JP5370613B2 - Nitride semiconductor crystal and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a large area nitride semiconductor crystal in which the variation of the off-angle on the surface is small. <P>SOLUTION: The method for producing a nitride semiconductor crystal comprises growing a semiconductor layer on a seed substrate to obtain the nitride semiconductor crystal. The seed substrate includes a plurality of seed substrates composed of the same material, and at least one of the seed substrates has an off-angle different from the off-angles of other seed substrates. The plurality of seed substrates are disposed in a semiconductor crystal production apparatus so as to have the off-angle distribution of a single semiconductor layer smaller than the off-angle distributions of the seed substrates when the single semiconductor layer is grown on the seed substrates, and then the single semiconductor layer is grown. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a nitride semiconductor crystal and a manufacturing method thereof, and more particularly to a nitride semiconductor crystal having a large area and a small variation in surface off angle and a manufacturing method thereof.

  Nitride semiconductors typified by gallium nitride (GaN) have a large band gap, and the transition between bands is a direct transition type. Therefore, relatively light emitting diodes such as ultraviolet, blue and green, semiconductor lasers, etc. It is a promising material as a substrate for semiconductor devices such as light emitting elements on the short wavelength side and electronic devices.

  Nitride semiconductors have a high melting point, and the dissociation pressure of nitrogen near the melting point is high, so that bulk growth from the melt is difficult. On the other hand, it is known that a nitride semiconductor crystal can be produced by using a vapor phase growth method such as a hydride vapor phase growth method (HVPE method) and a metal organic chemical vapor deposition method (MOCVD method).

  At this time, the nitride semiconductor crystal can be grown on the surface of the base substrate by supplying the source gas after the base substrate is placed on the support. The nitride semiconductor crystal grown on the base substrate is separated from the support together with the base substrate, and can be taken out by removing the base substrate by a method such as polishing as necessary (see, for example, Patent Document 1).

  As the base substrate, for example, different types of substrates such as sapphire and GaAs are often used. A nitride semiconductor crystal grown on a heterogeneous substrate is warped due to a difference in lattice constant or thermal expansion coefficient from the heterogeneous substrate serving as a base substrate. It is known that the warpage is observed even in a nitride semiconductor free-standing crystal from which the base substrate is removed.

  When the nitride semiconductor free-standing crystal is warped, the off-angle variation occurs on the surface of the nitride semiconductor substrate formed by processing the crystal. Here, the “off angle” is an inclination angle in the principal surface normal direction with respect to the low index surface.

  When there is a variation in off-angle on the surface of the nitride semiconductor substrate, when a semiconductor element is manufactured on the substrate, for example, in the case of a light-emitting device, the composition of the epitaxial layer varies, and as a result, the variation in emission wavelength within the substrate surface. May occur.

  As described above, the occurrence of variation in the off-angle on the surface of the nitride semiconductor substrate may affect the characteristics of the semiconductor element using the nitride semiconductor substrate. Therefore, various studies have been made to suppress the variation. .

  Patent Document 2 describes that the growth direction of a gallium nitride crystal is inclined as a cause of variation in the off-angle of the gallium nitride crystal on the surface of the gallium nitride substrate. The gallium nitride crystal grows while tilting toward the center of the base substrate.

  For this reason, even when the gallium nitride crystal is processed so that the crystal axis near the center of the gallium nitride substrate coincides with the normal of the gallium nitride substrate surface, the crystal axis and the normal of the gallium nitride substrate surface Are not matched, and it is described that variation in off-angle occurs when viewed over the entire gallium nitride substrate. And in order to avoid these, the manufacturing method processed into a concave spherical shape is disclosed.

  On the other hand, as one of the methods for producing a large-area nitride semiconductor substrate, there is a method of obtaining a large-area nitride semiconductor substrate by arranging at least two seed substrates and growing crystals on the substrates. Documents 3 and 4 describe.

  In Patent Document 3, a plurality of nitride semiconductor seed substrates are combined with (0001) planes, (000-1) planes, or (0001) planes and (000-1) planes of adjacent nitride semiconductor seed substrates. The nitride semiconductor seed substrates are arranged so that the {10-10} planes face each other, and the nitride semiconductor is regrown on the upper surfaces of the arranged nitride semiconductor seed substrates. It is described that a nitride semiconductor layer having a {10-10} plane as a main surface is formed to obtain a large-area {10-10} plane nitride semiconductor wafer.

  In Patent Document 4, a plurality of nitride semiconductor seed substrates are prepared, the main surfaces of the plurality of nitride semiconductor seed substrates are parallel to each other, and the [0001] directions of the bars are the same. Nitride semiconductor layers having a continuous {10-10} plane as a main surface by arranging the substrates next to each other in the direction and re-growing the nitride semiconductor on the top surface of the arranged nitride semiconductor seed substrate To obtain a nitride semiconductor substrate.

JP 2006-240988 A JP 2009-126727 A JP 2006-315947 A JP 2008-143772 A

  However, since the method described in Patent Document 2 is simply a technique for reducing the variation in the off angle by processing the surface along the variation in the crystal axis, the method can be used for photolithography using a substrate having a concave substrate surface. When performing an element manufacturing process such as lithography, a problem sometimes occurs.

  Further, Patent Documents 3 and 4 do not describe the variation in the off-angle of the surface of the manufactured nitride semiconductor, and it is unclear how much the variation in the crystal axis can be reduced.

  Therefore, the present invention relates to a method for manufacturing a nitride semiconductor crystal, and an object thereof is to manufacture a large-area nitride semiconductor crystal with less variation in surface off-angle than in the prior art. Another object of the present invention is to manufacture a nitride semiconductor substrate having a small variation in off-angle by reducing the variation in crystal axes as much as possible without using a special processing method.

  In order to achieve the above object, as a result of intensive studies by the present inventors, surprisingly, a plurality of seed substrates having different off angles are arranged, and a single nitride semiconductor layer is grown thereon. Thus, when the nitride semiconductor crystal was obtained, it was found that variation in the off-angle of the obtained nitride semiconductor crystal was reduced, and the present invention was completed.

That is, this invention consists of the following.
1. In a nitride semiconductor crystal manufacturing method for obtaining a nitride semiconductor crystal by growing a semiconductor layer on a seed substrate, the seed substrate includes a plurality of seed substrates of the same material, and at least one of the plurality of seed substrates is another When the single semiconductor layer is grown on the plurality of seed substrates, the off-angle distribution of the single semiconductor layer is larger than the off-angle distribution of the plurality of seed substrates. A method for producing a nitride semiconductor crystal, wherein the single semiconductor layer is grown by disposing the plurality of seed substrates so as to reduce the number of seed substrates.
2. The plurality of seed substrates are made of a hexagonal semiconductor, the growth surface is substantially a {10-10} plane, and at least one seed substrate of the plurality of seed substrates is [0001] with respect to the other seed substrate. 2. The method for producing a nitride semiconductor crystal as described in 1 above, wherein only the off angle in either the axial direction or the [11-20] axial direction is different.
3. The plurality of seed substrates are made of a hexagonal semiconductor, the growth surface is substantially a {11-20} plane, and at least one seed substrate of the plurality of seed substrates is [0001] relative to the other seed substrate. 2. The method for producing a nitride semiconductor crystal as described in 1 above, wherein only the off angle in either the axial direction or the [10-10] axial direction is different.
4). The plurality of seed substrates are made of a hexagonal semiconductor, the growth surface is a substantially (0001) surface or a substantially (000-1) surface, and at least one seed substrate of the plurality of seed substrates is the other seed substrate. On the other hand, the nitride semiconductor crystal manufacturing method according to item 1, wherein only the off angle in either the [10-10] axial direction or the [11-20] axial direction is different.
5. The plurality of seed substrates are made of a hexagonal semiconductor, the growth surface is a substantially (0001) surface or a substantially (000-1) surface, and at least one seed substrate of the plurality of seed substrates is the other seed substrate. On the other hand, the off-angle in both the [10-10] axial direction and the [11-20] axial direction are different from each other, wherein the nitride semiconductor crystal manufacturing method according to item 1 is characterized.
6). The plurality of seed substrates are made of a hexagonal semiconductor, the growth surface is substantially a {10-10} plane, and at least one seed substrate of the plurality of seed substrates is [11− [20] The method for producing a nitride semiconductor crystal as described in [1] above, wherein the off angles in both the axial direction and the [0001] axial direction are different.
7). The plurality of seed substrates are made of a hexagonal semiconductor, the growth surface is substantially a {11-20} plane, and at least one seed substrate of the plurality of seed substrates is [10− [10] The method for producing a nitride semiconductor crystal as described in [1] above, wherein the off angles in both the axial direction and the [0001] axial direction are different.
8). When a single semiconductor layer is grown on the plurality of seed substrates, the off-angles are gradually changed so that variations in off-angles of the single semiconductor layer are reduced, and the plurality of seed substrates are 8. The method for producing a nitride semiconductor crystal as described in any one of 1 to 7 above, wherein:
9. Any one of 1 to 8 above, wherein the plurality of seed substrates are arranged so that the off-angle gradually changes from the vicinity of the center of the plurality of seed substrates toward the periphery.
The method for producing a nitride semiconductor crystal according to Item.
10. 10. The nitride semiconductor as described in any one of 1 to 9 above, wherein the plurality of seed substrates are arranged so that a crystallographic surface shape of the plurality of continuous seed substrates is convex. Crystal manufacturing method.
11. The plurality of seed substrates are arranged such that an off angle of an intermediate portion of the seed is smaller than an off angle of both ends of the seed composed of the plurality of seed substrates. The method for producing a nitride semiconductor crystal according to any one of the above.
12 Any one of the preceding items 1 to 11, wherein the plurality of seed substrates are arranged so that off-angle directions of at least some of the plurality of seed substrates are substantially the same. 2. A method for producing a nitride semiconductor crystal according to 1.
13. 13. The method for manufacturing a nitride semiconductor crystal according to any one of items 1 to 12, wherein the plurality of seed substrates include at least one selected from sapphire, SiC, ZnO, and a group III nitride semiconductor.
14 14. The nitride semiconductor crystal manufacturing method according to any one of items 1 to 13, wherein the single semiconductor layer is at least one selected from gallium nitride, aluminum nitride, indium nitride, and mixed crystals thereof. .
15. Any one of the HVPE method, the MOCVD method, the MBE method, the sublimation method, and the PLD method, wherein a single semiconductor layer is grown on the plurality of seed substrates. The nitride semiconductor crystal manufacturing method as described.
16. The plurality of seed substrates are seed substrates manufactured by preparing a plurality of ingots of the same material and cutting out a portion having the smallest off angle in each ingot from each ingot. 16. The method for producing a nitride semiconductor crystal according to any one of 15 above.
17. The plurality of seed substrates are manufactured by cutting out an ingot in which the angle of inclination of the crystal axis changes from the vicinity of the center toward the periphery, and at least one of the plurality of seed substrates is different from other seed substrates. 17. The method for producing a nitride semiconductor crystal as described in any one of 1 to 16 above, wherein the seed substrates are a plurality of seed substrates having different off angles.
18. 18. The method for producing a nitride semiconductor crystal as described in 16 or 17 above, wherein the ingot is formed by a semiconductor crystal production method in which a semiconductor layer is grown on a seed.
19. A group III nitride semiconductor crystal produced by the production method according to any one of items 1 to 18.
20. A group III nitride semiconductor crystal having a principal plane other than the (0001) plane, wherein the off-angle distribution is 1 ° or less within a diameter of 2 inches.
21. Thickness of 100 μm to 8 cm having a main surface inclined at an off angle of 0 ° to 65 ° with respect to the {10-10} plane of the hexagonal crystal and having dislocations penetrating the surface of the main surface It is a group III nitride semiconductor crystal, and the off angle distribution of the [10-10] axis per 2 inches in the [0001] axis direction of the group III nitride semiconductor crystal is within ± 0.93 °. A group III nitride semiconductor crystal characterized.
22. 22. The group III nitride semiconductor crystal as described in 20 or 21 above, wherein there is a region where the off-angle variation per mm of crystal exceeds 0.015 °.
23. 23. The group III nitride semiconductor crystal as described in any one of 20 to 22 above, wherein there is a region where the off-angle variation per mm of crystal exceeds 0.056 °.
24. 24. The group III nitride semiconductor crystal as described in any one of 20 to 23 above, wherein there are a plurality of regions where the amount of change in off-angle per 1 mm of crystal exceeds 0.03 °.
25. 25. The group III nitride semiconductor crystal according to any one of items 20 to 24, wherein an area of the main surface is larger than 750 mm ² .
26. The group III nitride semiconductor crystal according to any one of items 20 to 25, wherein a dislocation density of dislocations penetrating the surface of the main surface is 5 × 10 ⁵ to 2 × 10 ⁸ cm ^−2. .

  According to the method for manufacturing a nitride semiconductor crystal of the present invention, the off-angle of each seed substrate included in the plurality of seed substrates is controlled, and the plurality of seed substrates are arranged on the plurality of seed substrates. It is possible to control the off-angle of a single semiconductor layer grown in a uniform manner, and the variation in off-angle in the manufactured nitride semiconductor crystal can be significantly reduced as compared with the conventional case.

It is a schematic diagram for explaining the inclination of the crystal axis of a nitride semiconductor crystal obtained when a semiconductor layer is grown on a seed substrate having a uniform off angle. It is a schematic diagram for demonstrating the inclination of the crystal axis of the nitride semiconductor crystal obtained when a semiconductor layer is crystal-grown on the seed substrate which applied the method of this invention. It is a schematic diagram for demonstrating an off angle. It is the schematic of an HVPE apparatus. (A) (10-10) plane gallium nitride seed substrate arrangement method in Example 1, (b) is a schematic diagram for explaining the inclination of the crystal axis of the nitride semiconductor crystal according to the present invention in Example 1. It is. It is a schematic diagram for demonstrating the off-angle measurement location in Examples 1-3 and Comparative Examples 1-4. (A) (10-10) plane gallium nitride seed substrate arrangement method in Example 2, (b) is a schematic diagram for explaining the inclination of the crystal axis of the nitride semiconductor crystal according to the present invention in Example 2. It is. (A) is a method for arranging a (10-10) plane gallium nitride seed substrate in Example 3, and (b) is a schematic diagram for explaining the inclination of the crystal axis of the nitride semiconductor crystal according to the present invention in Example 3. It is. (A) is a method for arranging a (10-10) plane gallium nitride seed substrate in Example 4, and (b) is a schematic diagram for explaining the inclination of the crystal axis of the nitride semiconductor crystal according to the present invention in Example 4. It is. (A) is a method for arranging a (10-10) plane gallium nitride seed substrate in Comparative Example 1, and (b) is a schematic diagram for explaining the inclination of the crystal axis of the nitride semiconductor crystal according to the present invention in Comparative Example 1. It is. (A) is a method for arranging a (10-10) plane gallium nitride seed substrate in Comparative Example 2, and (b) is a schematic diagram for explaining the inclination of the crystal axis of the nitride semiconductor crystal according to the present invention in Comparative Example 2. It is. (A) is a method for arranging a (10-10) plane gallium nitride seed substrate in Comparative Example 3, and (b) is a schematic diagram for explaining the inclination of the crystal axis of the nitride semiconductor crystal according to the present invention in Comparative Example 3. It is. (A) is a method for arranging a (10-10) plane gallium nitride seed substrate in Comparative Example 4, and (b) is a schematic diagram for explaining the inclination of the crystal axis of the nitride semiconductor crystal according to the present invention in Comparative Example 4. It is.

  Below, the manufacturing method of the nitride semiconductor crystal of this invention is demonstrated in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.

  In the following description, a gallium nitride crystal may be described as an example of the nitride semiconductor crystal, but the nitride semiconductor crystal that can be employed in the present invention is not limited to this.

  In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

(Seed substrate material, lattice constant, thermal expansion coefficient)
The seed substrate may be of any type as long as a desired nitride semiconductor crystal can be grown on the crystal growth surface. Further, a seed substrate may be used as a base substrate for crystal growth. Since the nitride semiconductor crystal is a hexagonal semiconductor, the seed substrate is preferably made of a hexagonal semiconductor.

  Examples of the material of the seed substrate include sapphire, SiC, ZnO, and a group III nitride semiconductor. Among them, a group III nitride semiconductor is preferable, a nitride semiconductor containing the same group III element as the nitride semiconductor to be manufactured is more preferable, and a nitride semiconductor of the same type as the nitride semiconductor to be manufactured is more preferable. .

  Each seed substrate included in the plurality of seed substrates is made of the same material. Here, the “same material” means that the chemical properties are the same material and the same material. By using the same material for each seed substrate included in the plurality of seed substrates, the characteristic distribution of the nitride semiconductor crystal to be manufactured can be made uniform.

  The lattice constant of the seed substrate is preferably close to the lattice constant of the nitride semiconductor crystal to be manufactured. This is because the occurrence of defects due to lattice mismatch can be suppressed. The difference in lattice constant between the nitride semiconductor crystal to be manufactured and the seed substrate is preferably within 17%, more preferably within 5%, based on the lattice constant of the nitride semiconductor crystal.

Further, the thermal expansion coefficient of the seed substrate is preferably close to the thermal expansion coefficient of the nitride semiconductor crystal to be manufactured. This is because the occurrence of warpage due to the difference in thermal expansion coefficient can be suppressed. The absolute value of the difference in thermal expansion coefficient between the nitride semiconductor crystal to be manufactured and the seed substrate is preferably 2 × 10 ⁻⁶ / ° C. or less, and more preferably 1 × 10 ⁻⁶ / ° C. or less. .

(Shape of seed substrate)
The shape of the seed substrate is not particularly limited as long as it does not depart from the essence of the present invention, but a so-called bar shape may be used. In addition, it is preferable that a plurality of seed substrates have the same shape because a large number of seed substrates can be easily arranged. The shape of the main surface of the seed substrate may be a polygon, and a rectangle or a square can also be preferably used.

  The length of one side of the main surface of the seed substrate is preferably 5 mm or more, more preferably 15 mm or more, and further preferably 20 mm or more. By setting the length of one side of the main surface of the seed substrate to 5 mm or more, the number of seed substrates to be prepared can be reduced when a large-area nitride semiconductor crystal is manufactured.

  In addition, by using a seed substrate having a side length of 5 mm or more on one side of the main surface, it is possible to improve the alignment accuracy of the arranged seed substrate, and to form a bonding surface of the seed substrate that easily causes a decrease in crystallinity. It is also preferable because it can be reduced.

  Here, the main surface of the seed substrate in the present invention refers to the widest surface of the seed substrate.

(Surface orientation of seed substrate)
In crystal geometry, a display such as (hkl) or (hkil) is used to indicate the plane orientation of a crystal plane. The plane orientation of the crystal plane in a hexagonal crystal such as a group III nitride crystal is represented by (hkil).

  Here, h, k, i and l are integers called Miller indices and have a relationship of i = − (h + k). The plane having the plane orientation (hkil) is referred to as the (hkil) plane. The {hkil} plane means a generic plane orientation including the (hkil) plane and individual plane orientations equivalent to the crystal geometry.

  The plane orientation of the main surface of the seed substrate includes polar planes such as (0001) plane and (000-1) plane, nonpolar planes such as {1-100} plane and {11-20} plane, {1-102} plane and A semipolar plane such as {11-22} plane can be mentioned.

  When the shape of the seed substrate is rectangular, the main surface of the seed substrate is {10-10} plane, {11-20} plane, {10-1-1} plane, {20- The 2-1} plane is preferable, and the {10-10} plane is more preferable. The plane orientations of the four side surfaces are (0001) plane, (000-1) plane, {11-20} plane and {11-20} plane, (0001) plane, (000-1) plane, {10 The −10} plane and the {10-10} plane are preferable, and the (0001) plane, the (000-1) plane, the {11-20} plane, and the {11-20} plane are more preferable.

(Seed substrate main surface area)
As a large area of the main surface of the seed substrate including a plurality of seed substrates well, preferably at 50 mm ² or more, more preferably 75 mm ² or more, more preferably 100 mm ² or more.

By setting the area of the main surface of the seed substrate to 50 mm ² or more, the number of seed substrates to be prepared can be reduced. In addition, since the number of bonding surfaces can be reduced, an increase in the twist angle distribution in the nitride semiconductor crystal grown on the seed substrate can be suppressed. The “twist angle” indicates an orientation distribution (in-plane orientation distribution) of crystal axes in a direction parallel to the main surface.

(An angle between the joint surface and the main surface)
The “bonding surface” refers to a surface adjacent to each other when seed substrates are arranged. The angle formed by the joint surface and the main surface is not particularly limited, but it is desirable that the angle is substantially a right angle in consideration of the ease of seed substrate preparation. The angle formed by the joint surface and the main surface is preferably 88 ° to 92 °, more preferably 89 ° to 91 °, and even more preferably 89.5 ° to 90.5 °.

(Off angle expression method)
FIG. 3 is a schematic diagram showing the relationship between the main surface normal direction of the seed substrate and the seed substrate crystal axis direction in order to explain the inclination (off angle) of the main surface normal direction with respect to the low index surface. . In FIG. 3, it is assumed that the low index surface of the main surface is the (10-10) plane and the bonding surfaces are the (0001) plane and the (11-20) plane. Note that the off-angle of the seed substrate can be measured by an X-ray analysis method.

  The angle formed between the seed substrate principal surface normal direction and the [10-10] axis is φ, and the seed substrate principal surface normal is projected onto a plane defined by the [10-10] axis and the [0001] axis. The angle formed between the axis and the [10-10] axis is φc, and the seed substrate main surface normal is projected onto a plane defined by the [10-10] axis and the [11-20] axis of the seed substrate crystal axis The angle between the axis and the [10-10] axis is φa.

  In the case shown in FIG. 3, the principal surface normal direction of the seed substrate is inclined by [phi] c in the [0001] direction and [phi] a in the [11-20] direction with respect to the low index surface of the main surface, that is, the (10-10) plane. It can be expressed as tilted.

  Here, the [hkil] direction refers to a direction perpendicular to the (hkil) plane (the normal direction of the (hkil) plane), and the <hkil> direction refers to the [hkik] direction and its crystal geometry. A generic direction including individual directions equivalent to.

(Inclination with respect to the low index surface in the normal direction of the joint surface)
The normal direction of the joint surface may be inclined from the low index surface or may not be inclined. However, considering the ease of arrangement and the twist angle distribution of the crystal after bonding, it is preferable that the difference in inclination from the low index surface in each axial direction between the two bonding surfaces facing each other is small. Therefore, the difference in inclination from the low index surface in the axial direction between the two facing joint surfaces is preferably within 1 °, more preferably within 0.7 °, and even more preferably 0.5 ° or less.

  For example, the bonding surface opposite to the bonding surface whose normal direction is + 5 ° in the [11-20] direction and + 5 ° in the [10-10] direction is inclined from the (0001) plane is the [11-20] direction. + 5 ° in the [10-10] direction, and a bonding surface in which the normal direction of the bonding surface is inclined from the (000-1) plane is preferable.

  Further, the absolute value distribution of the inclination from the low index surface in the direction of each axis between the seed substrates is preferably within 1 °, more preferably within 0.7 °, and more preferably within 0.5 °. By making the absolute value distribution of the inclination from the low index plane in each axial direction between the seed substrates within 1 °, the bonded surfaces can be faced substantially in parallel, and the twist angle distribution of the crystals after bonding can be reduced. Because.

(Cut out main surface, cut out method)
A seed substrate having a desired surface can be obtained by cutting out an ingot as necessary. For example, a group III nitride semiconductor ingot having a (0001) plane is formed, and then the {10-10} plane or the {11-20} plane is cut out so that the {10-10} plane or {11- A seed substrate having a 20} plane as a main surface can be obtained.

  The plurality of seed substrates are preferably obtained by preparing a plurality of ingots of the same material and cutting out the portion having the smallest off-angle distribution in each ingot. This can reduce the off-angle distribution in the seed substrate.

  As a method of preparing a plurality of seed substrates having at least one of the plurality of seed substrates having different off angles from other seed substrates, the off angle gradually changed from the vicinity of the center to the peripheral portion, that is, from the inside to the outside. A method of cutting from an ingot is preferred. However, in order to reduce the variation in the off angle within each seed substrate, it is preferable to cut out only the portion of the ingot having the smallest variation in the off angle.

  As the cutting method, there are a method of processing (grinding and slicing) with a scissors, a grinding machine, an inner peripheral slicer, a wire saw, etc., a method of polishing by polishing, and a method of dividing by cleavage. Among them, it is preferable to form a {10-10} plane or a {11-20} plane by cleavage.

  As for the cleavage method, a diamond scriber may be used for cutting and a laser scriber device may be used. You may divide by hand as it is, and you may carry out with the braking device on other foundations.

  The parallelism of the front and back surfaces of the seed substrate is preferably within 1 °, more preferably within 0.7 °, and even more preferably within 0.5 °. By setting the parallelism of the seed substrate within 1 °, it is possible to prevent the problem that it is difficult to perform processing such as polishing.

  The ingot is preferably an ingot made by a semiconductor crystal manufacturing method in which a semiconductor layer is grown on a seed. Examples of the semiconductor crystal manufacturing method include an HVPE method.

(Seed board placement method)
In the manufacturing method of the present invention, a plurality of seed substrates are arranged, and a single semiconductor layer is grown on the plurality of seed substrates. Here, the “single semiconductor layer” refers to a single semiconductor layer.

  The plurality of seed substrates is configured such that when a single semiconductor layer is grown on the plurality of seed substrates, the off-angle distribution of the single semiconductor layer is smaller than the off-angle distribution of the plurality of seed substrates. To place. By disposing the seed substrate in this way, a nitride semiconductor crystal having a small off-angle distribution can be manufactured.

  Here, “off-angle distribution” refers to variation in off-angle within the main surface, and can be obtained by performing X-ray diffraction measurement at a plurality of points within the main surface. The difference between the off-angle distribution of the single semiconductor layer and the off-angle distribution of the plurality of seed substrates is preferably a difference of 10% or more based on the off-angle distribution of the single semiconductor layer. A difference of 20% to 2000% is more preferable.

  The plurality of seed substrates may be arranged so as to be adjacent to each other in the same plane, or may be arranged so as to be adjacent to each other in a planar shape.

  In the manufacturing method of the present invention, a plurality of seed substrates having different off angles from other seed substrates are used as at least one of the plurality of seed substrates. This makes it possible to control the crystallographic plane shape of a plurality of continuous seed substrates.

  For example, when the plurality of seed substrates are made of a hexagonal semiconductor and the growth surface is a substantially {10-10} plane, at least one seed substrate among the plurality of seed substrates is [ Preferably, at least one off angle in the [0001] axial direction and the [11-20] axial direction are different.

  When the plurality of seed substrates are made of a hexagonal semiconductor and the growth surface is a substantially {11-20} plane, at least one seed substrate of the plurality of seed substrates is [0001] with respect to the other seed substrate. It is preferable that at least one off angle in the axial direction and the [10-10] axial direction are different.

  When the plurality of seed substrates are made of a hexagonal semiconductor and the growth surface is a substantially (0001) surface or a substantially (000-1) surface, at least one seed substrate of the plurality of seed substrates is the other seed substrate. On the other hand, it is preferable that at least one off angle in the [10-10] axial direction and the [11-20] axial direction are different.

  In addition, a substantially {10-10} plane, a substantially {11-20} plane, a substantially (0001) plane, and a substantially (000-1} plane are an off angle where each growth plane is about ± 10 ° in a plurality of substrates. Within the range of the deviation, it means that they are aligned in the {10-10} plane, the {11-20} plane, the (0001) plane, and the (000-1) plane direction.

  The plurality of seed substrates are preferably arranged so that the off angle gradually changes from the vicinity of the center toward the periphery. By arranging a plurality of seed substrates in this way, the crystallographic plane shape of a plurality of continuous seed substrates can be controlled.

  Here, the “off-angle of the seed substrate gradually changes” from the vicinity of the center toward the peripheral portion means that the off-angle of the seed substrate gradually changes from the inside to the outside of the seed substrate including a plurality of seed substrates. It shows that.

  Depending on the crystal structure of the semiconductor, it does not warp uniformly in any direction from the vicinity of the center. Therefore, it is necessary to determine the amount of change in the off angle in consideration of the crystal structure of the semiconductor. Specifically, for example, when a gallium nitride layer having a {10-10} plane is grown on a gallium nitride seed substrate having a {10-10} plane, the [0001] axial direction is the other direction. Therefore, it is preferable to gradually change the off-angle of the seed substrate from the inside toward the outside only in the [0001] axis direction.

Further, depending on the structure of the semiconductor crystal manufacturing apparatus, there is a case where the temperature distribution inside the semiconductor crystal manufacturing apparatus is largely biased, and the center of the warp of the grown semiconductor layer is largely deviated from the vicinity of the center of the seed substrate.

  In the above case, the variation in the off angle of a single semiconductor layer is caused by the variation in the off angle of a plurality of seed substrates in consideration of the warpage center and the amount of warpage in each portion of the grown single semiconductor layer. The seed substrate may be arranged so that the off angle gradually changes from the inner side toward the outer side with respect to any one seed substrate included in the plurality of seed substrates, so that the number of seed substrates is smaller.

  In the above case, the difference between the off-angle variation of the single semiconductor layer and the off-angle variation of the plurality of seed substrates is preferably 10% or more, and preferably 20% to 2000%. More preferred. By setting it in this range, the crystal plane curvature of the seed substrate group composed of a plurality of seed substrates and the crystal plane curvature change amount of the single semiconductor layer being grown can be made substantially equal. Note that the variation in off-angle can be determined by X-ray diffraction measurement.

  Specifically, for example, it is preferable to arrange a plurality of seed substrates so that the crystallographic surface shape of the plurality of continuous seed substrates is convex. This makes it possible to reduce the off-angle distribution of the nitride semiconductor crystal to be produced by utilizing the change in the crystal plane curvature of the growing gallium nitride single crystal film.

  As another specific example, for example, in the case of producing a nitride semiconductor crystal having a main surface close to a low index plane, the intermediate portion of the seed is more than the off-angle of both ends of the seed composed of the plurality of seed substrates. It is preferable to arrange so that the off angle is smaller, and it is more preferable to arrange the off angle so that the off angle is continuously increased from the portion having the smallest off angle in the intermediate portion toward both ends. This makes it possible to reduce the off-angle distribution of a nitride semiconductor crystal having a main surface close to a low index surface to be manufactured by utilizing the change in crystal plane curvature of the single semiconductor layer being grown.

  Here, the “seed” refers to the entire structure in which a plurality of seed substrates are arranged to form a single structure. The portion sandwiched between the opposite ends of the seed is called an intermediate portion of the seed. Therefore, the intermediate portion does not indicate only the central portion connecting both ends of the seed, but the entire portion sandwiched between both ends of the seed.

  As another preferred specific example, it is preferable that at least some of the plurality of seed substrates are arranged so that the off-angle directions of adjacent seed substrates are substantially the same, and the absolute difference between the off-angle directions is absolute. The value is more preferably 0.3 to 2.0 °, and particularly preferably 0.5 to 1.5 °. It is preferable that the off-angle directions of adjacent seed substrates are substantially the same because dislocations that are likely to occur in crystals grown above the junction of the seed substrate can be reduced.

  That is, if the main surface normal direction of the seed substrate matches the orientation of the low index surface, the growth in the normal direction of each surface of the seed substrate becomes dominant. In this case, the laterally grown portions from the adjacent seed substrates meet in the gap at the junction. As in the ELO meeting part, a large amount of dislocations occur in the meeting part on the gap.

  A low index surface tilted from the main surface is generated by properly growing the main surface normal direction with respect to the low index surface (off angle). The surface grows obliquely with respect to the main surface while maintaining a low index surface. When an off-angle is added in the normal direction of the bonding surface, the bonding portion grows obliquely from one seed substrate and reaches the next seed substrate. By causing association on the adjacent seed substrate, a large amount of dislocations can be suppressed.

  The absolute value of the off angle of the seed substrate is preferably 0.1 ° or more, more preferably 1 ° or more, and further preferably 3 ° or more. By setting the absolute value of the off-angle of the seed substrate to 0.1 ° or more, before the growth part of the low index surface of one seed substrate straddles the gap, the lateral growth part from both of the adjacent seed substrates is , It is possible to suppress meeting in the gap.

  On the other hand, the absolute value of the off angle of the seed substrate is preferably 15 ° or less, more preferably 10 ° or less, and further preferably 7 ° or less. By setting the absolute value of the off angle of the seed substrate to 15 ° or less, an increase in surface step density can be suppressed, and problems such as step bunching (step densification) easily occurring during growth can be prevented.

  FIG. 1 is a schematic diagram illustrating a state in which a crystal is warped in a concave shape and a crystal surface is also curved in a concave shape using a cross-sectional view of a nitride semiconductor crystal. It is shown.

  In FIG. 1, reference numeral 101 denotes a seed substrate having aligned crystal axes, reference numeral 102 denotes a nitride semiconductor crystal manufactured by growing on the seed substrate 101, and reference numeral 103 denotes a slice of the nitride semiconductor crystal 102 at a broken line. Thus, the substrate is shown.

  When the crystal is grown on the seed substrate 101 with the aligned crystal axes, the manufactured nitride semiconductor crystal 102 is warped, and accordingly, the crystal axis inside the nitride semiconductor crystal 102 is also shifted from near the center toward the periphery. As the tilt increases, the tilt angle of the crystal axis varies.

  Conventionally, such a nitride semiconductor crystal 102 is sliced at a broken line portion and used as the nitride semiconductor substrate 103. However, since the inclination of the crystal axis inside the nitride semiconductor substrate 103 is not uniform, For example, when a light-emitting device is manufactured using the nitride semiconductor substrate 103, there has been a problem that the emission wavelength varies as described above.

  FIG. 2 shows a case where a single nitride semiconductor crystal is grown on a plurality of seed substrates by the manufacturing method of the present invention.

  In FIG. 2, reference numeral 201 denotes a configuration in which a plurality of seed substrates having different crystal axis inclinations are arranged so that the crystal axes of each seed substrate expand radially from the back surface side to the front surface side from the vicinity of the center toward the periphery. The seed substrate is shown. Reference numeral 202 denotes a nitride semiconductor crystal manufactured by growing on the seed substrate 201, and 203 denotes a state in which the nitride semiconductor crystal 202 is sliced at a broken line to form a substrate.

  2, the manufactured nitride semiconductor crystal 202 is warped as in the case shown in FIG. 1, but the crystal axis inside the nitride semiconductor crystal 202 is tilted by the action of the crystal axis of the seed substrate 201. However, for this reason, when the nitride semiconductor crystal 202 is sliced along the broken line, the nitride semiconductor substrate 203 with no variation in the tilt of the crystal axis can be manufactured.

  In addition, in the case shown in FIG. 2, depending on the crystal grown on the seed substrate, there is a crystal that warps in a convex shape, contrary to the case shown in FIG. 1, but in this case, the seed substrate 201 shown in FIG. By arranging a plurality of substrates having different crystal axis inclinations so that the crystal axes of each seed substrate radially extend from the surface side of the seed substrate toward the periphery from the vicinity of the center, the crystal axes are aligned. A semiconductor substrate can be manufactured.

(Off-angle change between seed substrates)
“Off-angle change amount between seed substrates” means that each seed substrate prepared by arranging a plurality of seed substrates so that the off-angle of each seed substrate gradually changes from near the center toward the periphery. The amount of change in the off-angle between the seed substrates.

  The preferred range of the off-angle variation between the seed substrates varies depending on the length of the single semiconductor layer and semiconductor crystal film grown on the plurality of seed substrates, but between the seed substrates prepared by arranging the plurality of seed substrates. The amount of change in the off-angle per unit length is usually preferably 0.02 ° / mm or more, more preferably 0.03 ° / mm or more, and 0.05 ° / mm or more. Is more preferable.

  By setting the amount of change in the off angle per unit length between the seed substrates including the plurality of seed substrates to 0.02 ° / mm or more, a plurality of seeds can be obtained from the crystal plane curvature of the seed substrate group including the plurality of seed substrates. It is possible to prevent the crystal plane curvature change amount of the semiconductor crystal film being grown on the substrate from becoming larger, and to reduce the off-angle change amount in the manufactured nitride semiconductor crystal.

  The amount of change in the off-angle per unit length between the seed substrates including a plurality of seed substrates is usually preferably 0.5 ° / mm or less, more preferably 0.3 ° / mm or less, More preferably, it is 0.2 ° / mm or less.

  By changing the off-angle change amount per unit length between seed substrates including a plurality of seed substrates to 0.5 ° / mm or less, the amount of change in crystal plane curvature of a semiconductor crystal film grown on the plurality of seed substrates As a result, it is possible to prevent the crystal plane curvature of the seed substrate group composed of a plurality of seed substrates from becoming larger, and to reduce the off-angle change amount in the manufactured nitride semiconductor crystal.

  The amount of change in the off-angle between the seed substrates is preferably adjusted so that the amount of crystal plane curvature of the seed substrate group composed of a plurality of seed substrates is the same as the amount of crystal plane curvature change of the growing semiconductor crystal film. This is because the off-angle distribution of the produced nitride semiconductor crystal can be reduced.

  Here, the “crystal plane curvature change amount” refers to the degree of change in the crystallographic plane shape curvature of a plurality of continuous seed substrates during the growth of the nitride semiconductor, and the shape of the fabricated nitride semiconductor It can be calculated by measuring the warpage. For example, the crystallographic surface shape of the seed substrate group is convex and the off-angle distribution is 1.0 °, and the crystallographic surface shape of the fabricated nitride semiconductor crystal is concave and the off-angle distribution is 0.5. In the case of °, the crystal plane curvature change amount is 1.5 °. The crystal plane curvature of the seed substrate group composed of a plurality of seed substrates and the crystal plane curvature change amount of the growing semiconductor crystal film are preferably 0.1 ° to 5.0 °, preferably 0.5 ° to 5.0 °. More preferably.

  If the amount of change in the off-angle between the seed substrates is too small, the amount of change in the crystal plane curvature of the growing gallium nitride single crystal film becomes larger than the crystal plane curvature of the seed substrate group consisting of a plurality of seed substrates. The amount of change in the off-angle in the nitride semiconductor crystal to be manufactured cannot be reduced.

  Specifically, for example, when the gallium nitride single crystal film is grown at least 0.3 mm or more, the off-angle variation per unit length of the seed substrate including a plurality of seed substrates is ± 0.005 ° / mm or more. Preferably, it is ± 0.007 ° / mm or more, more preferably ± 0.01 ° / mm or more.

Specifically, for example, a gallium nitride single crystal film is grown at least 0.3 mm or more on a (10-10) plane gallium nitride seed substrate prepared by arranging seed substrates with different off angles in an area corresponding to a diameter of at least 2 inches. In this case, the off-angle change amount between the seed substrates in the C-axis ([0001] axis) direction with a width of 2 inches is preferably ± 0.25 ° or more, and more preferably ± 0.35 ° or more. More preferably, it is more preferably ± 0.5 ° or more.

  Conversely, if the amount of change in the off-angle between the seed substrates is too large, the crystal plane curvature of the seed substrate group becomes larger than the amount of crystal plane curvature change of the gallium nitride single crystal film during the growth of the gallium nitride single crystal film. As a result, the off-angle change amount cannot be reduced.

  When the gallium nitride single crystal film is grown at least 0.3 mm or more, the off-angle change amount per unit length is preferably ± 0.04 ° / mm or less, and ± 0.03 ° / mm or less. More preferably, it is more preferably ± 0.02 ° / mm or less.

  Specifically, when a gallium nitride single crystal film is grown at least 0.3 mm or more on a (10-10) plane gallium nitride seed substrate prepared by arranging seed substrates having different off angles in an area corresponding to a diameter of at least 2 inches. The off-angle variation between the seed substrates in the C-axis ([0001] axis) direction is preferably ± 2 ° or less, more preferably ± 1.5 ° or less, and ± 1.0 ° or less. More preferably.

  An advantage of using a plurality of seed substrates in the manufacturing method of the present invention is that an arbitrary off-angle distribution can be given to a seed substrate including a plurality of seed substrates. When the in-plane off-angle change amount of the semiconductor crystal grown on the seed substrate is different, for example, when the warp on the inner peripheral side of the semiconductor crystal is small but the warp on the outer peripheral side is large, a seed including a plurality of seed substrates It is effective to use a substrate.

(manufacturing device)
In the present invention, a plate-like crystal is grown in a direction perpendicular to the crystal growth surface of the seed substrate by supplying a source gas to the seed substrate. Examples of growth methods include metal organic chemical vapor deposition (MOCVD), hydride vapor deposition (HVPE), molecular beam epitaxy (MBE), sublimation and pulsed laser deposition (PLD). The HVPE method having a high growth rate is preferable.

  FIG. 4 is a diagram for explaining a configuration example of a nitride semiconductor crystal manufacturing apparatus used in the present invention, but there is no particular limitation on the details of the configuration. The HVPE apparatus shown in FIG. 4 includes a susceptor 407 for placing a seed substrate and a reservoir 405 for containing a nitride semiconductor material to be grown in a reactor 400.

  In addition, introduction pipes 401 to 404 for introducing gas into the reactor 400 and an exhaust pipe 408 for exhausting are installed. Further, a heater 406 for heating the reactor 400 from the side surface is installed.

(Reactor material)
Examples of the material of the reactor 400 include quartz, sintered boron nitride, and stainless steel. A preferred material is quartz.

(Gas type of atmospheric gas)
The reactor 400 is filled with atmospheric gas in advance before starting the reaction. Examples of the atmospheric gas (carrier gas) include hydrogen, nitrogen, He, Ne, and an inert gas such as Ar. These gases may be mixed and used.

(Susceptor material, shape, distance from growth surface to susceptor)
As a material of the susceptor 407, carbon is preferable, and a material whose surface is coated with SiC is more preferable.

  The shape of the susceptor 407 is not particularly limited as long as the seed substrate used in the present invention can be installed. However, it is preferable that no structure exists near the crystal growth surface during crystal growth. If there is a structure that is likely to grow near the crystal growth surface, polycrystals adhere to the structure, and HCl gas is generated as the product, which adversely affects the crystal that is about to grow. It is.

  The contact surface between the seed substrate and the susceptor 407 is preferably separated from the crystal growth surface of the seed substrate by 1 mm or more, more preferably 3 mm or more, and further preferably 5 mm or more. This is to prevent the polycrystal generated from the susceptor surface from eroding the growth surface of the nitride semiconductor crystal.

(Reservoir)
The reservoir 405 contains a nitride semiconductor material to be grown. For example, when a group III-V nitride semiconductor is grown, a raw material to be a group III source is added. Examples of the raw material to be the group III source include Ga, Al, and In.

  A gas that reacts with the raw material put in the reservoir 405 is supplied from an introduction pipe 403 for introducing the gas into the reservoir 405. For example, when a raw material to be a group III source is put in the reservoir 405, HCl gas can be supplied from the introduction pipe 403.

  At this time, the carrier gas may be supplied from the introduction pipe 403 together with the HCl gas. Examples of the carrier gas include hydrogen, nitrogen, He, Ne, and an inert gas such as Ar. These gases may be mixed and used.

(Nitrogen source (ammonia), carrier gas, dopant gas) From the introduction pipe 404, a raw material gas serving as a nitrogen source is supplied. Usually, NH ₃ is supplied. A carrier gas is supplied from the introduction pipe 401. As the carrier gas, the same carrier gas supplied from the introduction pipe 404 can be exemplified. This carrier gas also has an effect of separating the source gas nozzle and preventing the polycrystal from adhering to the nozzle tip.

A dopant gas can also be supplied from the introduction pipe 402. For example, an n-type dopant gas such as SiH ₄ , SiH ₂ Cl ₂ and H ₂ S can be supplied.

(Gas introduction method)
The gases supplied from the introduction pipes 401 to 404 may be exchanged with each other and supplied from another introduction pipe. In addition, the source gas and the carrier gas serving as a nitrogen source may be mixed and supplied from the same introduction pipe. Further, a carrier gas may be mixed from another introduction pipe. These supply modes can be appropriately determined according to the size and shape of the reactor 400, the reactivity of the raw materials, the target crystal growth rate, and the like.

(Exhaust pipe location)
The gas exhaust pipe 408 can be installed on the top, bottom and side surfaces of the reactor inner wall. From the viewpoint of dust removal, it is preferably located below the crystal growth end, and more preferably a gas exhaust pipe 408 is installed on the bottom of the reactor as shown in FIG.

(Crystal growth conditions)
The crystal growth in the present invention is usually performed at 950 ° C. to 1120 ° C., preferably 970 ° C. to 1100 ° C., more preferably 980 ° C. to 1090 ° C., and 990 ° C. to
More preferably, it is carried out at 1080 ° C. This is because a nitride semiconductor crystal having a mirror surface can be easily obtained by setting this range.

  The pressure in the reactor is preferably 10 kPa to 200 kPa, more preferably 30 kPa to 150 kPa, and even more preferably 50 kPa to 120 kPa. This is because a nitride semiconductor crystal having a mirror surface can be easily obtained by setting this range.

(Crystal growth rate)
The growth rate of crystal growth in the present invention varies depending on the growth method, growth temperature, raw material gas supply amount, crystal growth surface orientation, etc., but is generally in the range of 5 μm / h to 500 μm / h, and is 10 μm / h or more. Is preferably 50 μm / h or more, and more preferably 70 μm or more. It is because productivity can be raised by setting it as this range.

  In addition to the above, the growth rate can be controlled by appropriately setting the type of carrier gas, the flow rate, the supply port-crystal growth edge distance, and the like.

(Nitride semiconductor crystal area)
According to the manufacturing method of the present invention, a nitride semiconductor crystal having a large main surface area can be easily obtained. The area of the main surface of the nitride semiconductor crystal can be appropriately adjusted according to the size of the crystal growth surface of the seed substrate and the crystal growth time.

According to the manufacturing method of the present invention, for example, the area of the main surface of the nitride semiconductor crystal can be 500 mm ² or more, can be larger than 750 mm ² , and can be 1500 mm ² or more. Yes, it can be 2500 mm ² or more, and further can be 10000 mm ² or more.

(Nitride semiconductor crystal)
The type of nitride semiconductor crystal provided by the present invention is not particularly limited. Specific examples include group III nitride semiconductor crystals, and more specific examples include gallium nitride, aluminum nitride, indium nitride, and mixed crystals thereof.

  The group III nitride semiconductor crystal of the present invention is a crystal having a main surface other than the (0001) plane and having an off-angle distribution of 1 ° or less within a diameter of 2 inches. Examples of principal surfaces other than the (0001) plane include {10-10} plane, {11-20} plane, (10-11) plane, and (20-21) plane.

  Further, the group III nitride semiconductor crystal of the present invention has a main surface inclined at an off angle of 0 ° to 65 ° with respect to the {10-10} plane of the hexagonal crystal, and the surface of the main surface is A Group III nitride semiconductor crystal having a threading dislocation and a thickness of 100 μm to 5 cm, and the [10-10] axis per 2 inches of the Group III nitride semiconductor crystal is turned off in the [0001] axis direction The angular distribution is within ± 0.93 °.

  The main surface of the group III nitride semiconductor crystal of the present invention refers to the widest surface of the group III nitride semiconductor crystal, and is 0 ° to 65 ° with respect to the {10-10} plane of the hexagonal crystal. The surface is not particularly limited as long as the surface is inclined at an off angle.

For example, (10-11) plane and (10-1-1) plane having an off angle of 28 ° with respect to the {10-10} plane; 47 ° off angle with respect to the {10-10} plane (10-12) plane and (10-1-2) plane; (10-13) plane and (10-1-3) plane having an off angle of 58 ° with respect to the {10-10} plane; {10 (10-14) and (10-1-4) planes having an off angle of 65 ° with respect to the -10} plane; 15 ° off angles with respect to the {10-10} plane (20-21) ) Plane and (20-2-1) plane.

  In addition, the group III nitride semiconductor crystal of the present invention is characterized by having dislocations penetrating the surface of the main surface because it grows in the main surface direction. The dislocation penetrating the surface of the main surface corresponds to a dark spot that is observed when observed by cathodoluminescence (CL) measurement. Therefore, it can be said that the average dark spot density when the main surface of the crystal is observed by CL is the dislocation density penetrating the surface of the main surface.

The dislocation density of dislocations penetrating the surface of the main surface is not particularly limited, but is preferably 5 × 10 ⁴ cm ⁻² or more, more preferably 5 × 10 ⁵ cm ⁻² or more, and even more preferably 7 × 10 ⁵ cm ⁻² or more, preferably 2 × 10 ⁸ cm ⁻² or less. This is because by setting this range, it is possible to reduce the residual strain of the crystal and to suppress a decrease in light emission efficiency due to dislocation.

  Usually, since dislocations extend parallel to the growth direction of the crystal, for example, the ratio of penetrating dislocations on the main surface of the crystal obtained by slicing in the direction parallel to the growth direction is considered to be extremely low.

  The group III nitride semiconductor crystal of the present invention preferably has a thickness of 100 μm or more, more preferably 1 mm or more, and further preferably 5 mm or more. Moreover, it is preferable that it is usually 8 cm or less, and can also be 5 cm or less.

Also, the area of the main surface of the crystal may larger, for example, 100 mm ² or more it is possible to preferably be a 500 mm ² or more, more preferably, to greater than 750 mm ^2, be a 1500 mm ² or more Yes, it can be 2500 mm ² or more, and further can be 10000 mm ² or more.

  Further, in the group III nitride semiconductor crystal of the present invention, the off-angle distribution in the [0001] axis direction of the [10-10] axis per 2 inches is within ± 0.93 °, preferably ± 0.75 °. Within ± 0.50 °, more preferably within ± 0.30 °.

  That is, the group III nitride semiconductor crystal of the present invention has a uniform crystal axis in a single crystal, and the group III nitride semiconductor substrate obtained by slicing such a group III nitride semiconductor crystal has an internal structure. Thus, for example, when a light emitting device is manufactured, the problem that the emission wavelength varies as described above is solved.

  Further, in the case of the group III nitride semiconductor crystal of the present invention obtained by crystal growth on a plurality of seed substrates, for example, it is particularly preferable in that a large-area crystal can be obtained. The arrangement method as described above is preferable in that the crystal axes of the entire crystal obtained in a large area can be aligned over a wide range.

  As a feature in such a case, for example, in a crystal grown above the junction of the seed substrate, the off-angle change amount per 1 mm of the crystal tends to be larger than a crystal grown on a single seed substrate.

Therefore, in the group III nitride semiconductor crystal of the present invention, it is preferable that there is a region where the change in off-angle per 1 mm of crystal exceeds 0.015 °, and it is more preferable that a region exceeding 0.03 ° exists. Further, it is more preferable that a region exceeding 0.056 ° exists.

  In addition, in the group III nitride semiconductor crystal of the present invention, it is preferable that there are a plurality of regions where the off-angle change amount per 1 mm of crystal exceeds 0.03 °.

The group III nitride semiconductor crystal of the present invention preferably has a carrier concentration of 1 × 10 ^{18 to} 5 × 10 ¹⁸ cm ⁻³ .

(Use of nitride semiconductor crystals)
The nitride semiconductor crystal obtained by the production method of the present invention can be used for various applications. In particular, it is useful as a substrate for semiconductor devices such as light emitting diodes of ultraviolet, blue or green, etc., light emitting elements having relatively short wavelengths such as semiconductor lasers, and electronic devices. It is also possible to obtain a larger nitride semiconductor crystal by using the nitride semiconductor crystal manufactured by the manufacturing method of the present invention as a seed substrate.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example 1]
A rectangular parallelepiped having a length of 25 mm in the [11-20] direction and 5 mm in the [0001] direction and having a thickness of 330 μm,
One (10-10) plane gallium nitride seed substrate having an off angle of −0.30 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of -0.01 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of + 0.30 ° in the [0001] direction,
A total of three seed substrates with different off angles were prepared.

  The parallelism of the front and back surfaces of the seed substrate (10-10) surface was within 0.5 °. The (0001) plane and the (000-1) plane were selected as the bonding plane.

  As shown in FIG. 5 (a), three seed substrates are arranged in three rows in the [0001] direction so that the cross section of the (0001) plane and the cross section of the (000-1) plane face each other. Aligned on the susceptor so that the parallelism is within 5 °. The M axis ([10-10] axis) of the seed substrate arranged outside the M axis ([10-10] axis) of the seed substrate arranged in the center is directed from the back surface side to the front surface side with respect to the seed substrate. The seed substrates were lined up so as to face outward. Specifically, the off angles in the [0001] direction of the seed substrate were set to −0.30 °, −0.01 °, and + 0.30 ° from the [0001] side.

The susceptor was placed in the reactor 400, the temperature of the reaction chamber was raised to 1020 ° C., and a gallium nitride single crystal film was grown for 40 hours. In this single crystal growth step, the growth pressure is 1.01 × 10 ⁵ Pa, the partial pressure of the GaCl gas G3 is 1.85 × 10 ² Pa, and the partial pressure of the NH ₃ gas G4 is 7.05 × 10 ³ Pa. It was.

After the single crystal growth step is completed, the temperature is lowered to room temperature and the grown crystal is taken out. As a result, the region above the boundary region between the seed substrate and the seed substrate is coupled, and the outer periphery of the arranged seed is [1].
It was enlarged 2 mm each in the [1-20] direction and the [-1-120] direction, 2 mm in the [0001] direction, and 2 mm in the [000-1] direction. It grew 3.5 mm in the [10-10] direction. Three free-standing substrates having a rectangular (10-10) plane of 29 mm in the [11-20] direction, 19 mm in the [0001] direction, and a thickness of 330 μm as the main surface were produced by general slicing and polishing. The area of the main surface was 551 mm ² .

  When the off-angle of the M-axis ([10-10] axis) in the C-axis ([0001] axis) direction was measured by X-ray diffraction, A in FIG. 6 was −0.22 ° and B was −0.10. °, C was + 0.16 °. Further, the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained free-standing substrate surface was 0.37 °. Here, the tilt angle distribution is a variation in off-angle. Moreover, 2 inches converted as 50 mm.

  When the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained self-standing substrate surface was converted into 2 inches, it was ± 0.93 °. When the off-angle change amount in the region above the boundary region between the seed substrate and the seed substrate was measured, it was 0.13 ° / mm in the boundary region on the + C side and 0.07 ° / mm in the boundary region on the −C side. Met. The radius of curvature of the crystal axis in the C-axis ([0001] axis) direction was 1.5 m.

The X-ray rocking curve half-value width of the obtained self-supporting substrate was 56 seconds in (10-10) plane symmetry reflection when an X-ray beam was incident perpendicularly to the [0001] direction. About the obtained self-supporting substrate, the average dark spot density in the CL measurement in the region above the seed substrate was 4.8 × 10 ⁶ cm ⁻² , and the average in the CL measurement in the region above the boundary region between the seed and the seed The dark spot density was 2.6 × 10 ⁷ cm ⁻² .

  FIG. 5B schematically shows a manufacturing process of the gallium nitride substrate according to the first embodiment. In FIG. 5B, 501 is a seed substrate composed of three seed substrates having different off angles, 502 is a gallium nitride single crystal produced by growing on the seed substrate 501, and 503 is a gallium nitride single crystal 502. These are three (10-10) plane free-standing substrates manufactured by slicing at a broken line portion.

[Example 2]
As described below, the process was performed in the same manner as in Example 1 except that a seed substrate having a different off angle from that in Example 1 was used to sequentially arrange the seed substrate.

One (10-10) plane gallium nitride seed substrate having an off angle of −5.28 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of −5.03 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of −4.71 ° in the [0001] direction,
A total of three seed substrates with different off angles were prepared.

  The M axis ([10-10] axis) of the seed substrate arranged outside the M axis ([10-10] axis) of the seed substrate arranged in the center is directed from the back surface side to the front surface side with respect to the seed substrate. The seed substrates were lined up so as to face outward. Specifically, as shown in FIG. 7A, the off angles in the [0001] direction of the seed substrate are −5.28 °, −5.03 °, and −4.71 ° from the [0001] side. It was.

After the single crystal growth step is completed, the temperature is lowered to room temperature, and the grown crystal is taken out. As a result, the region above the boundary region between the seed substrate and the seed substrate is combined, and the outer periphery of the arranged seed substrate is [11-20]. ] And [-1-120] directions were enlarged by 2 mm, 2 mm in the [0001] direction, and 2 mm in the [000-1] direction. It grew 3.5 mm in the [10-10] direction. Three free-standing substrates having a rectangular (10-10) plane of 29 mm in the [11-20] direction, 19 mm in the [0001] direction, and a thickness of 330 μm as the main surface were produced by general slicing and polishing. The area of the main surface was 551 mm ² .

  When the off-angle of the M-axis ([10-10] axis) in the C-axis ([0001] axis) direction was measured by X-ray diffraction, A in FIG. 6 was −4.98 ° and B was −4.82. °, C was -4.62 °. Further, the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained free-standing substrate surface was 0.36 °.

  When the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained free-standing substrate surface was converted to 2 inches, it was ± 0.90 °. The radius of curvature of the crystal axis in the C-axis ([0001] axis) direction was 1.5 m. From this result, it was found that a self-supporting substrate having the same variation in the off-angle of the surface as in Example 1 was obtained.

  The X-ray rocking curve half-value width of the obtained self-supporting substrate was 47 seconds in (10-10) plane symmetry reflection when the X-ray beam was incident perpendicularly to the [0001] direction.

About the obtained self-supporting substrate, the average dark spot density in the CL measurement in the region above the seed substrate is 2.5 × 10 ⁶ cm ⁻² , and the CL measurement in the region above the boundary region between the seed substrate and the seed substrate is used. The average dark spot density was 7.5 × 10 ⁶ cm ⁻² .

  FIG. 7B schematically shows a manufacturing process of the gallium nitride substrate according to the second embodiment. In FIG. 7B, 701 is a seed substrate composed of three seed substrates having different off angles, 702 is a gallium nitride single crystal manufactured by growing on the seed substrate 701, and 703 is a gallium nitride single crystal 702. These are three (10-10) plane free-standing substrates manufactured by slicing at a broken line portion.

Example 3
As described below, the process was performed in the same manner as in Example 1 except that a seed substrate having a different off angle from that in Example 1 was used to sequentially arrange the seed substrate.

One (10-10) plane gallium nitride seed substrate having an off angle of −5.51 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of −5.01 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of −4.50 ° in the [0001] direction,
A total of three seed substrates with different off angles were prepared.

  The M axis ([10-10] axis) of the seed substrate arranged outside the M axis ([10-10] axis) of the seed substrate arranged in the center is directed from the back surface side to the front surface side with respect to the seed substrate. The seed substrates were lined up so as to face outward. Specifically, as shown in FIG. 8A, the off-angle in the [0001] direction of the seed substrate is −5.51 °, −5.01 °, −4.50 ° from the [0001] side. It was.

After the single crystal growth step is completed, the temperature is lowered to room temperature, and the grown crystal is taken out. As a result, the region above the boundary region between the seed substrate and the seed substrate is bonded, and the outer periphery of the arranged seed is [11-20]. Direction, [−1-120] direction 2 mm each, [0001] direction 2
mm, enlarged by 2 mm in the [000-1] direction. It grew 3.5 mm in the [10-10] direction. Three free-standing substrates having a rectangular (10-10) plane of 29 mm in the [11-20] direction, 19 mm in the [0001] direction, and a thickness of 330 μm as the main surface were produced by general slicing and polishing. The area of the main surface was 551 mm ² .

  When the off-angle of the M-axis ([10-10] axis) in the C-axis ([0001] axis) direction was measured by X-ray diffraction, A in FIG. 6 is −4.95 ° and B is −5.00. °, C was -5.04 °. In addition, the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained free-standing substrate surface was 0.09 °.

  When the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained self-standing substrate surface was converted into 2 inches, it was ± 0.23 °. The radius of curvature of the crystal axis in the C-axis ([0001] axis) direction was 6.0 m. From this result, it was found that a self-supporting substrate having a smaller variation in the off-angle of the surface than in Example 1 was obtained.

The X-ray rocking curve half-width of the obtained self-supporting substrate was 44 seconds in (10-10) plane symmetry reflection when the X-ray beam was incident perpendicularly to the [0001] direction. About the obtained self-supporting substrate, the average dark spot density in the CL measurement in the region above the seed substrate was 2.8 × 10 ⁶ cm ⁻² , and in the CL measurement in the region above the boundary region between the seed substrate and the seed substrate. The average dark spot density was 7.6 × 10 ⁶ cm ⁻² .

  FIG. 8B schematically shows a manufacturing process of the gallium nitride substrate according to the third embodiment. In FIG. 8B, 801 is a seed substrate composed of three seed substrates having different off angles, 802 is a gallium nitride single crystal manufactured by growing on the seed substrate 801, and 803 is a gallium nitride single crystal 802. These are three (10-10) plane free-standing substrates manufactured by slicing at a broken line portion.

Example 4
It is a rectangular parallelepiped with a length of 25 mm in the [11-20] direction and 5 mm in the [0001] direction and a thickness of 330 μm, and has an off-angle of −5.6 ° to −4.4 ° in the [0001] direction. Twenty (10-10) plane gallium nitride seed substrates were prepared.

  The parallelism of the front and back surfaces of the seed substrate (10-10) surface was within 0.5 °.

  The (0001) plane and the (000-1) plane were selected as the bonding plane.

  As shown in FIG. 9A, 20 seed substrates are arranged in 10 rows in the [0001] direction and 2 rows in the [11-20] direction, and the cross section of the (0001) plane and the cross section of the (000-1) plane face each other. Alternatively, they were arranged on the susceptor so that the cross-sections were parallel to each other within 0.5 ° so that the (11-20) plane and the (-1-120) plane face each other.

  The M-axis ([10-10] axis) of the outer seed substrate is always outside the M-axis ([10-10] axis) of the seed substrate on the center side from the back surface side to the front surface side with respect to the seed substrate. The seed substrates were lined up so as to face. That is, the off-angles in the [0001] direction of the seed substrates are arranged so that the off-angle value increases (the absolute value of the off-angle decreases) as it goes from [0001] to [000-1]. It was.

  The growth of the gallium nitride single crystal film was performed under the same conditions as in Example 1.

After the single crystal growth step is completed, the temperature is lowered to room temperature, and the grown crystal is taken out. As a result, the region above the boundary region between the seed substrate and the seed substrate is combined, and the outer periphery of the arranged seed substrate is [11-20]. ] And [-1-120] directions were enlarged by 2 mm, 2 mm in the [0001] direction, and 2 mm in the [000-1] direction. It grew 3.5 mm in the [10-10] direction. Three free-standing substrates having a main surface of (10-10) surface having a diameter of 2 inches and a thickness of 440 um were produced by general slicing and polishing. The area of the main surface was 1963 mm ² .

  The tilt angle distribution in the C-axis ([0001] axis) direction in the obtained free-standing substrate surface was measured by an X-ray diffraction method to be 0.941 ° and ± 0.47 ° for 2 inches. The radius of curvature of the crystal axis in the C-axis direction was 1.5 m.

The X-ray rocking curve half-width of the obtained self-supporting substrate was 45 seconds in (10-10) plane symmetry reflection when the X-ray beam was incident perpendicularly to the [0001] direction. About the obtained self-supporting substrate, the average dark spot density in the CL measurement in the region above the seed substrate was 2.7 × 10 ⁶ cm ⁻² , and in the CL measurement in the region above the boundary region between the seed substrate and the seed substrate. The average dark spot density was 8.1 × 10 ⁶ cm ⁻² .

  FIG. 9B schematically shows a manufacturing process of the gallium nitride substrate according to the fourth embodiment. In the drawing, reference numeral 901 denotes a seed substrate composed of three seed substrates having different off angles, and 902 denotes a seed substrate. A gallium nitride single crystal manufactured by growing it on 901, 903 indicates three (10-10) plane free-standing substrates manufactured by slicing the gallium nitride single crystal 902 at a broken line.

Example 5
The [11-20] axis has a length of 25 mm in the direction projected onto the (10-1-1) plane, and the [0001] axis has a length of 15 mm in the direction projected onto the (10-1-1) plane. A (10-1-1) plane gallium nitride seed having a rectangular parallelepiped of 330 μm and having off angles of −0.6 °, −0.2 °, + 0.2 °, and + 0.6 ° in the [0001] direction A total of 8 substrates were prepared.
The parallelism of the front and back surfaces of the seed substrate (10-1-1) surface is within 0.5 °.

As a bonding surface, a surface having an off angle of 28 ° in the [10-10] direction from the (0001) plane and a surface having an off angle of −28 ° in the [10-10] direction from the (000-1) plane ( The 11-20) plane and the (-1-120) plane were selected.
Eight seed substrates are arranged in 4 rows in the direction projected on the (10-1-1) plane of the [0001] axis and 2 rows in the [11-20] direction, and from the (0001) plane in the [10-10] direction. A plane having an off angle of 28 ° and a plane having an off angle of −28 ° in the [10-10] direction from the (000-1) plane face each other, or the (11-20) plane and the (−1−120) plane. Were arranged on the susceptor so that the cross-sections were parallel to each other within 0.5 °. The [10-1-1] axis of the outer seed substrate is always directed outward with respect to the seed substrate from the back surface side to the front surface side with respect to the [10-1-1] axis of the central seed substrate. A seed substrate was arranged. That is, the off-angles in the [0001] direction of the seed substrates are arranged so that the off-angle value increases (the absolute value of the off-angle decreases) as it goes from [0001] to [000-1]. It was.

The growth of the gallium nitride single crystal film was performed under the same conditions as in Example 1 except that the growth time was 78 hours.
After the single crystal growth step is completed, the temperature is lowered to room temperature, and the grown crystal is taken out. As a result, the region above the boundary region between the seed substrate and the seed substrate is bonded, and the enlarged growth of the outer peripheral portion of the seed substrate is 2 mm. It was the following. It grew 10.3 mm in the [10-1-1] direction. Three self-supporting substrates having a rectangular (10-10) plane of 20 mm in the [0001] direction, 50 mm in the [11-20] direction and a thickness of 440 μm as the main surface were produced by general slicing and polishing.

The tilt angle distribution in the C-axis ([0001] axis) direction of the M-axis ([10-10] axis) in the substrate plane was measured by X-ray diffractometry and found to be 0.352 °. When the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained self-standing substrate surface was converted into 2 inches, it was ± 0.44 °. The radius of curvature of the crystal axis in the C-axis ([0001] axis) direction was 1.6 m.
The X-ray rocking curve half-width of the obtained self-supporting substrate was 44 seconds in (10-10) plane symmetry reflection when the X-ray beam was incident perpendicularly to the [0001] direction. CL measurement is performed on the obtained self-supporting substrate, and dark spots having a density of 1 × 10 ⁶ cm ⁻² or more are observed in both the region above the seed substrate and the region above the boundary region between the seed substrate and the seed substrate. It was.

[Comparative Example 1]
As described below, the process was performed in the same manner as in Example 1 except that a seed substrate having a different off angle from that in Example 1 was used to sequentially arrange the seed substrate.
One (10-10) plane gallium nitride seed substrate having an off angle of + 0.01 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of -0.02 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of + 0.02 ° in the [0001] direction,
A total of three seed substrates were prepared.

  As shown in FIG. 10A, the off-angles in the [0001] direction of the seed substrate were + 0.01 °, −0.02 °, and + 0.02 ° from the [0001] side.

After the single crystal growth step is completed, the temperature is lowered to room temperature, and the grown crystal is taken out. As a result, the region above the boundary region between the seed substrate and the seed substrate is combined, and the outer periphery of the arranged seed substrate is [11-20]. ] And [-1-120] directions were enlarged by 2 mm, 2 mm in the [0001] direction, and 2 mm in the [000-1] direction. It grew 3.5 mm in the [10-10] direction. Three free-standing substrates having a rectangular (10-10) plane of 29 mm in the [11-20] direction, 19 mm in the [0001] direction, and a thickness of 330 μm as the main surface were produced by general slicing and polishing. The area of the main surface was 551 mm ² .

  When the off-angle in the C-axis ([0001] axis) direction was measured by X-ray diffraction, it was −0.36 ° for A, −0.03 ° for B, and + 0.30 ° for C in FIG. . In addition, the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained free-standing substrate surface was 0.66 °.

  When the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained self-standing substrate surface was converted into 2 inches, it was ± 1.65 °. The radius of curvature of the crystal axis in the C-axis ([0001] axis) direction was 0.8 m. From this result, it was found that a self-supporting substrate having a larger variation in the surface off-angle than Example 1 was obtained.

The X-ray rocking curve half-value width of the obtained self-supporting substrate was 57 seconds in (10-10) plane symmetry reflection when the X-ray beam was incident perpendicularly to the [0001] direction. About the obtained self-supporting substrate, the average dark spot density in the CL measurement in the region above the seed substrate is 4.6 × 10 ⁶ cm ⁻² , and the CL measurement in the region above the boundary region between the seed substrate and the seed substrate is used. The average dark spot density was 2.3 × 10 ⁷ cm ⁻² .

FIG. 10B schematically shows a manufacturing process of a gallium nitride substrate according to the comparative example 1. In FIG. 10, 1001 is a seed substrate composed of three seed substrates whose off angles hardly change, and 1002 is a seed substrate. A gallium nitride single crystal manufactured by growing on the seed substrate 1001, and 1003 includes three (1
0-10) A plane free-standing substrate.

[Comparative Example 2]
As described below, the process was performed in the same manner as in Example 1 except that a seed substrate having a different off angle from that in Example 1 was used to sequentially arrange the seed substrate.
One (10-10) plane gallium nitride seed substrate having an off angle of −4.99 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of −5.01 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of -5.00 ° in the [0001] direction,
A total of three seed substrates were prepared.

  As shown in FIG. 11A, the off-angles in the [0001] direction of the seed substrate were −4.99 °, −5.01 °, and −5.00 ° from the [0001] side.

After the single crystal growth step is completed, the temperature is lowered to room temperature, and the grown crystal is taken out. As a result, the region above the boundary region between the seed substrate and the seed substrate is combined, and the outer periphery of the arranged seed substrate is [11-20]. ] And [-1-120] directions were enlarged by 2 mm, 2 mm in the [0001] direction, and 2 mm in the [000-1] direction. It grew 3.5 mm in the [10-10] direction. Three free-standing substrates having a rectangular (10-10) plane of 29 mm in the [11-20] direction, 19 mm in the [0001] direction, and a thickness of 330 μm as the main surface were produced by general slicing and polishing. The area of the main surface was 551 mm ² .

  The off-angle in the C-axis ([0001] axis) direction was measured by X-ray diffraction. As a result, A in FIG. 6 was −5.31 °, B was −4.99 °, and C was −4.68 °. It was. In addition, the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained self-supporting substrate surface was 0.63 °.

  When the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained self-standing substrate surface was converted into 2 inches, it was ± 1.58 °. The radius of curvature of the crystal axis in the C-axis ([0001] axis) direction was 0.9 m. As described above, a self-supporting substrate having a larger variation in the off angle of the surface than in Example 1 was obtained.

The X-ray rocking curve half-width of the obtained self-supporting substrate was 45 seconds in (10-10) plane symmetry reflection when the X-ray beam was incident perpendicularly to the [0001] direction. About the obtained self-standing substrate, the average dark spot density in the CL measurement in the region above the seed substrate is 3.0 × 10 ⁶ cm ⁻² , and in the CL measurement in the region above the boundary region between the seed substrate and the seed substrate. The average dark spot density was 9.0 × 10 ⁷ cm ⁻² .

  FIG. 11B schematically shows a manufacturing process of a gallium nitride substrate according to the comparative example 2. In FIG. 11B, reference numeral 1101 denotes a seed substrate composed of three seed substrates whose off angles hardly change. A gallium nitride single crystal 1103 manufactured by growing on the seed substrate 1101 indicates three (10-10) plane free-standing substrates manufactured by slicing the gallium nitride single crystal 1102 at a broken line.

[Comparative Example 3]
As described below, the process was performed in the same manner as in Example 1 except that a seed substrate having a different off angle from that in Example 1 was used to sequentially arrange the seed substrate.
One (10-10) plane gallium nitride seed substrate having an off angle of −5.01 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of -5.00 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of −4.98 ° in the [0001] direction,
A total of three seed substrates were prepared.

  The seed substrates were arranged such that the M axis ([10-10] axis) of the seed substrate arranged outside faces the M axis ([10-10] axis) of the seed substrate arranged in the center. Specifically, as shown in FIG. 12A, the off angles in the [0001] direction of the seed substrate are −5.01 °, −5.00 °, and −4.98 ° from the [0001] side. It was.

After the single crystal growth step is completed, the temperature is lowered to room temperature, and the grown crystal is taken out. As a result, the region above the boundary region between the seed substrate and the seed substrate is bonded, and the outer periphery of the arranged seed is [11-20]. The direction was enlarged by 2 mm each in the direction and the [−1-120] direction, 2 mm in the [0001] direction, and 2 mm in the [000-1] direction. It grew 3.5 mm in the [10-10] direction. Three free-standing substrates having a rectangular (10-10) plane of 29 mm in the [11-20] direction, 19 mm in the [0001] direction, and a thickness of 330 μm as the main surface were produced by general slicing and polishing. The area of the main surface was 551 mm ² .

  The off-angle in the C-axis ([0001] axis) direction was measured by X-ray diffraction. As a result, A in FIG. 6 was −5.25 °, B was −5.00 °, and C was −4.77 °. It was. In addition, the tilt angle distribution in the C-axis direction in the obtained free-standing substrate surface was 0.48 °.

  When the tilt angle distribution in the C-axis ([0001] axis) direction was converted to 2 inches, it was ± 1.20 °. The radius of curvature of the crystal axis in the C-axis ([0001] axis) direction was 1.1 m. As described above, a self-supporting substrate having a larger variation in the off angle of the surface than in Example 1 was obtained.

The X-ray rocking curve half-value width of the obtained self-supporting substrate was 46 seconds in (10-10) plane symmetry reflection when an X-ray beam was incident perpendicularly to the [0001] direction. About the obtained self-supporting substrate, the average dark spot density in the CL measurement in the region above the seed substrate was 2.8 × 10 ⁶ cm ⁻² , and in the CL measurement in the region above the boundary region between the seed substrate and the seed substrate. The average dark spot density was 8.1 × 10 ⁷ cm ⁻² .

  FIG. 12B schematically shows a manufacturing process of a gallium nitride substrate according to the comparative example 3. In the figure, reference numeral 1201 denotes a seed substrate composed of three seed substrates whose off angles hardly change, and 1202 denotes A gallium nitride single crystal 1203 manufactured by growing on the seed substrate 1201 indicates three (10-10) plane free-standing substrates manufactured by slicing the gallium nitride single crystal 1202 at a broken line.

[Comparative Example 4]
As described below, the process was performed in the same manner as in Example 1 except that a seed substrate having a different off angle from that in Example 1 was used to sequentially arrange the seed substrate.

One (10-10) plane gallium nitride seed substrate having an off angle of −4.71 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of −5.03 ° in the [0001] direction;
One (10-10) plane gallium nitride seed substrate having an off angle of −5.28 ° in the [0001] direction,
A total of three seed substrates with different off angles were prepared.

  The seed substrates were arranged so that the M axis ([10-10] axis) of the seed substrate arranged on the outside faces the M axis ([10-10] axis) of the seed substrate arranged in the center. Specifically, as illustrated in FIG. 13A, the off-angle in the [0001] direction of the seed substrate is −4.71 °, −5.03 °, −5.28 ° from the [0001] side. It was.

After the single crystal growth step is completed, the temperature is lowered to room temperature, and the grown crystal is taken out. As a result, the region above the boundary region between the seed substrate and the seed substrate is bonded, and the outer periphery of the arranged seed is [11-20]. The direction was enlarged by 2 mm each in the direction and the [−1-120] direction, 2 mm in the [0001] direction, and 2 mm in the [000-1] direction. It grew 3.5 mm in the [10-10] direction. Three free-standing substrates having a rectangular (10-10) plane of 29 mm in the [11-20] direction, 19 mm in the [0001] direction, and a thickness of 330 μm as the main surface were produced by general slicing and polishing. The area of the main surface was 551 mm ² .

  When the off-angle in the C-axis ([0001] axis) direction was measured by X-ray diffraction, it was −5.61 ° at A, −5.00 ° at B, and −4.42 ° at C in FIG. It was. Further, the tilt angle distribution in the C-axis ([0001] axis) direction in the obtained free-standing substrate surface was 1.19 °.

  When the tilt angle distribution in the C-axis ([0001] axis) direction was converted to 2 inches, it was ± 2.98 °. The radius of curvature of the crystal axis in the C-axis ([0001] axis) direction was 0.5 m. As described above, a self-supporting substrate having a larger variation in the off angle of the surface than in Example 1 was obtained.

The X-ray rocking curve half-width of the obtained self-supporting substrate was 45 seconds in (10-10) plane symmetry reflection when the X-ray beam was incident perpendicularly to the [0001] direction. About the obtained self-supporting substrate, the average dark spot density in the CL measurement in the region above the seed substrate is 2.6 × 10 ⁶ cm ⁻² , and in the CL measurement in the region above the boundary region between the seed substrate and the seed substrate. The average dark spot density was 8.5 × 10 ⁷ cm ⁻² .

  FIG. 13B schematically shows a manufacturing process of a gallium nitride substrate according to the comparative example 4. In the figure, reference numeral 1301 denotes a seed substrate composed of three seed substrates whose off angles hardly change, and 1302 denotes A gallium nitride single crystal manufactured by growing it on the seed substrate 1301, 1303 shows three (10-10) plane free-standing substrates manufactured by slicing the gallium nitride single crystal 1302 at a broken line.

  Table 1 shows the results of evaluation of the seed substrate conditions of Examples 1 to 4 and Comparative Examples 1 to 4 and the grown gallium nitride single crystal. Table 2 shows the seed substrate conditions of Example 5 and the results of evaluation of the grown gallium nitride single crystal. By using the seed substrate conditions of Examples 1 to 5, it was possible to obtain a nitride semiconductor crystal with a small variation in the off-angle of the surface.

[Reference example]
As described below, unlike Example 1, it was carried out in the same manner as Example 1 except that a plurality of seed substrates were not arranged and grown on one seed.

  It is a rectangular parallelepiped having a length of 25 mm in the [11-20] direction and 5 mm in the [0001] direction, a thickness of 330 μm, and an off angle of −0.240 ° in the [0001] direction (10− 10) One surface gallium nitride seed substrate was prepared.

After the single crystal growth step is completed, the temperature is lowered to room temperature, and the grown crystal is taken out. As a result, the outer periphery of the seed substrate is 2 mm in each of the [11-20] direction and the [-1-120] direction, [0001] It was enlarged 2 mm in the direction and 2 mm in the [000-1] direction. It grew 3.5 mm in the [10-10] direction. Three free-standing substrates having a rectangular (10-10) plane of 29 mm in the [11-20] direction, 9 mm in the [0001] direction, and a thickness of 330 μm as the main surface were produced by general slicing and polishing. The area of the main surface was 261 mm ² .

  When the off-angle in the C-axis ([0001] axis) direction was measured by an X-ray diffraction method, the tilt angle distribution in the C-axis ([0001] axis) direction in the substrate plane was 0.22 °. When the tilt distribution in the C-axis ([0001] axis) direction was converted to 2 inches, it was ± 0.61 °. The off-angle change amount was 0.012 ° / mm.

  The present application is effective in manufacturing a semiconductor substrate having a large area mainly used for mass production of semiconductor elements and reducing variations in quality of semiconductor elements mass-produced by the semiconductor substrate.

101 Seed substrate 102 with uniform off angles 102 Substrate manufactured by slicing a nitride semiconductor crystal 103 102 grown on 101 with a broken line 201 Nitride semiconductor grown on a plurality of seed substrates 202 201 having different off angles Substrate 400 manufactured by slicing with a broken line of crystal 203 202 Reactor 401 Pipe for carrier gas 402 Pipe for dopant gas 403 Group III raw material pipe 404 Group V raw material pipe 405 HCl gas pipe 405 Group III raw material reservoir 406 Heater 407 Susceptor 408 Exhaust pipe 501 Seed substrate in Example 1 and its arrangement 502 501 Substrate produced by slicing with a broken line of gallium nitride single crystal 503 502 grown on 501 Seed substrate in Example 2 and its arrangement 702 701 Grown on Substrate 801 produced by slicing with broken line of gallium nitride single crystal 703 702 The seed substrate in Example 3 and substrate 901 produced by slicing with broken line of gallium nitride single crystal 803 802 grown on its arrangement 802 801 Seed substrate in Example 4 and substrate 1001 manufactured by slicing with a broken line of gallium nitride single crystal 903 902 grown on its arrangement 902 901, grown on seed substrate in its comparative example 1 and its arrangement 1002 1001 Substrate 1101 manufactured by slicing a gallium nitride single crystal 1003 1002 with a dashed line Substrate 1201 manufactured by slicing a seed substrate in Comparative Example 2 and a gallium nitride single crystal 1103 1102 grown on its arrangement 1102 1101 Seed in Example 3 Substrate, and substrate 1301 manufactured by slicing with a dashed line of gallium nitride single crystal 1203 1202 grown on its arrangement 1202 1201 Seed substrate in Comparative Example 4, and gallium nitride single crystal grown on its arrangement 1302 1301 1303 Substrate G1 produced by slicing along the broken line 1302 Carrier gas G2 Dopant gas G3 Group III source gas G4 Group V source gas

Claims (7)

A step of growing a single nitride semiconductor layer on a plurality of seed substrates made of a hexagonal nitride semiconductor to obtain a nitride semiconductor crystal, and a step of slicing the nitride semiconductor crystal into a substrate. In a method for manufacturing a nitride semiconductor substrate having
The plurality of seed substrates have non-polar or semipolar growth surfaces;
At least one of the plurality of seed substrates has a different off-angle in the [0001] axis direction from other seed substrates,
The single nitride is disposed by arranging the plurality of seed substrates such that an off-angle distribution in the [0001] axis direction of the substrate is smaller than an off-angle distribution in the [0001] axis direction of the plurality of seed substrates. A method for manufacturing a nitride semiconductor substrate, comprising growing a semiconductor layer.   The manufacturing method according to claim 1, wherein the growth surfaces of the plurality of seed substrates are substantially {10-10} planes.   The manufacturing method according to claim 2, wherein the at least one seed substrate differs from the other seed substrate only in an off angle in the [0001] axis direction.   The manufacturing method according to claim 1, wherein the growth surfaces of the plurality of seed substrates are substantially {11-20} planes.   The growth surfaces of the plurality of seed substrates are substantially {11-20} planes, and the at least one seed substrate differs from the other seed substrates only in the off-angle in the [0001] axis direction. The manufacturing method according to claim 4.   6. The manufacturing method according to claim 1, wherein the plurality of seed substrates are arranged by gradually changing an off angle in a [0001] axial direction. The manufacturing method according to claim 1, wherein the single nitride semiconductor layer is at least one selected from gallium nitride, aluminum nitride, indium nitride, and mixed crystals thereof.

Images