Method for manufacturing an aluminum nitride substrate, aluminum nitride substrate, and method for forming an aluminum nitride layer

Abstract

The problem to be solved by the present invention is to provide a novel technology capable of manufacturing a large-diameter AIN substrate. The present invention pertains to a method for manufacturing an AIN substrate, the method including a crystal growth step S30 for forming an AIN layer 20 on a SiC base substrate 10 having a through-hole 11. Furthermore, the present invention pertains to a method for manufacturing the AIN layer 20, the method including a through-hole formation step S10 for forming the through-hole 11 in the SiC base substrate 10 before forming the AIN layer 20 on the surface of the SiC base substrate 10.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an aluminum nitride substrate, an aluminum nitride substrate, and a method for forming an aluminum nitride layer. [Background technology]

[0002] Generally, semiconductor substrates are manufactured by growing a growth layer on a base substrate. However, it has been reported that it is difficult to obtain large-diameter semiconductor substrates depending on the composition of the semiconductor material used for crystal growth.

[0003] For example, there is the case where AlN crystal is grown by sublimation on a base substrate such as an aluminum nitride (AlN) substrate or a silicon carbide (SiC) substrate. When crystal is grown simply by sublimation, there are areas where the AlN crystal does not grow, which makes it difficult to obtain a large-diameter semiconductor substrate with good crystallinity.

[0004] In response to these problems, Patent Document 1 describes a technology known as "a method for growing AlN crystal by vapor phase growth on a seed crystal substrate placed in a crystal growth chamber within a crystal growth vessel provided within a reaction vessel, characterized in that a carbon-containing gas is supplied into the crystal growth chamber during crystal growth." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-55881 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a new technique that enables the manufacture of large-diameter AlN substrates. Another problem to be solved by the present invention is to provide a new technique that makes it possible to manufacture large-diameter AlN substrates with good crystallinity. [Means for solving the problem]

[0007] The present invention, which solves the above-mentioned problems, is a method for manufacturing an aluminum nitride substrate, which includes a crystal growth step of forming an aluminum nitride layer on a silicon carbide base substrate having through-holes.

[0008] In this way, by forming an aluminum nitride layer on a silicon carbide base substrate having through-holes, it is possible to manufacture a large-diameter aluminum nitride substrate with good crystallinity. In this way, by forming an aluminum nitride layer on a silicon carbide base substrate with through holes, it is possible to produce an aluminum nitride substrate having a diameter equivalent to that of the silicon carbide base substrate. Therefore, by using a silicon carbide base substrate with a large diameter, it is possible to obtain a large-diameter aluminum nitride substrate.

[0009] In this specification, the term "large diameter" means that an aluminum nitride layer having a larger area can be obtained compared to when an aluminum nitride layer is formed on a silicon carbide base substrate that does not have through holes.

[0010] In a preferred embodiment of the present invention, the crystal growth step is a step of heating the silicon carbide base substrate so as to form a temperature gradient along the vertical direction of the silicon carbide base substrate.

[0011] In a preferred embodiment of the present invention, the crystal growth step is a step of arranging the silicon carbide substrate and a raw material for the aluminum nitride layer so as to face each other, and heating the silicon carbide substrate and the raw material so as to form a temperature gradient between the silicon carbide substrate and the raw material.

[0012] In a preferred embodiment of the present invention, the crystal growth step comprises a lateral growth step in which the aluminum nitride layer grows horizontally on the silicon carbide base substrate, and a vertical growth step in which the aluminum nitride layer grows vertically on the silicon carbide base substrate.

[0013] In a preferred embodiment of the present invention, the method further comprises a through-hole forming step of forming through-holes in the silicon carbide base substrate, and a strained layer removing step of removing the strained layer introduced in the through-hole forming step.

[0014] In a preferred embodiment of the present invention, the through-hole forming step is a step of forming the through-hole by irradiating the silicon carbide base substrate with a laser.

[0015] In a preferred embodiment of the present invention, the strained layer removal step is a step of removing the strained layer of the silicon carbide base substrate by heat treatment.

[0016] In a preferred embodiment of the present invention, the strained layer removal step is a step of etching the silicon carbide base substrate in a silicon atmosphere.

[0017] The present invention also relates to a method for forming an aluminum nitride layer, namely, a method for forming an aluminum nitride layer that solves the above-mentioned problems, comprising a through-hole forming step of forming through-holes in a silicon carbide base substrate before forming an aluminum nitride layer on the silicon carbide base substrate.

[0018] In a preferred embodiment of the present invention, the method further comprises a strained layer removing step of removing the strained layer introduced in the through-hole forming step.

[0019] In a preferred embodiment of the present invention, the strained layer removal step is a step of etching the silicon carbide base substrate by heat treatment. [Effects of the Invention]

[0020] The disclosed technology can provide a novel technology that enables the manufacture of large-diameter AlN substrates. Furthermore, the disclosed technology can provide a novel technology that enables the manufacture of large-diameter AlN substrates with good crystallinity.

[0021] Other objects, features and advantages will become apparent from a reading of the following detailed description when taken in conjunction with the drawings and claims. [Brief explanation of the drawings]

[0022] [Figure 1] 2A to 2C are explanatory diagrams illustrating steps of a method for manufacturing an AlN substrate according to an embodiment. [Figure 2] 10A to 10C are explanatory views illustrating a through-hole forming step and a strained layer removing step according to the embodiment. [Figure 3] 10A and 10B are explanatory diagrams of a through-hole forming step according to an embodiment; [Figure 4] FIG. 2 is an explanatory diagram illustrating a crystal growth process according to an embodiment. [Figure 5] FIG. 2 is an explanatory diagram illustrating a crystal growth process according to an embodiment. [Figure 6] FIG. 3 is an explanatory view of a through-hole forming step according to the first embodiment. [Figure 7] FIG. 4 is an explanatory diagram of a strained layer removing step according to the first embodiment. [Figure 8] FIG. 2 is an explanatory diagram of a crystal growth process according to Example 1. [Figure 9] FIG. 2 is an explanatory diagram of a crystal growth process according to Example 1. [Figure 10] FIG. 2 is an explanatory diagram of a crystal growth process according to Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0023] Preferred embodiments of the AlN substrate manufacturing method according to the present invention will be described in detail below with reference to the accompanying drawings. The technical scope of the present invention is not limited to the embodiments shown in the accompanying drawings, and appropriate modifications are possible within the scope of the claims. Furthermore, the accompanying drawings are conceptual diagrams, and the relative dimensions of each component do not limit the present invention. Furthermore, in this specification, for the purpose of explaining the invention, the top and bottom may be referred to based on the top and bottom of the drawings, but this does not limit the top and bottom in relation to the use mode of the AlN substrate of the present invention. In the following description of the embodiments and the accompanying drawings, similar components are designated by the same reference numerals, and redundant explanations will be omitted.

[0024] <<Method for manufacturing aluminum nitride substrate>> 1 to 4 are explanatory diagrams illustrating steps in a method for manufacturing an AlN substrate according to an embodiment of the present invention. The manufacturing method of the AlN substrate according to the embodiment may include a through-hole forming step S10 for forming a through-hole 11 in a SiC base substrate 10, a strained layer removal step S20 for removing the strained layer 12 introduced by the through-hole forming step S10, and a crystal growth step S30 for forming an AlN layer 20 on the SiC base substrate 10 having the through-hole 11.

[0025] Furthermore, this embodiment can be understood as a method for forming a large-area AlN layer, including a through-hole formation step S10 for forming through-holes 11 in the SiC base substrate 10 before forming the AlN layer 20 on the surface of the SiC base substrate 10. Each step of the embodiment will be described in detail below.

[0026] <Through hole formation process> The through hole forming step S10 is a step of forming through holes 11 in the SiC base substrate 10. Naturally, any technique that can form through holes 11 in the SiC base substrate 10 can be used for this through hole forming step S10.

[0027] The through-holes 11 can be formed, for example, by laser processing, focused ion beam (FIB) system, reactive ion etching (RIE) or other plasma etching. Note that Fig. 2 showing this embodiment illustrates a method for forming the through-holes 11 by irradiating the SiC base substrate 10 with a laser L.

[0028] The SiC base substrate 10 may be a wafer or substrate processed from a bulk crystal, or may be a substrate having a buffer layer made of the semiconductor material described above.

[0029] The through-hole 11 may be formed in one or more shapes that reduce the strength of the SiC base substrate 10. Alternatively, a through-hole group (pattern) in which a plurality of through-holes 11 are arranged may be used.

[0030] An example of a pattern for growing a hexagonal semiconductor material will now be described in detail.

[0031] FIG. 3 is an explanatory diagram illustrating a pattern 100 according to an embodiment. The line segments shown in the pattern 100 represent the SiC substrate 10. The pattern 100 preferably has a regular hexagonal displaced shape with three-fold symmetry. The "regular hexagonal displaced shape" in the description of this specification will be explained in detail below with reference to FIG. 3. The regular hexagonal displaced shape is a dodecagon. The regular hexagonal displaced shape is composed of 12 straight line segments of equal length. The regular hexagonal displaced shape pattern 100 contains a reference figure 101 that is a regular triangle, has an area 101a, and includes three vertices 104. Each of the three vertices 104 is included in the vertices of the pattern 100. It can be understood that the three vertices 104 may be located on the line segments that constitute the pattern 100. Pattern 100 includes line segment 102 (corresponding to a first line segment) that extends from and includes vertex 104, and line segment 103 (corresponding to a second line segment) that does not extend from vertex 104 and is adjacent to line segment 102 without including vertex 104. Here, the angle θ formed by the two adjacent line segments 102 in pattern 100 is constant and equal to the angle θ formed by the two adjacent line segments 103 in pattern 100. Note that the term "regular hexagon-displaced shape" in the description herein can be understood to mean a dodecagon formed by displacing (deforming) a regular hexagon while maintaining the area of ​​the regular hexagon based on angle θ, which indicates the degree of irregularity.

[0032] The angle θ is preferably greater than 60°, and is preferably 66° or greater, and is preferably 80° or greater, and is preferably 83° or greater, and is preferably 120° or greater, and is preferably 150° or greater, and is preferably 155° or greater. The angle θ is preferably 180° or less, and is preferably 155° or less, and is preferably 150° or less, and is preferably 120° or less, and is preferably 83° or less, and is preferably 80° or less, and is preferably 66° or less.

[0033] The pattern 100 according to the embodiment may have a configuration of a displaced regular dodecagon with six-fold symmetry, instead of a displaced regular hexagon with three-fold symmetry. The displaced regular dodecagon is a 24-sided polygon. The displaced regular dodecagon is composed of 24 straight line segments of equal length. The pattern 100 having a displaced regular dodecagon contains a reference figure 101 that is a regular hexagon, has an area 101a, and includes six vertices 104. Each of the six vertices 104 is included as a vertex of the pattern 100. As with the displaced regular hexagon, the angle θ between two adjacent line segments 102 in the pattern 100 is constant and equal to the angle θ between two adjacent line segments 103 in the pattern 100. In other words, the "displaced dodecagon" in the description herein can be understood as a 24-gon obtained by displacing (deforming) a regular dodecagon while maintaining the area of ​​the regular dodecagon based on the angle θ, which indicates the degree of irregularity. Note that the pattern 100 may be configured to present a displaced dodecagon, which is a 4n-gon obtained by displacing (deforming) a regular 2n-gon while maintaining the area of ​​the regular 2n-gon based on the angle θ, which indicates the degree of irregularity. In this case, the displaced dodecagon can be understood to include a regular n-gon (corresponding to the reference figure 101) within it.

[0034] The pattern 100 according to the embodiment may include a displaced regular 2n-gon shape (including a displaced regular hexagon shape and a displaced regular dodecagon shape). The pattern 100 may further include, in addition to the line segments constituting the displaced regular 2n-gon shape, at least one line segment (corresponding to a third line segment) connecting the intersection of two adjacent line segments 103 in the displaced regular 2n-gon shape to the center of gravity of the reference figure 101. The pattern 100 may further include, in addition to the line segments constituting the displaced regular 2n-gon shape, at least one line segment connecting the intersection of two adjacent line segments 103 in the displaced regular 2n-gon shape to a vertex 104 constituting the reference figure 101. The pattern 100 may further include, in addition to the line segments constituting the displaced regular 2n-gon shape, at least one line segment constituting the reference figure 101 included in the displaced regular 2n-gon shape.

[0035] Furthermore, the through-hole forming step S10 is preferably a step of removing 50% or more of the effective area of ​​the SiC base substrate 10. More preferably, it is a step of removing 60% or more of the effective area, even more preferably, it is a step of removing 70% or more of the effective area, and even more preferably, it is a step of removing 80% or more of the effective area.

[0036] In this specification, the term "effective area" refers to the surface of the SiC base substrate 10 to which the source material adheres in the crystal growth step S30. In other words, it refers to the remaining area on the growth surface of the SiC base substrate 10 other than the area removed by the through holes 11.

[0037] <Strained layer removal process> The strained layer removal step S20 is a step of removing the strained layer 12 formed in the SiC base substrate 10 by the through-hole formation step S10. An example of this strained layer removal step S20 is a means of etching the SiC base substrate 10 by heat treating the SiC base substrate 10. Furthermore, any means capable of removing the strained layer 12 can be naturally adopted.

[0038] The strained layer 12 can be removed by, for example, a hydrogen etching method using hydrogen gas as an etching gas, a Si-Vapor Etching (SiVE) method in which heating is performed under a Si atmosphere, or an etching method described in Example 1 below.

[0039] <Crystal growth process> The crystal growth step S30 is a step of forming an AlN layer 20 on the SiC base substrate 10 in which the through-holes 11 have been formed.

[0040] The crystal growth step S30 can employ known vapor phase growth methods (corresponding to vapor phase epitaxial methods) such as physical vapor transport (PVT), sublimation recrystallization, modified Rayleigh process, chemical vapor transport (CVT), molecular-organic vapor phase epitaxy (MOVPE), and hydride vapor phase epitaxy (HVPE) as a growth method for the AlN layer 20. Note that the crystal growth step S30 can employ physical vapor deposition (PVD) instead of PVT. Note that the crystal growth step S30 can employ chemical vapor deposition (CVD) instead of CVT.

[0041] 4 and 5 are explanatory diagrams illustrating the crystal growth step S30 according to the embodiment. The crystal growth step S30 according to the embodiment is a step of arranging a SiC base substrate 10 and a semiconductor material 40, which is the raw material for the AlN layer 20, facing each other in a crucible 30 having a semi-closed space, and heating them. Note that the term "semi-closed space" as used herein refers to a space in which the container can be evacuated, but in which at least a portion of the vapor generated within the container can be contained.

[0042] Furthermore, the crystal growth step S30 is a step of heating so as to form a temperature gradient along the vertical direction of the SiC base substrate 10. By heating the crucible 30 (SiC base substrate 10 and semiconductor material 40) in this temperature gradient, the raw material is transported from the semiconductor material 40 onto the SiC base substrate 10 via the raw material transport space 31.

[0043] The driving force for transporting the source material can be the temperature gradient described above or the chemical potential difference between the SiC base substrate 10 and the semiconductor material 40 .

[0044] Specifically, within the semi-closed space, vapor consisting of elements sublimated from semiconductor material 40 is transported by diffusion within source transport space 31, and condenses in a supersaturated state onto SiC base substrate 10, which is set at a lower temperature than semiconductor material 40. As a result, AlN layer 20 is formed on SiC base substrate 10.

[0045] The crystal growth step S30 also includes a lateral growth step S31 in which the AlN layer 20 grows horizontally across the SiC base substrate 10, and a vertical growth step S32 in which the AlN layer 20 grows vertically across the SiC base substrate 10. In the lateral growth step S31, it is sufficient that the growth component in the horizontal direction is greater than the growth component in the vertical direction, and the growth component in the vertical direction may also be included (growth component: horizontal direction>vertical direction). Furthermore, the vertical growth step S32 may include a horizontal growth component as long as the vertical growth component is greater than the horizontal growth component (growth component: vertical direction>horizontal direction).

[0046] That is, as shown in FIG. 4, the lateral growth process S31 is a process in which heat escapes from the through-holes 11 in the SiC base substrate 10, forming a horizontal temperature gradient on the surface of the SiC base substrate 10, causing the AlN layer 20 to grow toward the through-holes 11.

[0047] Thereafter, when AlN layer 20 is formed on through-hole 11 in lateral growth step S31, the horizontal temperature gradient on the surface of SiC base substrate 10 decreases and disappears, and the process automatically moves to vertical growth step S32.

[0048] In this crystal growth step S30, an inert gas or a doping gas may be introduced into the source material transport space 31 to control the doping concentration and growth environment of the AlN layer 20. In addition, in the crystal growth step S30, it is preferable to introduce nitrogen gas so that the inside of the source material transport space 31 is filled with a nitrogen atmosphere during growth.

[0049] According to the present invention, a large-diameter AlN substrate can be manufactured by growing an AlN layer 20 on a SiC base substrate 10 having through-holes 11. That is, heat escapes from the region where through-holes 11 are formed, and a growth driving force acts in the horizontal direction of the SiC base substrate 10. As a result, bonding of the AlN layer 20 is promoted in the region where through-holes 11 are formed, and an AlN layer 20 having a diameter equivalent to that of the SiC base substrate 10 can be formed. Therefore, by employing a SiC base substrate 10 with a large diameter, a large-diameter AlN substrate can be obtained.

[0050] Furthermore, according to the present invention, by forming the AlN layer 20 on the region where the through holes 11 are formed, the crystallinity of the AlN layer 20 can be improved. In other words, the AlN layer 20 formed on the region where the through holes 11 are formed is not located directly on the SiC base substrate 10. Therefore, the AlN layer 20 does not inherit threading dislocations (for example, threading screw dislocations, threading edge dislocations, micropipes, etc.) present in the SiC base substrate 10, and threading dislocations in the AlN layer 20 can be reduced. [Example]

[0051] The present invention will be explained more specifically with reference to Example 1 and Comparative Example 1.

[0052] Example 1 <Through hole formation process> A laser was irradiated onto a SiC base substrate 10 under the following conditions to form through-holes 11.

[0053] (SiC base substrate 10) Semiconductor material: 4H-SiC Board size: 11mm wide x 11mm long x 524μm thick Growth aspect: Si-face Off-axis angle: on-axis

[0054] (Laser processing conditions) Type: Green laser Wavelength: 532nm Spot diameter: 40 μm Average output power: 4W (at 30kHz)

[0055] (Pattern details) 6A and 6B are explanatory diagrams illustrating the pattern of through holes 11 formed in the through hole forming step S10 according to Example 1. Fig. 6A is an explanatory diagram showing an arrangement of a plurality of through holes 11. In Fig. 6A, the black areas indicate the portions of the through holes 11, and the white areas are left as the SiC base substrate 10.

[0056] Fig. 6(b) is an explanatory diagram showing an enlarged view of the through-hole 11 in Fig. 6(a). In Fig. 6(b), the white area indicates the through-hole 11, and the black area is the SiC base substrate 10 that remains. In the pattern of FIG. 6, 80% or more of the effective area of ​​the SiC base substrate 10 is removed, reducing the strength of the SiC base substrate 10.

[0057] <Strained layer removal process S20> FIG. 7 is an explanatory diagram illustrating the strained layer removing step S20 according to the first embodiment. The SiC base substrate 10 in which the through-holes 11 were formed in the through-hole forming step S10 was housed in a SiC container 50, which was then housed in a TaC container 60 and heated under the following conditions.

[0058] (Heating conditions) Heating temperature: 1800℃ Heating time: 2h Etching amount: 8 μm

[0059] (SiC container 50) Material: Polycrystalline SiC Container size: diameter 60mm x height 4mm Distance between the SiC substrate 10 and the bottom of the SiC container 50: 2 mm

[0060] (Details of the SiC container 50) 5, the SiC container 50 is a fitting container having an upper container 51 and a lower container 52 that can fit together. A minute gap 53 is formed at the fitting portion between the upper container 51 and the lower container 52, and the SiC container 50 is configured so that the inside of the SiC container 50 can be evacuated (vacuumed) through this gap 53.

[0061] SiC container 50 has etching space 54 formed by arranging a part of SiC container 50 located on the low temperature side of the temperature gradient opposite SiC base substrate 10, with SiC base substrate 10 located on the high temperature side of the temperature gradient. This etching space 54 is a space in which Si atoms and C atoms are transported from SiC base substrate 10 to SiC container 50 for etching, using the temperature difference between SiC base substrate 10 and the bottom surface of SiC container 50 as a driving force.

[0062] Furthermore, SiC vessel 50 has substrate holder 55 that holds SiC base substrate 10 in the air and forms etching space 54. Note that substrate holder 55 may not be provided depending on the direction of the temperature gradient in the heating furnace. For example, if the heating furnace forms a temperature gradient such that the temperature decreases from lower vessel 52 to upper vessel 51, SiC base substrate 10 may be placed on the bottom surface of lower vessel 52 without providing substrate holder 55.

[0063] (TaC container 60) Material: TaC Container size: diameter 160mm x height 60mm Si vapor source 64 (Si compound): TaSi2

[0064] (Details of TaC container 60) Similar to the SiC container 50, the TaC container 60 is a fitting container having an upper container 61 and a lower container 62 that can fit together, and is configured to be able to house the SiC container 50. A minute gap 63 is formed at the fitting portion between the upper container 61 and the lower container 62, and the TaC container 60 is configured to be able to be evacuated (vacuumed) through this gap 63.

[0065] The TaC container 60 has a Si vapor supply source 64 capable of supplying vapor pressure of a gaseous species containing Si element into the TaC container 60. The Si vapor supply source 64 may be configured to generate vapor pressure of a gaseous species containing Si element inside the TaC container 60 during heat treatment.

[0066] <Crystal growth process S30> FIG. 8 is an explanatory diagram illustrating the crystal growth step S30 according to the first embodiment. The SiC base substrate 10 from which the strained layer 12 had been removed in the strained layer removal step S20 was placed opposite the semiconductor material 40 and placed in the crucible 30, and heated under the following conditions.

[0067] (Heating conditions) Heating temperature: 2040℃ Heating time: 70h Growth thickness: 500 μm N2 gas pressure: 10kPa

[0068] (crucible 30) Material: Tantalum carbide (TaC) and / or tungsten (W) Container size: 10mm x 10mm x 1.5mm Distance between SiC substrate 10 and semiconductor material 40: 1 mm

[0069] (Details of Crucible 30) Crucible 30 has a source material transport space 31 between SiC base substrate 10 and semiconductor material 40. Source material is transported from semiconductor material 40 onto SiC base substrate 10 via source material transport space 31.

[0070] 8(a) shows an example of a crucible 30 used in the crystal growth step S30. Similar to the SiC container 50 and the TaC container 60, this crucible 30 is a fitting container including an upper container 32 and a lower container 33 that can fit together. A minute gap 34 is formed at the fitting portion between the upper container 32 and the lower container 33, and the crucible 30 is configured so that the inside of the crucible 30 can be evacuated (evacuated) through this gap 34.

[0071] Furthermore, crucible 30 has substrate holder 35 that forms raw material transport space 31. Substrate holder 35 is provided between SiC base substrate 10 and semiconductor material 40, and forms raw material transport space 31 by placing semiconductor material 40 on the high-temperature side and SiC base substrate 10 on the low-temperature side.

[0072] Figures 8(b) and 8(c) show other examples of crucible 30 used in crystal growth step S30. The temperature gradient in Figures 8(b) and 8(c) is set to be the opposite of that in Figure 8(a), with SiC base substrate 10 placed on the upper side. That is, similar to Figure 8(a), semiconductor material 40 is placed on the high-temperature side and SiC base substrate 10 is placed on the low-temperature side to form source material transport space 31.

[0073] FIG. 8(b) shows an example in which a source material transport space 31 is formed between the SiC base substrate 10 and the semiconductor material 40 by fixing the SiC base substrate 10 to the upper vessel 32 side. 8(c) shows an example in which a through window is formed in upper vessel 32 and SiC base substrate 10 is placed therein, thereby forming raw material transport space 31 between upper vessel 32 and lower vessel 33. Alternatively, as shown in FIG. 8(c), raw material transport space 31 may be formed by providing intermediate member 36 between upper vessel 32 and lower vessel 33.

[0074] (Semiconductor Materials 40) Material: AlN sintered body Size: Width 20mm x Height 20mm x Thickness 5mm

[0075] (Details of Semiconductor Material 40) The AlN sintered body of the semiconductor material 40 was sintered by the following procedure. The AlN powder was placed in the frame of a TaC block and compressed with a moderate force.The compressed AlN powder and TaC block were then placed in a pyrolytic carbon crucible and heated under the following conditions.

[0076] Heating temperature: 1850℃ N2 gas pressure: 10kPa Heating time: 3h

[0077] 9 is a schematic diagram showing the crystal growth step S30 of Example 1. By growing AlN layer 20 on SiC base substrate 10 with through-holes 11 formed therein, a temperature gradient is formed in the horizontal direction of SiC base substrate 10, which can serve as a driving force for the lateral growth of AlN layer 20. In other words, even with a semiconductor material such as AlN, which is difficult to grow crystals from in the horizontal direction, AlN layer 20 can be formed on the region with through-holes 11 formed therein, and a large-diameter AlN substrate can be manufactured.

[0078] In the AlN substrate manufactured in Example 1, no threading dislocations were found in the AlN layer 20 formed on the region where the through-holes 11 were formed.

[0079] Comparative Example 1 In the SiC base substrate 10 of Comparative Example 1, grooves 13 were formed instead of the through holes 11 of Example 1. This SiC base substrate 10 was subjected to the crystal growth step S30 under the same conditions as in Example 1. That is, in Comparative Example 1, the through hole formation step S10 was not performed, but the crystal growth step S30 was performed.

[0080] 10 is a schematic diagram showing the crystal growth step S30 of Comparative Example 1. In the AlN substrate manufactured in Comparative Example 1, regions were formed above the grooves 13 where the AlN layer 20 did not grow.

[0081] That is, when grooves 13 are formed instead of through holes 11, the temperature in the region of grooves 13 does not decrease, and no temperature gradient is formed in the horizontal direction of SiC base substrate 10. As a result, no driving force for lateral growth is generated, and it is thought that AlN layer 20 is not formed in the region of grooves 13.

[0082] From the results of Example 1 and Comparative Example 1, it can be seen that by forming an AlN layer 20 on a SiC base substrate 10 having through-holes 11, a large-diameter AlN substrate can be manufactured.

[0083] 10 SiC base substrate 11 Through hole 12 Strain layer 13 Groove 20 AlN layer 30 Crucible 31 Raw material transportation space 40 Semiconductor Materials 50 SiC container 60 TaC container S10 Through hole formation process S20 Strained layer removal process S30 Crystal growth process S31 Lateral growth process S32 Vertical growth process

Claims

1. a crystal growth step of forming an aluminum nitride layer on a silicon carbide base substrate having through holes; the crystal growth step comprises: arranging the silicon carbide substrate and a raw material for the aluminum nitride layer so as to face each other; and heating the silicon carbide substrate and the raw material so as to create a temperature gradient between the silicon carbide substrate and the raw material, in which the silicon carbide substrate is on the low temperature side and the raw material is on the high temperature side.

2. 2. The method for producing an aluminum nitride substrate according to claim 1, wherein the crystal growth step is a step of heating the silicon carbide base substrate so as to form a temperature gradient along a vertical direction of the silicon carbide base substrate.

3. 3. The method for producing an aluminum nitride substrate according to claim 1, wherein the crystal growth step comprises a lateral growth step in which the aluminum nitride layer grows in a horizontal direction of the silicon carbide base substrate, and a vertical growth step in which the aluminum nitride layer grows in a vertical direction of the silicon carbide base substrate.

4. a through-hole forming step of forming a through-hole in the silicon carbide base substrate; 4. The method for producing an aluminum nitride substrate according to claim 1, further comprising a strained layer removing step of removing the strained layer introduced in the through-hole forming step.

5. The method for producing an aluminum nitride substrate according to claim 4 , wherein the through-hole forming step is a step of forming the through-holes by irradiating the silicon carbide base substrate with a laser.

6. 6. The method for producing an aluminum nitride substrate according to claim 4, wherein the strained layer removal step is a step of removing the strained layer of the silicon carbide base substrate by heat treatment.

7. 7. The method for producing an aluminum nitride substrate according to claim 5, wherein the strained layer removal step is a step of etching the silicon carbide base substrate in a silicon atmosphere.

8. a through-hole forming step of forming through-holes in the silicon carbide substrate before forming an aluminum nitride layer on the surface of the silicon carbide substrate; a crystal growth step of forming an aluminum nitride layer on the silicon carbide base substrate having through holes; a method for forming an aluminum nitride layer, wherein the crystal growth step comprises: arranging the silicon carbide substrate and a source material for the aluminum nitride layer so as to face each other; and heating the silicon carbide substrate and the source material so as to create a temperature gradient between the silicon carbide substrate and the source material, in which the silicon carbide substrate is on the low temperature side and the source material is on the high temperature side.

9. a crystal growth step of forming an aluminum nitride layer on a silicon carbide base substrate having through holes; a method for forming an aluminum nitride layer, wherein the crystal growth step comprises: arranging the silicon carbide substrate and a source material for the aluminum nitride layer so as to face each other; and heating the silicon carbide substrate and the source material so as to create a temperature gradient between the silicon carbide substrate and the source material, in which the silicon carbide substrate is on the low temperature side and the source material is on the high temperature side.

10. The method according to claim 8 , further comprising a strained layer removing step of removing the strained layer introduced by the through-hole forming step.

11. The method of claim 10 , wherein the strained layer removal step is a step of etching the silicon carbide base substrate by heat treatment.

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