Attached substrate, semiconductor element, and method for manufacturing attached substrate

Abstract

The present application provides a bonded substrate with excellent bonding strength. A bonded substrate having a Group III element nitride layer and a support substrate including a support layer, wherein the carbon concentration of the Group III element nitride layer is 5 x 10 17 atoms / cm 3 or less and the carbon concentration of the support layer is 2 x 10 19 atoms / cm 3 or less.

Description

Technical Field

[0001] This invention relates to a bonding substrate, a semiconductor device, and a method for manufacturing a bonding substrate. Background Technology

[0002] Regarding group III nitrides, they are being actively developed as semiconductor materials, for example. As a substrate for semiconductor devices employing group III nitrides, for example as described in Patent Document 1, a bonding substrate has been proposed to be obtained by bonding a group III nitride layer with a substrate whose coefficient of thermal expansion is close to that of the group III nitride layer.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 4458116 Summary of the Invention

[0006] However, the bonding strength of the aforementioned bonding substrates is sometimes insufficient. For example, during the process of obtaining a semiconductor device, when the device layer is formed on the aforementioned bonding substrate, peeling of the group III nitride layer and the substrate sometimes occurs.

[0007] In view of the above, the main objective of the present invention is to provide a bonding substrate with excellent bonding strength.

[0008] 1. The bonding substrate involved in the embodiments of the present invention is a bonding substrate having a group III element nitride layer and a support substrate including a support layer, wherein the carbon concentration of the group III element nitride layer is 5 × 10⁻⁶. 17 atoms / cm 3 Above and 2×10 19 atoms / cm 3 the following.

[0009] 2. In the bonding substrate described in 1 above, the support layer may be composed of gallium nitride, aluminum nitride, silicon carbide, diamond carbon, or diamond.

[0010] 3. The bonding substrate described in 1 or 2 above can be disc-shaped with a diameter of 4 inches or more.

[0011] 4. In any one of the bonding substrates described in 1 to 3 above, the group III element nitride layer and the support layer included in the support substrate can be directly bonded.

[0012] 5. The bonding substrate described in any one of 1 to 4 above may have a bonding layer disposed between the group III nitride layer and the support layer included in the support substrate, the bonding layer being composed of silicon, tantalum oxide, aluminum oxide, aluminum nitride, silicon carbide, silicon aluminum oxynitride ceramic or silicon oxide.

[0013] 6. A semiconductor element according to another embodiment of the present invention comprises: a bonding substrate as described in any one of claims 1 to 5; and a device layer disposed on the bonding substrate.

[0014] 7. A method for manufacturing a bonding substrate according to another embodiment of the present invention includes: mixing a carbon substrate with a carbon concentration of 5 × 10⁻⁶. 17 atoms / cm 3 Above and 2×10 19 atoms / cm 3 The following group III nitride layer or group III nitride substrate is bonded to a support substrate including a support layer, wherein the arithmetic mean roughness Ra of the side of the group III nitride layer or group III nitride substrate bonded to the support substrate is less than 1.0 nm.

[0015] 8. In the manufacturing method of the bonding substrate described in 7 above, the support layer may be composed of gallium nitride, aluminum nitride, silicon carbide, diamond carbon, or diamond.

[0016] 9. In the method for manufacturing the bonding substrate described in 7 or 8 above, during the bonding process, activation treatment may be performed on the bonding surface of the group III nitride layer or the group III nitride substrate side and the bonding surface of the support substrate side, respectively.

[0017] Invention Effects

[0018] According to embodiments of the present invention, a bonding substrate with excellent bonding strength can be provided. Attached Figure Description

[0019] Figure 1A This is a simplified cross-sectional view showing the general structure of a bonding substrate according to one embodiment of the present invention.

[0020] Figure 1B It is shown Figure 1A A simplified cross-sectional view showing a detailed example of the support substrate.

[0021] Figure 1C This is a simplified cross-sectional view illustrating the general structure of a bonding substrate according to another embodiment of the present invention.

[0022] Figure 2AThis is a diagram illustrating an example of the manufacturing process of a bonding substrate according to one embodiment of the present invention.

[0023] Figure 2B It was immediately afterwards Figure 2A The image.

[0024] Figure 3A This is a diagram illustrating another example of the manufacturing process of a bonding substrate according to one embodiment of the present invention.

[0025] Figure 3B It was immediately afterwards Figure 3A The image.

[0026] Figure 4 This is a simplified cross-sectional view showing the general configuration of a semiconductor element according to one embodiment of the present invention.

[0027] Explanation of reference numerals in the attached figures

[0028] 10 Support substrate, 10b Bonding surface, 11 Support layer, 12 Substrate, 15 Bonding layer, 20 Group III nitride layer, 20b Bonding surface, 21 First main surface, 22 Second main surface, 30 Group III nitride substrate, 40 Another substrate, 51 Channel layer, 52 Barrier layer, 53 Device layer, 61 Source electrode, 62 Drain electrode, 63 Gate electrode, 100 Attachment substrate, 101 Bonding body, 200 HEMT device. Detailed Implementation

[0029] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings; however, the present invention is not limited to these embodiments. To make the description clearer, the drawings sometimes schematically represent the width, thickness, shape, etc., of various parts compared to the embodiments; however, this is merely an example and does not limit the interpretation of the present invention. Furthermore, regarding the drawings, the same reference numerals are used to label the same or equivalent elements, and sometimes repeated descriptions are omitted.

[0030] A. Laminating substrate

[0031] Figure 1A This is a simplified cross-sectional view illustrating the general structure of a bonding substrate according to one embodiment of the present invention. The bonding substrate 100 includes a support substrate 10 and a Group III nitride layer 20 made of a Group III nitride. The bonding substrate 100 comprises: the Group III nitride layer 20 having a first main surface 21 and a second main surface 22 facing each other; and the support substrate 10 disposed on the second main surface 22 side of the Group III nitride layer 20. The bonding substrate 100 can be obtained by bonding the support substrate 10 and the Group III nitride layer 20.

[0032] The support substrate 10 includes at least a support layer. The support layer in the support substrate 10 can be made of, for example, gallium nitride, aluminum nitride, silicon carbide, diamond, or diamond carbon. With such a support layer, a bonding substrate 100 with excellent bonding strength to the group III nitride layer 20 can be obtained. In one embodiment, the support layer can be made of a material different from the material constituting the group III nitride layer 20 (hereinafter sometimes referred to as a dissimilar material). By adopting such a configuration, for example, a bonding substrate 100 that satisfies characteristics (e.g., high heat dissipation) that cannot be achieved solely with the group III nitride layer 20 can be obtained. For example, the support layer is preferably made of silicon carbide or aluminum nitride. These materials can produce a bonding substrate 100 with high thermal conductivity, for example, excellent heat dissipation.

[0033] The thickness of the support substrate 10 is preferably 100 μm or more and 1000 μm or less, more preferably 200 μm or more and 1000 μm or less. When the support substrate 10 does not contain any layers other than the support layer (when the support substrate 10 is composed only of the support layer), the thickness of the support substrate 10 is equivalent to the thickness of the support layer. When the support substrate 10 does not contain any layers other than the support layer, the support substrate (support layer) 10 is preferably made of gallium nitride, aluminum nitride, silicon carbide, or diamond. Figure 1B As shown, when the support substrate 10 is a stack of support layer 11 and substrate 12, the thickness of support layer 11 is preferably 20 μm or more and 300 μm or less, more preferably 20 μm or more and 100 μm or less. The substrate that may be included in the support substrate 10 can be made of any suitable material. The substrate 12 that may be included in the support substrate 10 is preferably made of, for example, silicon, andalusite, sapphire, HICERAM, alumina, aluminum oxynitride, gallium nitride, silicon carbide, aluminum nitride, or diamond. When the support substrate 10 is a stack of support layer 11 and substrate 12, in the bonding substrate 100, the support substrate 10 is arranged such that the support layer 11 is located on the side of the group III nitride layer 20. Specifically, the support substrate 10 is bonded as described above with its support layer 11 located on the side of the group III nitride layer 20.

[0034] The support layer included in the support substrate 10 can be made of a single crystal, a polycrystalline material, an amorphous material, or a combination thereof. From the viewpoint of obtaining superior bonding strength, the support layer is preferably made of a single crystal. When the support layer is made of a single crystal, its crystal orientation and the crystal orientation of the Group III nitride layer 20, which can be formed by crystallizing Group III nitrides, can be set to any suitable configuration. In addition, the deviation orientation (direction of the deviation angle) of the support layer and the deviation orientation of the Group III nitride layer 20 can be set to any suitable configuration. The deviation angle of the support layer and the deviation angle of the Group III nitride layer 20 can each be set to any suitable value.

[0035] Typically, the Group III nitride layer 20 is composed of Group III nitride crystals. Typically, the Group III nitride crystals have a wurtzite-type crystal structure of the hexagonal crystal system. In the Group III nitride crystals, typically, the <0001> direction is the c-axis direction, the <1-100> direction is the m-axis direction, and the <11-20> direction is the a-axis direction. Furthermore, the crystal plane orthogonal to the c-axis is the c-plane, the crystal plane orthogonal to the m-axis is the m-plane, and the crystal plane orthogonal to the a-axis is the a-plane. In one embodiment, the thickness direction of the Group III nitride layer 20 is parallel or substantially parallel to the c-axis, the first principal plane 21 is a Group III polar plane on the (0001) plane side, and the second principal plane 22 is a nitrogen polar plane on the (000-1) plane side. The first principal plane 21 can be parallel to the (0001) plane or inclined relative to the (0001) plane. The tilt angle of the first principal surface 21 relative to the (0001) surface is, for example, less than 10°, less than 5°, less than 2°, or less than 1°. The second principal surface 22 may be parallel to the (000-1) surface or tilted relative to the (000-1) surface. The tilt angle of the second principal surface 22 relative to the (000-1) surface is, for example, less than 10°, less than 5°, less than 2°, or less than 1°.

[0036] In one embodiment, the thickness of the group III nitride layer 20 is preferably 0.5 μm or more and 10 μm or less, more preferably 0.5 μm or more and 5 μm or less. In another embodiment, the thickness of the group III nitride layer 20 is preferably 100 μm or more and 1000 μm or less, more preferably 200 μm or more and 1000 μm or less.

[0037] Group III elements that constitute the aforementioned group III nitrides include, for example, aluminum (Al), gallium (Ga), and indium (In). These group III elements can be used alone or in combination of two or more. Specific examples of group III nitrides include aluminum nitride (Al). x N), gallium nitride (Ga)y N), Indium nitride (In) z N), aluminum gallium nitride (Al) x Ga y N), gallium indium nitride (GaN) y In z N), aluminum indium nitride (Al) x In z N), aluminum gallium indium nitride (Al) x Ga y In z N). It should be noted that, representatively, among the chemical formulas in parentheses, x + y + z = 1.

[0038] The group III nitride layer 20 contains carbon. Because the group III nitride layer 20 contains carbon, the bonding substrate 100 can exhibit excellent bonding strength. The carbon concentration of the group III nitride layer 20 is preferably 5 × 10⁻⁶. 17 atoms / cm 3 The above is preferred to be 1×10 18 atoms / cm 3 The above is further preferred to be 2×10 18 atoms / cm 3 That's all. On the other hand, the carbon concentration of the Group III nitride layer 20 is preferably 2 × 10⁻⁶. 19 atoms / cm 3 Hereinafter, 1×10 is more preferred. 19 atoms / cm 3 The following describes how a concentration like this ensures the crystallinity of the Group III nitride layer 20. The carbon concentration in the thickness direction of the Group III nitride layer 20 can be uniform or varied. For example, the carbon concentration in the thickness direction of the Group III nitride layer 20 can vary periodically, continuously, or in stages within the aforementioned range. Furthermore, regions with different carbon concentrations than other regions can be locally formed in the thickness direction of the Group III nitride layer 20.

[0039] Regarding carbon concentration, for example, it can be determined using secondary ion mass spectrometry (SIMS).

[0040] The Group III nitride layer 20 can be doped with elements other than carbon. Specifically, the Group III nitride layer 20 can contain elements other than carbon as dopants. Examples of such dopants include transition elements such as zinc (Zn), iron (Fe), manganese (Mn), vanadium (V), chromium (Cr), cobalt (Co), and nickel (Ni). These dopants can be used alone or in combination of two or more.

[0041] The group III nitride layer 20 can be semi-insulating. In this case, the resistivity of the group III nitride layer 20 is, for example, 1 × 10⁻⁶. 5 Ω·cm or more and 1×10 14 Below Ω·cm, preferably 1×10 6 Ω·cm or higher, more preferably 1×10 7 Ω·cm or higher.

[0042] Resistivity can be measured using any suitable method. Examples of resistivity measurement methods include the capacitance method, the two-terminal method, and the double-ring electrode method. In one embodiment, the capacitance method is preferred. According to the capacitance method, resistivity can be determined without damaging the object being measured. Specifically, the object being measured is inserted into a capacitor consisting of a probe and a stage, a pulse voltage is applied, the time change of the charge on the object is measured, and the resistivity is calculated based on the measured value. Since the probe does not contact the object being measured, the resistivity can be determined without forming an ohmic contact electrode. It should be noted that the spatial resolution of the probe can be approximately 1 mm to 10 mm. Methods for determining resistivity are described, for example, in the non-patent literature *R. Stibal et al., “Contactless evaluation of semi-insulating GaAs waferresistivity using the time-dependent charge measurement” Semiconductor Science and Technology 6 p995 (1991)*.

[0043] The bonding substrate 100 may further have any layers. The type, function, number, combination, and configuration of such layers can be appropriately set according to the purpose. For example, the bonding substrate 100 may have a device layer formed on the group III nitride layer 20.

[0044] Additionally, for example, the bonding substrate 100 can be as follows: Figure 1CThe substrate shown has a bonding layer 15 disposed between a support layer and a group III nitride layer 20 included in the support substrate 10. Preferably, the bonding layer 15 constituting the bonding substrate 100 is made of silicon, tantalum oxide, aluminum oxide, aluminum nitride, silicon carbide, silicon aluminum oxynitride ceramic, or silicon oxide (e.g., SiO2). x (0 < x ≤ 2). Silicon-aluminum-oxygen-nitrogen ceramics are ceramics obtained by sintering a mixture of silicon nitride and aluminum oxide, for example, those having a silicon content of 0 < x ≤ 2. 6－w Al w O w N 8－w The composition is indicated by w. Specifically, the silicon-aluminum-oxygen-nitrogen ceramic has a composition in which alumina is mixed in silicon nitride, where w represents the mixing ratio of alumina. w is preferably 0.5 or more and 4.0 or less.

[0045] The thickness of the bonding layer is, for example, 2 nm to 1 μm, preferably 5 nm to 200 nm. The bonding layer can be formed using any suitable method. For example, it can be formed using physical evaporation such as sputtering, vacuum evaporation, ion beam assisted evaporation (IAD), chemical evaporation, or atomic layer deposition (ALD). The bonding layer can be formed at, for example, room temperature (25°C) to 300°C.

[0046] The bonding substrate 100 can be manufactured in any suitable shape. In one embodiment, it can be manufactured in a so-called wafer-like shape (disk-shaped). Regarding the bonding substrate 100, positioning edges or cutouts can be formed on a portion of it to display crystal orientation (e.g., the crystal orientation of a wafer). The size of the bonding substrate 100 can be appropriately set according to the purpose. For example, the diameter of the wafer is 50 mm to 200 mm, preferably 100 mm or more, or 4 inches or more. Even at such a large size, the bonding substrate 100 can still exhibit excellent bonding strength.

[0047] B. Manufacturing Method

[0048] The aforementioned bonding substrate can be obtained, for example, by bonding a group III nitride layer and a support substrate including a support layer. Figure 2A and Figure 2B This is a diagram illustrating an example of the manufacturing process of a bonding substrate according to one embodiment of the present invention. Figure 2A As shown, a support substrate 10 and a group III element nitride layer 20 are prepared and directly bonded together, as shown. Figure 2BAs shown, a bond 101 (attached substrate 100) is obtained, consisting of a support substrate 10 and a group III nitride layer 20. In the example shown, when bonded to the support substrate 10, the group III nitride layer 20 is integrated with another substrate 40. Furthermore, after bonding the group III nitride layer 20 and the support substrate 10, the other substrate 40 can be removed from the group III nitride layer 20 (bonded body 101).

[0049] The group III nitride layer 20, integrated with another substrate 40, is formed using, for example, a vapor phase growth method. Specific examples of vapor phase growth methods include: metal-organic chemical vapor deposition (MOCVD), hydride vapor phase growth (HVPE), pulsed excitation deposition (PXD), molecular beam epitaxy (MBE), evaporation, and sublimation. Among these, MOCVD is preferred.

[0050] When forming the group III nitride layer 20 using the above-described MOCVD method, an organometallic (MO) source gas can be used as the group III element source. For example, when forming a gallium nitride layer using MOCVD, trimethylgallium (TMG) can be used as the Ga source. Furthermore, ammonia can be used as the nitrogen source. Additionally, hydrogen or nitrogen can be used as the carrier gas. The formation temperature for forming the group III nitride layer 20 using the MOCVD method can be adjusted, for example, within the range of 500°C to 1200°C.

[0051] Typically, the group III nitride layer 20 can be formed using a substrate (not shown). In one embodiment, after the group III nitride layer 20 is formed on the substrate, another substrate 40 is integrated with the group III nitride layer 20 using any suitable method, and then the substrate is removed from the group III nitride layer 20. Typically, the group III nitride layer 20 and the other substrate 40 can be integrated using an adhesive. Examples of methods for removing the substrate from the group III nitride layer 20 include: machining such as grinding and polishing, slicing based on wire saws or lasers, and laser peeling based on laser irradiation. In the case of laser peeling, for example, the group III nitride layer 20 is formed after a peeling layer capable of absorbing laser light is formed on the substrate.

[0052] In addition, for example, regarding the aforementioned bonding substrate, by bonding a group III nitride substrate and a support substrate including a support layer, and by thinning the group III nitride substrate as needed, a bonding substrate having a group III nitride layer and a support substrate can be obtained. Figure 3A and Figure 3BThis is a diagram illustrating another example of the manufacturing process of a bonding substrate according to one embodiment of the present invention. (See diagram below.) Figure 3A As shown, a support substrate 10 and a group III element nitride substrate 30 are prepared and directly bonded together, as shown. Figure 3B As shown, a bonding body 101 (adhesive substrate 100) is obtained, consisting of a support substrate 10 and a group III nitride substrate 30. After bonding, the bonding body 101 can be subjected to any appropriate processing to obtain the adhesive substrate 100. Specifically, after bonding, the group III nitride substrate 30 can be thinned by grinding, polishing, etc., to obtain a group III nitride layer 20, or the group III nitride substrate 30 can be directly set as a group III nitride layer 20.

[0053] The thickness of the group III nitride substrate 30 is, for example, 100 μm or more and 1000 μm or less. The group III nitride substrate 30 can be a substrate fabricated using any suitable method. For example, the group III nitride substrate 30 can be formed using hydride vapor phase growth (HVPE).

[0054] Although not illustrated, when a bonding layer is provided, a bonding substrate can be obtained by bonding a support substrate with a bonding layer to a group III nitride layer or a group III nitride substrate. Alternatively, a bonding substrate can be obtained by bonding a support substrate to a group III nitride layer or a group III nitride substrate with a bonding layer. Furthermore, a bonding substrate can be obtained by bonding a first bonding layer formed on the support substrate to a second bonding layer formed on the group III nitride layer or the group III nitride substrate.

[0055] <Joining>

[0056] In the above-mentioned direct bonding, the bonding surface 10b of the support substrate 10 and the bonding surface 20b of the group III nitride layer 20 or the group III nitride substrate 30 are preferably activated by any appropriate activation treatment.

[0057] Typically, the activation process described above is performed by irradiating a neutral beam. Preferably, an apparatus similar to that described in Japanese Patent Application Publication No. 2014-086400 is used to generate a neutral beam, which is then used to irradiate the device for activation. Specifically, a saddle-type high-speed atomic beam (FAB) source is used as the beam source, and inert gases such as argon or xenon are introduced into the chamber. A high voltage is applied to the electrodes from a DC power supply. As a result, the saddle-type electric field generated between the electrodes (positive electrode) and the casing (negative electrode) causes electrons to move, generating a beam of atoms and ions based on the inert gas. Upon reaching the grid, the ion beam is neutralized at the grid, thus the beam of neutral atoms is emitted from the high-speed atomic beam source. The voltage used for activation by beam irradiation is preferably 0.5 kV to 2.0 kV, and the current used for activation by beam irradiation is preferably 50 mA to 200 mA.

[0058] After activation treatment, the bonding surface 10b of the support substrate 10 is brought into contact with the bonding surface 20b of the group III nitride layer 20 or group III nitride 30, and pressure is applied, thereby enabling direct bonding. The contact and pressure application of the bonding surfaces are preferably performed in a vacuum atmosphere. The temperature at this time is typically room temperature. Specifically, it is preferably 20°C or higher and 40°C or lower, more preferably 25°C or higher and 30°C or lower. The applied pressure is preferably 100N to 20000N.

[0059] Although not illustrated, when a bonding layer is provided, the bonding surfaces of the bonding layer and the bonding surfaces of the supporting substrate or the group III nitride layer or the group III nitride substrate are preferably activated by any suitable activation treatment. Alternatively, the bonding surfaces of the first bonding layer and the second bonding layer are preferably activated by any suitable activation treatment. After activation, the bonding surfaces are brought into contact with each other and pressure is applied, thereby allowing direct bonding. The activation treatment and bonding conditions can be the same as described above.

[0060] During bonding, the bonding surfaces are preferably flat. Specifically, the bonding surfaces on the support substrate 10 side and the bonding surfaces on the group III nitride layer 20 or group III nitride substrate 30 side are preferably flat. By making the bonding surfaces flat, excellent bonding strength can be achieved. The arithmetic mean roughness Ra of each bonding surface is, for example, 2.0 nm or less, preferably 1.0 nm or less, more preferably 0.7 nm or less, further preferably 0.5 nm or less, and particularly preferably 0.3 nm or less. Methods for planarizing the surfaces of the support substrate 10, group III nitride layer 20, and group III nitride substrate 30 include, for example, mirror polishing based on chemical mechanical polishing (CMP), fine polishing (lap polishing), etc. It should be noted that when a bonding layer is provided, regarding the bonding surfaces of the bonding layer, since the surfaces of the support substrate 10, group III nitride layer 20, and group III nitride substrate 30 on which the bonding layer film is formed are flat, the surface of the bonding layer film formed thereon can also be flat.

[0061] Regarding the side 20b of the bonding support substrate 10 of the group III nitride layer 20 or the group III nitride substrate 30, through its carbon concentration of 2×10 19 atoms / cm 3 The following method can achieve the aforementioned arithmetic mean roughness Ra well. Specifically, the carbon concentration of the group III nitride layer 20 or the group III nitride substrate 30 is 2 × 10⁻⁶. 19 atoms / cm 3 The following can ensure the crystal quality of the group III nitride layer 20 or the group III nitride substrate 30, and the above-mentioned arithmetic mean roughness Ra can be well achieved by planarization process.

[0062] During the bonding process, it is preferable to clean the bonding surfaces to remove any residue of abrasive. Examples of cleaning methods include wet cleaning, dry cleaning, and brushing. Brushing is preferred for ease and efficiency. A specific example of brushing is a method where, after using a cleaning agent (e.g., Lion's San Wash series), a solvent (e.g., a mixture of acetone and isopropanol (IPA)) is used to clean the surfaces using a brushing machine.

[0063] C. Uses

[0064] Typically, the aforementioned bonding substrate can be applied to any suitable semiconductor device. Specifically, any suitable device layer can be formed on the bonding substrate. Typically, the device layer is formed by epitaxial growth of crystals. As described above, the bonding strength of the bonding substrate is excellent; therefore, even when exposed to high temperatures (e.g., above 1000°C) during the formation of the device layer, defects such as interlayer delamination in the bonding substrate are suppressed, enabling the manufacture of semiconductor devices with good yield.

[0065] Figure 4 This is a simplified cross-sectional view illustrating the general structure of a semiconductor device according to one embodiment of the present invention, using a high electron mobility transistor (HEMT) as an example. The HEMT device 200 includes: a bonding substrate 100, a device layer 53 sequentially comprising a channel layer 51 and a barrier layer 52, and a source electrode 61, a drain electrode 62, and a gate electrode 63 disposed on the device layer 53. These electrodes can each be metal electrodes having a thickness of approximately tens of nm to hundreds of nm.

[0066] Typically, device layer 53 is composed of a group III nitride, which can be formed by epitaxial growth of crystals over group III nitride layer 20. The thickness of channel layer 51 is, for example, 50 nm to 5 μm. The thickness of barrier layer 52 is, for example, 2 nm to 40 nm. In one embodiment, channel layer 51 is preferably composed of gallium nitride. Furthermore, barrier layer 52 is preferably composed of at least one selected from aluminum gallium nitride, aluminum indium nitride, and aluminum indium gallium nitride.

[0067] As a method for forming (growing) the device layer 53, vapor phase growth can be representatively employed. Specific examples of vapor phase growth methods include: metal-organic chemical vapor deposition (MOCVD), hydride vapor phase growth (HVPE), pulsed excitation deposition (PXD), molecular beam epitaxy (MBE), evaporation, and sublimation. Among these, MOCVD is preferred. The formation temperature (growth temperature) of the device layer is, for example, 800°C or higher and 1200°C or lower, preferably 1000°C or higher.

[0068] Example

[0069] The present invention will now be specifically described by way of examples; however, the present invention is not limited to these examples. It should be noted that the carbon concentration and arithmetic mean roughness Ra are values ​​obtained using the measurement methods described below.

[0070] <Carbon Concentration>

[0071] The carbon concentration of the gallium nitride layer was determined using secondary ion mass spectrometry (SIMS). The determination conditions are as follows.

[0072] (Measurement conditions)

[0073] Types of secondary ion mass spectrometers: sector magnetic field type

[0074] • Types of primary ions: Cs ＋

[0075] Arithmetic mean roughness Ra

[0076] The arithmetic mean roughness Ra of the substrate was measured using an atomic force microscope (AFM5400L manufactured by Hitachi High Technology Co., Ltd.) with a field of view of 10 μm × 10 μm.

[0077] [Example 1]

[0078] (Fabrication of gallium nitride substrate)

[0079] Prepare a 4-inch diameter c-plane sapphire substrate. On this sapphire substrate, form a 2μm thick gallium nitride film using MOCVD to create a seed substrate.

[0080] Gallium nitride crystallization is performed on a seed substrate using a crystallization manufacturing apparatus. The crystallization manufacturing apparatus includes: a pressure vessel capable of supplying high-pressure nitrogen gas; a rotating stage capable of rotating within the pressure vessel; an outer container placed on the rotating stage; and a crystallization furnace for placing the outer container in a desired temperature environment.

[0081] The obtained seed substrate was placed in an alumina crucible within a glove box under a nitrogen atmosphere. Next, 40g of metallic gallium and 80g of metallic sodium were melted separately in the glove box and filled into the crucible. The seed substrate was then immersed in the flux melt and covered with an alumina plate. In this state, the crucible was placed into a stainless steel inner container, and then into a stainless steel outer container capable of housing the inner container. The outer container was closed with a lid equipped with a nitrogen inlet tube. In this state, the outer container was placed on a rotating stage within the crystallization apparatus, and the pressure vessel lid of the crystallization apparatus was closed to seal it.

[0082] Next, the heater section is heated to a uniform temperature of 875°C within the crystallization furnace of the crystallization fabrication apparatus, while nitrogen gas is introduced from a nitrogen cylinder into the pressure vessel until a pressure of 4 MPa is reached, and the outer vessel is rotated horizontally. This state is maintained for 70 hours to allow gallium nitride crystals to grow.

[0083] Afterward, allow it to cool naturally to room temperature and depressurize to atmospheric pressure. Then, open the lid of the pressure-resistant container and remove the crucible. Remove the solidified metallic sodium from the crucible and recover the seed substrate with gallium nitride crystals grown on it.

[0084] Next, at room temperature, an ultraviolet laser is irradiated onto the sapphire substrate side of the seed substrate on which gallium nitride crystals have grown, decomposing the gallium nitride film on the seed substrate and thus separating the grown gallium nitride crystals from the sapphire substrate. The separated gallium nitride crystals are fixed on a ceramic processing platform, and two main surfaces are ground and planarized using a grinding and fine grinding device to fabricate a gallium nitride substrate (base substrate) with a diameter of 4 inches and a thickness of 350 μm.

[0085] (Formation of gallium nitride layer)

[0086] Using MOCVD, a 1000 nm thick release layer was formed on the main surface of the gallium polar side of the obtained gallium nitride substrate, which was decomposed by irradiation with a 532 nm wavelength laser. After the release layer was formed, a carbon (C)-doped gallium nitride layer was continuously formed using MOCVD. Specifically, the MOCVD furnace was set with a hydrogen flow, and under conditions of 0.3 atm furnace pressure and 1050 °C substrate temperature, ammonia and trimethylgallium (TMG) were used to form a 3 μm thick gallium nitride layer with a carbon concentration of 2 × 10⁻⁶. 18 atoms / cm 3 A gallium nitride layer is formed to obtain an epitaxial substrate.

[0087] On the gallium nitride (GaN) layer side of the obtained epitaxial substrate, an adhesive is used to bond the sapphire substrate, and then the GaN substrate is peeled off from the epitaxial substrate. Specifically, the epitaxial substrate is irradiated with a laser from the GaN substrate side, and after laser irradiation, the epitaxial substrate is immersed in a 50°C water bath to peel off the GaN substrate.

[0088] The surface of the gallium nitride (GaN) substrate after peeling off the GaN layer was polished using CMP until the GaN layer thickness reached 2 μm. The arithmetic mean roughness Ra of the GaN layer surface (bonding surface) was 0.35 nm.

[0089] (Jointing with the support substrate)

[0090] A silicon carbide substrate with a diameter of 4 inches and a thickness of 500 μm was prepared as a support substrate. The arithmetic mean roughness Ra of the surface (bonding surface) of the silicon carbide substrate was 0.24 nm.

[0091] Next, the gallium nitride layer integrated with the sapphire substrate and the support substrate will be directly bonded. Specifically, after cleaning the bonding surfaces of the gallium nitride layer and the support substrate, the two substrates are placed in a vacuum chamber and evacuated to 10 °C. －6 After approximately 1000 N, the bonding surfaces of the two substrates are irradiated with a high-speed atomic beam (accelerating voltage 1 kV, Ar flow rate 27 sccm) for 120 seconds. After irradiation, the irradiated surfaces of the two substrates are aligned, and a pressure of 10000 N is applied for 2 minutes to bond the two substrates together.

[0092] The adhesive is then decomposed by heating, the sapphire substrate is removed from the resulting bond, and the surface of the gallium nitride layer is cleaned to obtain the bonding substrate.

[0093] [Example 2]

[0094] In the formation of gallium nitride layers based on MOCVD, by changing the formation conditions, a carbon concentration of 7 × 10⁻⁶ was obtained. 17 atoms / cm 3 A gallium nitride layer was formed, and otherwise, a bonding substrate was obtained in the same manner as in Example 1. It should be noted that the arithmetic mean roughness Ra of the bonding surface of the gallium nitride layer is 0.40 nm.

[0095] [Example 3]

[0096] In the fabrication of the gallium nitride substrate, the diameter of the sapphire substrate was set to 6 inches. During the formation of the gallium nitride layer based on the MOCVD method, the formation conditions were changed to obtain a layer with a thickness of 2 μm and a carbon concentration of 5 × 10⁻⁶, starting from the gallium nitride substrate side. 18 atoms / cm 3 The first gallium nitride layer is 1 μm thick and has a carbon concentration of 8 × 10⁻⁶. 18 atoms / cm 3 The second gallium nitride layer is a gallium nitride layer, and a silicon carbide substrate with a diameter of 6 inches and a thickness of 500 μm is used as the support substrate. Otherwise, the bonding substrate is obtained in the same manner as in Example 1. It should be noted that the polished gallium nitride layer has a first gallium nitride layer with a thickness of 1 μm and a second gallium nitride layer with a thickness of 1 μm, and the arithmetic mean roughness Ra of the bonding surface is 0.35 nm.

[0097] [Example 4]

[0098] As the support substrate, a 4-inch diameter, 500μm thick polycrystalline aluminum nitride substrate (with an arithmetic mean roughness Ra of 1.20nm at the bonding surface) was used. Furthermore, a 4μm thick gallium nitride layer was obtained during the formation of the gallium nitride layer using the MOCVD method. Otherwise, the bonding substrate was obtained in the same manner as in Example 1. It should be noted that the thickness of the polished gallium nitride layer was set to 3μm here.

[0099] [Comparative Example 1]

[0100] In the formation of gallium nitride layers based on MOCVD, by changing the formation conditions, a carbon concentration of 3×10⁻⁶ was obtained. 17 atoms / cm 3 A gallium nitride layer was formed, and otherwise, a bonding substrate was obtained in the same manner as in Example 1. It should be noted that the arithmetic mean roughness Ra of the bonding surface of the gallium nitride layer is 0.50 nm.

[0101] [Comparative Example 2]

[0102] In the formation of gallium nitride layers based on MOCVD, by changing the formation conditions, a carbon concentration of 2.5 × 10⁻⁶ was obtained. 19 atoms / cm 3 A gallium nitride layer was formed, and otherwise, a bonding substrate was obtained in the same manner as in Example 1. It should be noted that the arithmetic mean roughness Ra of the bonding surface of the gallium nitride layer is 2.21 nm.

[0103] <Evaluation>

[0104] The bonding strength of the laminated substrates obtained in the examples and comparative examples was evaluated using the crack opening method.

[0105] Specifically, using thickness (t) b A 100 μm blade was used to mechanically peel the gallium nitride substrate from the support substrate. The blade was inserted into the end face of the bonding substrate, and the distance (L) from the blade tip to the most severely peeled area was measured. The surface energy (γ) was calculated using the following formula and set as the bonding strength. The evaluation results are summarized in Table 1.

[0106]

Mathematical Formula 1

[0107]

[0108] γ: Surface energy (J / m 2 )

[0109] L: Distance from the blade tip to the area with the most severe peeling (μm)

[0110] t w1 Thickness (μm) of gallium nitride substrate

[0111] t w2 Thickness of the supporting substrate (μm)

[0112] E1: Young's modulus (MPa) of gallium nitride substrate

[0113] E2: Young's modulus of the supporting substrate (MPa)

[0114] t b Blade thickness (μm)

[0115] Table 1

[0116]

[0117] Industrial availability

[0118] The bonding substrates described in the embodiments of the present invention can be applied, for example, to semiconductor devices.

Claims

1. A bonding substrate having a group III element nitride layer and a support substrate including a support layer, The bonding substrate is characterized in that... The carbon concentration of the group III nitride layer is 5 × 10⁻⁶. 17 atoms / cm 3 Above and 2×10 19 atoms / cm 3 the following.

2. The bonding substrate according to claim 1, characterized in that, The support layer is composed of gallium nitride, aluminum nitride, silicon carbide, diamond carbon, or diamond.

3. The bonding substrate according to claim 1, characterized in that, The bonding substrate is disc-shaped with a diameter of 4 inches or more.

4. The bonding substrate according to claim 1, characterized in that, The group III nitride layer and the support layer included in the support substrate are directly bonded.

5. The bonding substrate according to claim 1, characterized in that, The bonding substrate has a bonding layer disposed between the group III nitride layer and the support layer included in the support substrate. The bonding layer is composed of silicon, tantalum oxide, aluminum oxide, aluminum nitride, silicon carbide, silicon aluminum oxynitride ceramic, or silicon oxide.

6. A semiconductor element, characterized in that, have: The bonding substrate according to any one of claims 1 to 5; and A device layer is disposed on the bonding substrate.

7. A method for manufacturing a bonding substrate, characterized in that, include: With a carbon concentration of 5×10 17 atoms / cm 3 Above and 2×10 19 atoms / cm 3 The following group III nitride layers or group III nitride substrates are bonded to a support substrate including a support layer. The arithmetic mean roughness Ra of the side of the group III nitride layer or group III nitride substrate that is bonded to the supporting substrate is less than 1.0 nm.

8. The method for manufacturing a bonding substrate according to claim 7, characterized in that, The support layer is composed of gallium nitride, aluminum nitride, silicon carbide, diamond carbon, or diamond.

9. The method for manufacturing a bonding substrate according to claim 7, characterized in that, During the bonding process, activation treatment is performed on the bonding surface of the group III nitride layer or the group III nitride substrate side, and the bonding surface of the support substrate side, respectively.

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