JP6024335B2 - Periodic table group 13 metal nitride semiconductor substrate manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a Group 13 metal nitride semiconductor crystal of the periodic table. Specifically, the method includes a step of growing a periodic table group 13 metal nitride crystal layer by an ammonothermal method on at least an M plane and a semipolar plane as a growth plane on a base substrate having an M plane as a principal plane. Furthermore, the present invention relates to a method for producing a periodic table group 13 metal nitride semiconductor crystal including a step of obtaining a plate-like crystal having a M-plane having a larger area than the main surface of the base substrate.

Conventionally, periodic table group 13 metal nitrides such as gallium nitride (GaN) -based compounds have been used as semiconductor materials for periodic table group 13 metal nitride semiconductor substrates, and periodic table group 13 metal nitride semiconductors. Substrates are used in various devices such as light emitting devices. In recent years, the periodic table group 13 metal nitride semiconductor substrate has been used for power semiconductor elements (power devices) in addition to light-emitting device applications. Therefore, development of a periodic table group 13 metal nitride semiconductor substrate capable of withstanding high pressure and large current is in progress.
A single crystal of nitride such as gallium nitride or aluminum nitride can be obtained by growing the crystal using an ammonothermal method or the like. The ammonothermal method is a method for producing a desired material by using a dissolution-precipitation reaction of raw materials using a solvent containing nitrogen such as ammonia in a supercritical state and / or a subcritical state. When applied to crystal growth, this is a method in which crystals are precipitated by generating a supersaturated state due to a temperature difference utilizing the temperature dependence of the solubility of a raw material in a solvent such as ammonia.

  Conventionally, a periodic table group 13 metal nitride semiconductor substrate having a C-plane which is a polar plane as a main surface has been often used. However, in this case, due to the inherent characteristics of the Group 13 nitride crystal such as GaN, there is a problem that the influence of the piezo electric field is increased and the efficiency of the light emitting element is lowered. In addition, crystal defects such as threading dislocations may occur in a semiconductor substrate having a C-plane as a main surface, and the dislocation density may increase.

In order to solve these problems, it has been studied to produce a light emitting device using a substrate having a nonpolar plane other than the C plane or a semipolar plane as a main plane. Therefore, it is required to manufacture a substrate having a large nonpolar surface or semipolar surface as a main surface from which a device can be manufactured. For example, Patent Documents 1 to 3 disclose that crystal growth is performed using a seed crystal having an M plane as a growth main surface.
In Patent Document 1, the side surfaces of the obtained grown crystal are the A plane and the C plane, and the main surface of the grown crystal is composed only of the M plane obtained by lateral growth. Similarly, Patent Documents 2 and 3 only describe that crystal growth is performed with the main surface as the M-plane. In Patent Document 3, an alkali mineralizer is preferably used as a mineralizer used during crystal growth.

International Publication 2010/005914 Pamphlet Special table 2011-521878 gazette Special table 2009-541997

  When efficiently obtaining a Group 13 metal nitride semiconductor substrate (hereinafter also referred to as a Group 13 nitride semiconductor substrate) having an M plane as a main surface, a Group 13 nitride having the M surface as a main growth surface It is necessary to grow crystals. However, the rate of crystal growth in the m-axis direction with the M plane as the growth plane is slow, and it is difficult to increase the size of the semiconductor substrate with the M plane as the main plane. Furthermore, the semiconductor substrate having the M plane as the main surface has a problem that the manufacturing cost per unit area becomes very high because the size is small and the crystal growth rate is slow.

  Further, in the conventional method of growing a group 13 nitride crystal having the M plane as the growth main surface, a nitride semiconductor bar is cut out from a primary wafer formed by performing thick film growth using the C plane as a growth plane. A nitride semiconductor has been regrown on a substrate arranged so that the surface becomes the upper surface. That is, there has been a problem that crystals having an M-plane as a main surface cannot be grown on the substrate under the same conditions as the substrate manufacturing conditions. For this reason, there has been a problem that a Group 13 nitride crystal having the M-plane as the main surface cannot be obtained efficiently.

  Therefore, in order to solve the problems of the prior art, the inventors of the present application are Group 13 nitride crystals having an M plane as a main surface, and the main surface has a large area and is made of a high quality crystal. Further, studies have been made for the purpose of providing a method for producing a Group 13 nitride crystal with reduced production costs.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present application are composed of a periodic table group 13 metal nitride semiconductor, and on the base substrate having the M plane as a main surface, at least the M plane and By growing the periodic table group 13 metal nitride crystal layer by the ammonothermal method using the semipolar plane as the growth plane, it is a plate-like substrate having the M plane as the principal plane, which is larger than the area of the base substrate. It has been found that a plate-like substrate can be obtained.
Specifically, the present invention has the following configuration.

[1] Periodic Table A group 13 metal nitride semiconductor is formed on an underlying substrate having an M plane as a main surface, and at least an M plane and a semipolar plane as growth planes by an ammonothermal method. A first growth step for growing a group 13 metal nitride crystal layer; and after the first growth step, an area larger than the main surface of the base substrate from the first periodic table group 13 metal nitride crystal layer. A method for producing a Group 13 metal nitride semiconductor crystal of the periodic table, comprising a step of producing a plate crystal having a M-plane as a main surface.
[2] After the plate crystal manufacturing step, a second periodic table group 13 metal nitride crystal layer is formed on the plate crystal by an ammonothermal method using at least the M plane and the semipolar plane as growth planes. The method for producing a periodic table group 13 metal nitride semiconductor crystal according to [1], further including a second growth step of growing.
[3] When the area of the main surface of the base substrate is P and the area of the main surface of the plate crystal is Q, Q / P is 1.05 to 10 in [1] or [2] The manufacturing method of the periodic table group 13 metal nitride semiconductor crystal of description.
[4] The plate crystal includes an M-plane growth region made of a periodic table group 13 metal nitride crystal grown in the m-axis direction, and a direction inclined at an angle of 10 ° to 80 ° from the m-axis to the c-axis direction. The ratio of the M-plane area of the M-plane growth region to the total area of the main surface of the plate-like crystal is 50%. % In the periodic table group 13 metal nitride semiconductor crystal according to any one of [1] to [3].
[5] The periodic table group 13 metal nitride according to [4], wherein the M-plane area of the M-plane growth region is larger than the M-plane area of the main surface of the base substrate on the main surface of the plate crystal. Of manufacturing a semiconductor crystal.
[6] The period according to any one of [1] to [5], wherein the first growth step includes a step of reacting a mineralizer containing at least one element selected from fluorine, chlorine, bromine and iodine. TABLE 13 Group 13 metal nitride semiconductor crystal manufacturing method.
[7] The period according to any one of [2] to [6], wherein the second growth step includes a step of reacting a mineralizer containing at least one element selected from fluorine, chlorine, bromine and iodine. TABLE 13 Group 13 metal nitride semiconductor crystal manufacturing method.
[8] The method for producing a periodic table group 13 metal nitride semiconductor crystal according to [6] or [7], wherein the mineralizer is a mineralizer containing fluorine and iodine.
[9] When the concentration of fluorine contained in the mineralizer is F and the concentration of iodine contained in the mineralizer is I, the I / F is 0.5 to 10. The manufacturing method of the periodic table group 13 metal nitride semiconductor crystal of description.
[10] The plate-like crystal manufacturing step includes a step of slicing the first periodic table group 13 metal nitride crystal layer. [10] The periodic table group 13 metal according to any one of [1] to [9] A method for producing a nitride semiconductor crystal.
[11] The slicing step is a step of slicing at any depth position within a range of 45% or less with respect to the thickness of the first periodic table group 13 metal nitride crystal layer [ 10]. The manufacturing method of the periodic table group 13 metal nitride semiconductor crystal of [10].
[12] A periodic table group 13 metal nitride semiconductor crystal produced by the production method according to any one of [1] to [11].

ADVANTAGE OF THE INVENTION According to this invention, it is a group 13 nitride crystal which made M surface the main surface, Comprising: The group 13 nitride crystal with a large area of a main surface can be manufactured efficiently. Furthermore, according to the present invention, it is possible to efficiently manufacture a plate-like substrate made of a Group 13 nitride crystal having an M-plane area larger than that of the base substrate. In addition, a high quality region composed of high quality crystals can be secured in a wide proportion in the crystal main surface.
Further, according to the present invention, the production efficiency of the group 13 nitride crystal having the M plane as the main surface can be increased, and the production cost can be suppressed.

FIG. 1 is a schematic diagram showing a unit cell having a crystal structure of a group 13 nitride semiconductor. FIG. 2 is a schematic view showing one embodiment of a base substrate (seed crystal) used for crystal growth. FIG. 3 is a schematic view of an example of a group 13 nitride semiconductor crystal lump used in the present invention having an M plane as a main surface. FIG. 4 is a schematic cross-sectional view of a group 13 nitride semiconductor crystal mass used in the present invention. FIG. 5 is a schematic cross-sectional view of a group 13 nitride semiconductor crystal lump used in the present invention. FIG. 6 is a schematic diagram of a crystal manufacturing apparatus that can be used in the present invention.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

As shown in FIG. 1, the group 13 nitride compound used as the material of the group 13 nitride crystal according to the present invention has a hexagonal crystal structure. In this specification, the “principal surface” refers to the widest surface in the crystal, and usually the surface on which crystal growth is to be performed. The “side surface” means a surface that intersects the main surface, and may or may not be adjacent to the main surface.
In this specification, the “C plane” is a plane equivalent to the {0001} plane in a hexagonal crystal structure (wurtzite type crystal structure), and is a polar plane. For example, it refers to the (0001) plane shown in FIG. 1 and the (000-1) plane opposite to the (0001) plane, and may be referred to as + C plane and −C plane, respectively. In the group 13 nitride crystal, the + C plane is a group 13 plane of the periodic table and the −C plane is a nitrogen plane, and in gallium nitride, it corresponds to a Ga plane or an N plane, respectively.
Further, in this specification, the “M plane” refers to {1-100} plane, {01-10} plane, {-1010} plane, {−1100} plane, {0-110} plane, {10-10 } Non-polar planes comprehensively represented as planes, specifically (1-100) plane, (01-10) plane, (-1010) plane, (-1100) plane, (0-110). ) Plane and (10-10) plane. Further, in this specification, the “A plane” means {2-1-10} plane, {-12-10} plane, {-1-120} plane, {-2110} plane, {1-210} plane. , {11-20} plane which is comprehensively represented as a plane. Specifically, the (11-20) plane, (2-1-10) plane, (-12-10) plane, (-1-120) plane, (-2110) plane, (1-210) plane means. In this specification, “c-axis”, “m-axis”, and “a-axis” mean axes perpendicular to the C-plane, M-plane, and A-plane, respectively.
In the present specification, the “nonpolar plane” means a plane in which both a Group 13 element and a nitrogen element are present on the surface and the abundance ratio thereof is 1: 1. Specifically, the M surface and the A surface can be mentioned. In the present specification, the term “polar plane” or “non-polar plane” includes a plane within a range having an off angle of less than 10 ° from each crystal axis measured with an accuracy within ± 0.01 °. The off angle is preferably within 5 °, more preferably within 3 °. Similarly, the c-axis, m-axis, and a-axis also include axial directions within a range having an off angle.

In this specification, the “semipolar plane” means, for example, that when the periodic table group 13 nitride is hexagonal and the main surface is represented by (hklm), except for the {0001} plane, when m = 0 It means no side. That is, it refers to a plane that is inclined with respect to the (0001) plane and is not a nonpolar plane. It means a surface in which only one of the group 13 element and nitrogen element in the periodic table or the C surface is present on the surface, and the abundance ratio is not 1: 1. h, k, l and m are each independently preferably an integer of -5 to 5, more preferably an integer of -2 to 2, and preferably a low index surface. .
In this specification, the semipolar plane may be expressed as the S plane. In addition, an axis perpendicular to the semipolar plane may be expressed as “s-axis”. Therefore, the direction inclined at an angle of 10 ° to 80 ° from the m-axis to the c-axis direction coincides with the s-axis direction.

(Method for producing Group 13 nitride crystal)
The manufacturing method of a periodic table group 13 metal nitride semiconductor crystal according to the present invention includes a first growth step of growing a first periodic table group 13 metal nitride crystal layer on a base substrate having an M plane as a main surface; After the first growth step, a plate-like crystal manufacturing step for obtaining a plate-like crystal having a M-plane having a larger area than the main surface of the base substrate from the first periodic table group 13 metal nitride crystal layer. including. The first periodic table group 13 metal nitride crystal layer is formed of a periodic table group 13 metal nitride semiconductor, and has at least an M plane and a semipolar plane as a growth surface on a base substrate having the M plane as a main surface. As described above, the crystal is grown by an ammonothermal method. The ammonothermal method is a method for producing a desired material by using a dissolution-precipitation reaction of raw materials using a solvent containing nitrogen such as ammonia in a supercritical state and / or a subcritical state.

  The periodic table group 13 metal nitride semiconductor crystal includes a periodic table group 13 metal nitride crystal layer, and may or may not include a base substrate. The periodic table group 13 metal nitride semiconductor crystal may be a bulk semiconductor crystal or a plate-like semiconductor crystal. In this specification, an as-grown crystal obtained by growing a periodic table group 13 metal nitride crystal layer on a base substrate is referred to as a periodic table group 13 metal nitride crystal lump (group 13 nitride crystal lump). When the main surface of the Group 13 nitride crystal mass is an M-plane having a larger area than the main surface of the base substrate, the Group 13 nitride crystal mass itself is used as the Group 13 nitride crystal of the present invention. Also good.

  The first growth step is a step of growing a crystal on a base substrate having an M plane as a main surface to obtain a first periodic table group 13 metal nitride crystal layer. In the first growth step, a crystal is grown with at least the M plane and the semipolar plane as growth planes. An ammonothermal method is used for crystal growth. In the first growth step, by growing the crystal using at least the M plane and the semipolar plane as the growth plane, the size of the M plane of the obtained crystal layer can be increased.

The base substrate functions as a seed crystal. The main surface here means the surface having the maximum area among the surfaces constituting the crystal, and the main surface of the base substrate is the M plane.
As shown in FIG. 2, the base substrate 40 is a plate-like group 13 nitride seed crystal having a front-side main surface 41 and a back-side main surface. A group 13 nitride semiconductor crystal can be grown on this base substrate to obtain a grown crystal lump having an M (10-10) plane as a main surface on the front side. The plane orientation of the base substrate is not limited to the above-described aspect, but is preferably M (10-10) ± 15 °.

The base substrate has a hexagonal crystal structure. As the group 13 nitride seed crystal, a single crystal of nitride grown as a growth crystal is used. Specific examples of the group 13 nitride seed crystals include nitride single crystals such as gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), or mixed crystals thereof.
The base substrate can be determined in consideration of lattice matching with the grown crystal. For example, as a seed crystal, a single crystal obtained by epitaxial growth on a heterogeneous substrate such as sapphire and then exfoliated, a single crystal obtained by crystal growth of Na, Li, Bi as a flux from a metal such as Ga, a liquid phase A homocrystal / heteroepitaxially grown single crystal obtained by using an epitaxy method (LPE method), a single crystal produced based on a solution growth method, a crystal obtained by cutting them, and the like can be used. The specific method of epitaxial growth is not particularly limited. For example, a hydride vapor phase growth method (HVPE) method, a metal organic chemical vapor deposition method (MOCVD method), a liquid phase method, an ammonothermal method, or the like is adopted. Can do.

The base substrate used in the present invention is not particularly limited as long as it is a plate-like group 13 nitride seed crystal having a main surface on the front side and a main surface on the back side, but the main surface on the front side and the main surface on the back side are substantially the same. It is preferable that they are parallel. It is more preferable that the main surface on the front side and the main surface on the back side are both M surfaces.
The shape of the seed crystal is not particularly limited, but a large-area growth crystal can be obtained efficiently, so that the outer shape of the main surface is a shape having a longitudinal direction and a short direction such as a rectangle or an ellipse. It is preferable that the straight line extending in the longitudinal direction and the straight line extending in the short direction intersect substantially perpendicularly. The side surface of the seed crystal may be flat or curved. Examples of the shape of the seed crystal include a rectangular parallelepiped, a triangular plate, a pentagonal plate, a hexagonal plate, a disc, a triangular prism, a pentagonal column, a hexagonal column, and a cylinder. Among them, the base substrate used in the present invention is more preferably a plate-shaped rectangular parallelepiped seed crystal.

  The thickness of the base substrate used in the present invention (when the M surface is the main surface, the dimension in the m-axis direction) is preferably 0.1 mm or more, and more preferably 0.2 mm or more from the viewpoint of handleability. In addition, when the seed crystal is too thick, the ratio of the seed crystal in the grown crystal is increased, leading to an increase in manufacturing cost and cost. Therefore, the thickness of the seed crystal is preferably 2 mm or less, More preferably, it is 1 mm or less.

The base substrate used in the present invention is not limited to the size of the main surface on the front side of the base substrate, but the size in the c-axis direction, which is the longitudinal direction of the main surface on the front side of the base substrate, is 200 mm or less as the seed crystal size. Is preferably 150 mm or less, more preferably 5 mm or more, and even more preferably 10 mm or more. On the other hand, the dimension in the a-axis direction, which is the lateral direction of the main surface on the front side of the base substrate, is preferably 300 mm or less, more preferably 200 mm or less, preferably 10 mm or more, and 15 mm or more. Is more preferable.
Further, in the base substrate used in the present invention, the dimensions of the main surface on the front side and the dimensions of the main surface on the back side are preferably substantially the same, and the preferred range of the dimensions of the main surface on the back side of the base substrate used in the present invention. Is the same as the preferred range of dimensions of the main surface on the front side.

The manufacturing method of the periodic table group 13 metal nitride semiconductor crystal of the present invention is a plate crystal having an M plane as a main surface from the first periodic table group 13 metal nitride crystal layer after the first growth step. It further includes a plate-like crystal production step for obtaining The plate crystal production step is a step of obtaining a plate crystal from the first periodic table group 13 metal nitride crystal layer obtained in the first growth step. The plate crystal has an area larger than the area of the main surface of the base substrate used for the growth of the first periodic table group 13 metal nitride crystal layer. That is, the M-plane area of the plate crystal is larger than the M-plane area of the base substrate.
The plate-like crystal obtained in the plate-like crystal production step may be a surface in which at least one of the crystal surfaces as the main surface is composed of the first periodic table group 13 metal nitride crystal layer, and the entire plate-like crystal is The first periodic table group 13 metal nitride crystal layer does not have to be formed alone. Therefore, the base substrate may be included in the plate crystal.

  The plate-like crystal may be the first periodic table group 13 metal nitride crystal layer itself obtained in the first growth step, or may be a part of the first periodic table group 13 metal nitride crystal layer. May be. When the plate crystal is the first periodic table group 13 metal nitride crystal layer itself, the first periodic table group 13 metal nitride crystal layer can be removed from the base substrate to form a plate crystal. . In this case, the first periodic table group 13 metal nitride crystal layer is preferably plate-shaped, and the area of the main surface of the first periodic table group 13 metal nitride crystal layer is the main surface of the base substrate. It is preferable that it is larger than the area.

  When the plate-like crystal is a part of the first periodic table group 13 metal nitride crystal layer, the plate-like crystal is obtained by slicing the first periodic table group 13 metal nitride crystal layer into a plate shape. Is preferred. In this case, the plate crystal manufacturing step includes a step of slicing the first periodic table group 13 metal nitride crystal layer. In the step of slicing the first periodic table group 13 metal nitride crystal layer, slicing is performed so that the principal surface of the plate-like crystal becomes the M plane.

  The area of the main surface of the plate crystal is larger than the area of the main surface of the base substrate. The first periodic table group 13 metal nitride crystal layer is obtained by growing at least the M plane and the semipolar plane as growth planes. For this reason, the periodic table group 13 metal nitride crystal layer has a layer portion larger than the area of the main surface of the base substrate or larger than the area of the main surface of the base substrate. As the plate crystal, it is preferable to use a periodic table group 13 metal nitride crystal layer larger than the area of the main surface of the base substrate.

  When the area of the main surface of the base substrate is P and the area of the main surface of the plate crystal is Q, Q / P is preferably 1.05 to 10. Q / P may be 1.05 or more, preferably 1.1 or more, more preferably 1.5 or more, and Q / P may be 10 or less, and 9 or less. It is preferable that it is 8 or less. By setting Q / P within the above range, a Group 13 nitride crystal having a large crystal layer area can be produced. Moreover, manufacturing efficiency can be improved more by making Q / P into the said range.

In the step of slicing the first periodic table group 13 metal nitride crystal layer so that the area of the main surface of the base substrate and the area of the main surface of the plate crystal are as described above, the slicing position is adjusted. can do. In the slicing step, it is preferable to slice the crystal at a position where a plate-like crystal having an area larger than that of the base substrate can be obtained. For this reason, the slicing position varies greatly depending on the shape of the crystal.
For example, when the first periodic table group 13 metal nitride crystal layer is grown in a shape such that the cross-sectional area of the first periodic table group 13 metal nitride crystal layer is larger than that of the base substrate, the first periodic table group 13 metal nitride crystal is used in the slicing step. It is preferable to slice at any depth within a range of 90% or less from the base substrate with respect to the thickness of the layer. The slice position may be sliced from the surface of the first periodic table group 13 metal nitride crystal layer at a depth within a range of 90% or less from the base substrate with respect to the thickness of the crystal layer, It is preferably within a range of 60% or less from the base substrate, and more preferably within a range of 45% or less from the base substrate.
Further, when the first periodic table group 13 metal nitride crystal layer is grown in such a shape that the cross-sectional area of the first periodic table group 13 metal nitride crystal layer is smaller than that of the base substrate, the slice position is the first periodic table group 13 metal nitride crystal. It is preferable to slice from the surface of the layer at any depth within a range of 45% or less from the base substrate with respect to the thickness of the crystal layer.
For example, when the shape of the group 13 nitride crystal mass (growth crystal mass) obtained by growing the first periodic table group 13 metal nitride crystal layer on the base substrate is as shown in FIG. When sliced at a position of 45.9% or less from the base substrate, the cut plate crystal has a larger area than the base substrate. In the case of FIG. 5B, if the slice is made at a position of 58% or less from the base substrate, the cut-out plate crystal has a larger area than the base substrate. In the case of FIGS. 5C to 5E, the plate crystal has a larger area than the base substrate regardless of where it is sliced.

  In the slicing step, the crystal layer may be sliced multiple times. The number of times of slicing can be appropriately determined according to the thickness required for the plate crystal. As described above, the plate-like crystal manufacturing step includes the step of slicing the first periodic table group 13 metal nitride crystal layer, whereby a plate-like substrate having a principal surface larger than the area of the principal surface of the base substrate is obtained. Can be obtained.

When the group 13 nitride crystal layer is grown using at least the M plane and the semipolar plane as the growth plane in the first growth step, the obtained group 13 nitride crystal mass has a periodic table 13th grown in the m-axis direction. An M-plane growth region composed of a group metal nitride crystal and a semipolar plane growth region composed of a periodic table group 13 metal nitride crystal grown in a direction inclined at an angle of 10 ° to 80 ° from the m-axis to the c-axis direction. Will have.
Therefore, the plate-like crystal of the present invention also has an M-plane growth region made of a periodic table group 13 metal nitride crystal grown in the m-axis direction and a direction inclined from the m-axis to the c-axis direction by an angle of 10 ° to 80 °. It is preferable to include a semipolar plane growth region made of a periodic table group 13 metal nitride crystal grown in the same manner. The semipolar plane growth regions are preferably formed in regions facing each other so as to sandwich the M plane growth region. That is, the M-plane growth region is a region sandwiched between the semipolar plane growth regions, and two or more semipolar plane growth regions are preferably formed.
The semipolar plane growth region is composed of a periodic table group 13 metal nitride crystal grown using the semipolar plane as a growth plane. A part of the exposed region of the semipolar plane growth region of the plate crystal may include a semipolar plane. Here, the exposed region refers to a surface region of the semipolar plane growth region of the plate crystal and includes a part of the edge. A semipolar plane growth region grows with a semipolar plane as a growth plane, and a plate crystal having an M plane as a main surface so as to include the semipolar plane is obtained, thereby increasing the M plane area of the plate crystal. be able to.
It should be noted that the semipolar plane can be prevented from being included in the exposed region of the semipolar plane growth region by scraping or polishing the outer periphery of the plate crystal.

  The semipolar plane serving as a growth plane preferably includes at least one of a [10-11] plane and a [10-1-1] plane. When the semipolar plane includes these planes, the production efficiency can be further increased, and the area of the main surface of the plate crystal can be increased.

  The main surface of the semipolar plane growth region appearing on the main surface of the plate-like crystal is the M plane, and these M planes are a series of planes having the M plane as the main plane in succession to the M plane of the M plane growth region. It becomes. Thereby, the area of the plate-like crystal having the M plane as the main surface can be increased.

  The ratio of the M-plane area of the M-plane growth region to the area of the entire main surface of the plate crystal is preferably 50% or more. The M-plane area of the M-plane growth region may be 50% or more, preferably 60% or more, and more preferably 70% or more with respect to the entire area of the main surface of the plate crystal. Moreover, it is preferable that it is 95% or less, and it is more preferable that it is 90% or less. By setting the ratio of the M-plane area in the M-plane growth region within the above range, the area of the plate crystal having the M-plane as the main surface can be increased, and it is high against external stress such as processing. Since the proportion of the M-plane growth region, which is a high-quality region having strength and good crystallinity, is increased, it is preferable because handling of the plate crystal can be facilitated.

  In the main surface of the plate crystal, the M-plane area of the M-plane growth region is preferably larger than the M-plane area of the main surface of the base substrate. By making the M-plane area of the M-plane growth region larger than the M-plane area of the main surface of the base substrate, the M-plane growth region, which is a high quality region, can be obtained more widely, and the M-plane is the main surface. The area of the plate crystal can be increased. Also, a crystal grown on a plate-like crystal has a wider M-plane growth region, and the yield at the time of manufacturing a device using the crystal as a wafer is improved.

  The plate crystal may be a plate crystal, and the shape of the plate crystal is not particularly limited, but is a rectangular parallelepiped, a triangular plate shape, a pentagonal plate shape, a hexagonal plate shape, a disc shape, a triangular prism, a pentagonal column, a hexagonal column, It can be a column, a cylinder, or the like. Among these, the shape of the plate crystal is preferably a plate-shaped cuboid crystal.

  The thickness of the plate crystal can be appropriately determined by design. For example, the thickness of the plate crystal is preferably 100 μm or more, more preferably 200 μm or more, and further preferably 250 μm or more. Moreover, it is preferable that it is 700 micrometers or less, It is more preferable that it is 650 micrometers or less, It is further more preferable that it is 500 micrometers or less.

  According to the method for producing a periodic table group 13 metal nitride semiconductor crystal of the present invention, a second periodic table group 13 metal nitride crystal layer is grown on the plate crystal after the plate crystal manufacturing step. It is preferable to further include a growth step. In this second growth step, a crystal is grown on the plate-like crystal obtained in the plate-like crystal production step with at least the M plane and the semipolar plane as the growth plane. An ammonothermal method is used for crystal growth. In the second growth step in addition to the first growth step, the size of the obtained crystal layer can be further increased by growing the crystal using at least the M plane and the semipolar plane as the growth plane.

  The first growth step preferably includes a step of reacting a mineralizer containing at least one element selected from fluorine, chlorine, bromine and iodine. Furthermore, it is preferable that the second growth step also includes a step of reacting a mineralizer containing at least one element selected from fluorine, chlorine, bromine and iodine. In the present invention, in the first growth step and / or the second growth step, by including a step of reacting a mineralizer containing at least one element selected from fluorine, chlorine, bromine and iodine, Alternatively, the crystal can be grown on the plate crystal using the M plane and the semipolar plane as growth planes. Thereby, the size of the obtained crystal layer can be increased.

  The mineralizer used in the first growth step and / or the second growth step is preferably one containing fluorine and iodine. By including fluorine and iodine in the mineralizer, crystals can be efficiently grown using the M-plane and semipolar plane as growth planes. Further, when iodine and fluorine are used as mineralizers, iodine and fluorine are preferable because they are hardly taken into the crystal and do not affect the crystal quality. In particular, the case where iodine and fluorine are used in combination is more preferable than the case where fluorine is used alone because the incorporation into the crystal is suppressed.

  When the concentration of fluorine contained in the mineralizer is F and the concentration of iodine contained in the mineralizer is I, the I / F is preferably 0.5-10. The I / F may be 0.5 or more, preferably 1 or more, and more preferably 2 or more. Moreover, I / F should just be 10 or less, it is preferable that it is 9 or less, and it is more preferable that it is 8 or less. By setting the I / F within the above range, the crystal can be efficiently grown using the M plane and the semipolar plane as the growth plane. Thereby, the size of the obtained crystal layer can be further increased.

(Group 13 nitride crystal)
The present invention relates to a periodic table group 13 metal nitride semiconductor crystal obtained by growing a crystal using the manufacturing method described above. The periodic table group 13 metal nitride semiconductor crystal grown using the manufacturing method described above has an M plane as a main surface, and further includes an M plane growth region and a semipolar plane growth region.

As shown in FIG. 3, a crystal can be grown on a base substrate 40 that is a seed crystal to obtain a periodic table group 13 metal nitride semiconductor crystal lump 100. The main surface 51 of the periodic table group 13 metal nitride semiconductor crystal lump formed on the front-side main surface 41 of the base substrate 40 is an M (10-10) plane.
The semiconductor crystal lump has a Group 13 nitride semiconductor crystal layer (growth crystal) formed on the base substrate. The group 13 metal nitride semiconductor crystal mass of the periodic table is obtained by growing a group 13 nitride semiconductor crystal layer of the same type as the seed crystal.
Here, even when the plate-like crystal of the present invention is used as a seed crystal and the second group 13 nitride semiconductor crystal layer is grown, the periodic table group 13 metal nitride as shown in FIG. 3 is used. It is preferable to obtain a semiconductor crystal.

  The periodic table group 13 metal nitride semiconductor crystal layer is not particularly limited as long as it has a hexagonal crystal structure, but examples of the group 13 nitride crystal include a periodic table represented by GaN and AlN. Examples include Group 13 metal nitride crystals. Examples of the periodic table group 13 metal nitride include GaN, AlN, InN, and mixed crystals thereof. 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.

The oxygen concentration of the periodic table group 13 metal nitride semiconductor crystal layer is preferably 1 × 10 ²⁰ atoms / cm ³ or less, more preferably 5 × 10 ¹⁹ atoms / cm ³ or less, and 1 × 10 6. More preferably, it is ¹⁹ atoms / cm ³ or less. By setting the oxygen concentration of the group 13 nitride crystal layer in the above range, the ratio of the M-plane growth region and the semipolar plane growth region contained in the group 13 nitride crystal can be made a more preferable ratio.

The concentration of the metal and alkali metal in the Group 13 metal nitride semiconductor crystal layer of the periodic table is preferably 1 × 10 ¹⁶ atoms / cm ³ or less, more preferably 1 × 10 ¹⁵ atoms / cm ³ or less. . Here, the said density | concentration points out the total density | concentration of the density | concentration of a metal and an alkali metal. By setting the metal and alkali metal concentrations in the group 13 nitride crystal layer within the above range, the ratio of the M-plane growth region and the semipolar plane growth region included in the group 13 nitride crystal is set to a more preferable ratio. Can do.

The dislocation density of the periodic table group 13 metal nitride semiconductor crystal is preferably 1 × 10 ⁷ cm ⁻³ or less, more preferably 1 × 10 ⁶ m ⁻³ or less, and 1 × 10 ³ cm ^−. More preferably, it is ³ or less. The dislocation density may be 0 as long as it is within the above range.

FIG. 4 shows a cross-sectional view of the periodic table group 13 metal nitride semiconductor crystal block shown in FIG. Further, FIG. 5 shows a cross-sectional view of an example of a periodic table group 13 metal nitride semiconductor crystal lump of various modes. As can be seen from these cross-sectional views, in the periodic table group 13 metal nitride semiconductor crystal lump, the entire surface of the base substrate is covered with the growth crystal.
The group 13 nitride semiconductor crystal according to the present invention can be obtained by slicing, grinding, polishing, or the like the above-described grown crystal mass. For example, as shown in FIG. 5, a plate-like crystal can be obtained by slicing along a slice line indicated by a dotted line A.

In the periodic table group 13 metal nitride semiconductor crystal mass (hereinafter sometimes referred to as a grown crystal mass) according to the present invention, the crystal surface includes at least a {10-11} or {10-1-1} plane. The periodic table group 13 metal nitride semiconductor crystal block has a semipolar plane (Semi-Polar plane) as a surface so that such a {10-11} or {10-1-1} plane is formed. So that it grows under control. The semipolar plane may be a plane in which a plurality of crystal planes are aggregated.
The periodic table group 13 metal nitride semiconductor crystal lump according to the present invention has an M (10-10) plane as the main surface 51 and S (10-1-1) as the side surface as shown in FIGS. ) Plane and S (10-11) plane at least while appearing, having an M (10-10) plane as a main surface in an as-grown state, and an S (10-1-1) plane as a side surface It is preferable to include at least the S (10-11) plane. Furthermore, it grows while making at least one of the (0001) plane and the (000-1) plane appear, and has at least one of the (0001) plane and the (000-1) plane in the as-grown state. Also good. Preferably, it has a (0001) plane in an as-grown state. 3 to 5, 53 and 54 are M (10-10) planes, 61, 63 and 64 are S (10-1-1) planes, and 71 to 76 are S (10-11) planes.

  In order for the crystal surface of the Group 13 metal nitride semiconductor crystal of the periodic table to include at least the M plane and the {10-11} or {10-1-1} plane, It is preferable to use a mineralizer containing at least one selected from the group consisting of chlorine, bromine and iodine. As the mineralizer, those containing elemental fluorine and iodine are particularly preferable. As described above, when a mineral containing a fluorine element and iodine is used as a mineralizer, a crystal having at least a {10-11} or {10-1-1} plane and having a large main surface can be easily obtained.

The M-plane growth region and the semipolar growth region contain fluorine atoms in the periodic table group 13 metal nitride crystal. The concentration of fluorine atoms contained in the periodic table group 13 metal nitride crystal constituting the M-plane growth region is preferably 1 × 10 ¹⁵ atoms / cm ³ or more. The fluorine concentration may be 1 × 10 ¹⁵ atoms / cm ³ , and more preferably 1 × 10 ¹⁶ atoms / cm ³ or more. The fluorine concentration is preferably 1 × 10 ²⁰ atoms / cm ³ or less, and more preferably 1 × 10 ¹⁹ atoms / cm ³ or less. The concentration of fluorine atoms contained in the periodic table group 13 metal nitride crystal constituting the semipolar plane growth region is preferably 1 × 10 ¹⁶ atoms / cm ³ or more. The fluorine concentration is preferably 1 × 10 ²⁰ atoms / cm ³ or less. By setting the fluorine concentration in the group 13 metal nitride crystal of the periodic table within the above range, the ratio of the M-plane area of the M-plane growth region to the total area of the main surface of the plate-like crystal is 50% or more. can do.

Further, by reducing the concentration of impurities in the periodic table Group 13 metal nitride crystal layer (growth crystal) to be grown, growth with the growth surface as a semipolar surface can be promoted. At this time, the impurity concentration can be based on oxygen concentration, alkali metal, transition metal concentration such as Ni, or the like. For example, by setting the oxygen concentration in the grown crystal to less than 10 ²⁰ atoms / cm ³ , growth with the growth surface as a semipolar surface can be promoted. As a result, the semipolar plane appearing on the surface of the grown crystal lump is narrowed and the M-plane is widened, which is preferable because a high quality region in the group 13 nitride substrate of the present invention can be widened. The oxygen atom concentration when oxygen atoms are contained as impurity atoms in the grown crystal is preferably 1 × 10 ²⁰ atoms / cm ³ or less, more preferably 5 × 10 ¹⁹ atoms / cm ³ or less. × and more preferably 10 ¹⁹ atoms / cm ³ or less.

  Further, the growth of the growth surface as a surface including the M plane and the semipolar plane can be promoted by appropriately selecting the shape of the seed crystal, the processing method, and the like.

(Crystal growth by ammonothermal method)
In the first growth step and the second growth step of the manufacturing method of the present invention, an ammonothermal method is used for crystal growth.
The mineralizer, solvent, and raw material which can be used for the ammonothermal method in the present invention are described below.

(Mineralizer)
In the growth of nitride crystals by the ammonothermal method in the present invention, a mineralizer is preferably used. Since the solubility of the crystal raw material in a solvent containing nitrogen such as ammonia is not high, a mineralizer is used to improve the solubility.
As the mineralizer, a mineralizer containing at least one element selected from fluorine element and other halogen elements composed of chlorine, bromine and iodine is preferably used.

The combination of halogen elements contained in the mineralizer may be a combination of two elements such as chlorine and fluorine, bromine and fluorine, iodine and fluorine, chlorine and bromine and fluorine, chlorine and iodine and fluorine, bromine and iodine. It may be a combination of three elements such as fluorine and fluorine, or a combination of four elements such as chlorine, bromine, iodine and fluorine. Preferred is a combination containing at least iodine and fluorine from the viewpoint of controlling the surface expressed in the a-axis direction to a semipolar surface as described above. The combination and concentration ratio (molar concentration ratio) of the halogen elements contained in the mineralizer used in the present invention are the type, shape and size of the nitride crystal to be grown, and the type, shape and size of the seed crystal used. It can be appropriately determined depending on the reaction apparatus, the temperature conditions and pressure conditions employed, and the like.
For example, in the case of a mineralizer containing iodine (I) and fluorine (F), the iodine concentration relative to the fluorine concentration, that is, the I / F is preferably 0.5 or more, more preferably 0.7 or more. More preferably, it is 1 or more. The I / F is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less.

  Generally, when the fluorine concentration of the mineralizer is increased, the growth rate of the nitride crystal in the m-axis direction tends to increase, and the growth in the c-axis direction and the growth perpendicular to the semipolar plane tend to be relatively slow. It is in. This means that the difference in growth rate depending on the plane orientation can be controlled by changing the mineralizer concentration. In a grown crystal, the area of the crystal plane that appears in a direction in which the growth rate is slow tends to increase. Therefore, when growth in a direction perpendicular to the semipolar plane (growth with the semipolar plane as the growth plane) is slow, the semipolar plane appearing on the surface of the obtained group 13 nitride crystal block becomes relatively large. In this way, if the surface area where the growth rate is high becomes narrower and the area where the surface direction where the growth rate is relatively slow can be controlled to be wider, the main surface of the plate crystal can be made wider. It is preferable because a high quality region included in the group 13 nitride semiconductor crystal of the present invention can be widened.

  Examples of mineralizers containing halogen elements include ammonium halide, hydrogen halide, ammonium hexahalosilicate, and hydrocarbyl ammonium fluoride, tetramethylammonium halide, tetraethylammonium halide, benzyltrimethylammonium 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 halogens of Group 13 metals of the periodic table. A halide and a hydrogen halide, particularly preferably an ammonium halide, a gallium halide and a hydrogen halide.

In the production process, a mineralizer containing no halogen element can be used together with a mineralizer containing a halogen element. For example, it can be used in combination with an alkali metal amide such as NaNH ₂ , KNH _2, or LiNH _2. it can. 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.

  In addition to changing the concentration of the mineralizer, the growth rate can be changed by the dopant. In the manufacturing process, the mineralizer can be used after being purified and dried as necessary in order to prevent impurities from being mixed into the nitride crystal to be grown. 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 ppm or less, more preferably 10 ppm or less, and further preferably 1.0 ppm or less. . By controlling the oxygen concentration within these ranges, the higher the oxygen concentration, the lower the growth rate in the direction perpendicular to the semipolar plane, that is, the area of the semipolar plane tends to increase. On the other hand, the lower the oxygen concentration, the higher the growth rate in the direction perpendicular to the semipolar plane, that is, the area of the semipolar plane tends to decrease.

  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.

  The molar concentration of the halogen element contained in the mineralizer with respect to the solvent is preferably 0.1 mol% or more, more preferably 0.3 mol% or more, and further preferably 0.5 mol% or more. The molar concentration of the halogen element contained in the mineralizer is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less. If the concentration is too low, the solubility tends to decrease and the growth rate tends to decrease. On the other hand, when the concentration is too high, there is a tendency that the solubility becomes too high and the generation of spontaneous nuclei increases, or the supersaturation degree becomes too high and control becomes difficult.

(solvent)
As a solvent used in the ammonothermal method, a solvent containing nitrogen can be used. Examples of the solvent containing nitrogen include a solvent that does not impair the stability of the grown nitride single crystal. 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 ppm or less, more preferably 10 ppm or less, and further preferably 0.1 ppm 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 manufacturing process, a raw material containing an element constituting a nitride crystal to be grown as a growth crystal on a seed crystal is used. For example, when a nitride crystal of a periodic table 13 group metal is to be grown, a raw material containing a periodic table 13 group metal is used. Preferred is a polycrystalline raw material of a group 13 nitride crystal and / or a group 13 metal, and more preferred is gallium nitride and / or metal gallium. The polycrystalline raw material does not need to be a complete nitride, and may contain a metal component in which the group 13 element is in a metal state (zero valence) depending on conditions. For example, when the crystal is gallium nitride Is a mixture of gallium nitride and metal gallium.

  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 raw material having higher reactivity, a compound having a covalent MN bond such as a halide, an amide compound, an imide compound, or galazan 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.

  The amount of water and oxygen contained in the polycrystalline raw material used as the raw material in the present invention is preferably small. The oxygen content in the polycrystalline raw material is usually 10,000 ppm or less, preferably 1000 ppm or less, particularly preferably 1 ppm or less. The ease of mixing oxygen into the polycrystalline raw material is related to the reactivity with water or the absorption capacity. The worse the crystallinity of the polycrystalline raw material, the more active groups such as NH groups exist on the surface, which may react with water and partially generate oxides or hydroxides. For this reason, it is usually preferable to use a polycrystalline material having as high crystallinity as possible. The crystallinity can be estimated by the half width of powder X-ray diffraction. The half width of the (100) diffraction line (2θ = about 32.5 ° for hexagonal gallium nitride) is usually 0.25 ° or less, preferably It is 0.20 ° or less, more preferably 0.17 ° or less.

(manufacturing device)
A specific example of a crystal manufacturing apparatus that can be used in the nitride crystal manufacturing method of the present invention is shown in FIG. The crystal production apparatus used in the present invention includes a reaction vessel. FIG. 6 is a schematic diagram of a crystal manufacturing apparatus that can be used in the present invention. In the crystal manufacturing apparatus shown in FIG. 6, 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. The baffle plate 5 has a hole area ratio of preferably 2 to 60%, more preferably 3 to 40%. The material of the surface of the baffle plate is preferably the same as the material of the capsule 20 that is a reaction vessel. Further, in order to give more corrosion resistance and to purify the crystal to be grown, the surface of the baffle plate is Ni, Ta, Ti, W, Mo, Ru, Nb, Pd, Pt, Au, Ir, pBN. Of these, W, Mo, Ti, Pd, Pt, Au, Ir, and pBN are more preferable, and Pt, Mo, and Ti are particularly preferable.
In the crystal manufacturing apparatus shown in FIG. 6, the gap between the inner wall of the autoclave 1 and the capsule 20 can be filled with the second solvent. Here, ammonia can be filled as the second solvent while filling the nitrogen gas from the nitrogen cylinder 13 through the valve 10 or confirming the flow rate from the ammonia cylinder 12 with the mass flow meter 14. In addition, the vacuum pump 11 can perform necessary pressure reduction. Note that a valve, a mass flow meter, and the like are not necessarily installed in the crystal manufacturing apparatus used when the nitride crystal manufacturing method of the present invention is performed.

  Lining can also be used to provide corrosion resistance by autoclaving. The lining material is preferably at least one metal or element of Pt, Ir, Ag, Pd, Rh, Cu, Au and C, or an alloy or compound containing at least one metal, More preferably, it is an alloy or compound containing at least one or more metals or elements of Pt, Ag, Cu and C, or at least one or more metals because they are easily lined. For example, Pt simple substance, Pt-Ir alloy, Ag simple substance, Cu simple substance, graphite, etc. are mentioned.

(Manufacturing process)
An example of the method for producing a nitride crystal of the present invention will be described. In carrying out the method for producing a 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. Here, as the seed crystal, a nitride crystal grown with the C-plane as the main surface is cut out in a desired direction, whereby a substrate whose main surface is a nonpolar surface or a semipolar surface can be obtained. Thereby, a seed crystal having a nonpolar plane such as an M plane and a semipolar plane such as (10-11) or (20-21) can be obtained.

  In the production process of the present invention, a dopant source isolation step may be further provided prior to introducing the material into the reaction vessel. The dopant source isolation step refers to a step of removing oxygen, oxide or water vapor present in the reaction vessel. The dopant source isolation step includes a step of coating or lining the surface of a reaction vessel or a member containing oxygen, oxide, or water vapor among various members installed in the reaction vessel. Coating or lining the surface of the member can prevent the dopant from being exposed and incorporated into the nitride crystal.

  In order to remove oxygen, oxides or water vapor present in the reaction vessel, the reaction vessel is filled with a nitride crystal raw material, and then the reaction vessel is evacuated, or an inert gas is contained in the reaction vessel. A method that satisfies the above can be adopted. In addition, oxygen, oxides, or water vapor can be removed by drying the reaction vessel and various members included in the reaction vessel.

At the time of introducing the material, an inert gas such as nitrogen gas may be circulated. Usually, the seed crystal is placed in the reaction vessel at the same time or after filling the raw material and the mineralizer. The seed crystal is preferably fixed to a noble metal jig similar to the noble metal constituting the inner surface of the reaction vessel. After installation of the seed crystal, heat deaeration may be performed as necessary.
When the production apparatus shown in FIG. 6 is used, after encapsulating the seed crystal 7, the solvent containing nitrogen, the raw material, and the mineralizer in the capsule 20, which is a reaction vessel, the capsule 20 is autoclaved (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 or a subcritical state. In the supercritical state, the viscosity of a substance is generally low and it diffuses more easily than a liquid, but has a solvating power similar to that of a 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 part, the raw material is melted as a supercritical state, and in the crystal growth part, the temperature is changed so as to be in the subcritical state, and crystal growth utilizing the difference in solubility between the supercritical state and the subcritical state raw 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 an ammonia solvent is used, the critical point is a critical temperature of 132 ° C. and a critical pressure of 11.35 MPa. However, 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 nitride crystals can be obtained. The reaction time depends in particular on the reactivity of the mineralizer and the thermodynamic parameters, ie temperature and pressure values. During the synthesis or growth of the 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 method for producing a 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. 6 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.

Nitride crystal growth in the reaction vessel is maintained in a subcritical or supercritical state of a solvent such as ammonia by heating and heating the reaction vessel using an electric furnace with a thermocouple. Is done. 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.

  In the method for producing a nitride crystal of the present invention, a pretreatment can be added to the seed crystal. Examples of the pretreatment include subjecting the seed crystal to a meltback process, polishing the growth surface of the seed crystal, and washing the seed crystal.

  In the pretreatment, in order to polish the surface of the seed crystal capable of crystal growth, for example, chemical mechanical polishing (CMP) can be performed. As for the surface roughness of the seed crystal, for example, the root mean square roughness (Rms) measured by an atomic force microscope is preferably 1.0 nm or less, more preferably 0.5 nm, and particularly preferably 0.3 nm. .

  The reaction time after reaching a predetermined temperature varies depending on the type of nitride crystal, the raw material used, the type of mineralizer, and the size and amount of the crystal to be produced, but is usually several hours to several hundred days. be able to. 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 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 the valve connection port of the valve attached to the reaction vessel, leading to a vessel filled with water or the like. Furthermore, if necessary, remove the ammonia solvent in the reaction vessel sufficiently by applying a vacuum, etc., then dry, open the reaction vessel lid, etc., and generate nitride crystals and unreacted raw materials and mineralization. Additives such as agents can be removed.

  In addition, when manufacturing gallium nitride according to the method for manufacturing a nitride crystal of the present invention, JP 2009-263229 A can be preferably referred to for details of materials, manufacturing conditions, manufacturing apparatuses, and processes other than those described above. . The entire disclosure of this publication is incorporated herein by reference.

  In the method for producing a nitride crystal of the present invention, after the nitride crystal is grown on the seed crystal, post-treatment may be added. The type and purpose of post-processing are not particularly limited. For example, the crystal surface may be melted back in the cooling process after growth so that crystal defects such as pits and dislocations can be easily observed.

  The group 13 metal nitride semiconductor crystal of the periodic table 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 nitride crystal or wafer of the present invention is used include a light-emitting diode, a laser diode, and a light-emitting element that combines them with a phosphor. In addition, examples of the electronic device using the nitride crystal or wafer of the present invention 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 and high-power elements include thyristors (SCR, GTO), insulated gate bipolar transistors (IGBT), and Schottky barrier diodes (SBD). . Since the epitaxial wafer of the present invention has a feature of excellent pressure resistance, it is suitable for any of the above applications.

  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: First growth step)
In this example, a nitride crystal was grown using the reaction apparatus shown in FIG.
Crystal growth was carried out using an autoclave 1 having an inner dimension of 30 mm in diameter and 450 mm in length as a pressure vessel, and using a Pt-Ir capsule 20 as a reaction vessel. As the raw material 8, 130 g of polycrystalline GaN particles were weighed and placed in the capsule lower region (raw material dissolution region 9). Next, NH ₄ F having a purity of 99.999% sufficiently dried as a mineralizer was weighed so that the F concentration was 0.5 mol% with respect to the amount of NH ₃ charged, and charged into the capsule. Further, a platinum baffle plate 5 (opening ratio: 32%) was placed between the lower raw material dissolution region 9 and the upper crystal growth region 6. As the seed crystal 7, a plate-shaped hexagonal GaN single crystal (c-axis direction 15 mm, a-axis direction 53 mm) having an M-plane as a main surface and a main surface being a quadrangle was used. The surface of the seed crystal having the M plane as the main surface was subjected to CMP finish. These seed crystals 7 were hung on a platinum seed crystal support frame by a platinum wire and placed in the crystal growth region 6 above the capsule.

  Next, after a cap made of Pt—Ir was connected to the upper part of the capsule 20 by welding, the tube was connected to the HI gas line, and the valve was operated so as to communicate with the vacuum pump 11 to perform vacuum deaeration. Thereafter, the valve was operated so as to pass through the nitrogen cylinder 13 and the inside of the capsule was purged with nitrogen gas. After performing the vacuum degassing and nitrogen purging, it was left to stand overnight while connected to a vacuum pump.

Next, 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. Based on the flow rate control, HI was charged so that the I concentration was 1.5 mol% with respect to the amount of NH ₃ charged, and then the valve was closed again. Next, the capsule was removed from the HI line and connected to an NH ₃ gas line. After the gas line was vacuum degassed, vacuuming was performed with a vacuum pump. Thereafter, the valve of the NH ₃ line was operated, and based on the flow rate control, an equimolar amount of HI gas previously filled with NH ₃ was filled, and the valve was closed. The capsules were then removed from the liquid nitrogen and cooled with dry ice ethanol solvent. Subsequently, the valve was opened again and NH ₃ was filled without touching the outside air. Based on the flow rate control, NH ₃ was filled as a liquid corresponding to about 55% of the effective volume of the capsule (converted to an NH ₃ density of −33 ° C.), and then the valve was closed again. Thereafter, the tube at the top of the cap was sealed with a welder.

Subsequently, the capsule was inserted into the autoclave and the autoclave was sealed. The conduit was connected to the vacuum pump 11 through the valve 10 attached to the autoclave, and the valve was opened to perform vacuum deaeration. Nitrogen gas purging was performed several times as in the capsule. Thereafter, the autoclave 1 was cooled with a dry ice methanol solvent while maintaining the vacuum state, and the valve 10 was once closed. Next, after the conduit was operated to lead to the NH ₃ cylinder 12, the valve 10 was opened again, and NH ₃ was charged into the autoclave 1 without continuously touching the outside air. Based on the flow rate control, NH ₃ was filled as a liquid corresponding to about 56% of the effective volume of the autoclave 1 (autoclave volume−filled volume) (converted to an NH ₃ density of −33 ° C.), and then the valve 10 was closed again. It was.

  Subsequently, the autoclave 1 was housed in an electric furnace composed of a heater divided into two parts in the vertical direction. The temperature was raised while controlling the external temperature of the autoclave so that the average temperature inside the autoclave was 600 ° C. and the internal temperature difference was 20 ° C. After reaching the set temperature, the temperature was maintained at that temperature for 14.8 days. The pressure in the autoclave was 215 MPa. Further, the variation in the control temperature of the outer surface of the autoclave during the holding was ± 0.3 ° C. or less.

Thereafter, the temperature of the outer surface of the autoclave 1 was cooled to 400 ° C., the valve 10 attached to the autoclave was opened, and NH ₃ in the autoclave was removed. At this time, the capsule was divided using the pressure difference between the autoclave and the capsule, and NH ₃ filled in the capsule was also removed.

Then, the lid | cover of the autoclave was opened and the capsule 20 was taken out. When the inside of the capsule was confirmed, a gallium nitride crystal was grown on the seed crystal. In the crystal, the M plane, S plane (10-11), (10-1-1), and + C plane form facets, the M plane is colored pale yellow, and the S plane is brown. Observed. The size of the grown crystal lump was 17 mm in the c-axis direction and 55 mm in the a-axis direction. Further, the M-plane grown region was 12 mm in the c-axis direction and 53 mm in the a-axis direction. The M-plane growth rate relative to the S-plane growth of this crystal was 0.8 (first growth step A). A plate-like GaN crystal was obtained by slicing parallel to the M plane at a position of 10% from the underlying substrate with respect to the growth thickness of the obtained growth crystal mass. The plate-like GaN crystal was approximately quadrangular and was 16 mm in the c-axis direction and 54 mm in the a-axis direction.

(Example 2: First growth step)
In the same procedure as in Example 1, crystal growth is performed in the first step. From a seed crystal of 9.5 mm in the c-axis direction and 25.5 mm in the a-axis direction, 12.5 mm in the c-axis direction and a-axis direction. A GaN growth crystal mass of 29 mm was obtained. At this time, the growth rate of the M plane relative to the S plane was 0.81 (first growth step B). A plate-like GaN crystal was obtained by slicing parallel to the M plane at a position of 10% from the underlying substrate with respect to the growth thickness of the obtained growth crystal mass. The plate-like GaN crystal was approximately quadrangular and was 10 mm in the c-axis direction and 26 mm in the a-axis direction.

(Examples 3 to 7: first growth step)
In the same procedure as in Example 1, the mineralizer concentration was set to I: 0.75F 0.375%, I: 2.0% F: 1.0%, I: 1.5% F: 0.5% Crystal growth was performed by the first step (first growth steps C to F). With respect to the growth thickness of the obtained growth crystal lump, the base substrate was sliced in parallel to the M-plane to obtain a roughly square plate-like GaN crystal. The slice position and size of each plate-like GaN crystal were as shown in Table 1.

(Example 8: 1st growth process)
In the same procedure as in Example 1, crystal growth is performed in the first step, and from a seed crystal of 8 mm in the c-axis direction and 26 mm in the a-axis direction, 13.5 mm in the c-axis direction and 32 mm in the a-axis direction. Crystals were obtained (first growth step G). A plate-like GaN crystal was obtained by slicing parallel to the M-plane at a position of 55% from the underlying substrate with respect to the growth thickness of the obtained growth crystal mass. The plate-like GaN crystal was approximately square and had a size of 13.2 mm in the c-axis direction and 26.5 mm in the a-axis direction.
The results of the first growth process of Examples 1 to 8 are summarized in Table 1.

(Example 2: Second growth step)
The crystal obtained in the first growth step B is sliced in parallel to the M plane, and the obtained plate-like GaN crystal has a size of 10 mm in the c-axis direction and 26 mm in the a-axis direction. The S-plane growth region included in the plane was 86.4%.
The plate-like GaN crystal having the M-plane as the main surface obtained by the first growth step was used as a seed crystal, and crystal growth was performed in the same procedure as in the first growth step. After completion of the growth process, a crystal having 12.7 mm in the c-axis direction and 32 mm in the a-axis direction and no visible defects such as voids and cracks on the surface is obtained, which is compared with the base substrate used in the first growth process. A GaN crystal having an M-plane area of 1.56 times was obtained.
The results of the second growth step of Example 2 are summarized in Table 2.

(Examples 3 and 4: second growth step)
Since the crystals obtained in the first growth steps C and D have an M-plane growth region / underlying substrate main surface area larger than 1, the main surface area larger than the area of the main surface of the underlying substrate used in the first growing step And a plate-like GaN crystal is prepared by slicing parallel to the M-plane so that the proportion of the M-plane growth region is 50% or more, and this is used as a seed crystal in the same procedure as the first growth step. Crystal growth in the second growth step was performed.
After the crystal growth is completed, a crystal having no visible defects such as voids and cracks is obtained on the surface. Compared with the area of the main surface of the base substrate used in the first growth process, a GaN crystal having a large M-plane growth region is obtained. Obtained.

  From the results of Examples 1 to 8, it can be seen that a Group 13 nitride crystal having a large crystal layer area can be produced efficiently.

  According to the present invention, a Group 13 nitride crystal having a M-plane as a main surface and a large crystal layer area can be efficiently produced. Further, according to the present invention, the production efficiency of the group 13 nitride crystal having the M plane as the main surface can be increased, and the production cost can be suppressed. For this reason, this invention is useful for manufacture of a group 13 nitride crystal, and its industrial applicability is high.

1 Autoclave (pressure-resistant container)
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)
40 Underlying substrate (seed crystal)
41 M-plane of base substrate 51 M-plane of growing crystal lump 61 S-plane of growing crystal lump: {10-1-1} plane 71 S-plane of growing crystal lump: {10-11} plane 81 C-plane of growing crystal lump : {0001} face 53-54 M face included in side face of group 13 nitride crystal lump 63-64 Included in side face of group 13 nitride crystal lump, on main face of crystal lump on −c axis side S (10-1-1) plane that does not contact 71-72 S (10-11) plane that is included in the side surface of the Group 13 nitride crystal block and contacts the main surface of the Group 13 nitride crystal block 73-76 S (10-11) plane included in side surface of group 13 nitride crystal lump and not in contact with main surface of group 13 nitride crystal lump on the + c-axis side 100 Periodic table group 13 metal nitride semiconductor crystal lump A Slice line

Claims (8)

On a base substrate made of a group 13 metal nitride semiconductor of the periodic table and having an M plane as a main surface, fluorine and at least the M plane, {10-11} plane and {10-1-1} plane as growth planes A periodic table group 13 metal nitride characterized by including a first growth step of growing a first periodic table group 13 metal nitride crystal layer by an ammonothermal method using a mineralizer containing iodine. Manufacturing method of semiconductor crystal. The manufacturing method according to claim 1 , wherein the base substrate is made of a GaN crystal, and the first periodic table Group 13 metal nitride crystal layer is a GaN layer. Further, a plate-like crystal having a major surface with an M-plane larger than the major surface of the base substrate is obtained from the first periodic table Group 13 metal nitride crystal layer grown in the first growth step. The manufacturing method of Claim 1 or 2 including a plate-shaped crystal production process. The plate-like crystal includes an M-plane growth region made of a periodic table group 13 metal nitride crystal grown in the m-axis direction,
The manufacturing method according to claim 3 , wherein a ratio of an area occupied by the M-plane growth region in the main surface of the plate crystal is 50% or more. The manufacturing method according to claim 4 , wherein an area of the M-plane growth region that appears on the main surface of the plate crystal is larger than an area of the main surface of the base substrate. Further, a second periodic table group 13 metal nitride crystal layer is grown on the plate crystal obtained in the plate crystal production step by an ammonothermal method using at least the M plane and the semipolar plane as growth planes. The manufacturing method according to any one of claims 3 to 5 , further comprising a second growth step. In the second growth step, the first growth step is performed by an ammonothermal method using a mineralizer containing fluorine and iodine with at least the M plane, the {10-11} plane, and the {10-1-1} plane as the growth plane. The manufacturing method according to claim 6 , wherein two periodic table group 13 metal nitride crystal layers are grown. The manufacturing method according to claim 6 or 7 , wherein the plate-like crystal is a GaN crystal, and the second periodic table group 13 metal nitride crystal layer is a GaN layer.

Images