JP6455575B2 - Method for manufacturing group 13 metal nitride substrate - Google Patents

Description

  The present invention relates to a method for manufacturing a Group 13 metal nitride substrate. Specifically, the present invention relates to a method for manufacturing a Group 13 metal nitride substrate, which can efficiently obtain a large substrate with extremely good crystal quality.

Periodic table group 13 metal nitride semiconductors typified by gallium nitride (GaN) have a large band gap, and the transition between bands is a direct transition type. It is put to practical use as a light emitting element on the relatively short wavelength side.
These devices are preferably manufactured using a high-quality semiconductor substrate (free-standing substrate) made of the same kind of material and having few crystal defects, and a periodic table Group 13 metal nitride that can be such a semiconductor substrate. A technique for producing a crystal (hereinafter sometimes simply referred to as a group 13 nitride crystal) has been actively studied.

As a method for producing a Group 13 nitride crystal, a vapor phase growth method such as a hydride vapor phase growth method (HVPE method), a liquid phase growth method such as a flux method, an ammonothermal method, and the like are known. The HVPE method is a method in which Ga chloride and a hydride (NH ₃ ) of a Group 5 element in a periodic table are introduced into a furnace and thermally decomposed in a hydrogen stream, and crystals generated by the thermal decomposition are deposited on the substrate. is there. On the other hand, the ammonothermal method is a method for producing a desired crystal material using a solvent containing nitrogen such as ammonia in a supercritical state and / or a subcritical state and a dissolution-precipitation reaction of raw materials. When applied to crystal growth, crystals are precipitated by generating a supersaturated state due to a temperature difference utilizing the temperature dependence of the raw material solubility in a nitrogen-containing solvent such as ammonia. Specifically, a crystal raw material or seed crystal is placed in a pressure-resistant container such as an autoclave and sealed, and heated with a heater or the like to form a high-temperature region and a low-temperature region in the pressure-resistant container. Crystals can be produced by dissolving and growing crystals on the other hand.

  In general, a periodic table group 13 metal nitride substrate (hereinafter sometimes simply referred to as a group 13 metal nitride substrate or a group 13 nitride substrate) is formed on the main surface of the seed crystal using the above-described method. The bulk crystal grown in this manner can be obtained by processing such as slicing. However, the conventionally known bulk crystal growth method has a problem that crystal defects and warpage existing in the seed crystal are inherited by the bulk crystal. As one method for solving such a problem, an ELO method (Epitaxial Lateral Overgrowth) is known. The ELO method is a crystal growth method in which a mask layer is formed on the main surface of the seed crystal and laterally grown on the mask from the opening by a vapor phase growth method. However, since dislocations are stopped by the lateral growth, the layer has few crystal defects. It is known that can be formed (see Patent Document 1).

  As another method, for example, Patent Document 2 discloses a method of obtaining a plate-like crystal whose area is enlarged by widening the C-plane by performing crystal growth in a direction perpendicular to the c-axis using an elongated seed. Has been.

JP-A-11-251253 Special table 2008-521737 gazette

  When the present inventors diligently studied the liquid phase growth method represented by the ammonothermal method, when a bulk crystal was grown on the main surface of the seed crystal, crystal defects and It has been found that there is a new problem that it is difficult to obtain large-sized and high-quality crystals because cracks are generated not only due to the propagation of warp but also due to the propagation of crystal defects and warp. Furthermore, since the liquid phase growth method is generally slower in growth rate than the vapor phase growth method, the growth of expanding the area by lateral growth as in Patent Document 2 requires a very long time, and the productivity. From the point of view, it was not realistic. Furthermore, even when lateral growth is used, when a plate-like crystal having a polar surface as the main surface is grown, it is predicted that distortion will occur in the crystal due to the difference in polarity between the front and back surfaces. When processing such as slicing and polishing is performed on the bulk crystal obtained by such a method, cracks and large cracks occur during the processing, and it is difficult to obtain a semiconductor substrate with a high yield. It has been found that there is a serious problem.

  Accordingly, in the present invention, a large-scale and high-quality Group 13 metal nitride substrate manufacturing method, in which the generation of crystal defects, warpage, and cracks is small and the generation of cracks during processing can be suppressed. It is an object of the present invention to provide a method for manufacturing a nitride substrate.

As a result of intensive studies, the inventors of the present invention performed crystal growth after coating one main surface of a seed crystal having a polar surface as a main surface with a growth-inhibiting member, and seeding the other main surface existing on the back side. It has been found that the above problem can be solved by removing the crystal and further growing the crystal to obtain a plate-like substrate from the other main surface side existing on the back side.
That is, the present invention is as follows.
[1] A seed crystal having a polar surface as a main surface, a front main surface and a back main surface, wherein at least a part of the front main surface is coated with a growth inhibiting member. Preparing a seed crystal having a stripe pattern having a plurality of line-shaped openings; and
A first growth step of growing a first Group 13 metal nitride crystal from a plurality of the line-shaped openings in a direction perpendicular to the main surface on the front side;
A removal step of removing part or all of the seed crystal from the main surface on the back side until the first Group 13 metal nitride crystal grown in the first growth step is exposed;
A second growth step of growing a second group 13 metal nitride crystal from the first group 13 metal nitride crystal exposed in the removing step in a direction parallel to at least the main surface on the back side;
Cutting and / or grinding the second group 13 metal nitride crystal grown in the second growth step to obtain a plate-shaped group 13 metal nitride substrate,
In the first growth step, first group 13 metal nitride crystals grown from a plurality of line-shaped openings are grown so as to be connected to each other,
In the removing step, the exposed first group 13 metal nitride crystal has a plurality of surfaces parallel to the main surface of the seed crystal,
In the second growth step, the group 13 metal nitride is grown until a plurality of second group 13 metal nitride crystals grown from the first group 13 metal nitride crystal are joined to each other. Manufacturing method of physical substrate.
[2] The method for producing a Group 13 metal nitride substrate according to [1], wherein a main surface on the front side of the seed crystal is a -C plane and a main surface on the back side is a + C plane.
[3] The method for manufacturing a Group 13 metal nitride substrate according to [1] or [2], wherein the plurality of line-shaped openings form a stripe pattern extending in the a-axis direction.
[4] The method for manufacturing a Group 13 metal nitride substrate according to [1] or [2], wherein the plurality of line-shaped openings form a stripe pattern extending in the m-axis direction.
[5] The method for producing a Group 13 metal nitride substrate according to any one of [1] to [4], wherein the width W ₁ of the growth inhibition member of the stripe pattern is ₁ mm to 20 mm.
[6] In the first growth step, plate-like Group 13 metal nitride crystals are grown in a direction perpendicular to the main surface on the front side from the plurality of line-shaped openings, [1] to [1] to The method for producing a Group 13 metal nitride substrate according to any one of [5].
[7] The group 13 according to any one of [1] to [6], wherein the growth surface of the second group 13 metal nitride crystal is grown to a continuous flat surface in the previous second growth step. A method for manufacturing a metal nitride substrate.
[8] The method according to any one of [1] to [7], wherein the first growth step and the second growth step are performed by crystal growth in a solvent in a supercritical state and / or a subcritical state. A method for manufacturing a Group 13 metal nitride substrate.
[9] The method for producing a Group 13 metal nitride substrate according to any one of [1] to [8], wherein the main surface of the Group 13 metal nitride substrate is a polar surface.

  According to the present invention, there is provided a large and high-quality Group 13 metal nitride substrate manufacturing method, which is less likely to cause crystal defects, warpage and cracks, and can suppress the occurrence of cracks during processing. A method for manufacturing a metal nitride substrate can be provided.

FIG. 1 is a schematic view of a crystal manufacturing apparatus that can be used in the present invention. FIG. 2 is a schematic view of another crystal manufacturing apparatus that can be used in the present invention. FIG. 3 is a conceptual diagram for explaining a series of steps of the production method of the present invention. FIG. 4 is a conceptual diagram for illustrating a specific example in the case where a plurality of line-shaped openings are provided. FIG. 5 is a conceptual diagram for illustrating a specific example of crystal growth in the first growth step. FIG. 6 is a conceptual diagram for illustrating a specific example of crystals obtained in the removing step. FIG. 7 is a graph showing the XRC half width of the GaN substrate obtained in Example 1. FIG. 8 is a graph showing the XRC half width of the GaN crystal obtained in Comparative Example 1. FIG. 9 is a graph showing the XRC half width of the GaN crystal obtained in Comparative Example 2.

Hereinafter, a method for producing a periodic table group 13 metal nitride substrate (hereinafter referred to as a group 13 nitride substrate) of the present invention will be described in detail.
The description of the constituent elements described below may be made based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples.
In addition, the numerical value range represented using "to" in this application means the range which includes the numerical value described before and behind "to" as a lower limit and an upper limit. Further, the Miller index in the present application is described by adding a minus sign in front of the index when the index is negative. Further, in this specification, the notation <...> Represents a collective expression of directions, and the notation [...] Represents an individual expression of directions. On the other hand, the notation {...} Represents the collective expression of the faces, and the notation (...

In this specification, the “off angle” is an angle representing a deviation of a certain surface from the exponential surface.
In the present specification, the “main surface” means the widest surface among the surfaces existing in the crystal, and the “main surface” of the seed crystal usually exists substantially parallel to the front and back surfaces, Are referred to as the “main surface” and “the back main surface”.
In the present specification, the “C plane” is a {0001} plane in a hexagonal crystal structure (wurtzite crystal structure) and is a plane orthogonal to the c-axis. Such a plane is a polar plane. In the Group 13 metal nitride crystal, the “+ C plane” is a Group 13 metal plane (gallium plane in the case of gallium nitride), and the “−C plane” is a nitrogen plane.

In the present specification, the “M plane” is a plane equivalent to the {1-100} plane, specifically, a (1-100) plane, a (01-10) plane, a (−1010) plane, The (−1100) plane, (0-110) plane, or (10-10) plane is a plane orthogonal to the m-axis. Such a surface is a nonpolar surface and is usually a cleaved surface.
In the specification of the present application, the “A plane” is a plane equivalent to the {2-1-10} plane, specifically, the (2-1-10) plane, the (-12-10) plane, ( A (1-120) plane, a (-2110) plane, a (1-210) plane, or a (11-20) plane, which is a plane orthogonal to the a-axis. Such a surface is a nonpolar surface. In this specification, “c-axis”, “m-axis”, and “a-axis” mean axes perpendicular to the C-plane, M-plane, and A-plane, respectively.

  Further, in the present specification, the “semipolar plane” means, for example, that when the group 13 metal nitride crystal is a hexagonal crystal and the main surface is represented by (hklm), at least one of h, k, and l Two are non-zero and m is non-zero. Further, the semipolar plane is a C plane, that is, a plane inclined with respect to the {0001} plane, where both or only one of group 13 metal element and nitrogen element in the periodic table is present on the surface, and the abundance ratio thereof. Means a surface that is not 1: 1. h, k, l, and m are each independently preferably an integer of -5 to 5, more preferably an integer of -3 to 3, and preferably a low index surface. . Specifically, for example, {20-21} plane, {20-2-1} plane, {30-31} plane, {30-3-1} plane, {10-11} plane, {10-1- 1} plane, {10-12} plane, {10-1-2} plane, {11-22} plane, {11-2-2} plane, {11-21} plane, {11-2-1} Low index surface such as surface.

  Further, in this specification, when referring to the C, M, A, or specific index plane, a range having an off angle within 10 ° from each crystal axis measured with an accuracy within ± 0.01 °. Including the inner face. The off angle is preferably within 5 °, more preferably within 3 °. Similarly, when referring to specific axial directions such as the c-axis, m-axis, and a-axis, the direction including an off angle of 10 ° or less is included. The off angle is preferably within 5 °, more preferably within 3 °.

<Method for Producing Group 13 Metal Nitride Substrate>
The method for producing a Group 13 metal nitride substrate (hereinafter sometimes referred to as a Group 13 nitride substrate) of the present invention includes the following steps (1) to (5).
(1) A seed crystal having a polar surface as a main surface and having a main surface on the front side and a main surface on the back side, and covering at least a part of the main surface on the front side with a growth inhibiting member A preparation step of preparing a seed crystal in which a stripe pattern having a plurality of line-shaped openings is formed. (2) From the plurality of line-shaped openings, the first crystal is perpendicular to the main surface on the front side. Group 13 metal nitride crystals (hereinafter sometimes referred to as first Group 13 nitride crystals) are grown, and the first Group 13 nitride crystals grown from the plurality of line-shaped openings are, First growth step of growing so as to be connected to each other (3) Part or all of the seed crystal from the main surface on the back side until the first group 13 nitride crystal grown in the first growth step is exposed The exposed first group 13 nitride crystal has a plurality of planes parallel to the main surface of the seed crystal. (4) From the first group 13 nitride crystal exposed in the removal step, at least a second group 13 metal nitride crystal (hereinafter referred to as a direction parallel to the main surface on the back side). And may be referred to as a second group 13 nitride), and is grown until a plurality of second group 13 nitride crystals grown from the first group 13 nitride crystal are joined together. Two-growth step (5) Substrate manufacturing step of obtaining a plate-like group 13 metal nitride substrate by cutting and / or grinding the second group 13 metal nitride crystal grown in the second growth step. FIG. 3 is a conceptual diagram illustrating a series of steps of the manufacturing method. Hereinafter, a case where a GaN crystal is grown as a Group 13 metal nitride crystal will be described as an example. However, the manufacturing method of the present invention is limited to this. Not.

FIG. 3A is a cross-sectional view of a seed crystal in which a stripe pattern having a plurality of line-shaped openings is formed by covering with a growth inhibiting member in the preparation step. A stripe pattern extending parallel to the a-axis direction is formed by the mask 102 on the −C plane as the main surface on the front side of the seed crystal 101. Next, FIG. 3B shows a state in which the first GaN crystal 104 is grown in the first growth step, where (b-1) shows a top view on the −C plane side, and (b-2) shows Sectional drawing in AA 'is shown. A GaN crystal 104 grows in the −c-axis direction from the line-shaped opening 103, and a plate-like crystal is formed. Further, since the GaN crystal 104 also grows in the −c-axis direction from the side surface of the seed crystal, a frame-like crystal grows so as to surround the outer periphery of the seed crystal, and the plate crystals are connected at the end. Further, FIG. 3C shows a state in which the seed crystal is removed from the + C plane which is the main surface on the back side in the removing step, and (c-1) shows a top view on the −C plane side, 2) shows a cross-sectional view at AA ′. The seed crystal 101 is completely removed, and a GaN crystal frame 105 in which the + C plane of the first GaN crystal 104 is exposed is obtained. Since the seed crystal 101 is completely removed, the plate-like crystals of the GaN crystal frame are not connected to each other and become a cavity, and are connected and integrated only by the frame-like crystal existing at the end of the plate-like crystal. A GaN crystal frame 105 is formed. FIG. 3D shows a state in which the second GaN crystal 106 is grown in the second growth step. The second GaN crystal 106 is grown in the lateral direction (direction parallel to the + C plane) from the + C plane of the GaN crystal frame 105 made of the exposed first GaN crystal 104 as shown in (d-1). When the crystal growth is continued, the second GaN crystals 106 that have started growing from the + C plane of each plate-like crystal as shown in (d-2) are joined together to form an integral GaN crystal. Finally, FIG. 3E is a cross-sectional view of the plate-like GaN substrate 107 obtained by removing the GaN crystal frame 105 from the second GaN crystal 106 in the substrate manufacturing process. By separating at least the first GaN crystal 104 from the second GaN crystal 106 by cutting and / or grinding, a plate-like GaN substrate 107 having a large-diameter C-plane as a main surface is obtained.
Below, it demonstrates still in detail about each process.

[Preparation process]
The preparatory process according to the method for manufacturing a Group 13 metal nitride substrate of the present invention is “a seed crystal having a polar surface as a main surface and a main surface on the front side and a main surface on the back side, A step of preparing a seed crystal in which a stripe pattern having a plurality of line-shaped openings is formed by covering at least a part of the main surface on the front side with a growth inhibiting member ”. The preparation step may be a step of covering at least a part of the main surface of the seed crystal with the growth inhibiting member, or obtaining a seed crystal having at least a part of the main surface coated with the growth inhibiting member. May be.

(Seed crystal)
Examples of the seed crystal in the production method of the present invention include a Group 13 metal nitride represented by GaN, or a substrate such as sapphire, Si, SiC, Ga ₂ O ₃ , GaAs, ZnO (zinc oxide). It is preferably at least one crystal selected from the group consisting of Group 13 metal nitrides, sapphire, GaAs, zinc oxide, Si and SiC. Further, among the group 13 metal nitrides, the same type of crystal as the group 13 metal nitride crystal grown thereon is preferable. For example, when it is intended to obtain a GaN substrate by growing a GaN crystal, the seed crystal is also preferably made of GaN. Examples of the Group 13 metal nitride crystal include AlN, InN, or a mixed crystal thereof in addition to GaN. Examples of the mixed crystal include AlGaN, InGaN, AlInN, and AlInGaN. Preferred is a mixed crystal containing GaN and Ga, and more preferred is GaN. In the case where a substrate containing a different type of crystal from the Group 13 metal nitride crystal grown thereon is used as a seed crystal, a crystal layer made of the Group 13 metal nitride crystal is formed on the different type of crystal. It is preferable to use a thing (template substrate).

The shape of the main surface of the seed crystal is not particularly limited, and examples thereof include a quadrangle, a hexagon, a dodecagon, a circle, and an ellipse, and it is easy to produce a circular wafer as the finally obtained group 13 nitride substrate. Therefore, it is preferable that the shape is a quadrangle, a hexagon, or a circle.
The maximum diameter of the main surface of the seed crystal is preferably 10 mm or more, more preferably 15 mm or more, further preferably 20 mm or more, and usually 150 mm or less. By setting the lower limit value or more, the size of the main surface of the obtained group 13 nitride substrate tends to be larger. The maximum diameter of the main surface means the diameter when the shape of the main surface is circular, and the maximum length of the main surface when the shape is other than circular.

  The crystal plane of the main surface of the seed crystal is a polar plane, and when the seed crystal is a hexagonal material such as a group 13 metal nitride, it is the {0001} plane. The main surface exists on the front side and the back side, and these exist as substantially parallel surfaces. The front side and the back side may be determined in any way. However, when the growth process described later is performed by the ammonothermal method, the main surface on the front side is − The C surface is preferable, and the main surface on the back surface side is preferably the + C surface.

The thickness of the seed crystal is not particularly limited, but is preferably 100 μm or more, and more preferably 200 μm or more.
The crystal growth method of the seed crystal is not limited at all. However, when a group 13 metal nitride crystal such as GaN is used as the seed crystal, a hydride vapor phase growth method (HVPE method), a metal organic chemical vapor deposition method (MOCVD method). ), Crystal grown by vapor phase growth method such as metal organic chloride vapor phase growth method (MOC method), molecular beam epitaxy method (MBE method), liquid phase epitaxy method (LPE method), flux It may be a crystal grown by a liquid phase growth method such as a method or an ammonothermal method (in this specification, the ammonothermal method is classified and handled as a liquid phase growth method). Among these, from the viewpoint of using a seed crystal having a large main surface area, a crystal obtained by the HVPE method with high growth efficiency is preferable.

(Growth inhibition member)
The growth inhibiting member in the production method of the present invention is a member that functions as a mask, and is provided to suppress the growth of the first Group 13 metal nitride crystal on the main surface on the front side of the seed crystal. The growth inhibiting member is partially formed so as to leave a line-shaped opening in which the main surface of the front side of the seed crystal is exposed. The material of the growth inhibition layer is not particularly limited as long as it does not dissolve or decompose during the reaction. For example, Si, Al, W, Mo, Ti, Pt, Ir, Ag, Au, Ta , Ru, Nb, Pd, alloys thereof, oxides or nitrides.

  The shape of the growth-inhibiting member is not limited as long as it is a shape that can provide a line-shaped opening serving as a starting point for the growth of the plate-like crystal on the main surface on the front side. It is preferably a shape having a straight portion serving as a side surface in the longitudinal direction, for example, more preferably a polygonal shape such as a triangular shape, a quadrangular shape or a hexagonal shape, and further preferably a stripe shape.

The width W ₁ of the growth inhibiting member is not particularly limited, but is preferably 1 mm or more, more preferably 2 mm or more, more preferably 20 mm or less, and even more preferably 10 mm or less. This is because by adjusting the interval at which the plate-like crystals are arranged when growing a second group 13 nitride crystal, which will be described later, to be equal to or greater than the lower limit, the number of joints is reduced over the entire main surface of the substrate. The second group 13 nitride crystal can be promoted to be easily bonded to each other, and the second group 13 nitride crystal can be promoted. This tends to shorten the time required for growth until they are bonded to each other, which is preferable.

The width W ₂ of the line-shaped opening is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more, further preferably 10 μm or more, particularly preferably 20 μm or more, It is preferably 5000 μm or less, more preferably 1000 μm or less, and even more preferably 500 μm or less. There exists a tendency which can promote the crystal growth from a line-shaped opening part by setting it as the said lower limit or more, and there exists a tendency which can make the influence of a seed crystal small by setting it as the said upper limit or less.

Further, the length L ₁ in the longitudinal direction of the line-shaped opening is not particularly limited, but is preferably 10 mm or more, more preferably 20 mm or more, and further preferably 25 mm or more. There exists a tendency for a large crystal | crystallization to be obtained by setting it as the said lower limit or more.
Further, the longitudinal direction of the line-shaped opening is not limited at all. However, when a seed crystal having a {0001} plane as a main surface is used, an M-plane or A-plane that tends to be a stable surface during crystal growth is used as the main surface. Since a plate-like crystal can be grown, it is preferable that the longitudinal direction of the line-shaped opening is the a-axis direction or the m-axis direction. With such a direction, the line-shaped opening forms a stripe pattern extending in the a-axis direction or the m-axis direction. The longitudinal direction extending in the a-axis direction or the m-axis direction preferably has an off angle of 10 ° or less, more preferably 6 ° or less. When it has an off angle, a more stable plate crystal can be grown.

  The number of line-shaped openings is not particularly limited and is usually 2 or more, preferably 3 or more, more preferably 4 or more, and usually 100 or less. This is because the second group 13 nitride crystal is adjusted by adjusting the interval in which the plate-like crystals are arranged when growing a second group 13 nitride crystal, which will be described later, to be equal to or more than the lower limit value. There is a tendency that crystal growth that is easy to bond to each other can be promoted, and by making the upper limit or less, there is a tendency that joints can be reduced over the entire main surface of the substrate.

  In addition, as long as a plurality of line-shaped openings are provided to form a stripe pattern, the number and arrangement thereof are not limited, but a plurality of line-shaped openings may be formed so as to be substantially parallel to each other. preferable. Moreover, since it has a line-shaped opening part in the main surface of the front side, and these should just form the stripe pattern, there may be an opening part of another shape which cross | intersects these lines. .

Specific examples in the case where the line-shaped openings form a stripe pattern are shown in FIGS. FIG. 4A shows an example in which a plurality of stripe-shaped growth inhibiting members 202 are provided in parallel so as to reach the end of the main surface of the seed crystal, and a plurality of line-shaped openings 203 are formed in parallel. . Since the plurality of line-shaped openings are formed so that the longitudinal direction thereof is parallel to the a-axis, in this example, when the first group 13 nitride crystal is grown, a plate shape having the M plane as the main surface A plurality of crystals can be grown. 4B and 4C, a plurality of rectangular growth inhibiting members 202 that do not reach the end of the seed crystal are provided in parallel to the a-axis direction, and the plurality of line-shaped openings 203 are parallel to each other. The openings are connected to each other at the end of the seed crystal.
When the first growth step is performed using these seed crystals, a plate-like crystal grows also from the openings at the end of the seed crystal, and grows from the line-like openings forming the stripe pattern. It becomes a part which connects the shaped crystals. Further, FIG. 4 (d) is provided with a plurality of rectangular growth inhibiting members 202 that do not reach the end of the seed crystal in parallel to the a-axis direction, and a plurality of line-shaped openings 203 are present in parallel, Furthermore, it is an example in which line-shaped openings are provided so as to intersect these lines perpendicularly. When the first growth step is performed using this seed crystal, a plate-like crystal grows also from the line-shaped opening provided so as to intersect perpendicularly, and from the line-shaped opening that forms the stripe pattern. It becomes a part which connects plate-like crystals to grow.

In addition, the growth inhibiting member may be formed not only on the main surface of the seed crystal but also on the side surface. However, if crystal growth is possible from the side surface of the seed crystal, the plate crystals grown from a plurality of line-shaped openings are formed. Can be grown so as to be connected at the side end surfaces thereof, it is preferable not to provide a growth inhibiting member on at least the side surface of the seed crystal adjacent to the line-shaped opening, that is, to expose the side surface. . By exposing the side surface of the seed crystal adjacent to the line-shaped opening, lateral growth from the side surface is promoted, and a crystal (frame-shaped crystal) grown laterally from the side surface is formed on the main surface. The plate crystal grown from the line-shaped opening can be united. The ratio of the length of the side surface of the seed crystal adjacent to the opening to the minimum width W ₂ of the line-shaped opening is preferably 100 or more, more preferably 200 or more, and preferably 400 or more. Further preferred. By setting it to the lower limit value or more, lateral growth from the side surface tends to be further promoted. In addition, the length of the side surface of the seed crystal adjacent to the opening means the maximum length in the direction parallel to the main surface among the lengths of the side surface. Further, the plane orientation of the side surface of the seed crystal adjacent to the opening is not particularly limited, but nonpolar planes such as M plane and A plane; semipolar planes such as (10-1-1) plane and (10-11) plane A surface etc. can be mentioned preferably.

  A growth inhibiting member may be provided on the outer edge of the main surface of the seed crystal, but a growth inhibiting member is provided in a region of 0.1 mm from the outer edge toward the center as shown in FIGS. 4B and 4C. In other words, it is preferable that an area of 0.1 mm from the outer edge toward the center is an exposed part, and an area of 5 mm from the outer edge toward the center is more preferably an exposed part. Thus, by making the vicinity of the outer edge an exposed part, the side end face of the plate crystal grown from the line-shaped opening is combined with the crystal (frame crystal) grown from the side surface of the seed crystal and the exposed part near the outer edge. In this state, crystal growth can proceed, and plate crystals can be grown so as to be connected to each other.

  Further, the ratio of the main surface of the seed crystal covered with the growth inhibiting member is not particularly limited, but it is preferably 90% or more, more preferably 95% or more, and usually 99. 99% or less. By setting it to the lower limit value or more, there is a tendency that warpage to the plate crystal grown from the seed crystal and propagation of crystal defects can be suppressed.

[First growth process]
The first growth step according to the method for manufacturing a Group 13 nitride substrate of the present invention is as follows: “From the plurality of line-shaped openings, the first Group 13 nitride is formed in a direction perpendicular to the main surface on the front side. This is a step of growing a physical crystal so that first group 13 nitride crystals grown from a plurality of line-shaped openings are connected to each other.

The shape of the crystal to be grown is not particularly limited, but a plate-like group 13 nitride crystal (plate-like crystal) is grown in a direction perpendicular to the main surface on the front side from a plurality of line-shaped openings. It is preferable. Specifically, the first group 13 nitride crystal is formed in a direction (−c axis direction) perpendicular to the −C plane that is the main surface on the front side from the line-shaped opening 203 in FIG. The plate crystal 204 is grown as shown in FIG. In this specification, a plate-like crystal is a crystal grown from a line-shaped opening, and has a maximum height H in a direction perpendicular to the main surface of the seed crystal 201 and a main surface of the seed crystal. The minimum width W _{3 in the} direction parallel to the crystal means a crystal having a shape satisfying the condition of H> W ₃ .

  Further, it is preferable to grow a group 13 nitride crystal (frame crystal) that intersects the line-shaped opening so as to connect the plurality of plate crystals. As described above, the frame-like crystal is formed by growing the first group 13 nitride crystal in the −c-axis direction in the −C plane region that is expanded by lateral growth from the side surface of the seed crystal. By using the seed crystal as shown in FIGS. 4B and 4C, the first group 13 nitride crystal grows in the −c-axis direction from the exposed portion near the outer edge of the seed crystal. The method of forming is mentioned. The first group 13 nitride crystal obtained by these methods has a shape as shown in FIG. In this case, the side end faces of the plate-like crystal 204 are joined by the frame-like crystal 205 grown from the side surface of the seed crystal and / or the exposed portion near the outer edge of the seed crystal. By forming the frame-like crystal 205 so that the side ends of the plate-like crystal 204 are connected to each other, it serves as a guide, and the side-end face of the plate-like crystal does not become a stable surface, It can suppress that a corresponding area becomes small. Even when the seed crystal is removed in the next removal step, the plurality of plate crystals 204 are kept integrated by the frame crystal 205 without changing the axial direction grown in the first growth step. Therefore, the crystal axes of the plate crystals 204 can be aligned in the same direction. For the purpose of holding the plate-like crystal 204 in an integrated state, a frame-like crystal that is connected across the central portion of the plate-like crystal using a seed crystal as shown in FIG. May be formed.

  A plate-like crystal obtained by using such a method tends to be a crystal in which the occurrence of crystal defects, warpage, and cracks is small and the occurrence of cracks during processing is suppressed. It is considered that the crystal growth of the plate-like crystal from the opening not covered with the growth inhibiting member can promote the lateral growth at the initial stage of growth and reduce the crystal defects. Further, it is considered that the growth crystal overcomes the seed crystal and the propagation of warpage is suppressed by performing the thick film growth to the extent that a plate-like crystal is obtained. Also, especially when using the liquid phase growth method, which is a harsh growth condition compared to the vapor phase growth method, the growth inhibiting member formed on the main surface of the seed crystal is grown on the main surface during the growth. It may be difficult to fix firmly and may be easily peeled off due to stress generated in the growth layer during the growth. In other words, by relaxing the stress generated during the growth by peeling the growth inhibiting member, the internal stress remaining in the growth layer can be reduced, and as a result, cracks caused by the stress are suppressed, It is considered that the occurrence of cracking is suppressed even when a load is applied by processing or the like.

The shape of the plate crystal to be grown is not particularly limited, but the width W ₂ of the line-shaped opening and the minimum width W _{3 in the} direction parallel to the main surface of the seed crystal in the plate crystal are W preferably satisfies the _3> W ₂ relationship. By satisfying the relationship, lateral growth can be promoted at the initial stage of growth, and crystal defects tend to be reduced. From such a viewpoint, the ratio of the minimum width W _{3 in} the direction parallel to the main surface of the seed crystal in the plate crystal to the width W ₂ of the line-shaped opening is preferably 5 or more. More preferably, it is more preferably 20 or more, and usually 1000 or less.

  As the crystal growth method, any growth method capable of growing a plate-like group 13 nitride crystal may be used. Specifically, known methods such as a liquid phase epitaxy method (LPE method), a flux method, an ammonothermal method, and the like. A liquid phase growth method is preferably used. Among these, the ammonothermal method can be preferably employed because the crystal growth rate in the −c-axis direction tends to be increased.

[Removal process]
The removing step according to the method for manufacturing the group 13 nitride substrate of the present invention is as follows: “From the main surface on the back side until the first group 13 nitride crystal grown in the first growth step is exposed, The first group 13 nitride crystal exposed by removing a part or the whole is processed to have a plurality of planes parallel to the main surface of the seed crystal ”.

  The method for removing the seed crystal from the main surface on the back side is not particularly limited, but if the seed crystal is removed by cutting by a known method such as a wire saw or grinding by a known method using a grindstone or the like. Good. In order to process the exposed first group 13 nitride crystal to have a plurality of planes parallel to the main surface of the seed crystal, the cutting and / or grinding may be performed in parallel to the main surface of the seed crystal. preferable.

  FIG. 6A shows the crystal of the shape shown in FIG. 5C obtained in the first growth step on the + C plane side of the crystal obtained by completely removing the seed crystal existing on the + c axis side. It is a top view. FIG. 6B is a cut perspective view cut along AA ′. Here, the crystal obtained after the removing step is referred to as “Group 13 nitride crystal frame”. In the group 13 nitride crystal frame of FIG. 6, the seed crystal is completely removed, and the + C plane of the first group 13 nitride crystal grown in the first growth step is exposed, and the plate-like crystal is A plurality of + C planes are arranged at regular intervals.

  In the second growth step of the next step, since the second group 13 nitride crystal is grown from the plate crystal (+ C plane) exposed in the removal step, the seed crystal is used until at least a part of the plate crystal is exposed. It is necessary to remove. The seed crystal can be removed in part or in whole, but it is easy to perform processing parallel to the main surface of the seed crystal and a flat surface can be easily obtained in the subsequent second growth step. It is preferable to remove. It is also preferable to remove the growth inhibiting member provided on the main surface on the front side of the seed crystal. Therefore, the group 13 nitride crystal frame preferably has a cavity penetrating between the plate crystals as shown in FIG. When the first group 13 nitride crystal is grown on the main surface on the back side of the seed crystal, it is removed together with the seed crystal.

[Second growth process]
The second growth step according to the method for manufacturing a group 13 nitride substrate of the present invention includes: “from the first group 13 nitride crystal exposed in the removing step, at least in a direction parallel to the main surface on the back side. The second group 13 nitride is grown and grown until a plurality of second group 13 nitride crystals grown from the first group 13 nitride crystal are joined together.

  The shape of the crystal to be grown is not particularly limited as long as it grows in a direction parallel to the main surface on the back side of the seed crystal, but is preferably a plate-like crystal formed by lateral growth. As shown in FIG. 3 (d-1), in the group 13 nitride crystal frame, crystal growth starts in the lateral direction from a plurality of plate crystals, and a plurality of second group 13 nitride crystals are formed. Is done. It is necessary to grow the crystal until at least these two or more second group 13 nitride crystals are bonded to each other. Preferably, as shown in FIG. 3D-2, a large number of second group 13 nitride crystals are joined to form a continuous flat plate covering the group 13 nitride crystal frame. Growing until the surface is a continuous flat surface. By performing such growth, it is possible to obtain a substrate having a large main surface in the next substrate manufacturing process.

  In the second growth step, unlike the first growth step in which the growth is performed in a direction perpendicular to the main surface of the seed crystal, the growth can be performed in a direction parallel to the main surface of the seed crystal. This is because it is used. Since the seed crystal used in the present invention has a polar surface as a main surface, the Group 13 nitride crystal frame obtained from the first crystal through the first growth step also has the same polarity as the seed crystal. When the growth surface is a polar surface, the growth rate is usually greatly different from the polarity to the front and back. Utilizing this, the surface with a high crystal growth rate is used as the main surface on the front side, and the growth rate of the plate crystal is advanced by utilizing the fact that the growth rate in the direction perpendicular to the seed crystal is high. By utilizing the slow surface as the main surface on the back side, lateral growth can be promoted by taking advantage of the growth rate in the direction parallel to the seed crystal. Therefore, when the second growth process is performed using the group 13 nitride crystal frame of FIG. 6B, lateral growth (ie, growth in the a-axis and m-axis directions) is performed on the + c-axis side where the growth rate is slow. ) To join the second group 13 nitride crystals together to form a flat surface with a continuous growth surface. Of the polar surfaces, the fast growth surface and the slow growth surface vary depending on the type of group 13 nitride to be selected, the growth method of the group 13 nitride crystal, and the like. Just choose.

  As the crystal growth method, any growth method capable of lateral growth of a group 13 nitride crystal may be used. Specifically, known methods such as a liquid phase epitaxy method (LPE method), a flux method, an ammonothermal method, and the like. A liquid phase growth method is preferably used. Of these, the ammonothermal method can be preferably employed because it tends to promote lateral growth in the + c-axis direction.

[Substrate manufacturing process]
The substrate manufacturing process according to the method for manufacturing a group 13 nitride substrate of the present invention includes: “cutting and / or grinding the second group 13 metal nitride crystal grown in the second growth process, To obtain a Group 13 metal nitride substrate.
The method for cutting and / or grinding the second group 13 metal nitride crystal is not particularly limited, and it is possible to use a known method such as a wire saw or a known method using a grindstone. A plate-like crystal may be manufactured. At least the group 13 nitride crystal frame used in the second growth step needs to be separated from the second group 13 metal nitride crystal into a plate shape. In this step, in addition to cutting and / or grinding, steps such as polishing, etching, and cleaning that are usually performed when a semiconductor substrate is manufactured may be included. Examples of the surface polishing step include an operation for polishing the surface using abrasive grains such as diamond abrasive grains, a CMP (chemical mechanical polishing), and an operation for etching the damaged layer by RIE after mechanical polishing.

The thickness of the plate-like group 13 metal nitride substrate is preferably 100 μm or more, and more preferably 200 μm or more. Further, the maximum diameter of the main surface of the plate-like group 13 metal nitride substrate is preferably 10 mm or more, more preferably 15 mm or more, further preferably 20 mm or more, and usually 150 mm or less. is there. Preferably the area of the main surface of the plate-like Group 13 metal nitride substrates are each 1 cm ² or more, more preferably 2 cm ² or more, more preferably 4 cm ² or more.

  Examples of the shape of the main surface of the plate-like group 13 metal nitride substrate include a quadrangle, a hexagon, a dodecagon, a circle, and an ellipse, but a circle, a rectangle, or a hexagon is preferable. In addition, even if it is any shape, an orientation flat can be produced in an appropriate location.

[Crystal growth by ammonothermal method]
Hereinafter, in the ammonothermal method preferably used for growing a group 13 nitride crystal in the first growth step and the second growth step of the production method of the present invention, the structure of a crystal growth apparatus for producing a GaN crystal and Although a specific example of the growth condition will be described, the present invention is not limited to the following mode. In the second growth step, the group 13 nitride crystal frame obtained in the removal step may be used as a seed crystal described below.

(Crystal growth by ammonothermal method)
The ammonothermal method is a method for producing a desired material by utilizing a raw material dissolution-precipitation reaction using a nitrogen-containing solvent in a supercritical state and / or a subcritical state. The mineralizer, solvent, and raw material that can be used in the crystal growth method of the present invention are specifically described below.

(Mineralizer)
In the present invention, it is preferable to use a mineralizer when the group 13 nitride crystal is grown by the ammonothermal method. Since the solubility of the crystal raw material in a solvent containing nitrogen such as ammonia is not high, a halogen or alkali metal mineralizer is used to improve the solubility, but the type is not particularly limited.

  Examples of mineralizers containing halogen elements include ammonium halide, hydrogen halide, ammonium hexahalosilicate, and hydrocarbyl ammonium fluoride, tetramethyl ammonium halide, tetraethyl ammonium halide, benzyl trimethyl ammonium halide, halogen Examples thereof include alkylammonium salts such as dipropylammonium halide and isopropylammonium halide, alkyl metal halides such as sodium alkyl fluoride, alkaline earth metal halides and metal halides. Of these, preferred are alkali halides, alkaline earth metal halides, metal halides, ammonium halides and hydrogen halides, and more preferred are alkali halides, ammonium halides and group 13 metal halides. And hydrogen halide, particularly preferably ammonium halide, gallium halide, and hydrogen halide.

In addition to a mineralizer containing a halogen element, a mineralizer that does not contain a halogen element can be used. For example, it can be used in combination with an alkali metal amide such as NaNH ₂ , KNH _2, or LiNH ₂ . When a halogen element-containing mineralizer such as ammonium halide and a mineralizer containing an alkali metal element or alkaline earth metal element are used in combination, it is preferable to increase the amount of the halogen element-containing mineralizer. Specifically, the mineralizer containing an alkali metal element or alkaline earth metal element is preferably 50 to 0.01 parts by mass with respect to 100 parts by mass of the halogen element-containing mineralizer. It is more preferable to set it as 1 mass part, and it is further more preferable to set it as 5-0.2 mass part. By adding a mineralizer containing an alkali metal element or alkaline earth metal element, the ratio of the m-axis crystal growth rate to the crystal growth rate in the c-axis direction (m-axis / c-axis) can be further increased. It is.

Further, in order to prevent impurities from being mixed into the Group 13 nitride crystal to be grown, it is preferable to use the mineralizer after purification and drying as necessary. The purity of the mineralizer is usually 95% or higher, preferably 99% or higher, more preferably 99.99% or higher.
It is desirable that the amount of water and oxygen contained in the mineralizer is as small as possible, and the content thereof is preferably 1000 wtppm or less, more preferably 10 wtppm or less, and even more preferably 1.0 wtppm or less. .
When crystal growth is performed, aluminum halide, phosphorus halide, silicon halide, germanium halide, zinc halide, arsenic halide, tin halide, antimony halide, bismuth halide, etc. are added to the reaction vessel. It may be present.

(solvent)
As the solvent used in the ammonothermal method, a solvent containing nitrogen (nitrogen-containing solvent) is used. Examples of the nitrogen-containing solvent include a solvent that does not impair the stability of the group 13 metal nitride semiconductor crystal to be grown. Examples of the solvent include ammonia, hydrazine, urea, amines (for example, primary amines such as methylamine, secondary amines such as dimethylamine, tertiary amines such as trimethylamine, and ethylenediamine. Diamine) and melamine. These solvents may be used alone or in combination.

  The amount of water and oxygen contained in the solvent is desirably as small as possible, and the content thereof is preferably 1000 wtppm or less, more preferably 10 wtppm or less, and further preferably 0.1 wtppm or less. When ammonia is used as a solvent, the purity is usually 99.9% or more, preferably 99.99% or more, more preferably 99.999% or more, and particularly preferably 99.9999% or more. .

(material)
In the growth step, a raw material containing an element constituting the Group 13 nitride crystal to be grown as a growth crystal on the seed crystal is used. For example, when a nitride crystal of a Group 13 metal is to be grown, a raw material containing a Group 13 metal is used. Preferred are polycrystalline raw materials for Group 13 nitride crystals and / or Group 13 metals of the periodic table, and more preferred are gallium nitride and / or metallic gallium. The polycrystalline raw material does not need to be a complete nitride, and may contain a metal component whose group 13 element in the periodic table is in a metal state (zero valence) depending on conditions. For example, when the Group 13 metal nitride crystal to be grown is gallium nitride, a mixture of gallium nitride and metal gallium can be used.

  The method for producing the polycrystalline raw material is not particularly limited. For example, a nitride polycrystal produced by reacting a metal or an oxide or hydroxide thereof with ammonia in a reaction vessel in which ammonia gas is circulated can be used. In addition, as a metal compound material having higher reactivity, a compound having a covalent MN bond such as a halide, an amide compound, and an imide compound can be used. Furthermore, a nitride polycrystal produced by reacting a metal such as Ga with nitrogen at a high temperature and a high pressure can also be used.

(manufacturing device)
A specific example of a crystal manufacturing apparatus that can be used for manufacturing the Group 13 nitride crystal of the present invention is shown in FIGS. The crystal production apparatus used in the present invention includes a reaction vessel.
FIG. 1 is a schematic view of a crystal manufacturing apparatus that can be used in the present invention. In the crystal manufacturing apparatus shown in FIG. 1, the inside of an autoclave (pressure-resistant container) 1 is lined, and crystal growth is performed using the inside of the lining 3 as a reaction container. The autoclave 1 is composed of a raw material dissolution region 9 for melting the raw material and a crystal growth region 6 for growing crystals. The other members can be installed in the same manner as the crystal manufacturing apparatus in FIG.

  FIG. 2 is a schematic view of another crystal manufacturing apparatus that can be used in the present invention. In the crystal manufacturing apparatus shown in FIG. 2, crystal growth is performed in a capsule (inner cylinder) 20 loaded as a reaction vessel in the autoclave 1 (pressure-resistant vessel). The capsule 20 includes a raw material filling region 9 for dissolving the raw material and a crystal growth region 6 for growing crystals. In the raw material filling area 9, a solvent and a mineralizer can be put together with the raw material 8. A seed crystal 7 can be installed in the crystal growth region 6 by suspending it with a wire 4. Between the raw material filling region 9 and the crystal growth region 6, a partition baffle plate 5 is installed in two regions.

(Crystal growth)
An example of the crystal growth method according to the method for producing a Group 13 nitride crystal of the present invention will be described. When carrying out crystal growth according to the method for producing a Group 13 nitride crystal of the present invention, first, a seed crystal, a nitrogen-containing solvent, a raw material, and a mineralizer are put in a reaction vessel and sealed. To do. Here, as the seed crystal, a crystal whose at least a part of its main surface is coated with a growth inhibiting member is used. When the plate-like crystal is once grown and then grown again, the growth inhibiting member may remain on the main surface of the seed crystal or may be peeled off.

The inside of the reaction vessel may be degassed before or after introducing a material such as a raw material. Moreover, you may distribute | circulate inert gas, such as nitrogen gas, at the time of introduction | transduction of materials, such as a raw material. Usually, the seed crystal is placed in the reaction vessel at the same time or after filling the raw material and the mineralizer. After installation of the seed crystal, heat deaeration may be performed as necessary. The degree of vacuum at the time of deaeration is preferably 1 × 10 ⁻² Pa or less, more preferably 5 × 10 ⁻³ Pa or less, and particularly preferably 1 × 10 ⁻³ Pa or less.

When the production apparatus shown in FIG. 2 is used, the capsule 20 is sealed in the capsule 20 which is a reaction vessel by putting the seed crystal 7, a nitrogen-containing solvent, a raw material, and a mineralizer, and then sealing the capsule 20 with an autoclave (pressure resistance). Container) 1, and preferably, the space between the pressure-resistant container and the reaction container is filled with the second solvent to seal the pressure-resistant container.
Thereafter, the whole is heated to bring the inside of the reaction vessel into a supercritical state and / or a subcritical state. In the supercritical state, the viscosity of the substance is generally lower and it diffuses more easily than the liquid, but has the same solvating power as the liquid. The subcritical state means a liquid state having a density substantially equal to the critical density near the critical temperature. For example, in the raw material filling region, the raw material is melted as a supercritical state, and in the crystal growth region, the temperature is changed so that it becomes a subcritical state, and crystal growth using the difference in solubility between the supercritical state material and the subcritical state material is also performed. Is possible.

  In the supercritical state, the reaction mixture is generally maintained at a temperature above the critical point of the solvent. When ammonia is used as a solvent, the critical point is a critical temperature of 132 ° C. and a critical pressure of 11.35 MPa, but if the filling rate with respect to the volume of the reaction vessel is high, the pressure far exceeds the critical pressure even at a temperature below the critical temperature. . In the present invention, the “supercritical state” includes such a state exceeding the critical pressure. Since the reaction mixture is enclosed in a constant volume reaction vessel, the increase in temperature increases the pressure of the fluid. In general, if T> Tc (critical temperature of one solvent) and P> Pc (critical pressure of one solvent), the fluid is in a supercritical state.

Under supercritical conditions, a sufficient growth rate of the group 13 nitride crystal can be obtained. In the present invention, the growth rate of the group 13 nitride crystal is preferably equal to or higher than a certain rate. The growth rate in the direction perpendicular to the main surface of the seed crystal is preferably 50 μm / day or more, more preferably 100 μm / day or more, and further preferably 200 μm / day or more.
The reaction time depends in particular on the reactivity of the mineralizer and the thermodynamic parameters, ie temperature and pressure values. For this reason, it is preferable to increase the growth rate of the Group 13 nitride crystal by controlling these conditions. By setting the growth rate of the group 13 nitride crystal to a certain rate or more, a plate crystal having a larger principal surface tends to be obtained.

  During the growth of the Group 13 nitride crystal, the pressure in the reaction vessel is preferably 30 MPa or more, more preferably 60 MPa or more, and further preferably 100 MPa or more from the viewpoint of crystallinity and productivity. . The pressure in the reaction vessel is preferably 700 MPa or less, more preferably 500 MPa or less, further preferably 350 MPa or less, and particularly preferably 300 MPa or less from the viewpoint of safety. The pressure is appropriately determined depending on the filling rate of the solvent volume with respect to the temperature and the volume of the reaction vessel. Originally, the pressure in the reaction vessel is uniquely determined by the temperature and the filling rate, but in practice, the raw materials, additives such as mineralizers, temperature heterogeneity in the reaction vessel, and free volume Depending on the presence of

  From the viewpoint of crystallinity and productivity, the lower limit of the temperature range in the reaction vessel is preferably 320 ° C or higher, more preferably 370 ° C or higher, and further preferably 450 ° C or higher. From the viewpoint of safety, the upper limit value is preferably 700 ° C. or less, more preferably 650 ° C. or less, and further preferably 630 ° C. or less. In the production of the Group 13 nitride crystal of the present invention, the temperature of the raw material filling region in the reaction vessel is preferably higher than the temperature of the crystal growth region. The temperature difference (| ΔT |) is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, preferably 100 ° C. or lower, and 90 ° C. or lower from the viewpoints of crystallinity and productivity. More preferably, 80 ° C. or lower is particularly preferable. The optimum temperature and pressure in the reaction vessel can be appropriately determined depending on the type and amount of mineralizer and additive used during crystal growth.

  In order to achieve the temperature range and pressure range in the reaction vessel, the injection rate of the solvent into the reaction vessel, that is, the filling rate, is the free volume of the reaction vessel, that is, when crystal raw materials and seed crystals are used in the reaction vessel. Subtract the volume of the seed crystal and the structure on which the seed crystal is installed from the volume of the reaction vessel, and if a baffle plate is installed, subtract the volume of the baffle plate from the volume of the reaction vessel to remain. Based on the liquid density at the boiling point of the solvent of volume, it is usually 20 to 95%, preferably 30 to 80%, more preferably 40 to 70%. When the capsule 20 as shown in FIG. 2 is used as the reaction vessel, it is preferable to appropriately adjust the amount of the solvent so that the pressure is balanced inside and outside the capsule 20 in the supercritical state of the solvent.

  The growth of the Group 13 nitride crystal in the reaction vessel is carried out by heating and raising the temperature of the reaction vessel using an electric furnace having a thermocouple, so that the solvent such as ammonia in the reaction vessel is subcritical or supercritical. This is done by maintaining the state. The heating method and the rate of temperature increase to a predetermined reaction temperature are not particularly limited, but are usually performed over several hours to several days. If necessary, the temperature can be raised in multiple stages, or the temperature raising speed can be changed in the temperature range. It can also be heated while being partially cooled.

  The above-mentioned “reaction temperature” is measured by a thermocouple provided so as to be in contact with the outer surface of the reaction vessel and / or a thermocouple inserted into a hole having a certain depth from the outer surface, and It can be estimated in terms of internal temperature. The average value of the temperatures measured with these thermocouples is taken as the average temperature. Usually, an average value of the temperature of the raw material filling region and the temperature of the crystal growth region is defined as the average temperature.

The reaction time after reaching a predetermined temperature varies depending on the type of Group 13 nitride crystal, the raw material used, the type of mineralizer, and the size and amount of the crystal to be produced, but usually several hours to several hundreds. Can be a day.
During the reaction, the reaction temperature may be constant, or the temperature may be gradually raised or lowered. After a reaction time for forming the desired crystal, the reaction temperature is lowered. The temperature lowering method is not particularly limited, but the heating may be stopped while the heating of the heater is stopped and the reaction vessel is installed in the furnace as it is, or the reaction vessel may be removed from the electric furnace and air cooled. If necessary, quenching with a refrigerant is also preferably used.

  After the temperature of the outer surface of the reaction vessel or the estimated temperature inside the reaction vessel is below a predetermined temperature, the reaction vessel is opened. The predetermined temperature at this time is not particularly limited, and is usually −80 ° C. to 200 ° C., preferably −33 ° C. to 100 ° C. Here, the valve may be opened by pipe connection to a valve connection port of the valve attached to the reaction vessel, passing through a vessel filled with water or the like. Further, if necessary, the ammonia solvent in the reaction vessel is sufficiently removed by making a vacuum or the like, and then dried, and the periodic table group 13 metal nitride semiconductor crystal formed by opening the lid of the reaction vessel and the like Additives such as unreacted raw materials and mineralizers can be taken out.

  In addition, after carrying out the above-mentioned crystal growth, the solvent containing the nitrogen, the raw material, and the mineralizer are again put in the reaction vessel, sealed, and repeated several times in the direction perpendicular to the main surface of the seed crystal. Crystals may be grown. In this case, a crystal body in which the seed crystal and the plate crystal are integrated may be used as the seed crystal.

<Group 13 metal nitride substrate>
By the manufacturing method of the present invention described above, a large-diameter and high-quality group 13 nitride substrate can be obtained. The crystal plane of the main surface of the group 13 nitride substrate is not particularly limited, but is preferably a C-plane from the viewpoint that a large-diameter main surface can be secured.
Moreover, although the physical property of the group 13 nitride substrate manufactured by the manufacturing method of the present invention is not particularly limited, preferable physical properties will be described below.

(Carrier concentration)
In the case of a GaN crystal, the carrier concentration of the group 13 nitride substrate is usually 1.0 × 10 ¹⁷ cm ⁻³ or more, preferably 2.0 × 10 ¹⁷ cm ⁻³ or more, and usually 1 × 10 ¹⁹ cm ^{−. 3} or less, preferably 8.0 × 10 ¹⁸ cm ⁻³ or less.

(Half width of X-ray diffraction peak rocking curve (XRC))
The full width at half maximum of the rocking curve of the (002) diffraction peak and (102) diffraction peak of the X-ray diffraction of the group 13 nitride substrate is usually 50 arcsec or less, preferably 40 arcsec or less, more preferably 30 arcsec or less, and even more preferably 25 arcsec or less. Most preferably, it is 20 arcsec or less.

  Further, when XRC is measured at a plurality of points in the main surface of the group 13 nitride substrate, it is preferable that variations in the XRC half width are small. For example, when 30 or more points are measured at equal intervals, the average value of the XRC half-width is preferably 30 arcsec or less, more preferably 28 arcsec or less, and the standard deviation is preferably 15 or less. The following is more preferable. Further, when 30 points or more are measured at equal intervals, the ratio of the points having an XRC half width of 50 arcsec or more in all measurement points is preferably 20% or less, more preferably 10% or less, and more preferably 5%. More preferably, it is as follows.

(curvature radius)
The curvature radius of the group 13 nitride substrate is usually 5 m or more, preferably 10 m or more, more preferably 20 m or more, and further preferably 50 m or more.

<Device>
The group 13 nitride substrate obtained by the production method of the present invention is suitably used for devices such as light emitting elements, electronic devices, and power devices. Examples of the light-emitting element in which the Group 13 nitride crystal or the substrate of the present invention is used include a light-emitting diode, a laser diode, and a light-emitting element obtained by combining these with a phosphor. Moreover, examples of the electronic device in which the group 13 nitride substrate of the present invention is used include a high frequency element, a high withstand voltage high output element, and the like. Examples of high-frequency elements include transistors (HEMT, HBT), and examples of high-voltage high-power elements include thyristors (SCR, GTO), insulated gate bipolar transistors (IGBT), and Schottky barrier diodes (SBD). .

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but can be appropriately changed without departing from the gist of the present invention. Accordingly, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Example 1>
In this example, a nitride crystal was grown using a reactor as shown in FIG.
(1) Crystal growth was performed using the nickel-based alloy autoclave 1 as a pressure resistant container and the Pt—Ir capsule 20 as a reaction container.
Polycrystalline GaN particles were placed as the raw material 8 in the capsule lower region (raw material dissolution region 9), and high-purity NH ₄ F was charged into the capsule as a mineralizer. Further, a platinum baffle plate 5 was installed between the lower raw material melting region 9 and the upper crystal growth region 6. As the seed crystal 7, a C-plane substrate obtained by the HVPE method was suspended using a platinum wire and a seed support frame, and placed in the crystal growth region 6 above the capsule. The main surface (−C surface) on the front side of the seed crystal 7 is 46 mm □, and the elongated linear opening of 50 μm width (W ₁ ) whose longitudinal direction is parallel to the a-axis direction (parallel to the M-plane). Is covered with a Pt mask having a width of 4 mm, and a stripe pattern is formed on the entire main surface on the front side as shown in FIG. From the portion 203, the CMP-finished region of the main surface (−C surface) on the front side was partially exposed. Next, in the procedure shown below, a plate-like crystal was grown from the line-shaped opening to the −c axis direction so that the M-plane spread as shown in FIG.

(2) After a Pt cap was connected to the upper part of the capsule 20 by welding, the lower part of the capsule was cooled with liquid nitrogen, and the valve was opened and filled with HI without touching the outside air. Next, the capsule was connected to the NH ₃ gas line, and after filling with NH ₃ without touching the outside air, the valve was closed again. Thereafter, the tube at the top of the cap was sealed. The F concentration introduced into the capsule was 1.0 mol% with respect to NH ₃ and the I concentration was 1.5 mol%.

(3) The capsule was inserted into the autoclave and the autoclave was sealed.
(4) The valve was opened and vacuum degassed. While maintaining the vacuum state, the autoclave 1 was cooled with dry ice methanol solvent and charged with NH ₃ without touching the outside air, and then the valve 10 was closed again. .
(5) The autoclave 1 was stored in an electric furnace composed of a plurality of heaters. The temperature was raised while controlling the autoclave outer surface temperature so that the average temperature inside the autoclave was 618 ° C. and the internal temperature difference (ΔT) was 14 ° C. After reaching the set temperature, the temperature was maintained for 21 days. The pressure in the autoclave was 218 MPa.

(6) While cooling the autoclave 1, the valve 10 attached to the autoclave was opened, and NH ₃ in the autoclave was removed.
(7) The autoclave lid was opened and the capsule 20 was taken out. A gallium nitride crystal (first GaN crystal) is grown on the seed crystal, the growth thickness in the −c axis direction (N dimension) is 4 mm, and the growth rate in the N direction (−c axis direction) is 190 μm. The growth rate was as high as / day.

  Further, the crystal growth is not only in the −c-axis direction but also in the a-axis direction parallel to the main surface of the seed crystal, so that the −C plane region is expanded. The growth in the -c-axis direction also proceeds on the enlarged -C plane region, and the plate-like crystal portion grown from the line-shaped opening is enlarged by the lateral growth existing at both ends of the seed crystal. They were integrated with the crystals grown in the −c-axis direction (frame crystals) and connected to each other as shown in FIG.

  (8) The seed crystal was completely removed by grinding from the main surface (+ C surface) on the back side to obtain a GaN crystal frame in which the + C surface of the first GaN crystal obtained in (7) was exposed. The main surface on the back side is as shown in FIG. 6A when viewed from above, and the + C plane is exposed in each of the plate-like crystal portion and the frame-like crystal portion.

(9) Using the GaN crystal frame obtained in the above (8) as the seed crystal 7, the F concentration is 0.5 mol% with respect to NH ₃ and the I concentration is 1 by the same method as (1) to (6). Gallium nitride (second GaN crystal) was grown on the GaN crystal frame serving as the seed crystal 7 at 0.5 mol%, a pressure of 216 MPa, an average temperature of 611 ° C., a temperature difference (ΔT) of 18 ° C., and a holding time of 21 days. Made growth. On the −C plane side of the GaN crystal frame, the second GaN crystal grows so that the plate crystal extends in the −c axis direction, and on the + C plane side, the growth from the plate crystal to the lateral direction proceeds. Two GaN crystals were joined together, and a second GaN crystal on a flat plate having an integrated + C plane was formed.

(10) The GaN crystal frame used as the seed crystal 7 is cut and removed to separate the plate-like second GaN crystal formed on the + C plane side, and the length in the a-axis direction is 50 mm, m A GaN substrate having an axial length of 20 mm and a thickness of 300 μm is obtained.
When the curvature radius of the C-plane of the obtained GaN substrate was measured, the a-axis direction was 555 m and the m-axis direction was 18 m, indicating that a very flat crystal without warping was obtained. It was. The obtained results are summarized in Table 1.
Moreover, when the rocking curve (XRC) measurement of the X-ray diffraction peak was performed and the half width was obtained, it was 22.0 arcsec for the (002) diffraction peak and 20.3 arcsec for the (102) diffraction peak. Further, FIG. 7 shows the result of measuring the rocking curve of the (002) diffraction peak of the X-ray diffraction continuously on the C-plane of the obtained GaN substrate at a pitch of 200 μm in the m-axis direction. The horizontal axis represents the measurement point where the center point in the substrate is 0 mm, and the vertical axis represents the XRC half-value width. It was less than 30 arcsec over almost the entire C plane, and it was confirmed that the crystallinity was excellent uniformly in the plane.

[X-ray rocking curve (XRC) half width]
X-ray rocking curve (XRC) was measured with a high resolution X-ray diffractometer manufactured by PANalytical. Rocking curve measurement was performed for GaN (002) reflection and GaN (102) reflection, and crystal orientation distribution in the tilt and twist directions of the crystal was evaluated. Here, (002) and (102) represent X-ray diffraction planes.

[curvature radius]
The radius of curvature was measured using a high-resolution X-ray diffractometer manufactured by PANalytical having a high-precision cradle having a single-axis stage (x-axis) or a two-axis stage (xy). The sample is moved in the uniaxial direction (x direction) at intervals of 0.5 to 5 mm, the ω value giving the maximum intensity is calculated from the X-ray rocking curve measured at each point, the ω value against the moving distance x is plotted, and the minimum The slope k of the graph was calculated by the square method. The curvature radius R [m] was calculated from the slope k by the following equation.

      R = 1 / k × 180 × π / 1000

<Comparative Example 1>
The seed crystal 7 has a 50 μm width (W ₁ ) whose longitudinal direction is parallel to the a-axis direction (parallel to the M plane) on the main surface (+ C plane) on the front side of the C-plane substrate obtained by the HVPE method. 4e is covered with a Pt mask having a width of 200 μm so that the elongated line-shaped openings are arranged at intervals (pitch) of 200 μm, and a stripe pattern is formed on the entire main surface on the front side as shown in FIG. Formed. Other than this, the F concentration was 0.5 mol% relative to NH ₃ , the I concentration was 1.5 mol%, the pressure was 215 MPa, the average temperature was 618 ° C., and the temperature was the same as in Example 1 (2) to (6). A gallium nitride (GaN) crystal was grown on the seed crystal 7 with a difference (ΔT) of 14 ° C. and a holding time of 22 days. The GaN crystals grown from the line-shaped openings are immediately joined to each other immediately above the mask, and the obtained GaN crystals have a thickness of 0 on the main surface (+ C plane) on the front side of the seed crystal 7. It grew to form a flat film of 6 mm. When the obtained GaN crystal was visually confirmed, it was confirmed that a plurality of fine cracks were generated in the C plane.

The obtained GaN crystal was measured for the C-plane curvature radius. As a result, the a-axis direction was 2.5 to 50 m, the surface was uneven, and the m-axis direction was 17 m. The obtained results are summarized in Table 1.
Further, FIG. 8 shows the result of continuously measuring the rocking curve of the (002) diffraction peak of X-ray diffraction on the C-plane of the obtained GaN substrate at a pitch of 200 μm in the m-axis direction. The XRC half-value width varied widely in the range of 20 to 120 arcsec.

<Comparative Example 2>
The seed crystal 7 was used without forming a pattern with a mask on a C-plane substrate obtained by the HVPE method. Other than this, the F concentration was 0.5 mol% with respect to NH ₃ , the I concentration was 4.0 mol%, the pressure was 220 MPa, the average temperature was 616 ° C., and the temperature was the same as in Example 1 (2) to (6). A gallium nitride (GaN) crystal was grown on the seed crystal 7 with a difference (ΔT) of 24 ° C. and a holding time of 27 days. The obtained GaN crystal was grown so that a flat film having a thickness of 0.5 mm was formed on the + C plane side of the seed crystal 7 and a flat film having a thickness of 4 mm was formed on the −C plane side.

About the obtained GaN crystal, when the curvature radius of C surface was measured, the a-axis direction was 1.1 m and the m-axis direction was 1.1 m. The obtained results are summarized in Table 1.
Further, FIG. 9 shows the result of measuring the rocking curve of the (002) diffraction peak of X-ray diffraction continuously at a pitch of 200 μm in the m-axis direction on the C-plane of the obtained GaN substrate. The XRC half-value width varied widely in the range of 20 to 200 arcsec.

Comparing the grown crystals of Example 1 and Comparative Examples 1 and 2, in Example 1, a GaN substrate composed of a second GaN crystal integrated laterally from a first GaN crystal that is a plate-like crystal is obtained. It was confirmed that the crystallinity was extremely good. On the other hand, in Comparative Examples 1 and 2, a GaN crystal having a C-plane as a main surface grown on a seed crystal obtained by the HVPE method was obtained, but it was confirmed that the crystallinity was clearly poor.
In addition, Table 2 summarizes the XRC half-value width distribution of each grown crystal shown in FIGS.

  Comparing the grown crystals of Example 1 and Comparative Examples 1 and 2, it was confirmed that in Example 1, the XRC half-value width was clearly small and the variation was small. Therefore, it can be seen that good crystallinity is uniformly exhibited in the main surface. On the other hand, in Comparative Examples 1 and 2, it was confirmed that the XRC half width was large and the variation was large.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the group 13 nitride board | substrate which can suppress generation | occurrence | production of the crack at the time of a process can be provided with few generation | occurrence | production of a crystal defect, curvature, and a crack. The group 13 nitride substrate obtained by such a manufacturing method is suitably used as a substrate for a light emitting device or a power device, and has high industrial applicability.

1 Autoclave (pressure-resistant container)
2 Autoclave inner surface 3 Lining 4 Wire 5 Baffle plate 6 Crystal growth area 7 Seed crystal 8 Raw material 9 Raw material filling area 10 Valve 11 Vacuum pump 12 Ammonia cylinder 13 Nitrogen cylinder 14 Mass flow meter 20 Capsule (inner cylinder)
101 seed crystal 102 growth inhibiting member (mask)
103 line-shaped opening 104 first GaN crystal 105 GaN crystal frame 106 second GaN crystal 107 GaN substrate 201 seed crystal 202 growth inhibiting member (mask)
203 Line-shaped opening 204 Plate-like crystal 205 Frame-like crystal

Claims (4)

A GaN substrate that can draw at least one line segment that is a virtual line segment with a length of 20 mm parallel to the m-axis and that satisfies the following condition (A) on the C plane:
(A) When the rocking curve measurement of the (002) diffraction peak is performed at 41 measurement points that are separated at equal intervals on the line segment, the average value of the half-value width of the rocking curve is 30 arcsec or less. A GaN substrate that can draw at least one line segment that is a virtual line segment with a length of 20 mm parallel to the m-axis and that satisfies the following condition (A) on the C plane:
(A) When the rocking curve of the (002) diffraction peak is measured at 41 measurement points that are spaced apart at equal intervals on the line segment, the average value of the half-value widths of the rocking curve is 28 arcsec or less. An imaginary line segment having a length of 20 mm parallel to the m-axis, wherein at least one line segment satisfying the following condition (B) in addition to the condition (A) can be drawn on the C plane: Item 1 or 2 GaN substrate:
(B) When the rocking curve measurement of the (002) diffraction peak was performed at 41 measurement points spaced at equal intervals on the line segment, the ratio of the measurement points having a half-width of the rocking curve of 50 arcsec or more was 5%. It is as follows. The GaN substrate according to any one of claims 1 to 3 , which does not substantially contain Li, Na, and K.