NITRIDE SEMICONDUCTOR SUBSTRATE AND METHOD FOR MANUFACTURING NITRIDE SEMICONDUCTOR SUBSTRATE

Abstract

To provide a nitride semiconductor substrate of which plastic deformation is suppressed and a manufacturing method thereof, a nitride semiconductor layer being grown on a SOI substrate for manufacturing a high frequency device in the nitride semiconductor substrate and the manufacturing method thereof.SOLUTION: The present invention relates to a high frequency nitride semiconductor substrate. The nitride semiconductor substrate includes: a SOI substrate in which a monocrystal silicon thin film is formed via a silicon oxide layer on a monocrystal silicon substrate; and a nitride semiconductor layer including a GaN layer formed on the SOI substrate. The monocrystal silicon thin film contains nitrogen in concentration of 2.0×1014 atoms / cm3 or more, resistivity is 100 Ωcm or more, resistivity of the monocrystal silicon substrate is 50 mΩcm or less, and a thickness of the silicon oxide layer ranges from 10 to 400 nm.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] The MOCVD method, which is one of the semiconductor thin film manufacturing methods, is widely used because it has excellent properties for large diameter and mass production, and can form homogeneous thin film crystals. Nitride semiconductors, such as GaN, are expected to be the next generation semiconductor material that exceeds the material limits of Si. GaN, SiC, sapphire, Si, etc. are used as substrates for epitaxial growth of GaN and other semiconductors in the MOCVD method.

[0003] In recent years, substrates in which a single crystal silicon substrate is bonded onto an insulating layer (SiO2, etc.), such as SOI, have been actually applied as substrates for epitaxial growth of GaN. The growth of nitride semiconductors on SOI substrates is disclosed, for example, in Patent Documents 1 to 4. In GaN / SOI, individual discrete components can be electrically isolated, and this insulation method has been proven to eliminate the backgate effect (the variation in the threshold voltage of a MOSFET due to the voltage of the substrate) and reduce switching noise. These characteristics are advantages that do not appear in silicon substrates, GaN substrates, etc. SOI substrates can be obtained by bonding substrates as described, for example, in Patent Documents 5 and 6.

[0004] Recently, as disclosed in Patent Document 7, high frequency devices have been manufactured by epitaxially growing a nitride semiconductor on a silicon single crystal seed layer.

[0005] In high frequency devices, degradation of characteristics due to the substrate, loss due to the substrate, and degradation of second and third harmonic characteristics are observed.

[0006] Substrates for high frequency devices are generally made by epitaxially growing a GaN layer on a high resistivity substrate to fabricate high frequency devices.

[0007] Substrates for high-frequency devices use high-resistivity substrates to prevent signals from flowing from the epitaxial layer to the underlying Si substrate. When a nitride semiconductor epitaxial layer is stacked on a high-resistivity silicon substrate, the nitride semiconductor epitaxial layer is stacked by devising a buffer layer as a stress relaxation layer. However, high-resistivity silicon substrates are subject to plastic deformation during epitaxial growth due to stress. To solve this problem, it is preferable to use an SOI substrate made of a high-resistivity silicon substrate bonded to a low-resistivity substrate (a hard single-crystal silicon substrate dedicated to nitride semiconductor epitaxial growth) that is resistant to stress, via a silicon oxide layer.

[0008] However, even in the nitride semiconductor substrate for manufacturing a high frequency device produced in this manner, plastic deformation may occur during epitaxial growth of the nitride semiconductor. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2010-40737 A [Patent Document 2] JP 2011-97062 A [Patent Document 3] JP 2019-208022 A [Patent Document 4] Patent No. 5396369 specification [Patent Document 5] Patent No. 5233111 Specification [Patent Document 6] JP 2010-278339 A [Patent Document 7] JP 2021-100087 A Summary of the Invention [Problem to be solved by the invention]

[0010] 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 in which a nitride semiconductor layer is grown on an SOI substrate for manufacturing high-frequency devices, in which plastic deformation is suppressed, and a manufacturing method thereof. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides a high frequency nitride semiconductor substrate, comprising: an SOI substrate in which a single crystal silicon thin film is formed on a single crystal silicon substrate via a silicon oxide layer; a nitride semiconductor layer including a GaN layer formed on the SOI substrate; Including, The single crystal silicon thin film is doped with nitrogen at a concentration of 2.0×10 14 atoms / cm 3 or more, and the resistivity is 100 Ω cm or more, The single crystal silicon substrate has a resistivity of 50 mΩcm or less, The present invention provides a nitride semiconductor substrate, wherein the silicon oxide layer has a thickness of 10 to 400 nm.

[0012] In this way, the single crystal silicon thin film absorbs nitrogen at 2.0 × 10 14 atoms / cm 3 A nitride semiconductor substrate in which a nitride semiconductor layer including a GaN layer is formed on an SOI substrate containing the nitride semiconductor layer at a concentration of 100 Ωcm or more, the resistivity of the single crystal silicon thin film is 100 Ωcm or more, the resistivity of the single crystal silicon substrate is 50 mΩcm or less, and the thickness of the silicon oxide layer is 10 to 400 nm, can be a nitride semiconductor substrate in which plastic deformation is suppressed. Furthermore, by using this nitride semiconductor substrate, a high frequency device with good high frequency characteristics can be manufactured.

[0013] The silicon oxide layer preferably has a thickness of 10 to 200 nm.

[0014] If the thickness of the silicon oxide layer is in the range of 10 to 200 nm, the plastic deformation of the nitride semiconductor substrate can be further suppressed.

[0015] The present invention also provides a method for producing a high frequency nitride semiconductor substrate, comprising the steps of: Preparing two single crystal silicon substrates to be a bond wafer and a base wafer; bonding the two single crystal silicon substrates together via a silicon oxide layer; a step of thinning the bond wafer to form a single crystal silicon thin film, thereby obtaining an SOI substrate in which the single crystal silicon thin film is formed on the base wafer via the silicon oxide layer; growing a nitride semiconductor layer including a GaN layer on the single crystal silicon thin film of the SOI substrate to obtain a nitride semiconductor substrate in which the nitride semiconductor layer is formed on the SOI layer; Including, The single crystal silicon substrate to be the bond wafer is doped with nitrogen at a concentration of 2.0×10 14 atoms / cm 3 The concentration of the material is 100 Ω cm or more, and the resistivity is 100 Ω cm or more. The single crystal silicon substrate to be the base wafer has a resistivity of 50 mΩcm or less, The present invention provides a method for producing a nitride semiconductor substrate, characterized in that the silicon oxide layer has a thickness of 10 to 400 nm.

[0016] Such a method for producing a nitride semiconductor makes it possible to relatively easily and reliably produce a nitride semiconductor substrate in which plastic deformation is suppressed, and by using the nitride semiconductor substrate produced in this manner, a high-frequency device with good high-frequency characteristics can be produced.

[0017] The silicon oxide layer preferably has a thickness of 10 to 200 nm.

[0018] If a silicon oxide layer having a thickness of 10 to 200 nm is used, a nitride semiconductor substrate in which plastic deformation is further suppressed can be manufactured.

[0019] The single crystal silicon substrate that becomes the bond wafer can be prepared by manufacturing using an FZ method or an MCZ method.

[0020] The single crystal silicon substrate to be the bond wafer can be manufactured by, for example, the FZ method or the MCZ method. Effect of the Invention

[0021] As described above, the nitride semiconductor substrate of the present invention can be a nitride semiconductor substrate in which plastic deformation is suppressed. Furthermore, the nitride semiconductor substrate of the present invention can be used to manufacture high-frequency devices with excellent high-frequency characteristics.

[0022] Furthermore, the method for producing a nitride semiconductor substrate of the present invention makes it possible to relatively easily and reliably produce a high-frequency nitride semiconductor substrate in which plastic deformation is suppressed. Furthermore, by using a nitride semiconductor substrate produced by the method for producing a nitride semiconductor substrate of the present invention, a high-frequency device with good high-frequency characteristics can be produced. [Brief description of the drawings]

[0023] [Figure 1] 1 is a schematic cross-sectional view showing an example of a nitride semiconductor substrate of the present invention. [Diagram 2] 1 is a schematic diagram showing a configuration of an example of a nitride semiconductor substrate of the present invention. [Diagram 3] 1 is a graph showing changes in warpage during epitaxial growth in an example and a comparative example. [Figure 4] 1 is a graph showing the relationship between the thickness and warpage of a silicon oxide layer in an example and a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] When a nitride semiconductor is epitaxially grown on an SOI substrate having a high resistivity single crystal silicon thin film in order to manufacture a high frequency device as described above, plastic deformation may occur during the epitaxial growth.

[0025] The inventors of the present invention have conducted extensive research into a nitride semiconductor substrate in which plastic deformation is suppressed and a method for manufacturing the same, and have found that the single crystal silicon thin film of the SOI substrate contains 2.0×10 nitrogen. 14 atoms / cm 3 or greater, the resistivity of the single crystal silicon thin film is 100 Ωcm or more, the resistivity of the single crystal silicon substrate is 50 mΩcm or less, and the thickness of the silicon oxide layer of the SOI substrate is 10 to 400 nm, thereby making it possible to manufacture a nitride semiconductor substrate in which plastic deformation is suppressed, and the present invention has been completed.

[0026] That is, the present invention provides a high frequency nitride semiconductor substrate, an SOI substrate in which a single crystal silicon thin film is formed on a single crystal silicon substrate via a silicon oxide layer; a nitride semiconductor layer including a GaN layer formed on the SOI substrate; Including, The single crystal silicon thin film is doped with nitrogen at a concentration of 2.0×10 14 atoms / cm 3 or more, and the resistivity is 100 Ω cm or more, The single crystal silicon substrate has a resistivity of 50 mΩcm or less, The nitride semiconductor substrate is characterized in that the silicon oxide layer has a thickness of 10 to 400 nm.

[0027] The present invention also provides a method for manufacturing a high frequency nitride semiconductor substrate, comprising the steps of: Preparing two single crystal silicon substrates to be a bond wafer and a base wafer; bonding the two single crystal silicon substrates together via a silicon oxide layer; a step of thinning the bond wafer to form a single crystal silicon thin film, thereby obtaining an SOI substrate in which the single crystal silicon thin film is formed on the base wafer via the silicon oxide layer; growing a nitride semiconductor layer including a GaN layer on the single crystal silicon thin film of the SOI substrate to obtain a nitride semiconductor substrate in which the nitride semiconductor layer is formed on the SOI layer; Including, The single crystal silicon substrate to be the bond wafer is doped with nitrogen at a concentration of 2.0×10 14 atoms / cm 3 The concentration of the material is 100 Ω cm or more, and the resistivity is 100 Ω cm or more. The single crystal silicon substrate to be the base wafer has a resistivity of 50 mΩcm or less, The method for producing a nitride semiconductor substrate is characterized in that the silicon oxide layer has a thickness of 10 to 400 nm.

[0028] The present invention will be described in detail below with reference to the drawings, but the present invention is not limited thereto.

[0029] [Nitride semiconductor substrate] Fig. 1 shows a schematic cross-sectional view of an example of the nitride semiconductor substrate of the present invention, and Fig. 2 shows a schematic diagram of the configuration of an example of the nitride semiconductor substrate of the present invention.

[0030] The nitride semiconductor substrate 1 shown in FIG.

[0031] In the SOI substrate 2, a single crystal silicon thin film 23 is formed on a single crystal silicon substrate 21 with a silicon oxide layer 22 interposed therebetween.

[0032] The nitride semiconductor layer 3 includes a GaN layer 34 shown in Fig. 2. The nitride semiconductor layer 3 shown in Fig. 2 includes an AlN layer 31, an AlGaN layer 32, and superlattice layers (SLs) 33 in addition to the GaN layer 34, but the nitride semiconductor layer 3 is not limited to the configuration shown in Fig. 2 as long as it includes the GaN layer 34.

[0033] The single crystal silicon thin film 23 of the SOI substrate 2 of the nitride semiconductor substrate 1 is doped with nitrogen at a concentration of 2.0×10 14 atoms / cm 3 or more, and has a resistivity of 100 Ωcm or more. The single crystal silicon substrate 21 has a resistivity of 50 mΩcm or less. The silicon oxide layer 22 has a thickness of 10 to 400 nm.

[0034] Such an SOI substrate 2 can exhibit high strength even if it has a high resistivity SOI layer 23. By including such an SOI substrate 2, the nitride semiconductor substrate 1 of the present invention can be one in which plastic deformation is suppressed.

[0035] On the other hand, the nitrogen concentration in the single crystal silicon thin film 23 is 2.0×10 14 atoms / cm 3 If it is less than this, the plastic deformation cannot be sufficiently suppressed.

[0036] Furthermore, if the thickness of the silicon oxide layer 22 exceeds 400 nm, plastic deformation cannot be sufficiently suppressed. Conversely, if the thickness of the silicon oxide layer 22 is less than 10 nm, bonding does not go well and voids occur. If the thickness of the silicon oxide layer 22 is 10 to 400 nm, the nitride semiconductor substrate 1 can be made in which plastic deformation is further suppressed.

[0037] Furthermore, if the resistivity of the single crystal silicon substrate 21 exceeds 50 mΩcm, the plastic deformation cannot be sufficiently suppressed.

[0038] Furthermore, since the resistivity of the single crystal silicon thin film 23 is 100 Ωcm or more, a high frequency device having good high frequency characteristics can be manufactured.

[0039] [Method of manufacturing nitride semiconductor substrate] The method for producing a nitride semiconductor substrate of the present invention comprises the steps of: Preparing two single crystal silicon substrates to be a bond wafer and a base wafer; bonding the two single crystal silicon substrates together via a silicon oxide layer; a step of thinning the bond wafer to form a single crystal silicon thin film, thereby obtaining an SOI substrate in which the single crystal silicon thin film is formed on the base wafer via the silicon oxide layer; growing a nitride semiconductor layer including a GaN layer on the single crystal silicon thin film of the SOI substrate to obtain a nitride semiconductor substrate in which the nitride semiconductor layer is formed on the SOI layer; Includes.

[0040] In the process of preparing two single crystal silicon substrates, nitrogen was added at 2.0 × 10 14 atoms / cm 3 or more and has a resistivity of 100 Ωcm or more.

[0041] The single crystal silicon substrate to be the bond wafer is preferably a single crystal silicon substrate manufactured by the FZ method or the MCZ method and having a surface orientation of (111). For example, the single crystal silicon substrate is doped with nitrogen during the manufacturing process of the single crystal silicon by the FZ method or the MCZ method to have a nitrogen concentration of 2.0×10 14 atoms / cm 3 Concentrations of 0.1 to 100% can be achieved.

[0042] In addition, a single crystal silicon substrate having a resistivity of 50 mΩcm or less is prepared as the base wafer.

[0043] The single crystal silicon substrate serving as the base wafer is preferably a single crystal silicon substrate manufactured by the CZ method and having a (100) plane orientation.

[0044] Then, the single crystal silicon substrate to be the bond wafer is, for example, thermally oxidized to form a silicon oxide layer having a thickness of 10 to 400 nm on the surface, preferably a silicon oxide layer having a thickness of 10 to 200 nm.

[0045] Next, the single crystal silicon substrate that will become the bond wafer is superimposed on the single crystal silicon substrate that will become the base wafer via a silicon oxide layer having a thickness of 10 to 400 nm, and bonded by performing a bonding heat treatment at 1150°C for about 2 hours, for example.

[0046] Thereafter, the bond wafer is processed to a thickness of, for example, about 100 to 200 nm to obtain a single crystal silicon thin film. Although the processing method is not particularly limited, a method in which the wafer is peeled off by hydrogen ion implantation and then polished is preferable because it is easy to perform.

[0047] By this processing, for example, as shown in FIG. 1, an SOI substrate 2 can be obtained in which a single crystal silicon thin film 23 is formed on a base wafer (single crystal silicon substrate) 21 with a silicon oxide layer 22 interposed therebetween.

[0048] The SOI substrate 2 thus prepared is used as a starting substrate, and a nitride semiconductor layer including a GaN layer is grown on the SOI substrate 2. For example, as shown in FIG. 2, an AlN layer 31 is first formed to a thickness of, for example, 150 nm, and then an AlGaN layer 32 is formed to a thickness of, for example, 160 nm. Next, a superlattice layer (SLs) 33 is formed by alternately stacking 40 to 60 pairs of GaN layers and AlN layers. Next, a GaN layer 34 having a thickness of, for example, 800 to 1200 nm is formed. Next, a barrier layer made of an AlGaN layer 32 having a thickness of, for example, 3 nm is formed, and a cap layer made of a GaN layer 34 having a thickness of, for example, 3 nm is formed thereon, thereby manufacturing a nitride semiconductor substrate 1 (GaN-HEMT epitaxial growth substrate) 1 having a nitride semiconductor layer 3 formed on an SOI substrate 2 as shown in FIG. 2.

[0049] According to such a method for producing a nitride semiconductor substrate of the present invention, the nitride semiconductor substrate of the present invention can be produced, however, the method for producing the nitride semiconductor substrate of the present invention is not limited to the production method described above.

[0050] In this manner, in the method for manufacturing a nitride semiconductor substrate of the present invention, a nitride semiconductor thin film including an AlN layer 31, a GaN layer 34, and an AlGaN layer 32 is formed on an SOI substrate 2 in which a single crystal silicon thin film is formed on a single crystal silicon substrate serving as a base wafer via a silicon oxide layer. 14 atoms / cm 3 By using a nitride semiconductor substrate containing the nitride semiconductor layer at a concentration of 0.1 or more and having a resistivity of 100 Ωcm or more, a single crystal silicon substrate serving as a base wafer having a resistivity of 50 mΩcm or less, and a silicon oxide layer having a thickness of 10 to 400 nm, preferably 10 to 200 nm, it is possible to produce a nitride semiconductor substrate which has a relatively high strength despite its high resistivity, is applicable particularly to high frequency devices having good high frequency characteristics, and in which plastic deformation is suppressed. EXAMPLES

[0051] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these.

[0052] Example 1 As shown in FIG. 2, a nitride semiconductor layer 3 having a thickness of 1.8 μm was epitaxially grown on an SOI substrate 2 to obtain a nitride semiconductor substrate (GaN-HEMT substrate) 1 of Example 1.

[0053] At that time, as the SOI substrate 2, an SOI substrate having a diameter of 150 mm and satisfying the following conditions was used.

[0054] The bond wafer is a single crystal silicon substrate (bond substrate) that is doped with nitrogen and manufactured by the MCZ method. The surface orientation is (111) and the nitrogen is 5×10 14 atoms / cm 3 A single crystal silicon substrate having a resistivity of 1200 Ωcm was prepared.

[0055] As a single crystal silicon substrate (Base substrate) serving as a base wafer, a single crystal silicon substrate manufactured by the CZ method, having a surface orientation of (100), a resistivity of 8 mΩcm, and a thickness of 675 μm was prepared.

[0056] The prepared bond wafer was thermally oxidized to form a silicon oxide layer having a thickness of 200 nm on the surface of the bond wafer.

[0057] Next, hydrogen ions were implanted into the bond wafer through the oxide film to form a bubble layer, and then the bond wafer was superimposed on the single crystal silicon substrate that would become the base wafer via the silicon oxide layer. After that, a heat treatment was performed to separate the bond wafer at the bubble layer, and then a bonding heat treatment was performed at 1150°C for 2 hours to bond the wafer.

[0058] Thus, nitrogen is 5 × 10 14 atoms / cm 3 A single crystal silicon thin film (SOI layer) having a resistivity of 1200 Ωcm and a thickness of 100 nm was obtained.

[0059] By this processing, as shown in FIG. 1, an SOI substrate 2 was obtained in which a single crystal silicon thin film 23 was formed on a base wafer (single crystal silicon substrate) 21 via a silicon oxide layer (BOX layer) 22.

[0060] In Example 1, the nitride semiconductor layer 3 was formed by epitaxial growth on the SOI substrate 2 obtained as described above, in the procedure previously described with reference to FIG.

[0061] Comparative Example 1 A nitride semiconductor substrate of Comparative Example 1 was obtained in the same manner as in Example 1, except that a single crystal silicon substrate produced by the FZ method without doping nitrogen and having a surface orientation of (111) and a resistivity of 5535 Ωcm was used as a single crystal silicon substrate to be a bond wafer.

[0062] Comparative Example 2 A nitride semiconductor substrate of Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except that the prepared bond wafer was thermally oxidized to form a silicon oxide layer having a thickness of 400 nm on the surface of the bond wafer.

[0063] Example 2 A nitride semiconductor substrate of Example 2 was obtained in the same manner as in Example 1, except that the prepared bond wafer was thermally oxidized to form a silicon oxide layer having a thickness of 400 nm on the surface of the bond wafer.

[0064] Comparative Example 3 A nitride semiconductor substrate of Comparative Example 3 was obtained in the same manner as in Comparative Example 1, except that the prepared bond wafer was thermally oxidized to form a silicon oxide layer having a thickness of 650 nm on the surface of the bond wafer.

[0065] Comparative Example 4 A nitride semiconductor substrate of Comparative Example 4 was obtained in the same manner as in Example 1, except that the prepared bond wafer was thermally oxidized to form a silicon oxide layer having a thickness of 650 nm on the surface of the bond wafer.

[0066] Comparative Example 5 The nitride semiconductor substrate of Comparative Example 5 was obtained by the same procedure as in Comparative Example 4, except that a single crystal silicon substrate was used as the base wafer, the single crystal silicon substrate being manufactured by the CZ method, having a surface orientation of (100), a resistivity of 8 mΩcm, a thickness of 675 μm, and having a backside CVD oxide film of 600 nm formed on the surface opposite to the surface to be bonded to the bond wafer.

[0067] Comparative Example 6 A nitride semiconductor substrate of Comparative Example 6 was obtained in the same manner as in Comparative Example 4, except that the thickness of the single crystal silicon thin film was 200 nm.

[0068] Table 1 below shows details of the SOI substrates and the warpage after epitaxial growth of the nitride semiconductor layer for Examples 1 and 2 and Comparative Examples 1 to 6.

[0069] [Table 1]

[0070] As is clear from the results shown in Table 1, in the nitride semiconductor substrates of Examples 1 and 2, the warpage after epitaxial growth was within ±50 μm, which is the general device input standard, and plastic deformation was found to be sufficiently suppressed.

[0071] On the other hand, the single crystal silicon substrate to be the bond wafer was prepared by adding 5×10 14 atoms / cm 3 In the nitride semiconductor substrates of Comparative Examples 1 and 2 in which the nitride semiconductor substrate containing no SiO 2 at a concentration was not used, the warpage after epitaxial growth exceeded ±50 μm, indicating that plastic deformation was not sufficiently suppressed.

[0072] Furthermore, in the nitride semiconductor substrates of Comparative Examples 3 to 6 in which a silicon oxide layer having a thickness exceeding 400 nm was used, the warpage after epitaxial growth exceeded ±50 μm, indicating that plastic deformation was not sufficiently suppressed.

[0073] Example 3 A nitride semiconductor substrate of Example 3 was obtained in the same manner as in Example 1, except that a single crystal silicon substrate manufactured by the CZ method, having a surface orientation of (100), a resistivity of 8 mΩcm, and a thickness of 1000 μm was used as a single crystal silicon substrate serving as a base wafer.

[0074] Example 4 The bond wafer was made of single crystal silicon substrate doped with nitrogen by the FZ method, with a surface orientation of (111) and a nitrogen concentration of 5×10 14 atoms / cm 3 A nitride semiconductor substrate of Example 4 was obtained in the same manner as in Example 1, except that a single crystal silicon substrate was used that contained ZnO at a concentration of 1000 nm and had a resistivity of 3552 Ωcm. That is, in Example 4, a silicon oxide layer having a thickness of 200 nm was used, as in Example 1.

[0075] Example 5 A nitride semiconductor substrate of Example 5 was obtained in the same manner as in Example 4, except that the prepared bond wafer was thermally oxidized to form a silicon oxide layer having a thickness of 400 nm on the surface of the bond wafer.

[0076] Comparative Example 7 A nitride semiconductor substrate of Comparative Example 7 was obtained in the same manner as in Example 4, except that the prepared bond wafer was thermally oxidized to form a silicon oxide layer having a thickness of 650 nm on the surface of the bond wafer.

[0077] Table 2 below shows details of the SOI substrates and the warpage after epitaxial growth of the nitride semiconductor layer for Examples 3 to 5 and Comparative Example 7.

[0078] [Table 2]

[0079] FIG. 3 shows a part of log data obtained by measuring the warpage state during epitaxial growth in Examples 1 and 3 and Comparative Examples 3 and 6 using curvature.

[0080] As shown in FIG. 3, Comparative Example 3 and Comparative Example 6, in which the silicon oxide layer has a thickness of 650 nm, are significantly plastically deformed at about 2 hours and 40 minutes.

[0081] On the other hand, it can be seen from FIG. 3 that in Examples 1 and 3, the warpage of the substrate during epitaxial growth was suppressed more effectively than in Comparative Examples 3 and 6.

[0082] FIG. 4 shows the relationship between the thickness of the silicon oxide layer and the warpage in the examples and the comparative examples.

[0083] Specifically, the square plots and the dotted approximation curve show the change in warpage when the thickness of the silicon oxide layer (BOX) is changed to 200 nm (Example 1), 400 nm (Example 2), and 650 nm (Comparative Example 4) using a bond wafer manufactured and prepared by the MCZ method.

[0084] The circle plots and the dashed approximation curves show the change in warpage when the thickness of the silicon oxide layer (BOX) is changed to 200 nm (Example 4), 400 nm (Example 5), and 650 nm (Comparative Example 7) using a bond wafer manufactured and prepared by the FZ method.

[0085] As can be seen from FIG. 4, regardless of whether the bond wafer was manufactured by the MCZ method or the FZ method, in the examples in which the silicon oxide layer (BOX layer) thickness was 400 nm or less, the warpage was 50 μm or less, which is significantly suppressed compared to the comparative example in which the silicon oxide layer thickness was 650 nm.

[0086] 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]

[0087] 1...nitride semiconductor substrate (GaN-HEMT substrate), 2...SOI substrate, 3...nitride semiconductor layer (nitride semiconductor thin film), 21...single crystal silicon substrate (Base substrate), 22...silicon oxide layer (BOX layer), 23...single crystal silicon thin film (SOI layer), 31...AlN layer, 32...AlGaN layer, 33...superlattice layer, 34...GaN layer.

Claims

1. A high frequency nitride semiconductor substrate, an SOI substrate in which a single crystal silicon thin film is formed on a single crystal silicon substrate via a silicon oxide layer; a nitride semiconductor layer including a GaN layer formed on the SOI substrate; Including, The single crystal silicon thin film is doped with nitrogen at a concentration of 2.0×10 １４ atoms / cm ３ or more, and the resistivity is 100 Ω cm or more, The single crystal silicon substrate has a resistivity of 50 mΩcm or less, A nitride semiconductor substrate, wherein the silicon oxide layer has a thickness of 10 to 400 nm.

2. 2. The nitride semiconductor substrate according to claim 1, wherein the silicon oxide layer has a thickness of 10 to 200 nm.

3. A method for manufacturing a high frequency nitride semiconductor substrate, comprising the steps of: Preparing two single crystal silicon substrates to be a bond wafer and a base wafer; bonding the two single crystal silicon substrates together via a silicon oxide layer; a step of thinning the bond wafer to form a single crystal silicon thin film, thereby obtaining an SOI substrate in which the single crystal silicon thin film is formed on the base wafer via the silicon oxide layer; growing a nitride semiconductor layer including a GaN layer on the single crystal silicon thin film of the SOI substrate to obtain a nitride semiconductor substrate in which the nitride semiconductor layer is formed on the single crystal silicon thin film; Including, The single crystal silicon substrate to be the bond wafer was doped with nitrogen at a concentration of 2.0×10 １４ atoms / cm ３ or more and has a resistivity of 100 Ω cm or more, The single crystal silicon substrate to be the base wafer has a resistivity of 50 mΩcm or less, A method for producing a nitride semiconductor substrate, wherein the silicon oxide layer has a thickness of 10 to 400 nm.

4. 4. The method for producing a nitride semiconductor substrate according to claim 3, wherein the silicon oxide layer has a thickness of 10 to 200 nm.

5. 5. The method for producing a nitride semiconductor substrate according to claim 3, wherein the single crystal silicon substrate to be the bond wafer is prepared by producing the single crystal silicon substrate by an FZ method or an MCZ method.

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