Gallium Nitride Substrate

Abstract

To provide a technology which is usable for inspection of a crystal quality of an epitaxial layer in a group III nitride laminate.SOLUTION: A gallium nitride substrate has a maximum defect density equal to or less than 5×106 cm-2 in a principal surface of the gallium nitride substrate. On each position arranged on a line segment B parallel to an azimuth of an off-angle on a position A, which passes the position A defined on the principal surface of the gallium nitride substrate, the azimuth of the off-angle is the same as the position A, and the size of the off-angle is monotonously changed in proportion to a distance from one end, from one end of the line segment B toward the other end.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a Group III nitride stack, a method for inspecting the same, and a Group III nitride stack. [Background technology]

[0002] Group III nitride semiconductors such as gallium nitride (GaN) are useful as materials for semiconductor devices such as optical devices, electronic devices, etc. A Group III nitride stack in which a Group III nitride epitaxial layer (hereinafter sometimes abbreviated as epilayer) is formed above a Group III nitride substrate has an epilayer with better crystal quality than a stack in which an epilayer is formed above a heterogeneous substrate such as sapphire (for example, see Patent Documents 1 and 2 for the construction of a semiconductor device by growing an epilayer on a Group III nitride substrate).

[0003] In semiconductor devices using III-nitride stacks, the crystal quality of the epitaxial layer has a significant effect on the performance of the device, making it important to have a technique for inspecting the crystal quality of the epitaxial layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-254970 A [Patent Document 2] Patent No. 5544723 Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide a technique that can be used to inspect the crystalline quality of epilayers in III-nitride stacks. [Means for solving the problem]

[0006] According to one aspect of the present invention, A gallium nitride substrate, 5×10 in the main surface of the gallium nitride substrate 6 cm -2 and having a maximum defect density of At each position located on a line segment B that passes through a position A defined on the primary surface of the gallium nitride substrate and is parallel to the orientation of the off-angle at the position A, the orientation of the off-angle is the same as that at the position A, and the magnitude of the off-angle changes monotonically from one end of the line segment B to the other end in proportion to the distance from the one end. Gallium Nitride Substrate is provided. Effect of the Invention

[0007] The correspondence between the magnitude of the off-angle and the relative yellow intensity can be used to inspect the crystal quality of epilayers in III-nitride stacks. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a flowchart showing a schematic flow of an inspection method according to an embodiment of the present invention. [Diagram 2] FIG. 2(a) is a schematic cross-sectional view of a III-nitride stack, and FIG. 2(b) is a schematic cross-sectional view showing a situation of PL mapping measurement for the III-nitride stack. [Diagram 3] FIG. 3(a) is a schematic diagram of the PL emission spectrum, and FIG. 3(b) is a graph showing a schematic relationship between the off amount and the relative yellow intensity. [Figure 4] FIG. 4 is a flowchart showing a schematic flow of an inspection method according to a first modified example of the embodiment. [Diagram 5] FIG. 5 is a flowchart showing a schematic flow of an inspection method according to a second modified example of the embodiment. [Figure 6] FIG. 6 is a flowchart showing a schematic flow of a method for estimating a physical quantity according to an application example. [Figure 7]FIG. 7(a) is a schematic plan view illustrating the orientation of a hexagonal Group III nitride crystal, FIG. 7(b) is a schematic cross-sectional view illustrating the off-angle distribution of substrates in an experimental example, and FIG. 7(c) is a schematic diagram showing the off-angle distribution of an a-off substrate, an m-off substrate, and an improved m-off substrate in the experimental example. [Figure 8] FIG. 8 is a graph showing the amount of offset on the center line segment of each substrate in the experimental example versus the position on the substrate. [Figure 9] FIG. 9(a) is a schematic plan view showing the epitaxial layer growth process in the experimental example, and FIG. 9(b) is a schematic cross-sectional view showing the III-nitride stack in the experimental example. [Figure 10] 10(a) and 10(b) are graphs showing the relative yellow intensity of the III-nitride stack in the experimental example versus the position on the substrate and versus the off-amount, respectively. [Figure 11] FIG. 11(a) is a graph showing the carrier concentration (net donor concentration) and acceptor concentration of a III-nitride stack in an experimental example versus the off-amount, and FIG. 11(b) is a graph showing the acceptor concentration versus the relative yellow intensity. [Figure 12] FIG. 12 is a schematic diagram showing a III-nitride stack with a physical quantity map. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Embodiment> A method for inspecting a group III nitride stack according to an embodiment of the present invention will now be described with reference to a flowchart of FIG 1.

[0010] First, in step S1, a reference III-nitride stack 100 (hereinafter referred to as stack 100 or reference stack 100) is prepared.

[0011] 2(a) is a schematic cross-sectional view of the laminate 100. The laminate 100 is composed of a group III nitride semiconductor. As the group III nitride semiconductor, a gallium nitride (GaN)-based semiconductor, that is, a semiconductor containing gallium (Ga) and nitrogen (N) is used. Although GaN is exemplified as a GaN-based semiconductor, the GaN-based semiconductor is not limited to GaN, and may contain, in addition to Ga and N, a group III element other than Ga as necessary.

[0012] Examples of group III elements other than Ga include aluminum (Al) and indium (In). However, from the viewpoint of reducing lattice strain, it is preferable that group III elements other than Ga are contained so that the lattice mismatch of the GaN-based semiconductor with GaN is 1% or less. The allowable content in the GaN-based semiconductor is, for example, 40 atomic % or less of group III elements for Al in AlGaN, and 10 atomic % or less of group III elements for In in InGaN. Note that InAlGaN may be InAlGaN, which is a combination of InAlN, in which In is 10 atomic % or more and 30 atomic % or less of group III elements, and GaN, with any composition. When the Al composition and In composition are within the above range, the lattice strain with GaN is unlikely to become large, and cracks are unlikely to occur.

[0013] The laminate 100 has a III-nitride substrate 110 (hereinafter, substrate 110) and a III-nitride epitaxial layer 120 (hereinafter, epilayer 120) formed above the substrate 110. Another III-nitride epitaxial layer may be interposed between the substrate 110 and the epilayer 120. Details of preferred characteristics of the substrate 110 used in the laminate 100 will be described later.

[0014] The substrate 110 has a primary surface 111. The angle between the normal direction of the primary surface 111 and the c-axis direction of the Group III nitride crystal constituting the substrate 110 is the off angle. The off angle is defined by its orientation and magnitude. The orientation of the off angle is referred to as the "off direction," and the magnitude of the off angle is referred to as the "off amount."

[0015] The substrate 110 is a c-plane substrate. When the substrate 110 is a c-plane substrate, it means that the amount of off-axis is, for example, not less than 0° and not more than 1.2° over the entire area of ​​the main surface 111.

[0016] For the substrate 110, the off-angle distribution in the main surface 111 is acquired. That is, at least one of the off-direction and the off-amount in the main surface 111 is known, and in particular, the off-amount is known. Here, the step of measuring the off-angle distribution in the main surface 111 may be included in step S1. X-ray diffraction can be used to measure the off-angle distribution. When the substrate 110 with a known off-angle distribution is used, the step of measuring the off-angle distribution does not need to be included in step S1.

[0017] The epilayer 120 is formed above the main surface 111 of the substrate 110 by metal-organic vapor phase epitaxy (MOVPE or MOCVD, hereinafter referred to as MOVPE). For this reason, the epilayer 120 unintentionally contains carbon derived from the Group III organic source gas as an impurity. Here, the step of growing the epilayer 120 may be included in step S1. When preparing the stack 100 by obtaining the stack 100 on which the epilayer 120 is already formed, the step of growing the epilayer 120 may not be included in step S1.

[0018] The substrate 110 and the epitaxial layer 120 have n-type conductivity. Examples of n-type impurities include silicon (Si) and germanium (Ge). The substrate 110 contains n-type impurities at a concentration of, for example, 1×10 18 cm -3 More than 1×10 19 cm -3 The epitaxial layer 120 is doped with n-type impurities at a concentration of, for example, 3×10 15 cm -3 5×10 or more 16 cm -3 The epitaxial layer 120 is doped with n-type impurity at the following concentration. The n-type impurity concentration of the epitaxial layer 120 is lower than the n-type impurity concentration of the substrate 110. The thickness of the substrate 110 is not particularly limited, but is, for example, 400 μm. The thickness of the epitaxial layer 120 is, for example, 10 μm to 30 μm.

[0019] The epitaxial layer 120 corresponds to a drift layer when a semiconductor device such as a Schottky diode or a pn junction diode is manufactured using a group III nitride stack similar to the stack 100. From the viewpoint of suppressing the on-resistance, it is preferable that the n-type impurity concentration of the epitaxial layer 120 is not too low, for example, 3×10 15 cm -3 From the viewpoint of improving the breakdown voltage, it is preferable that the n-type impurity concentration of the epitaxial layer 120 is not too high. 16 cm -3 It is preferable that the value is less than 1×10 16 cm -3 From the viewpoint of improving the breakdown voltage, the thickness of the epitaxial layer 120 is preferably not too thin, for example, 10 μm or more. Also, from the viewpoint of suppressing the on-resistance, the thickness of the epitaxial layer 120 is preferably not too thick, for example, 30 μm or less.

[0020] As described above, in step S1, the laminate 100 having the substrate 110 and the epitaxial layer 120 formed above the main surface 111 of the substrate 110 is prepared.

[0021] Next, in step S2, a photoluminescence (PL) mapping measurement is performed on the laminate 100 to obtain the relative yellow intensity, and the correspondence relationship between the off amount and the relative yellow intensity is obtained.

[0022] 2(b) is a schematic cross-sectional view showing a situation of PL mapping measurement of the laminate 100. In the PL mapping measurement, PL measurement is performed on a minute region, for example, a region with a diameter of 5 μm, at a measurement position 122 defined on a surface 121 of an epitaxial layer 120, to obtain a PL emission spectrum at the measurement position 122. Excitation light 11 is irradiated from an excitation light source 10 to the measurement position 122, and PL light 12 is emitted. The PL light 12 is incident on a detector 13, and a PL emission spectrum corresponding to the measurement position 122 is obtained.

[0023] 3(a) is a schematic diagram of a PL emission spectrum 20. The horizontal axis is wavelength in nm, and the vertical axis is intensity in arbitrary units. The PL emission spectrum 20 has a band-edge emission peak 21 and a yellow emission peak 22. The yellow emission peak 22 is believed to correspond to a deep level due to carbon, gallium vacancies, etc. mixed into the epitaxial layer 120.

[0024] Peak wavelength λ of band edge emission peak 21 NBE Although it may vary depending on the composition of the epitaxial layer 120, for example, in the case of GaN, the peak wavelength λ NBE is 365 nm, and the corresponding energy is 3.4 eV. YL Although it may vary depending on the composition of the epitaxial layer 120, the growth conditions, etc., it can be said to be a wavelength in the range of 500 nm to 650 nm. For example, in the case of GaN, the peak wavelength λ YL The wavelength of the band edge emission peak λ is 564 nm, and the corresponding energy is 2.2 eV. NBE and yellow emission peak wavelength λ YL varies depending on the amount of Al or In in the GaN-based semiconductor.

[0025] Peak 21 has an emission intensity of Int NBE and peak 22 has an emission intensity Int YL The relative yellow intensity is calculated by the band edge emission intensity Int NBE Yellow emission intensity Int YL Ratio of Int YL / Int NBE It is defined as:

[0026] The measurement position 122 and a position in the main surface 111 of the substrate 110 arranged directly below it can be treated as the same position in a plan view. A position in the main surface 111 where the off-amount is known is selected as the measurement position 122. PL mapping measurement is performed for a plurality of measurement positions 122 with different off-amounts. By performing PL measurement for the plurality of measurement positions 122, the distribution of the PL emission spectrum in the surface 121 is acquired.

[0027] In this embodiment, a measurement in which the PL emission spectrum is obtained for one or more measurement positions is called a PL mapping measurement. That is, even a measurement in which the PL emission spectrum is obtained for one measurement position without scanning the measurement positions, in other words, without obtaining PL emission spectra for two or more measurement positions, is called a PL mapping measurement.

[0028] A relative yellow intensity is calculated for the PL emission spectrum acquired for each measurement position 122. That is, a relative yellow intensity is calculated for each measurement position 122 having a different off amount.

[0029] Then, by associating the OFF amount with the relative yellow intensity, a correspondence relationship between the OFF amount and the relative yellow intensity is acquired.

[0030] Fig. 3(b) is a graph showing a schematic relationship between the off amount and the relative yellow intensity (hereinafter, sometimes simply referred to as the correspondence). The horizontal axis is the off amount expressed in degrees, and the vertical axis is the relative yellow intensity expressed in arbitrary units. The solid line 30 shows the graph of the correspondence. The upper and lower dashed lines 31 and 32 show the boundaries of the allowable range described below.

[0031] The findings regarding the correspondence described below were discovered by the present inventors, as will be described in detail in the experimental examples below. The relative yellow intensity does not depend on the off-direction, that is, does not depend on whether the off-direction is the a-axis direction or the m-axis direction, but is determined depending on the off-amount. In other words, the off-amount and the relative yellow intensity have a correspondence relationship that is independent of the off-direction.

[0032] The correspondence relationship has a tendency that as the off amount increases, the relative yellow intensity decreases and the degree of decrease in the relative yellow intensity becomes smaller. off and the relative yellow intensity is expressed as Int(θ off), it can be approximately expressed by equation (1) using the decay constant λ of the exponential function, the critical off amount θ0 which makes the argument of the exponential function zero, the constant A which is multiplied by the exponential function, and the constant Int0 which is added to the exponential function.

number

[0033] As described above, in step S2, the PL mapping measurement is performed for a plurality of measurement positions with different off amounts of the laminate 100, and the band edge emission intensity Int NBE Yellow emission intensity Int YL A relative yellow intensity, which is a ratio of the above values, is obtained, and a correspondence relationship between the off amount and the relative yellow intensity is obtained.

[0034] Next, in step S3, the group III nitride stack 200 to be inspected (hereinafter, referred to as stack 200 or inspected stack 200) is prepared.

[0035] The test stack 200 has a structure similar to that of the reference stack 100, so the test stack 200 will be described with reference to Fig. 2(a) again. Fig. 2(a) is a schematic cross-sectional view of the stack 200. The stack 200 has a III-nitride epitaxial layer 220 (hereinafter, epilayer 220) formed by MOVPE above a primary surface 211 of a III-nitride substrate 210 (hereinafter, substrate 210).

[0036] From the viewpoint of applying the correspondence relationship acquired for the reference stack 100 to the inspection of the inspection stack 200, it is preferable that the growth conditions of the epilayer 220 of the inspection stack 200 are controlled to be the same as those of the epilayer 120 of the reference stack 100. That is, in MOVPE, the type of supply gas such as source gas, the supply gas supply conditions such as V / III ratio, the growth temperature, the growth pressure, etc. are preferably controlled to be the same for the growth of the epilayer 120 of the reference stack 100 and the growth of the epilayer 220 of the inspection stack 200. Note that it is difficult to completely match the growth conditions of the epilayer 120 and the epilayer 220, so it is preferable that the two are substantially the same within the allowable error.

[0037] The n-type impurity concentration is preferably controlled to be the same in epilayer 120 and epilayer 220, and the error in the n-type impurity concentration of epilayer 220 relative to the n-type impurity concentration of epilayer 120 is preferably within ±2%. Furthermore, the layer thickness is preferably controlled to be the same in epilayer 120 and epilayer 220, and the error in the thickness of epilayer 220 relative to the thickness of epilayer 120 is preferably within ±5%.

[0038] For the substrate 210, the off-angle distribution in the main surface 211 is acquired. That is, at least one of the off-direction and the off-amount in the main surface 211 is known, and especially the off-amount is known. Here, the step of measuring the off-angle distribution in the main surface 211 may be included in step S3. X-ray diffraction can be used to measure the off-angle distribution. When the substrate 210 with a known off-angle distribution is used, the step of measuring the off-angle distribution does not need to be included in step S3.

[0039] The step of growing the epi layer 220 may be included in step S3. If the stack 200 is prepared by obtaining a stack 200 on which the epi layer 220 is already formed, the step of growing the epi layer 220 may not be included in step S3.

[0040] As described above, in step S3, the laminate 200 including the substrate 210 and the epitaxial layer 220 formed above the main surface 211 of the substrate 210 is prepared.

[0041] Next, in step S4, a PL mapping measurement is performed on the laminate 200 to obtain the relative yellow intensity.

[0042] The PL mapping measurement is basically the same as that for the stack 100, and therefore will be described with reference to Fig. 2(b) again. It is preferable that the measurement conditions, such as the wavelength, power, and spot size of the excitation light, are controlled to be the same as those for the stack 100. In the PL mapping measurement, a PL emission spectrum is obtained at an inspection position 222 defined on the surface 221 of the epitaxial layer 220. The PL mapping measurement is performed for at least one inspection position 222.

[0043] The inspection position 222 and a position in the main surface 211 of the substrate 210 disposed directly below the inspection position 222 can be treated as the same position in a plan view. A position in the main surface 211 where the amount of off-axis is known is selected as the inspection position 222. The amount of off-axis at the inspection position 222 is called the inspection position off-axis amount.

[0044] A relative yellow intensity is calculated for the PL emission spectrum acquired for the inspection position 222. That is, a relative yellow intensity is calculated for the inspection position 222 having an inspection position off amount.

[0045] As described above, in step S4, a PL mapping measurement is performed on inspection position 222 of stack 200 to obtain the relative yellow intensity.

[0046] Next, in step S5, the relative yellow color intensity of the laminate 200 obtained in step S4 is compared with the relative yellow color intensity obtained from the correspondence relationship obtained in step S2.

[0047] From the correspondence relationship obtained in step S2, the relative yellow intensity is calculated as follows. For the inspection position 222, the relative yellow intensity is calculated from the inspection position offset amount based on the correspondence relationship. More specifically, when the inspection position offset amount θ off By substituting into equation (1), the relative yellow intensity Int(θ off ) is calculated.

[0048] Referring again to FIG. 3B, two comparative examples will be described. The white circle 33 indicates the inspection position offset amount θ offThe black circles 34 and 35 indicate the relative yellow intensity obtained from the PL mapping measurement for the inspection position 222 in step S4 with respect to the inspection position offset amount θ off A filled circle 34 indicates the relative yellow intensity of the first example (which will be referred to as relative yellow intensity 34), and a filled circle 35 indicates the relative yellow intensity of the second example (which will be referred to as relative yellow intensity 35).

[0049] The first example is an example in which the relative yellow intensity 34 obtained from the PL mapping measurement matches well with the relative yellow intensity 33 obtained from the correspondence relationship (the difference is within an allowable range). When the relative yellow intensity 34 matches well with the relative yellow intensity 33, it is determined that the crystal growth at the inspection position 222 of the epilayer 220 of the stack 200 has been performed normally. In other words, it is determined that the crystal quality of the epilayer 220 is good.

[0050] In the second example, the relative yellow intensity 35 obtained from the PL mapping measurement significantly deviates from the relative yellow intensity 33 obtained from the correspondence relationship, and the difference between them exceeds the allowable range. When the relative yellow intensity 35 significantly deviates from the relative yellow intensity 33, it is determined that the crystal growth at the inspection position 222 of the epilayer 220 of the stack 200 was not normal.

[0051] The allowable range of the difference from the relative yellow intensity 33 may be set appropriately as necessary. In this example, the area between the dashed lines 31 and 32 indicates the allowable range. The dashed lines 31 and 32 are curves in which the parameters λ, A, and Int0 in formula (1) are 50% higher and 50% lower than the parameters λ, A, and Int0 representing the solid line 30, respectively.

[0052] For example, crystal growth may not be performed normally due to insufficient decomposition of the Group III organic source gas or peeling of the silicon carbide (SiC) coating from the susceptor of the crystal growth apparatus. In such a case, the concentration of carbon mixed into the epitaxial layer 220 increases significantly, causing the relative yellow intensity to increase and a large upward deviation from the correspondence relationship (solid line 30). If there are many inspection positions where the relative yellow intensity is outside the allowable range and some abnormality is suspected, it is advisable to inspect and adjust the crystal growth conditions and the crystal growth apparatus.

[0053] On the other hand, a large downward deviation from the correspondence (solid line 30), i.e., a weakening of the relative yellow intensity, can be interpreted as an indication that the crystal quality of the epitaxial layer 220 is rather good, and is unlikely to occur, but it may occur. If there is a large downward deviation, inspection and adjustment of the PL mapping measurement device, etc., may be performed in addition to the crystal growth conditions and crystal growth device.

[0054] As described above, in step S5, the relative yellow intensity obtained from the PL mapping measurement for the inspection position 222 of the laminate 200 is compared with the relative yellow intensity obtained from the correspondence relationship for the inspection position off amount.

[0055] Next, in step S6, the stack 200 determined to have had normal crystal growth of the epitaxial layer 220 based on the comparison in step S5 is selected as a non-defective product. The stack 200 selected as a non-defective product is used as a material for manufacturing a semiconductor device. In addition, in steps performed after step S6 to manufacture a semiconductor device, a step of forming an electrode above the epitaxial layer 220 and the like are performed.

[0056] In this manner, the method for inspecting a group III nitride stack according to the embodiment is performed. According to the inspection method of the embodiment, by using the correspondence between the off amount and the relative yellow intensity, it is possible to inspect whether the crystal growth of the epitaxial layer 220 of the inspection stack 200 has been performed normally. Then, when it is determined that the crystal growth has been performed normally, the inspection stack 200 can be used as a material for a semiconductor device as a non-defective product. Also, when it is determined that the crystal growth has not been performed normally, for example, further inspection or adjustment of the growth conditions, the crystal growth device, etc. can be performed. The inspection position 222 of the inspection stack 200 may be one position, or may be two or more positions. The inspection method of the embodiment can be performed by PL mapping measurement for the inspection position 222, so that it can be performed non-destructively and easily.

[0057] The reference laminate 100 used to obtain the correspondence relationship may be one, or may be two or more, i.e., a plurality of laminates 100, as in an experimental example described later. By using a plurality of laminates 100, it becomes easier to obtain the correspondence relationship with high accuracy for a wide range of off amounts, as compared with the case where only one laminate 100 is used, as described later.

[0058] The order of steps S1 to S5 described in the flow chart of FIG. 1 may be changed as appropriate. Step S1 of preparing the laminate 100 may be performed before step S2 of performing PL mapping measurement, etc. on the laminate 100. Step S3 of preparing the laminate 200 may be performed before step S4 of performing PL mapping measurement, etc. on the laminate 200. Step S2 of acquiring the correspondence relationship and step S4 of acquiring the relative yellow intensity from the PL mapping measurement of the laminate 200 may be performed before step S5 of comparing the relative yellow intensity obtained from the PL mapping measurement of the laminate 200 with the relative yellow intensity obtained from the correspondence relationship. Either step S2 of acquiring the correspondence relationship or step S4 of acquiring the relative yellow intensity from the PL mapping measurement of the laminate 200 may be performed first.

[0059] The stack 100 can be regarded as a Group III nitride stack in which the correspondence relationship between the off-amount and the relative yellow intensity of the epilayer 120 tends to be such that as the off-amount increases, the relative yellow intensity decreases and the degree of decrease in the relative yellow intensity becomes smaller.

[0060] Next, a description will be given of a method for manufacturing the substrate 110. Also, a description will be given of preferred characteristics of the substrate 110 used in the laminate 100. The substrate 110 is manufactured by hydride vapor phase epitaxy (HVPE) using the void-assisted exfoliation (VAS) method.

[0061] In the VAS method, first, an underlayer is formed on a growth substrate. For example, a sapphire substrate is used as the growth substrate. For example, a low-temperature grown GaN buffer layer and a Si-doped GaN layer are formed as the underlayer by metalorganic vapor phase epitaxy. Next, a metal layer is formed on the underlayer. For example, a titanium layer is formed by vapor deposition as the metal layer.

[0062] The metal layer is then nitrided by heat treatment in an atmosphere containing a nitriding gas to form a metal nitride layer having a high density of fine holes on the surface, and the heat treatment also etches a part of the underlayer through the holes in the metal nitride layer to form a void-containing underlayer.

[0063] In order to obtain a substrate 110 suitable for use in the laminate 100, in this example, the heat treatment has the following characteristics. The heat treatment is performed so that the "void ratio (volume porosity)", which is the volume ratio of voids in the void-containing underlayer, is made uniform in the circumferential direction on the growth substrate. Specifically, for example, the susceptor on which the growth substrate is placed is rotated to perform the heat treatment uniform in the circumferential direction. Also, for example, the temperature distribution of the growth substrate is made uniform in the circumferential direction by adjusting the heating condition of the heater within the plane of the growth substrate.

[0064] Furthermore, the heat treatment is performed so that the void ratio of the void-containing underlayer increases radially from the center to the outer periphery of the growth substrate. Specifically, for example, the temperature of the growth substrate is monotonically increased radially from the center to the outer periphery by adjusting the heating condition of a heater within the plane of the growth substrate.

[0065] Next, a Si-doped GaN layer is grown as a thick full-grown layer on the void-containing underlayer and the metal nitride layer of the growth substrate by HVPE. During this growth, gaps are formed between the full-grown layer and the metal nitride layer due to the voids present in the void-containing underlayer. By controlling the void ratio of the void-containing underlayer as described above, the gaps are formed uniformly in the circumferential direction and are enlarged from the center toward the outside in the radial direction.

[0066] In the cooling process after the growth of the full-grown layer is completed, the full-grown layer naturally peels off from the growth substrate at the gap formed between the full-grown layer and the metal nitride layer. The gap is formed to be uniform in the circumferential direction and to be larger from the center side toward the outside in the radial direction, so that the full-grown layer can be peeled off evenly in the circumferential direction so that the peeling proceeds from the outer periphery side toward the center side of the growth substrate. The full-grown layer after peeling is sliced ​​to obtain the substrate 110.

[0067] The full-growth layer has a low defect density on the growth surface side (front side) and a high defect density on the growth substrate side (back side). Due to this difference in defect density, the peeled full-growth layer warps so that the front side is concave. The main surface of the substrate 110 obtained by slicing the warped full-growth layer will have an off-angle distribution.

[0068] The substrate 110 produced by the VAS method as described above is preferable for use in the laminate 100 in at least the following two respects. First, the substrate 110 is preferable in that the main surface 111 does not have an area with an extremely high defect density. This makes it possible to obtain the laminate 100 having the correspondence between the off-amount and the relative yellow color intensity as described above.

[0069] If a substrate having a region with extremely high defect density on the main surface is used, the epitaxial layer grown on the region has poor crystal quality and therefore has a strong relative yellow intensity. Therefore, even if the off-amount is the same, the relative yellow intensity on the region with extremely high defect density and the other regions will be significantly different, and the above-mentioned correspondence between the off-amount and the relative yellow intensity cannot be obtained.

[0070] Specific preferred conditions for the defect density are, for example, as follows: When the observation area is scanned and measured in a measurement area of ​​3 mm square in the main surface 111 of the substrate 110 by a cathodoluminescence (CL) method, the maximum defect density is 5×10 6 cm -2 The maximum defect density is more preferably 10 times or less than the average defect density, and even more preferably 10 times or less than the minimum defect density. An example of the maximum defect density is 4.7×10 6 cm -2 It is.

[0071] Secondly, substrate 110 is preferable in that it has the following off-angle distribution. Consider position A on main surface 111 of substrate 110. Position A is defined, for example, at the center of substrate 110 (hereinafter referred to as substrate center), but may be defined elsewhere than the substrate center. In a circular substrate, when a cut-out portion such as an orientation flat is present, the substrate center is the center of the circle that complements the cut-out portion. Consider line segment B on main surface 111 that passes through position A and is parallel to the off-direction at position A. At each position on line segment B, the off-direction is the same as that of position A (parallel to line segment B), and the off-angle changes monotonically from one end of line segment B to the other end in proportion to the distance from the one end (see FIG. 7(c) and FIG. 8).

[0072] In the above-mentioned method, the gap between the full-grown layer and the metal nitride layer is formed so as to be uniform in the circumferential direction and to be larger from the center side to the outside in the radial direction, so that the full-grown layer is peeled off uniformly in the circumferential direction from the outer periphery side to the center side of the growth substrate. In addition, by forming such a gap, the generation of excessive stress locally in the surface of the full-grown layer during growth is suppressed.

[0073] By growing and peeling off such a full-grown layer, it is possible to obtain a substrate 110 in which the off-angle distribution changes smoothly and continuously; more specifically, it is possible to obtain a substrate 110 having the characteristic that the off-angle is proportional as described above.

[0074] Since substrate 110 has such an off-angle distribution and does not have any regions with extremely high defect density, the in-plane distribution of physical quantities possessed by epitaxial layer 120 grown on substrate 110, particularly physical quantities such as relative yellow intensity that tend to change monotonically depending on the off-angle, can be changed to a distribution that tends to change smoothly and continuously. This makes it possible to provide regions in stack 100 in which the epitaxial layer 120 has roughly the same physical quantities as a single large region. Stack 100 having such characteristics is preferable as a material for manufacturing semiconductor devices.

[0075] Although the preferred features of the stack and the substrate have been described using the reference stack 100 and the substrate 110 as examples, the same features also apply to the test stack 200 and the substrate 210.

[0076] <First Modification> Next, a method for inspecting a III-nitride stack according to a first modified example of the above-described embodiment will be described below. Fig. 4 is a flow chart showing a schematic flow of the inspection method according to the first modified example.

[0077] In the above embodiment, an example has been described in which the correspondence relationship between the off amount and the relative yellow intensity is acquired by performing a PL mapping measurement or the like on the laminate 100 (steps S1 and S2). However, the correspondence relationship once acquired can be used any number of times by, for example, making it a database, and the first modified example assumes a form in which such a correspondence relationship previously acquired is used.

[0078] First, in step S11, a correspondence relationship between the off amount and the relative yellow intensity is prepared. The correspondence relationship is prepared in the form of, for example, a database.

[0079] The subsequent steps S12 to S15 are the same as steps S3 to S6 in the above-described embodiment. That is, for the inspection position 222 of the laminate 200, a PL mapping measurement is performed to obtain the relative yellow intensity, and the relative yellow intensity obtained by the PL mapping measurement is compared with the relative yellow intensity obtained from the correspondence relationship to select the laminate 200 as a non-defective product.

[0080] According to the first modified example, it is possible to omit the work of performing PL mapping measurement or the like of the reference stack 100 for obtaining the correspondence relationship prior to the PL mapping measurement or the like of the test stack 200, thereby making the test more efficient.

[0081] 4 may be changed as appropriate. Step S12 of preparing the laminate 200 may be performed before step S13 of performing a PL mapping measurement or the like on the laminate 200. Step S11 of preparing the correspondence relationship and step S13 of acquiring a relative yellow intensity from a PL mapping measurement of the laminate 200 may be performed before step S14 of comparing the relative yellow intensity obtained from the PL mapping measurement of the laminate 200 with the relative yellow intensity obtained from the correspondence relationship. Either step S11 of preparing the correspondence relationship or step S13 of acquiring a relative yellow intensity from a PL mapping measurement of the laminate 200 may be performed first.

[0082] Note that the step of preparing the correspondence relationship (step S11 in the first modified example) may also include the step of acquiring the correspondence relationship by performing a PL mapping measurement or the like of the reference stack 100 (steps S1 and S2 in the above-described embodiment). When considered in this way, the above-described embodiment can also be included in the first modified example.

[0083] <Second Modification> Next, a method for inspecting a III-nitride stack according to a second modified example of the above-described embodiment will be described below. Fig. 5 is a flow chart showing a schematic flow of the inspection method according to the second modified example.

[0084] In the above embodiment, an example has been described in which the correspondence is acquired for the reference stack 100 (steps S1 and S2), and the test stack 200, which is another stack, is inspected (steps S3 to S5). The epitaxial layer 120 of the reference stack 100 preferably has good crystal quality, but depending on the measurement position 122, the crystal quality may not be good. Therefore, the reference stack 100 may be inspected while the correspondence is acquired. The second modified example assumes a configuration in which the reference stack 100 used to acquire the correspondence also serves as the test stack to be inspected.

[0085] In the second variant, first, in steps S21 and S22, similar to steps S1 and S2 in the above-described embodiment, a laminate 100 is prepared, a PL mapping measurement is performed on the laminate 100, the relative yellow intensity is obtained, and the correspondence relationship between the off amount and the relative yellow intensity is obtained.

[0086] Next, in step S23, a specific measurement position 122 is set as an inspection position, and the relative yellow intensity obtained by PL mapping measurement at the inspection position is compared with the relative yellow intensity obtained from the correspondence relationship. In step S24, non-defective laminates 100 are selected.

[0087] The concept of the comparison is the same as that explained for the inspection position 222 of the laminate 200 in the above embodiment. That is, when the relative yellow intensity obtained by the PL mapping measurement matches well with the relative yellow intensity obtained from the correspondence relationship, it is determined that the crystal growth at the measurement position (inspection position) 122 has been performed normally. On the other hand, when the relative yellow intensity obtained by the PL mapping measurement is significantly different from the relative yellow intensity obtained from the correspondence relationship, it is determined that the crystal growth at the measurement position (inspection position) 122 has not been performed normally.

[0088] According to the second modification, for the laminate 100, the correspondence can be acquired, and the crystal quality of each measurement position (inspection position) 122 can be inspected.

[0089] As described above, the inspection method of the Group III nitride stack according to the embodiment and the first and second modifications is performed. The inspection method according to the embodiment and the first and second modifications can also be regarded as a method for evaluating a Group III nitride stack. Furthermore, the inspection method according to the embodiment and the first and second modifications can be implemented as at least a part of a method for manufacturing a Group III nitride stack, or at least a part of a method for manufacturing a semiconductor device using a Group III nitride stack, and can also be regarded as a method for manufacturing a Group III nitride stack, or a method for manufacturing a semiconductor device.

[0090] <Application Examples> As described above, the correspondence relationship between the off amount and the relative yellow intensity can be used to inspect the crystal quality of the epitaxial layer at the inspection position based on the relative yellow intensity. In another embodiment, the correspondence relationship may be applied as follows.

[0091] For example, the following applications are possible. Carrier concentration (net donor concentration) can be measured by performing capacitance-voltage (CV) measurement on the epilayer of the III-nitride stack. As will be described in the experimental example below, the acceptor concentration can also be obtained by CV measurement. By performing CV measurement on a plurality of measurement positions with different off amounts, the correspondence between the off amount and the carrier concentration (or the off amount and the acceptor concentration) can be obtained. Then, by associating the correspondence with the correspondence between the off amount and the relative yellow intensity via the off amount, the correspondence between the relative yellow intensity and the carrier concentration (acceptor concentration) can be obtained. Therefore, if the CV measurement is performed on the epilayer of the reference stack in advance, the carrier concentration (acceptor concentration) of the epilayer of the test stack can be estimated by obtaining the relative yellow intensity by PL mapping measurement at the test position without performing CV measurement.

[0092] FIG. 6 is a flowchart showing a schematic flow of a method for estimating a carrier concentration (acceptor concentration) according to such an application example. In step S31, a first correspondence relationship is prepared, which is a correspondence relationship between the off amount and the relative yellow intensity. The first correspondence relationship may be prepared by measuring a reference stack, or may be prepared in the form of a database. In step S32, a second correspondence relationship is prepared, which is a correspondence relationship between the off amount and the carrier concentration (acceptor concentration). The second correspondence relationship may be prepared by measuring a reference stack, or may be prepared in the form of a database. In step S33, the first correspondence relationship and the second correspondence relationship are associated with each other via the off amount to obtain a third correspondence relationship, which is a correspondence relationship between the relative yellow intensity and the carrier concentration (acceptor concentration). Note that either step S31 or step S32 may be performed first. Also, step S31 and step S32 may be omitted, and a third correspondence relationship prepared in advance in the form of a database may be used in step S33.

[0093] In step S34, an inspection laminate is prepared. In step S35, a PL mapping measurement is performed on the inspection position of the inspection laminate to obtain a relative yellow intensity. In step S36, a carrier concentration (acceptor concentration) is obtained based on the relative yellow intensity obtained in step S35 and the third correspondence relationship obtained in step S33. In step S37, an inspection laminate is selected as a non-defective product whose carrier concentration (acceptor concentration) satisfies a predetermined condition.

[0094] Further, for example, the following applications are conceivable. By performing secondary ion mass spectrometry (SIMS) measurement on the epilayer of the III-nitride stack, the concentration of carbon, etc. can be measured. By performing SIMS measurement on a plurality of measurement positions with different off-amounts, the correspondence between the off-amount and the concentration of carbon, etc. can be obtained. By associating the correspondence with the correspondence between the off-amount and the relative yellow intensity via the off-amount, the concentration of carbon, etc. can be estimated from the relative yellow intensity obtained by the PL mapping measurement, based on a concept similar to that of the above-mentioned CV measurement, without performing SIMS measurement.

[0095] In addition, for physical quantities that can be obtained by methods other than CV measurement and SIMS measurement, such as deep level transient spectroscopy (DLTS) measurement, the correspondence between the off-amount and the physical quantity may be correlated with the correspondence between the off-amount and the relative yellow intensity via the off-amount to obtain the correspondence between the relative yellow intensity and the physical quantity, thereby making it possible to estimate the physical quantity from the relative yellow intensity.

[0096] <Experimental Example> Next, an experimental example will be described. In this experimental example, the relationship between the off-angle and the relative yellow intensity was examined for a laminate in which an epitaxial layer was grown above a substrate. Three types of substrates manufactured by the VAS method as described above were used as substrates. First, the substrates will be described.

[0097] 7(a) is a schematic plan view illustrating the orientations of a hexagonal III-nitride crystal. The a-axis direction is exemplified as the [11-20] orientation, the [-12-10] orientation, and the [2-1-10] orientation, and the m-axis direction is exemplified as the [10-10] orientation and the [1-100] orientation. The c-axis direction is the

[0001] orientation.

[0098] FIG. 7(b) is a schematic cross-sectional view illustrating the off-angle distribution of the substrate 40. The cross-sectional view is parallel to the a-axis direction passing through the center of the substrate. The substrate 40 (a-off substrate described later) is illustrated, in which the off-direction of the substrate center is parallel to the a-axis direction. The substrate 40 has a main surface 40a. The c-plane 40b of the group III nitride crystal constituting the substrate 40 is indicated by a broken line. The angle between the normal direction 40c of the main surface 40a and the c-axis direction 40d is the off-angle. The off-angle distribution occurs within the main surface 40a due to the curvature of the c-plane 40b. Note that the off-angle distribution, that is, the change in the c-axis direction 40d of the crystal within the main surface 40a, also changes the a-axis direction of the crystal. That is, the inclination of the a-axis direction of the crystal from the main surface 40a changes. In this specification, in order to avoid complicating the explanation, when the off-direction of the a-off substrate is referred to as the "a-axis direction," the a-axis direction refers not to the a-axis direction of the crystal itself but to the direction obtained by projecting the a-axis direction of the crystal onto the main surface 40a (the direction parallel to the main surface 40a). The same applies to the off-direction of the m-off substrate, which will be described later, when the "m-axis direction" is referred to.

[0099] In this experimental example, a substrate in which the off-direction of the substrate center is parallel to the a-axis direction (called an a-off substrate) and a substrate in which the off-direction of the substrate center is parallel to the m-axis direction (called an m-off substrate) were used. One a-off substrate and two m-off substrates were used. Of the two m-off substrates, one has a small off-angle distribution (called an improved m-off substrate). The improved m-off substrate can be obtained by growing a thicker film by HVPE than when manufacturing a normal m-off substrate.

[0100] 7(c) is a schematic diagram showing the off-angle distributions of the a-off substrate 40, the m-off substrate 41, and the m-off improved substrate 42. In the figure, the a-off substrate is indicated as "a-off VAS", the m-off substrate is indicated as "m-off VAS", and the m-off improved substrate is indicated as "m-off modified VAS".

[0101] The position where the off angle (off amount) is zero is set as the origin, and the a-axis and m-axis directions are shown radially from the origin, and the off amount is shown in proportion to the distance from the origin. Positions where the off amount is 0.2°, 0.4°, 0.6°, 0.8°, and 1.0° are shown concentrically.

[0102] The a-off substrate 40, the m-off substrate 41, and the m-off improved substrate 42 are each a circular substrate having an orientation flat at the end in the a-axis direction. Although each of the substrates 40 to 42 is a circular substrate, in FIG. 7(c), they are displayed as distorted ellipses due to the polar coordinate display. More precisely, the portion farther from the origin (the side with the larger off amount) is displayed as stretched. Since the m-off improved substrate 42 has a smaller off-angle distribution than the m-off substrate 41, the outline of the m-off improved substrate 42 is displayed as smaller than the outline of the m-off substrate 41.

[0103] The off-direction and off-amount of the off-angle are shown as positions within the outline of each of the substrates 40 to 42. For each of the substrates 40 to 42, the origin is located outside the outline, and each of the substrates 40 to 42 does not have a location where the off-angle (off-amount) is zero across the entire main surface. Hereinafter, when the substrates 40 to 42 are not particularly distinguished from one another, they may be simply referred to as substrates.

[0104] The off direction at a certain position A on the main surface of the substrate is the direction from position A toward the origin. When considering a line segment B that passes through position A and is parallel to the off direction at position A, the off direction at each position located on line segment B is the same as that at position A (parallel to line segment B). Because the substrate does not have a position where the off angle (off amount) is zero, the off direction does not reverse on line segment B (for example, it does not reverse from the positive a-axis direction to the negative a-axis direction).

[0105] The off-amount at position A is proportional to the distance from the origin to position A. Since the substrate does not have a location where the off-angle (off-amount) is zero, at each position arranged on line segment B, the off-amount changes monotonically from one end of line segment B to the other end in proportion to the distance from one end (for example, increases monotonically from the end of line segment B on the origin side to the end opposite the origin in proportion to the distance from the end on the origin side).

[0106] In the a-off substrate 40, the off-direction at the substrate center (position A as an example) is parallel to the a-axis direction. A line segment (line segment B as an example) that passes through the substrate center and is parallel to the off-direction at the substrate center is referred to as the center line segment 50. At each position on the center line segment 50, the off-direction is the same, that is, parallel to the a-axis direction. The actual measured values ​​of the off-angle in the a-off substrate 40 are indicated by circles. These circles indicate the off-angle at each position on the center line segment 50 within the margin of error. The central circle 60 indicates the substrate center. The off-amount at the substrate center is 0.41°.

[0107] In the m-off substrate 41, the off-direction at the substrate center (position A as an example) is parallel to the m-axis direction. A line segment (line segment B as an example) that passes through the substrate center and is parallel to the off-direction at the substrate center is referred to as the center line segment 51. At each position on the center line segment 51, the off-direction is the same, that is, parallel to the m-axis direction. The measured values ​​of the off-angle in the m-off substrate 41 are indicated by square marks. These square marks indicate the off-angle at each position on the center line segment 51 within the margin of error. The central square mark 61 indicates the substrate center. The off-amount at the substrate center is 0.64°.

[0108] In the m-off improved substrate 42, the off-direction at the substrate center (position A as an example) is parallel to the m-axis direction. A line segment (line segment B as an example) that passes through the substrate center and is parallel to the off-direction at the substrate center is called the center line segment 52. At each position on the center line segment 52, the off-direction is the same, that is, parallel to the m-axis direction. The measured values ​​of the off-angle in the m-off improved substrate 42 are indicated by triangular marks. Among these triangular marks, those aligned along the m-axis direction indicate the off-angle at each position on the center line segment 52 within the margin of error. The central triangular mark 62 indicates the substrate center. The off-amount at the substrate center is 0.44°. For the m-off improved substrate 42, the measured values ​​of the off-angle at positions shifted from the substrate center to the plus and minus sides of the a-axis direction perpendicular to the m-axis direction indicating the center line segment 52 are also indicated.

[0109] 8 is a graph showing the off-amount on the center line segments 50-52 of each of the substrates 40-42 versus the position on the substrate. The horizontal axis is the position on the substrate (Wafer position) in mm, and the vertical axis is the off-amount (|Off-angle|) in degrees. The position on the substrate is expressed with the substrate center as the reference (0), with the side where the off-amount decreases being negative and the side where the off-amount increases being positive. The diameter of each of the substrates 40-42 is 2 inches.

[0110] It can be seen that the off-amount varies monotonically in proportion to the distance from one end to the other end of the center line segment 50-52 of each of the substrates 40-42, that is, varies linearly. It can also be seen that the range of the off-amount (the magnitude of the off-angle distribution) is different for each of the substrates 40-42.

[0111] Since the amount of offset has the characteristic of changing linearly, the amount of offset over the entire center line (on line segment B) may be calculated by fitting actual measurements of the amount of offset at several points.

[0112] In this experimental example, the range of the off-amount of the m-off improved substrate 42 is included in the range of the off-amounts of the a-off substrate 40 and the m-off substrate 41, but the range of the off-amount of the a-off substrate 40 and the range of the off-amount of the m-off substrate 41 are different and have mutually exclusive portions. In other words, by using the substrate 40 having a relatively small off-amount range in combination with the substrate 41 having a relatively large off-amount range, the range of the off-amount can be expanded compared to the case of using only one substrate, for example, only the substrate 40 or only the substrate 41.

[0113] If the misalignment amount is close to 0°, the surface of the grown epitaxial layer will become rough (the morphology will become large). From this viewpoint, it is preferable that the misalignment amount is, for example, 0.1° or more over the entire main surface of the substrate.

[0114] Next, a description will be given of a stack in which epitaxial layers are grown above the substrates 40 to 42. Fig. 9(a) is a schematic plan view showing a growth process of an epitaxial layer, and Fig. 9(b) is a schematic cross-sectional view showing the stack.

[0115] In order to suppress the variation in the growth conditions, the substrates 40 to 42 were placed on the susceptor 310 of the MOVPE apparatus 300, and epitaxial layers were simultaneously grown on the substrates 40 to 42. Trimethylgallium (TMG) gas was used as the Group III organic source gas. Ammonia (NH3) gas was used as the N source gas. Si was used as the n-type impurity, and silane (SiH4) gas was used as the Si source gas.

[0116] The laminate 100 includes a substrate 110 (40, 41, 42) and an epitaxial layer 120. In the laminate 100 fabricated in this experimental example, another epitaxial layer 130 is interposed between the substrate 110 and the epitaxial layer 120. The substrate 110 is made of GaN and has a Si concentration of 1×10 18 cm -3 The other epitaxial layer 130 is made of GaN and has a Si concentration of 2×10 18 cm -3The epitaxial layer 120 is made of GaN and has a Si concentration of 9×10 15 cm -3 and has a thickness of 13 μm.

[0117] In this way, three types of laminate 100 were prepared: laminate 140 in which the substrate 110 is an a-off substrate 40; laminate 141 in which the substrate 110 is an m-off substrate 41; and laminate 142 in which the substrate 110 is an m-off improved substrate 42.

[0118] Next, the results of investigating the relationship between the off angle and the relative yellow intensity for the produced laminates 140 to 142 will be described.

[0119] The PL mapping measurement of the epitaxial layer 120 was performed using LabRAM HR Evolution manufactured by Horiba, Ltd. A He-Cd laser with a wavelength of 325 nm and a power of 1.25 mW was used as the excitation light source. The spot size of the laser was set to a diameter of 5 μm. Therefore, the irradiation intensity was 6.4 × 10 3 Wcm -2 The measurement position was moved at 500 μm intervals to perform PL mapping measurements.

[0120] The relative yellow intensity is the emission intensity Int at the band edge emission peak at 3.4 eV. NBE Yellow emission peak intensity at 2.2 eV Int YL Ratio of Int YL / Int NBE It was calculated as:

[0121] 10(a) is a graph showing the relative yellow intensity of the epitaxial layer 120 on the center line segments 50-52 of each of the stacks 140-142 versus position on the substrate. The horizontal axis is the position on the substrate (wafer position) in mm, and the vertical axis is the relative yellow intensity (Int YL / Int NBE ).

[0122] FIG. 10(b) is a graph showing the relative yellow intensity of the epitaxial layer 120 on the center line segments 50-52 of each of the stacks 140-142 versus the off-angle. The horizontal axis represents the off-angle (|Off-angle|) in degrees, and the vertical axis represents the relative yellow intensity (Int YL / Int NBE ).

[0123] 10(a) and 10(b), the results of the laminate 140 using the a-off substrate 40 are indicated by circles, the results of the laminate 141 using the m-off substrate 41 are indicated by squares, and the results of the laminate 142 using the m-off improved substrate 42 are indicated by triangles. Note that such results are similarly indicated in Figs. 11a and 11b described later.

[0124] 10(a), which shows the relative yellow intensity versus position on the substrate, it can be seen that the relative yellow intensity decreases as the position on the substrate moves toward the side where the off-amount increases for each of the laminates 140 to 142. However, it is difficult to see any characteristics that are common to the laminates 140 to 142.

[0125] The inventors of the present application attempted to show the relative yellow intensity versus the off-amount as shown in Fig. 10(b). As a result, they found that a common characteristic of the laminates 140 to 142 is that if the off-amount is equal, the relative yellow intensity is equal. For example, in all of the laminates 140 to 142, there is a position where the off-amount is 0.4° (see Fig. 8), and it can be seen that the relative yellow intensity at the position of the off-amount of 0.4° is equal, although there is an error.

[0126] The results for stack 140 show the characteristics at the measurement position where the off-direction is the a-axis direction, and the results for stacks 141 and 142 show the characteristics at the measurement position where the off-direction is the m-axis direction. In general, various characteristics of a III-nitride semiconductor may differ between the a-axis direction and the m-axis direction. That is, anisotropy may occur in the characteristics between the a-axis direction and the m-axis direction. Furthermore, the way in which anisotropy occurs may differ for each characteristic. For this reason, even if the off amount is the same at the measurement position where the off-direction is the a-axis direction and the measurement position where the off-direction is the m-axis direction, it is not self-evident that the relative yellow intensity is the same.

[0127] The present inventors have found through this experimental example that the relative yellow intensity of the epitaxial layer 120 does not depend on the off-direction, that is, whether the off-direction is the a-axis direction or the m-axis direction, but is determined depending on the off-amount. In other words, the inventors have found that the off-amount and the relative yellow intensity have a corresponding relationship that is independent of the off-direction.

[0128] The fact that the relative yellow intensity is determined by the off-amount for both the measurement position where the off-direction is the a-axis direction and the measurement position where the off-direction is the m-axis direction indicates that the relative yellow intensity is also determined by the off-amount for a measurement position where the off-direction has both a-axis and m-axis components and has intermediate characteristics between the a-axis and m-axis directions. In other words, the relative yellow intensity is also determined by the off-amount for measurement positions other than the center line segments 50-52 of each laminate 140-142.

[0129] The present inventors have also found that the correspondence relationship has a tendency that as the off amount increases, the relative yellow intensity decreases and the degree of decrease in the relative yellow intensity becomes smaller. The present inventors further found that such a tendency, that is, the relative yellow intensity Int(θ off ) is the off amount θ off The inventors found that the damping constant λ, the critical off amount θ0, the constants A and Int0 can be approximately expressed by the formula (1).

[0130] The approximation curve shown by the solid line in Figure 10(b) is a curve obtained from formula (1). In this example, the damping constant λ is 5.67 ± 0.24 (unit: 1 / °), the critical off amount θ0 is 0.091 (unit: °), the constant A is 0.00827 ± 0.00025 (unit: arbitrary unit), and the constant Int0 is 0.0029 ± 0.00006 (unit: arbitrary unit). The curves in which these parameters λ, A, and Int0 are increased by 50% and decreased by 50%, respectively, are shown by dashed lines.

[0131] In this experimental example, the laminate 100 (140) including the substrate 40 having an off-amount range on the relatively small side and the laminate 100 (141) including the substrate 41 having an off-amount range on the relatively large side are used in combination to widen the range of off-amounts to be measured compared to the case where only one laminate 100, for example, only the laminate 140, or for example, only the laminate 141, is used. This makes it possible to obtain a correspondence relationship with high accuracy for a wide range of off-amounts.

[0132] The correspondence relationship between the off amount and the relative yellow intensity thus obtained can be used for inspecting the crystal quality of the epilayer in a Group III nitride stack, as described in the above embodiments.

[0133] Next, the results of investigating the relationship between the off-angle and the carrier concentration for the fabricated laminates 140 to 142 will be described.

[0134] The carrier concentration of the epitaxial layer 120 was measured by non-contact CV measurement. Here, the "carrier concentration" refers to the concentration of the added n-type impurity, that is, the donor concentration N D From the acceptor concentration N A The net donor concentration N D -N A The non-contact CV measurements were performed using a FAaST-210 from Semilab Semiconductor Physics Laboratory Co. Ltd. In addition, the Si concentration and carbon (C) concentration were also measured by SIMS.

[0135] 11A is a graph showing the carrier concentration of the epitaxial layer 120 of each of the stacks 140 to 142 versus the off-angle. The horizontal axis represents the off-angle (|Off-angle|) in degrees, and the vertical axis represents the off-angle (|Off-angle|) in degrees. 15 cm -3 The concentration is expressed in units of 1. Figure 11(a) also shows the Si concentration, the C concentration, and the acceptor concentration.

[0136] The average Si concentration ([Si]) of the epitaxial layer 120 measured by SIMS was 8.32 × 10 15 cm -3 In addition, the off-dependence of the Si concentration was hardly observed. Therefore, it is possible to determine the carrier concentration N D -N A By subtracting A is estimated.

[0137] The inventors of the present application have determined the relationship between the off amount and the carrier concentration N D -N A The correspondence relationship between the carrier concentration N D -N A As the carrier concentration N D -N A In other words, the degree of increase in the off amount and the acceptor concentration N A The correspondence relationship between the acceptor concentration N A As the acceptor concentration N A The inventors have found that the degree of decrease in the amount of the ion exchange resin tends to be smaller when the amount of the ion exchange resin is large.

[0138] The stacked structures 140 to 142 can be regarded as III-nitride stacked structures in which the correspondence relationship between the off-amount and the acceptor concentration in the epitaxial layer 120 tends to be such that as the off-amount increases, the acceptor concentration decreases and the degree of decrease in the acceptor concentration becomes smaller.

[0139] The present inventors further ASuch a correspondence relationship is expressed as the off amount θ off , damping constant λ, critical off amount θ0, constants B and N A0 Here, the decay constant λ and the critical off amount θ0 are consistent with the decay constant λ and the critical off amount θ0 in the approximation equation (1) for the relative yellow intensity.

number

[0140] The acceptor concentration N A The approximation curve of is a curve obtained from the formula (2). In this example, the damping constant λ is 5.67±0.24 (unit: 1 / °), the critical off amount θ0 is 0.091 (unit: °), and the constant B is 9.21±0.74 (unit: 10 15 cm -3 ), constant N A0 is 0.86±0.09 (unit: 10 15 cm -3 ) The acceptor concentration N A As an example of the upper and lower limits of the acceptor concentration N A The curves for increasing the acceptor concentration N A The carrier concentration (net donor concentration) N D -N A The approximation curve, the lower limit guideline curve, and the upper limit guideline curve are shown.

[0141] Although the C concentration ([C]) appears to decrease slightly with increasing off-state, the acceptor concentration N A In other words, the acceptor concentration N A The main reason for the decrease in N is not the decrease in the C concentration. AThe researchers found that the C activation rate (C / C concentration, hereafter simply referred to as the "C activation rate") decreases as the off-dose increases. In this example, it is estimated that when the off-dose is 0.25°, almost all of the C becomes acceptors, when the off-dose is 0.4°, about 50% of the C becomes acceptors, and when the off-dose is 0.8°, about 10% of the C becomes acceptors.

[0142] The stacked bodies 140 to 142 can be regarded as Group III nitride stacked bodies in which the correspondence relationship between the off amount and the activation rate of C in the epitaxial layer 120 has a tendency that the activation rate of C decreases as the off amount increases.

[0143] The concentration of C mixed into the epitaxial layer 120 can be controlled to be 10 15 cm -3 On the other hand, the Si concentration in the epitaxial layer 120, i.e., the n-type impurity concentration, can be suppressed to the order of 10 15 cm -3 It is preferable to suppress the C concentration to the order of 1 / 10 of the Si concentration. Therefore, in the epilayer 120, the C concentration becomes similar to the Si concentration, and the activation rate of C greatly affects the carrier concentration. For example, if the C concentration is equal to the Si concentration and the activation rate of C is 100%, the donors caused by Si are offset by the acceptors caused by C. Here, the C concentration in the epilayer 120 being similar to the Si concentration is defined as the C concentration being 1 / 10 or more and equal to or less than the Si concentration.

[0144] According to the above findings, even if the C concentration in the epilayer is similar to the Si concentration and it is difficult to reduce the acceptor concentration by further reducing the C concentration, the acceptor concentration can be reduced and the carrier concentration increased by appropriately selecting a large off amount to suppress the C activation rate. In other words, the n-type impurities added to the epilayer can be efficiently used as donors. The technology that can control the C-induced acceptor concentration in this way has been developed for 10 15 cm -3This is particularly effective for precisely controlling low carrier concentrations on the order of 1000 .mu.m or less.

[0145] The activation rate of C is, for example, preferably 50% or less, and more preferably 30% or less. In the example shown in Fig. 11(a), the activation rate of C can be made 50% or less by setting the off amount to about 0.4° or more, and the activation rate of C can be made 30% or less by setting the off amount to about 0.5° or more.

[0146] According to the above findings, by using a substrate with an appropriately large off-axis amount, the n-type impurity concentration can be increased to 10 15 cm -3 on the order of 1×10 16 cm -3 It is possible to obtain a Group III nitride stack having an epilayer in which the C concentration is 1 / 10 or more of the n-type impurity concentration and is equal to or less than the n-type impurity concentration, and the C activation rate is preferably 50% or less, more preferably 30% or less.

[0147] Next, the results of investigating the relationship between the relative yellow intensity and the acceptor concentration for the produced laminates 140 to 142 will be described.

[0148] FIG. 11(b) is a graph showing the acceptor concentration of the epitaxial layer 120 of each of the stacks 140 to 142 versus the relative yellow intensity. The horizontal axis is the relative yellow intensity (Int YL / Int NBE ) and the vertical axis is 10 15 cm -3 The concentration is expressed in units.

[0149] By associating the correspondence relationship between the off-amount and the relative yellow intensity described with reference to Figure 10(b) with the correspondence relationship between the off-amount and the acceptor concentration described with reference to Figure 11(a) via the off-amount, it is possible to obtain the correspondence relationship between the relative yellow intensity and the acceptor concentration as shown in Figure 11(b).

[0150] For the epilayer 120, the relative yellow intensity is expressed by the off amount as shown in formula (1), and the acceptor concentration is expressed by the off amount as shown in formula (2), so that the acceptor concentration changes in proportion to the relative yellow intensity, as shown in Fig. 11(b). In other words, the stacks 140 to 142 can be regarded as Group III nitride stacks in which the correspondence relationship between the relative yellow intensity and the acceptor concentration in the epilayer 120 tends to be proportional to the acceptor concentration.

[0151] If the correspondence between the relative yellow intensity and the acceptor concentration as shown in FIG. 11(b) is obtained in advance, the acceptor concentration can be estimated without performing CV measurement by obtaining the relative yellow intensity by PL mapping measurement. This technique for obtaining the acceptor concentration by PL mapping measurement is very useful because it can be performed non-destructively and easily. Note that the carrier concentration may be obtained using a similar concept.

[0152] <Other embodiments> Next, as an example of another embodiment, a III-nitride stack with a physical quantity map will be described, which is an aspect in which the above-mentioned III-nitride stack is provided in combination with a physical quantity map.

[0153] 12 is a schematic diagram showing a III-nitride stack with a physical quantity map (hereinafter, sometimes referred to as a stack with a map) 400. The stack with a map 400 has a stack 410 and a physical quantity map 420. The stack 410 has a substrate 411 and an epitaxial layer 412. Here, the expression "with" a map includes cases where (1) a recording medium storing information indicating the contents of the map or a printed matter on which the map is printed is attached to a tray or enclosed item storing the stack 410, and (2) information indicating the contents of the map is provided so as to be downloadable via the Internet, a dedicated line, or the like.

[0154] The physical quantity map 420 is a map that displays the physical quantity of the epitaxial layer 412 of the stack 410, and displays the outline of the stack 410, the off amount within the outline, and the physical quantity within the outline. The physical quantity is, for example, the relative yellow intensity, or the acceptor concentration, or the activation rate of C. The physical quantity map 420 shown in FIG. 12 is an example of a display of the relative yellow intensity, and areas with high relative yellow intensity are displayed brightly.

[0155] Within the main surface of substrate 411, positions where the off-amount is constant are distributed along concentric circular arcs or concentric elliptical arcs (see FIG. 7(c)). Note that the ellipse may include a circle in the case where the two foci are coincident. Since the relative yellow intensity is determined according to the off-amount, positions where the relative yellow intensity is constant are distributed along concentric circular arcs or concentric elliptical arcs on epilayer 412. In other words, on epilayer 412, positions where the relative yellow intensity exhibits a certain constant value are distributed along a circular arc or an elliptical arc, and positions where the relative yellow intensity exhibits another constant value different from the certain value are distributed along another circular arc concentric with the certain arc, or another elliptical arc concentric with the certain elliptical arc.

[0156] Similarly, the acceptor concentration and the activation rate of C are each determined according to the off amount, so that certain positions are distributed along concentric circular arcs or concentric elliptical arcs on the epilayer 412. That is, on the epilayer 412, positions where the acceptor concentration shows a certain constant value are distributed along a circular arc or an elliptical arc, and positions where the acceptor concentration shows another constant value different from the certain value are distributed along another circular arc concentric with the certain arc, or another elliptical arc concentric with the certain elliptical arc. Also, on the epilayer 412, positions where the activation rate of C shows a certain constant value are distributed along a circular arc or an elliptical arc, and positions where the activation rate of C shows another constant value different from the certain value are distributed along another circular arc concentric with the certain arc, or another elliptical arc concentric with the certain elliptical arc.

[0157] When physical quantities determined according to the off-amount measured over the entire surface of the epilayer 412 are displayed on the physical quantity map 420, a concentric circular or concentric elliptical pattern (more specifically, a concentric circular or concentric elliptical pattern with its center located outside the stack 410) is observed for a normally grown epilayer 412. Therefore, by using the physical quantity map 420, the crystal quality over the entire surface of the epilayer 412 can be grasped at a glance, and by providing the stack 410 in combination with the physical quantity map 420, the quality of the stack 410 can be effectively guaranteed.

[0158] Although the present invention has been described above with reference to the embodiment and modified examples, the present invention is not limited to these. For example, it will be obvious to those skilled in the art that various modifications, improvements, combinations, etc. are possible.

[0159] <Preferred embodiment of the present invention> Preferred embodiments of the present invention will now be described by way of example.

[0160] (Appendix 1) Providing a first III-nitride stack (at least one) having a first III-nitride substrate and a first III-nitride epitaxial layer formed (by metal-organic vapor phase epitaxy) over a primary surface of the first III-nitride substrate; performing photoluminescence mapping measurement for a plurality of measurement positions of the first III-nitride epitaxial layer having different magnitudes of off-angles (off amounts) between a normal direction of a main surface of the first III-nitride substrate and a c-axis direction, and obtaining a relative yellow intensity, which is a ratio of a yellow emission intensity to a band edge emission intensity, and obtaining a correspondence relationship between the magnitude of the off-angle and the relative yellow intensity; The present invention relates to a method for manufacturing, inspecting and evaluating a Group III nitride stack having the above structure, and a method for manufacturing a semiconductor device.

[0161] (Appendix 2) moreover, providing a second III-nitride stack having a second III-nitride substrate and a second III-nitride epitaxial layer formed (by metal-organic vapor phase epitaxy) over a primary surface of the second III-nitride substrate; performing a photoluminescence mapping measurement for an inspection position of the second III-nitride epitaxial layer where the magnitude of the off-angle between the normal direction of the main surface of the second III-nitride substrate and the c-axis direction is a first off-angle, and acquiring a relative yellow emission intensity which is a ratio of a yellow emission intensity to a band edge emission intensity; comparing a relative yellow intensity obtained from a photoluminescence mapping measurement for the test location with a relative yellow intensity obtained from the correspondence relationship for a magnitude of the first off-angle; 2. The method for producing a Group III nitride stack according to claim 1, comprising:

[0162] (Appendix 3) 3. The method for producing a Group III nitride stack according to claim 1 or 2, wherein a plurality of Group III nitride stacks are used as the first Group III nitride stack.

[0163] (Appendix 4) A plurality of Group III nitride stacks having different ranges of off-angles are used as the first Group III nitride stack. 4. A method for producing a Group III nitride laminate according to any one of claims 1 to 3.

[0164] (Appendix 5) As the first III-nitride stack, a plurality of III-nitride stacks are used, the ranges of the magnitude of the off-angle being different on a line segment passing through a center of the first III-nitride substrate and parallel to the orientation (off-direction) of the off-angle at the center. 5. A method for producing a Group III nitride laminate according to any one of claims 1 to 4.

[0165] (Appendix 6) a plurality of Group III nitride stacks having different off-angle orientations at the center of the first Group III nitride substrate are used as the first Group III nitride stack; 6. A method for producing a Group III nitride laminate according to any one of claims 1 to 5.

[0166] (Appendix 7) providing the first III-nitride stack includes simultaneously growing III-nitride epitaxial layers of the plurality of III-nitride stacks; 7. A method for producing a Group III nitride laminate according to any one of claims 3 to 6.

[0167] (Appendix 8) Preparing a correspondence relationship between the magnitude of the off-angle and the relative yellow intensity; preparing a III-nitride stack having a III-nitride substrate and a III-nitride epitaxial layer formed (by metal-organic vapor phase epitaxy) above a primary surface of the III-nitride substrate; performing a photoluminescence mapping measurement for an inspection position where the magnitude of an off-angle of the III-nitride epitaxial layer between a normal direction of a main surface of the III-nitride substrate and a c-axis direction is a first off-angle, and acquiring a relative yellow emission intensity which is a ratio of a yellow emission intensity to a band edge emission intensity; comparing a relative yellow intensity obtained from a photoluminescence mapping measurement for the test location with a relative yellow intensity obtained from the correspondence relationship for a magnitude of the first off-angle; The present invention relates to a method for manufacturing, inspecting and evaluating a Group III nitride stack having the above structure, and a method for manufacturing a semiconductor device.

[0168] (Appendix 9) The correspondence relationship has a tendency that as the off-angle increases, the relative yellow intensity decreases and the degree of decrease in the relative yellow intensity becomes smaller. A method for manufacturing a semiconductor device according to any one of claims 1 to 8.

[0169] (Appendix 10) The correspondence relationship is such that the magnitude of the off angle is θ off and the relative yellow intensity is expressed as Int(θ off ), the decay constant λ of the exponential function, the magnitude θ0 of the critical off-angle at which the argument of the exponential function is zero, the constant A by which the exponential function is multiplied, and the constant Int0 by which the exponential function is added are used to obtain This is approximately expressed by the formula TIFF0007606710000003.tif12170. 10. A method for producing a Group III nitride laminate according to any one of claims 1 to 9.

[0170] (Appendix 11) In the above correspondence relationship, the relative yellow intensity does not depend on the orientation of the off-angle (whether the orientation of the off-angle is the a-axis direction or the m-axis direction). 11. A method for producing a Group III nitride laminate according to any one of claims 1 to 10.

[0171] (Appendix 12) Preparing a correspondence relationship between the magnitude of the off-angle and the relative yellow intensity; preparing a III-nitride stack having a III-nitride substrate and a III-nitride epitaxial layer formed (by metal-organic vapor phase epitaxy) above a primary surface of the III-nitride substrate; performing at least one of capacitance-voltage measurement, secondary ion mass spectrometry measurement, and deep level transient spectroscopy measurement at a plurality of measurement positions of the III-nitride stack having different off-angles between a normal direction of a main surface of the III-nitride substrate and a c-axis direction, and acquiring a correspondence relationship between the measurement results and the off-angle; A step of correlating the relationship between the off-angle and the measurement result with a relationship between the off-angle and a relative yellow intensity via the off-angle; The present invention relates to a method for manufacturing, inspecting and evaluating a Group III nitride stack having the above structure, and a method for manufacturing a semiconductor device.

[0172] (Appendix 13) preparing a first correspondence relationship between the magnitude of the off-angle and the relative yellow intensity; preparing a second correspondence relationship between the magnitude of the off-angle and a physical quantity that can be obtained by at least one of capacitance-voltage measurement, secondary ion mass spectrometry measurement, and deep level transient spectroscopy measurement; acquiring a third correspondence relationship, which is a correspondence relationship between a relative yellow intensity and the physical quantity, by correlating the first correspondence relationship with the second correspondence relationship via a magnitude of an off-angle; preparing a III-nitride stack having a III-nitride substrate and a III-nitride epitaxial layer formed above a primary surface of the III-nitride substrate; performing a photoluminescence mapping measurement for an inspection position defined in the III-nitride epitaxial layer to obtain a relative yellow intensity, which is a ratio of a yellow emission intensity to a band edge emission intensity; inferring the physical quantity at the test location based on a relative yellow intensity obtained from a photoluminescence mapping measurement for the test location and the third correspondence relationship; The present invention relates to a method for manufacturing, inspecting and evaluating a Group III nitride stack having the above structure, and a method for manufacturing a semiconductor device.

[0173] (Appendix 14) preparing a correspondence between the relative yellow intensity and a physical quantity that can be obtained by at least one of a capacitance-voltage measurement, a secondary ion mass spectrometry measurement, and a deep level transient spectroscopy measurement; preparing a III-nitride stack having a III-nitride substrate and a III-nitride epitaxial layer formed above a primary surface of the III-nitride substrate; performing a photoluminescence mapping measurement for an inspection position defined in the III-nitride epitaxial layer to obtain a relative yellow intensity, which is a ratio of a yellow emission intensity to a band edge emission intensity; inferring the physical quantity at the test location based on a relative yellow intensity obtained from a photoluminescence mapping measurement for the test location and the correspondence; The present invention relates to a method for manufacturing, inspecting and evaluating a Group III nitride stack having the above structure, and a method for manufacturing a semiconductor device.

[0174] (Appendix 15) A Group III nitride laminate comprising a Group III nitride substrate and a Group III nitride epitaxial layer formed (by metal-organic chemical vapor deposition) above a primary surface of the Group III nitride substrate, Regarding the relative yellow intensity, which is the ratio of the yellow emission intensity of photoluminescence to the band edge emission intensity in the III nitride epitaxial layer, a correspondence relationship between the magnitude of the off-angle formed between the normal direction of the primary surface of the III nitride substrate and the c-axis direction and the relative yellow intensity has a tendency that as the magnitude of the off-angle increases, the relative yellow intensity decreases and the degree of decrease in the relative yellow intensity becomes smaller; III-nitride stacks.

[0175] (Appendix 16) In the correspondence relationship between the magnitude of the off-angle and the relative yellow intensity, the relative yellow intensity does not depend on the orientation of the off-angle. 16. The III-nitride stack according to claim 15.

[0176] (Appendix 17) The correspondence relationship between the magnitude of the off-angle and the relative yellow intensity is as follows: off and the relative yellow intensity is expressed as Int(θ off ), the decay constant λ of the exponential function, the magnitude θ0 of the critical off-angle at which the argument of the exponential function is zero, the constant A by which the exponential function is multiplied, and the constant Int0 by which the exponential function is added are used to obtain This is approximately expressed by the formula TIFF0007606710000004.tif12170. 17. The III-nitride stack according to claim 15 or 16.

[0177] (Appendix 18) the measured values ​​of the relative yellow intensity are distributed within a range that is equal to or greater than a lower limit that is determined by substituting into the formula a value obtained by reducing by 50% each of the attenuation constant λ, the constant A, and the constant Int0, which are determined so as to approximately represent a correspondence relationship between the magnitude of the off-angle and the relative yellow intensity, and is equal to or less than an upper limit that is determined by substituting into the formula a value obtained by increasing by 50% each of the attenuation constant λ, the constant A, and the constant Int0, which are determined so as to approximately represent the correspondence relationship, 18. The III-nitride stack according to claim 17.

[0178] (Appendix 19) the III-nitride epitaxial layer is doped with an n-type impurity; Regarding the acceptor concentration of the Group III nitride epitaxial layer, The correspondence relationship between the magnitude of the off angle and the acceptor concentration has a tendency that as the magnitude of the off angle increases, the acceptor concentration decreases and the degree of decrease in the acceptor concentration becomes smaller. 19. The Group III nitride stack according to any one of claims 15 to 18.

[0179] (Appendix 20) The correspondence relationship between the magnitude of the off-angle and the acceptor concentration is as follows: off and the acceptor concentration is N A (θ off ), the attenuation constant λ, the magnitude of the critical off angle θ0, a constant B multiplied by the exponential function, and a constant N added to the exponential function A0 Using This is approximately expressed by the formula TIFF0007606710000005.tif11170. 20. The III-nitride stack of claim 19.

[0180] (Appendix 21) The correspondence relationship between the relative yellow intensity and the acceptor concentration has a tendency that the acceptor concentration is proportional to the relative yellow intensity. 21. The III-nitride stack according to claim 19 or 20.

[0181] (Appendix 22) In the III-nitride epitaxial layer, the concentration of the n-type impurity is 1×10 16 cm -3 and the carbon concentration is 1 / 10 or more of the n-type impurity concentration and is equal to or less than the n-type impurity concentration, Regarding the carbon activation ratio, which is the ratio of the acceptor concentration to the carbon concentration in the Group III nitride epitaxial layer, The correspondence relationship between the off angle and the carbon activation rate has a tendency that the carbon activation rate decreases as the off angle increases. 22. The Group III nitride stack according to any one of claims 15 to 21.

[0182] (Appendix 23) A Group III nitride laminate comprising a Group III nitride substrate and a Group III nitride epitaxial layer formed (by metal-organic chemical vapor deposition) above a primary surface of the Group III nitride substrate, In the III-nitride epitaxial layer, the concentration of n-type impurities is 1×10 16 cm -3 and the carbon concentration is 1 / 10 or more of the n-type impurity concentration and is equal to or less than the n-type impurity concentration, Regarding the carbon activation ratio, which is the ratio of the acceptor concentration to the carbon concentration in the Group III nitride epitaxial layer, a correspondence relationship between an off angle formed by a normal direction of a primary surface of the III nitride substrate and a c-axis direction and an activation rate of carbon has a tendency that the activation rate of carbon decreases as the magnitude of the off angle increases; III-nitride stacks.

[0183] (Appendix 24) A Group III nitride laminate comprising a Group III nitride substrate and a Group III nitride epitaxial layer formed (by metal-organic chemical vapor deposition) above a primary surface of the Group III nitride substrate, In the III-nitride epitaxial layer, the concentration of n-type impurities is 1×10 16 cm -3and the carbon concentration is 1 / 10 or more of the n-type impurity concentration and is equal to or less than the n-type impurity concentration, In the III nitride epitaxial layer, a carbon activation rate, which is a ratio of an acceptor concentration to a carbon concentration, is preferably 50% or less, and more preferably 30% or less. III-nitride stacks.

[0184] (Appendix 25) A Group III nitride laminate comprising a Group III nitride substrate and a Group III nitride epitaxial layer formed (by metal-organic chemical vapor deposition) above a primary surface of the Group III nitride substrate, Regarding the relative yellow intensity, which is the ratio of the yellow emission intensity of photoluminescence to the band edge emission intensity in the III nitride epitaxial layer, On the III-nitride epitaxial layer, positions at which the relative yellow intensity exhibits a first constant value are distributed along a first circular arc or a first elliptical arc, and positions at which the relative yellow intensity exhibits a second constant value different from the first constant value are distributed along a second circular arc concentric with the first circular arc or a second elliptical arc concentric with the first elliptical arc. III-nitride stacks.

[0185] (Appendix 26) the III-nitride epitaxial layer is doped with an n-type impurity; Regarding the acceptor concentration of the Group III nitride epitaxial layer, on the III-nitride epitaxial layer, positions at which the acceptor concentration exhibits a third constant value are distributed along a third arc (concentric with the first arc) or a third elliptical arc (concentric with the first elliptical arc), and positions at which the acceptor concentration exhibits a fourth constant value different from the third constant value are distributed along a fourth arc concentric with the third arc or a fourth elliptical arc concentric with the third elliptical arc. 26. The III-nitride stack of claim 25.

[0186] (Appendix 27) In the III-nitride epitaxial layer, the concentration of the n-type impurity is 1×10 16 cm -3 and the carbon concentration is 1 / 10 or more of the n-type impurity concentration and is equal to or less than the n-type impurity concentration, Regarding the carbon activation rate, which is the ratio of the acceptor concentration to the carbon concentration in the Group III nitride epitaxial layer, On the III-nitride epitaxial layer, positions at which the carbon activation rate exhibits a fifth constant value are distributed along a fifth circular arc (concentric with the first circular arc) or a fifth elliptical arc (concentric with the first elliptical arc), and positions at which the carbon activation rate exhibits a sixth constant value different from the fifth constant value are distributed along a sixth circular arc concentric with the fifth arc or a sixth elliptical arc concentric with the fifth elliptical arc. 27. The III-nitride stack of claim 26.

[0187] (Appendix 28) A Group III nitride laminate comprising a Group III nitride substrate and a Group III nitride epitaxial layer formed (by metal-organic chemical vapor deposition) above a primary surface of the Group III nitride substrate, In the III-nitride epitaxial layer, the concentration of the n-type impurity is 1×10 16 cm -3 and the carbon concentration is 1 / 10 or more of the n-type impurity concentration and is equal to or less than the n-type impurity concentration, Regarding the carbon activation ratio, which is the ratio of the acceptor concentration to the carbon concentration in the Group III nitride epitaxial layer, On the III-nitride epitaxial layer, positions at which the carbon activation rate exhibits a first constant value are distributed along a first circular arc or a first elliptical arc, and positions at which the carbon activation rate exhibits a second constant value different from the first constant value are distributed along a second circular arc concentric with the first circular arc or a second elliptical arc concentric with the first elliptical arc. III-nitride stacks.

[0188] (Appendix 29) The maximum defect density in the primary surface of the III-nitride substrate is 5×10 6 cm -2 or less, more preferably 10 times the average defect density or less, and even more preferably 10 times the minimum defect density or less. 29. The Group III nitride stack according to any one of claims 15 to 28.

[0189] (Appendix 30) In the III-nitride substrate, at each position arranged on a line segment B that passes through a position A defined on a primary surface of the III-nitride substrate and is parallel to the orientation of the off-angle at the position A, the orientation of the off-angle is the same as that at the position A, and the magnitude of the off-angle changes monotonically from one end of the line segment B to the other end in proportion to the distance from the one end. 30. The Group III nitride stack according to any one of claims 15 to 29.

[0190] (Appendix 31) moreover, a physical quantity map displaying a contour of the III-nitride stack, a magnitude of the off-angle within the contour, and a physical quantity of the III-nitride epitaxial layer within the contour; A group III nitride stack with a physical quantity map having 31. The Group III nitride stack according to any one of claims 15 to 30.

[0191] (Appendix 32) The III-nitride substrate has no location where the magnitude of the off-angle is zero across the entire main surface. 32. The Group III nitride stack according to any one of claims 15 to 31.

[0192] (Appendix 33) the magnitude of the off angle is 0.1° or more over the entire area of ​​the main surface of the Group III nitride substrate; 33. The Group III nitride stack according to any one of claims 15 to 32.

[0193] (Appendix 34) the III-nitride substrate and the III-nitride epitaxial layer have n-type conductivity; 34. The Group III nitride stack according to any one of claims 15 to 33.

[0194] (Appendix 35) The III-nitride epitaxial layer is doped with n-type impurities at a concentration of 3×10 15 cm -3 5×10 or more 16 cm -3 It is added at the following concentrations: 35. The Group III nitride stack according to any one of claims 15 to 34. [Explanation of symbols]

[0195] 100 Reference stack 200 Inspection stack 110, 210 board 111, 211 Main surface 120, 220 epilayer 121, 221 (epilayer) surface 122 Measurement position 222 Inspection position 40 a-off board 41 m-off board 42 m-off improved board 400 Mapped Stack 410 Laminate 420 Physical Quantity Map

Claims

1. A gallium nitride substrate which is a c-plane substrate, 5×10 in the main surface of the gallium nitride substrate ６ cm －２ and having a maximum defect density of With respect to an off-angle, which is an angle between a normal direction of the main surface of the gallium nitride substrate and a c-axis direction of a gallium nitride crystal constituting the gallium nitride substrate, at each position located on a line segment B that passes through a position A defined on the main surface of the gallium nitride substrate and is parallel to the orientation of the off-angle at the position A, the orientation of the off-angle is the same as that at the position A, and the magnitude of the off-angle changes monotonically from one end of the line segment B to the other end in proportion to the distance from the one end. Gallium nitride substrate.

2. The gallium nitride substrate according to claim 1 , wherein the line segment B on the primary surface has a length of 2 inches.

3. The gallium nitride substrate according to claim 1 , wherein the maximum defect density in the primary surface is not more than 10 times the average defect density.

4. 4. The gallium nitride substrate according to claim 1, wherein the magnitude of the off angle is 0.1° or more over the entire area of ​​the main surface.

5. 5. The gallium nitride substrate according to claim 1, wherein the orientation of the off-angle at the center of the gallium nitride substrate is parallel to the a-axis direction.

6. 5. The gallium nitride substrate according to claim 1, wherein the orientation of the off-angle at the center of the gallium nitride substrate is parallel to the m-axis direction.

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