Nitride semiconductor laminated structure precursor, nitride semiconductor laminated structure, semiconductor device, method of manufacturing nitride semiconductor laminated structure precursor, and method of manufacturing nitride semiconductor laminated structure

Abstract

To provide: a semiconductor laminated structure precursor for obtaining a semiconductor laminated structure that is excellent in bonding performance between a diamond substrate and a semiconductor layer and also excellent in heat dissipation and heat resistance; a semiconductor laminated structure; a semiconductor device; a method of manufacturing a semiconductor laminated structure precursor; and a method of manufacturing a semiconductor laminated structure.SOLUTION: A nitride semiconductor laminated structure precursor 1 includes a substrate 10 made of carbon, a semiconductor layer 20 made of gallium nitride, and an intermediate layer 30 located between the substrate 10 and the semiconductor layer 20, the substrate 10 and the semiconductor layer 20 being in contact with the intermediate layer 30. The intermediate layer 30 contains a metal M forming a compound with at least one of carbon and gallium nitride.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a nitride semiconductor stacked structure precursor, a nitride semiconductor stacked structure, a semiconductor device, a method for producing a nitride semiconductor stacked structure precursor, and a method for producing a nitride semiconductor stacked structure. [Background technology]

[0002] In recent years, with the trend toward higher power, higher speed, and higher integration of semiconductor devices, there is a demand for substrates for semiconductor device formation with high thermal conductivity. Diamond substrates with high thermal conductivity of 500 W / mK or more have been attracting attention as substrates for semiconductor device formation. In general, the surface of diamond substrates is rough, and there is a problem that it is difficult to bond to semiconductor layers.

[0003] To address such problems, for example, a method of bonding gallium nitride (GaN) and diamond in the manufacture of nitride semiconductor devices is being considered. As a method for bonding gallium nitride and diamond, for example, a method is known in which silicon (Si) is deposited on the bonding surface between gallium nitride and diamond, and GaN and diamond are bonded via the Si layer (for example, see Non-Patent Document 1). Also known is a method in which a silicon carbide (SiC) substrate on which a nitride semiconductor has been crystal-grown is thinned to 50 μm, and the SiC substrate is bonded to diamond via a 10 nm-thick titanium (Ti) layer (see, for example, Non-Patent Document 2). Also known is a method in which a SiC substrate into which hydrogen ions have been implanted is bonded to diamond, a SiC layer having a thickness of 1 μm to 30 μm is formed on the diamond by heat treatment, and then a nitride semiconductor layer is crystal-grown on the SiC layer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-139655 A [Non-patent literature]

[0005] [Non-Patent Document 1] Z. Cheng, et al., “Interfacial Thermal Conductance across Room-Temperature Bonded GaN-Diamond Interfaces for GaN-on-Diamond Devices,” ACS Appl. Mater. Interfaces 12, pp. 8376-8384 (2020). [Non-Patent Document 2] Yuichi Minoura, et al., “Surface activated bonding of SiC / diamond for thermal management of high-output power GaN HEMTs,” Jpn. J. Appl. Phys. 59, SGGD03 (2020). Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method described in Non-Patent Document 1, Si and GaN react (melt back) due to high-temperature heat treatment, and voids are generated at the bonding interface between Si and GaN. Therefore, this method has a problem in that it cannot apply the heat treatment required for manufacturing semiconductor elements. Furthermore, the methods described in Non-Patent Document 2 and Patent Document 1 have the problem that, because SiC is harder than Si, the irregularities on the diamond surface cannot be absorbed by SiC to firmly bond the nitride semiconductor layer and diamond.

[0007] The present invention has been made in consideration of the above circumstances, and provides a nitride semiconductor stack precursor for obtaining a nitride semiconductor stack having excellent adhesion between a diamond substrate and a semiconductor layer, and excellent heat dissipation and heat resistance, a nitride semiconductor stack, a semiconductor device, a method for manufacturing a nitride semiconductor stack precursor, and a method for manufacturing a nitride semiconductor stack. [Means for solving the problem]

[0008] The present invention has the following aspects. [1] A semiconductor device comprising: a substrate made of carbon; a semiconductor layer made of a nitride semiconductor containing gallium nitride; and an intermediate layer located between the substrate and the semiconductor layer; A nitride semiconductor stacked structure precursor in which the substrate and the semiconductor layer are in contact with the intermediate layer, The intermediate layer comprises a metal M that forms a compound with at least one of the carbon and the gallium nitride. [2] The nitride semiconductor stacked structure precursor according to [1], wherein the metal M is aluminum, manganese, magnesium or lithium, or an alloy containing the aluminum, manganese, magnesium or lithium. [3] A nitride semiconductor stacked structure in which a substrate made of carbon and a semiconductor layer made of a nitride semiconductor containing gallium nitride are bonded to each other via an intermediate layer containing a metal M that forms a compound with at least one of the carbon and the gallium nitride, the intermediate layer includes at least one of a compound A of the metal M and the carbon and a compound B of the metal M and the gallium nitride, A nitride semiconductor stacked structure comprising at least one of the compound A formed between the substrate and the intermediate layer, and the compound B formed between the intermediate layer and the semiconductor layer. [4] The nitride semiconductor stacked structure according to [3], wherein the metal M is aluminum, manganese, magnesium or lithium, or an alloy containing the aluminum, manganese, magnesium or lithium. [5] The nitride semiconductor stacked structure according to [4], wherein compound A is tetraaluminum tricarbide and compound B is aluminum gallium nitride. [6] A semiconductor device comprising the nitride semiconductor stacked structure according to any one of [3] to [5]. [7] a deposition step of depositing a metal M that forms a compound with at least one of the carbon and gallium nitride on at least a portion of one surface of a substrate made of carbon to form an intermediate layer; and forming a semiconductor layer on a surface of the intermediate layer, the semiconductor layer being made of a nitride semiconductor containing gallium nitride. [8] A method for producing a nitride semiconductor laminate structure, comprising: obtaining a nitride semiconductor laminate structure precursor by the method for producing a nitride semiconductor laminate structure precursor according to [7]; and subjecting the nitride semiconductor laminate structure precursor to a heat treatment at 500°C or higher. Effect of the Invention

[0009] According to the present invention, it is possible to provide a nitride semiconductor laminate structure precursor for obtaining a nitride semiconductor laminate structure having excellent bonding between a diamond substrate and a semiconductor layer, and excellent heat dissipation and heat resistance, a nitride semiconductor laminate structure, a semiconductor device, a method for manufacturing a nitride semiconductor laminate structure precursor, and a method for manufacturing a nitride semiconductor laminate structure. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view illustrating a nitride semiconductor stacked structure precursor according to one embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view illustrating a nitride semiconductor stacked structure according to one embodiment of the present invention. [Diagram 3] 1 is a cross-sectional view illustrating a semiconductor device according to an embodiment of the present invention. [Figure 4] 1 is a transmission electron microscope image of a cross section in the thickness direction of a nitride semiconductor laminate structure precursor in an example. [Diagram 5]FIG. 2 is a diagram showing the results of energy dispersive X-ray analysis of a cross section in the thickness direction of a nitride semiconductor laminate structure precursor in an example. [Figure 6] 1 is a transmission electron microscope image of a cross section in the thickness direction of a nitride semiconductor stacked structure after heat treatment at 600° C. in an example. [Figure 7] FIG. 2 is a diagram showing the results of energy dispersive X-ray analysis of a cross section in the thickness direction of a nitride semiconductor stacked structure after heat treatment at 600° C. in an example. [Figure 8] 2 is a transmission electron microscope image of a cross section in the thickness direction of a nitride semiconductor stacked structure after heat treatment at 1000° C. in an example. [Figure 9] FIG. 2 is a diagram showing the results of energy dispersive X-ray analysis of a cross section in the thickness direction of a nitride semiconductor stacked structure after heat treatment at 1000° C. in an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the nitride semiconductor laminate structure precursor, the nitride semiconductor laminate structure, the semiconductor device, the method for producing the nitride semiconductor laminate structure precursor, and the method for producing the nitride semiconductor laminate structure of the present invention will be described. It should be noted that the present embodiment is specifically described to allow a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[0012] [Nitride semiconductor laminated structure precursor] A nitride semiconductor stacked structure precursor according to one embodiment of the present invention has a substrate made of carbon, a semiconductor layer made of gallium nitride, and an intermediate layer located between the substrate and the semiconductor layer, the substrate and the semiconductor layer being in contact with the intermediate layer, and the intermediate layer contains a metal M that forms a compound with at least one of the carbon and the gallium nitride.

[0013] A nitride semiconductor laminated structure precursor according to one embodiment of the present invention will now be described with reference to the drawings, in which: Fig. 1 is a cross-sectional view that typically shows a nitride semiconductor laminated structure precursor according to one embodiment of the present invention. 1, the nitride semiconductor laminated structure precursor 1 of this embodiment has a substrate 10 made of carbon, a semiconductor layer 20 made of a nitride semiconductor containing gallium nitride, and an intermediate layer 30 located between the substrate 10 and the semiconductor layer 20. That is, in the nitride semiconductor laminated structure precursor 1 of this embodiment, the substrate 10 and the semiconductor layer 20 are bonded together via the intermediate layer 30.

[0014] Thickness T of the nitride semiconductor laminate precursor 1 1 is, for example, preferably 2 μm or more and 1000 μm or less, more preferably 5 μm or more and 700 μm or less, and further preferably 10 μm or more and 500 μm or less. 1 When the thickness T is equal to or greater than the lower limit, the physical strength of the nitride semiconductor laminated structure precursor 1 can be further increased. 1 When is equal to or less than the above upper limit, the size of the nitride semiconductor laminate structure precursor 1 can be made more compact. Thickness T 1 can be measured, for example, with a digital caliper. In this specification, "thickness T 1 " is the arithmetic mean value of the thickness at 10 randomly selected locations.

[0015] The substrate 10 is not particularly limited as long as it is a substrate made of carbon, and examples thereof include a diamond substrate, a graphite substrate, etc. Among these, a diamond substrate is preferred because it has high thermal conductivity and can efficiently dissipate heat generated by the semiconductor layer 20 in a semiconductor device using a nitride semiconductor laminate structure obtained by heat-treating the nitride semiconductor laminate structure precursor 1.

[0016] The thermal conductivity of the diamond substrate is, for example, preferably 500 W / m·K or more, more preferably 700 W / m·K or more, and even more preferably 1000 W / m·K or more. When the thermal conductivity of the diamond substrate is equal to or more than the lower limit, the heat dissipation of the semiconductor device can be further improved. The upper limit of the thermal conductivity of the diamond substrate is not particularly limited, and is, for example, 3000 W / m·K. The thermal conductivity of the diamond substrate can be measured by, for example, a temperature gradient method, a disk heat flow meter method, or the like. The thermal conductivity of the diamond substrate can be adjusted by the purity, crystallinity, type of crystal, density, or a combination thereof of the diamond constituting the diamond substrate.

[0017] Thickness T of the substrate 10 10 is, for example, preferably 10 μm or more and 500 μm or less, more preferably 30 μm or more and 400 μm or less, and further preferably 50 μm or more and 300 μm or less. 10 When the thickness T is equal to or greater than the lower limit, the physical strength of the nitride semiconductor laminated structure precursor 1 can be further increased. 10 When is equal to or less than the above upper limit, the size of the nitride semiconductor laminate structure precursor 1 can be made more compact. Thickness T 10 can be measured, for example, with a digital caliper. In this specification, "thickness T 10 " is the arithmetic mean value of the thickness at 10 randomly selected locations.

[0018] The semiconductor layer 20 is a layer made of a nitride semiconductor containing gallium nitride (GaN).

[0019] The thickness T of the semiconductor layer 20 20 is, for example, preferably 0.5 μm or more and 50 μm or less, more preferably 1 μm or more and 20 μm or less, and further preferably 2 μm or more and 10 μm or less. 20 When the thickness T is equal to or greater than the lower limit, the output of a semiconductor device using the nitride semiconductor laminate structure obtained by heat-treating the nitride semiconductor laminate structure precursor 1 can be further increased. 20When is equal to or less than the upper limit, the thermal resistivity of the gallium nitride constituting the semiconductor layer 20 suppresses a temperature rise in a semiconductor device using the nitride semiconductor laminate structure obtained by heat-treating the nitride semiconductor laminate structure precursor 1, and further improves the bond with the substrate 10. This further improves the heat dissipation and heat resistance of the semiconductor device. Thickness T 20 can be obtained, for example, by observing a cross section of the nitride semiconductor laminated structure precursor 1 in the thickness direction with an electron microscope or the like. In this specification, "thickness T 20 " is the arithmetic mean value of the thickness at 10 randomly selected locations.

[0020] The intermediate layer 30 contains a metal M that forms a compound with at least one of the carbon constituting the substrate 10 and the gallium nitride constituting the semiconductor layer 20 by heat treatment.

[0021] Metal M forms a compound with at least one of carbon constituting substrate 10 and gallium nitride constituting semiconductor layer 20 through heat treatment, and has a Young's modulus less than that of silicon (Si) (160 GPa). Examples of such metal M include metals such as aluminum (Al), manganese (Mn), magnesium (Mg), and lithium (Li), and alloys containing these metals. Examples of alloys include Al-Ca alloys. Among these, aluminum is preferred because it can absorb the unevenness (surface roughness) of the surface (one surface 10a) of the substrate 10 from carbon, and can easily form a compound with the carbon constituting the substrate 10 and the gallium nitride constituting the semiconductor layer 20 by heating. However, since pure aluminum does not exist, alloys containing aluminum are preferred, and for example, alloys with an aluminum component ratio of 85% or more as specified in JIS H4000:2014 are more preferred, and alloys with high aluminum purity of alloy numbers 1000 to 1099 as specified in JIS H4000:2014 are particularly preferred.

[0022] Furthermore, the intermediate layer 30 may have a single layer structure or a multilayer structure, so long as it contains the metal M. In the case of a single layer structure, the intermediate layer 30 is composed of a layer containing only the metal M (hereinafter referred to as "layer α1"). In the case of a multilayer structure, the intermediate layer 30 has the layer α1 and a layer β1 different from the layer α1, and the layer α1 may be present so as to be in contact with the substrate 10 and the semiconductor layer 20. For example, the intermediate layer 30 may be one in which the layer α1, layer β1, and layer α1 are laminated in this order. Examples of materials constituting the layer β1 include silicon (Si) and silicon carbide (SiC).

[0023] Thickness T of the intermediate layer 30 30 is, for example, preferably 1 nm or more and 100 nm or less, more preferably 2 nm or more and 50 nm or less, and further preferably 5 nm or more and 20 nm or less. 30 When the thickness T is equal to or greater than the lower limit, the influence of surface irregularities is mitigated and a strong bond is formed. 30 When it is equal to or less than the upper limit, the thermal resistance caused by the intermediate layer 30 can be sufficiently reduced. Thickness T 30 can be obtained, for example, by observing a cross section of the nitride semiconductor laminated structure precursor 1 in the thickness direction with an electron microscope or the like. In this specification, "thickness T 30 " is the arithmetic mean value of the thickness at 10 randomly selected locations.

[0024] According to the nitride semiconductor laminated structure precursor 1 of this embodiment, the substrate 10 made of carbon and the semiconductor layer 20 made of a nitride semiconductor containing gallium nitride are bonded via the intermediate layer 30, and the intermediate layer 30 contains the metal M that forms a compound with at least one of the carbon and the gallium nitride, so that even if one surface 10a of the substrate 10 has irregularities, the substrate 10 and the semiconductor layer 20 can be firmly bonded via the intermediate layer 30. Furthermore, even if the nitride semiconductor laminated structure precursor 1 of this embodiment is subjected to a heat treatment to form a nitride semiconductor laminated structure, no voids due to meltback are generated at the boundary between the intermediate layer 30 and the semiconductor layer 20, and the obtained nitride semiconductor laminated structure has excellent heat resistance.

[0025] [Method of manufacturing a nitride semiconductor laminated structure precursor] A method for producing a nitride semiconductor stacked structure precursor according to one embodiment of the present invention includes a deposition step of depositing a metal M that forms a compound with at least one of carbon and gallium nitride on at least a portion of one surface of a substrate made of carbon to form an intermediate layer, and a semiconductor layer formation step of forming a semiconductor layer made of a nitride semiconductor containing gallium nitride on a surface of the intermediate layer.

[0026] Hereinafter, a method for producing a nitride semiconductor stacked structure precursor according to one embodiment of the present invention will be described with reference to FIG.

[0027] The depositing step is a step of depositing the metal M on at least a portion of one surface 10a of the substrate 10 to form the intermediate layer 30. Examples of the method for depositing the metal M include sputtering, vacuum deposition, chemical vapor deposition, and physical vapor deposition. The method for depositing the metal M is preferably a sputtering method, since it can make the thickness of the intermediate layer 30 uniform and thinner.

[0028] Examples of the sputtering method include a two-pole method, a magnetron method, reactive sputtering, ion beam sputtering, electron cyclotron resonance (ECR) sputtering, etc. As the sputtering method, the magnetron method is preferable because it allows the metal M to be stably deposited.

[0029] The semiconductor layer forming step is a step of forming the semiconductor layer 20 made of gallium nitride on the surface of the intermediate layer 30 following the above-mentioned deposition step. Examples of a method for forming (bonding) the semiconductor layer 20 to the surface of the intermediate layer 30 include a surface activated bonding (SAB) method, a high pressure bonding method, and a high vacuum bonding method. In the SAB method, the surfaces to be joined are cleaned with chemicals and pure water, activated with plasma or ions in a vacuum chamber, and then bonded in a low-temperature atmosphere ranging from room temperature (e.g., 25°C) to approximately 400°C. In the high-pressure bonding method, the surfaces to be bonded are cleaned with chemicals and pure water, and then bonded by applying a high pressure of 0.1 MPa to 10 MPa while heated in the air. The high vacuum bonding method is performed after cleaning the surfaces to be bonded with chemicals and pure water. -6 Pa to 10 -3 This is a method of bonding under a high vacuum atmosphere of about Pa. As a method for bonding the intermediate layer 30 and the semiconductor layer 20, surface activated bonding is preferred because it allows bonding at room temperature (for example, 5° C. to 30° C.) and allows easier bonding.

[0030] The temperature (bonding temperature) in the semiconductor layer forming step is, for example, preferably 0° C. to 400° C., more preferably 0° C. to 300° C., and even more preferably 5° C. to 200° C. (room temperature) from the viewpoint of suppressing deterioration of the intermediate layer 30 and the semiconductor layer 20.

[0031] According to the method for producing the nitride semiconductor laminated structure precursor of this embodiment, the nitride semiconductor laminated structure precursor 1 can be obtained by the deposition step and the semiconductor layer formation step, so that the production process can be simplified compared to conventional methods.

[0032] [Nitride semiconductor laminated structure] A nitride semiconductor stacked structure according to one embodiment of the present invention is a nitride semiconductor stacked structure in which a substrate made of carbon and a semiconductor layer made of a nitride semiconductor containing gallium nitride are bonded via an intermediate layer containing a metal M that forms a compound with at least one of the carbon and the gallium nitride, the intermediate layer containing at least one of a compound A of the metal M and the carbon and a compound B of the metal M and the gallium nitride, and containing at least one of the compound A formed between the substrate and the intermediate layer and the compound B formed between the intermediate layer and the semiconductor layer.

[0033] Hereinafter, a nitride semiconductor stacked structure according to one embodiment of the present invention will be described with reference to the drawings. Fig. 2 is a cross-sectional view that typically shows a nitride semiconductor stacked structure according to one embodiment of the present invention. 2, the nitride semiconductor stacked structure 100 of this embodiment has a substrate 110 made of carbon, a semiconductor layer 120 made of gallium nitride, and an intermediate layer 130 located between the substrate 110 and the semiconductor layer 120. That is, in the nitride semiconductor stacked structure 100 of this embodiment, the substrate 110 and the semiconductor layer 120 are bonded via the intermediate layer 130. The nitride semiconductor stacked structure 100 of this embodiment is obtained by bonding the substrate 10 and the semiconductor layer 20 of the nitride semiconductor stacked structure precursor 1 of the above-mentioned embodiment via the intermediate layer 30 containing the metal M.

[0034] The thickness T of the nitride semiconductor stack 100 100 is, for example, preferably 2 μm or more and 1000 μm or less, more preferably 5 μm or more and 700 μm or less, and further preferably 10 μm or more and 500 μm or less. 100 When the thickness T is equal to or greater than the lower limit, the physical strength of the nitride semiconductor stacked structure 100 can be further increased. 100 When is equal to or less than the above upper limit, the size of the nitride semiconductor stacked structure 100 can be made more compact. Thickness T 100 can be measured, for example, with a digital caliper. In this specification, "thickness T 100 " is the arithmetic mean value of the thickness at 10 randomly selected locations.

[0035] As the substrate 110, the same one as the substrate 10 described above is used.

[0036] The semiconductor layer 120 is a layer made of a nitride semiconductor containing gallium nitride (GaN).

[0037] The thickness T of the semiconductor layer 120 120 is, for example, preferably 0.5 μm or more and 50 μm or less, more preferably 1 μm or more and 20 μm or less, and further preferably 2 μm or more and 10 μm or less. 120When the thickness T is equal to or greater than the lower limit, the output of the semiconductor device using the nitride semiconductor stacked structure 100 can be further increased. 120 When is equal to or less than the upper limit, the thermal resistance of the nitride semiconductor constituting the semiconductor layer 120 is suppressed, thereby suppressing a temperature rise in the semiconductor device using the nitride semiconductor stacked structure 100 and improving the bond with the substrate 110. This further improves the heat dissipation and heat resistance of the semiconductor device. Thickness T 120 can be obtained, for example, by observing a cross section of the nitride semiconductor stacked structure 100 in the thickness direction with an electron microscope or the like. In this specification, "thickness T 120 " is the arithmetic mean value of the thickness at 10 randomly selected locations.

[0038] The intermediate layer 130 contains at least one of a compound A of the metal M and the carbon and a compound B of the metal M and the gallium nitride.

[0039] The metal M is the same as the metal M in the nitride semiconductor stacked structure precursor 1 of the above-described embodiment.

[0040] Between the substrate 110 and the intermediate layer 130, there exists the compound A formed by the reaction of the metal M contained in the intermediate layer 130 and the carbon contained in the substrate 110. In addition, between the intermediate layer 130 and the semiconductor layer 120, there exists the compound B formed by the reaction of the metal M contained in the intermediate layer 130 and the gallium nitride contained in the semiconductor layer 120. That is, the intermediate layer 130 contains the metal M, the compound A, and the compound B. In the intermediate layer 130, there is a bias in the concentrations of the metal M, the compound A, and the compound B. The presence of the compound A between the substrate 110 and the intermediate layer 130 indicates that the substrate 110 and the intermediate layer 130 are firmly bonded by a chemical bond between the carbon contained in the substrate 110 and the metal M contained in the intermediate layer 130. Furthermore, the presence of the compound B between the intermediate layer 130 and the semiconductor layer 120 indicates that the intermediate layer 130 and the semiconductor layer 120 are firmly bonded to each other by chemical bonding between the metal M contained in the intermediate layer 130 and the gallium nitride contained in the semiconductor layer 120. The nitride semiconductor stacked structure 100 of the present embodiment includes a case in which the compound A is formed between the substrate 110 and the intermediate layer 130 and the compound B is not present between the intermediate layer 130 and the semiconductor layer 120, and a case in which the compound B is formed between the intermediate layer 130 and the semiconductor layer 120 and the compound A is not present between the substrate 110 and the intermediate layer 130.

[0041] When the metal M is aluminum, the intermediate layer 130 may be made of aluminum gallium nitride (AlGaN), a compound of aluminum and gallium nitride, or aluminum tetracarbide (AlC), a compound of aluminum and carbon. 3 ) is preferably contained. When the intermediate layer 130 contains aluminum gallium nitride, the semiconductor layer 120 and the intermediate layer 130 are strongly bonded to each other. When the intermediate layer 130 contains tetraaluminum tricarbide, the substrate 110 and the intermediate layer 130 are strongly bonded to each other. Therefore, in order to strongly bond the substrate 110 and the semiconductor layer 120 via the intermediate layer 130, it is preferable that the intermediate layer 130 contains at least one of aluminum gallium nitride and tetraaluminum tricarbide (AlC 3 ) is more preferably included.

[0042] The intermediate layer 130 may have a single-layer structure or a multi-layer structure, so long as it contains at least one of the metal M and the compound A of carbon and the metal M and the compound B of gallium nitride. In the case of a single-layer structure, the intermediate layer 130 is composed only of a layer (hereinafter referred to as "layer α2") containing at least one of the metal M and the compound A of carbon and the metal M and the compound B of gallium nitride. In the case of a multi-layer structure, the intermediate layer 130 has the layer α2 and a layer β2 different from the layer α2, and the layer α2 may be present so as to be in contact with the substrate 110 and the semiconductor layer 120. For example, the intermediate layer 130 may be one in which the layer α2, the layer β2, and the layer α2 are laminated in this order. Examples of materials constituting the layer β2 include silicon (Si) and silicon carbide (SiC).

[0043] Thickness T of the intermediate layer 130 130 is, for example, preferably 1 nm or more and 100 nm or less, more preferably 2 nm or more and 50 nm or less, and further preferably 5 nm or more and 20 nm or less. 130 When the thickness T is equal to or greater than the lower limit, the influence of surface irregularities is mitigated and a strong bond is formed. 130 When it is equal to or less than the upper limit, the thermal resistance caused by the intermediate layer 130 can be made sufficiently small. Thickness T 130 can be obtained, for example, by observing a cross section of the nitride semiconductor stacked structure 100 in the thickness direction with an electron microscope or the like. In this specification, "thickness T 130 " is the arithmetic mean value of the thickness at 10 randomly selected locations.

[0044] According to the nitride semiconductor laminated structure 100 of this embodiment, the substrate 110 and the semiconductor layer 120 are bonded via the intermediate layer 130 containing the metal M, and the intermediate layer 130 contains at least one of the compound A of the metal M and carbon and the compound B of the metal M and gallium nitride, and the compound A is present at the boundary between the substrate 110 and the intermediate layer 130, and the compound B is present at the boundary between the intermediate layer 130 and the semiconductor layer 120. Therefore, even if one surface 110a of the substrate 110 is uneven, the substrate 110 and the semiconductor layer 120 can be firmly bonded via the intermediate layer 130. In addition, since the nitride semiconductor laminated structure 100 of this embodiment has the substrate 110 made of carbon, the heat generated by the semiconductor layer 120 can be efficiently released. Furthermore, the nitride semiconductor laminated structure 100 of this embodiment has no voids due to meltback at the boundary between the intermediate layer 130 and the semiconductor layer 120, and has excellent heat resistance.

[0045] [Method of manufacturing nitride semiconductor laminate structure] A method for producing a nitride semiconductor laminate structure according to one embodiment of the present invention includes a heat treatment step of obtaining a nitride semiconductor laminate structure precursor by the method for producing a nitride semiconductor laminate structure precursor according to the above-mentioned embodiment, and subjecting the nitride semiconductor laminate structure precursor to a heat treatment at 500°C or higher.

[0046] Hereinafter, a method for producing a nitride semiconductor stacked structure according to one embodiment of the present invention will be described with reference to FIGS.

[0047] The heat treatment step is a step of subjecting the nitride semiconductor laminated structure precursor 1 to a heat treatment at 500° C. or higher. The heat treatment temperature when carrying out the heat treatment is preferably 550°C or more, more preferably 600°C or more. When the heat treatment temperature is equal to or higher than the above lower limit, the carbon contained in the substrate 10 and the metal M contained in the intermediate layer 30 can be reacted to generate a compound A, and the gallium nitride contained in the semiconductor layer 20 and the metal M contained in the intermediate layer 30 can be reacted to generate a compound B. In addition, the semiconductor layer 120 can be sufficiently given an element structure. The upper limit of the heat treatment temperature is not particularly limited, but is set to, for example, 1100°C or less from the viewpoint of suppressing deterioration of the semiconductor layer 120. Here, the element structure refers to a structure having, from the side closer to the intermediate layer 130, a buffer layer, a channel layer, a barrier layer, and a contact layer.

[0048] In the method for producing the nitride semiconductor laminated structure of this embodiment, the heat treatment time when the nitride semiconductor laminated structure precursor 1 is heat-treated is preferably 1 minute or more, more preferably 2 minutes or more, and even more preferably 5 minutes or more. When the heat treatment time is equal to or more than the above lower limit, the carbon contained in the substrate 10 and the metal M contained in the intermediate layer 30 can react with each other to produce compound A, and the gallium nitride contained in the semiconductor layer 20 and the metal M contained in the intermediate layer 30 can react with each other to produce compound B.

[0049] By subjecting the nitride semiconductor laminated structure precursor 1 to a heat treatment, at least one of carbon and gallium nitride contained in the semiconductor layer 20 of the nitride semiconductor laminated structure precursor 1 reacts with the metal M contained in the intermediate layer 30 to form a compound layer containing at least one of a compound A of the metal M and carbon and a compound B of the metal M and gallium nitride. Accordingly, crystal growth of a nitride semiconductor containing gallium nitride is promoted in the semiconductor layer 20.

[0050] According to the method for producing the nitride semiconductor laminated structure of this embodiment, the nitride semiconductor laminated structure 100 can be obtained by a heat treatment step of subjecting the nitride semiconductor laminated structure precursor 1 to a heat treatment at 500° C. or higher. This heat treatment may also serve as heating of the nitride semiconductor laminated structure associated with a step of producing a semiconductor element on the nitride semiconductor laminated structure, or a step of crystal growing (regrowing) a semiconductor layer made of a nitride semiconductor on the nitride semiconductor laminated structure by, for example, a vapor phase growth method. Since heating of the nitride semiconductor laminated structure is essential in the step of producing these semiconductor elements and the step of crystal growing a semiconductor layer made of a nitride semiconductor by a vapor phase growth method, the production process can be simplified compared to the conventional method by performing the heat treatment in this embodiment during the production of the semiconductor element or during the crystal growth of the semiconductor layer made of a nitride semiconductor. In addition, a nitride semiconductor laminated structure 100 having sufficient heat resistance can be obtained without meltback occurring at the boundary between the intermediate layer 130 and the semiconductor layer 120 of the obtained nitride semiconductor laminated structure 100.

[0051] [Semiconductor Devices] A semiconductor device according to one embodiment of the present invention has the above-mentioned nitride semiconductor stacked structure.

[0052] Hereinafter, a semiconductor device according to an embodiment of the present invention will be described with reference to the drawings. Fig. 3 is a cross-sectional view showing a schematic diagram of a semiconductor device according to an embodiment of the present invention. In Fig. 3, the same components as those in the nitride semiconductor stack structure shown in Fig. 2 are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 3, a semiconductor device 200 of this embodiment has a nitride semiconductor stacked structure 100.

[0053] In the semiconductor device 200, a portion of the semiconductor layer 120 and the intermediate layer 130 in the nitride semiconductor stack 100 has been removed. In the semiconductor device 200, of the semiconductor layer 120 and intermediate layer 130 remaining on the substrate 110, a gate electrode 141, a source electrode 142, and a drain electrode 143 may be formed as electrodes 140 on a surface (one side) 120a of the semiconductor layer 120.

[0054] Known materials can be used as the material for forming the gate electrode 141. Examples of the material for forming the gate electrode 141 include nickel, gold, and palladium. Known materials can be used as the material forming the source electrode 142. Examples of materials forming the source electrode 142 include titanium, aluminum, nickel, gold, and the like, and multi-layer structures thereof. Known materials can be used as the material forming the drain electrode 143. Examples of the material forming the drain electrode 143 include titanium, aluminum, nickel, gold, and the like, and a multi-layer structure thereof.

[0055] The thickness of the gate electrode 141 is, for example, preferably 0.05 μm to 5 μm, more preferably 0.1 μm to 2 μm, and even more preferably 0.2 μm to 1 μm. When the thickness of the gate electrode 141 is equal to or greater than the lower limit, the output of the semiconductor device 200 can be further increased. When the thickness of the gate electrode 141 is equal to or less than the upper limit, the gate electrode 141 can be miniaturized, and the operating frequency of the semiconductor device 200 can be improved. In addition, when the thickness of the gate electrode 141 is equal to or less than the upper limit, the production efficiency of the semiconductor device 200 can be further increased. The thickness of the source electrode 142 is similar to the thickness of the gate electrode 141 . The thickness of the drain electrode 143 is similar to the thickness of the gate electrode 141 .

[0056] The pattern shapes of the gate electrode 141, the source electrode 142, and the drain electrode 143 are not particularly limited, and can be appropriately determined depending on the application of the semiconductor device 200, etc.

[0057] In the nitride semiconductor stacked structure 100, the shape of the pattern of the semiconductor layer 120 and the intermediate layer 130 to be removed is not particularly limited, and can be appropriately determined depending on the application of the semiconductor device 200, etc.

[0058] The semiconductor device 200 of this embodiment includes the above-mentioned nitride semiconductor stacked structure 100 and the electrode 140 located on the surface 120a of the semiconductor layer 120, and since the nitride semiconductor stacked structure 100 has excellent heat dissipation properties, it is possible to suppress an increase in temperature of the semiconductor device 200 even when the semiconductor device 200 is applied to high-power applications. In addition, since the nitride semiconductor stacked structure 100 has excellent heat dissipation properties, it is possible to suppress deterioration of the semiconductor device 200 due to heat generated in the electrode 140 and the semiconductor layer 120.

[0059] [Method of manufacturing semiconductor device] A method for manufacturing a semiconductor device according to one embodiment of the present invention includes a patterning step of processing the semiconductor layers and intermediate layers of the nitride semiconductor stacked structure obtained by the above-mentioned method for manufacturing the nitride semiconductor stacked structure into a desired shape.

[0060] Hereinafter, a method for manufacturing a semiconductor device according to one embodiment of the present invention will be described with reference to FIG.

[0061] The patterning step is a step of processing the nitride semiconductor stacked structure 100 by lithography to process the semiconductor layer 120 and the intermediate layer 130 on the substrate 110 into a desired shape.

[0062] The method for manufacturing a semiconductor device according to this embodiment may include an electrode formation step of forming an electrode on the surface 120 a of the semiconductor layer 120 of the nitride semiconductor stack 100 . The electrode formation step is a step of laminating a gate electrode 141, a source electrode 142, and a drain electrode 143 on a surface 120a of the semiconductor layer 120 that has been processed into a desired shape. The gate electrode 141, the source electrode 142, and the drain electrode 143 may be made of a known metal such as nickel, gold, titanium, aluminum, palladium, or a multi-layer structure thereof.

[0063] The gate electrode 141, the source electrode 142, and the drain electrode 143 are obtained by forming a metal laminate film by film formation using vacuum deposition or the like. When forming the source electrode 142 and the drain electrode 143, a heat treatment is performed after the formation of the metal laminate film to react with the gallium nitride contained in the semiconductor layer 120. The heating temperature for this purpose is, for example, preferably 650° C. or higher, more preferably 700° C. or higher, and even more preferably 800° C. or higher.

[0064] Through the above steps, the intermediate layer 130 located on one surface 110a of the substrate 110 is bonded to the semiconductor layer 120, and a semiconductor device (semiconductor element) 200 is obtained in which a gate electrode 141, a source electrode 142, and a drain electrode 143 are formed on the surface 120a of the semiconductor layer 120. EXAMPLES

[0065] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0066] [Example] A rectangular substrate with a length of 4 mm, width of 4 mm, and thickness of 500 μm was prepared as the diamond substrate. One side of this diamond substrate was analyzed using an atomic force microscope (AFM), and the arithmetic mean roughness Ra was 0.77 nm. Aluminum was deposited on one side of this diamond substrate by sputtering to form an aluminum layer (intermediate layer) with a thickness of 13 nm, and a first laminate was obtained. Next, a silicon substrate with a diameter of 4 inches (101.6 mm) and a thickness of 500 μm was prepared as a crystal growth substrate, and gallium nitride was grown as a nitride on one side of the silicon substrate by MOCVD to form a semiconductor layer with a thickness of 1 μm, thereby obtaining a second laminate. Next, the semiconductor layer of the second laminate was cut into a rectangle having a length of 10 mm and a width of 12 mm. A rectangular silicon substrate having a length of 20 mm, a width of 20 mm and a thickness of 500 μm was attached to the semiconductor layer as a support substrate using wax to obtain a third laminate. Next, the crystal growth substrate of the third laminate was removed by etching with a hydrofluoric acid-nitric acid mixture, and the back surface of the semiconductor layer was polished by CMP to obtain a fourth laminate.

[0067] Next, the semiconductor layer of the fourth laminate and the aluminum layer of the first laminate were bonded by the SAB method to obtain a fifth laminate. The support substrate of the obtained fifth stack was removed by etching with a mixed solution of hydrofluoric acid and nitric acid to obtain a sixth stack (nitride semiconductor stack structure). The cross section of the sixth laminate in the thickness direction was observed with a transmission electron microscope (TEM), and the results are shown in FIG. As shown in Figure 4, it was confirmed that a 13 nm-thick aluminum layer (intermediate layer) was formed between the diamond substrate and the semiconductor layer (gallium nitride, GaN).

[0068] In addition, a cross section of the sixth laminate in the thickness direction was analyzed by energy dispersive X-ray spectroscopy (EDX), and the results are shown in FIG. As shown in FIG. 5, it was confirmed that an aluminum layer was formed between the diamond substrate and the semiconductor layer.

[0069] Next, the nitride semiconductor laminated structure was subjected to a heat treatment at 600° C. for 5 minutes. The cross section of the nitride semiconductor laminated structure in the thickness direction after the heat treatment was observed by a TEM. The results are shown in FIG. As shown in Figure 6, the contrast of the intermediate layer changed due to the heat treatment. Furthermore, microcrystals were observed in the intermediate layer in Figure 6, which were not observed in the intermediate layer in Figure 4. From these, it was found that compounds were formed in the intermediate layer by the heat treatment. Furthermore, as shown in Figure 6, no meltback occurred at the interface between the intermediate layer and the semiconductor layer, and it was confirmed that the nitride semiconductor stacked structure had sufficient heat resistance. The aluminum in the intermediate layer combines with the carbon in the diamond substrate and the gallium nitride in the semiconductor layer, forming an intermediate layer of aluminum gallium nitride (AlGaN) and tetraaluminum tricarbide (AlC3 ) is believed to be included. It is also believed that there is a region with a high concentration of tetraaluminum tricarbide at the boundary between the diamond substrate and the intermediate layer. It is also believed that there is a region with a high concentration of aluminum gallium nitride at the boundary between the intermediate layer and the semiconductor layer.

[0070] In addition, a cross section in the thickness direction of the nitride semiconductor stacked structure after heat treatment at 600° C. was analyzed by EDX. The results are shown in FIG. As shown in Figure 7, the distribution of aluminum contained in the intermediate layer is wider than that in Figure 5, and carbon, gallium, and nitrogen have diffused into the aluminum, and the overlap between the distribution of aluminum and the distribution of carbon, gallium, and nitrogen has become larger than that in Figure 5. This indicates that the compound consisting of microcrystals formed in the intermediate layer by heat treatment consists of aluminum, carbon, gallium, and nitrogen, that is, it combines with the carbon contained in the diamond substrate and the gallium nitride contained in the semiconductor layer, and the intermediate layer becomes aluminum gallium nitride (AlGaN) and tetraaluminum tricarbide (AlC 3 ) was confirmed to be included.

[0071] Next, the nitride semiconductor laminated structure was subjected to a heat treatment at 1000° C. for 5 minutes. The cross section of the nitride semiconductor laminated structure in the thickness direction after the heat treatment was observed by a TEM. The results are shown in FIG. As shown in Figure 8, in the intermediate layer after the 1000°C heat treatment, regions in which atoms are periodically arranged (microcrystals) were observed, which were not observed in the intermediate layer in Figure 4, as in Figure 6. The aluminum contained in the intermediate layer is bonded to the carbon contained in the diamond substrate and the gallium nitride contained in the semiconductor layer, and the intermediate layer is composed of aluminum gallium nitride (AlGaN) and tetraaluminum tricarbide (AlC 3 ) is thought to be contained in the intermediate layer. In addition, the intermediate layer is thicker than that in Figure 6. It is thought that the high-temperature heat treatment promotes the formation of aluminum gallium nitride and tetraaluminum tricarbide, and thus improves the bonding between the intermediate layer and the diamond substrate and the semiconductor layer. Moreover, as shown in FIG. 8, it was confirmed that no meltback occurred at the interface between the intermediate layer and the semiconductor layer, and the nitride semiconductor stacked structure had sufficient heat resistance.

[0072] In addition, a cross section of the semiconductor laminated structure in the thickness direction after heat treatment at 1000° C. was analyzed by EDX. The results are shown in FIG. As shown in Figure 9, the distribution of aluminum is wider after heat treatment at 1000°C than after heat treatment at 600°C, and the overlap between the distributions of aluminum and carbon, gallium, and nitrogen also becomes larger. These results are consistent with the increase in thickness of the intermediate layer and the promotion of compound formation due to heat treatment at 1000°C shown in Figure 8. Also, as in Figure 7, the compounds consisting of microcrystals formed in the intermediate layer by heat treatment consist of aluminum, carbon, gallium, and nitrogen. In other words, the aluminum contained in the intermediate layer combines with the carbon contained in the diamond substrate and the gallium nitride contained in the semiconductor layer, and the intermediate layer becomes aluminum gallium nitride (AlGaN) and tetraaluminum tricarbide (AlC 3 It was also confirmed that the formation of aluminum gallium nitride and tetraaluminum tricarbide was promoted, and the bonding between the intermediate layer and the diamond substrate and the semiconductor layer was improved. [Explanation of symbols]

[0073] 1. Nitride semiconductor stack precursor 10 Substrate 20 Semiconductor layer 30 Middle Class 100 Nitride semiconductor laminate structure 110 Substrate 120 Semiconductor layer 130 Middle Class 140 electrodes 141 Gate electrode 142 Source Electrode 143 Drain electrode 200 Semiconductor device

Claims

1. A semiconductor device comprising: a substrate made of carbon; a semiconductor layer made of a nitride semiconductor containing gallium nitride; and an intermediate layer located between the substrate and the semiconductor layer; A nitride semiconductor stacked structure precursor in which the substrate and the semiconductor layer are in contact with the intermediate layer, The intermediate layer comprises a metal M that forms a compound with at least one of the carbon and the gallium nitride.

2. 2. The nitride semiconductor stacked structure precursor according to claim 1, wherein the metal M is aluminum, manganese, magnesium or lithium, or an alloy containing the aluminum, the manganese, the magnesium or the lithium.

3. A nitride semiconductor stacked structure in which a substrate made of carbon and a semiconductor layer made of a nitride semiconductor containing gallium nitride are bonded to each other via an intermediate layer containing a metal M that forms a compound with at least one of the carbon and the gallium nitride, the intermediate layer includes at least one of a compound A of the metal M and the carbon and a compound B of the metal M and the gallium nitride, A nitride semiconductor stacked structure comprising at least one of the compound A formed between the substrate and the intermediate layer, and the compound B formed between the intermediate layer and the semiconductor layer.

4. 4. The nitride semiconductor stacked structure according to claim 3, wherein the metal M is aluminum, manganese, magnesium or lithium, or an alloy containing the aluminum, the manganese, the magnesium or the lithium.

5. 5. The nitride semiconductor stacked structure according to claim 4, wherein said compound A is tetraaluminum tricarbide, and said compound B is aluminum gallium nitride.

6. A semiconductor device comprising the nitride semiconductor stacked structure according to any one of claims 3 to 5.

7. a deposition step of depositing a metal M that forms a compound with at least one of the carbon and gallium nitride on at least a portion of one surface of a substrate made of carbon to form an intermediate layer; and forming a semiconductor layer on a surface of the intermediate layer, the semiconductor layer being made of a nitride semiconductor containing gallium nitride.

8. A method for producing a nitride semiconductor laminate structure, comprising: obtaining a nitride semiconductor laminate structure precursor by the method for producing a nitride semiconductor laminate structure precursor according to claim 7; and subjecting the nitride semiconductor laminate structure precursor to a heat treatment at 500° C. or higher.

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