METHOD FOR MANUFACTURING GaN EPITAXIAL FILM AND METHOD FOR MANUFACTURING SEMICONDUCTOR DEVICE

Abstract

To provide a method for manufacturing a GaN epitaxial film, capable of manufacturing a GaN thick film having a dislocation density of 1.0×106 / cm2 or less at low cost without warps or cracks in spite of a large diameter by a simple process.SOLUTION: A method for manufacturing a GaN epitaxial film comprising: a preparation step of preparing a support substrate having a diameter of 150 mm or more, having a core consisting of nitride ceramics and sealed by a sealing layer and having a thickness of less than 1 mm; a substrate manufacturing step of laminating a planarization layer and a seed crystal layer consisting of a SiC single crystal in this order on the support substrate to obtain a substrate for epitaxial growth; and an epitaxial step of growing a GaN epitaxial film having a thickness of 7 μm or more on the substrate for epitaxial growth can manufacture a GaN epitaxial film having a dislocation density of 1.0×106 / cm2 or less.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for producing a GaN epitaxial film and a method for producing a semiconductor device. [Background technology]

[0002] Si, GaAs, and Sap (sapphire) bulk substrates are promising as substrates for forming GaN epitaxial films because they can provide large diameter substrates and are inexpensive, but when attempting to grow a thick epitaxial film to reduce dislocations in the epitaxial film, problems arise such as substrate warping and cracks. In addition, if one tries to overcome these problems, the buffer process becomes very complicated, lowering productivity.

[0003] On the other hand, GaN and AlN bulk substrates, which have similar thermal expansion coefficients and lattice constants, are promising in terms of physical properties, but they cannot be mass-produced with a diameter of 150 mm or more and are expensive. As in Patent Document 1, there is a method of creating a GaN film with low dislocation density on a heterogeneous substrate by the VAS (Void-Assisted Separation) method and using this as a substrate, but it is unclear whether it can be made into a large diameter, and the process is complicated. Also, in Non-Patent Document 1, there is an example of improving the high defect density of GaN on Si substrates by using GaN on GaN, but it is unclear whether it can be made into a large diameter.

[0004] As in Patent Documents 2 and 3, if a substrate with a ceramic core with approximately the same thermal expansion coefficient as the crystal to be formed is used, a thick film can be formed. However, due to the difference in lattice constant between the seed crystal of Si or the like and the crystal to be formed, the crystal may grow to a thickness of 1.0 × 10 6 / cm 2 It is difficult to achieve a dislocation density below this value.

[0005] When a substrate having a ceramic core is used, a vertical transistor can be produced by separating the support substrate containing the ceramic core by ion implantation as described in Patent Document 4. In addition, an ultraviolet emitting element can be produced by separating the support substrate containing the ceramic core by etching the planarizing layer (SiO2 layer) as described in Patent Document 5.

[0006] Furthermore, Patent Documents 4 and 6 describe that, in addition to Si, SiC, AlN, AlGaN, Al2O3, and the like can be used for the single crystal layer on the support substrate containing a ceramic core, and that those with similar lattice constants are preferable, but there is no description as to whether the dislocation density can be reduced.

[0007] Epitaxial Lateral Overgrowth (ELO) is also known as a means for reducing dislocation density. For example, Patent Documents 7 and 8 describe ELO growth using island-shaped SiN on the support substrate of Patent Document 2. Patent Documents 9 and 10 describe the concept of reducing dislocations by growing GaN in two island-like stages on a Si-containing film containing island-shaped SiN, and growing it in an ELO manner, with the Si (doping) concentration of the two-stage island-shaped growth portion of GaN being 1.0×10 17 ~10 20 / cm 3 There is a description:

[0008] In Patent Document 11, there is a description that no mask such as SiN is used, and island-shaped GaN is grown under growth conditions to reduce dislocations by ELO growth, and a TD (threading dislocation) density of 5.0×10 6 / cm 2 , 5.0 × 10 for 3 times 5 / cm 2 It has been described that a GaN film having the above structure can be obtained.

[0009] However, these techniques involve forming ELO on silicon, and multiple ELO steps are required to reduce the dislocation density.

[0010] As a means for reducing dislocation density, a method is known in which dislocations are reduced by forming a film composed of inclined planes as an underlayer, instead of growing the (0001) plane, through which dislocations from below tend to propagate as is, and a mask such as island-shaped SiN is used (Patent Document 1, Patent Documents 12-13), or the growth of an inclined plane film is achieved by adjusting the growth conditions without pattern processing such as a mask layer (Patent Documents 14-17). The substrate used is a GaN free-standing substrate that was once fabricated by the VAS method on a substrate such as Si, GaAs, or Sap. However, it is unclear whether it is possible to increase the diameter. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2020-070229 A [Patent Document 2] JP 2013-177285 A [Patent Document 3] Special Publication No. 2019-523994 [Patent Document 4] International Publication No. 2021 / 230148 [Patent Document 5] JP 2022-056492 A [Patent Document 6] Patent Publication No. 2022-012558 [Patent Document 7] JP 2022-165964 A [Patent Document 8] Special Publication No. 2020-505767 [Patent Document 9] JP 2018-88528 A [Patent Document 10] JP 2015-29042 A [Patent Document 11] JP 2016-41654 A [Patent Document 12] JP 2020-070230 A [Patent Document 13] JP 2020-033210 A [Patent Document 14] JP 2020-033211 A [Patent Document 15] JP 2020-033212 A [Patent Document 16] JP 2020-033253 A [Patent Document 17] JP 2020-033254 A [Non-patent literature]

[0012] [Non-Patent Document 1] Odyssey Semiconductor, Inc. "Defects Matter", Odyssey Semiconductor, Inc., 2023, [Retrieved May 17, 2023], Internet<URL: https: / / odysseysemi.com / technology / > Summary of the Invention [Problem to be solved by the invention]

[0013] As described above, various technologies have been proposed for thickening epitaxial layers, increasing their diameter, and reducing dislocation density; however, there was no low-cost, simple method for manufacturing GaN epitaxial films that could increase their diameter, prevent the occurrence of warping and cracks during thickening, and reduce dislocation density.

[0014] The present invention has been made to solve the above problems, and provides a method for manufacturing a large-diameter quartz crystal having no warping or cracks and a dislocation density of 1.0×10 6 / cm 2 The objective of the present invention is to provide a method for producing a GaN epitaxial film by a simple process at low cost to produce the following GaN thick film: Another object of the present invention is to provide a method for manufacturing semiconductor devices that can produce high-quality semiconductor devices at low cost. [Means for solving the problem]

[0015] The present invention has been made to achieve the above object, and is a method for producing a GaN epitaxial film, comprising the steps of: a preparation step of preparing a support substrate having a diameter of 150 mm or more and a thickness of less than 1 mm, the support substrate having a core made of nitride ceramic sealed with a sealing layer; a substrate production step of sequentially laminating a planarizing layer and a seed crystal layer made of a SiC single crystal on the support substrate to obtain a substrate for epitaxial growth; and an epitaxial step of growing a GaN epitaxial film having a thickness of 7 μm or more on the substrate for epitaxial growth, thereby achieving a dislocation density of 1.0×10 6 / cm 2 The present invention provides a method for producing a GaN epitaxial film, which is characterized by producing the above-mentioned GaN epitaxial film as follows.

[0016] According to such a method for manufacturing a GaN epitaxial film, by growing the GaN epitaxial film on an epitaxial growth substrate containing a ceramic core, it is possible to manufacture a thick GaN film, unlike bulk substrates such as Si, Sap, and GaAs, on which inexpensive, large-diameter products exist but on which thick GaN epitaxial films cannot be formed due to differences in thermal expansion coefficients. Furthermore, if such a thick film with low dislocations can be manufactured, the crystallinity of the device layer will be good, which will improve the breakdown voltage and reduce leakage current in electronic devices, and will also contribute to energy conservation by enabling higher output or higher efficiency in visible and ultraviolet light devices.

[0017] In addition, according to this method for producing a GaN epitaxial film, the single crystal layer on the support substrate is made into a SiC single crystal. SiC is a material with a lattice constant closer to that of GaN than Si, and is available at a low cost and with a large diameter compared to other crystal layers such as GaN and AlN that can be used to produce high-quality GaN epitaxial films. Therefore, it is possible to produce SiC single crystals without warping or cracking in a simple process, with a dislocation density of 1.0×10 6 / cm 2 The following GaN epitaxial films can be formed:

[0018] Furthermore, by using a support substrate with a diameter of 150 mm or more, a GaN epitaxial film with a large diameter can be formed.

[0019] In addition, inexpensive, large-diameter products exist that can be manufactured by growing the GaN epitaxial film to a thickness of 7 μm or more. However, this makes it possible to achieve an epitaxial film thickness that cannot be formed on bulk substrates such as Si, Sap, and GaAs, on which thick GaN epitaxial films cannot be formed due to differences in thermal expansion coefficients.

[0020] Furthermore, by making the thickness of the support substrate less than 1 mm, it is possible to pass the CMOS lines for conventional silicon epitaxial wafers. For example, in GaN on Si substrate devices, due to problems such as warping and cracking caused by differences in thermal expansion coefficients, Si substrates of the normal standard thickness cannot be used and a thick substrate of 1 mm or more must be used by bonding or other methods, which makes it impossible to pass the CMOS lines of conventional silicon, but with the present invention, the CMOS lines can be passed through.

[0021] Therefore, even with a large diameter, there is no warping or cracking, and the dislocation density is 1.0×10 6 / cm 2 The following GaN thick films can be produced at low cost using a simple process:

[0022] In this case, the epitaxial process may include a formation step of forming an island-shaped SiN layer, an ELO step of growing a GaN layer using the SiN layer as a mask, and then a growth step of growing a GaN epitaxial film on the topmost SiN layer or GaN layer.

[0023] This makes it possible to further reduce the dislocation density in the GaN epitaxial film.

[0024] At this time, in the epitaxial process, the formation step and the ELO step can be performed alternately.

[0025] This can further reduce the dislocation density of the GaN epitaxial layer compared to performing the formation step and the ELO step once each.

[0026] In this case, the SiC single crystal may have an off angle of 0° to 4°.

[0027] This allows the Group III nitride epitaxial film to be grown in a step-flow mode.

[0028] The present invention also provides a method for manufacturing a semiconductor device, comprising the steps of: fabricating a device on a GaN epitaxial film manufactured by the above-described method for manufacturing a GaN epitaxial film; and then separating the device from the supporting substrate by etching the planarization layer.

[0029] According to this method of manufacturing a semiconductor device, a semiconductor device having a large diameter can be manufactured without warping or cracking, and with a dislocation density of 1.0×10 6 / cm 2 The following GaN thick films are epitaxially produced by a simple process at low cost, and devices are fabricated on the epitaxial films, making it possible to manufacture high-quality semiconductor devices at low cost without warping or cracks.

[0030] Furthermore, by separating the insulating support substrate portion by etching the planarization layer between the support substrate and the epitaxial film, it is possible to use only the conductive GaN film in the semiconductor device. Even if an insulating support substrate portion is present, the device fabrication process can be simplified in vertical devices that require current to flow vertically by supplying electricity from the back surface of the substrate. Effect of the Invention

[0031] As described above, according to the method for producing a GaN epitaxial film of the present invention, it is possible to produce a GaN epitaxial film having a large diameter, but without warping or cracks, and with a dislocation density of 1.0×10 6 / cm 2 It is possible to produce the following GaN thick films at low cost using a simple process. Furthermore, according to the method for manufacturing a semiconductor device of the present invention, a high-quality semiconductor device can be manufactured at low cost. [Brief description of the drawings]

[0032] [Figure 1] 1 shows an epitaxial substrate on which a GaN epitaxial film is formed, the epitaxial film being obtained by a method for producing a GaN epitaxial film according to an embodiment of the present invention. [Diagram 2] An example of a method for producing a GaN epitaxial film and a method for producing a semiconductor device using the produced epitaxial film will be described. [Diagram 3] 1 shows a device using a GaN epitaxial film of the present invention. [Figure 4] 1 shows a device using a GaN epitaxial film of the present invention. [Diagram 5] 1 shows the epitaxial film of Example 1. [Figure 6] The manufacturing procedure of the epitaxial film and the semiconductor device of Example 2 will be described. [Figure 7] The manufacturing procedure of the epitaxial film and the semiconductor device of Example 2 will be described. [Figure 8] The manufacturing procedure of the epitaxial film and the semiconductor device of Example 3 will be described. [Figure 9] 1 shows a cross-sectional photograph of the epitaxial film of Example 3. [Figure 10] The manufacturing procedure of the epitaxial film and the semiconductor device of Example 4 will be described. [Figure 11] The manufacturing procedure of the epitaxial film and the semiconductor device of Example 5 will be described. [Figure 12] The manufacturing procedure of the epitaxial film and the semiconductor device of Example 6 will be described. [Figure 13] The manufacturing procedure of the epitaxial film and the semiconductor device of Comparative Example 1 will be described. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The present invention will be described in detail below, but the present invention is not limited thereto.

[0034] As mentioned above, even with a large diameter, there is no warping or cracking, and the dislocation density is 1.0×10 6 / cm 2There has been a demand for a method for producing a GaN epitaxial film at low cost using a simple process to produce the following GaN thick films:

[0035] As a result of intensive research by the inventors into the above-mentioned problems, the present inventors have discovered a method for producing a GaN epitaxial film, comprising the steps of: a preparation step of preparing a support substrate having a diameter of 150 mm or more and a thickness of less than 1 mm, the support substrate having a core made of nitride ceramic sealed with a sealing layer; a substrate production step of sequentially laminating a planarizing layer and a seed crystal layer made of a SiC single crystal on the support substrate to obtain a substrate for epitaxial growth; and an epitaxial step of growing a GaN epitaxial film having a thickness of 7 μm or more on the substrate for epitaxial growth, thereby achieving a dislocation density of 1.0×10 6 / cm 2 The GaN epitaxial film manufacturing method described below, which is characterized by manufacturing the GaN epitaxial film, has a large diameter but is free of warping and cracks and has a dislocation density of 1.0 × 10 6 / cm 2 The present invention was completed based on the discovery that the following GaN thick film can be produced at low cost by a simple process.

[0036] As described above, there has also been a demand for a method of manufacturing semiconductor devices that can produce high-quality semiconductor devices at low cost.

[0037] As a result of extensive investigations into the above-mentioned problems, the inventors have found that a high-quality semiconductor device can be manufactured at low cost by a semiconductor device manufacturing method, which comprises fabricating a device on a GaN epitaxial film manufactured by the above-described GaN epitaxial film manufacturing method, and then etching the planarization layer to separate the device from the supporting substrate, thereby completing the present invention.

[0038] The following description will be given with reference to the drawings. Hereinafter, a method for producing a GaN epitaxial film according to an embodiment of the present invention will be described with reference to FIGS.

[0039] First, a GaN epitaxial film obtained by a method for producing a GaN epitaxial film according to an embodiment of the present invention will be described with reference to Fig. 1. Here, a film for a vertical power device (MOS-FET) is exemplified as the GaN epitaxial film.

[0040] As shown in Fig. 1, GaN epitaxial film 112 is formed on epitaxial growth substrate 109. Epitaxial growth substrate 109 serves as a base on which GaN epitaxial film 112 grows, and also serves as a support member for preventing deformation, such as warping, of GaN epitaxial film 112. In the following explanation, GaN epitaxial film 112 formed on epitaxial growth substrate 109 as shown in Fig. 1 will be referred to as epitaxial substrate 1.

[0041] The epitaxial growth substrate 109 includes a support substrate 100, a planarizing layer 105, and a seed crystal layer 107. In Fig. 1, a buffer layer 111 is formed on the epitaxial growth substrate 109, and an ELO layer 113 is further formed on the buffer layer 111.

[0042] Support substrate 100 is a support member for preventing deformation of GaN epitaxial film 112 , and includes core 101 and sealing layer 103 . The core 101 is a layer that forms the base of the support substrate 100, and is made of, for example, nitride ceramics such as AlN. The sealing layer 103 is a layer that covers the periphery (both sides) of the core 101 to prevent the diffusion of impurities, and is, for example, SiO2, SiN, or a mixture thereof, with SiN being preferred. The thickness of the coating is, for example, about 200 nm.

[0043] The planarizing layer 105 is a layer that flattens unevenness resulting from the outer shapes of the core 101 and the sealing layer 103. The planarizing layer 105 is also a portion that is removed by etching when the GaN epitaxial film 112 is separated from the epitaxial growth substrate 109 after a device is formed on the GaN epitaxial film 112. The planarizing layer 105 contains, for example, any one of silicon oxide, silicon oxynitride, and aluminum arsenide, and more specifically, is silicon oxide (SiO2). The planarizing layer 105 is provided at least on the side where the seed crystal layer 107 is bonded, but may be provided so as to encompass the entire substrate, or may be provided on both sides of the substrate.

[0044] The seed crystal layer 107 is a layer on which the GaN epitaxial film 112 grows, and is made of SiC single crystal. SiC is a material with a lattice constant closer to that of GaN than Si, and is available at a low cost and with a large diameter compared to other crystal layers such as GaN and AlN that can be used to manufacture high-quality GaN epitaxial films. Therefore, SiC can be manufactured by a simple process without warping or cracks, and with a dislocation density of 1.0×10 6 / cm 2 The following GaN epitaxial films can be formed:

[0045] The crystal structure of the SiC single crystal is not particularly limited, and examples include 6H-SiC, 4H-SiC, 3C-SiC, etc. For example, 4H-SiC is suitable for use in electronic devices, and 6H-SiC and 4H-SiC are suitable for use in visible and ultraviolet light devices.

[0046] The buffer layer 111 is a layer that is provided as necessary when it is desired to alleviate mismatch caused by the difference in lattice constant between the seed crystal layer 107 and the GaN epitaxial film 112 and stress on the GaN epitaxial film 112, and is made of, for example, AlN or AlGaN.

[0047] The ELO layer 113 is a layer that reduces dislocation density when the GaN epitaxial film 112 is epitaxially grown, and is formed as necessary when it is desired to further reduce the dislocation density. The ELO layer 113 comprises a SiN layer 110 and a GaN layer 115 . The SiN layer 110 is an island-like layer that serves as a mask when the GaN layer 115 grows. The GaN layer 115 is a layer of GaN that grows from gaps that are not masked by the SiN layer 110, and the SiN layer 110 regulates the growth direction during growth, thereby bending the direction of dislocations and reducing dislocations that reach the GaN epitaxial film 112. The density and size of the island-like SiN layer 110 can be adjusted as appropriate depending on the device application. Although the characteristics of the SiN layer 110 are conceptually and typically illustrated in FIG. 1, the SiN layer 110 is shown in a layered shape in the following figures for convenience.

[0048] The GaN epitaxial film 112 is a single crystal layer on which a semiconductor device is formed. The composition of the GaN epitaxial film 112 is not limited to GaN, but includes other group III nitrides such as InN and AlN and their mixed crystals. The composition, structure, and conductivity type of the GaN epitaxial film 112 may be appropriately selected depending on the device to be formed, and the GaN epitaxial film 112 may be multi-layered. FIG. 1 illustrates a stacked structure of an n-GaN layer 118, a p-GaN layer 122, and a GaN layer 123. The above is the description of the GaN epitaxial film 112.

[0049] Next, an example of a method for manufacturing GaN epitaxial film 112 and a method for manufacturing a semiconductor device using the manufactured GaN epitaxial film 112 will be described with reference to FIG.

[0050] First, a support substrate 100 having a diameter of 150 mm or more and a thickness of less than 1 mm, in which a core 101 made of nitride ceramic is sealed with a sealing layer 103 as shown in FIG. 1, is prepared (S1 in FIG. 2: preparation step). If the diameter is less than 150 mm, the diameter of GaN epitaxial film 112 will also be less than 150 mm, making it impossible to increase the diameter.

[0051] Furthermore, if the thickness is 1 mm or more, the thickness of the epitaxial substrate 1 will be 1 mm or more, and even if one tries to input it into a conventional silicon CMOS line or the like to form a device in the GaN epitaxial film 112, it will be too thick to pass through the line.

[0052] More preferably, the thickness of the support substrate 100 is within the JEITA or SEMI Si substrate thickness standard, so that conventional silicon CMOS lines can be passed through reliably.

[0053] Next, a flattening layer 105 and a seed crystal layer 107 made of a SiC single crystal are laminated in this order on the support substrate 100 shown in FIG. 1 to obtain a substrate 109 for epitaxial growth (S2 in FIG. 2: substrate manufacturing step).

[0054] A specific method for forming the planarization layer 105 is to form an oxide film such as SiO2 on the surface of the support substrate 100 by plasma CVD, LPCVD, low-pressure MOCVD, or the like, and then perform a thermal stabilization process, and then polish and smooth the surface by a known polishing method such as CMP. The thickness of the planarization layer 105 after polishing is, for example, 0.05 μm to 3.0 μm.

[0055] An example of a method for forming the seed crystal layer 107 is a method for transferring the surface layer of a SiC single crystal substrate. Specifically, hydrogen ions are first implanted into the C-face side of a SiC single crystal substrate fabricated by sublimation to form a split interface in advance. Next, the C-face side of the SiC single crystal substrate into which hydrogen ions have been implanted is bonded to the planarization layer 105. At this time, voids can be eliminated by performing a surface activation process as necessary.

[0056] Next, a split heat treatment is performed on the SiC single crystal substrate while it is bonded to the planarization layer 105, whereby peeling occurs starting from the hydrogen ion implantation layer, and the surface layer of the SiC single crystal substrate is transferred to the planarization layer 105, with the split interface appearing as the surface. Then, surface polishing such as CMP, or wet or dry etching is performed to remove the damaged layer caused by the peeling.

[0057] It is preferable to use a SiC single crystal having an off-angle of 0° to 4° for the seed crystal layer 107. This allows the Group III nitride epitaxial film formed on the seed crystal layer 107 to grow in a step-flow mode. If a lower off-angle is required depending on the circumstances, a 0° off substrate may be cut out from a 4° off substrate and used.

[0058] The thickness of seed crystal layer 107 is, for example, not less than 0.04 μm and not more than 1.0 μm, but is appropriately set depending on the structure and type of the device to be formed on GaN epitaxial film 112 .

[0059] In addition, the conductivity of the seed crystal layer 107 can be selected to be conductive or non-conductive depending on the structure and type of the device to be formed on the GaN epitaxial film 112. For example, a low resistivity (about 20 mΩcm) or a high resistivity (1.0×10 6 Ωcm or more).

[0060] For example, in a device that requires electrical current to flow vertically through the device layers, the electrodes can be formed either all on the same side as shown in Figure 3, or on the top and bottom surfaces as shown in Figure 4.

[0061] Here, the device layer portion is a collective name for the portion above seed crystal layer 107, and refers to GaN epitaxial film 112, or the portion consisting of buffer layer 111, ELO layer 113, and GaN epitaxial film 112.

[0062] In the device 200 (MOS-FET) shown in Fig. 3, the seed crystal layer 107 is conductive, and the device is used with the epitaxial growth substrate 109 attached. In this case, the seed crystal layer 107 is used to form a drain electrode, so the seed crystal layer 107 is preferably thicker in order to reduce the lateral resistance, and is preferably 300 nm or thicker, for example. In order to facilitate ohmic contact, the resistivity of the seed crystal layer 107 is preferably reduced to about 0.01 to 0.03 Ωcm.

[0063] On the other hand, the device 201 (MOS-FET) shown in Fig. 4 is a case where the seed crystal layer 107 has high resistivity, semi-insulation, or insulation, and after forming a device on the GaN epitaxial film 112, only the device layer portion is separated for use as a device. In this case, the seed crystal layer 107 is preferably thin since it will be removed, and preferably less than 300 nm, for example. Note that if the seed crystal layer 107 is conductive, there is no need to remove the seed crystal layer 107, and therefore the device can be used in the electrode formation type of Fig. 4 with the seed crystal layer 107 remaining under the device layer portion. For devices such as RF devices where it is not desired to pass current underneath, a semi-insulating seed crystal layer 107 is desirable.

[0064] Next, as necessary, a buffer layer 111 is formed on the seed crystal layer 107 (S3 in FIG. 2). The buffer layer 111 can be formed, for example, by MOCVD.

[0065] Next, the ELO layer 113 is formed as necessary. Specifically, a formation step (S4 in FIG. 2) of forming island-shaped SiN layer 110 and an ELO step (S5 in FIG. 2) of growing GaN layer 115 using SiN layer 110 as a mask are performed. This can further reduce the dislocation density in the GaN epitaxial film.

[0066] The formation step and the ELO step may be alternately performed as necessary to form multiple SiN layers 110 and GaN layers 115. This can further reduce the dislocation density of the GaN epitaxial film 112 compared to performing the formation step and the ELO step once each.

[0067] Thereafter, GaN epitaxial film 112 is grown (S6 in FIG. 2: growth step). GaN epitaxial film 112 is formed on the outermost SiN layer 110 or GaN layer 115 when the formation step and ELO step have been performed, and is formed on buffer layer 111 when the formation step and ELO step have not been performed and buffer layer 111 has been formed. GaN epitaxial film 112 is formed on seed crystal layer 107 when the formation step and ELO step have not been performed and buffer layer 111 has not been formed.

[0068] The surface of the seed crystal layer 107 on which the epitaxial growth is performed is preferably a Si surface which tends to make the epitaxial layer flat, but may be a C surface. Steps S3 to S6 are collectively referred to as the epitaxial process. The above is a description of the method for producing the GaN epitaxial film 112.

[0069] Next, a method for manufacturing a semiconductor device using GaN epitaxial film 112 manufactured by the method for manufacturing GaN epitaxial film 112 will be described.

[0070] First, a desired device is fabricated on the GaN epitaxial film 112 (S7 in FIG. 2). Fabrication of the device includes changing the conductivity type by ion implantation or the like, and forming an insulating layer and electrodes by sputtering or the like.

[0071] Here, when seed crystal layer 107 and supporting substrate 100 are not separated from GaN epitaxial film 112 even after a device is formed on GaN epitaxial film 112, such as device 200 shown in FIG. 3, the device is completed through the above steps.

[0072] On the other hand, when the support substrate 100 is to be separated from the GaN epitaxial film 112 even after a device is formed on the GaN epitaxial film 112, as in the case of device 201 shown in Fig. 4, the device is separated from the support substrate 100 by etching the planarizing layer 105 (S8 in Fig. 2). There are no particular limitations on the etchant as long as it dissolves the planarizing layer 105, but when the planarizing layer 105 is SiO2, an HF (hydrogen fluoride) solution can be used as an example.

[0073] During the separation, not only the planarizing layer 105 but also the seed crystal layer 107 and the buffer layer 111 may be removed. The above is a description of the method for manufacturing a semiconductor device. In addition, the semiconductor device to be manufactured is not particularly limited, but examples thereof include LED, LD (laser diode), PD (photodiode), HEMT (high mobility field effect transistor), FET, HBT, and the like. EXAMPLES

[0074] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

[0075] Example 1: Epitaxial substrate for vertical devices First, a GaN epitaxial film 112 was grown in the following manner to produce the epitaxial substrate 1a shown in FIG.

[0076] First, as shown in FIG. 1, a nitride ceramic substrate (AlN) as a core 101 was wrapped with a sealing layer 103, and a silicon oxide layer 105 having a thickness of 0.05 μm to 3.0 μm was provided as a flattening layer 105 on at least the side where a seed crystal layer 107 was to be bonded.

[0077] Next, 4H-SiC (resistivity 20 Ωcm, thickness 0.04 μm to 1.0 μm, epitaxial growth surface is a Si surface with an off angle of 0°) was transferred onto the flattening layer 105 as the seed crystal layer 107. Thereafter, the epitaxial growth substrate 109 was placed in a growth apparatus and heated to a growth temperature (1000 to 1200° C.), and TMA (trimethylaluminum), TMG (trimethylgallium), and NH3 gas were supplied to form a buffer layer 111 on the seed crystal layer 107. 0.2 Ga 0.8 A 0.15 μm thick N layer was formed. 0.2 Ga 0.8 The N layer is doped with 1.0×10 Si as an n-type dopant. 19 atoms / cm 3 Doped it.

[0078] Furthermore, the supply of TMA and TMG was interrupted, and SiH4 and NH3 were supplied to grow the SiN layer 110 on the buffer layer 111 in an island shape with a thickness of 1 nm. After that, the supply of SiH4 was stopped, and TMG was flowed to epitaxially grow the GaN layer 115 to a thickness of 3.0 μm. Then, the Si-doped n-GaN layer 114 was epitaxially grown to a thickness of 7 μm, and further, the Mg-doped p-GaN layer 119 was formed to a thickness of 0.5 μm, and the GaN layer 120 was formed to a thickness of 0.5 μm on the n-GaN layer. As is well known, Mg doped in the GaN layer is often inactivated immediately after epitaxial growth, and in that case, a separate heat treatment is required to activate it as a p-type dopant. In this embodiment, the heat treatment was performed at 1300° C. in a nitrogen atmosphere at normal pressure. In the following embodiments, when a Mg-doped p-GaN layer is described, it should be understood that the same treatment was performed. The epitaxial substrate 1a was produced by the above steps.

[0079] Next, the dislocation density near the surface of the epitaxial substrate 1a was evaluated in an area of ​​20 μm×20 μm at an accelerating voltage of 5 kV using a Hitachi SU-70 electron microscope with a semiconductor backscattered electron detector (PDBSE). As a result, the dislocation density was 7.5×10 5 cm -2 Thus, an epitaxial substrate 1a for a vertical device on which a high-quality GaN epitaxial film was grown could be manufactured. In the III-nitride epitaxial growth layer, dislocations disappear as the growth proceeds, so that the dislocation density in the lower layer (the bottom of the GaN layer 115 or the n-GaN layer 114 in this embodiment) in the early stage of growth is 1.0×10 6 / cm 2 Even if the thickness exceeds 100 μm, the dislocation density decreases rapidly in the upper layer. Therefore, if the epitaxial substrate of the present invention has a GaN epitaxial film of 7 μm or more grown thereon, it is possible to ensure that the epitaxial substrate has the quality required for device performance by evaluating the surface area of ​​the epitaxial substrate.

[0080] Example 2: MOS-FET First, a GaN epitaxial film 112 was grown in the following manner to produce an epitaxial substrate 1b shown in FIG. 6(a).

[0081] First, similarly to Example 1, a nitride ceramic substrate (AlN) as a core 101 was wrapped with a sealing layer 103, and a silicon oxide layer 105 having a thickness of 0.05 μm to 3.0 μm was provided on at least the side where the seed crystal layer 107 was to be bonded.

[0082] Next, 4H—SiC (resistivity 20 Ωcm, thickness 0.04 μm to 1.0 μm, epitaxial growth surface is a Si surface with an off angle of 0°) is transferred onto the flattening layer 105 as the seed crystal layer 107, and Al is grown on the seed crystal layer 107 as the buffer layer 111 in the same manner as in Example 1. 0.2 Ga 0.8 A 0.15 μm thick N layer was formed. 0.2 Ga 0.8 The N layer is doped with 1.0×10 19 atoms / cm 3 Doped it.

[0083] Next, as in Example 1, a SiN layer 110 was grown in an island shape with a thickness of 1 nm on the buffer layer 111, and then a GaN layer 115 was epitaxially grown to a thickness of 2.0 μm. A SiN layer 110 was grown in an island shape with a thickness of 1 nm on top of that, and then a GaN layer 115 was epitaxially grown to a thickness of 1.0 μm. In other words, the number of stacked ELO layers 113 is increased compared to the first embodiment.

[0084] Thereafter, a Si-doped n-GaN layer 114 was epitaxially grown to a thickness of 7 μm, a Mg-doped p-GaN layer 119 was grown to a thickness of 0.5 μm, and a GaN layer 120 was grown thereon to a thickness of 0.5 μm. Through the above steps, an epitaxial substrate 1b was manufactured.

[0085] The dislocation density near the surface of the epitaxial substrate 1b was measured in the same manner as in Example 1, and was found to be 6.0×10 5 cm -2 Thus, an epitaxial substrate 1b for a vertical device on which a high-quality GaN epitaxial film was grown could be manufactured.

[0086] Next, this epitaxial substrate 1b for a vertical device was processed by the following device process to fabricate a vertical power device (MOS-FET). First, as shown in FIG. 6(b), a mask 301 with a predetermined pattern shape was formed on the top surface by photolithography, and n was placed in the opening of the mask 301. + The layer 303 is implanted with ions to form n + A layer 303 was formed.

[0087] Furthermore, as shown in FIG. 6(c), n + A mask 301 having an opening formed therein was formed so that the layer 303 was at the center, and dry etching was performed down to the n-GaN layer 114 .

[0088] Next, as shown in Fig. 6(d), a mask 301 was formed on the dry-etched portion by photolithography, and a SiN film 305 was formed by sputtering. After that, the mask 301 was removed, and a SiO2 film 307 was formed by sputtering, as shown in Fig. 6(e).

[0089] Next, as shown in Fig. 6(f), a mask 301 was formed by photolithography, and then the center of the SiO2 film 307 was etched by dry etching. After that, the mask 301 was removed, and a mask 301 for the gate electrode was formed by photolithography, as shown in Fig. 7(a).

[0090] Furthermore, as shown in Fig. 7(b), a gate electrode 309 was sputtered, and the mask 301 was removed. Next, as shown in Fig. 7(c), a mask 301 was formed by photolithography, and a SiO2 film 311 was formed by sputtering to insulate the gate electrode 309. Furthermore, as shown in Fig. 7(d), after removing the mask 301, a source electrode 313 was sputtered.

[0091] Next, as shown in Fig. 7(e), a mask 301 for element isolation was formed by photolithography, and then dry etching was performed down to the SiO2 layer, which is the planarization layer 105. In Fig. 7(e), the layers above the seed crystal layer 107 are collectively shown as a device layer portion 315 for the sake of simplicity.

[0092] 7(f), the mask 301 was removed, and a temporary support substrate 317 was attached to the device layer portion 315, followed by immersion in an HF solution 319. This dissolved the SiO2 layer that was the planarization layer 105, and separated the device layer portion 315 from the portion below the planarization layer 105.

[0093] Thereafter, as shown in FIG. 7(g), a drain electrode 316 was sputtered on the seed crystal layer 107 on the side of the separated device layer 315, and an ohmic electrode was formed by RTA (Rapid Thermal Anneal) in a nitrogen atmosphere, and then Au320 was sputtered on the surface. In the following examples, when heat treatment is required to obtain ohmic contact of the electrode, it is performed under generally known conditions, and description is omitted. Furthermore, as shown in FIG. 7(h), a metal bond was formed with a substrate on which Au320 was sputtered on the surface of a conductive substrate 321 prepared in advance. Also, as shown in FIG. 7(i), each chip on the side of the separated device layer 315 was picked up and soldered onto a substrate 323 on which an electronic circuit was formed. As a result, a vertical power device (MOS-FET) was formed as a semiconductor device.

[0094] Example 3: SBD (Schottky Barrier Diode) First, HVPE-GaN epitaxial film 401 was grown as GaN epitaxial film 112 in the following procedure to produce epitaxial substrate 1c shown in FIG. 8(a).

[0095] First, similarly to Example 1, a nitride ceramic substrate (AlN) as a core 101 was wrapped with a sealing layer 103, and a silicon oxide layer 105 having a thickness of 0.05 μm to 3.0 μm was provided on at least the side where the seed crystal layer 107 was to be bonded.

[0096] Next, 4H—SiC (resistivity 20 Ωcm, thickness 0.04 μm to 1.0 μm, epitaxial growth surface is a Si surface with an off angle of 0°) is transferred onto the flattening layer 105 as the seed crystal layer 107, and Al is grown on the seed crystal layer 107 as the buffer layer 111 in the same manner as in Example 1. 0.2 Ga 0.8 A 0.15 μm thick N layer was formed. 0.2 Ga 0.8 The N layer is doped with 1.0×10 19 atoms / cm 3 Doped it.

[0097] Next, in the same manner as in Example 1, a SiN layer 110 was grown in an island shape with a thickness of 1 nm on the buffer layer 111, and then a GaN layer 115 was epitaxially grown to a thickness of 3.4 μm. Thereafter, a SiN layer 110 was grown in an island shape with a thickness of 1 nm, and further a GaN layer 115 was epitaxially grown to a thickness of 2.1 μm.

[0098] Thereafter, HVPE-GaN epitaxial film 401 was epitaxially grown to a thickness of 19 μm by HVPE (Hydride Vapor Phase Epitaxy). Through the above steps, epitaxial substrate 1c was manufactured.

[0099] The dislocation density near the surface of the HVPE-GaN epitaxial film 401 was measured in the same manner as in Example 1, and was found to be 3.0×10 5 cm -2 Thus, an epitaxial substrate 1c for vertical devices on which a high-quality GaN epitaxial film was grown could be manufactured.

[0100] In addition, when the cross section of the epitaxial substrate 1c for a vertical device was observed with an electron microscope, the growth of the planarization layer 105 (SiO2), the seed crystal layer 107 (SiC), the buffer layer 111, the SiN layer 110, and the HVPE-GaN epitaxial film 401 was confirmed, as shown in FIG. 9.

[0101] Specifically, a layer with a thickness of about 24.7 μm was observed in the SEM image shown in Figure 9(a), which is approximately the same as the total thickness of buffer layer 111 (thickness 0.15 μm), GaN layer 115 (thickness 3.4 μm + 2.1 μm), and HVPE-GaN epitaxial film 401 (thickness 19 μm), and it was found that the total thickness of these layers was as targeted.

[0102] Furthermore, as shown in Figures 9(b) and (c), when the layer with a thickness of approximately 24.7 µm was enlarged, a layer with a thickness of 3.4 µm was observed. This is the same as the thickness of the first layer of GaN layer 115, so it was found that GaN layer 115 had also reached the desired thickness.

[0103] In the TEM images shown in FIG. 9(d)(e), the planarization layer 105 (SiO2), the seed crystal layer 107 (SiC), and the buffer layer 111 (Al 0.2 Ga 0.8 N), and the SiN layer 110 were laminated in order.

[0104] Next, this epitaxial substrate 1c for a vertical device was processed by the following device process to fabricate a vertical power device (SBD). First, as shown in FIG. 8(b), a mask 501 for a Schottky electrode was prepared by photolithography, and a Schottky electrode 503 was formed by sputtering.

[0105] Thereafter, as shown in Fig. 8(c), a mask 501 was formed by photolithography, and then dry etching was performed down to the SiO2 planarization layer 105. Next, as shown in Fig. 8(d), a temporary support substrate 504 was bonded to the Schottky electrode 503 side, and immersed in an HF solution 319 to dissolve the SiO2 planarization layer 105, separating the upper part (device layer portion) and the lower part from the planarization layer 105, and exposing the SiC seed crystal layer 107 on the device layer portion side.

[0106] Furthermore, a drain electrode 505 was formed on the surface of the seed crystal layer 107 as shown in Fig. 8(e), and Au507 was further formed as shown in Fig. 8(f). Furthermore, a metal bond was performed with a conductive substrate 321 prepared in advance with Au507 attached. Furthermore, as shown in Fig. 8(g), each separated chip was picked up and soldered onto a substrate 322 on which an electronic circuit was formed. This allowed the formation of a vertical power device (SBD) as a semiconductor device.

[0107] Example 4: Vertical Light Emitting Device First, a GaN epitaxial film 112 was grown in the following manner to produce an epitaxial substrate 1d shown in FIG. 10(a).

[0108] First, similarly to Example 1, a nitride ceramic substrate (AlN) as a core 101 was wrapped with a sealing layer 103, and a silicon oxide layer 105 having a thickness of 0.05 μm to 3.0 μm was provided on at least the side where the seed crystal layer 107 was to be bonded.

[0109] Next, 6H—SiC (resistivity 20 Ωcm, thickness 0.04 μm to 1.0 μm, epitaxial growth surface is a Si surface with an off angle of 0°) is transferred onto the flattening layer 105 as the seed crystal layer 107, and Al is grown on the seed crystal layer 107 as the buffer layer 111 in the same manner as in Example 1. 0.2 Ga 0.8 The N layer was formed to a thickness of 0.15 μm. 0.2 Ga 0.8 The N layer is doped with 1.0×10 19 atoms / cm 3 Doped it.

[0110] Next, as in Example 1, a SiN layer 110 was grown in an island shape with a thickness of 1 nm on the buffer layer 111, and then a GaN layer 115 was epitaxially grown to a thickness of 3.0 μm. A SiN layer 110 was grown in an island shape with a thickness of 1 nm on top of that, and further a GaN epitaxial film 112 was epitaxially grown to a thickness of 4.0 μm.

[0111] In addition, they grew six pairs of MQW (multiple quantum wells) (InGaN: 2.3 nm / GaN: 11 nm) which serve as the active layer of the light-emitting diode. A 200 nm Mg-doped GaN layer was grown on top of it. Through the above steps, an epitaxial substrate 1d for a vertical light emitting device was manufactured.

[0112] The dislocation density near the surface of the epitaxial substrate 1d was measured in the same manner as in Example 1, and was found to be 9.0×10 5 cm -2 Thus, an epitaxial substrate 1d for a vertical device on which a high-quality GaN epitaxial film 112 was grown could be manufactured.

[0113] Next, this epitaxial substrate 1d for a vertical device was processed by the following device process to fabricate a vertical light emitting device. First, as shown in Fig. 10(b), a mask 601 was formed by photolithography on the outermost surface of an epitaxial substrate 1c for a vertical device, and then a p-electrode 603 was formed by sputtering. Then, as shown in Fig. 10(c), a mask 601 was formed by photolithography to protect the p-electrode 603 and also to separate elements.

[0114] Next, as shown in Fig. 10(d), dry etching was performed down to the SiO2 planarization layer 105. Furthermore, as shown in Fig. 10(e), a temporary support substrate 605 was attached to the p-electrode 603 side and immersed in an HF solution 319 to dissolve the planarization layer 105, and the device layer portion was separated from the part below the planarization layer 105.

[0115] Next, as shown in Fig. 10(f), an n-electrode 607 was formed by sputtering on the seed crystal layer 107 exposed on the separated device layer side. Furthermore, as shown in Fig. 10(g), Au was sputtered on the surface, and metal bonding was performed with a conductive substrate 321 prepared in advance on which Au had been formed, followed by sintering. Furthermore, as shown in Fig. 10(f), each chip was picked up and soldered onto a substrate 322 on which an electronic circuit had been formed. This resulted in the formation of a vertical light-emitting element as a semiconductor device.

[0116] Example 5: Lateral power device First, a GaN epitaxial film 112 was grown in the following manner to produce an epitaxial substrate 1e for a lateral power device as shown in FIG. 11(a).

[0117] First, similarly to Example 1, a nitride ceramic substrate (AlN) as a core 101 was wrapped with a sealing layer 103, and a silicon oxide layer 105 having a thickness of 0.05 μm to 3.0 μm was provided on at least the side where the seed crystal layer 107 was to be bonded.

[0118] Next, 4H-SiC (resistivity 1.0×10) was grown on the planarizing layer 105 as a seed crystal layer 107. 6 A silicon surface having a thickness of 0.04 μm to 1.0 μm and an epitaxial growth surface with an off-angle of 0° was transferred onto the seed crystal layer 107, and an Al 0.2 Ga 0.8 The N layer was formed to a thickness of 0.15 μm.

[0119] Next, as in Example 1, a SiN layer 110 was grown in an island shape with a thickness of 1 nm on the buffer layer 111, and then a GaN layer 115 was epitaxially grown to a thickness of 3.4 μm. A SiN layer 110 was grown in an island shape with a thickness of 1 nm on top of that, and further a GaN epitaxial film 112 was epitaxially grown to a thickness of 4.0 μm.

[0120] On top of that is a barrier layer of Al 0.25 Ga 0.75An N layer 701 was epitaxially grown to a thickness of 25 nm, and an Mg-doped p-GaN layer 703 was further grown to a thickness of 3 nm. Through the above steps, an epitaxial substrate 1e for a lateral power device was manufactured.

[0121] The dislocation density near the surface of the epitaxial substrate 1e was measured in the same manner as in Example 1, and was found to be 9.0×10 5 cm -2 Thus, an epitaxial substrate 1e for a lateral power device on which a high-quality GaN epitaxial film 112 was grown could be manufactured.

[0122] Next, this epitaxial substrate 1e for a lateral power device was processed by the following device process to fabricate a lateral power device. First, as shown in FIG. 11(b), a mask 705 for forming S (source) and D (drain) electrodes is formed by photolithography, and then an Al 0.25 The GaN layer 701 was etched to a depth of 4 nm.

[0123] Next, an S electrode 707 and a D electrode 709 were formed by sputtering. Furthermore, as shown in Fig. 11(c), a mask 705 for forming a G (gate) electrode was formed by photolithography, and a G electrode 711 was sputtered and sintered.

[0124] Next, a mask 705 for isolating elements was formed by photolithography, and etching was performed by dry etching down to the planarization layer 105 as shown in Fig. 11(d). Furthermore, as shown in Fig. 11(e), a temporary support substrate 713 was bonded, and immersed in an HF solution 319 to dissolve the SiO2 of the planarization layer 105, and the device layer portion was separated from the part below the planarization layer 105.

[0125] Next, as shown in Figure 11 (f), with the device of the device layer portion supported on the temporary support substrate 713, the exposed seed crystal layer 107 was covered with a thin film of Au 715 and metal-bonded to a heat dissipation substrate 717 covered with the thin film of Au 715.

[0126] 11(h), the chips were picked up one by one and mounted at designated positions on the substrate 322 on which the electronic circuit was formed, thereby forming a lateral power device as a semiconductor device.

[0127] Example 6: Lateral Light Emitting Device First, a GaN epitaxial film 112 was grown in the following manner to produce an epitaxial substrate 1f for a lateral light emitting device as shown in FIG. 12(a).

[0128] First, similarly to Example 1, a nitride ceramic substrate (AlN) as a core 101 was wrapped with a sealing layer 103, and a silicon oxide layer 105 having a thickness of 0.05 μm to 3.0 μm was provided on at least the side where the seed crystal layer 107 was to be bonded.

[0129] Next, 6H—SiC (resistivity 20 Ωcm, thickness 0.04 μm to 1.0 μm, epitaxial growth surface is a Si surface with an off angle of 0°) is transferred as a seed crystal layer 107 onto the surface of the flattening layer 105, and Al is grown on the seed crystal layer 107 as a buffer layer 111 in the same manner as in Example 1. 0.2 Ga 0.8 The N layer was formed to a thickness of 0.15 μm. 0.2 Ga 0.8 The N layer is doped with 1.0×10 19 atoms / cm 3 Doped it.

[0130] Next, as in Example 1, a SiN layer 110 was grown in an island shape with a thickness of 1 nm on the buffer layer 111, and then a GaN layer 115 was epitaxially grown with a thickness of 3 μm. A SiN layer 110 was grown in an island shape with a thickness of 1 nm on top of that, and further a GaN epitaxial film 112 was epitaxially grown with a thickness of 4 μm.

[0131] Next, six pairs of MQW (InGaN: 2.3 nm / GaN: 11 nm) were grown as the active layer of the light emitting diode, and a GaN layer 801 doped with Mg was grown to a thickness of 200 nm. Through the above steps, an epitaxial substrate 1f for a lateral light emitting device was manufactured.

[0132] The dislocation density near the surface of the epitaxial substrate 1f was measured in the same manner as in Example 1, and was found to be 9.0×10 5 cm -2 Thus, an epitaxial substrate 1f for a lateral light emitting device on which a high-quality GaN epitaxial film 112 was grown could be manufactured.

[0133] Next, this epitaxial substrate 1f for the lateral light emitting device was processed by the following device process to fabricate a lateral light emitting device. First, as shown in FIG. 12(a), a mask 901 was formed by photolithography, and a p-electrode 903 was formed by sputtering.

[0134] Next, as shown in FIG. 12(b), a mask 901 is formed by photolithography to form the n-electrode, and the n-electrode forming portion and the element isolation portion are simultaneously etched by dry etching. 0.2 Ga 0.8 Dry etching was performed up to the top of the N buffer layer 111.

[0135] Then, as shown in FIG. 12(c), a mask 901 is formed by photolithography to form an n-electrode 904, and sintering is performed to form an ohmic electrode. Then, as shown in FIG. 12(d), a mask 901 is formed by photolithography for element isolation, and a buffer layer 111 (Al 0.2 Ga 0.8 The silicon nitride (N) and the seed crystal layer 107 (SiC) were dry etched to expose the SiO2 planarization layer 105.

[0136] Next, as shown in FIG. 12(e), a temporary support substrate 906 was bonded, and the substrate was immersed in an HF solution 319 to dissolve the SiO2 of the planarization layer 105. The device layer portion was separated from the portion below the planarization layer 105, and a thin film 905 of Au was formed on the seed crystal layer 107 exposed on the device layer portion side (FIG. 12(f)).

[0137] Next, as shown in Fig. 12(g), metal bonding was performed with a heat dissipation substrate 717 covered with a thin film of Au 905. Then, as shown in Fig. 12(h), the chips were picked up one by one and mounted at a designated position on the substrate 322 on which the electronic circuit was formed. In this way, a horizontal light emitting element was formed as a semiconductor device.

[0138] Example 7: Epitaxial Substrate for Vertical Devices An epitaxial substrate was fabricated in the same manner as in Example 1, except that the SiN layer 110 and the GaN layer 115 thereon were not formed. As in Example 1, the dislocation density of the GaN layer 120 was measured and found to be 1×10 6 cm -2 Although the dislocation density is higher than that of Example 1, it is 1×10 6 cm -2 The following high quality epitaxial substrates were obtained:

[0139] Comparative Example 1 GaN epitaxial film 112 was grown in the following procedure to produce epitaxial substrate 2 shown in FIG.

[0140] First, similarly to Example 1, a nitride ceramic substrate (AlN) as a core 101 was wrapped with a sealing layer 103, and a silicon oxide layer 105 having a thickness of 0.05 μm to 3.0 μm was provided on at least the side where the seed crystal layer 107 was to be bonded.

[0141] Next, Si (resistivity 20 Ωcm, thickness 0.04 μm to 1.0 μm, off angle 0°) instead of SiC was transferred onto the flattening layer 105 as the seed crystal layer 107, and Al was deposited on the seed crystal layer 107 as the buffer layer 111 in the same manner as in Example 1. 0.2 Ga 0.8 The N layer was formed to a thickness of 0.15 μm. 0.2 Ga 0.8 The N layer is doped with 1.0×10 19 atoms / cm 3 Thereafter, in the same manner as in Example 1, a GaN layer 907 was epitaxially grown to a thickness of 7 μm.

[0142] The dislocation density near the surface of GaN layer 907 was measured in the same manner as in Example 1, and was found to be 2×10 8 cm -2 This was higher than that of the embodiment. Thereafter, a GaN layer 909 was epitaxially grown to a thickness of 19 μm by HVPE to produce an epitaxial substrate for a vertical device. Furthermore, the dislocation density near the surface of the GaN layer 907 was measured in the same manner as in embodiment 1, and it was found to be 9×10 6 cm -2 , which was higher than that of the embodiment.

[0143] The present specification includes the following aspects. [1]: A method for producing a GaN epitaxial film, comprising the steps of: A preparation step of preparing a support substrate having a diameter of 150 mm or more and a thickness of less than 1 mm, the support substrate having a nitride ceramic core sealed with a sealing layer; a substrate manufacturing process for obtaining an epitaxial growth substrate by sequentially stacking a planarization layer and a seed crystal layer made of a SiC single crystal on the support substrate; an epitaxial step of growing a GaN epitaxial film having a thickness of 7 μm or more on the epitaxial growth substrate; The dislocation density is 1.0×10 6 / cm 2 A method for producing a GaN epitaxial film, comprising the steps of: [2]: In the epitaxial process, A method for producing a GaN epitaxial film according to the above item [1], characterized in that a formation step is performed to form an island-shaped SiN layer, an ELO step is performed to grow a GaN layer using the SiN layer as a mask, and then a growth step is performed to grow a GaN epitaxial film on the topmost SiN layer or the GaN layer. [3]: In the epitaxial process, The method for producing a GaN epitaxial film according to [2] above, characterized in that the formation step and the ELO step are performed alternately. [4]: A method for producing a GaN epitaxial film according to any one of [1] to [3] above, wherein the SiC single crystal has an off-angle of 0° to 4°. [5]: A method for manufacturing a semiconductor device, comprising the steps of: fabricating a device on a GaN epitaxial film manufactured by any one of the methods for manufacturing a GaN epitaxial film according to any one of [1] to [4] above; and then etching the planarization layer to separate the device from the supporting substrate.

[0144] 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]

[0145] 1...epitaxial substrate, 1a...epitaxial substrate, 1b...epitaxial substrate, 1c...epitaxial substrate, 1d...epitaxial substrate, 1e...epitaxial substrate, 1f...epitaxial substrate, 2...epitaxial substrate, 100...support substrate, 101...core, 103...sealing layer, 105...planarization layer, 107...seed crystal layer, 109...substrate for epitaxial growth, 110...SiN layer, 111...buffer layer, 112...GaN epitaxial film, 113...ELO layer, 114...n-GaN layer, 115...GaN layer, 118...n-GaN layer, 119...p-GaN layer, 120...GaN layer, 122...p-GaN layer, 123...GaN layer, 200...device, 201...device, 301...mask, 303...n +layer, 305...SiN film, 307...SiO2 film, 309...gate electrode, 311...SiO2 film, 313...source electrode, 315...device layer, 316...drain electrode, 317...temporary support substrate, 319...HF solution, 320...Au, 321...conductive substrate, 322...substrate, 323...substrate, 401...HVPE-GaN epitaxial film, 501...mask, 503...Schottky electrode, 504...temporary support substrate, 505...drain electrode, 507...Au, 601...mask, 603...p electrode, 605...temporary support substrate, 607...n electrode, 701...Al 0.25 Ga 0.75 N layer, 703...p-GaN layer, 705...mask, 707...S electrode, 709...D electrode, 711...G electrode, 713...temporary support substrate, 715...thin film, 717...heat dissipating substrate, 801...GaN layer, 901...mask, 903...p electrode, 904...n electrode, 905...thin film, 906...temporary support substrate, 907...GaN layer, 909...GaN layer.

Claims

1. A method for manufacturing a GaN epitaxial film, comprising the steps of: a preparation step of preparing a support substrate having a diameter of 150 mm or more and a thickness of less than 1 mm, the support substrate having a core made of nitride ceramic sealed with a sealing layer; a substrate manufacturing step of laminating a planarizing layer and a seed crystal layer made of a SiC single crystal in this order on the support substrate to obtain an epitaxial growth substrate; an epitaxial step of growing a GaN epitaxial film having a thickness of 7 μm to 24.7 μm on the epitaxial growth substrate; By including ６ / cm ２ A method for producing a GaN epitaxial film, characterized by producing the following GaN epitaxial film:

2. In the epitaxial process, 2. The method for producing a GaN epitaxial film according to claim 1, further comprising the steps of: forming an island-shaped SiN layer; growing a GaN layer using the SiN layer as a mask; and then growing a GaN epitaxial film on the SiN layer or the GaN layer at the top surface.

3. In the epitaxial process, 3. The method for producing a GaN epitaxial film according to claim 2, wherein the forming step and the ELO step are performed alternately.

4. 2. The method for producing a GaN epitaxial film according to claim 1, wherein the SiC single crystal has an off-angle of 0° to 4°.

5. A method for manufacturing a semiconductor device, comprising the steps of: fabricating a device on the GaN epitaxial film manufactured by the method for manufacturing a GaN epitaxial film according to any one of claims 1 to 4; and then separating the device from the support substrate by etching the planarization layer.

Images