilt direction can be confirmed on the surface of the SiC epitaxial growth layer on element pattern No. 4, ―1 EBSD analysis revealed that the specimen contained DBPs with a density of 3C-SiC only in the surface layer, with the underlying layer being entirely 4H-SiC.

[0082] In the SiC epitaxial growth layers on element patterns No. 5 and No. 8, no 3C-SiC layer was found, and the surfaces of the positively inclined planes were entirely covered with a 4H-SiC layer.

[0083] Although the presence of 3C-SiC can be confirmed on the surface of the SiC epitaxial growth layer on element patterns No. 6 and No. 7, EBSD reveals that it is discontinuous in the non-tilt direction and contains a small amount of DBP.

[0084] As shown in the above examples, the method for manufacturing a SiC laminate provided by the present invention ensures the production of cubic SiC by providing a ridge line that forms the boundary between the positively and negatively inclined planes and by providing a ridge line apex that protrudes in the negatively inclined direction. It was also revealed that by not arranging multiple ridge line apexes in series in the non-inclined direction, a multilayer structure in which cubic SiC and hexagonal SiC are alternately stacked can be formed. Furthermore, it was verified that adjusting the relative arrangement of multiple ridge line apexes can eliminate DPB and enable the production of an SiC laminate structure that is optimal for manufacturing various semiconductor devices such as MOSFETs and HEMTs.

[0085] Although the examples of the present invention have been described above, the present invention is not limited to the above examples and embodiments, and can of course be embodied in various forms within the scope of the present invention. For example, the crystal polytype of hexagonal SiC is not limited to 4H-SiC; even if 6H-SiC or 15R-SiC is used, a cubic SiC layer can be reliably generated and its layer structure can be controlled. Furthermore, the polar surface of the substrate surface is not limited to the Si-face; the same effect can be obtained even if the C-face is used.

[0086] Furthermore, the ridge line does not necessarily have to be straight as in this embodiment; similar effects can be obtained as long as the ridge line deflection angle is in the range of 15 degrees or more and 86 degrees or less. The depression angles of the positively and negatively inclined surfaces relative to the ridge line do not need to be constant; the shape of the cubic SiC layer can be controlled as long as they are within the ranges described in this specification. Furthermore, the temperature, pressure, added impurities, and gas flow rate in the horizontal epitaxial process are not limited to those in this embodiment or example; optimal conditions can be adjusted as needed.

[0087] Furthermore, the ridge line apex does not need to be protruding with atomic level sharpness, and can be regarded as a protruding point if it has a curvature of substantially 10 μm or less. [Industrial Applicability]

[0088] The SiC laminate of the present invention can be used as a substrate for power semiconductor elements such as MOSFETs, IGBTs, bipolar transistors, pn diodes, and SBDs, as well as for high-speed CMOS logic circuits, MEMS elements, etc. Furthermore, by taking advantage of the characteristics of a matched heterointerface where different band gaps and electron affinities meet, it can also be used as a substrate for high-frequency devices such as HBTs and HEMTs, and for high-efficiency solar cells. [Explanation of symbols]

[0089] P b basal plane P f Positively inclined plane P r Negative slope P s Seed Faces P x terrace S x Steps θ f Positive tilt angle θ r Negative tilt angle α f Positive tilt direction α r Negative slope direction α p Non-tilt direction α z Normal direction to the base surface J, J1, J2, J3 ridge lines τ, τ1, τ2, τ 11 , τ 12 , τ 13 , τ 21 , τ 22 , τ 31 , τ 32 Ridge line apex Φ j , Φ j1 , Φ j2 , Φ j3 Ridge line deflection angle γ Two-dimensional nuclei of cubic SiC L h , L h1 , L h2 , L h11 , L h12 , L h13 , L h21 , L h22 , L h31 , L h31 Hexagonal SiC layer L c , L c1 , L c2 , L c11 , L c12 , L c13 , L c21 , L c22 , L c31 , L c31 cubic SiC layer d1 cubic SiC layer thickness d2 distance between adjacent cubic SiC layers S1 Reference line parallel to the non-tilt direction a1, a2 The length of the perpendicular line from a line parallel to the non-inclined direction to the ridge line apex a3, a4 The length of the perpendicular line from a line parallel to the non-inclined direction to the ridge line valley point w c Critical width for two-dimensional nucleation w s Seed Face Width θ τ Ridge line bend angle ν, ν1 ridge line valley point C γ Inscribed circle on the seed face Wf 4H-SiC wafer Res positive photoresist

Claims

【Request Item 1】 In a method for manufacturing a SiC laminate in which a single-crystal hexagonal SiC layer and a single-crystal cubic SiC layer are laminated via a coherent interface, a basal plane (P ｂ ) to a positive tilt angle (θ ｆ ) and the positive tilt direction (α ｆ ) positively inclined surface (P ｆ ) adjacent to the positive inclination surface and inclined in a negative inclination direction (α r ) opposite to the positive inclination direction. ｂ ) to a negative tilt angle (θ ｒ ) inclined negative slope (P ｒ ) forming the positive inclined surface (P ｆ ) and the negative inclined surface (P ｒ The ridge line deflection angle (Φ ｊ ) is 15 degrees or more and 86 degrees or less, and the ridge line (J) is composed of two or more line segments connected together, and at least one of the bending points of the ridge line, which is the connecting point of the line segments, is in the negative inclination direction (α ｒ ) and the basal plane (P ｂ 1. A method for manufacturing a SiC stack, comprising: a horizontal epitaxial growth step of epitaxially growing SiC in a direction parallel to the substrate. 【Request Item 2】 2. The method for manufacturing a SiC laminate according to claim 1, wherein two or more ridge line vertices (τ) are provided, and each ridge line vertex (τ) is in the positive inclination direction (α ｆ ) and the non-tilt direction (α ｐ ) in such a manner that the SiC layers are not in series.

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