Nitride semiconductor substrate and its manufacturing method

Abstract

This invention discloses a nitride semiconductor substrate comprising: a composite substrate having multiple layers; a silicon oxide layer or a TEOS layer deposited on the composite substrate, having a flat surface at a central portion and side surfaces surrounding the flat surface; a single-crystal silicon layer deposited on the silicon oxide layer or the TEOS layer; and a nitride semiconductor thin film formed on the single-crystal silicon layer. The nitride semiconductor substrate is characterized in that the entire flat surface at the central portion of the aforementioned silicon oxide layer or TEOS layer is covered by the aforementioned single-crystal silicon layer. This provides a nitride semiconductor substrate and a method for manufacturing the same, wherein the nitride semiconductor substrate exhibits no haze on the mirror edge surface after epitaxial growth, thus eliminating dust or reaction marks and reducing process defects.

Description

Technical Field

[0001] This invention relates to a nitride semiconductor substrate and a method for manufacturing the same. Prior Technology

[0002] Nitride semiconductors, primarily GaN and AlN, can be used to fabricate high electron mobility transistors (HEMTs) or high-voltage electronic components that utilize two-dimensional electron gases.

[0003] It is difficult to fabricate nitride wafers to grow these nitride semiconductors on substrates, and sapphire or SiC substrates are commonly used as substrates. However, to control the increase in aperture size and substrate cost, epitaxial growth by vapor deposition on silicon substrates has been adopted. Epitaxial growth films by vapor deposition on silicon substrates can use substrates with larger apertures than sapphire or SiC substrates, resulting in higher device productivity and advantages in heat dissipation. However, stress caused by differences in lattice constants or coefficients of thermal expansion can easily lead to increased warpage or plastic deformation, thus growth conditions or mitigation layers are used to reduce stress.

[0004] In high-voltage electronic components, a thicker epitaxial layer is required to improve high voltage withstand characteristics. However, if a thicker epitaxial layer is deposited, the silicon substrate, which serves as the substrate, will warp due to the difference in thermal expansion coefficients between the two layers.

[0005] Therefore, a large-diameter substrate (hereinafter referred to as a composite substrate) for growing nitride semiconductor epitaxial films has been developed, which has a large diameter and a coefficient of thermal expansion similar to that of nitride semiconductors. This composite substrate is composed of a composite substrate, a silicon oxide layer coupled only to one side of the aforementioned composite substrate, and a single-crystal silicon layer coupled to the aforementioned silicon oxide layer. The composite substrate includes: a polycrystalline ceramic core; a first adhesive layer, which is coupled to the aforementioned polycrystalline ceramic core over its entire surface; a conductive layer, which is coupled to the entire aforementioned first adhesive layer as needed; a second adhesive layer, which is coupled to the entire aforementioned conductive layer or the entire aforementioned first adhesive layer; and a barrier layer, which is coupled to the entire aforementioned second adhesive layer (Patent Document 1).

[0006] By using this composite substrate, a nitride semiconductor epitaxial growth substrate can be fabricated. This nitride semiconductor epitaxial growth substrate has a large aperture and a thick epitaxial layer, and it does not crack. Furthermore, due to the small difference in thermal expansion coefficients between the substrate and the nitride semiconductor, warping is less likely to occur during nitride semiconductor growth or cooling, allowing for minimal control of warping of the substrate after film deposition. Moreover, the composite substrate is mostly ceramic; the substrate itself is not only very hard and not easily deformed, but the wafer breakage issue that has not yet been resolved in GaN / Si also does not occur.

[0007] However, when using a growth substrate consisting of a silicon oxide layer coupled only to one side of a composite substrate and a single-crystal silicon layer coupled to the aforementioned silicon oxide layer to epitaxially grow nitride semiconductors and thus manufacture HEMT structure nitride semiconductor substrates, haze occurs on the edge surface of the epitaxially grown mirror. Reaction marks often appear at the interface between the aforementioned mirror and the haze area, becoming a source of dust during the manufacturing process. Furthermore, residues of chemicals and other substances from the manufacturing process remain in the haze area, also contributing to defects during the process. [Previous Technical Documents] (Patent Documents)

[0008] Patent Document 1: Japanese Patent Publication No. 2021-502701 Summary of the Invention

[0009] [The problem the invention aims to solve]

[0010] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a nitride semiconductor substrate and a method for manufacturing the same. The nitride semiconductor substrate is haze-free on the mirror edge surface after epitaxial growth, thus there is no dust or reaction traces and fewer defects in the process. [Technical means to solve the problem]

[0011] To address the above problems, the present invention provides a nitride semiconductor substrate comprising: Composite substrates have multiple layers; A silicon oxide layer or TEOS layer is deposited on the composite substrate, and has a flat surface in the center and side surfaces surrounding the flat surface; A single-crystal silicon layer, deposited on the silicon oxide layer or TEOS layer; and, A nitride semiconductor thin film is formed on the single-crystal silicon layer; wherein, The entire flat surface of the central part of the aforementioned silicon oxide layer or TEOS layer is covered by the aforementioned monocrystalline silicon layer.

[0012] In this way, if a nitride semiconductor substrate is used, and the flat surface of its silicon oxide layer or TEOS layer does not expose from the end of the aforementioned single-crystal silicon layer which serves as the growth surface of the nitride semiconductor thin film, then a nitride semiconductor substrate can be manufactured. This nitride semiconductor substrate does not grow a polycrystalline nitride semiconductor thin film on the flat surface of the silicon oxide layer or TEOS layer. Therefore, the mirror edge surface is free of fogging, dust or reaction marks, and there are fewer defects in the process.

[0013] Furthermore, it is preferable that the aforementioned side of the aforementioned silicon oxide layer or TEOS layer is covered by a silicon nitride film.

[0014] If such a nitride semiconductor substrate is used, fogging can be suppressed more effectively.

[0015] Furthermore, preferably, the aforementioned composite substrate comprises: a polycrystalline ceramic core; a first adhesive layer deposited on the entire polycrystalline ceramic core; a second adhesive layer deposited on the entire first adhesive layer; a second adhesive layer deposited on the entire first adhesive layer; and a barrier layer deposited on the entire second adhesive layer.

[0016] Furthermore, at this time, the aforementioned composite substrate may have a conductive layer deposited on the entire aforementioned first adhesive layer between the aforementioned first adhesive layer and the aforementioned second adhesive layer.

[0017] If a nitride semiconductor substrate is obtained by using such a composite substrate, a nitride semiconductor substrate can be fabricated that suppresses warping of the substrate after film formation.

[0018] Furthermore, it is preferable that the aforementioned conductive layer comprises a polycrystalline silicon layer.

[0019] Furthermore, preferably, the aforementioned first adhesive layer and the aforementioned second adhesive layer comprise TEOS or silicon oxide, and the aforementioned barrier layer comprises silicon nitride.

[0020] If such a nitride semiconductor substrate is used, the warpage of the substrate after film formation can be further reduced, and a thicker nitride semiconductor thin film can also be formed.

[0021] Furthermore, it is preferable that the aforementioned polycrystalline ceramic core contains aluminum nitride.

[0022] If it is such a nitride semiconductor substrate, the warpage of the substrate can be further reduced after film formation.

[0023] Furthermore, the present invention provides a method for manufacturing a nitride semiconductor substrate, comprising the following steps: Step (1): Prepare a composite substrate with multiple layers and a single-crystal silicon substrate; Step (2): The aforementioned single-crystal silicon substrate is bonded to the aforementioned composite substrate through a silicon oxide layer or a TEOS layer; Step (3) involves thinning the aforementioned bonded monocrystalline silicon substrate to form a monocrystalline silicon layer; Step (4): The aforementioned silicon oxide layer or TEOS layer and the end of the aforementioned single-crystal silicon layer are formed such that the entire flat surface of the central portion of the aforementioned silicon oxide layer or TEOS layer is covered by the aforementioned single-crystal silicon layer; Step (5): An AlN film is grown on the aforementioned monocrystalline silicon layer; and, Step (6): Growing one or more selected from GaN film, AlGaN film and AlN film on the aforementioned AlN film.

[0024] If such a manufacturing method is used, it is relatively easy to manufacture a nitride semiconductor substrate with no fogging, no dust or reaction marks on the mirror edge surface and fewer defects in the process.

[0025] Furthermore, it is preferable to set the aforementioned step (4) as a chamfering step.

[0026] If done in this way, manufacturing can be carried out without increasing the number of previous steps.

[0027] Furthermore, it is preferable to further include, between the aforementioned step (4) and the aforementioned step (5): step (4'), covering at least the side of the aforementioned silicon oxide layer or TEOS layer with a silicon nitride film.

[0028] If done in this way, the exposure of the silicon oxide layer or TEOS layer can be reliably eliminated.

[0029] Furthermore, it is preferable to configure the aforementioned composite substrate as comprising: a polycrystalline ceramic core; a first adhesive layer deposited on the entire polycrystalline ceramic core; a second adhesive layer deposited on the entire first adhesive layer; a second adhesive layer deposited on the entire first adhesive layer; and a barrier layer deposited on the entire second adhesive layer.

[0030] Furthermore, it is preferable to configure the aforementioned composite substrate as having a conductive layer deposited on the entire first adhesive layer between the aforementioned first adhesive layer and the aforementioned second adhesive layer.

[0031] If this manufacturing method is used, the warpage of the substrate can be further reduced after film formation. [Effects of the invention]

[0032] As described above, if it is the present invention, it can provide a nitride semiconductor substrate and a method for manufacturing the same. The nitride semiconductor substrate has no haze on the mirror edge surface after epitaxial growth, so there is no dust or reaction traces and fewer defects in the process. Simple Explanation of the Diagram

[0033] Figure 1 is a schematic cross-sectional view showing an example of a substrate for film formation in which a composite substrate, a silicon oxide layer, and a single-crystal silicon layer are stacked in a nitride semiconductor substrate according to the present invention. Figure 2 is a schematic cross-sectional view of the silicon oxide layer in the nitride semiconductor substrate used to illustrate the present invention in detail. Figure 3 is a schematic cross-sectional view showing an example of a substrate for film formation in which a silicon nitride film is formed on the side of a silicon oxide layer in a nitride semiconductor substrate of the present invention, comprising a composite substrate, a silicon oxide layer, and a single crystal silicon layer. Figure 4 is a schematic cross-sectional view showing an example of a conventional nitride semiconductor substrate for film formation, which has a composite substrate, a silicon oxide layer, and a single-crystal silicon layer stacked together. Figure 5 is a schematic diagram illustrating an example of an organometal chemical vapor deposition (MOCVD) apparatus that can be used in the manufacturing method of the nitride semiconductor substrate of the present invention. Figure 6 is a schematic diagram showing an example of a substrate for forming a nitride semiconductor substrate according to the present invention. Figure 7 is an illustrative diagram of an example of a method for manufacturing a nitride semiconductor substrate according to the present invention. Figure 8 is a cross-sectional view of a polycrystalline silicon layer grown at the end of a conventional nitride semiconductor substrate. Figure 9 is an enlarged view of the boundary between the monocrystalline layer and the polycrystalline silicon layer in Figure 8. Implementation

[0034] As described above, when a film-forming substrate consisting of a silicon oxide layer deposited only on one side of a composite substrate and a single-crystal silicon layer deposited on the aforementioned silicon oxide layer is used to epitaxially grow nitride semiconductors to manufacture a HEMT structure nitride semiconductor substrate, the surface of the mirror edge after epitaxial growth becomes hazy. Reaction marks often appear at the interface between the aforementioned mirror surface and the hazy portion, becoming a source of dust during the manufacturing process.

[0035] When the inventors observed the cross-sections of the mirror-like portion and the atomized portion using a scanning electron microscope (SEM), they discovered that a nitride semiconductor film was grown on the mirror-like portion using a single crystal, while a nitride semiconductor film was grown on the atomized portion using a polycrystalline material (Figure 8). Furthermore, they found that the mirror-like portion was grown on a single-crystal silicon layer, while the atomized portion was grown on a silicon oxide layer. The interface between the single-crystal and polycrystalline portions is shown in Figure 9. Additionally, the polycrystalline portion contained residues of chemicals and other substances from the manufacturing process, which also contributed to defects during the manufacturing process.

[0036] Furthermore, a nitride semiconductor substrate has been discovered in which a nitride semiconductor thin film is formed on a film-forming substrate. This film-forming substrate is obtained by bonding a single crystal silicon layer to a composite substrate with multiple layers through a silicon oxide layer. In this case, the flat surface of the silicon oxide layer does not expose from the end of the single crystal silicon layer, which serves as the growth surface of the aforementioned nitride semiconductor thin film. If this nitride semiconductor substrate is used, a substrate with no fogging at the edge portion can be manufactured, thereby completing the present invention.

[0037] That is, the present invention is a nitride semiconductor substrate comprising: a composite substrate having a plurality of layers; a silicon oxide layer or a TEOS layer deposited on the composite substrate and having a flat surface at the center and side surfaces surrounding the flat surface; a single-crystal silicon layer deposited on the silicon oxide layer or the TEOS layer; and a nitride semiconductor thin film formed on the single-crystal silicon layer; wherein the entire flat surface at the center of the aforementioned silicon oxide layer or the TEOS layer is covered by the aforementioned single-crystal silicon layer.

[0038] Furthermore, the present invention is a method for manufacturing a nitride semiconductor substrate, comprising the following steps: step (1), preparing a composite substrate having multiple layers and a single-crystal silicon substrate; step (2), bonding the single-crystal silicon substrate to the composite substrate with a silicon oxide layer or a TEOS layer in between; step (3), thinning the bonded single-crystal silicon substrate to form a single-crystal silicon layer; step (4), forming the silicon oxide layer or TEOS layer and the end of the single-crystal silicon layer such that the entire flat surface of the central portion of the silicon oxide layer or TEOS layer is covered by the single-crystal silicon layer; step (5), growing an AlN film on the single-crystal silicon layer; and step (6), growing one or more selected from GaN film, AlGaN film, and AlN film on the AlN film.

[0039] The present invention will now be described in detail, but the present invention is not limited to these descriptions.

[0040] (First Implementation Form) The nitride semiconductor substrate of the present invention comprises: a film-forming substrate, which includes a composite substrate, a bonding layer composed of a silicon oxide layer (SiO2 layer) or a tetraethyl orthosilicate (TEOS) layer, and a monocrystalline silicon layer; and a nitride semiconductor thin film formed on the film-forming substrate; wherein the entire planar surface of the bonding layer is covered by the monocrystalline silicon layer. Hereinafter, this specification uses the case where the bonding layer is a silicon oxide layer as an example, but the same principle applies to the case where the bonding layer is a TEOS layer.

[0041] Figure 1 shows an example of a film-forming substrate comprising a composite substrate, a silicon oxide layer, and a single-crystal silicon layer, according to the present invention. In this film-forming substrate, the single-crystal silicon layer 3 is deposited on the composite substrate 1, with the silicon oxide layer 2 in between. Here, the difference from the prior art is that the entire flat surface of the silicon oxide layer 2 in Figure 1 is covered by the single-crystal silicon layer 3. That is, no silicon oxide layer is exposed at the end 4 of the flat surface of the silicon oxide layer. In other words, the entire flat surface of the central portion of the silicon oxide layer 2 is covered by the single-crystal silicon layer 3.

[0042] As shown in Figure 4, in conventional nitride semiconductor substrates, the flat end 4 of the silicon oxide layer 2 is not covered by the monocrystalline silicon layer 3. Therefore, when a nitride semiconductor thin film is grown on a film-forming substrate, a polycrystalline silicon layer of the nitride semiconductor thin film grows on the silicon oxide layer 2 exposed at the flat end 4. In contrast, in this invention, the silicon oxide layer 2 is not exposed at the flat end 4, and therefore a polycrystalline silicon layer of the nitride semiconductor thin film does not grow on the silicon oxide layer 2.

[0043] Here, Figure 2 is used to describe in detail the structure of the silicon oxide layer in this invention. As shown in Figures 2(a) and 2(b), in the nitride semiconductor substrate of this invention, the silicon oxide layer 2 has a flat surface 21 (indicated by dashed lines) at the center and side surfaces 22 (indicated by thick lines) surrounding the flat surface. In this invention, the entire flat surface 21 is covered by a monocrystalline silicon layer 3. On the other hand, the side surfaces 22 surrounding the flat surface 21 may or may not be covered by the monocrystalline silicon layer 3; from the viewpoint of ease of manufacturing, it is preferable that they are not covered by the monocrystalline silicon layer 3. Furthermore, as shown in Figure 2(a), the side surfaces 22 may be perpendicular to the flat surface 21, and as shown in Figure 2(b), the side surfaces 22 may also be inclined. Furthermore, although the side surfaces 22 are depicted as straight lines (planes) in the figures, the side surfaces 22 may also be curved. Furthermore, the side surfaces 22 may also be chamfered surfaces.

[0044] In this invention, the nitride semiconductor thin film formed on the film-forming substrate can be an AlN film, and a GaN film or an AlGaN film formed thereon, or both. For example, an autorotational MOCVD reactor as shown in Figure 5 can be used to perform epitaxial growth of AlN films, AlGaN films, and GaN films on the film-forming substrate.

[0045] For example, as shown in Figure 6, the aforementioned film-forming substrate can be composed of a composite substrate, a silicon oxide layer 2 deposited only on one side of the aforementioned composite substrate, and a monocrystalline silicon layer 3 deposited on the aforementioned silicon oxide layer 2. The composite substrate includes: a polycrystalline ceramic core 6; a first adhesive layer 7 deposited on the entire aforementioned polycrystalline ceramic core; a conductive layer 8 deposited on the entire aforementioned first adhesive layer 7; a second adhesive layer 9 deposited on the entire aforementioned conductive layer 8; and a barrier layer 10 deposited on the entire aforementioned second adhesive layer 9.

[0046] Here, the polycrystalline ceramic core 6 can contain aluminum nitride and can be sintered at a high temperature of, for example, 1800°C using sintering aids, and preferably has a thickness of about 300~1150 μm. It is generally formed to the thickness of the Semiconductor Equipment and Materials International (SEMI) standard for single-crystal silicon substrates.

[0047] The first adhesive layer 7 and the second adhesive layer 9 may be layers containing tetraethyl orthosilicate (TEOS) or silicon oxide (SiO2), which can be deposited by processes such as low-pressure chemical vapor deposition (LPCVD) and chemical vapor deposition (CVD), and preferably have a thickness of 100 nm.

[0048] The conductive layer 8 may comprise a polycrystalline silicon layer, which can be deposited using processes such as LPCVD, and preferably has a thickness of approximately 300 nm. This layer is used to impart conductivity, and may be doped with elements such as boron (B) and phosphorus (P). Alternatively, depending on the circumstances, this conductive layer 8 may not be deposited.

[0049] The barrier layer 10 may contain silicon nitride and may be deposited by means of a process such as LPCVD, preferably having a thickness of 400 nm to 500 nm. This layer is used to prevent the diffusion or gas emission of elements such as yttrium, yttrium oxide, oxygen, metallic impurities, and other trace elements present in the ceramic core into the semiconductor processing chamber environment during high-temperature epitaxial growth processes.

[0050] The silicon oxide layer 2 can be deposited using processes such as LPCVD, and its thickness is preferably around 1.5 μm. The single-crystal silicon layer 3 preferably has a thickness of 300-500 nm. This layer is used as a growth surface for epitaxial growth of nitride semiconductors such as AlN and GaN.

[0051] The thickness of each layer is not limited to the above values, and there may not be all the layers. The film-forming substrate in this invention has at least a single crystal silicon layer, a silicon oxide layer or a TEOS layer, and a composite substrate with multiple layers.

[0052] The method for manufacturing a nitride semiconductor substrate according to the present invention can, for example, manufacture the nitride semiconductor substrate of the first embodiment of the present invention in the following manner.

[0053] First, prepare the composite substrate and the single-crystal silicon substrate as described above (step (1)). The single-crystal silicon substrate can be a single-crystal silicon substrate with an oxide film (silicon oxide layer) attached.

[0054] Then, the monocrystalline silicon substrate is bonded to the composite substrate through a silicon oxide layer or a TEOS layer (step (2)). The silicon oxide layer can be deposited on the composite substrate by, for example, an LPCVD process, and its thickness is preferably set to about 1.5 μm. Alternatively, the silicon oxide layer can be a layer obtained by combining the silicon oxide layer deposited on the composite substrate with the silicon oxide layer attached to the monocrystalline silicon substrate. The monocrystalline silicon substrate can be bonded to the silicon oxide layer in a bonding manner, for example, using a layer transfer process.

[0055] Next, the bonded monocrystalline silicon substrate is thinned to form a monocrystalline silicon layer (step (3)). The monocrystalline silicon layer preferably has a thickness of 300-500 nm. There is no particular limitation on the method of thinning the monocrystalline silicon layer, and conventional methods can be used. For example, thinning can be performed by bonding the composite substrate and the monocrystalline silicon substrate through a silicon oxide layer, and then grinding / polishing or etching the surface of the monocrystalline silicon substrate. Alternatively, the so-called ion implantation lift-off method can be used: an ion implantation layer is formed on the monocrystalline silicon substrate in advance, and the substrate is lifted off after bonding using the ion implantation layer.

[0056] Next, the silicon oxide layer and the end of the single-crystal silicon layer are formed such that the entire flat surface of the central part of the silicon oxide layer is covered by the single-crystal silicon layer (step (4)). Step (4) can be set as the step of performing chamfering on the outer periphery of the single-crystal silicon. At this time, for example, as shown in Figure 1, the chamfering is performed in such a way that the flat part of the silicon oxide layer is not exposed.

[0057] Subsequently, a nitride semiconductor thin film is formed on the single-crystal silicon layer. This step can be, for example, a step of growing an AlN film on the single-crystal silicon layer (step (5)) and a step of growing one or more selected from GaN film, AlGaN film and AlN film on the AlN film (step (6)).

[0058] Figure 5 shows a schematic diagram of an example of an MOCVD apparatus that can be used in the method for manufacturing a nitride semiconductor substrate according to the present invention. The MOCVD apparatus includes: a satellite section 52 having a pocket for placing a substrate 51 for film deposition; a quartz ceiling 53 and a quartz section 54; and an annular member 55, which is placed in such a way that it covers the inner side of the substrate 51 from the end. 56 is the direction of carrier airflow, and 57 is the direction of opening the cover.

[0059] As shown in Figure 5, the substrate for film formation can be placed, for example, in a wafer groove called a satellite section. During epitaxial growth, trimethylaluminum (TMAl) as an aluminum (Al) source, trimethylgallium (TMGa) as a gallium (Ga) source, or NH3 as a nitrogen (N) source can be used, and the method is not limited to these. Furthermore, the carrier gas can be N2 and H2, or any of these, and the process temperature is preferably set to around 900~1200°C.

[0060] At this point, a substrate for film formation is placed on the satellite section, and then the cover is closed to perform epitaxial growth. During this process, epitaxial layers can be formed sequentially from the substrate side toward the growth direction, for example, an AlN film, an AlGaN film, and then a GaN film is epitaxially grown. The structure of the epitaxial layer is not limited to this; there are also cases where an AlGaN film is not formed, or where an AlN film is further formed after the AlGaN film is formed.

[0061] (Second Implementation Form) As shown in Figure 3, the nitride semiconductor substrate of the present invention can be configured such that the film-forming substrate comprising a composite substrate 1, a silicon oxide layer 2, and a single-crystal silicon layer 3 is such that the side surface of the silicon oxide layer 2 is covered by a silicon nitride film 5. With such a nitride semiconductor substrate, it is possible to more reliably prevent the polycrystalline silicon layer of the nitride semiconductor thin film from growing at the end of the growth substrate. Furthermore, the silicon nitride film 5 may cover only the side surface of the silicon oxide layer 2, or it may cover both the side surface of the silicon oxide layer 2 and the side surface of the single-crystal silicon layer 3, and it may even cover the end of the epitaxial growth surface of the single-crystal silicon layer 3.

[0062] In the second embodiment, a portion of the silicon oxide layer is exposed by chamfering (i.e., the side of the silicon oxide layer is exposed), and the exposed silicon oxide layer is coated with a silicon nitride film (step (4')). Specifically, as shown in Figure 7, a CVD-SiN film is initially deposited on the entire surface of the chamfered wafer (Figure 7, (1)). Then, in the photolithography step, a resist is used to protect the exposed silicon oxide layer (Figure 7, (2)), thereby exposing the active layer portion. The wafer is then dry-etched using a dry etching apparatus to remove the SiN film from the active layer portion (Figure 7, (3)). Then, the resist in the protective film is removed / cleaned. Then, epitaxial growth is performed in the same manner as in the first embodiment (Figure 7, (4)). [Example]

[0063] The present invention will now be specifically described using examples and comparative examples, but the present invention is not limited to these examples.

[0064] (Example 1) A silicon oxide film is attached to a 100nm TEOS layer covering a 300μm polycrystalline ceramic core, a 300nm polycrystalline silicon layer covering the TEOS layer, a 100nm TEOS layer covering the polycrystalline silicon, and a 400nm silicon nitride layer (barrier layer) covering the TEOS layer. This is then bonded to a monocrystalline silicon substrate with the attached oxide film. Thinning (400nm) is achieved by grinding the surface of the monocrystalline silicon substrate. Next, chamfering of the edges is performed in a manner that avoids excessive cutting of the monocrystalline silicon layer, as shown in Figure 1, ensuring that the flat surface of the silicon oxide layer is not exposed on the wafer surface. Then, epitaxial growth of a HEMT structure (GaN 3nm / AlGaN 25nm / GaN 5000nm / tilted AlGaN 200nm / AlN 150nm / n-Si) is performed.

[0065] Compared to the comparative examples below, the yield obtained by the manufacturing method of Example 1 increased by 4%.

[0066] (Example 2) As shown in Figure 7, after the single-crystal silicon layer is attached, the edges are chamfered to expose the sides of the silicon oxide film. Then, a CVD-SiN film is deposited on the entire surface of the wafer. Next, during the photolithography step, the exposed silicon oxide layer is protected by covering it, exposing the active layer. Then, a dry etching apparatus is used to dry etch the wafer to remove the SiN film from the active layer and remove / clean the resist from the protective film. These steps are used to fabricate a nitride semiconductor substrate where the sides of the silicon oxide layer are covered by a silicon nitride film.

[0067] Compared to the comparative examples below, the yield obtained by the manufacturing method of Example 2 increased by 6%.

[0068] (Comparative Example) As shown in Figure 4, a nitride semiconductor substrate was manufactured under the same conditions as in Example 1, except that a portion of the flat surface of the silicon oxide film was exposed on the wafer surface. As a result, the yield was lower than that of Examples 1 and 2.

[0069] Furthermore, this invention is not limited to the embodiments described above. The embodiments described above are examples; any invention that has a substantially similar structure and performs the same function as the technical concept described in the claims of this invention is included within the technical scope of this invention.

[0070] 1: Composite substrate 2: Silicon oxide layer 3: Monocrystalline silicon layer 4: The end of the flat surface 5: Silicon nitride film 6: Polycrystalline ceramic core 7: First adhesive layer 8: Conductive layer 9: Second adhesive layer 10: Barrier layer 21: Flat surface 22: Side view 51: Substrate for film formation 52: Satellite Department 53: Ceiling 54: Quartz section 55: Ring-shaped component 56: Direction of carrier airflow 57: Direction for opening the cover

[0071] Domestic storage information (please note in order of storage institution, date, and number) none Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. A nitride semiconductor substrate comprising: a composite substrate having a plurality of layers deposited thereon; a silicon oxide layer or a TEOS layer deposited on the composite substrate and having a flat surface at a central portion and side surfaces surrounding the flat surface; a single-crystal silicon layer deposited on the silicon oxide layer or the TEOS layer; and a nitride semiconductor thin film formed on the single-crystal silicon layer; characterized in that the entire flat surface at the central portion of the aforementioned silicon oxide layer or the TEOS layer is covered by the aforementioned single-crystal silicon layer.

2. The nitride semiconductor substrate as described in claim 1, wherein, The aforementioned side of the silicon oxide layer or TEOS layer is covered by a silicon nitride film.

3. The nitride semiconductor substrate as described in claim 1, wherein, The aforementioned composite substrate comprises: a polycrystalline ceramic core; a first adhesive layer deposited on the entire polycrystalline ceramic core; a second adhesive layer deposited on the entire first adhesive layer; and a barrier layer deposited on the entire second adhesive layer.

4. The nitride semiconductor substrate as described in claim 2, wherein, The aforementioned composite substrate comprises: a polycrystalline ceramic core; a first adhesive layer deposited on the entire polycrystalline ceramic core; a second adhesive layer deposited on the entire first adhesive layer; a second adhesive layer deposited on the entire first adhesive layer; and a barrier layer deposited on the entire second adhesive layer.

5. The nitride semiconductor substrate as described in claim 3, wherein, The aforementioned composite substrate has a conductive layer deposited on the entire first adhesive layer between the aforementioned first adhesive layer and the aforementioned second adhesive layer.

6. The nitride semiconductor substrate as described in claim 4, wherein, The aforementioned composite substrate has a conductive layer deposited on the entire first adhesive layer between the aforementioned first adhesive layer and the aforementioned second adhesive layer.

7. The nitride semiconductor substrate as described in claim 5, wherein, The aforementioned conductive layer comprises a polycrystalline silicon layer.

8. The nitride semiconductor substrate as described in claim 6, wherein, The aforementioned conductive layer comprises a polycrystalline silicon layer.

9. The nitride semiconductor substrate as described in any one of claims 3 to 8, wherein, The aforementioned first adhesive layer and the aforementioned second adhesive layer contain TEOS or silicon oxide, and the aforementioned barrier layer contains silicon nitride.

10. The nitride semiconductor substrate as described in any one of claims 3 to 8, wherein, The aforementioned polycrystalline ceramic core contains aluminum nitride.

11. The nitride semiconductor substrate as described in claim 9, wherein, The aforementioned polycrystalline ceramic core contains aluminum nitride.

12. A method for manufacturing a nitride semiconductor substrate, characterized by comprising the following steps: Step (1), preparing a composite substrate having multiple layers and a single-crystal silicon substrate; Step (2), bonding the single-crystal silicon substrate to the composite substrate with a silicon oxide layer or a TEOS layer in between; Step (3), thinning the bonded single-crystal silicon substrate to form a single-crystal silicon layer; Step (4), forming the silicon oxide layer or TEOS layer and the end of the single-crystal silicon layer such that the entire flat surface of the central portion of the silicon oxide layer or TEOS layer is covered by the single-crystal silicon layer; Step (5), growing an AlN film on the single-crystal silicon layer; and Step (6), growing one or more selected from GaN film, AlGaN film, and AlN film on the AlN film.

13. A method for manufacturing a nitride semiconductor substrate as described in claim 12, wherein, Set the aforementioned step (4) as the chamfering step.

14. A method for manufacturing a nitride semiconductor substrate as described in claim 12, wherein, Between the aforementioned step (4) and the aforementioned step (5), there is a further step (4'), in which at least the side of the aforementioned silicon oxide layer or TEOS layer is covered with a silicon nitride film.

15. A method for manufacturing a nitride semiconductor substrate as described in claim 13, wherein, Between the aforementioned step (4) and the aforementioned step (5), there is a further step (4'), in which at least the side of the aforementioned silicon oxide layer or TEOS layer is covered with a silicon nitride film.

16. A method for manufacturing a nitride semiconductor substrate as described in any one of claims 12 to 15, wherein, The aforementioned composite substrate comprises: a polycrystalline ceramic core; a first adhesive layer deposited on the entire polycrystalline ceramic core; a second adhesive layer deposited on the entire first adhesive layer; and a barrier layer deposited on the entire second adhesive layer.

17. A method for manufacturing a nitride semiconductor substrate as described in claim 16, wherein, The aforementioned composite substrate is configured such that a conductive layer is deposited on the entire first adhesive layer between the aforementioned first adhesive layer and the aforementioned second adhesive layer.

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