JP2015044706A - Substrate for growing nitride semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate for growing a nitride semiconductor having low manufacturing cost, capable of epitaxially growing a nitride semiconductor uniformly on the whole main surface.SOLUTION: In a substrate for growing a nitride semiconductor including a ground substrate 1 and a nitride semiconductor layer 2 formed on the ground substrate 1, the nitride semiconductor layer 2 is formed by irradiating a silicon nitride film formed on the ground substrate 1 with an element as ion, and a value obtained by dividing a difference between the maximum value and the minimum value of the element concentration in the thickness direction by the maximum value is 40% or less, in the nitride semiconductor layer 2.

Description

  The present invention relates to a nitride semiconductor growth substrate for epitaxially growing a nitride semiconductor.

  Nitride substrates such as a gallium nitride (GaN) substrate having an energy band gap of 3.4 eV and high thermal conductivity are attracting attention as materials for semiconductor devices such as short-wavelength optical devices and power electronic devices. However, such a nitride substrate is expensive.

  International Publication No. 2006/104064 (Patent Document 1) discloses a gallium nitride growth substrate for forming a gallium nitride (GaN) film on a silicon (Si) substrate, a glass substrate, or a gallium arsenide (GaAs) substrate, and the same A manufacturing method is disclosed. Specifically, it is described that a GaN film can be formed on the surface layer of a SiN film by irradiating the surface of a silicon nitride (SiN) film formed on a substrate with Ga ions at an energy of 4 keV. ing.

International Publication No. 2006/104064

  However, the inventors of the present application uniformly grown gallium nitride on the entire main surface of the gallium nitride growth substrate when epitaxial growth was performed using the gallium nitride growth substrate manufactured by the method described in Patent Document 1. It was found that there is a problem that it is difficult to do.

  The present invention has been made to solve the above-described problems. A main object of the present invention is to provide a nitride semiconductor growth substrate that is low in manufacturing cost and capable of uniformly epitaxially growing a nitride semiconductor over the entire main surface.

  The nitride semiconductor growth substrate of the present invention includes a base substrate and a nitride semiconductor layer formed on the base substrate, and the nitride semiconductor layer is formed on the silicon nitride film formed on the base substrate. The nitride semiconductor layer is formed by irradiating the element as ions, and a value obtained by dividing the difference between the maximum value and the minimum value of the ion concentration in the thickness direction by the maximum value is 40% or less.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing cost is low, and the board | substrate for nitride semiconductor growth which can epitaxially grow a nitride semiconductor on the whole main surface can be provided.

It is a figure for demonstrating the board | substrate for nitride semiconductor growth which concerns on this Embodiment. It is a figure for demonstrating the manufacturing method of the board | substrate for nitride semiconductor growth which concerns on this Embodiment. It is a figure for demonstrating the manufacturing method of the board | substrate for nitride semiconductor growth which concerns on this Embodiment. It is a figure for demonstrating the manufacturing method of the board | substrate for nitride semiconductor growth which concerns on this Embodiment. It is a figure for demonstrating the nitride semiconductor epitaxial substrate which concerns on this Embodiment. In Example 1, it is a graph which shows the measurement result of the density | concentration profile of Ga in the GaN layer as a nitride semiconductor layer.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

[Description of Embodiment of Present Invention]
First, the outline of the embodiment of the present invention will be enumerated.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have found that in the nitride semiconductor growth substrate, the concentration of atoms that combine with nitrogen in the nitride semiconductor layer in the thickness direction of the nitride semiconductor layer. It has been found that the nitride semiconductor epitaxial layer can be uniformly epitaxially grown on the nitride semiconductor layer by reducing the variation.

  (1) Referring to FIGS. 1 and 2, a nitride semiconductor growth substrate 10 according to the present embodiment includes a base substrate 1 and a nitride semiconductor layer 2 formed on base substrate 1. The nitride semiconductor layer 2 is formed by irradiating the silicon nitride film 3 formed on the base substrate 1 with an element as an ion. In the nitride semiconductor layer 2, the concentration of the element in the thickness direction is formed. The value obtained by dividing the difference between the maximum value and the minimum value by the maximum value is 40% or less.

  That is, in the nitride semiconductor layer 2 in the nitride semiconductor growth substrate 10 according to the present embodiment, the elements combined with nitrogen in the nitride semiconductor layer are dispersed without being unevenly distributed in the film thickness direction (depth direction). Yes. The nitride semiconductor layer 2 is formed by irradiating an element with ions on the silicon nitride film 3, and the position where the element is introduced in the thickness direction of the silicon nitride film 3 depends on the irradiation energy of ions. Determined. In the nitride semiconductor growth substrate 10 according to the present embodiment, the silicon nitride film 3 is nitrided by irradiating an element with ions under a plurality of irradiation energy conditions as compared with the case of irradiation with one irradiation energy condition. The elements can be distributed with good uniformity in the film thickness direction of the physical semiconductor layer 2 (or silicon nitride film 3).

  The nitride semiconductor growth substrate 10 according to the present embodiment thus obtained is, for example, compared with a conventional nitride semiconductor growth substrate in which a nitride semiconductor layer is formed only on the surface layer portion of the silicon nitride film 3. A nitride semiconductor can be epitaxially grown more densely on the second main surface 2A.

  (2) In the nitride semiconductor growth substrate according to the present embodiment, the element may be at least one selected from the group consisting of gallium (Ga), indium (In), and aluminum (Al). . Even in this case, by irradiating the silicon nitride film 3 with the above-described element, the nitride semiconductor layer 2 in which the element is uniformly distributed can be formed.

(3) In the nitride semiconductor growth substrate 10 according to the present embodiment, the composition of the nitride semiconductor layer 2 may be represented by Al _1-xy Ga _x In _y N. As described above, at least one or more selected from the group consisting of Ga, In, and Al as an element is irradiated with ions, thereby causing Al _1-xy Ga _x In _y N (x ≧ 0, y ≧ 0, A nitride semiconductor growth substrate 10 including the nitride semiconductor layer 2 represented by 0 ≦ x + y ≦ 1) can be obtained.

  (4) In the nitride semiconductor growth substrate 10 according to the present embodiment, the nitride semiconductor layer 2 may have a film thickness of 10 nm or less.

  That is, the thickness of the silicon nitride film 3 irradiated with ions of the element may be 10 nm or less. In this way, an element irradiated with ions under a predetermined irradiation condition can easily reach a region adjacent to the first main surface 1A of the base substrate 1 in the silicon nitride film 3. As a result, ions of the above elements can be widely introduced in the film thickness direction (depth direction) of the silicon nitride film 3, and the nitride semiconductor layer 2 with higher element uniformity in the film thickness direction can be obtained. . That is, in the nitride semiconductor growth substrate 10 according to the present embodiment, when the film thickness of the nitride semiconductor layer 2 is 10 nm or less, the elements in the nitride semiconductor layer 2 are more uniformly distributed in the film thickness direction. Will be.

[Details of the embodiment of the present invention]
Next, details of the embodiment of the present invention will be described.

  A nitride semiconductor growth substrate 10 according to the present embodiment will be described with reference to FIG. A nitride semiconductor growth substrate 10 according to the present embodiment includes a base substrate 1 and a nitride semiconductor layer 2 formed on a first main surface 1A of the base substrate 1.

  The base substrate 1 is made of, for example, silicon (Si) and has a first main surface 1A having an outer diameter of 100 mm. First main surface 1A is, for example, a (100) plane.

The nitride semiconductor layer 2 is formed on the first main surface 1A of the base substrate 1. The nitride semiconductor layer 2 mainly contains nitrogen (N) and gallium (Ga). The nitride semiconductor layer 2 has a second main surface 2A. In the nitride semiconductor layer 2, the Ga concentration is almost uniform both in the direction parallel to the second main surface 2 </ b> A and in the direction perpendicular to the thickness (thickness direction). In the thickness direction of the nitride semiconductor layer 2, a value obtained by dividing the difference between the maximum value _Dmax and the minimum value _{Dmin of} Ga, which is an element combined with nitrogen in the nitride semiconductor layer 2, by the maximum value _Dmax (( _{Dmax− Dmin} ) / _Dmax ) is 40% or less.

  A method for manufacturing the nitride semiconductor growth substrate 10 according to the present embodiment will now be described with reference to FIGS. The method for manufacturing a nitride semiconductor growth substrate 10 according to the present embodiment includes a step of preparing a material substrate 20 including a base substrate 1 and a silicon nitride film 3 formed on the base substrate 1 (S11), and nitriding A step of irradiating the silicon film 3 with ions (S12).

First, the material substrate 20 is prepared (step (S11)). Specifically, first, a base substrate 1 having an outer diameter of 100 mm and made of Si is prepared. The base substrate 1 has a first main surface 1A, and the plane orientation is the (100) plane. The base substrate 1 may be prepared by any method. The outer diameter of the base substrate 1 is not limited to 100 mm, and may be 6 inches, for example. Next, a silicon nitride film 3 made of silicon nitride (SiN) is formed on the first main surface 1A of the base substrate 1. The silicon nitride film 3 may be formed by any method. For example, the silicon nitride film 3 is made of SiN on the first main surface 1A (Si (100) surface) by using a metal organic chemical vapor deposition method (MOCVD method). A silicon nitride film 3 may be formed. Alternatively, the silicon nitride film 3 made of SiN may be formed by nitriding the first main surface 1A (Si (100) surface) in an ammonia (NH ₃ ) atmosphere at 1200 ° C. The thickness of the silicon nitride film 3 is preferably 10 nm or less, for example 5 nm. The silicon nitride film 3 has a third third main surface 3A.

Next, the silicon nitride film 3 is irradiated with Ga ions (step (S12)). Specifically, the silicon nitride film 3 is irradiated with Ga ions from the third main surface 3A side using an ion implantation apparatus. At this time, Ga ions are irradiated under a plurality of energy conditions, for example, in an irradiation energy range of 0.1 keV to 100 keV. In the present embodiment, the silicon nitride film 3 is irradiated with Ga ions, for example, under three conditions of 0.5 keV, 2 keV, and 5 keV. In each irradiation condition, the dose amount of ions can be selected as appropriate, but in any case, 1.0 × 10 ¹⁶ cm ⁻² or more is preferable, and more preferably 3.0 × 10 ¹⁶ cm ⁻² or more. The dose amount of ions under each irradiation condition may be set equal, or may be set to different values.

By irradiating the silicon nitride film 3 with Ga ions, the silicon nitride film 3 is replaced with Ga irradiated with Si, and a nitride semiconductor layer 2 made of GaN is formed as shown in FIG. At this time, Si that has been decoupled from N is contained in the nitride semiconductor layer 2. Thus, the nitride semiconductor growth substrate 10 according to the present embodiment can be manufactured. In addition, the temperature conditions at the time of ion irradiation should just be room temperature, for example, and the pressure conditions should just be about 1 * 10 <^-6> Pa, for example.

  Next, a method for manufacturing nitride semiconductor epitaxial substrate 30 using nitride semiconductor growth substrate 10 according to the present embodiment will be described with reference to FIG. The method for manufacturing a nitride semiconductor epitaxial substrate according to the present embodiment includes a step (S10) of preparing a nitride semiconductor growth substrate 10 and a nitride on second main surface 2A of nitride semiconductor growth substrate 10. A step of epitaxially growing a semiconductor (S20).

  First, a nitride semiconductor growth substrate 10 is prepared (step (S10)). Specifically, the nitride semiconductor growth substrate 10 is manufactured by the method of manufacturing a nitride semiconductor growth substrate according to the present embodiment.

  Next, the nitride semiconductor epitaxial layer 4 is epitaxially grown on the second main surface 2A of the nitride semiconductor growth substrate 10 (step (S20)). The method for growing the nitride semiconductor epitaxial layer 4 is not particularly limited, but from the viewpoint of obtaining a nitride semiconductor epitaxial substrate 30 with good crystallinity, HVPE (hydride vapor phase epitaxy) method, MOVPE (organometallic vapor phase epitaxy). For example, a vapor phase method such as an MBE (molecular beam epitaxy) method or a sublimation method, a liquid phase method such as a flux method or a high nitrogen pressure solution method is preferable.

  Note that after the nitride semiconductor epitaxial layer 4 is grown on the nitride semiconductor layer 2, a part of the base substrate 1 is removed by etching, chemical mechanical polishing (CMP), or the like to remove the base substrate 1 from the nitride semiconductor epitaxial substrate 30. 1 may be removed. In this way, a wafer in which the nitride semiconductor layer 2 and the nitride semiconductor epitaxial layer 4 are laminated as the nitride semiconductor epitaxial substrate 30 can be obtained.

  Next, functions and effects of the nitride semiconductor growth substrate 10 and the manufacturing method thereof according to the present embodiment will be described.

  The nitride semiconductor layer 2 in the nitride semiconductor growth substrate 10 according to the present embodiment is formed by irradiating the silicon nitride film 3 formed on the base substrate 1 as elements with ions under a plurality of irradiation energy conditions. Is formed. Therefore, the elements can be distributed more uniformly in the film thickness direction (depth direction) of the nitride semiconductor layer 2 than in the nitride semiconductor layer formed by irradiation under one irradiation energy condition.

  The nitride semiconductor growth substrate 10 according to the present embodiment thus obtained is, for example, compared with a conventional nitride semiconductor growth substrate in which a nitride semiconductor layer is formed only on the surface layer portion of the silicon nitride film 3. A nitride semiconductor can be epitaxially grown more densely on the second main surface 2A.

In the present embodiment, the element irradiated to the silicon nitride film 3 is only Ga, but is not limited to this. For example, the element can be selected from group III elements, and may be In or Al. Further, it may be at least one selected from the group of Ga, In, and Al. For example, irradiation may be performed by combining Al and Ga, or irradiation by combining In and Ga. In addition, what is necessary is just to irradiate each ion continuously, for example, when irradiating in combination of 2 or more types of ions. That is, after irradiating one ion under a plurality of conditions, another ion may be irradiated under a plurality of conditions. Thus, the nitride semiconductor layer 2 having a composition represented by Al _1-xy Ga _x In _y N (x ≧ 0, y ≧ 0, 0 ≦ x + y ≦ 1) can be obtained.

  In the nitride semiconductor growth substrate 10 according to the present embodiment, the base substrate 1 is a Si substrate and the first main surface 1A is the (100) plane, but this is not restrictive. For example, the base substrate may be a Si substrate, and the first main surface 1A may be a (111) surface. Further, for example, the base substrate 1 may be a synthetic quartz or a SiC substrate whose crystal polymorph is 4H—SiC. Even if it does in this way, there can exist an effect similar to the board | substrate 10 for nitride semiconductor growth which concerns on this Embodiment.

Next, Example 1 of the present embodiment will be described.
In Example 1, the influence of the ion irradiation condition of the element on the silicon nitride film on the concentration distribution of the element in the nitride semiconductor layer formed by irradiation was evaluated.

(sample)
As a base substrate, a Si substrate having a (111) plane as a first main surface, a synthetic quartz glass substrate, and a SiC substrate having a crystal polymorphism of 4H—SiC having a (0001) plane as a first main surface were prepared. . An SiN _x film was formed on these first main surfaces by MOCVD. Alternatively, the SiN _x film was formed by nitriding the first main surface at 1200 ° C. in an ammonia (NH ₃ ) atmosphere. The film thickness of the SiN _x film was three types of 5 nm, 10 nm, and 100 nm.

Next, Ga ions were irradiated to the SiN _x film (second main surface) formed on each base substrate. The irradiation conditions were performed by combining three conditions of irradiation energy of 0.5 keV, 2.0 keV, and 5.0 keV as examples (sample IDs 1 to 5). On the other hand, as comparative examples (sample IDs 6 to 12), the irradiation energy was 0.5 keV. The dose amount during ion irradiation for each sample was as shown in Table 1 below. In this manner, evaluation samples of sample IDs 1 to 5 as examples shown in Table 1 below and sample IDs 6 to 12 as comparative examples were produced.

(Evaluation method)
The evaluation sample was evaluated for Ga concentration profile using secondary ion mass spectrometry (SIMS) in a direction perpendicular to the second main surface (depth direction). Specifically, SIMS measurement was performed in the depth direction from the surface of the nitride semiconductor layer (second main surface) to the interface (first main surface) between the nitride semiconductor layer and the base substrate. Further, from the obtained concentration profile, the maximum value and the minimum value of the Ga concentration in the nitride semiconductor layer were obtained, and a value (concentration variation (%)) obtained by dividing the difference between the maximum value and the minimum value by the maximum value was calculated. .

(result)
Table 1 shows the evaluation results of sample IDs 1 to 12. FIG. 6 shows a part of the evaluation results of the concentration profile (evaluation results of sample ID1 and sample ID6). The vertical axis in FIG. 6 is the Ga concentration (unit: atoms / cc), and the horizontal axis is the depth (unit: nm) from the surface of the nitride semiconductor layer (second main surface).

First, it was confirmed that a GaN layer was formed by irradiating the SiN _x film with Ga ions. Further, it was confirmed that the Ga irradiation condition greatly affects the Ga ion concentration distribution in the GaN layer.

Specifically, the sample IDs 6 to 12 as comparative examples in which the irradiation energy of Ga ions is 0.5 keV all obtain the maximum value and the minimum value of Ga ions calculated from the concentration profile. The density variation, which is a value obtained by dividing the difference by the maximum value, was as high as 97% or more. That is, in the GaN layer of the sample of the comparative example, it was confirmed that the Ga concentration varies greatly in the depth direction. This tendency was confirmed regardless of the film thickness of the SiN _x film and the type of the underlying substrate. Furthermore, the same tendency was confirmed when the dose of Ga ions was changed. Specifically, for example, a significant difference was not confirmed in the above values between the sample ID 6 with a dose amount of 3.0 × 10 ¹⁶ cm ^{−2 and} the sample ID 8 with a dose amount of 1.2 × 10 ¹⁷ cm ⁻² . That is, irradiation of Ga ions to the sample as a comparative example is performed under one condition of irradiation energy of 0.5 keV, so that the depth of Ga is reduced for a SiN _x film having a thickness of several nm or more. It was found that it could not be introduced uniformly in the direction. That is, from the graph of FIG. 6, when a SiN _x film having a thickness of 10 nm is irradiated with Ga ions at 0.5 keV energy, the surface layer portion (about 1 nm) of the second main surface of the gallium nitride growth substrate is used. It is considered that a GaN layer is formed, but Ga ions are not sufficiently supplied to the base substrate side (5 nm to 10 nm).

On the other hand, as for the sample IDs 1 to 5 of the examples irradiated with Ga ions by combining three conditions of 0.5 keV, 2.0 keV, and 5.0 keV with respect to the irradiation energy, all of the Ga concentration calculated from the concentration profile The maximum value and the minimum value were obtained, and the concentration variation, which is a value obtained by dividing the difference between the maximum value and the minimum value by the maximum value, was 35% or less, and the value of the concentration variation was significantly lower than that of the sample of the comparative example. . This tendency was confirmed regardless of the film thickness of the SiN _x film and the type of the underlying substrate. That is, the irradiation of Ga ions on the sample of the example is performed by combining three conditions of irradiation energy of 0.5 keV, 2.0 keV, and 5.0 keV, and thus a SiN _x film having a thickness of about 10 nm or less. It was confirmed that Ga can be introduced uniformly in the depth direction.

Next, Example 2 of the present embodiment will be described.
In Example 2, the influence of the ion irradiation conditions on the silicon nitride film on the surface coverage of the nitride semiconductor epitaxial layer epitaxially grown on the nitride semiconductor layer formed by irradiation was evaluated.

(sample)
First, a nitride semiconductor growth substrate was prepared in the same manner as in Example 1. Here, the ions irradiated on the SiN _x film were single ions of In and Al, or a combination of Ga and Al, or Ga and In, in addition to Ga. Thereby, a substrate for GaN growth (sample IDs 1 to 13) including a GaN layer, a substrate for AlN growth (sample IDs 14 to 24) including an AlN layer, a substrate for InN growth (sample IDs 25 to 35) including an InN layer, and Al _{0. .5} Ga _0.5 AlGaN growth substrate (sample _ID36～46) with a N _layer, was prepared InGaN growth substrate (sample ID47～57) comprising an In 0.5 _{Ga 0.5} N layer. The conditions such as the base substrate, nitride film, and nitride film of each sample are shown in Table 1 and Tables 2 to 5 described later.

  Next, a nitride semiconductor was epitaxially grown on the second main surface of each prepared nitride semiconductor growth substrate using MOCVD, to obtain a nitride semiconductor epitaxial substrate.

(Evaluation method)
A nitride film (nitride semiconductor epitaxial layer) is obtained by obtaining an optical microscope image of the surface (third main surface) of the nitride semiconductor epitaxial substrate and performing black and white binarization on the optical microscope image. Measure the area where is growing. Then, the surface coverage of the nitride semiconductor epitaxial layer, which is the ratio of the area where the nitride film is growing to the entire third main surface, was obtained.

(result)
1. GaN epitaxial substrate (Sample ID 1-13)
The results of the surface coverage are shown in Table 1. The surface coverage of the samples of the comparative examples (sample IDs 6 to 13) is 16% or less, whereas the surface coverage of the samples of the examples (sample IDs 1 to 5) is remarkably high at 89% or more. confirmed. That is, the surface coverage of the GaN epitaxial layer is strongly influenced by the uniformity of the Ga concentration in the depth direction of the GaN layer, regardless of the thickness of the SiN _x film, the type of the underlying substrate, and the dose of Ga ions. It was confirmed. Since the sample of the example has a GaN layer having excellent Ga concentration uniformity in the depth direction, it is considered that the surface coverage of the GaN epitaxial layer could be improved. Further, there is a difference in surface coverage between the nitride semiconductor growth substrate (sample ID 6) whose base substrate is Si (111) and the nitride semiconductor growth substrate (sample ID 7) whose base substrate is Si (100). Was not seen. However, the surface coverage of the nitride semiconductor epitaxial layer depends on the plane orientation of the first main surface of the base substrate and the film formation conditions of the nitride film (GaN film in this embodiment) formed on the base substrate. May also depend.

2. AlN epitaxial substrate (sample ID 14-24)
Table 2 shows the results of surface coverage. The surface coverage of the samples of the comparative examples (sample IDs 19 to 24) is 15% or less, whereas the surface coverage of the samples of the examples (sample IDs 14 to 18) is remarkably high at 83% or more. confirmed. That is, as with the GaN epitaxial substrate described above, the surface coverage of the AlN epitaxial layer is affected by the uniformity of the Al concentration in the depth direction of the AlN layer, regardless of the thickness of the SiN _x film and the type of the underlying substrate. It was confirmed that I received strong. Further, the surface coverage of the AlN epitaxial layer did not depend on the dose amount of Al ions as in the above-described GaN epitaxial substrate. Since the sample (sample IDs 14 to 18) of the example has an AlN layer excellent in uniformity of Al concentration in the depth direction by using a plurality of irradiation energy conditions, the surface coverage of the AlN epitaxial layer is improved. It is thought that it was possible.

3. InN epitaxial substrate (Sample ID 25-35)
Table 3 shows the results of surface coverage. The surface coverage of the samples of each comparative example (sample IDs 30 to 35) is 14% or less, whereas the surface coverage of the samples of each example (sample IDs 25 to 29) is significantly higher than 77%. confirmed. That is, similarly to the GaN epitaxial substrate described above, the surface coverage of the InN epitaxial layer is affected by the uniformity of the In concentration in the depth direction of the InN layer regardless of the thickness of the SiN _x film and the type of the underlying substrate. It was confirmed that I received strong. Further, the surface coverage of the InN epitaxial layer did not depend on the dose amount of In ions, as in the GaN epitaxial substrate described above. Since the sample of the example (sample ID 25 to 29) has an InN layer having excellent uniformity of In concentration in the depth direction by using a plurality of irradiation energy conditions, the surface coverage of the InN epitaxial layer is improved. It is thought that it was possible.

4). Al _0.5 Ga _0.5 N epitaxial substrate (sample ID 36 to 46)
Table 4 shows the results of surface coverage. The surface coverage of the samples of each comparative example (sample IDs 41 to 46) is 15% or less, whereas the surface coverage of the samples of each example (sample IDs 36 to 40) is significantly higher than 85%. confirmed. That is, similarly to the above-described GaN epitaxial substrate, the surface coverage of the Al _0.5 Ga _0.5 N epitaxial layer is Al _0.5 Ga ₀ regardless of the thickness of the SiN _x film or the type of the underlying substrate. _.5 It was confirmed that the N layer was strongly influenced by the uniformity of the Al and Ga concentrations in the depth direction. Further, the surface coverage of the Al _0.5 Ga _0.5 N epitaxial layer did not depend on the total dose of Al ions and Ga ions, as with the GaN epitaxial substrate described above. Since the sample (sample ID 36 to 40) of the example has an Al _0.5 Ga _0.5 N layer excellent in uniformity of the concentration of Al and Ga in the depth direction by using a plurality of irradiation energy conditions, It is considered that the surface coverage of the Al _0.5 Ga _0.5 N epitaxial layer could be improved.

5. InGaN epitaxial substrate (sample ID 47-57)
Table 5 shows the results of surface coverage. The surface coverage of the samples of each comparative example (sample IDs 52 to 57) is 15% or less, whereas the surface coverage of the samples of each example (sample IDs 47 to 51) is remarkably high at 85% or more. confirmed. That is, similarly to the GaN epitaxial substrate described above, the surface coverage of the In _0.5 Ga _0.5 N epitaxial layer is In _0.5 Ga ₀ regardless of the thickness of the SiN _x film and the type of the underlying substrate. _.5 It was confirmed that the N layer was strongly affected by the uniformity of the In and Ga concentrations in the depth direction. Further, the surface coverage of the In _0.5 Ga _0.5 N epitaxial layer did not depend on the total dose of In ions and Ga ions, as with the GaN epitaxial substrate described above. Since the sample (sample ID 47 to 51) of the example has an In _0.5 Ga _0.5 N layer excellent in uniformity of In and Ga concentrations in the depth direction by using a plurality of irradiation energy conditions, It is considered that the surface coverage of the In _0.5 Ga _0.5 N epitaxial layer could be improved.

  Although the embodiments and examples of the present invention have been described above, various modifications can be made to the above-described embodiments and examples. Further, the scope of the present invention is not limited to the above-described embodiments and examples. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is advantageously applied to a substrate used for epitaxial growth of a nitride semiconductor.

DESCRIPTION OF SYMBOLS 1 Base substrate 1A 1st main surface 2 Nitride semiconductor layer 2A 2nd main surface 3 Silicon nitride film 3A 3rd main surface 4 Nitride semiconductor epitaxial layer 10 Nitride semiconductor growth substrate 20 Material substrate 30 Nitride semiconductor Epitaxial substrate.

Claims (4)

A base substrate;
A nitride semiconductor layer formed on the base substrate,
The nitride semiconductor layer is formed by irradiating an element as ions to a silicon nitride film formed on the base substrate,
A nitride semiconductor growth substrate, wherein, in the nitride semiconductor layer, a value obtained by dividing a difference between a maximum value and a minimum value of the element concentration in the thickness direction by the maximum value is 40% or less.   The nitride semiconductor growth substrate according to claim 1, wherein the element is at least one selected from the group consisting of gallium, indium, and aluminum. 3. The nitride semiconductor growth layer according to claim 2, wherein the composition of the nitride semiconductor layer is expressed by Al _1-xy Ga _x In _y N (x ≧ 0, y ≧ 0, 0 ≦ x + y ≦ 1). substrate.   4. The nitride semiconductor growth substrate according to claim 1, wherein the nitride semiconductor layer has a thickness of 10 nm or less. 5.

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