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 preferably used as a substrate for semiconductor elements, sensors, integrated circuits, etc. that operate at high temperatures, high power densities, and high frequencies, and particularly relates to a method for manufacturing a SiC laminate in which a single-crystalline hexagonal SiC layer and a single-crystalline cubic SiC layer are laminated.

Background Art

[0002] Rectifying elements and switching elements using single-crystalline silicon carbide (SiC) as a substrate material have been put into practical use in electric devices such as trains and air conditioners, industrial power supplies, and home electric appliances. The single-crystalline SiC substrate mainly used for manufacturing these semiconductor elements is 4H-SiC having a bandgap (E g ) of 3.2 eV. Due to this wide E g , both an increase in the breakdown voltage (V b ) of the semiconductor element and a reduction in the on-resistance (R on ) of the characteristics are achieved, and the loss during power conversion is reduced.

[0003] The high V b of 4H-SiC is due to the width of its E g . On the other hand, this wide E g also causes a reduction in the low-loss performance and long-term reliability of the switching element. For example, in a metal-oxide-semiconductor field-effect transistor (MOSFET) using 4H-SiC as a substrate, the density of levels (D it ) at the oxide-semiconductor interface (MOS interface) becomes high, the channel resistance (R ch ) increases, and the reduction of power loss is hindered.

[0004] In addition, since the E g of 4H-SiC is 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 becomes larger than that of the MOS structure on Si, and the problem of shortening the life of the oxide film is also serious.

[0005] On the one hand, among the crystal polymorphs of SiC, cubic SiC (3C-SiC), which is the only cubic crystal system, has an E g showing 2.3 eV, which is about 1 eV narrower than that of 4H-SiC. Fortunately, due to the narrowness of this E g the D it at the MOS interface is about two orders of magnitude lower than that of 4H-SiC. Therefore, using cubic SiC makes it possible to manufacture low-loss and high-speed switching devices.

[0006] Also, since the E g of cubic SiC is about 0.9 eV higher than the electron affinity of 4H-SiC, in the MOS structure, the amount of charge leaking from the cubic SiC side through the oxide film to the metal side is small, and the long-term reliability of the oxide film is improved compared to Si.

[0007] Furthermore, when a cubic SiC layer is sandwiched through a coherent interface with hexagonal SiC having a wider E g than the cubic SiC layer, due to the high electron affinity of the cubic SiC layer and the spontaneous polarization brought about by the hexagonal SiC layer, a two-dimensional region (2DEG) with a high electron concentration and a two-dimensional region (2DHG) with a high hole concentration are generated at the coherent interface, and the mobility of electrons and holes is enhanced in the direction parallel to the coherent interface by the two-dimensional conduction effect, making it possible to realize low-loss and high-speed transistor operation.

[0008] In a structure where cubic SiC layers and hexagonal SiC layers are alternately stacked in three or more layers, two or more coherent interfaces in a parallel relationship are formed. At each coherent interface, the Si-polar surface and the C-polar surface naturally come into contact. However, if one of the adjacent coherent interfaces has a structure (P-type coherent interface) where the C-polar surface of cubic SiC and the Si-polar surface of hexagonal SiC are in contact, the other will have a structure (N-type coherent interface) where the Si-polar surface of cubic SiC and the C-polar surface of hexagonal SiC are in contact. In this case, conduction by electrons appears at the N-type coherent interface and conduction by holes appears at the P-type coherent interface, so it is also possible to manufacture a monolithic complementary metal-oxide-semiconductor field-effect transistor in a single SiC stacked structure.

[0009] In order to realize a high-performance semiconductor device that takes advantage of the benefits of this cubic SiC, Patent Document 1 (Japanese Patent No. 6795805) discloses a method for manufacturing a SiC laminate, which includes a step of forming a seed plane (seed step) parallel to the densest plane of the crystal lattice (corresponding to the basal plane described in this specification) in one or more regions on the surface of the hexagonal SiC layer, a step of providing an inclined plane (off step) inclined at a positive depression angle of 0.5 degrees or more and less than 73 degrees with respect to all surfaces adjacent to the seed plane with the seed plane as a reference, a step of generating two-dimensional nuclei of cubic SiC on the seed plane (nucleation step), and a step of simultaneously epitaxially growing both the two-dimensional nuclei of cubic SiC and the SiC layer exposed on the inclined plane in a direction parallel to the densest plane of the crystal lattice (horizontal epi step). By this method, all interfaces of the SiC laminate are made into coherent hetero-interfaces, and it has become possible to freely arrange semiconductor elements by distinguishing between the cubic SiC surface and the hexagonal SiC surface, thereby obtaining a high-performance semiconductor device.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] In the method provided by Patent Document 1, since a seed plane parallel to the densest plane (basal plane) is provided on the hexagonal SiC surface and the seed plane abuts on an inclined plane having a positive depression angle with respect to the seed plane, it is possible to stack a single layer of cubic SiC on the hexagonal SiC. However, it is not easy to stack a hexagonal SiC layer on the cubic SiC, and precise control of the conditions for the nucleation step and the horizontal epi step on the cubic SiC surface is required.

[0012] Furthermore, in the method provided by Patent Document 1, it is necessary to align the extending direction of the ridge of the undulating shape formed on the hexagonal SiC surface within 2 degrees from the non-inclined direction perpendicular to the inclined surface. When the azimuth error exceeds 2 degrees, a cubic SiC layer cannot be obtained at a predetermined location, and there also arises a problem that the yield in semiconductor device manufacturing decreases. For this reason, precise shape control in the manufacturing process of the SiC laminate is required, which has been an obstacle to cost reduction in manufacturing.

[0013] Even if the extending direction of the ridge of the undulating shape formed on the hexagonal SiC surface is aligned within 2 degrees from the non-inclined direction, when the tolerance of the hexagonal SiC surface is large or when the ridge is inclined from the basal plane, steps of hexagonal SiC remain on the seed surface, and a problem also arises that the nucleation of cubic SiC is hindered.

[0014] Alternatively, even if nuclei of cubic SiC are generated, they tend to generate multiple nuclei, and the occurrence of Double Positioning Boundary (BPD) due to the association of the multiply generated cubic SiC reduces the mobility of electrons or holes. Therefore, it is necessary to set the tolerance of the hexagonal SiC surface to 0.3 degrees or less and perform a surface structure stabilization process, and further, it may be necessary to precisely control the conditions of the horizontal epitaxial process and the nucleation process.

[0015] In view of the above problems, an object of the present invention is to enable obtaining a cubic SiC layer free of DPB at a predetermined location without requiring precise control of the horizontal epitaxial process, the nucleation process, the surface structure stabilization process, strict alignment of the extending direction of the undulating ridge, and strict management of the tolerance of the hexagonal SiC surface, and further to enable a laminated structure of a hexagonal SiC layer on the cubic SiC layer.

Means for Solving the Problems

[0016] As a result of intensive studies to solve the above problems, the inventors have found that by giving specific conditions to the shape of the ridge on the inclined plane formed on the surface of hexagonal SiC, precise machining shape control on the surface of the SiC substrate, precise control of the horizontal epi process and the nucleation process, and further, without the need for a surface structure stabilization process, it is possible to generate single nuclei of cubic SiC at the required locations and suppress the generation of DPB. In addition, it has been found that by having a plurality of single-nucleation locations of cubic SiC and displacing them in a specific direction, it is possible to manufacture a multilayer SiC laminate in which hexagonal SiC is laminated on cubic SiC.

[0017] Hereinafter, means for solving the problems according to the present invention will be described. [1] In a method for manufacturing an SiC laminate in which a single-crystalline hexagonal SiC layer and a single-crystalline cubic SiC layer are laminated via a coherent interface, a positive inclination angle (θ b ) that is a depression angle of 0.5 degrees or more and less than 30 degrees from the basal plane (P f ) of the hexagonal SiC layer, and a positive inclination direction (α f ) that coincides with either <11-20> azimuth or <1-100> azimuth, a positive inclined plane (P f ) inclined in the direction is formed, and adjacent to the positive inclined plane, a negative inclination direction (α f ) opposite to the positive inclination direction, a negative inclination angle (θ b ) that is a depression angle of 54 degrees or more from the basal plane (P r ) is formed, and a negative inclined plane (P r ) inclined in the direction is formed. The ridge line deflection angle (Φ f ), which is the angle formed by the ridge line (J), which is the line where the positive inclined plane (P r ) and the negative inclined plane (P j ) abut at their respective uppermost parts, and the positive inclination direction is 15 degrees or more and 86 degrees or less, and the ridge line (J) is composed of a connection of two or more line segments, and at least one of the inflection points of the ridge line, which is the connection point of these line segments, is a ridge line apex (τ) protruding in the negative inclination direction (α r ). The method for manufacturing an SiC laminate includes a horizontal epi process of epitaxially growing SiC in a direction parallel to the basal plane (P b ) of the hexagonal SiC layer. A method for manufacturing a SiC laminate of [2][1], wherein two or more ridgeline vertices (τ) are provided, and each ridgeline vertex (τ) is in a non-inclined direction (α f ) that is orthogonal to the positive inclination direction (α p ) and is arranged so as not to be in series. A method for manufacturing a SiC laminate, characterized in that.

[0018] In the case where the Miller index indicating the plane orientation of the SiC crystal is originally a negative value, a horizontal line (bar) should be described above the corresponding number. However, since such a description cannot be made, in this specification and the claims, a minus sign "-" is attached before the corresponding number for expression. [Advantages of the Invention]

[0019] First, in order to explain the effects of the present invention, the terrace (P x ) composed of the closest-packed plane of Si-C molecules formed on the SiC surface and its end face, the step (S x ) will be described in terms of microscopic structure. In hexagonal SiC, the closest-packed plane is parallel to the basal plane of the crystal. The hexagonal SiC single crystal has many crystal polymorphs, and in each crystal polymorph, the closest-packed planes of Si-C molecules are stacked while maintaining a specific periodicity in the normal direction (α z ). When the surface of the closest-packed plane is Si-polar, α z is the

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

[0020] Also, on the SiC surface inclined in the positive inclination direction (α f ) that coincides with either a specific <11-20> orientation or a specific <1-100> orientation from the basal plane, terraces (P x ) and steps (S x ) corresponding to their ends are exposed at approximately equal intervals. The step (S x ) is orthogonal to the positive inclination direction (α f ) and extends along a non-inclined direction (α p ) that is parallel to the basal plane. For example, in the positive inclination direction (α f) When the [11 - 20] azimuth is set, the non-inclined direction (α p ) becomes the [-1100] azimuth. Alternatively, when the positive inclined direction (α f ) is set to the [1 - 100] azimuth, the non-inclined direction (α p ) becomes the [-1 - 120] azimuth. Also, the terrace that is relatively positioned in the negative inclined direction (α f ), which is the opposite direction of the positive inclined direction (α r ), is relatively positioned in the normal direction (α f ) with respect to the base plane compared to the terrace located in the positive inclined direction (α z ). In this specification, the terrace or step that is relatively positioned upward with respect to the normal direction (α z ) with respect to the base plane is called the upstream side, and the terrace or step that is relatively positioned downward is called the downstream side. Also, the phenomenon in which the upstream step grows laterally to the downstream side is called flow in this specification.

[0021] As shown in Patent Document 1, by providing a seed plane parallel to the base plane and an inclined plane inclined on the surface of the hexagonal SiC layer, the two-dimensional nuclei of cubic SiC generated on the seed plane can be laterally expanded on the inclined plane, and it is possible to form a cubic SiC layer on the hexagonal SiC layer. For example, as shown in Fig. 2(a), on the surface of the hexagonal SiC layer (L h ), a positive inclined plane (P b ) inclined at a certain positive inclination angle (θ f ) from the base plane (P f ) in the positive inclined direction (α f ) is provided, and further, a negative inclined plane (P f ) inclined from the base plane (P r ) at a uniform negative inclination angle (θ b ) in the opposite direction of the positive inclined direction (α r ) is provided. Then, a ridgeline (J) extending in a straight line is formed in the non-inclined direction (α f ) orthogonal to the positive inclined direction (α p ). Here, when epitaxial growth of SiC is performed in a direction parallel to the base plane (P b ), as shown in Fig. 2(b), the positive inclined plane (P f ) and the negative inclined plane (P r ) are in the normal direction (α zStarting from the ridge line (J) that meets at the top of (), the seed plane (P b ) expands in the positive inclination direction (α f ) along the base plane (P s ).

[0022] Next, as shown in Fig. 2(c), when the width of the seed plane (P s ) exceeds the critical width (w c ) of two-dimensional nucleation determined by the temperature of the horizontal epitaxial process described later, two-dimensional nuclei (γ) of cubic SiC are generated near the center of the seed plane, and a cubic SiC layer expands on the seed plane (P s ) due to the flow at its ends. As a result, as shown in Fig. 2(d), a cubic SiC layer (L h ) can be obtained on the hexagonal SiC layer (L c ). Even if multiple two-dimensional nuclei (γ) of cubic SiC are generated simultaneously by multiple nucleations, as long as the surface of the seed plane (P s ) is parallel to the base plane (P b ), the stacking order of each two-dimensional nucleus (γ) of cubic SiC is the same, and the resulting cubic SiC layer (L c ) does not contain DPB.

[0023] However, as shown in Fig. 3(a), when the deflection angle (φ f ) of the ridge line with respect to the positive inclination direction (α j ) is less than 88 degrees, a flow of the step (S p ) also occurs in the non-inclination direction (α x ) from the ridge line (J), and the width of the seed plane (P s ) continues to be narrowed to below the critical width (w c ) of two-dimensional nucleation. As a result, as shown in Fig. 3(b), the generation of two-dimensional nuclei (γ) of cubic SiC is blocked, and a cubic SiC layer cannot be obtained. Microscopically, this phenomenon is as shown in Fig. 4. When the ridge line (J) crosses the terrace (P x ) from the upstream side to the downstream side, the upstream step continuously flows to the downstream side, preventing the expansion of the seed plane (P s ).

[0024] In contrast, in the method for producing 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 between 15 degrees and 86 degrees is φ j1 , φ j2 The intersection point of each line segment, the ridge line vertex (τ), is in the negative gradient direction (α r ) to orient the

[0025] The ridge line apex (τ) is in the normal direction (α z ) and the seed surface (P s ) is expanded, and the seed surface (P s ) is the critical width for two-dimensional nucleation (w c ) beyond the seed surface (P s ) near the center of the step. The ridge line apex (τ) is located at the upstream of the flowing step, so the seed surface (P s ) is not hindered from expanding, 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.

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

[0027] In the method for manufacturing a SiC laminate provided by Patent Document 1, as shown in Fig. 6(a), the ridgeline (J) corresponding to the end of the negative inclination direction (α r ) is a straight line substantially parallel to the non-inclination direction (α p ). Further, the end of the positive inclination direction (α f ) is also terminated by a coherent interface strictly parallel to the non-inclination direction (α p ). When the width of the seed surface (P s ) with such parallel ends reaches the critical width (w c ) for two-dimensional nucleus generation, a plurality of inscribed circles (C s ) can be simultaneously drawn on the seed surface (P γ ). Therefore, the two-dimensional nucleus (γ) of cubic SiC becomes multi-nucleus generation, and when the surface tolerance is large, the stacking of all the two-dimensional nuclei (γ) generated on the seed surface (P s ) does not match, and DPB occurs in the cubic SiC layer unless the surface structure stabilization process provided by Patent Document 1 is performed.

[0028] On the other hand, in the method for manufacturing a SiC laminate provided by the present invention, one end of the seed surface (P s ) is not parallel to the non-inclination direction (α p ) and corresponds to a ridgeline (J) including one or more ridgeline vertices (τ). Therefore, as shown in Fig. 6(b), when the seed surface (P s ) expands to reach the critical width (w c ) for two-dimensional nucleus generation, a plurality of (C s ) cannot be simultaneously drawn on the seed surface (P γ ), and the two-dimensional nucleus (γ) of cubic SiC is always generated as a single nucleus, suppressing the occurrence of DPB in the cubic SiC layer.

[0029] Furthermore, in the method for manufacturing a SiC laminate provided by the present invention, the shape of the expanding cubic SiC layer is the arrangement of the ridgeline, the positive inclination angle (θ f ), the ridgeline deflection angle (φ j)、Since it is uniquely determined by the thickness of the SiC film grown in the horizontal epitaxial process, a cubic SiC layer that matches the design of the required 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 ridgeline vertices (τ) on the ridgeline (J). In this case, a plurality of cubic SiC layers (L c ) and a plurality of hexagonal SiC layers (L h ) can be manufactured to form a SiC laminate in which they are alternately laminated.

[0031] Also, since each ridgeline vertex (τ) is arranged so as not to be in series in the non-inclined direction (α p ), a plurality of seed planes (P s ) that expand starting from the ridgeline vertex (τ) are displaced relative to the normal direction (α z ) to the basal plane. For this reason, a plurality of cubic SiC layers (L c ) that expand in a direction parallel to the basal plane through the horizontal epitaxial process from the two-dimensional nuclei (γ) of cubic SiC generated on each seed plane do not meet on the same basal plane, and the occurrence of DPB can be surely suppressed.

[0032] As described above, in the method for manufacturing a SiC laminate provided by the present invention, the formation of the cubic SiC layer contained in the SiC laminate is ensured, and no DPB occurs in the formed cubic SiC layer. Therefore, a SiC laminate suitable for a high-performance semiconductor device can be manufactured with high reproducibility.

[0033] Also, in the present invention, the arrangement of a plurality of ridgeline vertices (τ) enables the manufacture of a SiC laminate having an arbitrary multilayer structure. By utilizing the 2DEG or 2DHG generated at the interface, or by utilizing the quantum well structure formed by the cubic SiC layer sandwiched between hexagonal SiC layers above and below, it is also possible to obtain a more multifunctional semiconductor device.

Brief Description of the Drawings

[0034]

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Embodiments for Carrying Out the Invention

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

[0036] [Embodiment 1] In manufacturing a SiC laminate, a single-crystalline hexagonal SiC wafer can be used as a substrate. As the single-crystalline SiC wafer, 4H-SiC or 6H-SiC wafers are commercially available, but a 4H-SiC wafer having an E of 3.2 eV suitable for manufacturing a high-voltage power semiconductor device g is preferably used because a high-voltage power semiconductor device can be manufactured.

[0037] Furthermore, if the surface of a 4H-SiC wafer inclined at a certain angle from the (0001) plane, which is the basal plane (P b ), is used, the surface can be utilized as a positive inclined plane (P s ), so that the manufacturing process of the positive inclined plane (P s ) can be omitted. In this case, as the polarity of the substrate surface, the Si plane or the C plane can be selected according to the application, but it is preferable to use the Si plane side most suitable for manufacturing a power semiconductor. However, when attempting to obtain 2DEG at the interface between the cubic SiC layer and the hexagonal SiC layer, the C plane side can also be used.

[0038] The inclination angle of the surface of the 4H-SiC wafer with respect to the basal plane corresponds to the positive inclination angle (θ f ), and if this value is in the range of 0.5 degrees or more and less than 54 degrees, the effects of the present invention can be obtained. The lower the positive inclination angle (θ f ), the more the expansion of the cubic SiC surface area formed in the horizontal epi process described later can be promoted. However, when the positive inclination angle (θ f ) is less than 0.5 degrees, the positive inclined plane (P sThe step interval on the surface of ) is 50 μm or more, and two-dimensional nucleation of cubic SiC occurs even on a terraced surface with a positive inclined plane, making it difficult to obtain a coherent interface at the interface between cubic SiC and 4H-SiC. Further, in order to make the film thickness error of the cubic SiC obtained by the horizontal epitaxial process within 5%, it is more desirable that the angle be 1 degree or more and less than 30 degrees. Therefore, in this embodiment, a positive inclination angle of 4 degrees, which is widely used for commercially available 4H-SiC wafers, is used (θ f )

[0039] The positive inclination direction (α f ) can be selected from either the [1-100] orientation or the [11-20] orientation to obtain the effects of the present invention. In this embodiment, the [11-20] orientation, which is the inclination direction of a general commercially available wafer, is selected. In this case, the negative inclination direction (α r ) is the [-1-120] orientation, and the non-inclination direction (α p ) is the [1-100] orientation

[0040] Next, a part of the positive inclined plane (P s ) is processed to form a negative inclined plane (α r ). To obtain the negative inclined plane (α r ), it is necessary to form a partial plane inclined in the negative inclination direction (α f ), which is the direction opposite to the positive inclination direction (α r ). When forming the partial plane corresponding to the negative inclined plane (P r ), it is possible to perform groove processing using laser processing or machining and use the side wall of the groove as the negative inclined plane (P r ). However, in view of the reproducibility of the processing shape, dimensional accuracy, and controllability of the negative inclination angle (θ r ), it is most desirable to form a groove by combining photolithography and dry etching and use its side wall.

[0041] Specifically, a photoresist pattern is arranged on the substrate by the photolithography method so as to have the shape of a desired positive inclined plane (P f ). Using this photoresist pattern as a mask, a groove is formed on the 4H-SiC substrate by dry etching, and its side wall is used as the negative inclined plane (Pr ) is used. In dry etching, a parallel plate type plasma etching apparatus or an inductively coupled plasma etching apparatus is used, and a fluorine-based gas such as SF 6 or CF 4 is ionized and irradiated onto the SiC substrate to form a groove. At this time, by adjusting the difference in etching rates between the photoresist and SiC, the negative inclination angle (θ r ) can be adjusted.

[0042] The deeper the groove formed by the above dry etching, the larger the area of the negative inclined surface (P r ), so it becomes possible to increase the film thickness of the SiC layer formed in the horizontal epi process described later. However, not only does the shape error of the ridgeline (J) increase with the increase in the dry etching time, but also the roughness of the negative inclined surface (P r ) increases. Therefore, it is desirable that the depth of the groove be 2 μm or less.

[0043] In the above process, the side wall of the etched groove becomes the negative inclined surface (P r ) shown in Fig. 5(a), and the depression angle from the base surface to the side wall becomes the negative inclination angle (θ r ). Also, the line where the positive inclined surface (P f ) and the negative inclined surface (P r ) abut on the substrate surface corresponds to the ridgeline (J). This coincides with the end on the negative inclination direction (α r ) side of the photoresist pattern described above. Here, the negative inclination angle (θ r ) may be 54 degrees or more. However, in this embodiment, since it is easier to control the structure of the SiC laminate by suppressing the expansion of the seed surface in the negative inclination direction (α r ), the negative inclination angle (θ r ) is set to a value as close to 90 degrees as possible. For this reason, a groove having a side wall perpendicular to the SiC wafer surface is formed.

[0044] In order to exhibit the effects of the present invention and obtain cubic SiC containing no BPD at a predetermined location, the above positive inclined surface (P f ) and negative inclined surface (P rIt is necessary to control the shape of the ridge line (J) formed by the convergence of the uppermost parts of as follows. First, the ridge line deflection angle (φ f ), φ j1 between the ridge line (J) and a straight line parallel to the positive inclination direction (α j2 ) needs to be 15 degrees or more and 86 degrees or less. The ridge line deflection angle described here is the angle on the acute angle side when a line parallel to the positive inclination direction intersects the ridge line. When the ridge line deflection angle is less than 15 degrees, the width of the seed surface formed near the top of the ridge line becomes narrow, making it difficult to generate two-dimensional nuclei (γ) of cubic SiC. Also, even if two-dimensional nuclei (γ) of cubic SiC are generated, their expansion in the non-inclined direction (α p ) is restricted. Therefore, it is more desirable that both φ j1 and φ j2 be 30 degrees or more. On the other hand, when the ridge line deflection angle exceeds 86 degrees, due to the alignment error in the photolithography process described above, there is a high possibility that the ridge line (J) will be parallel to the non-inclined direction in part, resulting in the generation of multiple two-dimensional nuclei (γ) of cubic SiC. For this reason, preferably, the upper limit of the ridge line deflection angle is 82 degrees.

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

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

[0047] When carrying out the horizontal epitaxial process using the vapor phase growth method, a commercially available vapor phase growth apparatus is used. A 4H-SiC wafer with the inclined surface processed is placed on a graphite susceptor coated with SiC, and this is placed in a quartz reaction vessel. The 4H-SiC wafer is heated to a predetermined temperature by inductively heating the susceptor from the outside of the reaction vessel, and then a source gas is introduced into the reaction vessel to achieve epitaxial growth of SiC. As the source gas, silane-based gases such as SiH 4 and Si 2 H 6 , chlorosilane-based gases such as SiHCl 3 and SiCl 4 , hydrocarbon gases such as CH 4 , C 3 H 8 , C 2 H 2 , and organic silane-based gases such as (CH) 3 SiH and (CH)SiH 3 can be used in combination. By maintaining the wafer temperature at a constant temperature in the range of 1400°C to 1700°C during epitaxial growth, SiC single crystals grow epitaxially in a direction parallel to the basal plane. In particular, when the wafer temperature is in the range of 1450°C to 1550°C, two-dimensional nuclei of cubic SiC are likely to be generated on the seed surface, and a high-quality single-crystal SiC layer can be obtained.

[0048] For example, when the wafer temperature is 1500°C and the flow rate of H 2 , which is the carrier gas, is maintained at 5 slm, while the flow rate of SiH 4 is 50 sccm and the flow rate of C 3 H8 The flow rate is introduced into the vapor deposition apparatus at 13 sccm, and by setting the internal pressure of the reaction vessel to 300 hPa, on the positive inclined plane (P f ) having a positive inclination angle of 4 degrees (θ f ), the step flows at a speed of 171 μm / hour. As a result, an epitaxial film growth rate of 12 μm / hour is obtained in the direction (α z ) perpendicular to the basal plane. As a result, by epitaxial growth for 25 minutes, a cubic SiC epitaxial growth layer with a thickness of 5 μm is obtained on the seed plane (P s ) of hexagonal SiC. Further, the maximum width in the positive inclination direction (α f ) of the cubic SiC layer is 72 μm.

[0049] As described above, according to the method for manufacturing the SiC laminate of the present embodiment, single nucleation of cubic SiC is realized on the seed plane whose position is specified by the ridgeline vertex, and the cubic SiC layer step-flows in the positive inclination direction according to the film thickness of the SiC epitaxial growth layer formed in the positive inclination angle and horizontal epi process. At the same time, it expands in the non-inclined direction along the ridgeline, which is the boundary between the positive inclined plane and the negative inclined plane. Therefore, it is possible to obtain a single-layer cubic SiC layer without DBP on the hexagonal SiC epitaxial growth layer with the designed shape and film thickness. For this reason, it is possible to manufacture power semiconductor devices such as vertical power MOSFETs with low loss and high reliability with good reproducibility.

[0050] [Embodiment 2] By providing a plurality of ridgeline vertices on a continuous ridgeline, it is possible to alternately stack hexagonal SiC and cubic SiC. However, if the positions of the protrusions are in series in the non-inclined direction, the seed plane expands on the same basal plane while starting from different ridgeline vertices, so that a desired multilayer structure cannot be obtained. In addition to this, not all of the two-dimensional nuclei of cubic SiC generated on a plurality of seed planes have the same stacking structure, and there is a possibility that cubic SiC layers expanding on the same basal plane may meet and generate DPB, making it difficult to exhibit the effects of the present invention.

[0051] On the one hand, in the method for manufacturing the SiC laminate provided by the present invention, since different ridgeline vertices can be arranged so as not to be in series in the non-inclined direction, cubic SiC layers expanding from each ridgeline vertex do not meet on the same base plane, and are always separated by a hexagonal SiC layer, and the generation of DPB in the cubic SiC layer is suppressed.

[0052] The shape of each ridgeline vertex in this embodiment is the same as that in Embodiment 1. However, in order to specify the positional relationship and film thickness between the hexagonal SiC layer and the cubic SiC layer in the laminate structure, it is necessary to accurately determine the relative positions of a plurality of ridgeline vertices as described later.

[0053] In the method for manufacturing the SiC laminate provided by the present invention, the same number of cubic SiC layers as the number of ridgeline vertices formed on the hexagonal SiC can be obtained. FIG. 8 is a plan view showing an embodiment of the process for manufacturing a SiC laminate including a two-layer cubic SiC. As shown in FIG. 8(a), a positive inclined plane (P f ) and a negative inclined plane (P r ) are provided on the hexagonal SiC substrate, and two ridgeline vertices (τ 1 , τ 2 ) are provided on the ridgeline (J). In addition, as the bent portions of the ridgelines extending in the positive inclined direction from each of the ridgeline vertices τ 1 and τ 2 , ridgeline valley points (ν 1 ) with vertices oriented in the positive inclined direction are also formed.

[0054] Since a plurality of ridgeline vertices (τ 1 , τ 2 ) need to be arranged so as not to be in series in the non-inclined direction (α p ), τ 1 and τ 2 are arranged such that the lengths of the perpendiculars from the straight line (S 1 ) parallel to the non-inclined direction passing through the ridgeline valley point (ν 1 ) to each ridgeline vertex are different. In this embodiment, the length of the perpendicular from S 1 to τ 1 is a 1 , and the length of the perpendicular from S 1 to τ 2Let the length of the perpendicular line up to be a 2 and let a 2 be a value larger than a 1 . Therefore, τ 2 is located upstream of τ 1 . When a horizontal epitaxial process is performed here, as shown in Fig. 8(b), τ 1 , τ 2 , two seed surfaces (Ps 1 , Ps 2 ) expand in the positive inclination direction (α f ) starting from the peak point of the ridgeline of τ

[0055] Furthermore, by continuing the horizontal epitaxial process, as shown in Fig. 8(c), on the expanded seed surfaces P s1 and P s2 , two-dimensional nuclei (γ 1 , γ 2 ) of cubic SiC are formed. Here, let the two-dimensional nucleus of cubic SiC on P s1 be γ 1 , and the two-dimensional nucleus on P s2 be γ 2 .

[0056] The steps corresponding to the ends of the two-dimensional nuclei (γ 1 , γ 2 ) of each cubic SiC flow in the positive inclination direction (α f ) and expand in the positive and negative non-inclination directions (α p ) along the ridgeline (J), and as shown in Fig. 8(d), two layers of cubic SiC are obtained on the positive inclination surface (P f ). Here, let the cubic SiC layer starting from the end of τ 1 be the L c1 layer, and the cubic SiC layer starting from the end of τ 2 be the L c2 layer. Then, as shown in Fig. 9, the cross-sectional structure of the obtained SiC laminate is such that the cubic SiC layer (L 2 ) starting from the peak point of the ridgeline located upstream (τ c2 ) is the upper layer than the cubic SiC layer (L 1 ) starting from the peak point of the ridgeline located downstream (τ c1 ), and each cubic SiC layer (L c1 and L c2) is isolated by a hexagonal SiC layer (L h2 ).

[0057] Here, the relative positional relationship between L c1 and L c2 is uniquely determined by the positive inclination angle (θ f ) and the displacement amount (a 1 , a 2 ) in the negative inclination direction of the ridgeline vertex. The distance (d c1 ) from the bottom of L c2 to the bottom of L 2 is d 2 = (a 2 - a 1 ) × TAN(θ f ). For example, if the positive inclination angle (θ f ) is 4 degrees, a 2 is 14 μm, and a 1 is 10 μm, then d 2 is determined to be 0.28 μm. Also, since the film thickness d c1 of the L 1 layer is determined as d 1 = d 2 × a 1 / a 2 , d 1 becomes 0.2 μm. Since the thickness of the hexagonal SiC layer L c1 sandwiched between L c2 and L h2 is d 2 - d 1 , it can be determined to be 0.08 μm.

[0058] As described above, in the present invention, 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 is possible, and the interval between each SiC layer constituting the laminate can be controlled by the positive inclination angle (θ f ), and the arrangement of the ridgeline vertex (τ).

[0059] Note that since the method for selecting the SiC wafer used in this embodiment, the processing method for the negative inclined surface, and the conditions for the horizontal epi process are the same as those in Embodiment 1, the description thereof is 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 the respective ends are connected (however, a negative inclined surface is not shown in FIG. 10). As a result, a plurality of ridgeline lines (J 1 , J 2 , J 3 , J 4 ) are formed discontinuously. On the ridgeline line J 1 , three ridgeline line tops (τ 11 , τ 12 , τ 13 ) are arranged. On the ridgeline line J 2 , two ridgeline line tops (τ 21 , τ 22 ) are arranged. On the ridgeline line J 3 , two ridgeline line tops (τ 31 , τ 32 ) are also arranged. However, the plurality of ridgeline line tops are not arranged in series in the non-inclined direction (α p ). Also, the ridgeline line deflection angle (φ j ) formed by the ridgeline lines (J 1 , J 2 , J 3 ) and the positive inclined direction is 30 degrees or more and 82 degrees or less.

[0061] Here, when a horizontal epitaxial process is performed, three cubic SiC layers (L c11 , L c12 , L c13 ) expand onto P f2 from each of the ridgeline line tops (τ 11 , τ 12 , τ 13 ) on the ridgeline line (J 1 ) adjacent to P f1 . From each of the ridgeline line tops (τ 21 , τ 22 ) on the ridgeline line (J 2 ) adjacent to P f2 , two cubic SiC layers (L c21 , L c22 ) expand onto the positive inclined surface P f3 as the lower layer of the L c13 layer. Further, P f3The ridgeline (J adjacent to 3 ) on the ridgeline top (τ 31 , τ 32 ) respectively, from each of them, L c22 As the lower layer of the L layer, two layers of cubic SiC layers (L c31 , L c32 ) expand on the positive inclined plane P f4 .

[0062] As a result of performing the above horizontal epitaxial process, the cross-section at the position corresponding to M in FIG. 10 is, as shown in FIG. 11(a), from the lower layer, the L layer of hexagonal SiC, the L layer of cubic SiC, the L layer of hexagonal SiC, the L layer of cubic SiC, the L layer of hexagonal SiC, the L layer of cubic SiC are stacked to form a structure. Also, the cross-section at the position corresponding to M in FIG. 10 is, as shown in FIG. 11(b), under the stacked structure of the cross-section of M, the L layer of hexagonal SiC, the L layer of cubic SiC, the L layer of hexagonal SiC, the L layer of cubic SiC are stacked to form a structure. Furthermore, in the cross-section at the position corresponding to M in FIG. 10, as shown in FIG. 11(c), under the stacked structure of the cross-section of M, the L layer of hexagonal SiC, the L layer of cubic SiC, the L layer of hexagonal SiC, the L layer of cubic SiC are stacked to form a structure, and this expands on the positive inclined plane P 1 . h13 layer, the L layer of cubic SiC c13 layer, the L layer of hexagonal SiC h12 layer, the L layer of cubic SiC c12 layer, the L layer of hexagonal SiC h11 layer, the L layer of cubic SiC c11 layer. Also, the cross-section at the position corresponding to M in FIG. 10 is, as shown in FIG. 11(b), under the stacked structure of the cross-section of M, the L layer of hexagonal SiC 2 . 1 layer, the L layer of cubic SiC h22 layer, the L layer of hexagonal SiC c22 layer, the L layer of cubic SiC h21 layer are stacked to form a structure. Furthermore, in the cross-section at the position corresponding to M in FIG. 10, as shown in FIG. 11(c), under the stacked structure of the cross-section of M, the L layer of hexagonal SiC c21 layer, the L layer of cubic SiC 3 . 2 layer, the L layer of hexagonal SiC h32 layer, the L layer of cubic SiC c32 layer, the L layer of hexagonal SiC h31 layer, the L layer of cubic SiC c31 layer are stacked to form a structure, and this expands on the positive inclined plane P f4 .

[0063] As described above, by flowing the structure that appears in the step of the positive inclined plane where the multilayer SiC stacked structure is formed to the downstream positive inclined plane, it becomes possible to form a further multilayered SiC stacked structure.

[0064] Here, each positive inclined plane (P f1 , Pf2 , P f3 ) The narrower the width of, the easier it is for the basal plane dislocations (BPDs) contained in the epitaxially grown SiC layer on the upstream side to be discharged to the end of the positive inclined plane of the lower layer, and it becomes possible to obtain a SiC laminate with a lower BPD density toward the downstream side.

[0065] Note that the method for selecting the SiC wafer used in this embodiment, the processing method of the negative inclined plane (P r ), the conditions of the horizontal epi process, and the arrangement of each ridgeline (J) and the shape of the ridgeline apex (τ) are the same as those in Embodiment 1, so their descriptions are omitted.

Example

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

[0067] (Negative inclined plane processing step) The step of forming the negative inclined plane (P r ) and the ridgeline (J) is shown using FIG. 12. First, the positive inclined plane (P f) to form a resist pattern covering the corresponding part. Since the part covered by the resist pattern corresponds to the surface inclined by 4 degrees in the [11 - 20] azimuth from the (0001) plane (Si plane), the positive inclination angle (θ f ) is 4 degrees. In this step, as shown in Fig. 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, using a laser drawing device (DWL2000 GL manufactured by Heidelberg Instruments Co., Ltd.), the photoresist (Res) is exposed and developed except for the part corresponding to the positive inclined surface (P f ), so that, as shown in Fig. 12(b), openings of the photoresist (Res) are formed except for the region corresponding to the positive inclined surface.

[0068] After that, using an ICP-RIE device (MUC-21 manufactured by Sumitomo Precision Products Co., Ltd.), the opening part is etched. In the etching, CF 4 gas 400 sccm and O 2 gas 100 sccm are introduced, an ICP output of 1 kW is input to excite the plasma, and dry etching of 0.8 μm is performed in 15 minutes to form a groove. Then, the photoresist (Res) on the 4H-SiC wafer (Wf) is removed with a mixed acid of hydrogen peroxide and sulfuric acid. The side wall of this groove forms an angle of 80 degrees to 83 degrees with respect to the wafer surface, and the value obtained by adding the positive inclination angle (θ f ) of 4 degrees is the negative inclination angle (θ r ) of the negative inclined surface (P r ) which is 84 degrees to 87 degrees. Also, a part of the boundary between the positive inclined surface (P f ) and the negative inclined surface (P r ) covered by the photoresist (Res) during dry etching functions as a ridgeline (J).

[0069] (Shape of the ridgeline) The shape of the element pattern constituting the exposure shape is as shown in Fig. 13, and the element pattern has a ridgeline valley part (ν 1 ) at the upper end and a ridgeline valley part (ν 1) It is translated and exposed by translational operations in the non-inclined direction and the positive inclined direction so as to be consistent, and a ridge line continuous from the lower end to the upper end of the 4H-SiC wafer (Wf) is formed. However, the width of the positive inclined surface in contact with each element pattern shall be 50 μm or more.

[0070] The ridge line top (τ 1 , τ 2 ) that constitutes the element pattern shown in Fig. 13 j1 , φ j2 , φ j3 , φ j4 ) and the ridge line deflection angle are as shown in Table 1. Element patterns No. 1 to No. 3 conform to the manufacturing method of the SiC laminate provided by the present invention, and the ridge line forms an included angle with the positive inclined direction (α f ) at a ridge line deflection angle of 76 degrees to 81 degrees (φ 1 , τ 2 ). In addition, the two ridge line tops (τ p ) on the ridge line are arranged so as not to be in series in the non-inclined direction (α

[0071] ). In element pattern No. 4, the ridge line forms an included angle with the positive inclined direction (α j1 , φ j2 , φ j3 , φ j4 ) at a ridge line deflection angle of 71 degrees to 76 degrees (φ f ). However, since the two ridge line tops (τ 1 , τ 2 ) on the ridge line are arranged in series in the non-inclined direction (α p ), it does not conform to the manufacturing method of the SiC laminate provided by the present invention.

[0072] In element pattern No. 5, the two ridge line tops (τ 1 , τ 2 ) on the ridge line are arranged so as not to be in series in the non-inclined direction, but the ridge line forms an included angle with the positive inclined direction (α j1 , φ j2 , φ j3 , φ j4 ) at a ridge line deflection angle of 7 degrees to 11 degrees (φ f ), so it does not conform to the manufacturing method of the SiC laminate provided by the present invention.

[0073] In element pattern No. 6, the two ridgeline tops (τ 1 , τ 2 ) on the ridgeline are arranged so as not to be in series in the non-inclined direction, but the ridgeline forms an included angle with the positive inclination direction (α j1 , φ j2 , φ j3 , φ j4 ) at a ridgeline deflection angle of 89 degrees (φ f ), so it does not correspond to the manufacturing method of the SiC laminate provided by the present invention.

[0074] In element pattern No. 7, a 1 , a 2 , a 3 , a 4 are zero, and ridgeline tops are not formed in the same manner as the manufacturing method of the SiC laminate provided in Patent Document 1. Also, the ridgeline deflection angle (φ j1 , φ j2 , φ j3 , φ j4 ) is 90 degrees and the ridgeline (J) is parallel to the non-inclined direction (α p ). Therefore, it does not correspond to the manufacturing method of the SiC laminate provided by the present invention.

[0075] In element pattern No. 8, the ridgeline deflection angle (φ j1 ) is 84 degrees and the ridgeline (J) is not parallel to the non-inclined direction (α p ), but a 2 , a 3 , a 4 are zero, and ridgeline tops are not formed. Therefore, it does not correspond to the manufacturing method of the SiC laminate provided by the present invention.

[0076]

Table 1

[0077] (Horizontal epitaxial process) After forming ridgelines composed of the eight different element patterns described above on the same 4H-SiC wafer, epitaxial growth of SiC is performed as a horizontal epi process. At this time, the wafer temperature is set to 1500 °C, and while maintaining the flow rate of H 2 as the carrier gas at 5 slm, the flow rate of SiH 4 is set to 50 sccm, and the flow rate of C 3 H 8 is introduced into the vapor deposition apparatus at 13 sccm, and epitaxial growth of SiC is performed by setting the pressure inside the reaction vessel to 300 hPa. At this time, steps flow at a rate of 171 μm / hour on the positive inclined surface (P f ) having a positive inclination angle (θ s ) of 4 degrees, and an epitaxial film grows at a rate of 12 μm / hour in the direction perpendicular to the basal plane (α z ). As a result, an epitaxial growth layer of 3C-SiC with a thickness of 5 μm is obtained on the seed surface (P s ) of 4H-SiC by 25 minutes of epitaxial growth. Also, the maximum width in the positive inclination direction (α f ) of the 3C-SiC layer is 72 μm.

[0078] (Structure Evaluation of SiC Stacked Body) After the horizontal epi process, using a scanning electron microscope (SEM) and a transmission electron microscope (TEM), the surface and cross-sectional structures of the SiC epitaxial growth layer are observed, and the crystal structure distribution of SiC is observed using the electron backscatter diffraction method (EBSD). By this observation, the state of the 3C-SiC surface, the DPB density, and the cross-sectional structure of the SiC stacked body for each element pattern are measured. In particular, regarding the cross-sectional structure of the SiC stacked body, in light of the structure shown in FIG. 9, the film thickness (d 1 ) of the 3C-SiC layer and the interval (d 2 ) between the 3C-SiC layers segmented by the 4H-SiC layer are obtained, and these are summarized in Table 2.

[0079]

Table 2

[0080] As shown in Table 2, when using No.1 to No.3 of the element patterns, a 3C-SiC layer continuous in the non-inclined direction is found on the surface of the SiC laminate, and it is confirmed that it does not contain DPB. Also, a multilayer structure of 3C-SiC through the 4H-SiC layer is found, and the interval (d 2 ) between adjacent 3C-SiC layers is confirmed to maintain the relationship of (a 2 -a 1 )×TAN(θ f ). Also, the film thickness (d 1 ) of 3C-SiC in the lower layer of 4H-SiC almost coincides with the value derived from d 2 ×a 1 / a 2 . 。

[0081] Although the presence of 3C-SiC continuous in the non-inclined direction can be confirmed on the surface of the SiC epitaxial growth layer on element pattern No.4, it is found from EBSD that it contains DBP with a density of 530 mm ―1 . Also, 3C-SiC exists only in the surface layer, and all its lower layers are 4H-SiC.

[0082] In the SiC epitaxial growth layers on element patterns No.5 and No.8, no 3C-SiC layer is found, and the surfaces of the positive inclined planes are all covered with 4H-SiC layers.

[0083] Although the presence of 3C-SiC can be confirmed on the surfaces of the SiC epitaxial growth layers on element patterns No.6 and No.7, it is discontinuous in the non-inclined direction and is found from EBSD to contain DBP although slightly.

[0084] As in the above embodiments, in the method for manufacturing a SiC laminate provided by the present invention, a ridgeline that forms the boundary between the positive inclined surface and the negative inclined surface is provided, and by providing a ridgeline apex protruding in the negative inclination direction, the generation of cubic SiC is ensured. Further, it has been clarified that by not arranging a plurality of ridgeline apexes in series in the non-inclined direction, a multilayer structure in which cubic SiC and hexagonal SiC are alternately laminated can be formed. Furthermore, it has been verified that by adjusting the relative arrangement of a plurality of ridgeline apexes, DPB can be eliminated, and it is possible to manufacture an optimal SiC laminate structure for manufacturing various semiconductor devices such as MOSFETs and HEMTs.

[0085] As described above, the embodiments of the present invention have been explained. However, the present invention is not limited to the above embodiments and forms in any way, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention. For example, the crystal polymorphism of hexagonal SiC is not limited to 4H-SiC, and even when 6H-SiC or 15R-SiC is used, a cubic SiC layer is surely generated, and the control of its laminated structure is also possible. Furthermore, the polar plane of the substrate surface is not limited to the Si plane, and the same effect can be obtained even with the C plane.

[0086] Also, the ridgeline does not necessarily have to be a straight line as in this embodiment, and the same effect can be obtained as long as the ridgeline deflection angle is in the range of 15 degrees or more and 86 degrees or less. The depression angle of the positive inclined surface or the negative inclined surface with respect to the ridgeline does not have to be constant either, and the shape of the cubic SiC layer can be controlled within the range described in this specification. Furthermore, the temperature, pressure, added impurities, and gas flow rate in the horizontal epitaxial process are not limited to this embodiment and the examples, and the optimal conditions can be adjusted as appropriate according to the need.

[0087] Furthermore, the ridgeline apex does not have to protrude with atomic-level sharpness, and it can be regarded as a protruding point as long as the curvature is substantially 10 μm or less.

Industrial Applicability

[0088] The SiC laminate in the present invention can be used as a substrate for power semiconductor devices such as MOSFETs, IGBTs, bipolar transistors, pn diodes, and SBDs, high-speed logic circuits using CMOS, and MEMS devices. Further, by taking advantage of the characteristics of the alignment heterointerface where different bandgaps and electron affinities are in contact, it can also be used as a substrate for high-frequency devices such as HBTs and HEMTs and high-efficiency solar cell modules.

Explanation of Signs

[0089] P b Base plane P f Positive inclined plane P r Negative inclined plane P s Seed plane P x Terrace S x Step θ f Positive inclination angle θ r Negative inclination angle α f Positive inclination direction α r Negative inclination direction α p Non-inclined direction α z Normal direction to the base plane J, J 1 , J 2 , J 3 Ridge line τ, τ 1 , τ 2 , τ 11 , τ 12 , τ 13 , τ 21 , τ 22 , τ 31 , τ 32 Ridge line vertex Φ j , Φ j1 , Φ j2 , Φ j3 Ridge line deflection angle 2D nucleus 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 d 1 Thickness of cubic SiC layer d 2 Distance between adjacent cubic SiC layers S 1 Reference line parallel to the non-inclined direction a 1 , a 2 Length of the perpendicular line from the reference line parallel to the non-inclined direction to the peak of the ridgeline a 3 , a 4 Length of the perpendicular line from the reference line parallel to the non-inclined direction to the valley of the ridgeline w c Critical width of two-dimensional nucleation θ τ Ridgeline bending angle ν, ν 1 Valley of the ridgeline C γ Inscribed circle on the seed surface Wf 4H-SiC wafer Res Positive photoresist

Claims

1. In a method for manufacturing a SiC laminate in which a single-crystalline hexagonal SiC layer and a single-crystalline cubic SiC layer are laminated via a coherent interface, a part of the surface of the hexagonal SiC layer has a positive inclination angle (θ ｂ ), which is a depression angle of 0.5 degrees or more and less than 30 degrees from the basal plane (P ｆ ), and coincides with either <11-20> orientation or <1-100> orientation in a positive inclination direction (α ｆ ), and a positive inclined surface (P ｆ ), and a step of forming a negative inclined surface (P ｆ ), which is adjacent to the positive inclined surface and has a depression angle of 54 degrees or more from the basal plane (P ｂ ), in a negative inclination direction (α ｒ ), which is opposite to the positive inclination direction, and a depression angle (θ ｒ ), and a step of forming a negative inclined surface (P ｆ ), and the negative inclined surface (P ｒ ), and a ridge line (J), which is a line where the positive inclined surface and the negative inclined surface are in contact with each other at their uppermost parts, and a ridge line deflection angle (Φ ｊ ), which is an included angle formed by the ridge line and the positive inclination direction, is 15 degrees or more and 86 degrees or less, and the ridge line (J) is composed of a connection of two or more line segments, and at least one of the inflection points of the ridge line, which is a connection point of these line segments, is a ridge line apex (τ) protruding in the negative inclination direction (α ｒ ), and a horizontal epitaxial step of epitaxially growing SiC in a direction parallel to the basal plane (P ｂ ) of the hexagonal SiC layer. A method for manufacturing a SiC laminate, characterized by including the above steps.

2. A method for manufacturing a SiC laminate according to claim 1, wherein two or more ridgeline vertices (τ) are provided, and each ridgeline vertex (τ) is in a non-inclined direction (α ｆ ), which is a direction orthogonal to the positive inclination direction (α ｐ ), and are arranged so as not to be in series. A method for manufacturing a SiC laminate, characterized by this.

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