Composite with gallium nitride and diamond and manufacturing method thereof

Abstract

To provide a manufacturing method of a composite in which GaN and diamond can be bonded even in atmospheric air while suppressing deterioration of crystalline of GaN and diamond.SOLUTION: A manufacturing method of a composite in which GaN and diamond are bonded includes: a first substrate processing step of applying processing of one or more of oxidation processing, nitridation processing and reduction processing onto a surface of a gallium oxide layer of a first substrate comprising a gallium nitride layer and the gallium oxide layer, which is formed on the gallium nitride layer and exposed, thereby making the surface of the gallium nitride layer into a functional group; a second substrate processing step of applying the oxidation processing onto a surface of a diamond layer of a second substrate comprising a diamond layer, of which the surface is the (111) plane, thereby making the surface of the diamond layer into a functional group; and a junction step of joining the first substrate and the second substrate by applying reaction energy to a contact part in a state where the surface of the gallium oxide layer after the first substrate processing step is brought into contact with the surface of the diamond layer after the second substrate processing step.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] This application relates to a composite body in which gallium nitride and diamond are bonded via an intermediate layer containing carbon, gallium, and oxygen, and a method for producing the same. [Background technology]

[0002] Gallium nitride (GaN) has been attracting attention as a substrate material for next-generation power semiconductors. In order to improve the heat dissipation performance of GaN, a semiconductor device in which a GaN-based semiconductor is directly bonded to a diamond substrate is known (Patent Document 1). In Patent Document 1, the surfaces where the GaN and diamond are bonded are irradiated with an argon beam to remove natural oxide films and activate them, and then the surfaces are heated under a pressure of 10 -6 GaN and diamond are directly bonded in a vacuum chamber below Pa.

[0003] In the bonding method of Patent Document 1, the crystallinity of GaN deteriorates due to the irradiation of an argon beam on the GaN surface. When the crystallinity of GaN deteriorates, the characteristics of the GaN-based semiconductor as a device deteriorate. In addition, the crystallinity of diamond deteriorates due to the irradiation of an argon beam on the diamond surface. Diamond has a high electric breakdown field and is suitable for ensuring the insulation of GaN-based semiconductors. However, diamond with deteriorated crystallinity has low electric insulation. Therefore, when diamond with deteriorated crystallinity is bonded to a GaN-based semiconductor, it adversely affects the operation of the GaN-based semiconductor. In addition, the bonding method of Patent Document 1 is performed in a high vacuum, so a vacuum bonding device is required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-13007 Summary of the Invention [Problem to be solved by the invention]

[0005] The present application has been made in consideration of these circumstances, and has as its objective to provide a method for manufacturing a composite capable of bonding GaN and diamond even in air while suppressing deterioration of the crystallinity of the two, and a composite in which diamond with suppressed deterioration of crystallinity is bonded, via an intermediate layer, to GaN with suppressed deterioration of crystallinity. [Means for solving the problem]

[0006] The composite of the present application has a gallium nitride layer, an intermediate layer formed on the surface of the gallium nitride layer and containing carbon, gallium, and oxygen, and a diamond layer bonded to the surface of the gallium nitride layer via the intermediate layer.

[0007] A manufacturing method for a composite according to one embodiment of the present application includes a first substrate treatment step of subjecting a surface of the gallium oxide layer of a first substrate having a gallium nitride layer and an exposed gallium oxide layer formed on the gallium nitride layer to one or more of oxidation, nitridation and reduction treatments to functionalize the surface of the gallium oxide layer; a second substrate treatment step of subjecting a surface of a diamond layer of a second substrate having a diamond layer whose surface is a (111) plane to an oxidation treatment to functionalize the surface of the diamond layer; and a bonding step of bringing the surface of the gallium oxide layer that has undergone the first substrate treatment step into contact with the surface of the diamond layer that has undergone the second substrate treatment step into contact with this contact portion and applying reaction energy to the contact portion to bond the first substrate and the second substrate.

[0008] A manufacturing method for a composite according to another embodiment of the present application includes a first substrate treatment step of subjecting a surface of the gallium oxide layer of a first substrate having a gallium nitride layer and an exposed gallium oxide layer formed on the gallium nitride layer to a nitriding treatment to functionalize the surface of the gallium oxide layer, a second substrate treatment step of subjecting a surface of the diamond layer of a second substrate having a diamond layer whose surface is a (100) plane to an oxidation treatment to functionalize the surface of the diamond layer, and a bonding step of bringing the surface of the gallium oxide layer that has undergone the first substrate treatment step into contact with the surface of the diamond layer that has undergone the second substrate treatment step into contact with this contact portion and applying reaction energy to the contact portion to bond the first substrate and the second substrate. Effect of the Invention

[0009] In the manufacturing method of the composite of the present application, the gallium oxide layer on the gallium nitride layer and the diamond layer are each subjected to a predetermined treatment that suppresses deterioration of crystallinity, functionalized, and bonded.Therefore, according to the manufacturing method of the composite of the present application, a composite is obtained in which the gallium nitride layer and the diamond layer are bonded with each other and the deterioration of crystallinity is suppressed.In addition, in the composite of the present application, the gallium nitride layer and the diamond layer are bonded via a predetermined intermediate layer.Therefore, according to the composite of the present application, a composite is obtained in which the gallium nitride layer and the diamond layer are bonded with each other and the deterioration of crystallinity is suppressed. [Brief description of the drawings]

[0010] [Figure 1] 1 is a planar image of Composite 1 of Example 1 observed from the diamond substrate side. [Diagram 2] 1 is a planar image of composite 2 in Example 1 observed from the GaN layer side. [Diagram 3] 1 is a planar image of the composite of Example 2 observed from the diamond substrate side. [Figure 4] 1 is a cross-sectional microscope image of the composite of Example 2. [Diagram 5] 1 is a transmission electron microscope image of the bonding interface of the composite of Example 2. [Figure 6] 13 is an energy dispersive X-ray spectroscopy spectrum of the intermediate layer of the composite of Example 2. [Figure 7] 1 is a transmission electron microscope image and element map of the vicinity of the bonded interface of the composite of Example 2. [Figure 8] Electron energy loss spectroscopy spectra of the intermediate layer of the composite of Example 2 and the diamond substrate. [Figure 9] 1 is a planar image of the adhesion body of Comparative Example 2 observed from the diamond substrate side. [Figure 10] 1 is a planar image of the adhesion body of Comparative Example 3 observed from the diamond substrate side. [Figure 11] 1 is a planar image of the composite of Example 3 observed from the diamond substrate side. [Figure 12] 1 is a planar image of the composite of Example 4 observed from the diamond wafer side. [Figure 13] Rocking curve of the reference GaN substrate. [Figure 14] 4 shows X-ray photoelectron spectroscopy spectra of the surface of the GaN layer before and after the reduction treatment in Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The composite of the embodiment of the present application includes a gallium nitride layer, an intermediate layer, and a diamond layer. The intermediate layer is formed on the surface of the gallium nitride layer. The diamond layer is bonded to the surface of the gallium nitride layer through the intermediate layer. More specifically, the second substrate containing the diamond layer is bonded to the first substrate containing the gallium nitride layer through the intermediate layer. The intermediate layer contains carbon, gallium, and oxygen. The intermediate layer may contain nitrogen. The first substrate may include various substrates such as a single crystal GaN substrate, a GaN / sapphire substrate having a GaN layer on a sapphire substrate surface, a GaN / Si substrate having a GaN layer on a Si substrate surface, and a GaN / SiC substrate having a GaN layer on a SiC substrate surface.

[0012] A natural oxide film, which is a gallium oxide film, is formed on the surface of these GaN layers, and in this embodiment, the intermediate layer originates from this gallium oxide film. The intermediate layer may originate from a gallium oxide film other than the natural oxide film on the GaN layer. The fact that the intermediate layer contains gallium oxide can be determined by energy dispersive X-ray analysis. In order to suppress the decrease in thermal conductivity between the gallium nitride layer and the diamond layer, the thickness of the intermediate layer is preferably 4 nm or less. Since the thickness of the natural oxide film formed on the surface of the GaN layer is about 2 nm, the thickness of the intermediate layer is often 2 nm or more.

[0013] In the semiconductor device of Patent Document 1, in which the natural oxide film is removed by sputtering in ultra-high vacuum and the bonded interface between the GaN-based semiconductor and the diamond substrate has a higher nitrogen content than the oxygen content. However, sputtering the natural oxide film deteriorates the crystallinity of GaN. In this embodiment, the intermediate layer is derived from the gallium oxide film on the surface of the GaN layer. Therefore, the oxygen content of the intermediate layer is higher than the nitrogen content. In this way, the first substrate and the second substrate are bonded through the intermediate layer that contains carbon, gallium, and oxygen and has a smaller nitrogen content than the oxygen content, so that the shear strength between the first substrate and the second substrate is 0.1 MPa or more.

[0014] The second substrate may be a single crystal diamond substrate, a diamond / Si substrate having a diamond layer on a Si substrate surface, or a diamond / sapphire substrate having a diamond layer on a sapphire substrate surface. The diamond layer preferably has a (100) or (111) surface. The diamond layer may also be a mosaic crystal having a (100) or (111) surface.

[0015] The manufacturing method of the composite according to the first embodiment of the present application includes a first substrate treatment step, a second substrate treatment step, and a bonding step. The first substrate includes a gallium nitride layer and an exposed gallium oxide layer formed on the gallium nitride layer. In the first substrate treatment step, a predetermined treatment is performed on the surface of the gallium oxide layer of the first substrate to functionalize the surface of the gallium oxide layer. The predetermined treatment is one or more of an oxidation treatment, a nitridation treatment, and a reduction treatment.

[0016] The oxidation treatment is a treatment in which oxygen atoms are introduced to the surface of the gallium oxide layer to grow the gallium oxide layer. The nitridation treatment is a treatment in which nitrogen atoms are introduced to the surface of the gallium oxide layer. The reduction treatment is a treatment in which reactive functional groups are introduced to the surface while thinning the gallium oxide layer. Examples of the oxidation treatment include treatment with a liquid containing ammonia and hydrogen peroxide, and treatment with reactive oxygen plasma. Examples of the nitridation treatment include treatment with reactive nitrogen plasma. Examples of the reduction treatment include treatment with hydrochloric acid. The treatment with hydrochloric acid functionalizes the surface of the gallium oxide layer with one or more of -OH groups, -NH2 groups, and -Cl groups.

[0017] The examples of these various treatments are the same for the second substrate treatment step in the manufacturing method of the composite of the first embodiment, and the first substrate treatment step and the second substrate treatment step in the manufacturing method of the composite of the second embodiment. It is not necessarily clear what kind of chemical structure the surface of the gallium oxide layer functionalized by oxidation or nitridation in the first substrate treatment step has. However, the surface of the functionalized gallium oxide layer has a property that makes it easy to bond with the surface of the diamond layer functionalized in the second substrate treatment step. Moreover, these predetermined treatments that do not involve the total removal of the gallium oxide layer suppress the deterioration of the crystallinity of the GaN layer.

[0018] The second substrate has a diamond layer whose surface is a (111) plane. In the second substrate treatment step, the surface of the diamond layer of the second substrate is subjected to an oxidation treatment to introduce oxygen atoms into the surface of the diamond layer and functionalize the surface of the diamond layer. The oxidation treatment forms COC groups or -OH groups on the surface of the diamond layer. The functionalized surface of the diamond layer has properties that make it easy to bond with the surface of the gallium oxide layer functionalized in the first substrate treatment step.

[0019] In the bonding step, the surface of the gallium oxide layer that has been subjected to the first substrate treatment step is brought into contact with the surface of the diamond layer that has been subjected to the second substrate treatment step, and reaction energy is applied to the contact portion to bond the first substrate and the second substrate. Examples of reaction energy include thermal energy, light energy, electrical energy, and chemical energy. In this embodiment, the contact portion between the first substrate and the second substrate is heated to a temperature of about 200°C.

[0020] The bonding process bonds the surfaces of the gallium oxide layer and the diamond layer together. According to the electron energy loss spectroscopy of the gallium oxide layer and the diamond layer after bonding, it is considered that the gallium oxide layer and the diamond layer are not bonded by forming Ga-O-C bonds, but are bonded by the diffusion of C atoms on the surface of the diamond layer into the gallium oxide layer. The bonding process can be carried out in a vacuum container, but can also be carried out in the atmosphere. Therefore, the bonding process in the manufacturing method of the composite of this embodiment does not require a vacuum bonding device.

[0021] A method for manufacturing a composite according to a second embodiment of the present application will be described. In the description of the method for manufacturing a composite according to this embodiment, overlapping with the method for manufacturing a composite according to the first embodiment will be omitted as appropriate. The method for manufacturing a composite according to this embodiment also includes a first substrate treatment step, a second substrate treatment step, and a bonding step. In the first substrate treatment step, a nitriding treatment is performed on the surface of the gallium oxide layer of the first substrate, which includes a gallium nitride layer and an exposed gallium oxide layer formed on the gallium nitride layer, to functionalize the surface of the gallium oxide layer. In the second substrate treatment step, an oxidation treatment is performed on the surface of the diamond layer of the second substrate, which includes a diamond layer whose surface is a (100) plane, to functionalize the surface of the diamond layer.

[0022] Diamonds with a (100) surface (hereinafter sometimes simply referred to as "(100) diamond") are commonly used in the industry. However, it has been difficult to bond (100) diamond to GaN. The inventors of the present application have found that by subjecting the gallium oxide layer on the gallium nitride layer to a nitriding treatment, rather than an oxidation and reduction treatment, it becomes easier to bond the oxidized (100) diamond surface. In the bonding step, similar to the bonding step in the manufacturing method of the composite of the first embodiment, the surface of the gallium oxide layer that has been subjected to the first substrate treatment step and the surface of the diamond layer that has been subjected to the second substrate treatment step are brought into contact with each other, and reaction energy is applied to this contact portion to bond the first substrate and the second substrate. EXAMPLES

[0023] Example 1 A GaN / sapphire substrate (POWDEC, thickness 0.635 mm) having a 2 μm thick GaN layer on the sapphire substrate surface, the (0001) surface of which was polished, was cut into a parallelogram shape with one side of approximately 8 mm and the adjacent side of approximately 7 mm. The surface of the GaN layer of this GaN / sapphire substrate was treated as follows. The surface of this GaN layer, i.e., the native oxide layer of GaN, was immersed for 10 minutes in a treatment solution at 75°C consisting of 10 mL of 28% ammonia water, 10 mL of 35% hydrogen peroxide water, and 50 mL of pure water. The surface of this GaN layer was then washed with pure water for 5 minutes (oxidation treatment).

[0024] On the other hand, the surface of the diamond layer of a single crystal diamond substrate (EDP Corporation) with a thickness of 0.3 mm and a size of 3 mm square, with a (111) surface, was treated (oxidation treatment) under the same conditions as the surface treatment of the GaN layer. These oxidation treatments functionalized the surfaces of the GaN layer and the diamond layer, making them more likely to be bonded together. After leaving the surfaces of the GaN layer and the diamond layer in contact in the air for one day, they were heated at a temperature of 200°C for two hours to obtain a composite 1 in which the GaN / sapphire substrate and the diamond substrate were bonded, i.e., the GaN layer and the diamond layer were bonded.

[0025] Figure 1 is a planar image of composite 1 observed from the diamond substrate side. As shown in Figure 1, no bright areas indicating depletion between the substrates were observed. In other words, most of the surface of the GaN layer of the GaN / sapphire substrate and the surface of the diamond layer of the diamond substrate were bonded. From the sapphire substrate side of composite 1, a laser beam with a wavelength of 248 nm and an energy density of 1000 mJ / cm was applied. 2 The GaN / sapphire substrate was irradiated with a 0.3 mm x 0.15 mm lattice pattern, and the GaN layer was peeled off from the GaN / sapphire substrate and transferred to the surface of the diamond layer of the diamond substrate, obtaining composite 2 in which the diamond layer was bonded to the GaN layer. Figure 2 shows a planar image of composite 2 observed from the GaN layer side. As shown in Figure 2, multiple rectangular GaN layers measuring 0.3 mm x 0.15 mm were formed on the right side of the surface of the 3 mm square diamond substrate. The thickness of this GaN layer was 2 μm.

[0026] Example 2 A GaN / Si substrate (CoorsTek, thickness 0.635 mm) having a 2 μm thick GaN layer on the surface of a Si substrate, the (0001) surface of which was polished, was cut into a 15 mm × 16 mm rectangle. The surface of the GaN layer of this GaN / Si substrate was treated as follows. The surface of this GaN layer, i.e., the native oxide layer of GaN, was immersed for 10 minutes in a treatment solution at 70°C consisting of 10 mL of 35% hydrochloric acid and 60 mL of pure water. The surface of this GaN layer was then washed with pure water for 5 minutes (reduction treatment).

[0027] Figure 14 shows the X-ray photoelectron spectroscopy spectra of the surface of the GaN layer after this reduction treatment ("HCl treated" in the figure) and the surface of the GaN layer before this reduction treatment ("untreated" in the figure). As shown in Figure 14, by treating the surface of the GaN layer with hydrochloric acid, the peak derived from the O1s orbital becomes smaller and the position of this peak shifts to the higher energy side. It can be seen that the reduction treatment of the surface of the GaN layer makes the native oxide layer on the surface of the GaN layer thinner, and Ga-OH, which has a higher bond energy than Ga2O3, is formed. Furthermore, the peak derived from the -NH2 group near 397.7 eV and the peak derived from the -Cl group near 200 eV become larger. It can be seen that Ga-NH2 and Ga-Cl are formed.

[0028] On the other hand, a surface-treated diamond substrate was obtained under the same conditions as in Example 1, except that the temperature of the treatment solution during immersion was changed to 70°C (oxidation treatment). It is known that COC or C-OH is formed on the surface of a diamond layer that has been subjected to oxidation treatment. Thereafter, a composite was obtained in which the GaN layer of the GaN / Si substrate and the diamond layer of the diamond substrate were bonded together, using the same method as in Example 1. This composite was obtained by reacting at the interface between the -OH group, -NH2 group, or -Cl group formed on the surface of the GaN layer and the COC group or -OH group formed on the surface of the diamond layer.

[0029] Figure 3 is a planar image of this composite observed from the diamond substrate side. As shown in Figure 3, this composite has the surfaces of the diamond layers of two small diamond substrates bonded to the surface of the GaN layer of a large GaN / Si substrate. Even though the GaN layer and diamond layer overlap, Newton rings are observed in the areas where the surfaces of the GaN layer and diamond layer are not bonded. As shown in Figure 3, the surface of the diamond layer of the diamond substrate in the upper right is bonded entirely to the surface of the GaN layer, and the surface of the diamond layer of the diamond substrate in the lower center is bonded to approximately 70% of the surface area of ​​the GaN layer.

[0030] This composite was cut by irradiating it with laser light so as to pass through the diamond substrate, the GaN layer, and the Si substrate. Figure 4 is a microscope image of this cross section. As shown in Figure 4, no non-bonded areas were observed at the bonding interface between the diamond layer of the diamond substrate and the GaN layer. In addition, this composite was cut by irradiating it with laser light, and an extremely thin specimen was produced by irradiating the cross section with a focused ion beam. The bonding interface between the diamond layer and the GaN layer of this specimen was observed using a transmission electron microscope. Figure 5 is a transmission electron microscope image of this bonding interface. As shown in Figure 5, an intermediate layer with a thickness of approximately 3 nm was observed at the bonding interface.

[0031] The composition of this intermediate layer was analyzed by energy dispersive X-ray spectroscopy. Figure 6 shows the energy dispersive X-ray spectrum of this intermediate layer. The element ratio of this intermediate layer was C: 59.8%, Ga: 28.0%, O: 9.4%, N: 2.8%, and Cl: 0.1%, with the O content being greater than the N content. Furthermore, element mapping was performed near the bonding interface of this sample by energy dispersive X-ray spectroscopy. Figure 7 shows a transmission electron microscope image of the bonding interface of this sample and element maps of C, Ga, O, N, and Cl. The GaN layer portion was composed of Ga and N, the diamond layer portion was composed of C, and small amounts of O and Cl were observed at the bonding interface.

[0032] In addition, the structure of the intermediate layer and the diamond layer of this sample was evaluated by electron energy loss spectroscopy (EELS). Figure 8 shows the electron energy loss spectroscopy spectra of the intermediate layer and the diamond layer of this sample for C, Ga, O, and N. In the region of high crystallinity of diamond, the σ bond of carbon (sp 3 ) is observed. A σ bond peak was observed inside the diamond layer of this sample (inside diamond in the figure), but a π bond (sp 2) were observed. In addition, Ga and O peaks were detected inside the diamond layer and the intermediate layer (in the figure, "Interface intermediate layer interior"), but no significant peak was detected for N. From these results, it is concluded that the intermediate layer is 2 It is thought to be composed of bonded carbon, gallium, and oxygen.

[0033] Comparative Example 1 The surface of the GaN layer of the same GaN / sapphire substrate as in Example 1 and the surface of the diamond layer of the same single crystal diamond substrate as in Example 1 were washed with acetone, ethanol, and pure water, in that order, for 5 minutes each. The washed surfaces of the GaN / sapphire substrate and the diamond substrate were left in contact with each other in the air for 1 day, and then heated at a temperature of 200°C for 2 hours. However, the GaN layer of the GaN / sapphire substrate and the diamond layer of the single crystal diamond substrate were not bonded. Unlike Example 1, the surface treatment with acetone, ethanol, and pure water, which does not correspond to the oxidation treatment, nitridation treatment, and reduction treatment, did not change the properties of the GaN layer and the diamond substrate to be easily bonded to each other.

[0034] Comparative Example 2 The same GaN / sapphire substrate as in Example 1 was cut into a parallelogram shape with one side of about 8 mm and the adjacent side of about 7 mm. The surface of the GaN layer of this GaN / sapphire substrate was treated (reduction treatment) under the same conditions as the surface treatment of the GaN layer of the GaN / sapphire substrate in Example 2. Meanwhile, the surface of the diamond layer of a single crystal diamond substrate (EDP Corporation) with a (100) surface, a thickness of 0.3 mm, and a size of 5 mm square was treated (oxidation treatment) under the same conditions as the surface treatment of the diamond layer of the diamond substrate in Example 1.

[0035] Thereafter, a bonded body was obtained in which the GaN layer of the GaN / sapphire substrate and the diamond layer of the diamond substrate were bonded by the same method as in Example 1. Figure 9 is a planar image of this bonded body observed from the diamond substrate side. As shown in Figure 9, the depletion between the GaN / sapphire substrate and the diamond substrate was bright, and Newton's rings were observed, indicating that the GaN layer and the diamond layer were not bonded entirely.

[0036] Comparative Example 3 The same GaN / sapphire substrate as in Example 1 was cut into a parallelogram shape with one side of about 8 mm and the adjacent side of about 7 mm. The surface of the GaN layer of this GaN / sapphire substrate was treated (oxidation treatment) under the same conditions as the surface treatment of the GaN layer of the GaN / sapphire substrate in Example 1. Meanwhile, the surface of the diamond layer of the same diamond substrate as in Comparative Example 2 was subjected to reactive ion etching treatment (oxidation treatment) using oxygen gas at a pressure of 40 Pa at a power of 200 W for 30 seconds.

[0037] Thereafter, the same method as in Example 1 was used to obtain an attachment in which the GaN layer of the GaN / sapphire substrate and the diamond layer of the diamond substrate were attached. Figure 10 is a planar image of this attachment observed from the diamond substrate side. As shown in Figure 10, the depletion between the GaN / sapphire substrate and the diamond substrate was bright, and Newton's rings were observed, indicating that the GaN layer and the diamond layer were not bonded entirely. In addition, this attachment broke when a shear strength of 48 kPa was applied.

[0038] Example 3 The same GaN / sapphire substrate as in Example 1 was cut into a parallelogram shape with one side of about 8 mm and the adjacent side of about 7 mm. The surface of the GaN layer of this GaN / sapphire substrate was treated under the same conditions as the surface treatment of the GaN layer of the GaN / sapphire substrate in Example 1. Furthermore, the surface of this GaN layer was treated by reactive ion etching using nitrogen gas at a pressure of 40 Pa at an output of 200 W for 30 seconds (nitridation treatment). Meanwhile, the surface of the diamond layer of the same diamond substrate as in Comparative Example 2 was treated under the same conditions as the surface treatment of the diamond layer of the diamond substrate in Example 1 (oxidation treatment).

[0039] Thereafter, a composite was obtained in which the GaN layer of the GaN / sapphire substrate and the diamond layer of the diamond substrate were bonded together by the same method as in Example 1. Figure 11 is a planar image of this composite observed from the diamond substrate side. Darkness due to depletion between the substrates was only observed in a part of the right side of the diamond substrate. In other words, in this composite, the substrates were bonded together, i.e., the GaN layer and the diamond layer were mostly bonded together. This composite broke when a shear strength of 2.8 MPa was applied.

[0040] Example 4 The same GaN / sapphire substrate as in Example 1 was cut into a rectangular shape of 15 mm x 16 mm. Thereafter, a GaN / sapphire substrate was obtained in which the surface of the GaN layer was nitrided in the same manner as in Example 3. Meanwhile, the surface of the diamond layer of a circular mosaic single crystal diamond minimal wafer (EDP Co., Ltd.) with a (100) surface, a thickness of 0.3 mm and a diameter of 12.5 mm was treated (oxidation treatment) under the same conditions as the surface treatment of the diamond layer of the diamond substrate in Example 1.

[0041] Thereafter, a composite was obtained in which the GaN layer of the GaN / sapphire substrate and the diamond layer of the diamond wafer were bonded together by the same method as in Example 1. Figure 12 is a planar image of this composite observed from the diamond wafer side. Darkness due to depletion between the substrate and the wafer was only observed in a part of the upper left corner of the center of the diamond wafer. In other words, most of the GaN layer and the diamond layer were bonded together in this composite.

[0042] Reference example The surface of the GaN layer of the same GaN / sapphire substrate as in Example 1 was irradiated with an Ar atomic beam accelerated at a voltage of 1.5 kV and a current of 100 mA for 120 seconds to obtain a GaN substrate 1 in which the surface oxide film of the GaN layer was sputtered off. In addition, a GaN substrate 2 was obtained by subjecting the surface of the GaN layer to a reduction treatment in the same manner as in Example 2. Furthermore, a GaN substrate 3 was obtained by subjecting the surface of the GaN layer to a nitriding treatment in the same manner as in Example 3. The crystallinity of these GaN substrates was evaluated using XRD. That is, X-rays were incident on the surface of each GaN substrate at an incident angle of 0.3°, and a peak originating from the GaN (110) plane near 2Θ=57.775 in a region about 8 nm away from the surface was evaluated.

[0043] FIG. 13 shows the results of rocking curve measurement of each GaN substrate by XRD. The larger the half width, the more deteriorated the crystallinity of GaN. For GaN substrate 1, the half width of the in-plain XRD was 0.333°, and the half width of the rocking curve measurement was 0.418°. For GaN substrate 2, the half width of the in-plain XRD was 0.331°, and the half width of the rocking curve measurement was 0.395°. For GaN substrate 3, the half width of the in-plain XRD was 0.330°, and the half width of the rocking curve measurement was 0.387°.

[0044] That is, when the surface oxide film of the GaN layer was removed, as in GaN substrate 1, the crystallinity of the surface of the GaN layer was significantly deteriorated. In contrast, when the surface oxide film of the GaN layer was not completely removed but the surface was functionalized, as in GaN substrate 2 and GaN substrate 3, the deterioration of the crystallinity of the surface of the GaN layer could be suppressed. Therefore, it was found that by subjecting the surface oxide film of the GaN layer to the oxidation treatment, nitridation treatment, and reduction treatment of the present application, the deterioration of the crystallinity of the surface of the GaN layer can be suppressed while changing the properties of the surface of the GaN layer to one that is easily bonded to the surface of the diamond layer.

Claims

1. a gallium nitride layer; an intermediate layer formed on the surface of the gallium nitride layer and containing carbon, gallium, and oxygen; a diamond layer bonded to the surface of the gallium nitride layer via the intermediate layer; A complex having

2. In claim 1, A composite in which the diamond layer has a surface of a (100) plane or a (111) plane, or is a mosaic crystal having a surface of a (100) plane or a (111) plane.

3. In claim 2, The composite, wherein the thickness of the intermediate layer is 4 nm or less.

4. In claim 3, The composite wherein the nitrogen content of the intermediate layer is less than the oxygen content.

5. In any one of claims 1 to 4, a second substrate containing the diamond layer is bonded to a first substrate containing the gallium nitride layer; A composite having a shear strength between the first substrate and the second substrate of 0.1 MPa or more.

6. a first substrate treatment step of subjecting a surface of the gallium oxide layer of a first substrate, the first substrate comprising a gallium nitride layer and an exposed gallium oxide layer formed on the gallium nitride layer, to a nitriding treatment to functionalize the surface of the gallium oxide layer; a second substrate treatment step of subjecting a surface of a diamond layer of a second substrate, the surface of which is a (111) plane, to an oxidation treatment to functionalize the surface of the diamond layer; a bonding step of bonding the first substrate and the second substrate by bringing the surface of the gallium oxide layer that has been subjected to the first substrate treatment step into contact with the surface of the diamond layer that has been subjected to the second substrate treatment step and applying reaction energy to this contact portion; A method for producing a composite having the formula:

7. a first substrate treatment step of subjecting a surface of the gallium oxide layer of a first substrate including a gallium nitride layer and an exposed gallium oxide layer formed on the gallium nitride layer to a reduction treatment to functionalize the surface of the gallium oxide layer; a second substrate treatment step of subjecting a surface of a diamond layer of a second substrate, the surface of which is a (111) plane, to an oxidation treatment to functionalize the surface of the diamond layer; a bonding step of bonding the first substrate and the second substrate by bringing the surface of the gallium oxide layer that has been subjected to the first substrate treatment step into contact with the surface of the diamond layer that has been subjected to the second substrate treatment step and applying reaction energy to this contact portion; A method for producing a composite having the formula:

8. a first substrate treatment step of subjecting a surface of the gallium oxide layer of a first substrate, the first substrate comprising a gallium nitride layer and an exposed gallium oxide layer formed on the gallium nitride layer, to a nitriding treatment to functionalize the surface of the gallium oxide layer; a second substrate treatment step of subjecting a surface of a diamond layer of a second substrate, the surface of which is a (100) plane, to an oxidation treatment to functionalize the surface of the diamond layer; a bonding step of bonding the first substrate and the second substrate by bringing the surface of the gallium oxide layer that has been subjected to the first substrate treatment step into contact with the surface of the diamond layer that has been subjected to the second substrate treatment step and applying reaction energy to this contact portion; A method for producing a composite having the formula:

9. A first substrate treatment step of subjecting a surface of the gallium oxide layer of a first substrate having a gallium nitride layer and an exposed gallium oxide layer formed on the gallium nitride layer to an oxidation treatment to functionalize the surface of the gallium oxide layer; a second substrate treatment step of subjecting a surface of a diamond layer of a second substrate, the surface of which is a (111) plane, to an oxidation treatment to functionalize the surface of the diamond layer; a bonding step of bonding the first substrate and the second substrate by bringing the surface of the gallium oxide layer that has been subjected to the first substrate treatment step into contact with the surface of the diamond layer that has been subjected to the second substrate treatment step and applying reaction energy to this contact portion; and A method for producing a composite, wherein the oxidation treatment in the first substrate treatment step is treatment with a liquid containing ammonia and hydrogen peroxide.

10. In claim 6, A method for manufacturing a composite, wherein the nitriding treatment in the first substrate treatment step is a treatment with reactive nitrogen plasma.

11. In claim 7, A method for producing a composite, wherein the reduction treatment in the first substrate treatment step is treatment with hydrochloric acid.

12. In claim 11, In the first substrate treatment step, the surface of the gallium oxide layer is treated with —OH groups, —NH ２ A method for preparing a composite functionalized with one or more of the -Cl group and the -Cl group.

13. In claim 8, The method for manufacturing a composite, wherein the nitriding treatment is a treatment with reactive nitrogen plasma.

14. In any one of claims 6 to 13, A method for producing a composite, wherein the joining step is carried out in the atmosphere.

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