Gallium nitride base substrate, gallium nitride growth substrate, method for manufacturing gallium nitride base substrate

Abstract

Reduces defects in the epitaxial layer. [Solution] The gallium nitride base substrate on which the epitaxial layer 40 is placed comprises a support substrate 20 composed of aluminum nitride and a gallium nitride thin film substrate 30 composed of gallium nitride, which is placed on the support substrate 20 and surface activated bonded to the support substrate 20, wherein the gallium nitride thin film substrate 30 has an equal stoichiometric ratio throughout its entire region.

Description

Technical Field

[0001] The present disclosure relates to a gallium nitride base substrate, a gallium nitride growth substrate, and a method for manufacturing a gallium nitride base substrate

Background Art

[0002] Conventionally, it has been proposed that a silicon thin film substrate is bonded to a support substrate to constitute a gallium nitride (hereinafter also simply referred to as GaN) base substrate, and an epitaxial layer containing GaN is grown on the silicon thin film substrate of the GaN base substrate (see Patent Document 1). In this GaN base substrate, the silicon thin film substrate is prepared as follows. That is, first, an ingot composed of silicon is prepared. Then, ions are implanted into the ingot to form an embrittled layer, and the ingot is split starting from the embrittled layer, whereby the silicon thin film substrate is prepared.

[0003] Note that when ions are implanted into an ingot to form an embrittled layer, ions are implanted in a Gaussian distribution, so damage such as disrupted crystallinity is introduced into portions other than the embrittled layer. Accordingly, the silicon thin film substrate that has been subjected to, for example, heat treatment at about 1000 °C or the like to recover damage caused by ion implantation is prepared.

[0004] Then, by growing the epitaxial layer containing GaN on the GaN base substrate having the silicon thin film substrate with recovered damage, an epitaxial layer having crystal defects (hereinafter also simply referred to as defects) equivalent to those of a structure in which an epitaxial layer containing GaN is grown on a silicon substrate is grown. Note that when the silicon thin film substrate is Si(111) whose main surface (that is, the surface on which epitaxial growth is performed) is the (111) plane, the lattice constant difference from GaN is 17%. When GaN is epitaxially grown on such a silicon thin film substrate, the defect density such as dislocations in the epitaxial layer is 1.0×10 9 cm -2This is the extent of the problem. Furthermore, when an epitaxial layer containing GaN is grown using a silicon thin film substrate whose main surface is a (111) plane or different from that of the silicon thin film substrate, the difference in lattice constants between the silicon thin film substrate and the GaN becomes greater than 17%, and the defect density in the epitaxial layer also increases. Therefore, when growing an epitaxial layer containing GaN on a silicon thin film substrate in this manner, Si(111) is used as the silicon thin film substrate. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-138130 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, the inventors are also considering manufacturing a GaN base substrate by bonding a GaN thin film substrate to a support substrate, and manufacturing a GaN grown substrate by growing a GaN-containing epitaxial layer on a GaN base substrate, in order to further reduce defects in the epitaxial layer. However, similar to the silicon thin film substrate described above, if a GaN thin film substrate is formed by ion implantation of a GaN ingot and then heat-treated to repair the damage, there is a possibility that the GaN will decompose or otherwise disrupt the chemical balance. Furthermore, when repairing GaN damage, the damage repair temperature is approximately 1000 to 1400°C, but GaN can experience nitrogen loss at 800°C. Therefore, it is difficult to use the same manufacturing method for silicon thin film substrates.

[0007] This disclosure aims to provide a GaN base substrate, a GaN growth substrate, and a method for manufacturing a GaN base substrate that can reduce defects in the epitaxial layer. [Means for solving the problem]

[0008] According to one aspect of this disclosure, the GaN base substrate on which the epitaxial layer (40) is placed comprises a support substrate (20) composed of aluminum nitride and a GaN thin film substrate (30) composed of GaN, which is placed on the support substrate and surface activated bonding with the support substrate, wherein the GaN thin film substrate has an equal stoichiometric ratio throughout its entire region.

[0009] According to another aspect of this disclosure, the GaN base substrate on which the epitaxial layer (40) is placed comprises a support substrate (20) composed of ScAlMgO4 and a GaN thin film substrate (30) composed of GaN, which is placed on the support substrate and surface activated bonding with the support substrate, wherein the GaN thin film substrate has equal stoichiometric ratios throughout its entire region.

[0010] According to these findings, the GaN base substrate is constructed by bonding a GaN thin-film substrate to a support substrate. Furthermore, the GaN thin-film substrate has an equal stoichiometric ratio throughout its entire surface. Therefore, by growing an epitaxial layer on such a GaN base substrate, defects in the epitaxial layer can be reduced.

[0011] Furthermore, according to another aspect of this disclosure, the GaN growth substrate comprises the above-mentioned GaN base substrate and an epitaxial layer comprising GaN and disposed on the GaN base substrate.

[0012] According to this, since the epitaxial layer is placed on the GaN base substrate mentioned above, defects are reduced.

[0013] Furthermore, according to another aspect of this disclosure, a method for manufacturing a GaN base substrate comprises: preparing a support substrate (20) composed of aluminum nitride or ScAlMgO4; preparing an ingot (200) composed of GaN; forming a modified layer (220) along the plane direction of the ingot by irradiating the inside of the ingot with laser light (L); forming a GaN thin film substrate (30) from the ingot by dividing the ingot with the modified layer as the boundary; and joining the support substrate and the GaN thin film substrate by surface activation bonding.

[0014] According to this, the GaN base substrate is constructed by bonding a GaN thin-film substrate to a support substrate. Furthermore, since the GaN thin-film substrate is prepared by irradiating an ingot with laser light, the stoichiometric ratio is equal throughout the entire region. Therefore, by growing an epitaxial layer on such a GaN base substrate, defects in the epitaxial layer can be reduced.

[0015] The reference numerals in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described later. [Brief explanation of the drawing]

[0016] [Figure 1] This is a cross-sectional view of the GaN base substrate in the first embodiment. [Figure 2] This is a cross-sectional view of the GaN growth substrate in the first embodiment. [Figure 3A] Figure 1 is a cross-sectional view showing the manufacturing process of the GaN base substrate. [Figure 3B] This is a cross-sectional view showing the manufacturing process of the GaN base substrate, following Figure 3A. [Figure 3C] This is a cross-sectional view showing the manufacturing process of the GaN base substrate, following Figure 3B. [Figure 3D] This is a cross-sectional view showing the manufacturing process of GaN base substrates, following Figure 3C. [Figure 3E] This is a cross-sectional view showing the manufacturing process of the GaN base substrate, following Figure 3D. [Figure 3F] This is a cross-sectional view showing the manufacturing process of the GaN base substrate that follows Figure 3E. [Figure 3G] This is a cross-sectional view showing the manufacturing process of the GaN base substrate that follows Figure 3F. [Figure 3H] This is a cross-sectional view of a GaN growth substrate in which an epitaxial layer is grown on a GaN base substrate. [Figure 4] This is a cross-sectional view of the GaN base substrate in the second embodiment. [Figure 5] This is a cross-sectional view of the GaN base substrate in the third embodiment. [Figure 6] This is a cross-sectional view of the GaN base substrate in the fourth embodiment. [Modes for Carrying Out the Invention]

[0017] Hereinafter, embodiments of the present disclosure will be described based on the drawings. Note that in the following respective embodiments, parts that are the same or equivalent to each other will be described with the same reference signs assigned.

[0018] (First Embodiment) The first embodiment will be described with reference to the drawings. The GaN base substrate 10 of the present embodiment includes a support substrate 20 and a GaN thin film substrate 30. Note that the GaN base substrate 10 is formed in a cylindrical wafer shape.

[0019] In the present embodiment, the support substrate 20 has a core layer 21 and a design layer 22 disposed on the core layer 21. The core layer 21 is for bringing the thermal expansion coefficient of the support substrate 20 close to that of GaN, and in the present embodiment, it is composed of AlN (aluminum nitride) or the like which has a thermal expansion coefficient close to that of GaN. The design layer 22 is for absorbing irregularities on the surface of the core layer 21 and planarizing the surface on the side opposite to the core layer 21, and in the present embodiment, it is composed of an oxide film.

[0020] The GaN thin film substrate 30 is obtained by dividing an ingot composed of GaN, as described later, and is in the form of a plate having one surface 30a and the other surface 30b. Furthermore, the stoichiometric ratio of the GaN thin film substrate 30 in this embodiment is equal throughout its entire surface. The other surface 30b of the GaN thin film substrate 30 is connected to the design layer 22 of the support substrate 20 by surface activation bonding. Note that the stoichiometric ratio being equal throughout the entire surface of the GaN thin film substrate 30 means that no crystal collapse has occurred in any region. The thickness of the GaN thin film substrate 30 is not particularly limited, but for example, it is about 1 to 20 μm. In this embodiment, the one surface 30a of the GaN thin film substrate 30 is the gallium surface, and the other surface 30b is the nitrogen surface.

[0021] The above describes the configuration of the GaN base substrate 10 in this embodiment. As shown in Figure 2, the GaN growth substrate 100 is constructed by stacking an epitaxial layer 40 containing GaN on a GaN thin film substrate 30. In this GaN growth substrate 100, since the epitaxial layer 40 containing GaN is placed on the GaN thin film substrate 30, the difference in lattice constants is smaller compared to, for example, the case where the epitaxial layer 40 is placed on a silicon layer, and the defect density of the epitaxial layer 40 is reduced to 1.0 × 10⁻¹⁶. 4 cm -2 It can be reduced to the following:

[0022] Such a GaN growth substrate 100 can be used, for example, to construct semiconductor devices by dividing it into individual chips. When constructing a semiconductor device using the GaN growth substrate 100, for example, an epitaxial layer 40 is constructed by stacking an undoped GaN layer and an undoped AlGaN layer placed on top of the GaN layer. In such an epitaxial layer 40, a two-dimensional electron gas layer is induced on the GaN layer side of the AlGaN / GaN interface by the piezoelectric effect and spontaneous polarization effect. For this reason, the GaN growth substrate 100 can be used, for example, to construct a semiconductor device having a HEMT (High Electron Mobility Transistor) utilizing the two-dimensional electron gas layer. When a semiconductor device having a HEMT is constructed using the GaN growth substrate 100 of this embodiment, the defect density of the epitaxial layer 40 can be reduced as described above, and for example, current collapse can be reduced. Current collapse is a phenomenon unique to the formation of HEMTs in GaN, and is a phenomenon in which the on-resistance increases during operation, which is said to be caused by defects.

[0023] Furthermore, such a GaN growth substrate 100 can be used, for example, to manufacture a GaN thin film substrate 30, as will be described later.

[0024] Next, the manufacturing methods for the GaN base substrate 10 and the GaN growth substrate 100 will be explained with reference to Figures 3A to 3H.

[0025] First, as shown in Figure 3A, an ingot 200 is prepared, which is made of GaN and has a first main surface 200a and a second main surface 200b. The ingot 200 is manufactured, for example, by the amonothermal process and has a thickness of about 3 mm. In this embodiment, the first main surface 200a of the ingot 200 is the gallium surface and the second main surface 200b is the nitrogen surface.

[0026] Next, as shown in Figure 3B, the first retaining member 210 is placed on the first main surface 200a side of the ingot 200. The first retaining member 210 is, for example, a dicing tape having a base material 211 and an adhesive 212. The base material 211 is made of a material that is resistant to warping during the manufacturing process, and is made of, for example, glass, a silicon substrate, or ceramics. The adhesive 212 is made of a material whose adhesive strength can be changed, and is made of, for example, an ultraviolet curing resin, wax, or double-sided tape whose adhesive strength changes with temperature and light.

[0027] Next, as shown in Figure 3C, laser light L is irradiated from the second main surface 200b of the ingot 200 to form a modified layer 220 along the plane direction of the ingot 200 at a predetermined depth D from the first main surface 200a of the ingot 200. In this embodiment, this step is performed using a laser apparatus that includes a laser light source for emitting laser light L, a spatial light modulator for modulating the laser light L output from the laser light source, a focusing lens for focusing the laser light L modulated by the spatial light modulator, a displaceable stage, etc. The spatial light modulator is composed of, for example, a reflective liquid crystal (LCOS: abbreviation for Liquid Crystal on Silicon). The predetermined depth D is set according to the thickness of the GaN thin film substrate 30 and the amount to be removed, for example, it is set to 30 μm.

[0028] Then, when forming the altered layer 220, the ingot 200 is placed on a stage, and the position of the stage is adjusted so that the focal point of the laser beam L is scanned relative to the surface direction of the ingot 200. As a result, in the area irradiated with the laser beam L, an altered layer 220 is formed in which gallium and nitrogen are decomposed by thermal energy. More specifically, by irradiating with the laser beam L, nitrogen evaporates as a gas and gallium is precipitated, forming an altered layer 220 in which cracks occur. Furthermore, when forming the altered layer 220 by irradiating with laser beam L in this way, the crystallinity of the parts of the ingot 200 other than the part in which the altered layer 220 is formed is not destroyed.

[0029] Next, as shown in Figure 3D, the second retaining member 230 is placed on the second main surface 200b side of the ingot 200. The second retaining member 230 is composed of a base material 231 and an adhesive 232 whose adhesive strength can be changed, similar to the first retaining member 210. The base material 231 in the second retaining member 230 is made of, for example, glass, a silicon substrate, ceramics, etc. The adhesive 232 in the second retaining member 230 is made of, for example, ultraviolet curing resin, wax, double-sided tape, etc.

[0030] Then, as shown in Figure 3E, the first holding member 210 and the second holding member 230 are gripped and tensile force or the like is applied in the thickness direction of the ingot 200, and the ingot 200 is divided with the altered layer 220 as the boundary (i.e., the starting point of the division). One of the divided portions is then made into a GaN thin film substrate 30. In this embodiment, the portion supported by the first holding member 210 is made into the GaN thin film substrate 30. Furthermore, since the GaN thin film substrate 30 is formed by irradiating the ingot 200 with laser light L as described above, the stoichiometric ratio is equal throughout the entire region.

[0031] Hereinafter, the side of the GaN thin film substrate 30 from the ingot 200 that has been separated will be referred to as the first main surface 200a of the new ingot 200. Furthermore, the side of the GaN thin film substrate 30 that has been separated from the ingot 200 will be referred to as the other surface 30b of the GaN thin film substrate 30, and the side of the GaN thin film substrate 30 that is held by the first holding member 210 will be referred to as one surface 30a of the GaN thin film substrate 30.

[0032] Subsequently, as shown in Figure 3F, the first main surface 200a of the ingot 200 and the other surface 30b of the GaN thin film substrate 30 are planarized by performing a CMP (Chemical Mechanical Polishing) method using a polishing device 300 or the like. In this embodiment, for example, about 20 μm is removed by the CMP method. This prepares a GaN thin film substrate 30 with a thickness of about 10 μm. In this embodiment, the GaN thin film substrate 30 is prepared from the ingot 200 in this way. The ingot 200, with its first main surface 200a planarized, is then used again to perform the processes shown in Figure 3A and later.

[0033] Next, as shown in Figure 3G, a support substrate 20 is prepared on which a design layer 22 is placed on a core layer 21, and the design layer 22 of the support substrate 20 and the other surface 30b of the GaN thin film substrate 30 are bonded by surface activation bonding. In this embodiment, the GaN base substrate 10 is manufactured in this way. In this embodiment, since the first main surface 200a of the ingot 200 is the gallium surface, one surface 30a of the GaN thin film substrate 30 becomes the gallium surface.

[0034] Then, as shown in Figure 3H, an epitaxial layer 40 containing GaN is epitaxially grown on the GaN thin film substrate 30 of the GaN base substrate 10 by performing a method such as HVPE (Halide Vapor Phase Epitaxy) at 1000 to 1200°C. This constitutes a GaN growth substrate 100 in which the epitaxial layer 40 is arranged on the GaN base substrate 10.

[0035] Furthermore, such a GaN growth substrate 100 can be used, for example, as an ingot 200 in the process shown in Figure 3A, specifically in the epitaxial layer 40 portion. Therefore, after manufacturing the GaN growth substrate 100, it becomes possible to mass-produce GaN base substrates 10 without preparing a new ingot 200. When using the GaN growth substrate 100 as an ingot 200, the thickness of the epitaxial layer 40 can be increased to a degree that does not cause warping of the GaN growth substrate 100, for example, by depositing the epitaxial layer 40 to a thickness of about 100 to 1000 μm.

[0036] Furthermore, such a GaN growth substrate 100 can be used to manufacture semiconductor devices having HEMTs, etc., by appropriately adjusting the configuration of the epitaxial layer 40. In this case, the thickness of the epitaxial layer 40 is appropriately designed according to the required voltage withstand voltage, etc.

[0037] According to the embodiment described above, the GaN base substrate 10 is constructed by bonding a GaN thin film substrate 30 to a support substrate 20. Furthermore, since the GaN thin film substrate 30 is prepared by irradiating an ingot 200 with laser light L, the stoichiometric ratio is equal throughout the entire region. Therefore, by growing an epitaxial layer 40 on such a GaN base substrate 10, defects in the epitaxial layer 40 can be reduced.

[0038] (Second Embodiment) A second embodiment will now be described. This embodiment is a modification of the support substrate 20 compared to the first embodiment. Other aspects are the same as in the first embodiment, so a detailed explanation will be omitted here.

[0039] As shown in Figure 4, the GaN base substrate 10 of this embodiment has a support substrate 20 having a core layer 21, a design layer 22, and a silicon layer 23. In other words, the support substrate 20 of this embodiment is a so-called QST (Qromis Substrate Technology: registered trademark) substrate. The silicon layer 23 has a main surface (i.e., the bonding surface with the GaN thin film substrate 30) which is a (111) plane and is made of Si(111), with a thickness of about 0.3 to 3.0 μm. The other surface 30b of the GaN thin film substrate 30 is connected to the silicon layer 23 of the support substrate 20 by surface activation bonding. In this embodiment, the silicon layer 23 corresponds to the bonding layer.

[0040] According to the embodiment described above, the GaN base substrate 10 is constructed by bonding a GaN thin film substrate 30 to a support substrate 20, and the GaN thin film substrate 30 has an equal stoichiometric ratio throughout its entire region. Therefore, the same effects as in the first embodiment can be obtained.

[0041] (1) In this embodiment, the support substrate 20 is made of a QST substrate. Therefore, an existing substrate can be used as the support substrate 20, and the manufacturing process can be simplified. Also, since the support substrate 20 has a silicon layer 23, when a semiconductor device is constructed using the GaN growth substrate 100, semiconductor elements can also be formed on the silicon layer 23. For example, when a semiconductor device is constructed using the GaN growth substrate 100, if a diode is formed on the silicon layer 23 and an epitaxial layer 40 is used to construct a HEMT, a semiconductor device with improved avalanche withstand capability can be obtained. In this embodiment, an example in which the silicon layer 23 is Si(111) has been described, but the crystal orientation of the silicon layer 23 can be changed as appropriate.

[0042] (Third embodiment) A third embodiment will now be described. In this embodiment, a barrier layer is placed between the silicon layer 23 of the support substrate 20 and the GaN thin film substrate 30, compared to the second embodiment. Other aspects are the same as in the second embodiment, so a detailed explanation will be omitted here.

[0043] In this embodiment, as shown in Figure 5, the GaN base substrate 10 has a barrier layer 50 positioned between the silicon layer 23 of the support substrate 20 and the GaN thin film substrate 30. The GaN thin film substrate 30 is bonded to the barrier layer 50 by surface activation bonding. The barrier layer 50 is intended to suppress the reaction between the Ga of the GaN thin film substrate 30 and the silicon layer 23 when growing the epitaxial layer 40, and is composed of a material having a melting point of 1500°C or higher. For example, the barrier layer 50 is composed of a high-melting-point metal such as W (tungsten) or Ta (tantalum). The barrier layer 50 is composed of a polycrystalline film such as AlN or a single-crystal film. The barrier layer 50 is composed of a single-crystal film such as SiC (silicon carbide) or Al2O3 (aluminum oxide). The barrier layer 50, composed of such a material, is positioned on the silicon layer 23 by, for example, a sputtering method. However, the barrier layer 50 is preferably one that has a small difference in thermal expansion coefficient with respect to the GaN thin film substrate 30 and the epitaxial layer 40, and is preferably composed of an AlN single crystal film.

[0044] According to the embodiment described above, the GaN base substrate 10 is constructed by bonding a GaN thin film substrate 30 to a support substrate 20, and the GaN thin film substrate 30 has an equal stoichiometric ratio throughout its entire region. Therefore, the same effects as in the first embodiment can be obtained.

[0045] (1) In this embodiment, a barrier layer 50 made of a material having a melting point of 1500°C or higher is placed between the silicon layer 23 of the support substrate 20 and the GaN thin film substrate 30. Therefore, the reaction between the Ga of the GaN thin film substrate 30 and the silicon layer 23 can be suppressed. Consequently, a deterioration in the quality of the epitaxial layer 40 can be suppressed. Furthermore, when a semiconductor element is formed on the silicon layer 23, a change in the characteristics of the semiconductor element can be suppressed.

[0046] (Fourth Embodiment) A fourth embodiment will now be described. This embodiment is a modification of the GaN thin-film substrate 30 compared to the first embodiment. Other aspects are the same as in the first embodiment, so a detailed explanation will be omitted here.

[0047] As shown in Figure 6, in this embodiment, the GaN base substrate 10 is configured such that, when viewed from the stacking direction between the support substrate 20 and the GaN thin film substrate 30, the outer edge of the support substrate 20 protrudes from the GaN thin film substrate 30. In other words, the diameter of the GaN thin film substrate 30 is shorter than the diameter of the support substrate 20.

[0048] Such a GaN base substrate 10 is manufactured by using the epitaxial layer 40 of the GaN growth substrate 100 described in the first embodiment as an ingot 200. That is, when an epitaxial layer 40 is grown on the GaN base substrate 10 to form a GaN growth substrate 100, the diameter of the epitaxial layer 40 is not constant along the thickness direction, and the diameter becomes shorter toward the side opposite to the GaN base substrate 10. For this reason, when the epitaxial layer 40 of this GaN growth substrate 100 is used as an ingot 200 to manufacture a GaN thin film substrate 30, the diameter becomes shorter than the diameter of the support substrate 20.

[0049] According to the embodiment described above, the GaN base substrate 10 is constructed by bonding a GaN thin film substrate 30 to a support substrate 20, and the GaN thin film substrate 30 has an equal stoichiometric ratio throughout its entire region. Therefore, the same effects as in the first embodiment can be obtained.

[0050] (1) In this embodiment, the outer edge of the support substrate 20 protrudes from the GaN thin film substrate 30. Such a GaN base substrate 10 is manufactured by using the epitaxial layer 40 of the GaN growth substrate 100 as an ingot 200. Therefore, compared to the case in which the GaN base substrate 10 is manufactured using an ingot 200 composed of an amonothermal method or the like, it becomes easier to handle mass production and costs can be reduced.

[0051] (Other embodiments) This disclosure is described in accordance with embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and idea of ​​this disclosure.

[0052] In the embodiments described above, an example was given in which a support substrate 20 is used in which a design layer 22 is arranged on a core layer 21. However, the support substrate 20 does not necessarily have to include a design layer 22.

[0053] Furthermore, in each of the above embodiments, a support substrate 20 having a core layer 21 made of AlN was described. However, the support substrate 20 may also be made up of ScAlMgO4 (i.e., a so-called SAM substrate). In this case, the support substrate 20 may or may not have a design layer 22. Also, the support substrate 20 may have a silicon layer 23 as in the second embodiment described above. Note that ScAlMgO4 has a thermal expansion coefficient difference of about 0.6% from GaN, which is almost the same as that of GaN, and a lattice constant mismatch ratio of about 1.8%, which is almost the same as that of GaN.

[0054] Furthermore, in the second embodiment described above, a support substrate 20 was described in which a silicon layer 23 was arranged on a design layer 22. However, instead of a silicon layer 23 being arranged on the design layer 22, a polysilicon layer or an amorphous silicon layer may be arranged on the design layer 22. In this case, the polysilicon layer or amorphous silicon layer corresponds to the bonding layer. In other words, the configuration of the bonding layer can be appropriately changed depending on the application.

[0055] Furthermore, the above embodiments can be combined as appropriate. For example, the fourth embodiment may be combined with the second and third embodiments.

[0056] [Disclosure of the Invention] The above disclosure can be understood from the following perspectives, for example. [First point of view] A gallium nitride base substrate on which an epitaxial layer (40) is arranged, A support substrate (20) made of aluminum nitride, The system comprises a gallium nitride thin film substrate (30) which is disposed on the support substrate and surface activated bonded with the support substrate, and which is made of gallium nitride, The gallium nitride thin film substrate is a gallium nitride base substrate in which the stoichiometric ratio is equal throughout the entire region. [Second perspective] A gallium nitride base substrate on which an epitaxial layer (40) is arranged, A support substrate (20) composed of ScAlMgO4, The system comprises a gallium nitride thin film substrate (30) which is disposed on the support substrate and surface activated bonded with the support substrate, and which is made of gallium nitride, The gallium nitride thin film substrate is a gallium nitride base substrate in which the stoichiometric ratio is equal throughout the entire region. [Third perspective] The support substrate is a gallium nitride base substrate according to the first or second aspect, wherein the support substrate has a bonding layer (23) on the gallium nitride thin film substrate side. [Fourth perspective] The bonding layer is a silicon layer, The gallium nitride base substrate according to the third aspect, wherein a barrier layer (50) made of a material having a melting point of 1500°C or higher is disposed between the bonding layer and the gallium nitride thin film substrate. [Fifth perspective] The support substrate is a gallium nitride base substrate according to any one of the first to fourth views, wherein the support substrate has a portion of its outer edge that protrudes from the gallium nitride thin film substrate in the stacking direction between the support substrate and the gallium nitride thin film substrate. [Sixth perspective] Gallium nitride growth substrate, A gallium nitride substrate as described in any one of the first to fifth aspects, A gallium nitride growth substrate comprising: an epitaxial layer containing gallium nitride, disposed on the gallium nitride base substrate. [Seventh perspective] A method for manufacturing a gallium nitride substrate, A support substrate (20) is prepared, which is made of aluminum nitride or ScAlMgO4. Prepare an ingot (200) made of gallium nitride, By irradiating the interior of the ingot with laser light (L), a modified layer (220) is formed along the planar direction of the ingot. By dividing the ingot with the altered layer as the boundary, a gallium nitride thin film substrate (30) is formed from the ingot. A method for manufacturing a gallium nitride base substrate, comprising joining the support substrate and the gallium nitride thin film substrate by surface activation bonding. [Perspective 8] After joining the support substrate and the gallium nitride thin film substrate, an epitaxial layer (40) containing gallium nitride is grown on the gallium nitride thin film substrate. A method for manufacturing a gallium nitride substrate according to the seventh aspect, wherein the epitaxial layer is used as the ingot by preparing the aforementioned ingot. [Explanation of Symbols]

[0057] 10 GaN basic substrate 20 Support substrate 30 GaN thin film substrate

Claims

1. A gallium nitride base substrate on which an epitaxial layer (40) is arranged, A support substrate (20) made of aluminum nitride, The system comprises a gallium nitride thin film substrate (30) which is disposed on the support substrate and surface activated bonded with the support substrate, and which is made of gallium nitride, The gallium nitride thin film substrate is a gallium nitride base substrate in which the stoichiometric ratio is equal throughout the entire region.

2. A gallium nitride base substrate on which an epitaxial layer (40) is arranged, ScAlMgO ４ A support substrate (20) comprising the following, The system comprises a gallium nitride thin film substrate (30) which is disposed on the support substrate and surface activated bonded with the support substrate, and which is made of gallium nitride, The gallium nitride thin film substrate is a gallium nitride base substrate in which the stoichiometric ratio is equal throughout the entire region.

3. The gallium nitride base substrate according to claim 1 or 2, wherein the support substrate has a bonding layer (23) on the gallium nitride thin film substrate side.

4. The bonding layer is a silicon layer, The gallium nitride base substrate according to claim 3, wherein a barrier layer (50) made of a material having a melting point of 1500°C or higher is disposed between the bonding layer and the gallium nitride thin film substrate.

5. The gallium nitride base substrate according to claim 1 or 2, wherein the support substrate has a portion of its outer edge that protrudes from the gallium nitride thin film substrate in the stacking direction between the support substrate and the gallium nitride thin film substrate.

6. Gallium nitride growth substrate, A gallium nitride base substrate according to claim 1 or 2, A gallium nitride growth substrate comprising: an epitaxial layer containing gallium nitride, disposed on the gallium nitride base substrate.

7. A method for manufacturing a gallium nitride substrate, Aluminum nitride, or ScAlMgO ４ A support substrate (20) is prepared which includes the following: Prepare an ingot (200) made of gallium nitride, By irradiating the inside of the ingot with laser light (L), a modified layer (220) is formed along the planar direction of the ingot. By dividing the ingot with the altered layer as the boundary, a gallium nitride thin film substrate (30) is formed from the ingot. A method for manufacturing a gallium nitride base substrate, comprising joining the support substrate and the gallium nitride thin film substrate by surface activation bonding.

8. After joining the support substrate and the gallium nitride thin film substrate, an epitaxial layer (40) containing gallium nitride is grown on the gallium nitride thin film substrate. The method for manufacturing a gallium nitride substrate according to claim 7, wherein the epitaxial layer is used as the ingot by preparing the aforementioned ingot.

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