Laminated substrate

Abstract

The present invention provides, at low cost, a laminated substrate which is to be used in a device and is equipped with a heat sink material which exhibits excellent thermal conductivity. The laminated substrate is equipped with a three-layer structure comprising: a device substrate comprising at least one type of single crystal material selected from the group consisting of Si, SiC, GaN, AlN, BN, Ga2O3, Cr2O3, LiTaO3, and LiNbO3; a metal layer on the device substrate; and a diamond layer on the metal layer.

Description

Multilayer substrate

[0001] The present invention relates to a laminated substrate.

[0002] Diamond is a material with extremely high thermal conductivity (approximately 22 W / cm K), and is expected to be used as a heat sink for semiconductor devices and other devices. Applications such as heat sinks require diamond films or substrates of a certain size.

[0003] Non-Patent Document 1 (Makoto Kasu, Ryota Takaya, and Seong-Woo Kim, Diamond & Related Materials 126 (2022) 109086) discloses a method for producing a diamond substrate. A 1 μm thick Ir buffer layer is then formed on a sapphire substrate by sputtering, followed by forming diamond nuclei on the Ir buffer layer by a bias-enhanced nucleation (BEN) process using a DC plasma CVD apparatus. A diamond layer is then grown on the BEN-treated Ir buffer layer by microwave plasma CVD, thereby producing a sapphire / Ir buffer layer / diamond layer stack. This document also describes that a microneedle process is essential to obtain a free-standing diamond layer from the stack without breakage.

[0004] Makoto Kasu, Ryota Takaya, and Seong-Woo Kim, "Growth of high-quality inch-diameter heteroepitaxial diamond layers on sapphire substrates in comparison to MgO substrates", Diamond & Related Materials 126 (2022) 109086

[0005] As described above, there are known methods for manufacturing freestanding diamond substrates or films (hereinafter referred to as diamond substrates). When a freestanding diamond substrate is used as a heat sink or the like for a semiconductor device or other device, it is possible to directly bond the diamond substrate to the device. However, this requires mirror-finishing both the diamond substrate and the device, which increases costs.

[0006] The present inventors have now discovered that by forming a diamond layer on a predetermined device substrate via a metal layer, it is possible to provide a laminated device substrate equipped with a heat sink material having excellent thermal conductivity at low cost.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a low-cost laminate substrate for devices that includes a heat sink material with excellent thermal conductivity.

[0008] According to the present invention, the following aspects are provided: [Aspect 1] Si, SiC, GaN, AlN, BN, Ga ２ O ３ , Cr ２ O ３ , LiTaO ３ and LiNbO ３ A laminated substrate having a three-layer structure composed of a device substrate made of at least one single crystal material selected from the group consisting of: a metal layer on the device substrate; and a diamond layer on the metal layer. [Aspect 2] The laminated substrate according to Aspect 1, wherein the device substrate is made of at least one single crystal material selected from the group consisting of Si and SiC. [Aspect 3] The laminated substrate according to Aspect 1 or 2, wherein the device substrate is made of at least one single crystal material selected from the group consisting of GaN, AlN, and BN. [Aspect 4] The device substrate is made of Ga ２ O ３ , Cr ２ O ３ , LiTaO ３ and LiNbO ３The laminated substrate according to any one of Aspects 1 to 3, which is made of at least one single crystal material selected from the group consisting of: [Aspect 5] The laminated substrate according to any one of Aspects 1 to 4, wherein the metal layer is made of a metal or alloy containing at least one selected from the group consisting of Ir, Rh, Pt, Ru, and Au. [Aspect 6] The laminated substrate according to any one of Aspects 1 to 4, wherein the metal layer is made of a metal or alloy containing Ni, Cu, Fe, and Co. [Aspect 7] The laminated substrate according to any one of Aspects 1 to 4, wherein the metal layer is made of a metal or alloy containing Be. [Aspect 8] The laminated substrate according to any one of Aspects 1 to 4, wherein the metal layer is made of a metal or alloy containing Ir. [Aspect 9] The laminated substrate according to any one of Aspects 1 to 8, wherein the diamond layer is made of a diamond single crystal. [Aspect 10] The laminated substrate according to any one of Aspects 1 to 9, wherein the diamond layer is made of a biaxially textured layer of diamond. [Aspect 11] The laminated substrate according to any one of Aspects 1 to 10, wherein the diamond layer is made of a uniaxially textured layer of diamond. [Aspect 12] The laminated substrate according to any one of Aspects 1 to 11, wherein the thickness of the device substrate is 1 μm to 30 μm. [Aspect 13] The laminated substrate according to any one of Aspects 1 to 12, wherein the thickness of the metal layer is 50 nm to 100 μm. [Aspect 14] The laminated substrate according to any one of Aspects 1 to 13, wherein the thickness of the diamond layer is 100 μm to 2.0 mm. [Aspect 15] The laminated substrate according to any one of Aspects 1 to 14, wherein the thickness Ts of the device substrate, the thickness Tm of the metal layer, and the thickness Td of the diamond layer satisfy the relationships Td≧Ts×10 and Td≧Tm×10. [Aspect 16] The laminated substrate according to any one of Aspects 1 to 14, wherein the thickness Ts of the device substrate, the thickness Tm of the metal layer, and the thickness Td of the diamond layer satisfy the relationships Ts≧Tm×10 and Ts≧Td×10. [Aspect 17] The laminated substrate according to any one of aspects 1 to 14, wherein the thickness Ts of the device substrate, the thickness Tm of the metal layer, and the thickness Td of the diamond layer satisfy the relationships Tm ≧ Ts × 10 and Tm ≧ Td × 10.[Aspect 18] The laminated substrate according to any one of Aspects 1 to 14, wherein a thickness Ts of the device substrate, a thickness Tm of the metal layer, and a thickness Td of the diamond layer satisfy the relationships Ts ≥ Tm × 10 and Td ≥ Tm × 10. [Aspect 19] The laminated substrate according to any one of Aspects 1 to 4, 7, and 9 to 18, wherein the metal layer is a film formed by sputtering and composed of a metal or alloy containing Be.

[0009] Fig. 1 is a schematic cross-sectional view showing a laminated substrate according to one embodiment of the present invention; Fig. 2 is a schematic cross-sectional view showing a laminated substrate according to a preferred embodiment of the present invention; Fig. 3 is a schematic cross-sectional view showing a laminated substrate according to another preferred embodiment of the present invention; Fig. 4 is a schematic cross-sectional view showing a laminated substrate according to yet another preferred embodiment of the present invention; Fig. 5 is a schematic cross-sectional view showing a laminated substrate according to yet another preferred embodiment of the present invention.

[0010] 1 shows a laminated substrate 10 according to one embodiment of the present invention. The laminated substrate 10 has a three-layer structure consisting of a device substrate 12, a metal layer 14, and a diamond layer 16. The device substrate 12 is made of a material selected from the group consisting of Si, SiC, GaN, AlN, BN, and Ga. ２ O ３ , Cr ２ O ３ , LiTaO ３ and LiNbO ３ The device substrate 12 is made of at least one single crystal material selected from the group consisting of: A metal layer 14 is provided on the device substrate 12; and a diamond layer 16 is provided on the metal layer 14. By forming the diamond layer 16 on the predetermined device substrate 12 via the metal layer 14 in this way, a laminated device substrate 10 equipped with a heat sink material having excellent thermal conductivity can be provided at low cost.

[0011] As mentioned above, when a free-standing diamond substrate is used as a heat sink or the like in a device such as a semiconductor device, it is possible to directly bond the diamond substrate and the device. However, both the diamond substrate and the device must be mirror-finished, which increases costs. In this regard, according to the present invention, there is no need to prepare a free-standing diamond substrate, and therefore there is no need to directly bond the diamond substrate and the device. Therefore, a laminate substrate 10 for a device equipped with a heat sink material with excellent thermal conductivity can be provided at low cost. Furthermore, when a directly bonded diamond single crystal substrate and a device substrate are heated to form a functional layer, they may warp significantly, resulting in the functional layer not being formed or (even if it can be formed) the quality of the functional layer being reduced. In this regard, the laminate of the present invention is expected to reduce warpage of the laminate substrate when heated.

[0012] The device substrate 12 is made of Si, SiC, GaN, AlN, BN, Ga ２ O ３ , Cr ２ O ３ , LiTaO ３ and LiNbO ３ According to a preferred embodiment of the present invention, the single crystal material constituting the device substrate 12 is at least one selected from the group consisting of Si and SiC. According to another preferred embodiment of the present invention, the single crystal material constituting the device substrate 12 is at least one selected from the group consisting of GaN, AlN, and BN. According to yet another preferred embodiment of the present invention, the single crystal material constituting the device substrate 12 is Ga ２ O ３ , Cr ２ O ３ , LiTaO ３ and LiNbO ３ At least one selected from the group consisting of:

[0013] The thickness of the device substrate 12 is not particularly limited, but is preferably 1 μm to 2.0 mm. The device substrate 12 may be in the form of a thin film as a functional layer, in which case the thickness is more preferably 1 μm to 30 μm, and even more preferably 1 μm to 10 μm. On the other hand, when the device substrate 12 is used as a support substrate for a three-layer structure, the thickness is preferably 100 μm to 2000 μm, more preferably 300 μm to 1300 μm, and particularly preferably 350 μm to 1000 μm.

[0014] The device substrate 12 may be a commercially available single crystal substrate, and the manufacturing method thereof is not particularly limited. Furthermore, the device substrate 12 may have a functional layer formed thereon, or may be a substrate 12 alone before the functional layer is formed. Examples of functional layers include a p-type layer, an n-type layer, a drift layer, a buffer layer, etc. Furthermore, a device may be mounted on the device substrate 12 or the functional layer. Therefore, the laminated substrate 10 according to the present invention may be a substrate on which a device is mounted, or a substrate before a device is mounted. That is, the laminated substrate 10 may consist of only a three-layer structure consisting of the device substrate 12, the metal layer 14, and the diamond layer 16, or may further include a functional layer and / or device formed on the device substrate 12 in addition to this three-layer structure. Examples of devices include semiconductor devices, piezoelectric elements, etc., with semiconductor devices being preferred.

[0015] The metal layer 14 is preferably made of a metal or alloy including, but not limited to, Ir, Rh, Pt, Ru, Au, Ni, Cu, Fe, Co, and Be. According to a preferred embodiment of the present invention, the metal or alloy constituting the metal layer 14 includes at least one selected from the group consisting of Ir, Rh, Pt, Ru, and Au, such as Ir. According to another preferred embodiment of the present invention, the metal or alloy constituting the metal layer 14 includes at least one selected from the group consisting of Ni, Cu, Fe, Co, and Be, such as Be.

[0016] The thickness of the metal layer 14 is not particularly limited, but is preferably 50 nm to 1 mm, more preferably 50 nm to 100 μm, and even more preferably 100 nm to 100 μm.

[0017] The metal layer 14 may be formed on the device substrate 12 by any known film formation method, such as chemical vapor deposition (CVD) or physical vapor deposition (PVD), and the manufacturing method is not particularly limited. Examples of the method for forming the metal layer 14 include sputtering and atomic layer deposition (ALD).

[0018] The diamond layer 16 is made of diamond. This diamond may be either single crystal or polycrystalline, but is preferably made of a biaxially oriented or uniaxially oriented diamond layer. When the diamond layer 16 is made of a biaxially oriented or uniaxially oriented layer, warping of the laminated substrate 10 having a three-layer structure is more easily reduced. In other words, the diamond layer 16 may be made of a single crystal diamond, a biaxially oriented diamond layer, or a uniaxially oriented diamond layer.

[0019] The biaxially oriented layer of diamond is preferably oriented in the c-axis direction and the a-axis direction.As long as the biaxially oriented layer is oriented in the c-axis and the a-axis directions, it may be a diamond single crystal, a diamond polycrystal, or a mosaic crystal.A mosaic crystal is a collection of crystals that do not have clear grain boundaries, but whose orientation direction is slightly different in one or both of the c-axis and the a-axis.The evaluation method of orientation is not particularly limited, and known analytical methods such as EBSD (Electron Backscatter Diffraction Patterns) method and X-ray pole figure can be used.For example, when using the EBSD method, the inverse pole figure mapping of the surface (plate surface) of the biaxially oriented layer or the cross section perpendicular to the plate surface is measured. In the obtained inverse pole figure mapping, when the following four conditions are met, it can be defined as being oriented in two axes, the approximately normal direction and the approximately plate plane direction: (A) being oriented in a specific direction (first axis) approximately normal to the plate surface; (B) being oriented in a specific direction (second axis) approximately in the plate plane direction perpendicular to the first axis; (C) the tilt angle from the first axis is distributed within ±10°; and (D) the tilt angle from the second axis is distributed within ±10°. In other words, when the above four conditions are met, it is determined to be oriented in two axes, the c-axis and the a-axis. For example, when the approximately normal direction to the plate surface is oriented to the c-axis, it is sufficient that the approximately in-plane direction is oriented in a specific direction (e.g., the a-axis) perpendicular to the c-axis. The biaxially oriented layer may be oriented in two axes, the approximately normal direction and the approximately in-plane direction, but it is preferable that the approximately normal direction is oriented to the c-axis. The smaller the tilt angle distribution in the approximately normal direction and / or the approximately in-plane direction, the smaller the mosaic property of the biaxially oriented layer, and the closer it is to zero, the closer it is to single crystal. Therefore, from the viewpoint of the crystallinity of the biaxially oriented layer, it is preferable that the tilt angle distribution is small in both the approximately normal direction and the approximately in-plane direction, for example, ±5° or less is more preferable, and ±3° or less is even more preferable.

[0020] The uniaxially oriented layer of diamond is preferably oriented in the c-axis direction or the a-axis direction.The evaluation method of orientation is not particularly limited, but can be used known analytical methods such as EBSD (Electron Backscatter Diffraction Patterns) method or X-ray pole figure.For example, when using EBSD method, measure the inverse pole figure mapping of the surface (plate surface) of the uniaxially oriented layer or the cross section perpendicular to the plate surface to determine whether it is oriented.

[0021] The thickness of the diamond layer 16 is not particularly limited, but is preferably 1 μm or more, more preferably 20 μm or more, and even more preferably 100 μm to 2.0 mm.

[0022] The diamond layer 16 may be formed on the metal layer 14 by a known film formation method such as chemical vapor deposition (CVD) or physical vapor deposition (PVD), and the manufacturing method is not particularly limited. For example, as disclosed in Non-Patent Document 1, diamond nuclei may be formed on the metal layer 14 (e.g., an Ir layer) by a bias-enhanced nucleation (BEN) process using a DC plasma CVD apparatus, and the diamond layer 16 may be grown on the BEN-treated metal layer 14 by microwave plasma CVD. For example, the growth of the diamond layer 16 by microwave plasma CVD may be performed using H ２ Diluted CH ４ as a carbon source gas at a substrate temperature of 1000°C.

[0023] In the laminated substrate 10, the function of supporting the three-layer structure (function as a support matrix) may be provided to any of the device substrate 12, the metal layer 14, and the diamond layer 16. In other words, the thickest layer of the three-layer structure may be any of the device substrate 12, the metal layer 14, and the diamond layer 16.

[0024] According to a preferred embodiment of the present invention, the diamond layer 16 can be made to have the function of supporting the three-layer structure. In this case, as shown in Figure 2, the thickness Ts of the device substrate 12, the thickness Tm of the metal 14 layer, and the thickness Td of the diamond layer 16 preferably satisfy the relationships Td ≥ Ts x 10 and Td ≥ Tm x 10, more preferably Td ≥ Ts x 20 and Td ≥ Tm x 20. There are no particular restrictions on the upper limit of Td, but it is preferable that the relationships Td ≤ Ts x 1000 and Td ≤ Tm x 1000 are satisfied, more preferably Td ≤ Ts x 500 and Td ≤ Tm x 500.

[0025] According to another preferred embodiment of the present invention, the device substrate 12 can be provided with the function of supporting the three-layer structure. In this case, as shown in Figure 3, the thickness Ts of the device substrate 12, the thickness Tm of the metal layer 14, and the thickness Td of the diamond layer 16 preferably satisfy the relationships Ts ≥ Tm x 10 and Ts ≥ Td x 10, more preferably Ts ≥ Tm x 20 and Ts ≥ Td x 20. There are no particular restrictions on the upper limit of Ts, but it is preferable that the relationships Ts ≤ Tm x 1000 and Ts ≤ Td x 1000 are satisfied, more preferably Ts ≤ Tm x 500 and Ts ≤ Td x 500.

[0026] According to yet another preferred embodiment of the present invention, the metal layer 14 can be made to have the function of supporting the three-layer structure. In this case, as shown in Figure 4, the thickness Ts of the device substrate 12, the thickness Tm of the metal layer 14, and the thickness Td of the diamond layer 16 preferably satisfy the relationships Tm ≥ Ts x 10 and Tm ≥ Td x 10, more preferably Tm ≥ Ts x 20 and Tm ≥ Td x 20. There are no particular restrictions on the upper limit of Td, but it is preferable that the relationships Tm ≤ Ts x 1000 and Tm ≤ Td x 1000 are satisfied, more preferably Tm ≤ Ts x 500 and Tm ≤ Td x 500.

[0027] According to yet another preferred embodiment of the present invention, the function of supporting the three-layer structure may be provided to both the device substrate 12 and the diamond layer 16. In this case, as shown in Figure 5, the thickness Ts of the device substrate 12, the thickness Tm of the metal layer 14, and the thickness Td of the diamond layer 16 preferably satisfy the relationships Ts ≥ Tm x 10 and Td ≥ Tm x 10, more preferably Ts ≥ Tm x 20 and Td ≥ Tm x 20. There are no particular restrictions on the upper limits of Ts and Td, but they preferably satisfy the relationships Ts ≤ Tm x 1000 and Td ≤ Tm x 1000, more preferably Ts ≤ Tm x 500 and Td ≤ Tm x 500.

[0028] The size of the laminated substrate 10 is not particularly limited, but when the shape of the laminated substrate 10 in a planar view is circular, the diameter is preferably 2 cm or more, more preferably 5 cm or more, and even more preferably 10 cm or more. The upper limit of the diameter is not particularly limited, but is typically 300 cm or less. When the shape of the laminated substrate 10 in a planar view is rectangular, the dimensions are preferably 2 cm or more × 2 cm or more, more preferably 5 cm or more × 5 cm or more, and even more preferably 10 cm or more × 10 cm or more. In this case, the upper limit of each side is not particularly limited, but is typically 300 cm or less × 300 cm or less.

[0029] Example 1: A double-side polished GaN single crystal substrate (diameter 50.8 mm, thickness 0.45 mm) with a c-plane orientation and an off-angle of 0.2° was prepared as a device substrate. An iridium (Ir) film was grown on the N-face side of this device substrate. The film was formed by RF magnetron sputtering using metallic Ir as the target under an Ar gas pressure of 6×10. －２ Torr and substrate temperature: The process was continued under the conditions of 800° C. until the Ir film thickness reached 1.0 μm.

[0030] The bias treatment for forming diamond nuclei on the surface of the Ir film of the obtained substrate was carried out as follows. First, the substrate was set on the negative voltage application electrode (cathode) of the bias treatment device, and vacuum evacuation was carried out. Next, the substrate was heated to 800°C, and then 3 vol. % hydrogen diluted methane gas was introduced, and the pressure was set to 130 Torr, and bias treatment was carried out. That is, a DC voltage was applied between the two electrodes, and a predetermined direct current was passed.

[0031] Finally, single-crystal diamond was heteroepitaxially grown on the bias-treated surface by microwave plasma CVD at 1000° C. for 30 hours.

[0032] After growth was complete, the product removed from the CVD apparatus was a crack-free diamond / Ir / GaN laminate substrate. Cross-sectional observation revealed that the diamond film was approximately 105 μm thick. EBSD measurements also revealed that the diamond film was a biaxially oriented film, with both the c-axis and a-axis oriented.

[0033] Example 2: A double-side polished AlN single crystal substrate (diameter 50.8 mm, thickness 0.45 mm) with a c-plane orientation and an off-angle of 0.2° was prepared as a device substrate. An Ir film and a diamond film were formed in sequence on the N-face side of this device substrate using the same method as in Example 1. The resulting product was a crack-free diamond / Ir / AlN laminated substrate. Cross-sectional observation revealed that the diamond film was approximately 105 μm thick. Furthermore, EBSD measurement results indicated that the diamond film was a biaxially oriented film with both the c-axis and a-axis oriented.

[0034] Example 3: A (111)-oriented, double-side-polished Si single crystal substrate (diameter 50.8 mm, thickness 1 mm) with no off-axis angle was prepared as a device substrate. A beryllium (Be) film was grown on one side of this device substrate. The film was formed by RF magnetron sputtering using metallic Be as the target under an Ar gas pressure of 1×10. －２ Torr and substrate temperature: The process was continued under the conditions of 750° C. until the Be film thickness reached 1.0 μm.

[0035] The bias treatment for forming diamond nuclei on the surface of the Be film of the obtained substrate was carried out as follows. First, the substrate was set on the negative voltage application electrode (cathode) of the bias treatment device, and vacuum evacuation was carried out. Next, the substrate was heated to 800°C, and then 3 vol. % hydrogen diluted methane gas was introduced, and the pressure was set to 130 Torr, and bias treatment was carried out. That is, a DC voltage was applied between both electrodes, and a predetermined direct current was passed.

[0036] Finally, single-crystal diamond was heteroepitaxially grown on the bias-treated surface by microwave plasma CVD at 950° C. for 3 hours.

[0037] After growth was completed, the product removed from the CVD apparatus was a crack-free diamond / Be / Si laminated substrate. Cross-sectional observation revealed that the diamond film was approximately 8 μm thick. EBSD measurements also revealed that the diamond film was a uniaxially oriented film with a c-axis orientation.

[0038] Example 4: A (111)-oriented, double-side-polished 3C-SiC single crystal substrate (diameter 50.8 mm, thickness 0.35 mm) with no off-axis angle was prepared as a device substrate. A beryllium (Be) film was grown on one side of this device substrate. The film was formed by RF magnetron sputtering using metallic Be as the target, with Ar gas: 1×10 －２ Torr and substrate temperature: The process was continued under the conditions of 750° C. until the Be film thickness reached 1.0 μm.

[0039] The bias treatment for forming diamond nuclei on the surface of the Be film of the obtained substrate was carried out as follows. First, the substrate was set on the negative voltage application electrode (cathode) of the bias treatment device, and vacuum evacuation was carried out. Next, the substrate was heated to 800°C, and then 3 vol. % hydrogen diluted methane gas was introduced, and the pressure was set to 130 Torr, and bias treatment was carried out. That is, a DC voltage was applied between both electrodes, and a predetermined direct current was passed.

[0040] Finally, single-crystal diamond was heteroepitaxially grown on the bias-treated surface by microwave plasma CVD at 100° C. for 10 hours.

[0041] After growth was complete, the product removed from the CVD apparatus was a crack-free diamond / Be / 3C-SiC laminate substrate. Cross-sectional observation revealed that the diamond film was approximately 30 μm thick. EBSD measurements also revealed that the diamond film was a biaxially oriented film, with both the c-axis and a-axis oriented.

[0042] Example 5: Double-sided polished Z-cut LiTaO with no off-angle ３A single crystal substrate (diameter 50.8 mm, thickness 0.5 mm) was prepared as a device substrate. An Ir film and a diamond film were formed in this order on one side of this device substrate in the same manner as in Example 1, except that the film formation time by microwave plasma CVD was 25 hours. The resulting product was a crack-free diamond / Ir / LiTaO ３ The cross-sectional observation revealed that the diamond film was approximately 90 μm thick. EBSD measurements also revealed that the diamond film was a biaxially oriented film, with both the c-axis and a-axis oriented.

[0043] Example 6 A laminated substrate was produced in the same manner as in Example 1, except that the deposition time of single crystal diamond by microwave plasma CVD was set to 150 hours. The GaN layer of the obtained laminated substrate was thinned to a thickness of 2 μm by polishing, to produce a laminated substrate for a device.

[0044] The product was a crack-free diamond / Ir / GaN laminate substrate. Cross-sectional observation revealed that the diamond film was approximately 300 μm thick. EBSD measurements also revealed that the diamond film was a biaxially oriented film, with both the c-axis and a-axis oriented.

Claims

1. Si, SiC, GaN, AlN, BN, Ga ２ O ３ , Cr ２ O ３ , LiTaO ３ and LiNbO ３ a device substrate made of at least one single crystal material selected from the group consisting of: a metal layer on the device substrate; a diamond layer on the metal layer; A laminated substrate having a three-layer structure consisting of:

2. The laminated substrate according to claim 1 , wherein the device substrate is made of at least one single crystal material selected from the group consisting of Si and SiC.

3. 2. The laminated substrate according to claim 1, wherein the device substrate is made of at least one single crystal material selected from the group consisting of GaN, AlN, and BN.

4. The device substrate is Ga ２ O ３ , Cr ２ O ３ , LiTaO ３ and LiNbO ３ The laminated substrate according to claim 1 , which is made of at least one single crystal material selected from the group consisting of:

5. 5. The laminated substrate according to claim 1, wherein the metal layer is made of a metal or alloy containing at least one selected from the group consisting of Ir, Rh, Pt, Ru, and Au.

6. 5. The laminated substrate according to claim 1, wherein the metal layer is made of a metal or alloy containing at least one selected from the group consisting of Ni, Cu, Fe, and Co.

7. 5. The laminated substrate according to claim 1, wherein the metal layer is made of a metal or alloy containing Be.

8. 5. The laminated substrate according to claim 1, wherein the metal layer is made of a metal or alloy containing Ir.

9. 5. The laminated substrate according to claim 1, wherein the diamond layer is made of a single crystal diamond.

10. 5. The laminated substrate according to claim 1, wherein the diamond layer is composed of a biaxially oriented layer of diamond.

11. 5. The laminated substrate according to claim 1, wherein the diamond layer is composed of a uniaxially oriented diamond layer.

12. 5. The laminated substrate according to claim 1, wherein the device substrate has a thickness of 1 μm to 30 μm.

13. 5. The laminated substrate according to claim 1, wherein the metal layer has a thickness of 50 nm to 100 μm.

14. 5. The laminated substrate according to claim 1, wherein the diamond layer has a thickness of 100 μm to 2.0 mm.

15. The thickness Ts of the device substrate, the thickness Tm of the metal layer, and the thickness Td of the diamond layer satisfy the relationship of Td≧Ts×10 and Td≧Tm×10.

16. The thickness Ts of the device substrate, the thickness Tm of the metal layer, and the thickness Td of the diamond layer satisfy the relationship of Ts ≧ Tm × 10 and Ts ≧ Td × 10.

17. The thickness Ts of the device substrate, the thickness Tm of the metal layer, and the thickness Td of the diamond layer satisfy the relationship of Tm≧Ts×10 and Tm≧Td×10.

18. The thickness Ts of the device substrate, the thickness Tm of the metal layer, and the thickness Td of the diamond layer satisfy the relationship of Ts ≧ Tm × 10 and Td ≧ Tm × 10.

19. 5. The laminated substrate according to claim 1, wherein the metal layer is a film made of a metal or alloy containing Be, which is formed by sputtering.