Method for manufacturing aluminum nitride substrate, aluminum nitride substrate, and method for suppressing introduction of dislocations into aluminum nitride growth layer

Abstract

The present invention is to provide a novel technology capable of suppressing introduction of dislocations into an aluminum nitride growth layer. The present invention is a method for manufacturing an aluminum nitride substrate, including a processing step of removing a portion of a silicon carbide substrate and forming a pattern including an acute angle, and a crystal growth step of forming an aluminum nitride growth layer on the silicon carbide substrate on which the pattern is formed. Further, the present invention is a method for suppressing introduction of dislocations into an aluminum nitride growth layer, including a processing step of removing a portion of a silicon carbide substrate and forming a pattern including an acute angle before forming an aluminum nitride growth layer on the silicon carbide substrate.

Description

Technical Field

[0001] This invention relates to a method for manufacturing an aluminum nitride substrate, an aluminum nitride substrate, and a method for suppressing the introduction of dislocations into an aluminum nitride growth layer. Background Technology

[0002] In the past, in the manufacturing method of aluminum nitride substrates, a semiconductor substrate made of a desired semiconductor material was manufactured by crystal growth (so-called epitaxial growth) on a substrate.

[0003] However, in the epitaxial growth described above, the introduction of dislocations into the growth layer due to the extension of dislocations from the substrate to the growth layer is a problem.

[0004] Patent Document 1 discloses an invention in which a crystal growth is performed in a direction orthogonal to the c-axis by forming a groove on a silicon carbide (SiC) substrate, one example of which is a base substrate, thereby suppressing the propagation of through dislocations that exist on the SiC substrate and propagate in the c-axis direction.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2007-223821 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, it can be understood that the invention has room for improvement from the perspective of the introduction of new dislocations that would occur during the bonding of crystal growth surfaces in a direction orthogonal to the c-axis.

[0010] The problem to be solved by the present invention is to provide a novel technology that can suppress the introduction of dislocations into the aluminum nitride growth layer.

[0011] Problem-solving methods

[0012] The present invention, which solves the above problems, is a method for manufacturing an aluminum nitride substrate, comprising a processing step of removing a portion of a silicon carbide substrate and forming a pattern including a convex corner, and a crystal growth step of forming an aluminum nitride growth layer on the silicon carbide substrate on which the pattern is formed.

[0013] Thus, by performing crystal growth on a substrate having a pattern containing inferior angles, the present invention can suppress the introduction of dislocations into the growth layer.

[0014] In a preferred embodiment of the invention, the crystal growth step involves zipper bonding on the silicon carbide substrate to form an aluminum nitride growth layer. Thus, by performing crystal growth on a substrate with a pattern including inferior angles, the present invention achieves zipper bonding capable of suppressing the introduction of new dislocations.

[0015] In a preferred embodiment of the invention, the crystal growth step forms an aluminum nitride growth layer by performing crystal growth along the c-axis and crystal growth along the a-axis. Thus, the invention can form regions of dislocations that do not continue from the substrate during the formation of the growth layer.

[0016] In a preferred embodiment of the present invention, the crystal growth step is a growth step performed using a physical vapor transport method. Thus, the present invention can achieve the formation of a growth layer based on the transport of raw materials driven by a temperature gradient or chemical potential.

[0017] In a preferred embodiment of the present invention, the silicon carbide substrate and the aluminum nitride growth layer are made of different materials.

[0018] In a preferred embodiment of the invention, the processing steps include a through-hole forming step that removes a portion of the silicon carbide substrate to form a through-hole, and a strain layer removal step that removes the strain layer introduced by the through-hole forming step. Thus, the invention readily forms a temperature gradient along the a-axis, which becomes the driving force in crystal growth along the a-axis direction.

[0019] In a preferred embodiment of the invention, the through-hole forming step is a step of forming the through-hole by irradiating the silicon carbide substrate with a laser. Thus, the invention can form patterns including angular features based on the processing of a substrate without mechanical processing.

[0020] In a preferred embodiment of the invention, the strain layer removal step is a step of removing the strain layer of the silicon carbide substrate by performing heat treatment. Therefore, the present invention can reduce the defect density in patterns containing inferior angles.

[0021] In a preferred embodiment of the invention, the silicon carbide substrate is silicon carbide, and the strain layer removal step is a step of etching the silicon carbide substrate in a silicon atmosphere. Thus, the invention can planarize the top and sidewalls of a pattern containing a concave angle.

[0022] In a preferred embodiment of the present invention, the pattern is a regular m-sided polygon, where m is a natural number greater than 2.

[0023] In a preferred embodiment of the invention, the pattern is a 4n-sided polygon containing a reference shape that is a regular n-sided polygon and includes n vertices among the vertices of the pattern. It also includes first line segments extending from each of the n vertices and second line segments adjacent to the first line segments but not extending from any of the n vertices, where n is a natural number greater than 2. The angle between two adjacent first line segments in the pattern is constant and equal to the angle between two adjacent second line segments in the pattern. Thus, the invention can adjust the probability of dislocation introduction into the growth layer in the substrate and the mechanical strength of the substrate based on the setting of the angle.

[0024] In a preferred embodiment of the invention, the pattern includes a third line segment for connecting the centroid of the reference pattern and the intersection of two adjacent second line segments.

[0025] The present invention is a method for suppressing the introduction of dislocations into an aluminum nitride growth layer, comprising a processing step of removing a portion of the silicon carbide substrate and forming a pattern containing a convex angle before forming an aluminum nitride growth layer on the silicon carbide substrate.

[0026] The effects of the invention

[0027] According to the disclosed technology, a novel technique can be provided that can suppress the introduction of dislocations into the aluminum nitride growth layer.

[0028] Other issues, features, and advantages will become apparent from reading the embodiments of the invention described below, in conjunction with the accompanying drawings and claims. Attached Figure Description

[0029] Figure 1 This is an explanatory diagram illustrating the steps of a method for manufacturing an aluminum nitride substrate according to an embodiment.

[0030] Figure 2 This is an explanatory diagram illustrating the steps of a method for manufacturing an aluminum nitride substrate according to an embodiment.

[0031] Figure 3 This is an explanatory diagram illustrating the crystal growth steps according to the embodiment.

[0032] Figure 4 This is an explanatory diagram of the pattern according to the implementation method.

[0033] Figure 5 This is an explanatory diagram of the pattern according to Example 1.

[0034] Figure 6 This is an explanatory diagram of the strain layer removal steps according to Example 1.

[0035] Figure 7 This is an explanatory diagram of the crystal growth steps according to Example 1.

[0036] Figure 8 The results are based on Raman spectrophotometry measurements of the growth layer 20 in Example 1.

[0037] Figure 9 This is an observation image of the pad portion after KOH etching according to Example 1.

[0038] Figure 10 This is an observation image of the wing after KOH etching according to Example 1.

[0039] Figure 11 This is an observation image of the substrate 10 according to Example 2.

[0040] Figure 12 This is an observation image of the growth layer 20 after KOH etching according to Example 2.

[0041] Figure 13 These are observation images based on the substrate 10 of the comparative example.

[0042] Figure 14 This is an observation image of the growth layer 20 after KOH etching, based on the comparative example. Detailed Implementation

[0043] The preferred embodiment of the method for manufacturing an aluminum nitride substrate according to the present invention will be described in detail below with reference to the accompanying drawings.

[0044] The technical scope of this invention is not limited to the embodiments shown in the accompanying drawings, and can be appropriately modified within the scope of the claims.

[0045] The accompanying drawings in this specification are conceptual diagrams, and the relative dimensions of the components do not limit the invention.

[0046] In this specification, the terms "up" and "down" may be used to refer to "up" or "down" based on the accompanying drawings for the purpose of explaining the present invention, but this is not a limitation on the relationship between "up" and "down" in terms of the use of the aluminum nitride substrate of the present invention.

[0047] Furthermore, in the following description and accompanying drawings of the embodiments, the same reference numerals are used for the same structures, and repeated descriptions are omitted.

[0048] Manufacturing Method of Aluminum Nitride Substrates

[0049] Figure 1 and Figure 2 The steps of a method for manufacturing an aluminum nitride substrate according to an embodiment are shown.

[0050] The method for manufacturing an aluminum nitride substrate according to the embodiment includes a processing step S10 of removing a portion of a base substrate 10 and forming a pattern 100 containing a concave angle, and a crystal growth step S20 of forming a growth layer 20 on the base substrate 10 on which the pattern 100 is formed.

[0051] In addition, the processing step S10 according to the embodiment can be understood, for example, as a brittle processing step for reducing the strength of the substrate 10.

[0052] Furthermore, this embodiment can be understood as a method for suppressing the introduction of dislocations into the growth layer 20 by including a processing step of removing a portion of the substrate 10 and forming a pattern containing inferior angles before forming the growth layer 20 on the substrate 10.

[0053] The following is a detailed description of each step of the implementation method.

[0054] <Processing Step S10>

[0055] Processing step S10 is a step of removing a portion of the substrate 10 to form a pattern 100 containing a concave corner.

[0056] Furthermore, processing step S10 can be understood as the step of removing a portion of the substrate 10 and forming a pattern 100 as a periodic arrangement pattern.

[0057] In addition, "removing a portion of the substrate 10" as described in this specification means removing at least the portion of the substrate 10, including the surface layer, by methods such as those described later.

[0058] In this specification, "minor angle" refers to an acute or obtuse angle less than 180°. Additionally, "pattern 100 containing a minor angle" in this specification means a pattern 100 in which at least one of the angles constituting pattern 100 is a minor angle.

[0059] According to the processing step S10 of the embodiment, a through hole 11 is formed on the substrate 10, thereby facilitating the formation of a temperature gradient in the a-axis direction. This allows crystal growth along the a-axis direction, driven by this temperature gradient.

[0060] Furthermore, processing step S10 can also be a structure that replaces the through hole 11 or forms a recess in addition to the through hole 11. In this case, processing step S10 processes the surface of the substrate 10 into a mesa shape.

[0061] like Figure 2 As shown, the processing step S10 according to the embodiment includes a through-hole forming step S11, which forms a through-hole 11 on the substrate 10, and a strain layer removal step S12, which removes the strain layer 12 introduced through the through-hole forming step S11.

[0062] The substrate 10 can be any material commonly used in the manufacture of aluminum nitride substrates.

[0063] The substrate 10 is made of known group IV materials such as silicon (Si), germanium (Ge), and diamond (C).

[0064] Furthermore, the material of the substrate 10 is, for example, a known group IV-IV compound material such as SiC.

[0065] In addition, the substrate 10 is made of known II-VI compound materials such as zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenide (ZnSe), cadmium sulfide (CdS), and cadmium telluride (CdTe).

[0066] Furthermore, the substrate 10 is made of known III-V compound materials such as boron nitride (BN), gallium arsenide (GaAs), gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), gallium phosphide (GaP), indium phosphide (InP), and indium antimonide (InSb).

[0067] Furthermore, the material of the substrate 10 is, for example, an oxide material such as aluminum oxide (Al2O3) or gallium oxide (Ga2O3).

[0068] In addition, the material of the substrate 10 is, for example, a metal such as copper (Cu) or nickel (Ni).

[0069] Alternatively, the substrate 10 may also be a structure with known added atoms appropriately added according to its material.

[0070] In addition, the substrate 10 can be a wafer or substrate processed from bulk crystal, or a substrate including a growth layer formed by epitaxial growth.

[0071] <Step S11 for forming a through hole>

[0072] The through-hole forming step S11 is a step of removing a portion of the substrate 10 and forming the through-hole 11. As this through-hole forming step S11, a means of forming the through-hole 11 by irradiating the substrate 10 with a laser L can be illustrated.

[0073] At this time, the through-hole forming step S11 forms the through-hole 11 by scanning the focus of the laser L from the surface (equivalent to the upper surface) of the substrate 10 to the bottom surface (equivalent to the lower surface).

[0074] Furthermore, in the through-hole forming step S11, the laser L is irradiated onto the substrate 10 while the laser L is scanning along the in-plane direction of the substrate 10.

[0075] Furthermore, in the through-hole forming step S11, as a means of forming the through-hole 11 on the substrate 10, a known ion beam (equivalent to FIB processing) can be used to irradiate the substrate 10, instead of irradiating the substrate 10 with a laser L.

[0076] At this point, the ion species of the aforementioned ion beam can be obtained from Ga + Appropriately select from known ion species. Alternatively, in the through-hole formation step S11, the ion beam can be extracted from a known ion source such as a raw material gas or a liquid metal ion source while an appropriate accelerating voltage is applied.

[0077] Furthermore, as a means of forming the through hole 11 on the substrate 10, the through hole forming step S11 can be replaced by known dry etching (equivalent to plasma etching) such as patterning a hard mask on the substrate 10 and performing Deep-RIE (deep reactive ion etching) on ​​the substrate 10 with the hard mask, instead of irradiating the substrate 10 with laser L.

[0078] At this point, the material of the aforementioned hard mask can be determined from the material of the substrate 10, specifically from SiN. X Appropriate materials can be selected from known sources. Additionally, the etchant used in dry etching can be appropriately selected from known gases such as SF6, depending on the material of the substrate 10.

[0079] <Strain layer removal step S12>

[0080] The strain layer removal step S12 is a step of removing the strain layer 12 formed on the substrate 10 through the through hole forming step S11.

[0081] Furthermore, the strain layer removal step S12 can be performed by etching the substrate 10 through heat treatment.

[0082] Furthermore, the strain layer removal step S12 can employ a means capable of removing the strain layer 12.

[0083] Furthermore, the strain layer removal step S12 is preferably performed by thermal etching to remove the strain layer 12.

[0084] Ideally, the through-hole formation step S11 and the strain layer removal step S12 shall employ methods suitable for the substrate 10 material.

[0085] For example, if the substrate 10 is SiC, it is desirable to use a method of etching the substrate 10 in a Si atmosphere for the strain layer removal step S12.

[0086] Furthermore, for example, if the substrate 10 is SiC, the strain layer removal step S12 can also be a structure using a method of etching the substrate 10 under a hydrogen atmosphere.

[0087] <Crystal growth step S20>

[0088] The crystal growth step S20 is the step of forming a growth layer 20 on the substrate 10 after the processing step S10.

[0089] The material of the growth layer 20 can be the same as that of the substrate 10 (equivalent to homoepitaxial growth) or a different material from that of the substrate 10 (equivalent to heteroepitaxial growth).

[0090] The material of growth layer 20 can also be a material that is typically used for epitaxial growth.

[0091] Furthermore, the material of the growth layer 20 can be the material of the substrate 10, a known material that can be used as the material of the substrate 10, or a known material that can be epitaxially grown on the substrate 10.

[0092] The substrate 10 and the growth layer 20 are made of materials such as SiC and AlN, respectively. In other words, the substrate 10 is a silicon carbide (SiC) substrate, and the growth layer 20 is an aluminum nitride (AlN) layer.

[0093] Furthermore, the crystal growth step S20 is preferably a step of forming the growth layer 20 based on the physical vapor transport (PVT) method.

[0094] As a growth method for the growth layer 20, the crystal growth step S20 can employ known vapor phase growth methods (equivalent to vapor phase epitaxy) such as PVT, sublimation recrystallization, modified Rayleigh method, and chemical vapor transport (CVT).

[0095] Alternatively, the crystal growth step S20 can be replaced by physical vapor deposition (PVD) instead of chemical vapor deposition (CVD).

[0096] In addition, as a growth method for the growth layer 20, the crystal growth step S20 can employ known liquid phase growth methods (equivalent to liquid phase epitaxy) such as the TSSG method (Top-Seeded Solution Growth) and the Metastable Solvent Epitaxy (MSE).

[0097] Furthermore, as a growth method for the growth layer 20, the crystal growth step S20 can employ the CZ method (Czochralski method, Czochralski method).

[0098] The crystal growth step S20 can be selected and a suitable growth method can be adopted according to the materials of the substrate 10 and the growth layer 20 respectively.

[0099] like Figure 3 As shown, the crystal growth step S20 according to the embodiment is a step of placing the substrate 10 and the semiconductor material 40, which becomes the raw material for the growth layer 20, opposite to each other in a crucible 30 having a quasi-enclosed space and heating them.

[0100] In addition, the term "quasi-closed space" in this specification refers to a space that, although capable of being evacuated, can contain at least a portion of the vapor generated inside the container.

[0101] By heating the crucible 30 (substrate 10 and semiconductor material 40), the raw material is transported from the semiconductor material 40 to the substrate 10 through the raw material transport space 31.

[0102] Furthermore, a temperature gradient can be used in the crystal growth step S20 as a driving force for transporting raw materials between the substrate 10 and the semiconductor material 40.

[0103] Here, in the crystal growth step S20, vapor composed of atomic species sublimated from semiconductor material 40 is transported by diffusion in raw material transport space 31 and reaches supersaturation and condenses on substrate 10 where the temperature is set lower than that of semiconductor material 40.

[0104] Furthermore, as the driving force mentioned above, the crystal growth step S20 can utilize the chemical potential difference between the substrate 10 and the semiconductor material 40.

[0105] Here, in the crystal growth step S20, vapor composed of atomic species sublimated from semiconductor material 40 is transported by diffusion in raw material transport space 31 and reaches supersaturation and condenses on substrate 10 with a chemical potential lower than that of semiconductor material 40.

[0106] Furthermore, the crystal growth step S20 involves forming the pad portion 21 by performing crystal growth from the substrate 10 along the c-axis direction (equivalent to c-axis dominant growth), forming the wing portion 22 by performing crystal growth from the pad portion 21 along the a-axis direction (equivalent to a-axis dominant growth), and forming the growth layer 20. Additionally, a-axis dominant growth may include crystal growth along the a-axis direction from the side surface of the through-hole 11 or the side surface of the recess.

[0107] Additionally, the growth layer 20 includes a pad portion 21 and a wing portion 22. According to the embodiment, the through-hole 11 or recess is located directly below the wing portion 22.

[0108] The “c-axis dominant growth” and “a-axis dominant growth” described in this specification can be appropriately controlled based on the heating conditions in crystal growth step S20.

[0109] The heating conditions described above are, for example, temperature gradients along the c-axis and a-axis, and may include their history. This history corresponds to the shift or change of the temperature gradient during heating.

[0110] Furthermore, the aforementioned heating conditions are, for example, the back pressure or partial pressure of an inert gas containing nitrogen, and may include its history. This history corresponds to the shift or change in back pressure, etc., during heating.

[0111] Furthermore, the aforementioned heating conditions are, for example, heating temperatures, and may include their history. This history corresponds to the shift or change in heating temperatures, etc., during the heating process.

[0112] Alternatively, the crystal growth step S20 can also switch between c-axis dominant growth and a-axis dominant growth, for example, based on the conditions or methods described by D. Dojima et al. in Journal of Crystal Growth, 483, 206 (2018).

[0113] Alternatively, the doping concentration of the growth layer 20 can be adjusted in the crystal growth step S20 by using a doping gas. Alternatively, the doping concentration of the growth layer 20 can be adjusted in the crystal growth step S20 by using a semiconductor material 40 with a different doping concentration than the substrate 10.

[0114] Furthermore, the crystal growth step S20 is a step of performing a zipper-like bonding on the substrate 10 to form a growth layer 20.

[0115] Furthermore, the zipper-type joint is equivalent to joining the crystal growth surfaces along the center line that divides the adjacent sides of pattern 100 at equal angles.

[0116] Here, it can be understood that in a zipper-type joint, the joint between the crystal growth surfaces is gradually carried out from the location corresponding to the intersection of the two sides mentioned above.

[0117] Furthermore, it can be understood that in a zipper-type joint, for example, the joint area between crystal growth surfaces gradually expands from the area where the crystal growth surfaces are joined.

[0118] In addition, the crystal growth step S20 is preferably a step of forming the growth layer 20 using a substrate 10 having a pattern 100 that produces a zipper-like bond.

[0119] Here, the pattern 100 that produces a zipper-like joint refers to, for example, a pattern 100 in which the angle θ is set to increase the area.

[0120] Figure 4 This is an explanatory diagram illustrating pattern 100 according to an embodiment.

[0121] The line segment represented by pattern 100 is the substrate 10. In addition, the width of the line segment is not limited.

[0122] Pattern 100 preferably includes a concave angle.

[0123] Furthermore, pattern 100 can also be a structure formed by arranging predetermined patterns periodically. Additionally, pattern 100 can also be a structure formed by arranging the predetermined pattern and patterns obtained by flipping or rotating the predetermined pattern.

[0124] Furthermore, pattern 100 includes, for example, a regular m-sided polygon. In this case, m is a natural number greater than 2. m is, for example, 3 or 6.

[0125] Furthermore, pattern 100 includes, for example, a cubically symmetric regular hexagonal displacement shape. See below for reference. Figure 4 The "regular hexagonal displacement shape" in this specification will be described in detail.

[0126] The displacement form of a regular hexagon is a dodecagon. Furthermore, the displacement form of a regular hexagon consists of 12 line segments of equal length that are straight lines.

[0127] The pattern 100, which presents a regular hexagonal displacement shape, contains a reference shape 101 that is an equilateral triangle with an area and includes three vertices 104. These three vertices 104 are included in the vertices of the pattern 100. Here, it can be understood that the three vertices 104 are located on the line segments constituting the pattern 100.

[0128] Pattern 100 includes: a line segment 102 (equivalent to a first line segment) that extends from and includes vertex 104, and a line segment 103 (equivalent to a second line segment) that does not extend from and does not include vertex 104 and is adjacent to line segment 102.

[0129] Here, the angle θ between two adjacent line segments 102 in pattern 100 is constant and equal to the angle θ between two adjacent line segments 103 in pattern 100.

[0130] In addition, the term "displaced regular hexagon" in this specification can be understood as a dodecagon formed by displacing (deforming) a regular hexagon based on an angle θ representing the degree of concavity or convexity while maintaining the area of ​​the regular hexagon.

[0131] The angle θ is preferably greater than 60°, more preferably 66° or more, more preferably 80° or more, more preferably 83° or more, more preferably 120° or more, more preferably 150° or more, and more preferably 155° or more.

[0132] Furthermore, the angle θ is preferably 180° or less, more preferably 155° or less, more preferably 150° or less, more preferably 120° or less, more preferably 83° or less, more preferably 80° or less, and more preferably 66° or less.

[0133] According to the embodiment, pattern 100 can also be a six-fold symmetrical regular dodecagonal displacement shape, instead of a three-fold symmetrical regular hexagonal displacement shape.

[0134] The displacement form of a regular dodecagon is a 24-sided polygon. Furthermore, the displacement form of a regular dodecagon consists of 24 line segments of equal length that are straight.

[0135] The pattern 100, which presents a displacement shape of a regular dodecagon, contains a reference shape 101 that is a regular hexagon with an area and includes six vertices 104. These six vertices 104 are included in the vertices of the pattern 100. Furthermore, the area of ​​this regular hexagon can be equal to or different from the area of ​​the aforementioned equilateral triangle.

[0136] In addition, similar to the regular hexagonal displacement form, the angle θ between two adjacent line segments 102 in pattern 100 of the regular dodecagonal displacement form is constant and equal to the angle θ between two adjacent line segments 103 in pattern 100.

[0137] In other words, the "displaced regular dodecagon" in this specification can be understood as a 24-sided polygon formed by displacing (deforming) a regular dodecagon based on an angle θ representing the degree of concavity or convexity while maintaining the area of ​​the regular dodecagon.

[0138] Furthermore, in pattern 100, the regular 2n-gon is transformed into a 4n-gon by displacement (deformation) based on an angle θ representing the degree of concavity or convexity, while maintaining the area of ​​the regular 2n-gon; that is, a 2n-gon displacement form. Here, a regular n-gon can be understood as having n vertices. Additionally, when the angle θ = 180°, the regular 2n-gon displacement form becomes a regular 2n-gon.

[0139] At this point, it can be understood that the 2n-sided displacement shape contains a regular n-sided shape (equivalent to the reference figure 101).

[0140] The pattern 100 according to the embodiment may also be a structure including a regular 2n-sided displacement shape (including a regular hexagonal displacement shape and a regular 12-sided displacement shape).

[0141] In addition, pattern 100 may also include at least one line segment (equivalent to a third line segment) in addition to the line segments that constitute the displacement shape of the regular 2n-gon, for connecting the centroid of the reference pattern 101 and the intersection of two adjacent line segments 103 in the displacement shape of the regular 2n-gon.

[0142] In addition, pattern 100 may also include, besides the line segments constituting the displacement shape of the regular 2n-gon, at least one line segment for connecting the intersection of the vertex 104 constituting the reference pattern 101 and two adjacent line segments 103 in the displacement shape of the regular 2n-gon.

[0143] In addition, pattern 100 may also include at least one line segment constituting the reference pattern 101 included in the regular 2n-gon displacement shape, in addition to the line segments constituting the displacement shape of the regular 2n-gon.

[0144] The present invention will be described in more detail by providing examples 1, 2, and comparative examples.

[0145] Example 1 illustrates an embodiment in which an AlN layer is formed as a growth layer 20 on a SiC substrate 10. The substrate 10 according to Example 1 has a pattern 100 including a concave angle and including the above-described regular hexagonal deformation.

[0146] Example 2 illustrates an embodiment in which an AlN layer is formed as a growth layer 20 on a substrate 10 that is a SiC substrate. The substrate 10 according to Example 2 has a pattern 100 that includes a concave angle and includes equilateral triangular deformations.

[0147] The comparative example illustrates an embodiment in which a growth layer 20, serving as an AlN layer, is formed on a substrate 10, which is a SiC substrate. The substrate 10 according to the comparative example has a pattern 100 that does not contain obtuse angles.

[0148] Example 1

[0149] Hereinafter, Example 1 will be described in detail.

[0150] <Processing Steps>

[0151] According to Example 1, processing step S10 is a step of removing a portion of the substrate 10 and forming a pattern 100 containing a concave corner under the following conditions.

[0152] (Substrate 10)

[0153] Semiconductor material: 4H-SiC

[0154] Substrate dimensions: 10mm wide × 10mm long × 524μm thick

[0155] Growth surface: Si surface

[0156] Offset angle: coaxial

[0157] <Step S11 for forming a through hole>

[0158] According to Example 1, the through-hole forming step S11 is the step of irradiating the substrate 10 with laser L to form the through-hole 11.

[0159] (Laser processing conditions)

[0160] Wavelength: 532nm

[0161] Output power: 3W / cm 2

[0162] Spot diameter: 40μm

[0163] (Details of the pattern)

[0164] Figure 5 This is an explanatory diagram illustrating the pattern 100 of the through-hole 11 formed in step S11 of the through-hole formation according to Embodiment 1. The black area shows a portion of the through-hole 11, and the white area is reserved as the substrate 10.

[0165] In addition, it can be understood as, Figure 5 The illustrated pattern 100 is a regular hexagonal displacement shape with an angle θ = 80°, and includes line segments for connecting the intersection of two adjacent line segments 103 to the centroid of the reference pattern 101.

[0166] Here, the pattern 100 according to Embodiment 1 has a width of approximately 100 μm.

[0167] (Strain layer removal step S12)

[0168] According to Example 1, the strain layer removal step S12 is a step of removing the strain layer 12 formed on the substrate 10 through the through-hole forming step S11 by thermal etching.

[0169] Figure 6 This is an explanatory diagram illustrating the strain layer removal step S12 according to Example 1. According to the strain layer removal step S12 of Example 1, the substrate 10 is housed in a SiC container 50, and the SiC container 50 is further housed in a TaC container 60 and heated.

[0170] (SiC container 50)

[0171] Material: Polycrystalline SiC

[0172] Container dimensions: 60mm in diameter × 4mm in height

[0173] Distance between the substrate 10 and the bottom surface of the SiC container 50: 2mm

[0174] (Details of SiC container 50)

[0175] like Figure 6 As shown, the SiC container 50 is a fitted container that includes an upper container 51 and a lower container 52 that can fit together.

[0176] A tiny gap 53 is formed at the fitting part of the upper container 51 and the lower container 52, which enables the venting (vacuuming) of the SiC container 50 through the gap 53.

[0177] The SiC container 50 has an etch space 54 formed by placing a portion of the SiC container 50 disposed on the low-temperature side of the temperature gradient opposite to the substrate 10 while the substrate 10 is disposed on the high-temperature side of the temperature gradient.

[0178] The etching space 54 is a space in which Si atoms and C atoms are transported from the substrate 10 to the SiC container 50 and etched using the temperature difference between the substrate 10 and the bottom surface of the SiC container 50 as the driving force.

[0179] In addition, the SiC container 50 has a substrate holder 55 for holding the substrate 10 in mid-air and forming an etch space 54.

[0180] Alternatively, the SiC container 50 may be designed without a substrate holder 55, depending on the direction of the temperature gradient of the furnace.

[0181] For example, in the case where a temperature gradient is formed in the heating furnace so that the temperature drops from the lower container 52 to the upper container 51, the SiC container 50 may also have a substrate 10 disposed on the bottom surface of the lower container 52 without a substrate holder 55.

[0182] (TaC container 60)

[0183] Materials: TaC

[0184] Container dimensions: 160mm in diameter × 60mm in height

[0185] Si vapor supply source 64 (Si compound): TaSi2

[0186] (Details of TaC container 60)

[0187] Similar to the SiC container 50, the TaC container 60 is a fitted container including an upper container 61 and a lower container 62 that can fit together, and is configured to accommodate the SiC container 50.

[0188] A tiny gap 63 is formed at the fitting part of the upper container 61 and the lower container 62, which enables the TaC container 60 to be vented (vacuumed) through the gap 63.

[0189] The TaC container 60 has a Si vapor supply source 64 capable of supplying a vapor pressure of gaseous species containing Si within the TaC container 60.

[0190] The Si vapor supply source 64 can be any structure that generates a vapor pressure of gaseous species containing Si elements within the TaC container 60 during heat treatment.

[0191] (Heating conditions)

[0192] The substrate 10 configured under the above conditions will be subjected to heat treatment under the following conditions.

[0193] Heating temperature: 1800℃

[0194] Etching depth: 8μm

[0195] In addition, the heating time and temperature gradient are appropriately set in the strain layer removal step S12 to achieve the following etching amount.

[0196] <Crystal growth step S20>

[0197] According to Example 1, the crystal growth step S20 is the step of forming a growth layer 20 on the substrate 10 after the processing step S10.

[0198] Figure 7 This is an explanatory diagram illustrating the crystal growth step S20 according to Example 1. The crystal growth step S20 according to Example 1 is a step of placing the substrate 10 in a crucible 30 so that it is opposite to the semiconductor material 40 and heating it.

[0199] (Crucible 30)

[0200] Materials: TaC

[0201] Container dimensions: 10mm × 10mm × 1.5mm

[0202] Distance between substrate 10 and semiconductor material 40: 1 mm

[0203] (Details of crucible 30)

[0204] The crucible 30 has a material delivery space 31 between the substrate 10 and the semiconductor material 40. The material is delivered from the semiconductor material 40 to the substrate 10 through the material delivery space 31.

[0205] Figure 7 (a) is an example of the crucible 30 used in the crystal growth step S20. Like the SiC container 50 and the TaC container 60, the crucible 30 is a fitted container comprising an upper container 32 and a lower container 33 that can be fitted together. A small gap 34 is formed at the fitting portion of the upper container 32 and the lower container 33, which is configured to allow venting (vacuuming) of the crucible 30 through the gap 34.

[0206] Additionally, the crucible 30 has a substrate holder 35 for forming the raw material delivery space 31. The substrate holder 35 is disposed between the base substrate 10 and the semiconductor material 40, and the semiconductor material 40 is positioned on the high-temperature side while the base substrate 10 is positioned on the low-temperature side to form the raw material delivery space 31.

[0207] Figure 7 (b) and Figure 7 (c) is another example of the crucible 30 used in the crystal growth step S20. Figure 7 (b) and Figure 7 The temperature gradient of (c) is set to be similar to... Figure 7 The temperature gradient is opposite to that of (a), and the substrate 10 is disposed on the upper side. That is, with Figure 7 Similar to (a), a material delivery space 31 is formed by placing semiconductor material 40 on the high-temperature side and substrate 10 on the low-temperature side.

[0208] Figure 7 (b) shows an example of forming a material delivery space 31 between the substrate 10 and the semiconductor material 40 by fixing the substrate 10 to the side of the upper container 32.

[0209] Figure 7 (c) shows an example of forming a material delivery space 31 between the upper container 32 and the semiconductor material 40 by forming a through window at the upper container 32 and configuring the substrate 10 thereon. Furthermore, as shown in the diagram... Figure 7 As shown in (c), the raw material conveying space 31 can also be formed by setting an intermediate component 36 between the upper container 32 and the lower container 33.

[0210] Alternatively, the material of crucible 30 can be a high-melting-point material such as W (tungsten) instead of TaC.

[0211] (Semiconductor Materials 40)

[0212] Material: AlN sintered body

[0213] Dimensions: 20mm wide x 20mm long x 5mm thick

[0214] (Details of semiconductor material 40)

[0215] The AlN sintered body of semiconductor material 40 is manufactured in the following sequence.

[0216] First, in Example 1, AlN powder was placed inside a TaC block. Then, in Example 1, the AlN powder was compacted by mechanically applying external force. Next, in Example 1, the compacted AlN powder and TaC block were placed in a thermally decomposable carbon crucible and heated under the following conditions.

[0217] In the crystal growth step S20, the substrate 10 and the semiconductor material 40 are arranged in the crucible 30 and heated under the following heating conditions.

[0218] (Heating conditions)

[0219] Heating temperature: 2040℃

[0220] Heating time: 70 hours

[0221] Growth thickness: 500 μm

[0222] Temperature gradient: 6.7K / mm

[0223] N2 gas pressure: 10 kPa

[0224] Figure 8 The graph depicts the full half-width (FWHM) of the E2 peak obtained by Raman spectroscopy for the growth layer 20 formed under the above conditions.

[0225] according to Figure 8 It is understood that an AlN layer with poor crystallinity is formed in the pad portion 21, while an AlN layer with good crystallinity is formed in the wing portion 22. It is also understood that the pad portion 21 corresponds to a line segment of pattern 100.

[0226] Figure 9 This is a surface SEM image obtained by revealing the dislocations in the pad portion 21 of the growth layer 20 formed under the above conditions through an etching pit method. This etching pit method is performed using KOH wet etching.

[0227] according to Figure 9 It is understood that the pad portion 21 according to Embodiment 1 has a size of 1.5 × 10. 8 cm -2 The dislocation density (equivalent to the etch pit density).

[0228] Figure 10This is a SEM image of the surface obtained by using the above-described etching pit method to expose the dislocations of the wing 22 of the growth layer 20 formed under the above conditions. The etching pit method is performed based on KOH wet etching.

[0229] according to Figure 10 It is understood that the wing 22 according to Embodiment 1 has a size of 1.2 × 10⁻⁶. 6 cm -2 The dislocation density (equivalent to the etch pit density).

[0230] according to Figure 9 and Figure 10 It is understood that the introduction of dislocations toward the wings 22 is suppressed during the formation of the growth layer 20 on the substrate 10.

[0231] Example 2

[0232] Hereinafter, Example 2 will be described in detail. Furthermore, descriptions of structures and conditions common to Example 1 and the embodiments are omitted in this specification.

[0233] According to Example 2, the substrate 10 has a recess instead of a through hole 11.

[0234] The pattern 100 according to Embodiment 2 includes an equilateral triangle. Here, the line segments constituting the pattern 100 have a width of ~60 μm.

[0235] Figure 11 The image is an SEM image of the substrate 10 after processing step S10 according to Example 2.

[0236] In the crystal growth step S20, the substrate 10 and the semiconductor material 40 are arranged in the crucible 30 and heated under the following heating conditions.

[0237] (Heating conditions)

[0238] Heating temperature: 1840℃

[0239] N2 gas pressure: 50 kPa

[0240] Figure 12 The observation image is obtained by SEM observation of the surface of the growth layer 20 formed under the above conditions, which is obtained by using the etch pit method to expose the dislocations of the growth layer 20. The etch pit method is performed based on KOH wet etching.

[0241] according to Figure 12 This can be understood as the introduction of dislocations toward the wings 22 being suppressed during the formation of the growth layer 20 on the substrate 10 having a pattern 100 containing inferior angles.

[0242] Comparative Examples

[0243] The comparative examples will now be described in detail. Furthermore, descriptions of structures and conditions common to Example 1 and the embodiments have been omitted from this specification.

[0244] The substrate 10 of the comparative example has a recess instead of a through hole 11, just like in Example 2.

[0245] The pattern 100 according to the comparative example does not contain inferior angles or intersections. The line segments used to form the pattern 100 according to the comparative example are parallel to each other. Here, the line segments forming the pattern 100 have a width of ~60 μm.

[0246] Figure 13 The image is a SEM image of the substrate 10 after processing step S10 according to the comparative example.

[0247] In the crystal growth step S20, the substrate 10 and the semiconductor material 40 are arranged in the crucible 30 and heated under the following heating conditions.

[0248] (Heating conditions)

[0249] Heating temperature: 1840℃

[0250] N2 gas pressure: 50 kPa

[0251] Figure 14 The observation image is obtained by SEM observation of the surface of the growth layer 20 formed under the above conditions, which is obtained by using the etch pit method to expose the dislocations of the growth layer 20. The etch pit method is performed based on KOH wet etching.

[0252] according to Figure 14 This can be understood as the formation of the growth layer 20 on a substrate 10 having a pattern 100 that does not contain inferior corners, especially in Figure 14 In the central part of the wing 22 (equivalent to the junction of the crystal growth surface), dislocations were introduced into the wing 22.

[0253] In addition, according to Figure 12 and Figure 14 It is understood that, compared to Comparative Example 1, the bonding region (equivalent to) of the crystal growth surface in the wing 22 of Example 2 is different. Figure 12 and Figure 14 The dislocation density in the central region of the wing 22 is suppressed to a low level.

[0254] Understandable, Figure 12 In the a-axis dominant growth, since the crystal growth surface bonding in the formation of growth layer 20 is carried out in the form of zipper bonding, the introduction of new dislocations caused by the bonding of the crystal growth surface is suppressed.

[0255] According to the present invention, by a processing step S10 including removing a portion of the substrate 10 and forming a pattern 100 containing a convex angle, and a crystal growth step S20 including forming a growth layer 20 on the substrate 10 on which the pattern 100 is formed, the introduction of dislocations into the growth layer 20 can be suppressed.

[0256] Explanation of reference numerals in the attached figures

[0257] 10. Substrate

[0258] 11 Through Holes

[0259] 12 Strain Layer

[0260] 20 growth layers

[0261] 21. Solder pad section

[0262] 22 Wings

[0263] 30 crucibles

[0264] 31 Raw material conveying space

[0265] 40 Semiconductor Materials

[0266] 50 SiC container

[0267] 60 TaC containers

[0268] S10 Processing Steps

[0269] S11 Through Hole Formation Steps

[0270] S12 Strain Layer Removal Steps

[0271] S20 crystal growth steps

Claims

1. A method for manufacturing an aluminum nitride substrate, comprising a processing step of removing a portion of a silicon carbide substrate and forming a pattern including a convex corner, and a crystal growth step of forming an aluminum nitride growth layer on the silicon carbide substrate having the pattern formed. The processing steps include a through-hole forming step that removes a portion of the silicon carbide substrate to form a through-hole, and a strain layer removal step that removes the strain layer introduced by the through-hole forming step.

2. The method for manufacturing an aluminum nitride substrate according to claim 1, wherein, The crystal growth step includes zipper bonding on the silicon carbide substrate to form the aluminum nitride growth layer.

3. The method for manufacturing an aluminum nitride substrate according to claim 1, wherein, The crystal growth step forms the aluminum nitride growth layer by crystal growth along the c-axis and crystal growth along the a-axis.

4. The method for manufacturing an aluminum nitride substrate according to claim 1, wherein, The crystal growth step is a step performed using physical vapor transport.

5. The method for manufacturing an aluminum nitride substrate according to claim 1, wherein, The through-hole forming step is a step of forming through-holes by irradiating the silicon carbide substrate with a laser.

6. The method for manufacturing an aluminum nitride substrate according to claim 1, wherein, The strain layer removal step is a step of removing the strain layer of the silicon carbide substrate by performing heat treatment.

7. The method for manufacturing an aluminum nitride substrate according to claim 1, wherein, The silicon carbide substrate is silicon carbide, and the strain layer removal step is a step of etching the silicon carbide substrate in a silicon atmosphere.

8. The method for manufacturing an aluminum nitride substrate according to claim 1, wherein, The pattern comprises a regular m-sided polygon, where m is a natural number greater than 2.

9. A method for manufacturing an aluminum nitride substrate, wherein, The process includes a processing step of removing a portion of a silicon carbide substrate and forming a pattern containing a convex corner, and a crystal growth step of forming an aluminum nitride growth layer on the silicon carbide substrate with the pattern formed. The pattern comprises a 4n-sided polygon containing a reference figure consisting of n vertices included in the vertices of the pattern as a regular n-sided polygon, and comprising a first line segment extending from each of the n vertices and a second line segment adjacent to the first line segment but not extending from any of the n vertices, where n is a natural number greater than 2, and the angle between two adjacent first line segments in the pattern is constant and equal to the angle between two adjacent second line segments in the pattern.

10. The method for manufacturing an aluminum nitride substrate according to claim 9, wherein, The pattern includes a third line segment connecting the centroid of the reference figure to the intersection of two adjacent second line segments.

11. An aluminum nitride substrate, manufactured by the manufacturing method according to any one of claims 1 to 10.

12. A method for suppressing the introduction of dislocations into an aluminum nitride growth layer, comprising a processing step of removing a portion of the silicon carbide substrate and forming a pattern including a convex corner before forming an aluminum nitride growth layer on a silicon carbide substrate. The processing steps include a through-hole forming step that removes a portion of the silicon carbide substrate to form a through-hole, and a strain layer removal step that removes the strain layer introduced by the through-hole forming step.

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