JP7328230B2 - Manufacturing method for semi-polar self-supporting substrate - Google Patents

Description

The present invention relates to a method for manufacturing a semi-polar free-standing substrate.

In Patent Document 1, a GaN crystal thick film is grown on a base substrate having a sapphire substrate and a GaN crystal thin film in which voids are generated at a high density. A technique for performing the same process by reusing the sapphire substrate after removal is disclosed.

In Patent Document 2, after growing a nitride semiconductor epitaxial layer on a nitride semiconductor substrate, the nitride semiconductor epitaxial layer is separated from the nitride semiconductor substrate, and then the nitride semiconductor substrate is subjected to surface treatment, A technique for performing the same process by reusing a surface-treated nitride semiconductor substrate has been disclosed.

In Patent Document 3, after forming a nitride semiconductor layer on a base substrate to which rectangular crystal pieces made of a nitride semiconductor are bonded, the nitride semiconductor layer is separated from the base substrate, and then the base substrate is reused. A technique for performing the same step is disclosed.

In Patent Document 4, after ions are implanted in the vicinity of the surface of a nitride semiconductor substrate, a silicon substrate is attached to the nitride semiconductor substrate by heat treatment, and most of the nitride semiconductor substrate bordering on the ion-implanted layer is made of silicon. A technique is disclosed in which the nitride semiconductor substrate is peeled off from the substrate and then the nitride semiconductor substrate from which the ion-implanted layer has been removed is reused to perform the same process.

In Patent Document 5, after forming an upper layer portion by stacking a plurality of nitride semiconductor layers for forming a device on a nitride semiconductor substrate, the upper layer portion is separated from the nitride semiconductor substrate, and then nitrided. A technique for performing the same process by reusing the original semiconductor substrate is disclosed.

Patent Documents 6 and 7 disclose a method of forming a Group III nitride semiconductor layer having a semipolar plane as a main surface on a sapphire substrate.

JP 2012-158497 A JP 2014-166953 A JP 2015-187043 A Japanese Patent Application Laid-Open No. 2006-210660 JP 2007-73569 A Patent No. 6266742 Patent No. 6232150

The present inventors formed a group III nitride semiconductor layer on a seed substrate made of a group III nitride semiconductor, separated the group III nitride semiconductor layer from the seed substrate to obtain a free-standing substrate, then As a result of examining the technique of performing the same process by reusing the seed substrate from which the nitride semiconductor layer was separated, the following problems were found.

Although the details will be described in the following examples, when the group III nitride semiconductor layer is formed on the seed substrate by c-plane growth in the above technique, holes and cracks are likely to occur on the surface of the group III nitride semiconductor layer. As a result, holes and cracks are likely to occur on the surface of the free-standing substrate obtained. None of Patent Documents 1 to 7 disclose the problem and its solution.

The present invention forms a group III nitride semiconductor layer on a seed substrate made of a group III nitride semiconductor, separates the group III nitride semiconductor layer from the seed substrate to obtain a self-supporting substrate, and then forms a group III nitride semiconductor layer on the seed substrate. An object of the present invention is to improve the surface condition of a self-supporting substrate obtained in a technique of reusing a seed substrate from which a semiconductor layer has been separated for the same process.

According to the invention,
a preparation step of preparing a semipolar seed substrate having a semipolar plane as a main surface and made of a group III nitride semiconductor;
a group III nitride semiconductor layer forming step of epitaxially growing a group III nitride semiconductor on the semipolar seed substrate to form a group III nitride semiconductor layer;
a cutting step of cutting out a semipolar self-supporting substrate having a semipolar plane as a main surface from the III-nitride semiconductor layer;
After the cutting step, a processing step of removing all of the group III nitride semiconductor layer from the semipolar seed substrate in which a part of the group III nitride semiconductor layer remains;
and then reusing the semipolar seed substrate from which the group III nitride semiconductor layer has been removed, and performing the group III nitride semiconductor layer forming step and the cutting step. is provided.

According to the present invention, a group III nitride semiconductor layer is formed on a seed substrate made of a group III nitride semiconductor, and the group III nitride semiconductor layer is separated from the seed substrate to obtain a free-standing substrate. In the technique of reusing the seed substrate from which the nitride semiconductor layer has been separated and carrying out the same process, the obtained self-supporting substrate has a good surface condition.

The above objectives, as well as other objectives, features and advantages, will become further apparent from the preferred embodiments described below and the accompanying drawings below.

4 is a flow chart showing an example of the process flow of the method for manufacturing a semipolar self-supporting substrate according to the present embodiment. It is process drawing which shows an example of the flow of a process of the manufacturing method of the semipolar self-standing substrate of this embodiment. It is a flow chart which shows an example of the flow of processing of a preparation process of this embodiment. It is process drawing which shows an example of the flow of a preparation process of this embodiment. It is a schematic diagram which shows an example of the semipolar seed substrate of this embodiment. It is a figure for demonstrating the structure of the semipolar seed substrate of this embodiment. It is a figure for demonstrating the structure of the semipolar seed substrate of this embodiment. 4 is a flow chart showing an example of the process flow of the method for manufacturing a semipolar self-supporting substrate according to the present embodiment. 1 is a diagram showing the surface of a semi-polar self-supporting substrate of Example 1. FIG. 4 is a diagram showing the surface of the GaN layer of Example 1. FIG. It is a figure for demonstrating the slice position of an Example. 4 is a diagram showing a sliced surface of the separated GaN layer of Example 1. FIG. 4 is a diagram showing a sliced surface of the GaN layer remaining on the semipolar seed substrate of Example 1. FIG. FIG. 2 is a diagram showing the surfaces of the semipolar seed substrate before use and the semipolar seed substrate before reuse in Example 1; FIG. 10 is a diagram showing the surface of the semipolar self-supporting substrate of Example 2; FIG. 10 is a diagram showing the surface of the GaN layer in the growth stage of Example 2; FIG. 10 is a diagram showing the surface of the GaN layer in the growth stage of Example 2; FIG. 10 is a diagram showing a sliced surface of the separated GaN layer of Example 2; FIG. 10 is a diagram showing a sliced surface of the GaN layer remaining on the semipolar seed substrate of Example 2; FIG. 10 is a diagram showing a through-hole present in the central portion of the semipolar seed substrate of Example 2; FIG. 20 is a view showing a through-hole present in the central portion of the sliced surface of the GaN layer shown in FIG. 19; 3 is a diagram showing the surface of a seed substrate of Comparative Example 1. FIG. 3 is a diagram showing the surface of a GaN layer of Comparative Example 1; FIG. FIG. 10 is a diagram showing the surface of a seed substrate of Comparative Example 2; FIG. 10 is a diagram showing the surface of a GaN layer of Comparative Example 2; FIG. 10 is a diagram showing the surface of a seed substrate of Comparative Example 3; FIG. 10 is a diagram showing the surface of a GaN layer of Comparative Example 3;

An embodiment of the method for manufacturing a semipolar self-supporting substrate of the present invention will be described below with reference to the drawings. The drawings are only schematic diagrams for explaining the configuration of the invention, and the size, shape, number, ratio of sizes of different members, etc. are not limited to those illustrated.

<First Embodiment>
"Overview and Overview"
The flowchart of FIG. 1 shows an example of the flow of processing in the method for manufacturing a semipolar self-supporting substrate according to this embodiment. As illustrated, in the method for manufacturing a semipolar self-supporting substrate of the present embodiment, a preparation step S10, a group III nitride semiconductor layer forming step S20, a cutting step S30, and a processing step S40 are performed in this order.

Here, the outline of each process is demonstrated using the process drawing of FIG.

In the preparation step S10, as shown in FIG. 2(1), a semipolar seed substrate 1 having a semipolar plane as a main surface and made of a Group III nitride semiconductor is prepared.

In the group III nitride semiconductor layer forming step S20, as shown in FIG. 2B, the group III nitride semiconductor is epitaxially grown on the semipolar seed substrate 1 to form the group III nitride semiconductor layer 2. As shown in FIG.

In the cutting step S30, as shown in FIG. 2(3), a portion of the group III nitride semiconductor layer 2 (group III nitride semiconductor layer separation portion 2-2) is separated from the semipolar seed substrate 1, A semipolar self-supporting substrate having a semipolar surface as a main surface is obtained. A plurality of semipolar self-supporting substrates may be obtained by slicing the separating portion 2-2 of the group III nitride semiconductor layer.

In the processing step S40, the semipolar seed substrate 1 in which part of the group III nitride semiconductor layer 2 (remaining portion 2-1 of the group III nitride semiconductor layer) remains is processed, and the remaining portion of the group III nitride semiconductor layer is processed. Eliminate 2-1.

Thereafter, the group III nitride semiconductor layer forming step S20 and the cutting step S30 are performed by reusing the semipolar seed substrate 1 from which the remaining portion 2-1 of the group III nitride semiconductor layer has been removed. The semipolar seed substrate 1 may be reused multiple times by further performing the processing step S40.

Next, each step will be described in detail.

"Preparation step S10"
In the preparation step S10, as shown in FIG. 2(1), a semipolar seed substrate 1 having a semipolar plane as a main surface and made of a Group III nitride semiconductor is prepared. The main surfaces of the semipolar seed substrate 1 are the {-1-12-3} plane, the plane having an off angle within 15° from the {-1-12-3} plane, the {-1-12-4} plane, Examples include {-1-12-2} planes, but are not limited to these.

In the preparation step S10, the semipolar seed substrate 1 is manufactured by executing the process shown in the flowchart of FIG. As shown in FIG. 3, in the preparation step S10, a fixing step S11, a first growth step S12, a cooling step S13, a second growth step S14, and a seed substrate cutting step S15 are performed in this order. .

In the fixing step S11, the underlying substrate is fixed to the susceptor. For example, the underlying substrate 10 as shown in FIG. 4(1) is fixed to the susceptor 20 as shown in FIG. 4(2).

Underlying substrate 10 includes group III nitride semiconductor layer 12 having a semipolar plane as a main surface. The III-nitride semiconductor layer 12 is, for example, a GaN layer.

A semipolar plane is a plane other than a polar plane and a nonpolar plane. The main surface (exposed surface in the drawing) of the group III nitride semiconductor layer 12 is represented by a +c side semipolar plane (Ga polarity side semipolar plane: Miller index (hkml), l semipolar plane on the −c side (semipolar plane on the N-polar side: semipolar plane with Miller index (hkml) and l is less than 0). good too.

The base substrate 10 may be a laminate including layers other than the group III nitride semiconductor layer 12, or may be a single layer of the group III nitride semiconductor layer 12 only. As an example of the laminate, for example, as shown in FIG. 4(1), there is a laminate in which a sapphire substrate 11, a buffer layer (not shown in the drawing), and a group III nitride semiconductor layer 12 are laminated in this order. It is exemplified, but not limited to. For example, the sapphire substrate 11 may be replaced with another heterogeneous substrate. Also, the buffer layer may not be included. Other layers may also be included.

A method for manufacturing the base substrate 10 is not particularly limited, and any technique can be adopted. For example, on a sapphire substrate 11 having a predetermined plane orientation, a group III nitride semiconductor layer 12 is formed by epitaxially growing a group III nitride semiconductor by MOCVD (metal organic chemical vapor deposition) via a buffer layer. You may In this case, the plane orientation of the main surface of the sapphire substrate 11, the presence or absence of nitriding treatment during the heat treatment performed on the sapphire substrate 11 before forming the buffer layer, the growth conditions when forming the buffer layer, and the group III The growth conditions for forming the nitride semiconductor layer 12, the process of supplying a metal-containing gas (eg, trimethylaluminum, triethylaluminum) onto the main surface of the sapphire substrate 11 to form a metal film and a metal carbide film, A Group III nitride semiconductor having a main surface that is a desired semi-polar surface on either the N-polar side or the Ga-polar side by adjusting the growth conditions and the like when forming the buffer layer and the Group III nitride semiconductor layer 12 Layer 12 can be formed. Details are disclosed in Patent Documents 6 and 7.

As another example of the method for manufacturing the base substrate 10, a Group III nitride semiconductor layer obtained by growing the c-plane is processed (eg, sliced, etc.) to form a Group III nitride having a desired semipolar plane as a main surface. A semiconductor layer (underlying substrate 10) may be obtained.

The maximum diameter of the group III nitride semiconductor layer 12 is, for example, Φ50 mm or more and Φ6 inches or less. The thickness of the group III nitride semiconductor layer 12 is, for example, 50 nm or more and 1 mm or less. The diameter of the sapphire substrate 11 is, for example, Φ50 mm or more and Φ6 inches or less. The thickness of the sapphire substrate 11 is, for example, 100 μm or more and 10 mm or less.

Next, the susceptor 20 will be explained. The susceptor 20 has characteristics such as not being deformed by the stress of the underlying substrate 10 that may warp due to heating in the first growth step S12 or the second growth step S14. Examples of such a susceptor 20 include, but are not limited to, carbon susceptors, silicon carbide-coated carbon susceptors, boron nitride-coated carbon susceptors, and quartz susceptors.

Next, a method for fixing the underlying substrate 10 to the susceptor 20 will be described. In this embodiment, as shown in FIG. 4B, the rear surface of the underlying substrate 10 (the rear surface of the sapphire substrate 11) is fixed to the surface of the susceptor 20. As shown in FIG. This suppresses deformation of the underlying substrate 10 . As a method for fixing, a method is required that does not separate due to the heating in the first growth step S12 or the second growth step S14 or the warping force of the base substrate 10 that can warp due to the heating. For example, a method of fixing using an adhesive such as an alumina-based, carbon-based, zirconia-based, silica-based, or nitride-based adhesive is exemplified.

Returning to FIG. 3, in the first growth step S12, as shown in FIG. 4(3), HVPE (HVPE) is formed on the main surface of the group III nitride semiconductor layer 12 while the underlying substrate 10 is fixed to the susceptor 20. Hydride Vapor Phase Epitaxy) to grow a Group III nitride semiconductor. As a result, the first growth layer 30 composed of a single-crystal Group III nitride semiconductor is formed. For example, GaN is epitaxially grown under the following growth conditions to form a GaN layer (first growth layer 30).

Growth temperature: 900°C to 1100°C
Growth time: 1h to 50h
V/III ratio: 1-20
Growth film thickness: 100 μm to 10 mm

In the first growth step S<b>12 , a polycrystalline Group III nitride semiconductor is formed along the side surfaces of the laminate including the susceptor 20 , base substrate 10 and first growth layer 30 . A polycrystalline Group III nitride semiconductor adheres to all or most of the side surfaces of the stack. The adhered polycrystalline group III nitride semiconductors are connected to each other to form a ring. The laminate is held inside the ring-shaped polycrystalline Group III nitride semiconductor.

In addition, in the first growth step S12, a polycrystalline Group III nitride semiconductor can be formed not only on the side surfaces of the laminate but also on the back surface of the susceptor 20. FIG. The polycrystalline Group III nitride semiconductor adheres to all or most of the side surfaces of the stack and the back surface of the susceptor 20 . The adhered polycrystalline group III nitride semiconductors are connected to each other to form a cup-like shape. The laminate is held inside the cup-shaped polycrystalline Group III nitride semiconductor.

Returning to FIG. 3, in the cooling step S13, the laminate including the susceptor 20, the base substrate 10 and the first growth layer 30 is cooled. The purpose of the cooling here is to generate cracks in the first growth layer 30 by utilizing strain (stress) generated due to the difference in linear expansion coefficient between the first growth layer 30 and the sapphire substrate 11 . and to relieve stress. It is desirable to relax the stress before the second growth step S14. The cooling method is not particularly limited as long as the object can be achieved. For example, after the first growth step S12, the laminate may be temporarily removed from the HVPE apparatus and cooled to room temperature.

As shown in FIG. 4C, cracks (fissures, fissures, etc.) 31 are present in the first growth layer 30 after the cooling step S13. Cracks 31 may be present on the surface of the first growth layer 30 as shown. The cracks 31 may be generated during the first growth step S12 or may be generated during the cooling step S13.

Returning to FIG. 3, in the second growth step S14, as shown in FIG. 4(4), with the base substrate 10 fixed to the susceptor 20, a III growth layer is formed on the first growth layer 30 by the HVPE method. to grow a group nitride semiconductor. As a result, the second growth layer 40 composed of the single-crystal Group III nitride semiconductor is formed. For example, GaN is epitaxially grown under the following growth conditions to form a GaN layer (second growth layer 40). The growth conditions for forming the first growth layer 30 and the growth conditions for forming the second growth layer 40 may be the same or different.

Growth temperature: 900°C to 1100°C
Growth time: 1h to 50h
V/III ratio: 1-20
Growth film thickness: 100 μm to 10 mm

In the second growth step S14, the second growth layer 40 is formed on the first growth layer 30 while leaving the annular polycrystalline Group III nitride semiconductor formed in the first growth step S12. Form. The purpose of leaving the ring-shaped polycrystalline group III nitride semiconductor is to suppress the separation by holding the first growth layer 30, which may be separated into a plurality of parts due to the cracks 31, from the outer periphery. . If the first growth layer 30 is separated into a plurality of portions, the misalignment of plane orientation, handleability, workability, and the like for each of the plurality of portions are deteriorated. There is also the risk that some parts will be missing or shattered, making it impossible to reproduce the original shape. According to the present embodiment, it is possible to suppress the deviation of the plane orientation and the separation, so that the inconvenience can be suppressed.

Although the entire polycrystalline group III nitride semiconductor formed in the first growth step S12 may be left as it is, it is sufficient if the above purpose can be achieved, and the polycrystalline group III nitride semiconductor formed in the first growth step S12 does not necessarily need to be left as it is. It is not necessary to leave all of the crystalline Group III nitride semiconductor. That is, part of the polycrystalline Group III nitride semiconductor may be removed.

A polycrystalline Group III nitride semiconductor is also formed in the second growth step S14. The polycrystalline III-nitride semiconductor can be formed along the side surfaces of the laminate including the susceptor 20 , the base substrate 10 , the first growth layer 30 and the second growth layer 40 and the back surface of the susceptor 20 .

Further, in the second growth step S14, a group III nitride semiconductor is grown by HVPE on the surface of the first growth layer 30 where the cracks 31 are present to form the second growth layer 40. FIG. In this case, the growth surface (the surface of the first growth layer 30) becomes discontinuous at the crack 31 portion. Group III nitride semiconductor grown from each of the first surface region and the second surface region separated from each other by the crack 31 joins and integrates as the growth progresses.

Returning to FIG. 3 , in the seed substrate cutting step S<b>15 , at least part of the second growth layer 40 is cut out as the semipolar seed substrate 1 .

For example, as shown in FIG. 4(5), at least a portion of the second growth layer 40 is obtained by slicing the laminate including the susceptor 20, the base substrate 10, the first growth layer 30 and the second growth layer 40. is separated from the susceptor 20 to form the semipolar seed substrate 1 . At least part of the second growth layer 40 separated from the susceptor 20 may be sliced to obtain a plurality of semipolar seed substrates 1 . At least part of the second growth layer 40 may be separated from the susceptor 20 by using a method such as grinding, polishing, burning, decomposition, or dissolution, in addition to slicing.

As described above, a semipolar seed substrate 1 having a semipolar plane as a main surface and made of a Group III nitride semiconductor is obtained.

According to the preparation step S10, the second growth layer 40 can be formed by epitaxially growing a semiconductor on the stress-relaxed first growth layer 30 (second growth step S14). Therefore, the second growth layer 40 is less prone to cracks and breakages than when the first growth layer 30 is made thicker to have the same thickness without relaxing the stress.

Therefore, according to the preparatory step S10, it is possible to grow a thick film of a Group III nitride semiconductor having a semipolar plane as a main surface and a sufficient diameter. As a result, a bulk crystal including the first grown layer 30 and the second grown layer 40 is obtained. For example, the film thickness of the second growth layer 40 is 500 μm or more and 20 mm or less, and the maximum diameter is Φ50 mm or more and Φ6 inches or less. Also, the film thickness of the first growth layer 30 is 100 μm or more and 10 mm or less. The total thickness of the first growth layer 30 and the second growth layer 40 is 600 μm or more and 30 mm or less. The surface of the second growth layer 40 is uneven and has m-plane facets.

According to the preparatory step S10 capable of manufacturing a bulk crystal with a sufficient diameter and a sufficient film thickness as described above, by cutting out a part (group III nitride semiconductor layer) from the bulk crystal, a semipolar plane main surface, and the semipolar seed substrate 1 having a sufficient diameter and thickness can be efficiently manufactured. For example, the maximum diameter of the semi-polar seed substrate 1 is Φ50 mm or more and Φ6 inches or less, and the thickness of the semi-polar seed substrate 1 is 100 μm or more and 10 mm or less.

Cracks 31 are generated in the first grown layer 30 when the stress is relaxed. The second growth layer 40 grown on such a first growth layer 30 has a first surface region and a second surface region of the first growth layer 30 separated from each other by the cracks 31. Crystals grown from each are formed by bonding to each other. Here, dislocations can occur on the interface between the first surface region and the second surface region. When the plane orientations of the first surface region and the second surface region are misaligned, dislocations on the interface increase. In this embodiment, the first growth layer 30 is held from the outer periphery by the ring-shaped polycrystalline Group III nitride semiconductor. Therefore, it is possible to suppress the deviation of the plane orientation. As a result, an increase in dislocations on the interface can be suppressed.

In addition, according to the preparation step S10 in which the first growth step S12 and the cooling step S13 are performed while the base substrate 10 is constrained by the susceptor 20, compared to the case where the same processing is performed without the constraint, the The number of cracks 31 generated in one growth layer 30 can be reduced.

Further, according to the preparatory step S10 in which the second growth step S14 is performed while the laminate including the underlying substrate 10 and the first growth layer 30 is constrained by the susceptor 20, the same process can be performed without the constraint. The number of cracks generated in the first growth layer 30 and the second growth layer 40 can be reduced and the separation can be suppressed as compared with the case of performing this.

Moreover, according to the preparation step S10, as shown in FIGS. A structured semipolar seed substrate 1 can be manufactured. FIGS. 5(1) and 5(2) are plan views of the semipolar seed substrate 1, showing the main surface.

The second portion 52 is attached to the outer circumference of the first portion 51 . The second portion 52 is annular and holds the first portion 51 inside it. The second portion 52 may be left as it is in a randomly attached state as shown in FIG. 5(1), or may be trimmed by polishing, grinding, or the like as shown in FIG. 5(2).

According to the semipolar seed substrate 1 of this embodiment, the diameter can be increased by the second portion 52 . As a result, handleability and workability are improved, and when the semipolar seed substrate 1 is used as a seed substrate, a large growth area for the first portion 51 made of a single crystal can be ensured. For example, the maximum diameter of the first portion 51 is Φ50 mm or more and Φ6 inches or less, and the maximum diameter of the group III nitride semiconductor layer having the first portion 51 and the second portion 52 is Φ51 mm or more and Φ6.5 inches or less. be.

Alternatively, the second portion 52 made of polycrystal may be removed to obtain the semipolar seed substrate 1 consisting only of the first portion 51 made of single crystal.

Further, according to the preparatory step S10 of the present embodiment, as shown in FIGS. 6 and 7, the semipolar seed substrate 1 including a plurality of portions with mutually different crystal axis orientations is manufactured. 7 is a cross-sectional view taken along line AA' of FIG. 6. FIG. Regions A and B shown in the figure are portions grown from the first surface region and the second surface region of the first grown layer 30 separated from each other by the crack 31 .

The crystals in the region A and the region B have their crystal axes misaligned between the first surface region and the second surface region of the first growth layer 30 (misalignment caused by the cracks 31). different orientations. The crystal axis direction Y of the illustrated region A and the crystal axis direction Z of the region B indicate the same crystal axis direction. The feature is a feature appearing in the semi-polar seed substrate 1 manufactured in the preparatory step. As described above, in the present embodiment, the presence of the ring-shaped polycrystalline Group III nitride semiconductor that holds the first growth layer 30 from the outer periphery can suppress the deviation of the plane orientation. As a result, the angle formed by the crystal axis direction Y of the region A and the crystal axis direction Z of the region B can be suppressed to 2° or less.

In addition, in the preparation step S10, the semipolar seed substrate 1 may be manufactured by a process different from the process shown in the flowchart of FIG. For example, in the preparation step S10, the semipolar seed substrate 1 may be manufactured by slicing the c-plane grown group III nitride semiconductor bulk crystal so that the slice planes are semipolar planes.

"Group III nitride semiconductor layer forming step S20"
Returning to FIG. 1, in the group III nitride semiconductor layer forming step S20, as shown in FIG. 2B, a group III nitride semiconductor is epitaxially grown on the semipolar seed substrate 1 to form a group III nitride semiconductor layer 2 is formed. For example, a group III nitride semiconductor (eg, GaN) is grown on the main surface of the semipolar seed substrate 1 by HVPE to form the group III nitride semiconductor layer 2 . The growth conditions are as follows.

Growth temperature: 900°C to 1100°C
Growth time: 1h to 50h
V/III ratio: 1-20
Growth film thickness: 100 μm to 20 mm

"Cut-out step S30"
Returning to FIG. 1 , in the cutting step S<b>30 , a semipolar self-supporting substrate having a semipolar plane as a main surface is cut out from the group III nitride semiconductor layer 2 .

For example, in the slicing step S30, as shown in FIG. 2(3), the layered body composed of the semi-polar substrate 1 and the group III nitride semiconductor layer 2 is sliced, and the semi-polar substrate 1 is sliced into group III nitride semiconductors. By separating a part of the layer 2 (separating part 2-2 of the group III nitride semiconductor layer), a semipolar self-supporting substrate having a semipolar plane as a main surface can be obtained. A plurality of semipolar self-supporting substrates may be obtained by slicing the separating portion 2-2 of the group III nitride semiconductor layer. The slicing position for obtaining the separating portion 2-2 of the group III nitride semiconductor layer is, for example, the group III nitride semiconductor layer along the stacking direction from the interface between the semipolar seed substrate 1 and the group III nitride semiconductor layer 2. 2, but not limited to this.

The plane orientation of the main surface of the semipolar self-supporting substrate may be the same as the plane orientation of the main surface of the semipolar seed substrate 1 . In addition, the plane orientation of the main surface of the semipolar self-supporting substrate may be different from the plane orientation of the main surface of the semipolar seed substrate 1 . Both can be realized by adjusting the inclination of the slice plane in the slice. For example, when the main surface of the semipolar seed substrate 1 is a plane having an off angle within 15° from the {hklm} plane (eg, {-1-12-3} plane), the main surface of the semipolar self-supporting substrate is It may be a {hklm} plane.

Incidentally, as shown in FIG. 2(3), after a part of the group III nitride semiconductor layer 2 (separation part 2-2 of the group III nitride semiconductor layer) is separated from the semipolar seed substrate 1, group III nitriding is performed. Another portion of the compound semiconductor layer 2 (remaining portion 2 - 1 of the group III nitride semiconductor layer) remains on the semipolar seed substrate 1 .

"Processing step S40"
Returning to FIG. 1, the processing step S40 is performed after the cutting step S30 and before performing the Group III nitride semiconductor layer forming step S20 by reusing the semi-polar seed substrate 1 . In the processing step S40, all of the group III nitride semiconductor layer 2 is removed from the semi-polar seed substrate 1 in which part of the group III nitride semiconductor layer 2 (separating portion 2-2 of the group III nitride semiconductor layer) remains. . For example, the III-nitride semiconductor layer 2 can be removed from the semipolar substrate 1 by polishing.

In the processing step S<b>40 , a part of the surface of the semipolar seed substrate 1 that is in contact with the Group III nitride semiconductor layer 2 may be removed. By doing so, the removal of the entire group III nitride semiconductor layer 2 can be reliably achieved.

In addition, the processing step S40 may include a process of confirming that the entire group III nitride semiconductor layer 2 has been removed from the semi-polar seed substrate 1 by observing the surface. Surface observation here is, for example, surface observation by SEM (Scanning Electron microscope)/CL (Cathodoluminescence).

After the processing step S40, the group III nitride semiconductor layer forming step S20 and the cutting step S30 are performed by reusing the semi-polar seed substrate 1 from which the group III nitride semiconductor layer 2 has been completely removed. After performing the group III nitride semiconductor layer forming step S20 and the cutting step S30 by reusing the semipolar seed substrate 1, the processing step S40 is further performed to reuse the semipolar seed substrate 1 a plurality of times. may For example, the upper limit of the number of times of repeated use (for example, about 5 times) may be set in advance, and the reuse of the semipolar seed substrate 1 may be terminated when the number of times is reached.

Next, the effects of the method for manufacturing a semipolar self-supporting substrate according to this embodiment will be described. In the method for producing a semipolar self-supporting substrate according to the present embodiment, a group III nitride semiconductor layer 2 is formed on a semipolar seed substrate 1 made of a group III nitride semiconductor having a semipolar plane as a main surface, and a semipolar seed After separating the group III nitride semiconductor layer 2 from the substrate 1 to obtain a semipolar self-supporting substrate, the semipolar seed substrate 1 from which the group III nitride semiconductor layer 2 was separated is reused to perform the same process. By reusing the semipolar seed substrate 1, a cost advantage can be produced.

Further, as will be shown in the following examples, when a group III nitride semiconductor layer is formed on a seed substrate having a c-plane as a principal plane, with the c-plane as the growth plane, a through hole is formed on the surface of the obtained group III nitride semiconductor layer. Holes and cracks are more likely to occur. As a result, through-holes and cracks are likely to occur on the surface of the free-standing substrate obtained.

On the other hand, according to the manufacturing method of the present embodiment, in which the group III nitride semiconductor layer 2 is formed on the semipolar seed substrate 1 having the semipolar plane as the main surface and the semipolar plane as the growth plane, the above c-plane growth is achieved. As compared with the example of (2), through-holes and cracks are less likely to occur on the surface of the group III nitride semiconductor layer 2 to be obtained. As a result, through-holes and cracks are less likely to occur on the surface of the resulting semipolar self-supporting substrate. That is, according to the method for manufacturing a semipolar self-supporting substrate of the present embodiment, it is possible to manufacture a semipolar self-supporting substrate having a good surface condition.

In addition, according to the method for manufacturing a semipolar self-supporting substrate of the present embodiment, a semipolar self-supporting substrate having a semipolar surface as the main surface can be manufactured, so that the internal quantum efficiency of a device formed on the self-supporting substrate can be improved. is realized.

Further, according to the method for manufacturing a semipolar self-supporting substrate of the present embodiment in which the group III nitride semiconductor layer 2 is completely removed from the semipolar seed substrate 1 before reuse, III in the group III nitride semiconductor layer forming step S20 In the growth of a group nitride semiconductor, the probability of occurrence of defects such as local strain, abnormal growth, and crystal defects can be reduced. That is, a high-quality semipolar self-supporting substrate can be manufactured.

<Second embodiment>
The flow chart of FIG. 8 shows an example of the process flow of the method for manufacturing a semipolar free-standing substrate according to this embodiment. As illustrated, in the method for manufacturing a semipolar self-supporting substrate of the present embodiment, a preparation step S10, a group III nitride semiconductor layer forming step S20, a cutting step S30, a processing step S40, and a determination step S50. performed in this order.

This embodiment differs from the first embodiment in that it has a judgment step S50. The preparation step S10, the group III nitride semiconductor layer formation step S20, the cutting step S30, and the processing step S40 are the same as in the first embodiment.

Although not shown, the judgment step S50 may be performed after the cutting step S30 and before the machining step S40 instead of after the machining step S40. In addition, the determination step S50 may be performed both after the cutting step S30 and before the processing step S40 and after the processing step S40.

By performing the determination step S50 after the cutting step S30 and before the processing step S40, the inconvenience of performing the processing step S40 on the non-reusable semi-polar seed substrate 1 can be suppressed. Further, by performing the determination step S50 after the processing step S40, it is possible to determine whether or not the semi-polar seed substrate 1 can be reused in consideration of the influence of the processing step S40. The determination step S50 will be described below.

"Judgment step S50"
In the determination step S50, it is determined whether or not the semipolar seed substrate 1 is reusable. If it is determined that the semipolar seed substrate 1 is reusable in the determination step S50, the semipolar seed substrate 1 is reused. That is, the Group III nitride semiconductor layer 2 is formed on the semipolar seed substrate 1 , and the semipolar self-supporting substrate is cut out from the Group III nitride semiconductor layer 2 . On the other hand, if it is determined that the semipolar seed substrate 1 cannot be reused in the determination step S50, the reuse of the semipolar seed substrate 1 is terminated.

A specific example of the determination method will be described below.

In the first example, based on the radius of curvature of the semipolar seed substrate 1, it is determined whether or not it is reusable. Specifically, when the radius of curvature of the semipolar seed substrate 1 is equal to or greater than the reference value, it is determined that the substrate can be reused, and when the radius of curvature of the semipolar seed substrate 1 is less than the reference value, it is determined that the substrate cannot be reused. .

If the warp of the semipolar seed substrate 1 becomes too large, the obtained semipolar self-supporting substrate will also warp greatly, and problems such as cracks may occur. By determining whether or not the substrate is reusable based on the radius of curvature, it is possible to prevent the inconvenience of manufacturing a semipolar self-supporting substrate that is unsuitable as a product. Although the reference value of the curvature radius is, for example, 1 m, it can be appropriately set according to this.

When performing the determination step S50 after the cutting step S30 and before the processing step S40, the off angle with respect to the main surface is measured by an energy dispersive X-ray diffraction (EDXRD) method, and the radius of curvature is calculated from the obtained data. can do. Measurement by the X-ray rocking curve method is also possible, but it is not preferable because cutting damage occurs in the cut surface of the crystal in the cutting step S30, making accurate measurement difficult.

On the other hand, when the judgment step S50 is performed after the processing step S40, the cutting damage of the crystal surface is removed by the processing step S40, so the radius of curvature is can be measured with high precision.

Thus, by selecting an appropriate method according to the timing of performing the determination step S50, the state of the semipolar seed substrate 1 can be evaluated appropriately.

In the second example, it is determined whether or not the semipolar seed substrate 1 is reusable based on whether or not a predetermined crack has occurred. Specifically, if the semipolar seed substrate 1 does not have a predetermined crack, it is determined to be reusable, and if the semipolar seed substrate 1 has a predetermined crack, it is determined not to be reusable. . A predetermined crack is, for example, a crack having a predetermined reference length or longer. The reference length may be "50% or more of the diameter of the semipolar seed substrate 1" or may be defined as "XX cm or more".

If a long crack exists in the semipolar seed substrate 1, it adversely affects the crystallinity of the group III nitride semiconductor layer 2 formed thereon. By determining whether or not the substrate is reusable based on whether or not a predetermined crack has occurred, it is possible to prevent the inconvenience of manufacturing a semipolar self-supporting substrate that is unsuitable as a product.

In the third example, based on the thickness of the semipolar seed substrate 1, it is determined whether or not it can be reused. Specifically, when the thickness of the semi-polar seed substrate 1 is equal to or greater than the reference value, it is determined that it can be reused, and when the thickness of the semi-polar seed substrate 1 is less than the reference value, it is determined that it cannot be reused. .

As described in the first embodiment, in the processing step S40, the surface side of the semipolar seed substrate 1 in contact with the group III nitride semiconductor layer 2 is removed in order to reliably remove all of the group III nitride semiconductor layer 2. can be removed. In such a case, the semipolar seed substrate 1 becomes thinner due to the partial removal of the semipolar seed substrate 1 .

If the semipolar seed substrate 1 becomes too thin, the semipolar seed substrate 1 and the group III nitride semiconductor layer 2 formed thereon are likely to be warped or cracked. By judging whether or not the substrate is reusable based on the thickness, it is possible to prevent the inconvenience of producing a semipolar self-supporting substrate that is unsuitable as a product. Although the reference value of the thickness is, for example, 250 μm, it can be appropriately set according to this.

In the fourth example, based on the surface roughness of the semipolar seed substrate 1, it is determined whether or not it can be reused. Specifically, when the surface roughness of the semi-polar seed substrate 1 is less than the reference value, it is determined that it can be reused, and when the surface roughness of the semi-polar seed substrate 1 is equal to or greater than the reference value, it is determined that it cannot be reused. to decide.

If the surface roughness of the semipolar seed substrate 1 becomes too rough, the crystallinity of the semipolar seed substrate 1 and the group III nitride semiconductor layer 2 formed thereon are likely to be impaired. By judging whether or not the substrate is reusable based on the surface roughness, it is possible to prevent the inconvenience of producing a semipolar self-supporting substrate that is unsuitable as a product. The reference value of the surface roughness is, for example, the surface roughness RMS of 5×5 μm ² is 0.5 nm or more and 5 nm or less, but it can be appropriately set according to this.

In the fifth example, based on the presence or absence of scratches on the surface of the semipolar seed substrate 1, it is determined whether or not the substrate is reusable. Specifically, if the surface of the semi-polar seed substrate 1 is not damaged, it is determined that it can be reused, and if the surface of the semi-polar seed substrate 1 is damaged, it is determined that it cannot be reused. .

Due to the use of the semi-polar seed substrate 1, the execution of the processing step S40, etc., there is a possibility that the surface of the semi-polar seed substrate 1 will have polishing marks or scratches. If the surface of the semipolar seed substrate 1 has polishing marks or scratches, the crystallinity of the group III nitride semiconductor layer 2 formed thereon is adversely affected. By determining whether or not the semipolar seed substrate 1 is reusable based on the presence or absence of scratches on the surface of the semipolar seed substrate 1, it is possible to prevent the inconvenience of manufacturing a semipolar self-supporting substrate that is unsuitable as a product. Inspection for confirming the presence or absence of scratches can be realized by optical microscope observation, SEM/CL, or the like.

According to the method for manufacturing a semipolar self-supporting substrate of the present embodiment described above, the same effects as those of the first embodiment can be achieved. Further, according to the manufacturing method of the semipolar self-supporting substrate of the present embodiment, in which the semipolar seed substrate 1 is reused after appropriately determining whether or not the semipolar seed substrate 1 is reusable, the state failure of the semipolar seed substrate 1 causes , the inconvenience of manufacturing a semipolar self-supporting substrate that is unsuitable as a product can be suppressed.

<Example>
"Example 1"
FIG. 9 shows the semipolar seed substrate 1 of Example 1. As shown in FIG. The semipolar seed substrate 1 of Example 1 is made of GaN, and has a crack (a crack extending vertically in the drawing and located near the outer periphery of the substrate), but does not have a through hole. The plane orientation of the main surface was the {-1-12-3} plane inclined 9° toward the m-plane and 3° towards the c-plane, the diameter was Φ60 mm, and the thickness was 800 μm.

GaN was epitaxially grown on the semipolar seed substrate 1 under the following growth conditions to form a GaN layer (III-nitride semiconductor layer 2).

Growth method: HVPE method Growth temperature: 1040°C
V/III ratio: 2000/200
Total gas flow rate: 10314sccm
Impurities: undoped Growth time: 12 hours

10 shows the surface of the GaN layer of Example 1. FIG. No through holes or cracks were present on the surface of the GaN layer. That is, the GaN layer could be formed without generating new through holes or cracks. Moreover, the cracks existing on the surface of the semipolar seed substrate 1 disappeared on the surface of the GaN layer.

After the GaN layer was formed, as shown in FIG. 11, it was sliced at a position shifted 300 μm from the interface between the semipolar seed substrate 1 and the GaN layer along the stacking direction toward the GaN layer (upward in the figure). , separated the semipolar seed substrate 1 and part of the GaN layer. As shown in the figure, the central portion of the GaN layer had a thickness of 2500 μm, and the outermost peripheral portion thereof had a thickness of 1550 μm.

FIG. 12 shows a slice plane of the separated GaN layer. A circle in the drawing indicates a circle of Φ50 mm. FIG. 13 shows a sliced surface of the GaN layer remaining on the semipolar seed substrate 1 . As shown in FIGS. 12 and 13, neither through-holes nor cracks were observed inside the GaN layer.

FIG. 14 shows a semipolar seed substrate 1 (starting substrate) before forming and separating the GaN layer, and a semipolar seed substrate 1 (starting substrate) from which the GaN layer was removed by polishing after forming and separating the GaN layer. The surface of the recycled substrate) is shown. It was confirmed that the semi-polar seed substrate 1 can be reused without causing scratches or the like on the surface even if the above steps are performed.

"Example 2"
FIG. 15 shows the semipolar seed substrate 1 of Example 2. As shown in FIG. The semipolar seed substrate 1 of Example 2 is made of GaN, has cracks in part, and has through holes. In the drawing, circles indicate through holes. The plane orientation of the main surface was the {-1-12-3} plane inclined 9° toward the m-plane and 3° towards the c-plane, the diameter was Φ60 mm, and the thickness was 800 μm.

GaN was epitaxially grown on the semipolar seed substrate 1 to form a GaN layer (group III nitride semiconductor layer 2). The growth conditions are the same as in Example 1, except that growth was performed twice for 20 hours.

FIG. 16 shows the surface of the GaN layer when the thickness of the central portion of the laminate including the semipolar seed substrate 1 and the GaN layer is 6 mm. FIG. 17 shows the surface of the GaN layer when the film thickness at the central portion of the laminate is 12.8 mm. In either case, no new through-holes or cracks that do not exist in the semipolar seed substrate 1 were generated.

Then, in the same manner as in Example 1, the semipolar seed substrate 1 and the GaN layer were sliced at a position shifted 300 μm from the interface between the semipolar seed substrate 1 and the GaN layer along the stacking direction toward the GaN layer (upward in the figure). The substrate 1 and part of the GaN layer were separated.

FIG. 18 shows a slice plane of the separated GaN layer. No through-holes or cracks were present on the sliced surface of FIG. That is, the through holes and cracks (see FIG. 15) existing in the semipolar seed substrate 1 disappeared.

FIG. 19 shows a sliced surface of the GaN layer remaining on the semipolar seed substrate 1 . A through hole was present in the center (marked with a circle in the figure), but no other through holes or cracks were present. That is, of the through-holes and cracks (see FIG. 15) existing in the semipolar seed substrate 1, the central through-hole remained, but the other through-holes and cracks disappeared.

FIG. 20 shows an optical microscopic image of the through hole existing in the center of the semipolar seed substrate 1 . FIG. 21 shows an optical microscopic image of a through-hole present at the center of the sliced surface of the GaN layer shown in FIG. Note that the unit of numbers indicating lengths in FIGS. 20 and 21 is “μm”. From the figure, it can be seen that the width and length of the through-holes become smaller as the distance from the semipolar seed substrate 1 increases (as the group III nitride semiconductor forming the group III nitride semiconductor layer 2 grows). That is, it was confirmed that by growing the group III nitride semiconductor on the semipolar seed substrate 1, the through holes existing in the semipolar seed substrate 1 can be made smaller and the cracks can be eliminated. The <000-2> projection axis in the figure indicates the direction of the axis obtained by projecting <000-2> onto the main surface of the semipolar seed substrate 1 . Similarly, the <10-10> projection axis in the figure indicates the direction of the axis obtained by projecting <10-10> onto the main surface of the semipolar seed substrate 1 .

"Comparative Example 1"
22 shows the seed substrate of Comparative Example 1. FIG. The seed substrate of Comparative Example 1 is made of GaN and has through holes. In the drawing, circles indicate through holes. The main surface was the c-plane, the diameter was Φ50 mm, and the thickness was 400 μm.

GaN was epitaxially grown on the seed substrate to form a GaN layer. The growth conditions were the same as in Example 1, except that the growth time was 20 hours and Si doping was performed.

FIG. 23 shows the surface of the GaN layer. It can be seen that the through-holes present on the seed substrate also exist in the GaN layer. And it can be confirmed that the through-holes in the GaN layer are larger than the through-holes on the seed substrate.

"Comparative Example 2"
FIG. 24 shows the seed substrate of Comparative Example 2. As shown in FIG. The seed substrate of Comparative Example 2 is made of GaN and has an opening that does not penetrate to the back surface. The main surface was the c-plane, the diameter was Φ50 mm, and the thickness was 400 μm.

GaN was epitaxially grown on the seed substrate to form a GaN layer. The growth conditions were the same as in Example 1, except that the growth time was 20 hours.

FIG. 25 shows the surface of the GaN layer. It can be confirmed that there are new through holes in the GaN layer that were not present on the seed substrate (indicated by circles in the figure).

"Comparative Example 3"
FIG. 26 shows the seed substrate of Comparative Example 3. As shown in FIG. The seed substrate of Comparative Example 3 is made of GaN and has an opening hole that does not penetrate to the back surface. The main surface was the c-plane, the diameter was Φ54 mm, and the thickness was 1.4 mm.

GaN was epitaxially grown on the seed substrate to form a GaN layer. The growth conditions were the same as in Example 1, except that the growth time was 21 hours.

FIG. 27 shows the surface of the GaN layer. It can be confirmed that cracks that were not present on the seed substrate exist in the GaN layer. In addition, the presence of through-holes that were not on the seed substrate, the remaining through-holes that were on the seed substrate, and the expansion of the through-holes can be confirmed.

Examples of reference forms are added below.
1. a preparation step of preparing a semipolar seed substrate having a semipolar plane as a main surface and made of a group III nitride semiconductor;
a group III nitride semiconductor layer forming step of epitaxially growing a group III nitride semiconductor on the semipolar seed substrate to form a group III nitride semiconductor layer;
a cutting step of cutting out a semipolar self-supporting substrate having a semipolar plane as a main surface from the III-nitride semiconductor layer;
After the cutting step, a processing step of removing all of the group III nitride semiconductor layer from the semipolar seed substrate in which a part of the group III nitride semiconductor layer remains;
and then reusing the semipolar seed substrate from which the group III nitride semiconductor layer has been removed, and performing the group III nitride semiconductor layer forming step and the cutting step. .
2. 1. In the method for producing a semipolar self-supporting substrate according to 1,
The method for manufacturing a semipolar self-supporting substrate, wherein in the processing step, a part of a surface of the semipolar seed substrate that is in contact with the group III nitride semiconductor layer is removed.
3. In the method for manufacturing a semipolar self-supporting substrate according to 1 or 2,
The method for manufacturing a semipolar self-supporting substrate, wherein, in the processing step, removal of all the group III nitride semiconductor layers is confirmed by surface observation.
4. In the method for manufacturing a semipolar self-supporting substrate according to any one of 1 to 3,
further comprising a determining step of determining whether the semipolar seed substrate is reusable;
Reusing the semipolar seed substrate if it is determined to be reusable in the determination step,
A method for manufacturing a semipolar self-supporting substrate, wherein the reuse of the semipolar seed substrate is terminated when it is determined in the determining step that the semipolar seed substrate cannot be reused.
5. 4. In the method for producing a semipolar self-supporting substrate according to 4,
In the determining step, when the radius of curvature of the semi-polar seed substrate is equal to or greater than a reference value, it is determined that the substrate is reusable, and when the radius of curvature of the semi-polar seed substrate is less than the reference value, it is determined that the substrate is not reusable. A method for manufacturing a semi-polar free-standing substrate.
6. 4. In the method for producing a semipolar self-supporting substrate according to 4,
In the determining step, it is determined that the semi-polar seed substrate is reusable when the predetermined crack has not occurred in the semi-polar seed substrate, and it is determined that the semi-polar seed substrate is not reusable when the predetermined crack has occurred in the semi-polar seed substrate. A method for manufacturing a semi-polar free-standing substrate.
7. 4. In the method for producing a semipolar self-supporting substrate according to 4,
In the determining step, when the thickness of the semi-polar seed substrate is equal to or greater than a reference value, it is determined that the substrate is reusable, and when the thickness of the semi-polar seed substrate is less than the reference value, it is determined that the substrate is not reusable. A method for manufacturing a semi-polar free-standing substrate.
8. 4. In the method for producing a semipolar self-supporting substrate according to 4,
In the determination step, if the surface roughness of the semi-polar seed substrate is less than a reference value, it is determined that the substrate can be reused, and if the surface roughness of the semi-polar seed substrate is equal to or greater than the reference value, it is determined that the substrate cannot be reused. A method for manufacturing a semi-polar free-standing substrate to determine.
9. 4. In the method for producing a semipolar self-supporting substrate according to 4,
In the determining step, if the surface of the semi-polar seed substrate is not damaged, it is determined that the substrate is reusable, and if the surface of the semi-polar seed substrate is damaged, it is determined that the substrate cannot be reused. A method for manufacturing a semi-polar free-standing substrate.
10. 10. In the method for manufacturing a semipolar self-supporting substrate according to any one of 1 to 9,
the main surface of the semipolar seed substrate is a surface having an off angle of 15° or less from the {hklm} plane;
In the cutting step, the semipolar self-supporting substrate manufacturing method includes cutting out the semipolar self-supporting substrate having the {hklm} plane as a main surface.
11. 11. In the method for producing a semipolar self-supporting substrate according to 10,
The semipolar self-supporting substrate manufacturing method, wherein the main surface of the semipolar seed substrate has an off angle of 15° or less from the {-1-12-3} plane.
12. 12. In the method for manufacturing a semipolar self-supporting substrate according to any one of 1 to 11,
The preparation step includes
a fixing step of fixing a base substrate including a group III nitride semiconductor layer having a semipolar plane as a main surface to a susceptor;
With the base substrate fixed to the susceptor, a group III nitride semiconductor is grown on the main surface of the group III nitride semiconductor layer by HVPE (Hydride Vapor Phase Epitaxy) to form a first growth layer. a first growth step of forming;
a cooling step of cooling a laminate including the susceptor, the underlying substrate, and the first growth layer;
After the cooling step, with the base substrate fixed to the susceptor, a group III nitride semiconductor is grown on the first growth layer by HVPE to form a second growth layer. 2 growth step;
a seed substrate cutting step of cutting out at least part of the second growth layer as the semipolar seed substrate;
A method for manufacturing a semi-polar free-standing substrate having

This application claims priority based on Japanese Patent Application No. 2018-158077 filed on August 27, 2018, and the entire disclosure thereof is incorporated herein.

Claims (11)

a preparation step of preparing a semipolar seed substrate having a semipolar plane as a main surface and made of a group III nitride semiconductor;
a group III nitride semiconductor layer forming step of epitaxially growing a group III nitride semiconductor on the semipolar seed substrate to form a group III nitride semiconductor layer;
a cutting step of cutting out a semipolar self-supporting substrate having a semipolar plane as a main surface from the III-nitride semiconductor layer;
After the cutting step, a processing step of removing all of the group III nitride semiconductor layer from the semipolar seed substrate in which a part of the group III nitride semiconductor layer remains;
after performing the group III nitride semiconductor layer forming step and the cutting step by reusing the semipolar seed substrate from which the group III nitride semiconductor layer has been removed ,
The preparation step includes
a fixing step of fixing a base substrate including a group III nitride semiconductor layer having a semipolar plane as a main surface to a susceptor;
With the base substrate fixed to the susceptor, a group III nitride semiconductor is grown on the main surface of the group III nitride semiconductor layer by HVPE (Hydride Vapor Phase Epitaxy) to form a first growth layer. a first growth step of forming;
a cooling step of cooling a laminate including the susceptor, the underlying substrate, and the first growth layer to generate cracks in the first growth layer;
After the cooling step, with the base substrate fixed to the susceptor, a group III nitride semiconductor is grown on the first growth layer by HVPE to form a second growth layer having a thickness of 300 μm or more. a second growth step of forming a growth layer;
a seed substrate cutting step of cutting out at least part of the second growth layer as the semipolar seed substrate;
A method for manufacturing a semi-polar free-standing substrate having In the method for manufacturing a semipolar self-supporting substrate according to claim 1,
The method for manufacturing a semipolar self-supporting substrate, wherein in the processing step, a part of a surface of the semipolar seed substrate that is in contact with the group III nitride semiconductor layer is removed. In the method for manufacturing a semipolar self-supporting substrate according to claim 1 or 2,
The method for manufacturing a semipolar self-supporting substrate, wherein, in the processing step, removal of all the group III nitride semiconductor layers is confirmed by surface observation. In the method for manufacturing a semipolar self-supporting substrate according to any one of claims 1 to 3,
further comprising a determining step of determining whether the semipolar seed substrate is reusable;
Reusing the semipolar seed substrate if it is determined to be reusable in the determination step,
A method for manufacturing a semipolar self-supporting substrate, wherein the reuse of the semipolar seed substrate is terminated when it is determined in the determining step that the semipolar seed substrate cannot be reused. In the method for manufacturing a semipolar self-supporting substrate according to claim 4,
In the determining step, when the radius of curvature of the semi-polar seed substrate is equal to or greater than a reference value, it is determined that the substrate is reusable, and when the radius of curvature of the semi-polar seed substrate is less than the reference value, it is determined that the substrate is not reusable. A method for manufacturing a semi-polar free-standing substrate. In the method for manufacturing a semipolar self-supporting substrate according to claim 4,
In the determining step, it is determined that the semi-polar seed substrate is reusable when the predetermined crack has not occurred in the semi-polar seed substrate, and it is determined that the semi-polar seed substrate is not reusable when the predetermined crack has occurred in the semi-polar seed substrate. A method for manufacturing a semi-polar free-standing substrate. In the method for manufacturing a semipolar self-supporting substrate according to claim 4,
In the determining step, when the thickness of the semi-polar seed substrate is equal to or greater than a reference value, it is determined that the substrate is reusable, and when the thickness of the semi-polar seed substrate is less than the reference value, it is determined that the substrate is not reusable. A method for manufacturing a semi-polar free-standing substrate. In the method for manufacturing a semipolar self-supporting substrate according to claim 4,
In the determining step, if the surface roughness of the semi-polar seed substrate is less than a reference value, it is determined that the substrate is reusable, and if the surface roughness of the semi-polar seed substrate is equal to or greater than the reference value, it is determined that reusability is not possible. A method for manufacturing a semi-polar free-standing substrate to determine. In the method for manufacturing a semipolar self-supporting substrate according to claim 4,
In the determining step, if the surface of the semi-polar seed substrate is not damaged, it is determined that the substrate is reusable, and if the surface of the semi-polar seed substrate is damaged, it is determined that the substrate cannot be reused. A method for manufacturing a semi-polar free-standing substrate. In the method for manufacturing a semipolar self-supporting substrate according to any one of claims 1 to 9,
The main surface of the semipolar seed substrate is a plane having an off angle of 15° or less from the {-1-12-3} plane,
In the cutting step, a semipolar self-supporting substrate manufacturing method for cutting out the semipolar self-supporting substrate having a {-1-12-3} plane as a main surface. In the method for manufacturing a semipolar self-supporting substrate according to any one of claims 1 to 10,
In the second growth step, the group III nitride semiconductor grown from each of the first surface region and the second surface region of the first growth layer, separated from each other by the crack, is bonded to each other and integrated. A method for producing a semi-polar free-standing substrate by growing a III-nitride semiconductor until a

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