Nitride semiconductor substrate and method for producing same

Abstract

To provide a nitride semiconductor substrate without having a reaction mark or a polycrystal growth portion in an edge part when epitaxially growing an AlN layer on a silicon substrate and epitaxially growing a GaN or AlGaN layer thereon, and a method for manufacturing the same.SOLUTION: A nitride semiconductor substrate includes a nitride semiconductor thin film deposited on a film deposition substrate consisting of single crystal silicon. A silicon nitride film is formed in an outer peripheral portion of the film deposition substrate; an AlN film is formed on the film deposition substrate and the silicon nitride film; and the nitride semiconductor thin film is formed on the AlN film.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a nitride semiconductor substrate and a method for manufacturing the same. [Background technology]

[0002] Nitride semiconductors such as GaN and AlN can be used to fabricate high electron mobility transistors (HEMTs) that use two-dimensional electron gas and high-voltage electronic devices.

[0003] It is difficult to manufacture nitride wafers by growing these nitride semiconductors on a substrate, and sapphire or SiC substrates are used as the substrate. However, epitaxial growth by vapor phase growth on silicon substrates is used to increase the diameter and reduce the cost of substrates (Patent Document 1). The production of epitaxially grown films by vapor phase growth on silicon substrates allows the use of substrates with larger diameters than sapphire or SiC substrates, which is advantageous in terms of high device productivity and heat dissipation.

[0004] When epitaxial growth of an AlN buffer layer, buffer layer, and GaN-HEMT structure is performed on a silicon substrate, there are areas near the edges where the AlN buffer layer is not formed cleanly. When a GaN or AlGaN layer is stacked on top of this, the Ga and Si in the TMG raw material react in the areas where the AlN film is not formed, generating reaction marks. These reaction marks become a source of dust during processing. Even if a SiO2 protective film is applied to prevent reaction marks from occurring, polycrystals grow on the protective film, and residues of chemicals and other materials remain during processing, causing defects. Therefore, it is necessary to eliminate the polycrystalline growth areas on the surface near the edges. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-36030 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above-mentioned problems, and has an object to provide a nitride semiconductor substrate and a manufacturing method thereof that are free of reaction marks or polycrystalline growth portions at the edge portions when an AlN layer is epitaxially grown on a silicon substrate and a nitride semiconductor thin film is epitaxially grown thereon. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides A nitride semiconductor substrate having a nitride semiconductor thin film formed on a film-formation substrate made of single crystal silicon, The present invention provides a nitride semiconductor substrate, in which a silicon nitride film is formed on the outer periphery of the film-formation substrate, an AlN film is formed on the film-formation substrate and the silicon nitride film, and the nitride semiconductor thin film is formed on the AlN film.

[0008] In this manner, if a silicon nitride film is formed on the outer periphery of a film-formation substrate made of single crystal silicon, the occurrence of reaction traces is suppressed, so that no dust is generated due to reaction traces during device processing, and adhesion of particles to the nitride semiconductor substrate is suppressed.

[0009] Moreover, the nitride semiconductor thin film on the silicon nitride film is preferably single crystal.

[0010] If the nitride semiconductor substrate has a single-crystal nitride semiconductor thin film on a silicon nitride film, polycrystalline growth does not occur, and therefore no residue of chemicals or the like remains during the process, which would cause defects.

[0011] The present invention also provides a method for producing a nitride semiconductor substrate, comprising the steps of: (1) forming a silicon nitride film on an outer periphery of a film-formation substrate made of single crystal silicon; (2) growing an AlN film on the film-formation substrate and on the silicon nitride film of the outer periphery; and (3) growing a GaN film, an AlGaN film, or both, on the AlN film; The present invention provides a method for producing a nitride semiconductor substrate, comprising the steps of:

[0012] According to this manufacturing method, it is possible to relatively easily and reliably manufacture a nitride semiconductor substrate having no reaction marks or polycrystalline growth portions at its edge portions. Effect of the Invention

[0013] As described above, the present invention can provide a nitride semiconductor substrate and a manufacturing method thereof that are free of reaction marks or polycrystalline growth portions at edge portions when an AlN layer is epitaxially grown on a silicon substrate and a nitride semiconductor thin film, in particular a GaN or AlGaN layer, is epitaxially grown thereon. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing an example of a nitride semiconductor substrate of the present invention. [Diagram 2] 1A to 1C are schematic diagrams illustrating an example of a method for producing a nitride semiconductor substrate according to the present invention. [Diagram 3] 3 is a photograph of the edge vicinity and edge portion of a nitride semiconductor substrate produced in an example. [Figure 4] 1 is a graph showing the thickness of an epitaxial layer measured at an edge portion and from the edge surface toward the center of a nitride semiconductor substrate produced in an example. [Diagram 5] 3 is a photograph of the vicinity of the edge and the edge portion of the nitride semiconductor substrate produced in Comparative Example 1. [Figure 6] 1 is a cross-sectional photograph of the vicinity of an edge and an edge portion of a nitride semiconductor substrate produced in Comparative Example 2. [Figure 7] 7 is an enlarged photograph of the polycrystalline portion of FIG. 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] As described above, there has been a demand for the development of a nitride semiconductor substrate that does not leave reaction marks on the edges when epitaxial growth of a nitride semiconductor consisting of an AlN buffer layer, a buffer layer, and a GaN-HEMT structure is performed on a silicon substrate.

[0016] As a result of extensive research, the inventors discovered that by forming a silicon nitride film on the outer periphery of a film-forming substrate made of single crystal silicon, it is possible to prevent the occurrence of reaction traces, and furthermore, it is possible to prevent polycrystals from growing on the film, as occurs with silicon oxide films, and thus completed the present invention.

[0017] That is, the present invention is a nitride semiconductor substrate having a nitride semiconductor thin film formed on a film-formation substrate made of single crystal silicon, wherein a silicon nitride film is formed on the outer periphery of the film-formation substrate, an AlN film is formed on the film-formation substrate and the silicon nitride film, and the nitride semiconductor thin film is formed on the AlN film.

[0018] The present invention also relates to a method for manufacturing a nitride semiconductor substrate, the method including: (1) forming a silicon nitride film on an outer periphery of a film-formation substrate made of single crystal silicon; (2) growing an AlN film on the film-formation substrate and on the silicon nitride film on the outer periphery; and (3) growing a GaN film, an AlGaN film, or both on the AlN film.

[0019] The present invention will be described in detail below, but the present invention is not limited thereto.

[0020] [Nitride semiconductor substrate] 1 shows a schematic diagram of an example of the nitride semiconductor substrate of the present invention. The nitride semiconductor substrate 1 of the present invention has a silicon nitride film 3 formed on the outer periphery 5 of a film-formation substrate 2 made of single crystal silicon, and further has an epitaxial layer 4 formed on the center of the film-formation substrate 2 and on the silicon nitride film 3 on the outer periphery 5. The epitaxial layer 4 is made of an AlN film (buffer layer) formed on the center of the film-formation substrate 2 and on the silicon nitride film 3 on the outer periphery 5, and a nitride semiconductor thin film formed on the AlN film. The nitride semiconductor thin film is not particularly limited, and may be, for example, a GaN film, an AlGaN film, or both.

[0021] Here, the outer periphery refers to, for example, the edge portion (the upper surface of the edge portion) and the area in the vicinity of the edge portion. The edge portion may be a chamfered surface.

[0022] The thickness of the silicon nitride film 3 is not particularly limited, but may be, for example, 0.2 to 20 nm, preferably 1 to 4 nm, and particularly 2 nm. The range of the outer periphery 5 where the silicon nitride film 3 is formed is not particularly limited, but may be, for example, 0.2 to 20 mm, preferably 0.5 to 10 mm, more preferably 1 to 5 mm, and particularly 2.5 mm at the edge portion and in the vicinity of the edge. The thickness of the epitaxial layer 4 is not particularly limited, but may be, for example, 0.1 to 20 μm, preferably 0.5 to 10 μm, more preferably 1 to 5 μm, and particularly about 2.7 μm.

[0023] The film-formation substrate 2 made of single crystal silicon is not particularly limited, and may be CZ single crystal silicon or FZ single crystal silicon, and there is no particular limit to the presence or absence, type, and concentration of a dopant.

[0024] In the nitride semiconductor substrate of the present invention, since a silicon nitride film is formed on the outer periphery of the film-forming substrate made of single crystal silicon, an AlN film (buffer layer) is formed on the silicon nitride film on the outer periphery of the growth substrate. As a result, the AlN film (buffer layer) is well formed even on the outer periphery of the growth substrate, so that even when a GaN film or an AlGaN film is formed on the AlN film as a nitride semiconductor thin film, no reaction traces are generated due to the reaction between Si of the growth substrate and Ga of the raw material gas. Furthermore, by forming the film covering the outer periphery as a silicon nitride film, the nitride semiconductor thin film formed thereon becomes single crystal.

[0025] [Method of manufacturing nitride semiconductor substrate] The nitride semiconductor substrate of the present invention can be manufactured by the method for manufacturing a nitride semiconductor substrate of the present invention, for example, as follows: Hereinafter, the flow of the method for manufacturing a nitride semiconductor substrate of the present invention will be described with reference to FIG.

[0026] <Process (1)> First, a silicon nitride film is formed on the outer periphery of a film-formation substrate made of single crystal silicon (step (1)).

[0027] First, as shown in FIG. 2(a), a film-forming substrate (silicon substrate) 2 made of single crystal silicon is placed in an RTA (Rapid Thermal Annealing) furnace and heat-treated in an ammonia atmosphere diluted with argon at, for example, 1175° C. for 10 seconds or in a nitrogen atmosphere at, for example, 1200° C. for 10 seconds to form a silicon nitride film 3 having a thickness of, for example, 2 nm on the surface of the film-forming substrate 2.

[0028] Next, as shown in FIG. 2(b), a resist 6 is applied onto the silicon nitride film 3.

[0029] 2(c), the resist near the edge (e.g., 2.5 mm) and at the edge is exposed and developed to become a protective film, and then the silicon substrate with the protective film near the edge and at the edge is etched in a dry etching device for, e.g., 10 seconds to remove the silicon nitride film 3 in the portion without the protective film (the center of the film-formation substrate 2).Then, the resist protective film on the outer periphery is removed and cleaning is performed.

[0030] <Steps (2) and (3)> Next, a step (step (2)) of growing an AlN film on the film-formation substrate and on the silicon nitride film on the outer periphery, and a step (step (3)) of growing a GaN film, an AlGaN film, or both, on the AlN film are performed.

[0031] As shown in Fig. 2(d), a nitride semiconductor (epitaxial layer 4) consisting of an AlN buffer layer, a buffer layer, and a GaN-HEMT layer is epitaxially grown to, for example, about 2.7 µm in an MOCVD apparatus. In the nitride semiconductor substrate 1 manufactured in this way, single crystals grow even on the silicon nitride film on the periphery, and polycrystals do not grow. Furthermore, no reaction marks are generated at the interface between the silicon nitride film and the silicon substrate. EXAMPLES

[0032] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these.

[0033] (Example) In the flow of Figure 2, the silicon substrate was placed in an RTA furnace and heat-treated at 1175°C for 10 seconds in an ammonia atmosphere diluted with argon to form a silicon nitride film with a thickness of 2 nm on the entire surface, and the resist film was left near the edge (2.5 mm) and at the edge by photolithography, and the silicon nitride film was removed from the part without the resist film by etching for 10 seconds in a dry etching device. After that, the resist film was removed, the substrate was cleaned, and a nitride semiconductor consisting of an AlN buffer layer, a buffer layer, and a GaN-HEMT structure (total thickness 2.7 μm) was epitaxially grown in an MOCVD device. As a result, as shown in the photograph in Figure 3, the part near the edge and the edge of the wafer were mirror-finished, there was no reaction trace, and it can be seen that no polycrystals had grown. Figure 4 shows the epitaxially grown film thickness [μm] measured at every 100 μm from the edge and the edge surface to the center by cross-sectional SEM.

[0034] Comparative Example 1 Except for not forming a silicon nitride film near or at the edge, a nitride semiconductor consisting of an AlN buffer layer, a buffer layer, and a GaN-HEMT structure was epitaxially grown on a silicon substrate in the same manner as in the example. As a result, reaction marks were generated near and at the edge of the wafer, as shown in Figure 5.

[0035] Comparative Example 2 Except for forming a silicon oxide film near the edge and at the edge, a nitride semiconductor consisting of an AlN buffer layer, a buffer layer, and a GaN-HEMT structure was epitaxially grown in the same manner as in the example. As a result, as shown in Figures 6 and 7, no reaction marks were found near the edge and at the edge of the wafer, but polycrystals were grown on the silicon oxide film.

[0036] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention. [Explanation of symbols]

[0037] 1... nitride semiconductor substrate, 2... film formation substrate made of single crystal silicon, 3: silicon nitride film; 4: epitaxial layer; 5: outer periphery; 6: resist.

Claims

1. A nitride semiconductor substrate having a nitride semiconductor thin film formed on a film-formation substrate made of single crystal silicon, a silicon nitride film is formed on the outer periphery of the film-formation substrate, an AlN film is formed on the film-formation substrate and the silicon nitride film, and the nitride semiconductor thin film is formed on the AlN film; and 2. The nitride semiconductor substrate, wherein the nitride semiconductor thin film on the silicon nitride film is a single crystal.

2. A method for manufacturing a nitride semiconductor substrate, comprising the steps of: (1) forming a silicon nitride film on an outer periphery of a film-formation substrate made of single crystal silicon; (2) growing an AlN film on the film-formation substrate and on the silicon nitride film of the outer periphery; and (3) A step of growing a GaN film, an AlGaN film, or both of them as a nitride semiconductor thin film on the AlN film. and A method for producing a nitride semiconductor substrate, comprising the steps of: forming the nitride semiconductor thin film on the silicon nitride film into a single crystal;

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