JP2020019675A - Nitride crystal member, manufacturing method thereof, laminated nitride crystal substrate and manufacturing method thereof - Google Patents

Abstract

To provide a nitride crystal member manufacturable without a grinding step and a polishing step, and having a ground surface capable of epitaxially growing a nitride crystal layer.SOLUTION: A nitride crystal member is constituted of a crystal of a group III nitride, and has a ground surface for growing a nitride crystal layer. The ground surface is a surface capable of epitaxially growing the nitride crystal layer so that surface roughness expressed by a peak-to-valley value PV becomes 0.01 μm or more and 10 μm or less, and that a dislocation density in the nitride crystal layer becomes double or less of a dislocation density in the nitride crystal member.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a nitride crystal member and a method for manufacturing the same, and a laminated nitride crystal substrate and a method for manufacturing the same.

  BACKGROUND ART Group III nitrides (hereinafter also referred to as nitrides) such as gallium nitride (GaN) are used as materials for manufacturing semiconductor devices such as light-emitting elements and transistors. 2. Description of the Related Art A technique for epitaxially growing a nitride crystal layer on a member made of a nitride crystal has attracted attention because a high-quality nitride crystal layer can be obtained. For example, Non-Patent Document 1 describes the advantage of epitaxial growth on a GaN substrate.

Yuichi Oshima and five others, “GaN substrate by void formation peeling method”, Hitachi Cable, 26 (2007-1), p. 31-36

  For example, in a GaN substrate, a main surface used as a ground for epitaxial growth is finished to a flat mirror surface by a grinding process and a polishing process. However, in order to obtain such a mirror surface, a grinding step and a polishing step are required, which is very troublesome.

  An object of the present invention is to provide a nitride crystal member and a laminated nitride crystal substrate which can be manufactured without performing a grinding step and a polishing step and have a base surface on which a nitride crystal layer can be epitaxially grown. It is.

According to one aspect of the present invention, there is provided a nitride crystal member including a group III nitride crystal and having a lower ground surface for growing a nitride crystal layer,
The base surface has a surface roughness PV expressed by a peak-to-valley value of 0.01 μm or more and 10 μm or less, and a dislocation density in the nitride crystal layer is twice or less of a dislocation density in the nitride crystal member. Is a surface on which the nitride crystal layer can be epitaxially grown.
A nitride crystal member is provided.

According to another aspect of the present invention,
Preparing a nitride crystal member composed of a group III nitride crystal and having an altered layer on a surface to be a lower ground for growth of a nitride crystal layer,
Etching said surface,
Removing the group III element generated due to the etching such that adhesion to the base surface is suppressed;
A method for producing a nitride crystal member comprising:
By etching the surface and removing the group III element generated due to the etching so that the adhesion to the base surface is suppressed,
The surface has a surface roughness PV represented by a peak-to-valley value of 0.01 μm or more and 10 μm or less, and the dislocation density in the nitride crystal layer is twice or less the dislocation density in the nitride crystal member. As described above, the nitride crystal layer is used as the base surface on which epitaxial growth can be performed,
A method for manufacturing a nitride crystal member is provided.

According to yet another aspect of the present invention,
A nitride crystal substrate composed of a group III nitride crystal and having a first main surface;
A first nitride crystal layer composed of a group III nitride crystal and epitaxially grown on the first main surface and having a second main surface;
A laminated nitride crystal substrate comprising:
The second main surface of the first nitride crystal layer has higher flatness than the first main surface of the nitride crystal substrate, and is a lower ground surface for growing the second nitride crystal layer. ,
A laminated nitride crystal substrate is provided.

According to yet another aspect of the present invention,
Preparing an as-sliced nitride crystal substrate composed of a group III nitride crystal and having an altered layer on a surface to be a first main surface for growing a first nitride crystal layer;
Etching said surface,
Removing a group III element generated due to the etching such that adhesion to the first main surface is suppressed;
Epitaxially growing a first nitride crystal layer composed of a group III nitride crystal and having a second main surface having a higher flatness than the first main surface on the first main surface;
A method for producing a laminated nitride crystal substrate comprising:
By etching the surface and removing a Group III element generated due to the etching such that adhesion to the first main surface is suppressed,
The surface has a surface roughness PV represented by a peak-to-valley value of 0.01 μm or more and 10 μm or less, and the dislocation density in the first nitride crystal layer is twice or less the dislocation density in the nitride crystal substrate. The first main surface on which the first nitride crystal layer can be epitaxially grown,
The second main surface is used as a ground for growing a second nitride crystal layer,
The second nitride crystal layer can be epitaxially grown such that the dislocation density in the second nitride crystal layer is equal to or less than twice the dislocation density in the nitride crystal substrate.
A method for manufacturing a laminated nitride crystal substrate is provided.

  A nitride crystal member and a laminated nitride crystal substrate which can be manufactured without performing a grinding step and a polishing step and have a base surface on which a nitride crystal layer can be epitaxially grown are provided.

FIG. 1A is a flowchart schematically showing a method for manufacturing a nitride crystal member (nitride crystal substrate or nitride crystal growth) according to the first or second embodiment of the present invention, and FIG. 4) is a flowchart schematically showing a method for manufacturing a laminated nitride crystal substrate according to a modification of the first embodiment. 2A to 2C are schematic cross-sectional views illustrating a method for manufacturing the nitride crystal substrate according to the first embodiment, and FIG. FIG. 4 is a schematic cross-sectional view showing a state in which a material crystal layer is grown. FIGS. 3A and 3B are schematic diagrams illustrating an example of a gas etching apparatus. FIG. 4A is a schematic cross-sectional view illustrating a method for manufacturing a laminated nitride crystal substrate according to a modification of the first embodiment, and FIG. FIG. 3 is a schematic sectional view showing a state where a crystal layer is grown. 5A to 5C are schematic cross-sectional views illustrating a method for manufacturing a nitride crystal growth according to the second embodiment. FIG. 5D is a view on a lower ground of the nitride crystal growth. FIG. 3 is a schematic sectional view showing a state in which a nitride crystal layer is grown. FIG. 6 is a 2PPL image of a GaN layer surface of a sample having an etching depth of 10 μm in an experimental example. FIG. 7 is a 2PPL image of a GaN layer surface of a sample having an etching depth of 35 μm in an experimental example. FIG. 8 is a 2PPL image of a GaN layer surface of a sample having an etching depth of 35 μm from which Ga-containing particles have been removed in an experimental example. FIGS. 9A to 9E are 2PPL images of a sample having an etching depth of 35 μm from which Ga-containing particles have been removed in the experimental example, observed at different depths. FIGS. 10A and 10B are obtained by optical microscopic observation of cross sections of a sample having an etching depth of 35 μm and a sample having an etching depth of 50 μm from which Ga-containing particles have been removed in the experimental example, respectively. It is a fluorescent image. FIG. 11 is a perspective view showing the surface of an as-sliced substrate that has not been etched in the experimental example. FIG. 12 is a perspective view showing a surface of a base substrate which has been etched so as to have a surface roughness PV of about 1 μm in an experimental example. FIG. 13A is a photograph showing the entire GaN layer grown by the HVPE method in the experimental example, and FIG. 13B is a differential interference image obtained by observing the surface of the GaN layer by an optical microscope. It is. FIG. 14A is a photograph showing the entire GaN layer grown by the MOVPE method in the experimental example, and FIG. 14B is a differential interference image obtained by observing the surface of the GaN layer by an optical microscope. It is.

  A nitride crystal member 200 (hereinafter, also referred to as member 200) and a method for manufacturing the same according to an embodiment of the present invention will be described. FIG. 2C and FIG. 5C are schematic cross-sectional views each showing the member 200. The member 200 is a member made of a single crystal of a group III nitride, and has a lower ground surface 201 for growing a nitride crystal layer 300 (hereinafter, also referred to as a crystal layer 300). Gallium nitride (GaN) is exemplified as the group III nitride constituting the member 200. Here, the group III nitride is also referred to as a nitride. FIGS. 2D and 5D are schematic cross-sectional views each showing a state in which the crystal layer 300 is grown on the lower ground surface 201 of the member 200.

  The lower ground surface 201 has a surface roughness represented by a peak-to-valley value (hereinafter, also referred to as a surface roughness PV) of 0.01 μm or more and 10 μm or less, and the dislocation density in the crystal layer 300 is smaller than the dislocation density in the member 200. It is configured as a surface on which the crystal layer 300 can be epitaxially grown so as to be twice or less. Here, the surface roughness PV refers to the surface roughness PV measured on a two-dimensional area of 0.14 mm × 0.11 mm by an optical surface texture measuring device using a laser interferometer.

  In the prior art, a substrate whose base surface is polished to a flat mirror surface is used as a nitride crystal member having a lower ground surface for growth of a nitride crystal layer. Otherwise, it has been considered that the nitride crystal layer does not grow well epitaxially. In contrast, the member 200 of the present embodiment can improve the crystal layer 300 even on the base surface 201 which is rougher than the base surface polished to a mirror surface (for example, the surface roughness PV is 0.01 μm or more). It has the feature that it can be epitaxially grown.

  As described below, the lower ground surface 201 of the member 200 can be formed by etching. In the manufacturing process of the member 200 of the present embodiment, the grinding step and the polishing step required to form the lower surface of the mirror surface need not be performed, so that the number of steps can be reduced. In this way, it is possible to avoid occurrence of problems such as cracks.

  By setting the surface roughness PV of the lower ground surface 201 to 10 μm or less, it is possible to suppress a large increase in dislocation density in the crystal layer 300 due to the occurrence of dislocations on the base surface 201. Thereby, the crystal layer 300 can be epitaxially grown so as to have a dislocation density suppressed to twice or less the dislocation density of the member 200, that is, to maintain a dislocation density equivalent to that of the member 200.

  In order to make the surface of the crystal layer 300 grown on the lower ground 201 nearly flat (with a small growth thickness) quickly, the surface roughness PV of the base surface 201 is preferably small. From such a viewpoint, the surface roughness PV of the base surface 201 is preferably 5 μm or less, more preferably 2 μm or less, further preferably 1.5 μm or less, still more preferably 1 μm or less, particularly preferably 0.9 μm or less, More preferably, the thickness is 0.8 μm or less, further preferably 0.7 μm or less, still more preferably 0.6 μm or less, particularly preferably 0.5 μm or less.

  When a semiconductor element is formed on the member 200, a crystal layer 300 having a thickness of, for example, about 2 μm is formed on the lower ground 201 of the member 200 as a base layer of an operation layer (for example, a multiple quantum well layer of a light emitting diode). You. Considering an example in which the (maximum) thickness of the crystal layer 300 having a thickness slightly larger than 2 μm is to bury the irregularities of the underlying surface 201 to obtain a flat surface, the surface roughness PV of the underlying surface 201 is The thickness is preferably 2 μm or less so as not to exceed the (maximum) thickness of the crystal layer 300 to be grown, and 1 μm or less so as to be 1/2 or less of the (maximum) thickness of the crystal layer 300 to be grown. Is more preferable.

  In the case where the flatness improving layer 220 is formed on the member 200 as in a modified example of the first embodiment described later, compared with the case where the crystal layer 300 is grown directly on the base surface 201, The surface roughness PV of the underlying surface 201 may be large, and the surface roughness PV of the underlying surface 201 may be 10 μm or less. In this case, similarly, in order to make the surface of the flatness improving layer 220 nearly flat (with a small growth thickness) quickly, it is preferable to reduce the surface roughness PV of the base surface 201.

  As will be described in detail in an experimental example described later, the surface roughness PV of the underlying surface 201 can be controlled by the depth of etching performed to obtain the underlying surface 201. As the etching depth increases, the etching depth increases. The surface roughness PV of the lower ground 201 can be reduced. However, it is preferable that the etching time does not become too long. From such a viewpoint, the surface roughness PV of the base surface 201 is preferably 0.02 μm or more, more preferably 0.05 μm or more, further preferably 0.1 μm or more, further preferably 0.2 μm or more, and still more preferably 0.3 μm or more, more preferably 0.4 μm or more.

In order to improve the quality of the crystal layer 300 epitaxially grown on the lower ground 201, the member 200 preferably has an average dislocation density of less than 1 × 10 ⁷ / cm ² . Further, in order to improve the in-plane uniformity of the quality of crystal layer 300, member 200 preferably does not include a dislocation concentrated region having a dislocation density of 1 × 10 ⁷ / cm ² or more. Here, the dislocation density is evaluated by emission intensity mapping near the band edge of GaN by two-photon excitation photoluminescence (hereinafter abbreviated as 2PPL). Since the dislocation defect is a non-radiative recombination center, the emission intensity is weakened around the dislocation defect, and the dislocation density is evaluated using the fact that the dislocation defect is observed as a dark spot in the emission intensity mapping image. An image is taken in an observation area of 250 μm square in one visual field at an arbitrary position on the sample, and a dark spot density obtained as an evaluation result can be treated as a dislocation density. That is, in this specification, the dark spot density measured by 2PPL is treated as the dislocation density.

  As will be described in detail in an experimental example described later, the crystal layer 300 is grown so that pits are not formed over the entire surface of at least a 250 μm square region of the surface of the crystal layer 300 on the base surface 201 of the member 200. This is the aspect that can be done. The base surface 201 is a surface on which the crystal layer 300 can be grown two-dimensionally without growing it three-dimensionally. Therefore, by using the member 200 according to the present embodiment, it is possible to obtain the crystal layer 300 in which the uniformity of the crystal quality in the in-plane direction and the thickness direction is improved.

  FIG. 1A is a flowchart schematically illustrating a method for manufacturing the member 200. The method for manufacturing the member 200 includes a step S10 of preparing the nitride crystal member 100 having the altered layer on the surface 101, a step S20 of etching the surface 101 of the nitride crystal member 100, and a step S20 for etching the surface 101 of the nitride crystal member 100. And removing step S30. The surface 101 of the nitride crystal member 100 is a surface to be the lower ground surface 201 for growing the crystal layer 300 in the member 200 through the etching step S20 and the group III element removing step S30. Since nitride crystal member 100 is a precursor member for producing member 200, it is also referred to as precursor member 100. Hereinafter, the description will proceed more specifically along the first embodiment and the second embodiment.

<First embodiment>
A first embodiment will be described. In the first embodiment, a nitride crystal substrate 210 (hereinafter, also referred to as a substrate 210) is exemplified as a specific mode of the member 200, and a nitride crystal substrate 110 ( Hereinafter, the substrate is also referred to as an as-sliced substrate 110). FIG. 1A is a flowchart schematically illustrating a method of manufacturing the member 200, that is, the substrate 210 according to the first embodiment. 2A to 2C are schematic cross-sectional views illustrating a method for manufacturing the substrate 210.

  In step S10, as shown in FIG. 2A, a precursor member 100 according to the first embodiment, that is, an as-sliced substrate 110 is prepared. Step S10 is performed, for example, as follows. An ingot, which is a nitride crystal grown as thick as slicable, is prepared. As a method of growing a nitride crystal to obtain an ingot, for example, a void formation peeling (VAS) method may be used, or another method may be used.

In order for the dislocation density of the substrate 210 to satisfy the above-described conditions, the ingot preferably has an average dislocation density of less than 1 × 10 ⁷ / cm ^2, preferably 1 × 10 ⁷ / cm 2. More preferably, it does not include a dislocation concentrated region having a dislocation density of ² or more. The VAS method is preferable as a growth method for obtaining such an ingot.

  One or more as-sliced substrates 110 are obtained by slicing the ingot to a predetermined thickness. As the slicing means, for example, a wire saw may be used, for example, electric discharge machining may be used, and other means may be used. On the surface 101 of the as-sliced substrate 110, an altered layer 102 due to the slice is generated. In this way, an as-sliced substrate 110 having a slice-induced altered layer 102 on the surface 101 is prepared.

  The as-sliced substrate 110 is, for example, one obtained by slicing an ingot on a c-plane. In this case, the c-plane is a crystal plane having a low index closest to a virtual plane obtained by averaging the lower ground surface 201 of the substrate 210.

  The size of the as-sliced substrate 110 is not particularly limited, but is preferably, for example, 2 inches or more in diameter, and more preferably 4 inches or more in diameter. The thickness of the as-sliced substrate 110 is not particularly limited as long as the substrate 210 can stand on its own after the etching in step S20, and is, for example, 0.3 mm or more.

In step S20, as shown in FIG. 2B, the surface 101 of the as-sliced substrate 110 is etched. As the etching method, for example, gas etching may be used, and another method may be used. As the gas etching, for example, gas etching using a gas containing chlorine and a hydrogen (H ₂ ) gas added as needed as an etching gas can be used. As the gas containing chlorine, for example, at least one of a hydrogen chloride (HCl) gas and a chlorine (Cl ₂ ) gas is used. In such gas etching, the etching depth can be increased, for example, as the etching time is increased, and the etching rate can be increased, for example, as the etching temperature is increased. The etching depth, the etching rate, and the like can be appropriately adjusted as needed. The following are examples of the etching conditions.
Partial pressure of HCl gas: 4 to 15 kPa
Partial pressure of H ₂ gas: 0 to 81 kPa
Etching temperature: 650-1,000 ° C

  The etching in step S20 is performed such that the surface roughness PV on the lower ground surface 201 of the substrate 210 is generally 10 μm or less, preferably 2 μm or less, more preferably 1 μm or less (and, for example, 0.01 μm or more). .

  By the etching in step S20, the altered layer 102 is removed from the surface 101 of the as-sliced substrate 110. However, due to the etching, particles 103 containing a group III element (for example, Ga) derived from a group III nitride constituting the as-sliced substrate 110 are generated. As will be described in detail in an experimental example described later, it is not desirable that the particles 103 adhere to the base surface 201.

  In step S30, as shown in FIG. 2C, the particles 103 are removed, that is, the group III element is removed. Thus, the substrate 210 having the base surface 201 in which the adhesion of the group III element is suppressed is obtained. As a method for removing the group III element, for example, removal using an acid or an alkali may be used, or another method may be used.

  By the etching step S20 and the group III element removing step S30, the surface 101 of the as-sliced substrate 110 has a surface roughness PV of 0.01 μm or more and 10 μm or less, and the dislocation density in the crystal layer 300 is The lower surface 201 of the substrate 210 is capable of epitaxially growing the crystal layer 300 so as to have a density of twice or less. Note that the etching step S20 and the group III element removing step S30 may be collectively regarded as a step of forming the base surface 201. The group III element removing step S30 may be regarded as a step of suppressing the adhesion of the group III element to the underground 201.

  By the etching step S20, the deteriorated layer 102 on the surface 101 of the as-sliced substrate 110 can be removed, and the base surface 201 having a predetermined surface roughness PV can be obtained. Furthermore, the base surface 201 on which the crystal layer 300 can be favorably epitaxially grown can be obtained by suppressing the attachment of the group III element to the base surface 201 by the group III element removing step S30. As will be understood from the description of the experimental example described later, when the attachment of the group III element to the underlying surface 201 is not suppressed, an unintended three-dimensional growth layer is formed on the crystal layer 300 grown on the underlying surface 201, Accordingly, pits are likely to be generated, and it is difficult to sufficiently improve the quality of the crystal layer 300. By performing the group III element removing step S30, the base surface 201 on which the crystal layer 300 can be grown such that three-dimensional growth and pits do not occur over at least the entire 250 μm square region of the surface of the crystal layer 300 Can be obtained.

  The substrate 210 according to the first embodiment is a free-standing substrate whose entire thickness is made of a nitride crystal, and is distributed as a substrate for growing the crystal layer 300.

  Here, the surface on the base surface 201 side of the as-sliced substrate 110 and the substrate 210 is called a front surface, and the surface on the opposite side is called a back surface. As illustrated in FIGS. 2B and 2C, the etching in step S20 and the removal of the group III element in step S30 may be performed on both the front and back surfaces of the as-sliced substrate 110. However, since the back surface of the substrate 210 is not used as a base for epitaxial growth, it is sufficient that the altered layer caused by the slice is removed, and the flatness is not as high as that of the base surface 201 which is the front surface. May be. The flatness of the back surface of the substrate 210 only needs to be such that vacuum chucking is possible.

  An example of a method of performing gas etching on the as-sliced substrate 110 will be described. In this example, etching processing is simultaneously performed on a large number (for example, 100 to 200) of as-sliced substrates 110 by batch processing.

  FIGS. 3A and 3B are schematic diagrams showing an example of the gas etching apparatus 500. FIG. FIG. 3A is a schematic view of the gas etching apparatus 500 as viewed from the front, and FIG. 3B is a boat 520 carried into a reaction tube 510 of the gas etching apparatus 500 and a gas supply pipe. It is the schematic which looked at 540 from the side surface direction.

A boat 520 in which a large number of as-sliced substrates 110 are loaded in parallel is loaded into a reaction tube 510 of the gas etching apparatus 500. The inside of the reaction tube 510 is heated to a predetermined etching temperature by a heater 530 provided around the reaction tube 510. While the inside of the reaction tube 510 is heated to a predetermined etching temperature, an etching gas is supplied to the as-sliced substrate 110 from the gas supply tube 540 introduced into the reaction tube 510. In this example, HCl gas is supplied together with nitrogen (N ₂ ) gas from a gas supply pipe 541, and H ₂ gas is supplied together with N ₂ gas from a gas supply pipe 542. By supplying an etching gas in parallel to the as-sliced substrate 110, a large number of as-sliced substrates 110 are simultaneously etched, and both the front and back surfaces of each as-sliced substrate 110 are simultaneously etched. The exhaust gas after the etching is exhausted from the exhaust port to the outside of the reaction tube 510. The etching process is performed to an etching depth at which the lower surface 201 of the predetermined surface roughness PV is obtained.

  The growth of the crystal layer 300 using the substrate 210 will be described. As shown in FIG. 2D, a nitride crystal laminate in which the crystal layer 300 is stacked on the substrate 210 is formed by epitaxially growing the crystal layer 300 on the lower surface 201 of the substrate 210. Crystal layer 300 may be made of a group III nitride having the same composition as substrate 210, or may be made of a group III nitride having a composition different from that of substrate 210. The thickness of the crystal layer 300 to be grown may be appropriately selected as needed. As a method for growing the crystal layer 300, for example, a hydride vapor phase epitaxy (HVPE) method may be used, for example, a metal organic vapor phase epitaxy (MOVPE) method may be used, or another method may be used.

For example, the growth conditions of the GaN layer by the HVPE method are as follows.
Growth temperature: 980-1,100 ° C
Growth pressure: 90-105 kPa
GaCl gas partial pressure: 1.5 to 15 kPa
Partial pressures of / GaCl gas of the NH ₃ gas: 4-20
Partial pressures of / _{N 2} gas of the H ₂ gas: 20

  By using the substrate 210 of the present embodiment, even on the rough base surface 201 having a surface roughness PV of 10 μm or less, preferably 2 μm or less, more preferably 1 μm or less (and for example, 0.01 μm or more). As described above, the crystal layer 300 can be favorably grown epitaxially.

<Modification of First Embodiment>
A modification of the first embodiment will be described. In this modification, a laminated nitride crystal substrate 230 (hereinafter, laminated) having a structure in which a nitride crystal layer 220 (hereinafter, also referred to as a crystal layer 220) is laminated on a lower ground surface 201 of the substrate 210 of the first embodiment. The substrate 230) will be described. FIG. 1B is a flowchart schematically showing a method of manufacturing the laminated substrate 230. FIG. 4A is a schematic sectional view showing the laminated substrate 230.

  In the present modification, the surface 221 of the crystal layer 220 is used instead of the lower surface 201 of the substrate 210 as the lower surface for growing the crystal layer 300 on the laminated substrate 230. Based on such a situation, in this modification, the lower surface 201 of the substrate 210 may be referred to as the main surface 201, and the surface 221 of the crystal layer 220 may be referred to as the main surface 221 or the lower surface 221 of the laminated substrate 230. It may be called.

  The crystal layer 220 is configured such that the main surface 221 of the crystal layer 220, that is, the lower ground surface 221 of the laminated substrate 230 has higher flatness (small surface roughness PV) than the main surface 201 of the substrate 210. I have. Therefore, crystal layer 220 is also referred to as flatness improving layer 220.

  In FIG. 1B, steps S10, S20 and S30 are the same as those in FIG. 1A. That is, the process up to the step S30 of obtaining the substrate 210 is the same as that of the first embodiment. The manufacturing method of this modification further includes a flatness improving layer forming step S40.

  In step S40, as shown in FIG. 4A, the flatness improving layer 220 is epitaxially grown on the main surface 201 of the substrate 210. Since the flatness improving layer 220 is a nitride crystal layer epitaxially grown on the main surface 201 of the substrate 210, it is formed in the same manner as the crystal layer 300 described in the first embodiment with reference to FIG. can do.

  As will be described in detail in an experimental example described later, according to the findings of the present inventor, the HVPE method provides a nitride crystal layer having a high surface flatness on the lower ground of the present embodiment, for example, as compared with the MOVPE method. Is easy to form. The HVPE method also has an advantage that the growth rate is high. For this reason, it is preferable that the flatness improving layer 220 be grown by the HVPE method. The thickness of the flatness improving layer 220 is not particularly limited as long as the main surface 221 having higher flatness than the main surface 201 of the substrate 210 can be obtained. The flatness improving layer 220 may be grown to a thickness of, for example, 10 to 20 μm.

  Since the flatness improving layer 220 is a nitride crystal layer epitaxially grown on the main surface 201 of the substrate 210, it has the same characteristics as the crystal layer 300 described in the first embodiment, as described below. The flatness improving layer 220 has a dislocation density that is twice or less the dislocation density in the substrate 210. In addition, the flatness improving layer 220 has no pits over the entire area of at least the 250 μm square area of the main surface 221. The flatness improving layer 220 is grown two-dimensionally without growing three-dimensionally.

Flatness enhancing layer 220 of the crystal layer 300 for use as the base layer preferably has a dislocation density less than 1 × ¹⁰ 7 / cm ² as an average dislocation density, 1 × ¹⁰ 7 / cm ² or more More preferably, it does not include a dislocation concentrated region having a dislocation density.

  Since the flatness improving layer 220 is a nitride crystal layer epitaxially grown on the main surface 201 of the substrate 210, the main surface 221 of the flatness improving layer 220, that is, the lower ground surface 221 of the laminated substrate 230 will be described below. As described above, it can be configured to have the same characteristics as the lower ground surface 201 of the substrate 210 described in the first embodiment. The lower ground surface 221 is a surface on which the crystal layer 300 can be epitaxially grown such that the dislocation density in the crystal layer 300 is equal to or less than twice the dislocation density in the substrate 210. The base surface 221 is a surface on which the crystal layer 300 can be grown so that pits are not formed over the entire area of at least a 250 μm square region on the surface of the crystal layer 300. The base surface 221 is a surface on which the crystal layer 300 can be grown two-dimensionally without growing three-dimensionally.

  As described above, by forming the flatness improving layer 220 on the main surface 201 of the substrate 210, the laminated substrate 230 having the base surface 221 can be obtained. The laminated substrate 230 according to the present modification is a free-standing substrate whose entire thickness is made of a nitride crystal, and is distributed as a substrate for growing the crystal layer 300.

  The growth of the crystal layer 300 using the laminated substrate 230 will be described. As shown in FIG. 4B, the crystal layer 300 is epitaxially grown on the lower ground surface 221 of the multilayer substrate 230 to form a nitride crystal laminate in which the crystal layer 300 is stacked on the multilayer substrate 230. By using the laminated substrate 230 of the present modification, the crystal layer 300 can be favorably epitaxially grown on the base surface 221.

  In the present modification, the crystal layer 300 is grown on the lower ground surface 221 of the laminated substrate 230, that is, on the main surface 221 of the flatness improving layer 220, so that the crystal layer 300 is directly formed on the lower ground surface 201 of the substrate 210 of the first embodiment. The surface of the crystal layer 300 to be grown can be made more flat (with a small growth thickness) as compared with the case where the crystal layer 300 is specifically grown.

<Second embodiment>
A second embodiment will be described. In the second embodiment, a nitride crystal growth 250 (hereinafter, also referred to as a growth 250) is illustrated as a specific mode of the member 200, and a nitride crystal growth in an as-grown state is a specific mode of the precursor member 100. 150 (hereinafter, also referred to as as-grown body 150). FIG. 1A is a flowchart schematically illustrating a method of manufacturing the member 200, that is, the growth body 250 according to the second embodiment. 5A to 5C are schematic cross-sectional views illustrating a method of manufacturing the grown body 250.

  In step S10, as shown in FIG. 5A, a precursor member 100 according to the second embodiment, that is, an as-grown grown body 150 is prepared. Step S10 is performed, for example, as follows. A seed crystal 400 is prepared, and a nitride crystal is epitaxially grown on the seed crystal 400 to form an as-grown grown body 150. As the seed crystal 400, for example, a self-standing substrate of a nitride crystal may be used, or a seed crystal having another structure may be used. As a growth method of the as-grown growth body 150, for example, a liquid phase growth (LPE) method can be mentioned.

  The surface 101 of the as-grown grown body 150 grown by the LPE method is composed of a low-quality crystal layer that has been additionally grown during the temperature decrease after the growth is stopped. The low-quality crystal layer is a deteriorated layer 102 that is deteriorated with respect to the high-quality crystal inside the as-grown growth body 150, and has a rough surface 101.

  In step S20, as shown in FIG. 5B, the altered layer 102 is removed by etching the surface 101 of the as-grown body 150. In step S30, as shown in FIG. 5C, by removing the particles 103 containing the group III element generated due to the etching in step S20, the base surface 201 in which the adhesion of the group III element is suppressed is removed. obtain. As the etching technique in step S20 and the technique for removing the group III element in step S30, the same technique as in the first embodiment may be used. In this manner, in the second embodiment, a growth 250 having the base surface 201 corresponding to the as-grown surface 101 of the as-grown growth 150 is obtained.

  The growth of the crystal layer 300 using the growth body 250 will be described. As shown in FIG. 5D, the crystal layer 300 is epitaxially grown on the lower ground surface 201 of the growth body 250, thereby forming a nitride crystal laminate in which the crystal layer 300 is stacked on the growth body 250. Crystal layer 300 may be made of a group III nitride having the same composition as growth body 250, or may be made of a group III nitride having a composition different from growth body 250. The thickness of the crystal layer 300 to be grown may be appropriately selected as needed. As a method for growing the crystal layer 300, for example, the HVPE method may be used, or another method may be used. The HVPE method is preferable as a method for forming the thick crystal layer 300 on the growth body 250 because the growth rate is high. When growing crystal layer 300, seed crystal 400 may be in a state of being joined to growth body 250 or may be in a state of being removed from growth body 250.

  By using the growth body 250 of the present embodiment, the surface roughness PV is 10 μm or less, preferably 2 μm or less, more preferably 1 μm or less (for example, 0.01 μm or more) on the rough underlying surface 201. However, as described above, the crystal layer 300 can be favorably grown epitaxially. That is, according to the second embodiment, it is possible to prepare the lower ground surface 201 when the crystal layer 300 is regrown on the growth body 250 without performing a step of making the ground surface 201 a mirror surface by grinding and polishing.

  The as-grown growth body 150 is exemplified by the one grown by the LPE method. However, the as-grown growth body 150 has a rough surface 101 including the altered layer 102 obtained by abruptly interrupting the growth by the HVPE method. The same process may be performed on the as-grown body 150 to re-grow the crystal layer 300.

<Other embodiments>
The embodiment and the modification of the present invention have been specifically described above. However, the present invention is not limited to the above-described embodiments and modifications, and can be variously modified without departing from the gist thereof.

  In the above-described embodiment, GaN is exemplified as the III nitride constituting the member 200, but the member 200 may be composed of another group III nitride. The group III nitride forming the member 200 may include any one (at least one) of aluminum (Al), Ga, and indium (In) as a group III element.

  Each of the precursor member 100, the member 200, the flatness improving layer 220, and the crystal layer 300 may be added with an impurity such as a conductivity determining impurity as necessary.

<Example of experiment>
Next, an experimental example will be described. First, an experiment will be described in which an as-sliced GaN substrate (as-sliced substrate) is etched and a GaN layer is grown on the etched surface. In the description of the experimental example, a substrate obtained by etching an as-sliced substrate is referred to as a base substrate. It was investigated how the crystal quality of the GaN layer grown on the underlying substrate changes by changing the etching depth. As the as-sliced substrate, a GaN ingot grown by the VAS method and sliced on the c-plane was used. The average dislocation density in the crystals (crystals excluding the surface portion including the altered layer) of the bulk portion (of the underlying substrate) of the as-sliced substrate is 1.6 × 10 ⁶ / cm ² . The GaN layer was grown by the HVPE method.

  Each sample on which the GaN layer was grown while changing the etching depth was observed with a 2PPL apparatus. FIG. 6 is a 2PPL image of a GaN layer surface of a sample having an etching depth of 10 μm. FIG. 7 is a 2PPL image of the GaN layer surface of the sample having an etching depth of 35 μm. The upper part of FIGS. 6 and 7 is a 2PPL image of a region of about 250 μm square. The lower part of FIG. 7 is a 2PPL image of a region of about 60 μm square in which a part of the upper part of FIG. 7 is enlarged.

In the sample having an etching depth of 10 μm, the dislocation density of the GaN layer is much higher than 1 × 10 ⁷ / cm ² , which is significantly higher than the dislocation density of the underlying substrate (see FIG. 6). . It is considered that the dislocation density of the GaN layer increased due to the occurrence of dislocation on the surface of the base substrate. On the other hand, in the sample having an etching depth of 35 μm, although pits are remarkably observed (see the upper part of FIG. 7), the dislocation density of the crystal other than the pits is 9.7 × 10 ⁵ / cm ² . 7 can be said to be equivalent to the dislocation density of the underlying substrate (see the lower part of FIG. 7).

  From this result, it can be said that, by setting the etching depth to, for example, 35 μm or more, a GaN layer having a region having a dislocation density equivalent to that of the base substrate can be grown (the etching depth is smaller than 35 μm). Even if the etching depth is larger than 10 μm), there is a possibility that a GaN layer having a region where the dislocation density is equivalent to that of the underlying substrate can be grown). However, as shown in the upper part of FIG. 7, pits are remarkably observed and three-dimensional growth has occurred, so that the uniformity of the crystal quality of the GaN layer in the in-plane direction and the thickness direction is sufficiently high. Absent.

  The inventors of the present application have examined the reason. As a result, particles containing Ga (hereinafter also referred to as “Ga particles”) adhere to the surface of the base substrate due to the etching, and the Ga particles are nitrided to improve the quality. It has been found that the formation of a bad GaN crystal nucleus causes a decrease in the crystal quality of the GaN layer.

  Next, an experiment in which Ga particles attached to the surface of the base substrate are removed and a GaN layer is grown on the surface from which the Ga particles have been removed will be described. For each of the sample having an etching depth of 35 μm and the sample having an etching depth of 50 μm, a GaN layer was grown on the surface from which the Ga particles had been removed.

  Each sample was observed with a 2PPL device. FIG. 8 is a 2PPL image of a GaN layer surface of a sample having an etching depth of 35 μm, and is a 2PPL image of a region of about 250 μm square. No pits and slips are observed over the entire area of the 2PPL image, and a crystal with high in-plane uniformity is obtained. In addition, an area of about 750 μm square including the area shown in FIG. 8 was also observed, and pits and slips were not observed over the entire area of about 750 μm square, and a crystal having high in-plane uniformity was similarly observed. Has been confirmed.

  FIGS. 9A to 9E are 2PPL images of a sample having an etching depth of 35 μm observed at different depths, each being a 2PPL image of a region of about 60 μm square. 9A is a 2PPL image of the GaN layer surface, FIG. 9B is a 2PPL image of the GaN layer having a depth of 50 μm from the GaN layer surface, and FIG. 9C is the GaN layer surface. 7 is a 2PPL image of a GaN layer having a depth of 87.5 μm from FIG. FIG. 9D is a 2PPL image of a depth of 127.5 μm from the surface of the GaN layer, that is, a 2PPL image of an interface between the GaN layer and the underlying substrate. FIG. 9E is a 2PPL image of a depth of 140 μm from the GaN layer surface, which is a 2PPL image of the underlying substrate.

The dislocation density at the surface of the GaN layer is 2.1 × 10 ⁶ / cm ² , the dislocation density at a depth of 50 μm is 2.1 × 10 ⁶ / cm ² , and the dislocation density at a depth of 87.5 μm. The density is 2.1 × 10 ⁶ / cm ² . The dislocation density of the base substrate is 1.6 × 10 ⁶ / cm ² . Thus, it can be seen that the GaN layer is epitaxially grown so that the dislocation density equivalent to that of the underlying substrate is maintained. Here, the dislocation density of the GaN layer is suppressed to twice or less (more preferably, 1.5 times or less) the dislocation density of the underlying substrate, that is, no significant increase in the dislocation density in the GaN layer is observed. This is an indication that the dislocation density of the GaN layer is maintained equal to that of the underlying substrate.

  As can be seen from FIGS. 9 (a) to 9 (c), no trace of pits is observed from the interface between the underlying substrate and the GaN layer to the surface of the GaN layer. Two-dimensional growth occurs without dimensional growth. As described above, by removing Ga particles from the surface of the base substrate, a crystal having high uniformity in the in-plane direction and uniformity in the thickness direction can be obtained.

  For a sample with an etching depth of 50 μm, similar pits and slips were not observed over the entire region of about 750 μm square by observing the same 2PPL image, and a GaN layer having a dislocation density equivalent to that of the underlying substrate was obtained. Have confirmed. Therefore, it can be said that the GaN layer can be favorably epitaxially grown on the base substrate by setting the etching depth to, for example, 35 μm or more.

  FIGS. 10A and 10B are fluorescent images obtained by optical microscopic observation of the cross sections of the sample having an etching depth of 35 μm and the sample having an etching depth of 50 μm, respectively. In each fluorescent image, the lower part of the dark color is the underlying substrate, and the GaN layer is formed on the surface of the underlying substrate. It can be seen that the flatness of the surface of the underlying substrate is higher in the sample with the etching depth of 50 μm than in the sample with the etching depth of 35 μm. As described above, the flatness of the surface of the base substrate can be improved as the etching depth is increased.

  FIG. 10A shows that the surface roughness PV of the base substrate surface of the sample having the etching depth of 35 μm is about 10 μm. Therefore, it can be said that setting the etching depth to 35 μm or more corresponds to setting the surface roughness PV of the underlying substrate to 10 μm or less. By setting the surface roughness PV of the underlying substrate to 10 μm or less, The GaN layer can be favorably grown epitaxially.

  In this experimental example, it was found that an etching depth of 35 μm or more is preferable in order to sufficiently remove the altered layer. However, this etching depth is an example when the base substrate of this experimental example is used. The etching depth for sufficiently removing the altered layer may vary depending on the thickness of the altered layer formed on the underlying surface. The thickness at which the altered layer is formed on the underlying surface may vary depending on the slicing conditions in the case of as-slicing, and in the case of as-grown, for example, by the growth termination sequence of LPE, and for example, unexpected growth interruption of HVPE growth. It can vary depending on the growth conditions at the time. Therefore, the etching depth may be appropriately adjusted according to the base member to be etched so that the altered layer is sufficiently removed and the surface roughness PV is 10 μm or less.

  Next, an experiment for measuring the surface roughness PV and the like of the underlying substrate will be described. The surface roughness of the underlying substrate was measured for a two-dimensional area of 0.14 mm × 0.11 mm by an optical surface texture measuring device using a laser interferometer manufactured by Zygo. As the surface roughness, a peak-to-valley value (surface roughness PV), a root-mean-square roughness (surface roughness RMS), and an arithmetic average roughness (surface roughness Ra) were measured.

  Here, the measurement result of an as-sliced substrate that has not been subjected to etching and the measurement of a base substrate that has been subjected to etching such that the surface roughness PV is about 1 μm (hereinafter, also referred to as a base substrate that has been etched flat) will be described. And the results. FIG. 11 is a perspective view showing the surface of an as-sliced substrate that has not been subjected to etching. FIG. 12 is a perspective view showing the surface of the base substrate etched flat.

  The surface roughness PV of the as-sliced substrate is 12.8 μm, and the surface roughness PV of the base substrate etched flat is 1.1 μm. The surface roughness RMS of the as-sliced substrate is 2.3 μm, and the surface roughness RMS of the base substrate etched flat is 0.10 μm. The surface roughness Ra of the as-sliced substrate is 1.8 μm, and the surface roughness Ra of the base substrate etched flat is 0.08 μm.

  Next, an experiment will be described in which the difference in the surface flatness of the GaN layer grown on the base substrate from which the Ga particles have been removed due to the growth method is examined. A sample in which the GaN layer was grown by the HVPE method and a sample in which the GaN layer was grown by the MOVPE method were produced.

  FIG. 13A is a photograph showing the entire GaN layer grown by the HVPE method, and FIG. 13B is a differential interference image obtained by observing the surface of the GaN layer with an optical microscope. FIG. 14A is a photograph showing the entire GaN layer grown by the MOVPE method, and FIG. 14B is a differential interference image obtained by observing the surface of the GaN layer with an optical microscope.

  The GaN layer surface of the sample grown by the HVPE method is very flat. The surface of the GaN layer of the sample grown by the MOVPE method is also almost flat, as can be seen from the photograph showing the whole, but has some irregularities as can be seen from the differential interference image. It is thought that the surface flatness of the GaN layer grown on the base substrate by the MOVPE method can be improved by adjusting the growth conditions, but the general tendency is that the surface flatness when grown by the HVPE method is reduced. In comparison, it tends to be lower. In other words, it can be said that the HVPE method is a method for easily forming a GaN layer having high surface flatness on the base substrate.

<Preferred embodiment of the present invention>
Hereinafter, preferred embodiments of the present invention will be additionally described.

(Appendix 1)
A nitride crystal member composed of a group III nitride crystal and having an underground for growing a nitride crystal layer,
The base surface has a surface roughness PV expressed by a peak-to-valley value of 0.01 μm or more and 10 μm or less, and a dislocation density in the nitride crystal layer is twice or less of a dislocation density in the nitride crystal member. Is a surface on which the nitride crystal layer can be epitaxially grown.
Nitride crystal members.

(Appendix 2)
The surface roughness PV of the base surface is preferably 5 μm or less, more preferably 2 μm or less, further preferably 1.5 μm or less, still more preferably 1 μm or less, particularly preferably 0.9 μm or less, and still more preferably 0.1 μm or less. 8 μm or less, more preferably 0.7 μm or less, still more preferably 0.6 μm or less, particularly preferably 0.5 μm or less.
3. The nitride crystal member according to supplementary note 1.

(Appendix 3)
The surface roughness PV of the base surface is preferably 0.02 μm or more, more preferably 0.05 μm or more, further preferably 0.1 μm or more, still more preferably 0.2 μm or more, particularly preferably 0.3 μm or more, More particularly preferably 0.4 μm or more,
3. The nitride crystal member according to supplementary note 1 or 2.

(Appendix 4)
The nitride crystal member has a dislocation density of less than 1 × 10 ⁷ / cm ² ;
The nitride crystal member according to any one of supplementary notes 1 to 3.

(Appendix 5)
The nitride crystal member does not include a dislocation concentrated region having a dislocation density of 1 × 10 ⁷ / cm ² or more;
5. The nitride crystal member according to any one of supplementary notes 1 to 4.

(Appendix 6)
The base surface is a surface on which the nitride crystal layer can be grown so that pits are not formed over the entire area of at least a 250 μm square region of the surface of the nitride crystal layer.
6. The nitride crystal member according to any one of supplementary notes 1 to 5.

(Appendix 7)
The base surface is a surface on which the nitride crystal layer can be grown two-dimensionally without growing it three-dimensionally.
7. The nitride crystal member according to any one of supplementary notes 1 to 6.

(Appendix 8)
The nitride crystal member is a free-standing substrate in which the entire thickness of the nitride crystal member is formed of a group III nitride crystal.
8. The nitride crystal member according to any one of supplementary notes 1 to 7.

(Appendix 9)
The nitride crystal member is distributed as a substrate for growing the nitride crystal layer,
9. The nitride crystal member according to any one of supplementary notes 1 to 8.

(Appendix 10)
A low-index crystal plane closest to a virtual plane obtained by averaging the ground plane is a c-plane.
10. The nitride crystal member according to any one of supplementary notes 1 to 9.

(Appendix 11)
The base surface corresponds to the surface of the as-grown of the nitride crystal member,
9. The nitride crystal member according to any one of supplementary notes 1 to 8.

(Appendix 12)
The nitride crystal layer grown on the base surface is laminated,
12. The nitride crystal member according to any one of supplementary notes 1 to 11.

(Appendix 13)
Preparing a nitride crystal member composed of a group III nitride crystal and having an altered layer on a surface to be a lower ground for growth of a nitride crystal layer,
Etching said surface,
Removing the group III element generated due to the etching such that adhesion to the base surface is suppressed;
A method for producing a nitride crystal member comprising:
By etching the surface and removing the group III element generated due to the etching so that the adhesion to the base surface is suppressed,
The surface has a surface roughness PV represented by a peak-to-valley value of 0.01 μm or more and 10 μm or less, and the dislocation density in the nitride crystal layer is twice or less the dislocation density in the nitride crystal member. As described above, the nitride crystal layer is used as the base surface on which epitaxial growth can be performed,
A method for manufacturing a nitride crystal member.

(Appendix 14)
Not having a grinding step and a polishing step for the surface,
14. The method for producing a nitride crystal member according to supplementary note 13.

(Appendix 15)
A nitride crystal substrate composed of a group III nitride crystal and having a first main surface;
A first nitride crystal layer composed of a group III nitride crystal and epitaxially grown on the first main surface and having a second main surface;
A laminated nitride crystal substrate comprising:
The second main surface of the first nitride crystal layer has higher flatness than the first main surface of the nitride crystal substrate, and is a lower ground surface for growing the second nitride crystal layer. ,
Multilayer nitride crystal substrate.

(Appendix 16)
The second main surface of the first nitride crystal layer is formed such that a dislocation density in the second nitride crystal layer is equal to or less than twice a dislocation density in the nitride crystal substrate. Surface on which layers can be grown epitaxially,
16. The laminated nitride crystal substrate according to supplementary note 15.

(Appendix 17)
The first principal surface of the nitride crystal substrate has a surface roughness PV represented by a peak-to-valley value of 0.01 μm or more and 10 μm or less, and the dislocation density in the first nitride crystal layer is A surface on which the first nitride crystal layer can be grown so as to have a dislocation density of twice or less the crystal substrate.
17. The laminated nitride crystal substrate according to supplementary note 15 or 16.

(Appendix 18)
The surface roughness PV of the first main surface is preferably 5 μm or less, more preferably 2 μm or less, further preferably 1.5 μm or less, still more preferably 1 μm or less, particularly preferably 0.9 μm or less, and still more preferably. 0.8 μm or less, more preferably 0.7 μm or less, still more preferably 0.6 μm or less, particularly preferably 0.5 μm or less,
18. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 17.

(Appendix 19)
The surface roughness PV of the first main surface is preferably 0.02 μm or more, more preferably 0.05 μm or more, further preferably 0.1 μm or more, further preferably 0.2 μm or more, and still more preferably 0.3 μm or more. , More preferably 0.4 μm or more,
19. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 18.

(Appendix 20)
The nitride crystal substrate (the first nitride crystal layer) has a dislocation density of less than 1 × 10 ⁷ / cm ² ;
20. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 19.

(Appendix 21)
The nitride crystal substrate (the first nitride crystal layer) does not include a dislocation concentrated region having a dislocation density of 1 × 10 ⁷ / cm ² or more;
21. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 20.

(Appendix 22)
The second main surface of the first nitride crystal layer is formed on the second nitride crystal layer such that pits are not formed over the entire area of at least a 250 μm square region of the surface of the second nitride crystal layer. The surface that can be grown,
22. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 21.

(Appendix 23)
The second main surface of the first nitride crystal layer is a surface on which the second nitride crystal layer can be grown two-dimensionally without growing it three-dimensionally.
23. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 22.

(Appendix 24)
The first nitride crystal layer has a dislocation density that is not more than twice the dislocation density in the nitride crystal substrate,
24. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 23.

(Appendix 25)
The first nitride crystal layer has no pits over the entire area of at least a 250 μm square area of the second main surface;
25. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 24.

(Supplementary Note 26)
The first nitride crystal layer grows two-dimensionally without growing three-dimensionally;
26. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 25.

(Appendix 27)
The laminated nitride crystal substrate is a self-standing substrate in which the total thickness of the laminated nitride crystal substrate is made of a group III nitride crystal.
27. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 26.

(Appendix 28)
The laminated nitride crystal substrate is distributed as a substrate for growing the second nitride crystal layer,
28. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 27.

(Appendix 29)
The nitride crystal substrate is a self-supporting substrate integrally formed of a group III nitride crystal (in a continuous crystal) in an in-plane direction of the first main surface.
30. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 28.

(Appendix 30)
The second nitride crystal layer grown on the second main surface is laminated;
30. The laminated nitride crystal substrate according to any one of supplementary notes 15 to 29.

(Appendix 31)
Preparing an as-sliced nitride crystal substrate composed of a group III nitride crystal and having an altered layer on a surface to be a first main surface for growing a first nitride crystal layer;
Etching said surface,
Removing a group III element generated due to the etching such that adhesion to the first main surface is suppressed;
Epitaxially growing a first nitride crystal layer composed of a group III nitride crystal and having a second main surface having a higher flatness than the first main surface on the first main surface;
A method for producing a laminated nitride crystal substrate comprising:
By etching the surface and removing a group III element generated due to the etching such that adhesion to the first main surface is suppressed,
The surface has a surface roughness PV represented by a peak-to-valley value of 0.01 μm or more and 10 μm or less, and the dislocation density in the first nitride crystal layer is twice or less the dislocation density in the nitride crystal substrate. The first main surface on which the first nitride crystal layer can be epitaxially grown,
The second main surface is used as a ground for growing a second nitride crystal layer,
The second nitride crystal layer can be epitaxially grown such that the dislocation density in the second nitride crystal layer is equal to or less than twice the dislocation density in the nitride crystal substrate.
A method for manufacturing a laminated nitride crystal substrate.

(Supplementary Note 32)
Not having a grinding step and a polishing step for the surface,
A manufacturing method of a laminated nitride crystal substrate according to supplementary note 31.

Reference Signs List 100: nitride crystal member (precursor member), 101: surface, 102: altered layer, 103: particles containing group III element, 110: as-sliced nitride crystal substrate, 150: as-grown nitride crystal growth , 200: nitride crystal member (member), 201: base surface, 210: nitride crystal substrate, 220: nitride crystal layer (flatness improving layer), 221: base surface, 230: laminated nitride crystal substrate, 250 ... nitride crystal growth, 300 ... nitride crystal layer, 400 ... seed crystal, 500 ... gas etching equipment

Claims (19)

A nitride crystal member composed of a group III nitride crystal and having an underground for growing a nitride crystal layer,
The base surface has a surface roughness PV expressed by a peak-to-valley value of 0.01 μm or more and 10 μm or less, and a dislocation density in the nitride crystal layer is twice or less of a dislocation density in the nitride crystal member. Is a surface on which the nitride crystal layer can be epitaxially grown.
Nitride crystal members. The surface roughness PV of the ground surface is 2 μm or less,
The nitride crystal member according to claim 1. The nitride crystal member has a dislocation density of less than 1 × 10 ⁷ / cm ² ;
The nitride crystal member according to claim 1. The base surface is a surface on which the nitride crystal layer can be grown so that pits are not formed over the entire area of at least a 250 μm square region of the surface of the nitride crystal layer.
The nitride crystal member according to claim 1. The base surface is a surface on which the nitride crystal layer can be grown two-dimensionally without growing it three-dimensionally.
The nitride crystal member according to claim 1. The nitride crystal member is distributed as a substrate for growing the nitride crystal layer,
The nitride crystal member according to claim 1. The base surface corresponds to the surface of the as-grown of the nitride crystal member,
The nitride crystal member according to claim 1. The nitride crystal layer grown on the base surface is laminated,
The nitride crystal member according to claim 1. Preparing a nitride crystal member composed of a group III nitride crystal and having an altered layer on a surface to be a lower ground for growth of a nitride crystal layer,
Etching said surface,
Removing the group III element generated due to the etching such that adhesion to the base surface is suppressed;
A method for producing a nitride crystal member comprising:
By etching the surface and removing the group III element generated due to the etching so that the adhesion to the base surface is suppressed,
The surface has a surface roughness PV represented by a peak-to-valley value of 0.01 μm or more and 10 μm or less, and the dislocation density in the nitride crystal layer is twice or less the dislocation density in the nitride crystal member. As described above, the nitride crystal layer is used as the base surface on which epitaxial growth can be performed,
A method for manufacturing a nitride crystal member. Not having a grinding step and a polishing step for the surface,
A method for manufacturing a nitride crystal member according to claim 9. A nitride crystal substrate composed of a group III nitride crystal and having a first main surface;
A first nitride crystal layer composed of a group III nitride crystal and epitaxially grown on the first main surface and having a second main surface;
A laminated nitride crystal substrate comprising:
The second main surface of the first nitride crystal layer has higher flatness than the first main surface of the nitride crystal substrate, and is a lower ground surface for growing the second nitride crystal layer. ,
Multilayer nitride crystal substrate. The second main surface of the first nitride crystal layer is formed such that a dislocation density in the second nitride crystal layer is equal to or less than twice a dislocation density in the nitride crystal substrate. Surface on which layers can be grown epitaxially,
A laminated nitride crystal substrate according to claim 11. The nitride crystal substrate has a dislocation density of less than 1 × 10 ⁷ / cm ² ;
The multilayer nitride crystal substrate according to claim 11. The second main surface of the first nitride crystal layer is formed on the second nitride crystal layer such that pits are not formed over the entire area of at least a 250 μm square region of the surface of the second nitride crystal layer. The surface that can be grown,
The multilayer nitride crystal substrate according to any one of claims 11 to 13. The second main surface of the first nitride crystal layer is a surface on which the second nitride crystal layer can be grown two-dimensionally without growing it three-dimensionally.
The laminated nitride crystal substrate according to any one of claims 11 to 14. The laminated nitride crystal substrate is distributed as a substrate for growing the second nitride crystal layer,
A laminated nitride crystal substrate according to any one of claims 11 to 15. The second nitride crystal layer grown on the second main surface is laminated;
The multilayer nitride crystal substrate according to any one of claims 11 to 16. Preparing an as-sliced nitride crystal substrate composed of a group III nitride crystal and having an altered layer on a surface to be a first main surface for growing a first nitride crystal layer;
Etching said surface,
Removing a group III element generated due to the etching such that adhesion to the first main surface is suppressed;
Epitaxially growing a first nitride crystal layer composed of a group III nitride crystal and having a second main surface having a higher flatness than the first main surface on the first main surface;
A method for producing a laminated nitride crystal substrate comprising:
By etching the surface and removing a Group III element generated due to the etching such that adhesion to the first main surface is suppressed,
The surface has a surface roughness PV represented by a peak-to-valley value of 0.01 μm or more and 10 μm or less, and the dislocation density in the first nitride crystal layer is twice or less the dislocation density in the nitride crystal substrate. The first main surface on which the first nitride crystal layer can be epitaxially grown,
The second main surface is used as a ground for growing a second nitride crystal layer,
The second nitride crystal layer can be epitaxially grown such that the dislocation density in the second nitride crystal layer is equal to or less than twice the dislocation density in the nitride crystal substrate.
A method for manufacturing a laminated nitride crystal substrate. Not having a grinding step and a polishing step for the surface,
A method for manufacturing a laminated nitride crystal substrate according to claim 18.