JP2014047097A - Manufacturing method for nitride semiconductor crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an excellent nitride crystal while preventing the deposition of a polycrystalline substance in the case where a non-polar surface or a semi-polar surface is a growing principal surface.SOLUTION: In the method, a nitride semiconductor crystal is made to grow on a seed crystal 110, in which a non-polar surface or a semi-polar surface is a principal surface. The seed crystal 110 is attached through an underlay substrate 109 to a susceptor 107. The outer edge of the lower substrate 109 is arranged on the inner side than the outer edges of the seed crystal 110 and the susceptor 107. The distance R between the seed crystal 110 and the susceptor 107 is 1 to 9 mm.

Description

  The present invention relates to a method for manufacturing a nitride semiconductor crystal. More specifically, the present invention relates to a method for forming a nitride semiconductor crystal on a seed crystal having a nonpolar plane or a semipolar plane as a main plane, wherein a polycrystalline body adheres to the periphery of a laminated substrate and chucking occurs. The present invention relates to a method for manufacturing a nitride semiconductor crystal that suppresses occurrence of the above.

As a method for growing a nitride semiconductor crystal, various manufacturing methods such as a vapor phase method and a liquid phase method are known. Among these, the hydride vapor phase epitaxy (HVPE method) is suitably used as a method for obtaining a semiconductor crystal because of its high growth rate.
When it is desired to manufacture a gallium nitride (GaN) semiconductor wafer as a nitride semiconductor crystal, for example, a substrate such as sapphire or GaN is placed in the growth chamber of the vapor phase growth apparatus and contains a gallium compound in the growth chamber. By supplying a gas and a gas containing a nitrogen compound, a gallium nitride semiconductor crystal is grown on the substrate to a thickness of several μm to several cm.

  Patent Document 1 discloses a method for manufacturing a nitride semiconductor crystal in which the growth of a polycrystalline body is suppressed. Here, in the case where a semiconductor crystal is grown on a seed crystal whose main surface is the C-plane which is a polar surface, the polycrystalline body is grown by exposing a part of the back surface of the seed crystal. Can be suppressed. Thereby, it is said that the grown nitride semiconductor crystal can be easily taken out.

  However, when the C-plane is the growth main surface, there is a problem that the dislocation density of the nitride semiconductor crystal is high and crystal defects are generated. In addition, when the C-plane is used as a growth principal surface as a semiconductor device wafer, a polarization electric field is generated, which causes a problem that luminous efficiency is deteriorated when used for a light-emitting device. Therefore, in Patent Document 2, it is proposed to manufacture a semiconductor crystal having an M plane as a growth main surface in order to obtain a wafer having an M plane which is a nonpolar plane as a main surface.

  In general, it is difficult to obtain a wafer having a large area of the M-plane from which crystal growth is performed using the C-plane as the growth principal plane. Therefore, Patent Document 2 discloses a method for growing a crystal having an M plane as a growth main surface, in which a nitride semiconductor bar is cut out from a primary wafer formed with a C plane as a growth plane so that the M plane becomes an upper surface. A method for re-growing a nitride semiconductor on the substrate is disclosed. In Patent Document 2, the crystal is grown to such a thickness that the crystallinity can be maintained satisfactorily.

JP 2009-46377 A JP 2006-315947 A

  However, it has been found that when a crystal is grown over a long period of time by the method disclosed in Patent Document 2, a hard polycrystalline body with few voids around the base substrate is generated. A hard polycrystalline body with few voids becomes a problem because even a small amount causes cracking of the grown crystal.

  Further, the inventors have confirmed that when a crystal is grown with a nonpolar plane or a semipolar plane as a main plane, the growth rate of the crystal is slower than when a polar plane is grown. It was. For this reason, in order to obtain a crystal having a certain film thickness, it is necessary to grow the crystal for a longer time than the growth with the conventional polar plane as the main surface. However, when a crystal is grown for a long time with a nonpolar plane or a semipolar plane as a main plane, a polycrystalline body is deposited around the laminated substrate, and the grown crystal is cracked or taken out. It has been found that the problem of being unable to do so becomes significant.

  In addition, it has been found that when a nitride semiconductor crystal is grown for a long time, a polycrystalline body grows concomitantly and the polycrystalline body chucks the semiconductor crystal, seed crystal, and susceptor. When chucking occurs, it becomes a problem because the grown semiconductor crystal cannot be taken out from the seed crystal. In addition, since chucking occurs during crystal growth at a high temperature, there is a problem that the semiconductor crystal is cracked due to a difference in thermal expansion coefficient from the susceptor or the like during cooling after crystal growth, and a crack is generated.

  Therefore, in order to solve the problems of the prior art, the present inventors have deposited a polycrystalline body even when thick film growth is performed using a nonpolar plane or a semipolar plane as a growth principal plane. Studies were conducted with the aim of providing a manufacturing method that is difficult to cause chucking.

  As a result of diligent studies to solve the above problems, the inventors of the present application have suppressed the deposition of polycrystals by providing an underlay support that satisfies specific conditions between the base substrate and the susceptor. I found out that I can do it. Specifically, the present invention has the following configuration.

[1] A method for growing a nitride semiconductor crystal on a seed crystal having a nonpolar plane or a semipolar plane as a principal plane, the seed crystal being attached to a susceptor via an underlay support, A method for producing a nitride semiconductor crystal, wherein an outer edge of the support is arranged on an inner side than outer edges of the seed crystal and the susceptor, and a distance between the seed crystal and the susceptor is 1 to 9 mm.
[2] The method for producing a nitride semiconductor crystal according to [1], wherein the shortest distance between the outer edge of the seed crystal and the outer edge of the underlay support is 0.1 to 30 mm.
[3] The method for producing a nitride semiconductor crystal according to [1] or [2], wherein the shortest distance between the outer edge of the susceptor and the outer edge of the underlay support is 1 to 40 mm.
[4] The ratio of the shortest distance between the outer edge of the seed crystal and the outer edge of the underlay support and the distance between the base substrate and the susceptor is 3: 1 to 1:10. The manufacturing method of the nitride semiconductor crystal in any one.
[5] Any of [1] to [4], wherein the ratio of the shortest distance between the outer edge of the susceptor and the outer edge of the underlay support and the distance between the seed crystal and the susceptor is 3: 1 to 1:20. A method for producing a nitride semiconductor crystal according to claim 1.
[6] The method for producing a nitride semiconductor crystal according to any one of [1] to [5], wherein an outer edge of the seed crystal is disposed inside an outer edge of the susceptor.
[7] The method for producing a nitride semiconductor crystal according to any one of [1] to [6], wherein the seed crystal is a hexagonal crystal having an M plane as a main surface.
[8] The method for producing a nitride semiconductor crystal according to any one of [1] to [7], wherein the nitride semiconductor crystal has a thickness of 2 mm or more.
[9] The structure has a structure in which a susceptor, an underlay support, a seed crystal having a nonpolar or semipolar surface as a main surface, and a nitride semiconductor crystal are stacked in order, and A nitride semiconductor crystal-containing laminate, which is disposed inside an outer edge of a crystal and the susceptor, and a distance between the base substrate and the susceptor is 1 to 9 mm.

  According to the present invention, a seed crystal having a nonpolar plane or a semipolar plane as a main growth surface is used, and an underlaying support that satisfies a specific condition is provided between the seed crystal and the susceptor, thereby providing a hard layer around the multilayer substrate. Generation | occurrence | production of a polycrystal can be suppressed. Thereby, the crack of the grown semiconductor crystal can be prevented.

  Furthermore, according to the present invention, even when a small amount of polycrystal is attached around the base substrate, the polycrystal does not grow as a result. Can prevent king. Thereby, the grown semiconductor crystal can be easily taken out, and a high-quality nitride semiconductor crystal free from cracks can be obtained.

FIG. 1 is a schematic cross-sectional view showing the relationship between a seed crystal, an underlay support and a susceptor in a conventional method. FIG. 2 is a schematic sectional view showing the relationship between the seed crystal, the underlay support and the susceptor. FIG. 3 is a diagram showing the relationship between the seed crystal, the underlay support, and the susceptor, and is a schematic view when viewed from the seed crystal side. FIG. 4 is a diagram showing the relationship between the seed crystal, the underlay support, the dummy seed, and the susceptor, and is a schematic view when viewed from the seed crystal side. FIG. 5 is a schematic cross-sectional view of an HVPE apparatus suitably used for crystal growth according to 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.

In the present invention, the + C plane refers to the (0001) plane in hexagonal crystal, and the −C plane refers to the (000-1) plane, which are collectively referred to as the C plane or [0001] plane. In the present invention, since the M plane is a crystal plane perpendicular to the C plane, the normal line of the M plane is orthogonal to the polarization direction. For this reason, the M plane is a nonpolar plane having no polarity. The M plane is indicated by six types of plane orientations ((1-100), (10-10), (01-10), (-1100), (-1010), (0-110)). Since the plane orientations of these are geometrically equivalent plane orientations, these are collectively referred to as {1-100}.
The A plane is a nonpolar plane like the M plane, and refers to a (11-20) plane in hexagonal crystal and a plane equivalent thereto. The normal directions of the + C plane, the −C plane, the M plane, and the A plane are referred to as + c axis, −c axis, m axis, and a axis directions.
Specific examples of the semipolar plane include [10-1-3] plane, [10-1-1] plane, [11-2-2], [20-2-1], [30-3-1]. Surface, [10-13] surface, [10-11] surface, [11-22], [20-21] surface, [30-31] surface, and the like.
The seed crystal used in the present invention has a hexagonal crystal structure having a nonpolar plane such as M plane or A plane or a semipolar plane as a main growth plane.

  In the present invention, a polycrystal means a crystal that cannot form a crystal lattice of a certain crystal system (for example, a hexagonal system) and has no atoms at appropriate positions. That is, it refers to a collection of minute crystals with disordered crystal orientation, meaning a collection of very small single crystal grains. When such a polycrystalline body is chucked, the nitride semiconductor crystal obtained must be taken out after performing the process of removing the polycrystalline body, which makes the process complicated, and time and cost are reduced. Take it. Further, since chucking occurs during crystal growth, the biggest problem is that the nitride semiconductor crystal breaks due to a difference in thermal expansion coefficient from the susceptor or the like during cooling.

  In the present invention, chucking means that a polycrystalline body generated in a growth process continuously grows over two or more members of a seed crystal, an underlay support or a susceptor, and these members are fixed. Means that. When chucking occurs, it becomes very difficult to remove the polycrystal. Chucking also causes damage to members in the container such as the underlay support and susceptor.

FIG. 1 schematically shows the periphery of a multilayer substrate in a conventional method, and shows an example in which a polycrystalline body is connected to the periphery of the multilayer substrate and chucked. In FIG. 1, the seed crystal is attached to the susceptor via an underlay support. In FIG. 1 (a), the outer edge of the base support is disposed outside the outer edge of the seed crystal and the susceptor, and in FIG. 1 (b), the outer edge of the base support is disposed outside the outer edge of the susceptor. ing. As described above, when the outer edge of the underlay support is disposed outside the outer edge of the seed crystal or the susceptor, the polycrystalline body is deposited on the laminated substrate, and chucking occurs.
On the other hand, in FIG. 1 (c), the outer edge of the underlay support is arranged inside the outer edges of the seed crystal and the susceptor. Happens. In the present invention, a layer structure including a seed crystal, an underlay support or a susceptor is referred to as a laminated substrate, and the polycrystalline body is indicated by P in FIG.

The present invention relates to a method for growing a nitride semiconductor crystal on a seed crystal whose main surface is a nonpolar plane or a semipolar plane, and relates to a manufacturing method in which the occurrence of chucking is suppressed. In the present invention, the seed crystal is attached to the susceptor via an underlay support. The outer edge of the underlay support is disposed inside the outer edges of the seed crystal and the susceptor, and each member is disposed such that the distance between the base substrate and the susceptor is 1 to 9 mm.
Thereby, it can suppress that a polycrystal grows over two or more members among a seed crystal, an underlay support body, and a susceptor. In particular, it is possible to suppress the growth of the polycrystalline body so as to cover the side surface of the underlay support, and it is possible to prevent the occurrence of chucking.

(Seed crystal)
In the method for producing a nitride semiconductor crystal of the present invention, a seed crystal having a main surface and a back surface thereof is used. Examples of the seed crystal include sapphire, SiC, ZnO, and a periodic table group 13 metal nitride semiconductor. As the seed crystal, a nitride semiconductor of the same type as or different from the nitride semiconductor to be manufactured can be used. Among them, it is preferable to use a nitride semiconductor containing at least the Group 13 metal element of the same type as the Group 13 metal element of the periodic table constituting the nitride semiconductor to be manufactured. More preferably, the same type of nitride semiconductor seed crystal is used. From another point of view, a seed crystal having a lattice constant close to that of the nitride semiconductor crystal to be manufactured and having a small difference in thermal expansion coefficient may be selected.

  The main surface of the seed crystal here refers to the surface having the largest area among the surfaces constituting the seed crystal. When there are a plurality of surfaces having the largest area, one of them is the main surface, and the back surface is the back surface. In the manufacturing method of the present invention, the main surface is disposed so as to face the source of the source gas for growing the nitride semiconductor crystal, and serves as a surface that receives the source gas.

In the present invention, the principal plane of the hexagonal seed crystal is a nonpolar plane or a semipolar plane. Thereby, a crystal body in which the dislocation density of the nitride semiconductor crystal is low and crystal defects are not easily generated can be obtained. In addition, it is preferable that the main surface of the seed crystal is a nonpolar plane or a semipolar plane when a nitride semiconductor is grown using a dopant such as S.
In the present invention, it is particularly preferable to use the M-plane which is a nonpolar plane as the seed crystal growth main surface. When the M plane is the growth main surface, a semiconductor crystal that is flatter and has few crystal defects can be obtained.

  Each surface such as a nonpolar surface or a semipolar surface constituting the seed crystal may have an off angle. The off angle is preferably within ± 10 ° from the low index surface, and more preferably within ± 8 °. Moreover, the crystal growth direction specified in the present invention may be inclined from the main surface of the seed crystal. The inclination angle is preferably within ± 25 °, more preferably within ± 10 °, and even more preferably within ± 5 °.

Area of the seed crystal for growing a nitride semiconductor crystal is preferably 1 cm ² or more, more preferably 2 cm ² or more, more preferably 5 cm ² or more. A seed crystal having such a plane can be obtained by forming a nitride semiconductor crystal mass having a C plane and then cutting out such that a nonpolar plane M plane, A plane or semipolar plane appears. . Cutting methods include scissors, grinders, inner-blade slicers, wire saws (grinding, cutting), polishing by polishing, and splitting by cleavage. The M-plane, A-plane or semipolar plane is preferably formed by a method of cutting, polishing) and a method of polishing by polishing. A cut crystal or a single crystal may be used as a seed crystal, or may be arranged in a tile shape so that a nonpolar plane or a semipolar plane of a plurality of crystals is a main plane, and may be an integrated seed crystal.

  The thickness of the seed crystal (distance between the main surface and the back surface) used in the method for producing a nitride semiconductor crystal of the present invention is usually 100 μm or more, preferably 200 μm or more, and more preferably 300 μm or more. . Further, the thickness of the seed crystal is usually 2000 μm or less, preferably 1000 μm or less, and more preferably 800 μm or less.

  In the method for producing a nitride semiconductor crystal of the present invention, one seed crystal or a plurality of seed crystals may be installed on the underlying support. When a plurality of seed crystals are provided, the sizes and shapes may be different from each other, but it is preferable that the sizes and shapes are uniform. In addition, when installing a plurality of seed crystals, it is preferable to install them apart from each other so as not to interfere with the nitride semiconductor crystals. Usually, it is preferable to leave 3 mm or more between adjacent seed crystals, more preferably 5 mm or more.

(Underlay support)
The underlay support is a member that is installed between the seed crystal and the susceptor and supports the seed crystal. The underlay support is placed in contact with the back surface of the seed crystal and the main surface of the susceptor. The shape of the underlay support is not particularly limited as long as the seed crystal can be placed and supported, but a structure that can stably mount the seed crystal is preferable. For example, the shape may be a circle or a rectangle, and a rectangle is preferable. Moreover, it is preferable that the underlay support has a flat seed crystal mounting surface in order to stably mount the seed crystal.

  Examples of the material for the underlay support include quartz, SiC-coated carbon, and pyrolytic graphite. Of these, quartz and pyrolytic graphite are preferably used. It is preferable to use an underlay support having excellent heat resistance, ammonia resistance, and hydrogen chloride resistance.

The thickness of the underlay support is preferably 1 mm to 9 mm. The height of the underlay support is preferably 1 mm or more, more preferably 1.5 mm or more, further preferably 2 mm or more, and particularly preferably 3 mm or more. Further, the height of the base support is preferably 9 mm or less, more preferably 8 mm or less, further preferably 7 mm or less, and particularly preferably 6 mm or less.
In addition, the thickness of an underlay support body shows the distance between a seed crystal and a susceptor. The distance between the seed crystal and the susceptor is preferably constant, and the underlay support preferably has a constant thickness.

  The outer edge of the underlay support is smaller than the outer edges of the seed crystal and the susceptor, and the outer edge of the underlay support is disposed inside the outer edges of the seed crystal and the susceptor. The outer edge of the underlay support is located inside the outer edges of both the seed crystal and the susceptor. Further, the outer periphery of the underlay support is disposed entirely inside the outer edges of the seed crystal and the susceptor, and a part of the outer edge of the underlay support is not exposed to the outside of the outer edges of the seed crystal and the susceptor.

  The outer shape of the underlay support can be circular or square, and the outer shape is not particularly limited. Moreover, one seed crystal may be mounted on one underlay support body, and one seed crystal may be mounted on a plurality of underlay support bodies. When one seed crystal is mounted on a plurality of base supports, it is preferable to devise the arrangement of the base supports so that the seed crystals can be stably supported. For example, two or more rod-shaped underlaying supports can be arranged under the seed crystal, and can be arranged at intervals according to the size and shape of the seed crystal.

(Susceptor)
The susceptor is a member for placing an underlay support on which a seed crystal is mounted. The material of the susceptor is not particularly limited, and for example, silicon carbide (SiC), carbon, carbon coated with pBN, pyrolytic graphite, and the like can be appropriately selected. Nitride semiconductor crystals are preferably not deposited on the susceptor, and the susceptor is preferably made of a material that is difficult for the nitride semiconductor crystals to adhere to.

The shape of the susceptor is not particularly limited as long as the underlay support can be installed and supported, but a structure that can stably place the underlay support is preferable. For example, a circular shape or a quadrangular shape can be used, and a circular shape is particularly preferable. Moreover, it is preferable that a susceptor has a mounting surface of an underlay support body on a plane. Moreover, it is preferable that the structure has no structure on the upstream side of the growing crystal when the crystal is grown. If there is a structure that can grow a crystal upstream, the polycrystal will adhere to it and the flow of the raw material gas will change, which will adversely affect the crystal to be grown. Because.
The susceptor preferably has a rotation mechanism in the growth chamber in order to grow the nitride semiconductor crystal in a uniform state on the seed crystal.

(Relationship between seed crystal, underlay support and susceptor)
As shown in FIG. 2, in the method for producing a nitride semiconductor crystal of the present invention, the seed crystal 110 is attached to the susceptor 107 via an underlay support 109. The seed crystal 110 is placed so that the back surface of the seed crystal 110 is in contact with the main surface of the underlying support 109, and a nitride semiconductor crystal grows on the main surface of the seed crystal 110.
The outer edge of the base support 109 is smaller than the outer edges of the seed crystal 110 and the susceptor 107, and the outer edge of the base support 109 is arranged to be inside the outer edges of the seed crystal 110 and the susceptor 107. As a result, the entire circumference of the outer edge of the underlay support 109 enters the inside of the outer edges of the seed crystal 110 and the susceptor 107. That is, when viewed from the main surface side of the seed crystal 110, the underlay support 109 is hidden by the seed crystal 110. Further, when viewed from the back side of the susceptor 107, the underlay support 109 is hidden by the susceptor 107.

  In FIG. 2, the distance between the seed crystal and the susceptor is indicated by R. In the present invention, R is 1 mm to 9 mm. R is 1 mm or more, preferably 1.5 mm or more, more preferably 2 mm or more, and further preferably 3 mm or more. R is 9 mm or less, preferably 8 mm or less, more preferably 7 mm or less, and preferably 6 mm or less. By setting R within the above range, it is possible to prevent the polycrystalline body from growing on the laminated substrate and causing chucking.

  As described above, the outer edge of the underlay support is smaller than the outer edge of the seed crystal, and the outer edge of the underlay support is arranged to be inside the outer edge of the seed crystal. In this invention, it is preferable that the shortest distance between the outer edge of a seed crystal and the outer edge of an underlay support body is 0.1-30 mm. The shortest distance between the outer edge of the seed crystal and the outer edge of the base support means the distance between the points where the distance between the outer edge of the seed crystal and the outer edge of the base support is closest.

  FIG. 3 is a schematic diagram of the seed crystal, the underlay support, and the susceptor viewed from the main surface side of the seed crystal. In FIG. 3, the shortest distance between the outer edge of the seed crystal and the outer edge of the underlay support is indicated by S. S is preferably 0.1 mm or more, more preferably 0.5 mm or more, and further preferably 1.0 mm or more. Further, S is preferably 30 mm or less, more preferably 25 mm or less, and further preferably 20 mm or less.

  As shown in FIG. 3, the outer edge of the underlay support is entirely inside the outer edge of the seed crystal. The distance between the outer edge of the seed crystal and the outer edge of the underlay support is preferably 0.1 mm or more, more preferably 0.5 mm or more, and 1.0 mm or more over the entire circumference. More preferably. Further, the distance between the outer edge of the seed crystal and the outer edge of the underlay support is preferably 40 mm or less, more preferably 30 mm or less, and even more preferably 25 mm or less over the entire circumference. .

  Further, the outer edge of the underlay support is smaller than the outer edge of the susceptor, and the outer edge of the underlay support is arranged to be inside the outer edge of the susceptor. In the present invention, the shortest distance between the outer edge of the susceptor and the outer edge of the underlay support is preferably 1 to 40 mm. The shortest distance between the outer edge of the susceptor and the outer edge of the underlay support means the distance between the points where the distance between the outer edge of the susceptor and the outer edge of the underlay support is closest.

  In FIG. 3, the shortest distance between the outer edge of the susceptor and the outer edge of the underlay support is indicated by T. T is preferably 1 mm or more, more preferably 2 mm or more, and further preferably 3 mm or more. Further, T is preferably 40 mm or less, more preferably 30 mm or less, and further preferably 20 mm or less.

  As shown in FIG. 3, the outer edge of the underlay support body is entirely inside the outer edge of the susceptor. The distance between the outer edge of the susceptor and the outer edge of the underlying support is preferably 1 mm or more, more preferably 2 mm or more, and further preferably 3 mm or more over the entire circumference. Further, the distance between the outer edge of the susceptor and the outer edge of the underlying support is preferably 50 mm or less, more preferably 40 mm or less, and even more preferably 30 mm or less over the entire circumference.

  The entire circumference of the outer edge of the underlay support is arranged so as to be inside the outer edges of the seed crystal and the susceptor, and the distance R between the seed crystal and the susceptor is set to 1 mm to 9 mm so as to straddle each member of the multilayer substrate. Thus, the formation of a polycrystal can be suppressed. This is presumably because a space is formed between the seed crystal and the susceptor where the gas raw material for forming the nitride semiconductor crystal is difficult to enter. By generating a space in which the gas raw material is difficult to enter, it is possible to prevent the polycrystalline body from growing and chucking so as to connect the seed crystal and the susceptor.

  The ratio of S, which indicates the shortest distance between the outer edge of the seed crystal and the outer edge of the underlay support, and R, which indicates the distance between the base substrate and the susceptor, is preferably 3: 1 to 1:10. : 8 is more preferable, and 1: 1 to 1: 5 is more preferable. By setting the ratio of S and R within the above range, it is possible to create a space in which the gas raw material is more difficult to enter and to prevent the occurrence of chucking.

  The ratio of T indicating the shortest distance between the outer edge of the susceptor and the outer edge of the underlying support and R indicating the distance between the base substrate and the susceptor is preferably 3: 1 to 1:20, and 2: 1 to 1: 15 is more preferable, and 1: 1 to 1:10 is even more preferable. By setting the ratio of T and R within the above range, it is possible to create a space in which the gas raw material is more difficult to enter and to prevent the occurrence of chucking.

Furthermore, it is preferable that the outer edge of the seed crystal is disposed inside the outer edge of the susceptor. As shown in FIG. 3, the outer edge of the seed crystal is preferably disposed inside the outer edge of the susceptor without protruding. In FIG. 3, U represents the shortest distance between the outer edge of the seed crystal and the outer edge of the susceptor. When the seed crystal has a quadrangular shape and the susceptor has a circular shape, U indicates the shortest distance from the point indicating the square to the circumference of the susceptor. U is preferably 0.1 mm or more, more preferably 0.5 mm or more, further preferably 1.0 mm or more, preferably 25 mm or less, and more preferably 20 mm or less. More preferably, it is 15 mm or less.
By disposing the outer edge of the seed crystal on the inner side of the outer edge of the susceptor, it is possible to prevent the source gas from flowing around the back side of the seed crystal and to prevent chucking.

(Dummy seed)
As shown in FIG. 4, in the present invention, a dummy seed 111 may be installed on the susceptor 107. The dummy seed 111 is placed on the susceptor 107 and in a peripheral region outside the outer edge of the seed crystal 110. The dummy seed 111 preferably has an overlapping region that overlaps a part of the seed crystal 110 when viewed from the main surface side of the seed crystal 110. On the other hand, when the dummy seed 111 is arranged outside the outer edge of the seed crystal 110 so as not to overlap the seed crystal 110 when viewed from the main surface side of the seed crystal 110, the dummy seed 111 is interposed between the dummy seed and the susceptor. Alternatively, an underlay support may be used.
The dummy seeds 111 may be formed from a plurality of pieces. For example, 4 to 16 dummy seeds 111 may be installed on the susceptor 107.

  The dummy seed 111 has a property of taking in a gas raw material for forming a nitride semiconductor crystal. For this reason, by installing the dummy seed 111 on the susceptor 107, it is possible to prevent the gas raw material for forming the nitride semiconductor crystal from reaching the side surface of the underlying support 109. That is, the dummy seed 111 functions to prevent a gas material for forming a nitride semiconductor crystal from entering the space between the seed crystal 110 and the susceptor 107. That is, since the source gas that can enter the space between the seed crystal 110 and the susceptor 107 is used for single crystal growth on the dummy seed 111, a small amount of source gas enters the space between the seed crystal 110 and the susceptor 107. Even if it is possible, it can be effectively prevented from reaching the side surface of the underlay support 109 and becoming polycrystalline, and the occurrence of chucking can be effectively suppressed.

When the dummy seed 111 is installed on the susceptor 107, the distance between the surface of the dummy seed 111 and the surface of the seed crystal 110 is preferably 1 mm or more, more preferably 1.5 mm or more, and 2 mm or more. More preferably it is. Further, the distance between the dummy seed 111 and the seed crystal 110 is preferably 9 mm or less, more preferably 8 mm or less, and further preferably 7 mm or less. Even when the dummy seed 111 is provided, it is preferable that the distance between the seed crystal 110 and the dummy seed 111 is within the above range. Thereby, it is possible to prevent the polycrystalline body from growing on the laminated substrate and causing chucking.
In addition, it is preferable that the thickness of the dummy seed 111 is 500 nm-1000 micrometers.

(Nitride semiconductor crystal growth process)
Next, the growth process of the nitride semiconductor crystal will be described.
The nitride semiconductor crystal to be grown is preferably a nitride semiconductor crystal containing a Group 13 metal element of the periodic table, more preferably a gallium-containing nitride semiconductor crystal, and Al _1-x Ga _x N (0 ≦ A nitride semiconductor crystal satisfying x ≦ 1) is more preferable, and a gallium nitride semiconductor crystal is particularly preferable.
Examples of the crystal growth method that can be used here include HVPE method, MOCVD method, MBE method, and sublimation method. The HVPE method and the MOCVD method are preferable, and the HVPE method is most preferable.

  Details of the apparatus used for crystal growth are not particularly limited. For example, an HVPE apparatus as shown in FIG. 5 can be used. The HVPE apparatus of FIG. 5 includes a susceptor 107 for placing a seed crystal 110 and an underlay support 109 on which the seed crystal 110 is mounted in a reactor 100, and a reservoir 113 for storing a nitride semiconductor material to be grown. I have. In addition, introduction pipes 101 to 105 for introducing gas into the reactor 100 and an exhaust pipe 108 for exhausting are installed. Further, a heater 106 for heating the reactor 100 from the side surface is installed.

As a material of the reactor 100, quartz, polycrystalline BN, stainless steel or the like is used. A preferred material is quartz. The reactor 100 is filled with atmospheric gas in advance before starting the reaction. Examples of the atmospheric gas include H ₂ gas, N ₂ gas, inert gas such as He, Ne, and Ar. These gases may be mixed and used.

  When the seed crystal 110 is placed on the susceptor 107, the main surface of the seed crystal 110 for crystal growth is placed so as to face the upstream side of the gas flow (above the reactor in FIG. 5). That is, it is more preferable that the gas is placed so as to flow toward the main surface, and the gas flows from the direction perpendicular to the main surface toward the main surface.

  The reservoir 113 is filled with a nitride semiconductor material to be grown. For example, in the case where a nitride semiconductor crystal is grown by reacting Group 13 of the periodic table with a nitrogen source, a source serving as a Group 13 source of the periodic table is added. Examples of the raw material that becomes the group 13 source of the periodic table include Ga, Al, and In.

A gas that reacts with the raw material put in the reservoir 113 is supplied from an introduction pipe 103 for introducing the gas into the reservoir 113. For example, when a raw material that is a Group 13 source of the periodic table is put in the reservoir 113, HCl gas can be supplied from the introduction pipe 103. At this time, the carrier gas may be supplied from the introduction pipe 103 together with the HCl gas. Examples of the carrier gas include H ₂ gas, N ₂ gas, inert gas such as He, Ne, and Ar. These gases may be mixed and used. The carrier gas may be the same as or different from the atmospheric gas, but is preferably the same.

A carrier gas is supplied from the introduction pipes 101 and 102. At this time, a material containing a dopant such as silicon atom or sulfur atom may be supplied from the introduction tube 102. Examples of the carrier gas supplied from the introduction pipes 101 and 102 are the same as the carrier gas supplied from the introduction pipe 103. For example, N ₂ gas can be supplied from the introduction pipe 101 and H ₂ gas can be supplied from the introduction pipe 102. The carrier gas supplied from the introduction pipe 101 or 102 and the carrier gas supplied from the introduction pipe 103 are preferably the same.
From the introduction pipe 104, a source gas serving as a nitrogen source is supplied. Normally, NH ₃ gas is supplied.

  Etching gas can be supplied from the introduction pipe 105 as necessary. As an etching gas, a chlorine-based gas can be used, and HCl gas is preferably used. The etching gas is preferably supplied intermittently (pulsed). Here, “intermittent” means that the step of supplying an etching gas (supplying step) and the step of not supplying an etching gas (non-supplying step) are repeated alternately. By intermittently supplying the etching gas, vacancies of N atoms are easily formed, and dopants such as S atoms are easily taken in. For this reason, a nitride semiconductor crystal or the like doped with S at a high concentration can be more easily manufactured. In addition, a nitride semiconductor crystal with better crystallinity can be manufactured.

  The flow rate of the etching gas in the supply step is preferably about 0.1% to 3%, more preferably 0.5% to 1.5% with respect to the total flow rate. The gas flow rate can be controlled by a mass flow controller (MFC) or the like, and the individual gas flow rates are preferably always monitored by MFC. The ratio of the time required for the supply step and the time required for the non-supply step is not particularly limited, but it is preferable to set 10 to 80% of the total time for crystal growth of the nitride semiconductor as the supply step, and supply 10 to 60%. It is more preferable to set it as a step, and it is more preferable to set 10 to 50% as a supply step. In addition, the length of one cycle consisting of one supply step and one non-supply step is usually 0.1 to 10 minutes, preferably 0.1 to 5 minutes, and more preferably 1 to 3 minutes. . The length of one cycle may be gradually shortened or lengthened, and may not be changed at all. Preferred is an embodiment in which the length of one cycle is always constant.

  The gases supplied from the introduction pipes 101 to 105 may be exchanged with each other and supplied from another introduction pipe. In addition, the source gas and the carrier gas serving as a nitrogen source may be mixed and supplied from the same introduction pipe. Further, a carrier gas may be mixed from another introduction pipe. These supply modes can be appropriately determined according to the size and shape of the reactor 100, the reactivity of the raw materials, the target crystal growth rate, and the like.

  The gas discharge pipe 108 is generally installed so that it can be discharged from the reactor inner wall on the side opposite to the introduction pipes 101 to 105 for gas introduction. In FIG. 5, a gas discharge pipe 108 is installed on the bottom surface of the reactor located opposite to the top surface of the reactor where the introduction pipes 101 to 105 for gas introduction are installed. When the introduction pipe for introducing gas is installed on the right side of the reactor, the gas discharge pipe is preferably installed on the left side of the reactor. By adopting such an aspect, a gas flow can be stably formed in a certain direction.

For example, when Al _1-x Ga _x N (0 ≦ x ≦ 1) is grown by the HVPE method, crystal growth is usually performed at 900 ° C. to 1070 ° C., preferably at 925 ° C. to 1050 ° C., and 950 ° C. More preferably, it is carried out at -1030 ° C, more preferably 975 ° C-1000 ° C. The pressure in the reactor is preferably 10 kPa to 400 kPa, more preferably 30 kPa to 150 kPa, and even more preferably 50 kPa to 120 kPa. For example, when using GaCl and NH ₃ , the partial pressure of GaCl is preferably 0.03 to 30 kPa, and the partial pressure of NH ₃ is preferably 1 to 300 kPa.

For example, when AlN is grown by the HVPE method, it can be carried out in an atmosphere containing AlCl ₃ and / or AlCl and NH ₃ . The crystal growth temperature is preferably 1050 ° C. to 1250 ° C., the partial pressure of AlCl ₃ and / or AlCl is preferably 3 × 10 ^{1 to} 3 × 10 ⁴ Pa, and the partial pressure of NH ₃ is 1 to 300 kPa. It is preferable that AlCl ₃ and / or AlCl is formed by reacting Al and HCl. AlCl ₃ is mainly produced at a relatively low temperature of about 600 ° C., and AlCl ₃ is formed at a relatively high temperature of about 800 ° C. Mainly generated.

According to the manufacturing method of the present invention, crystal growth of a nitride semiconductor can be performed at a constant rate,
As in the conventional method, it is possible to prevent the polycrystalline body from growing on the laminated substrate and causing chucking. Further, since the occurrence of chucking is suppressed, the crystal obtained by the production method of the present invention is uniform and has a feature of higher quality.

Of the nitride semiconductor crystals obtained after crystal growth, it is preferable to perform a heat treatment in a reducing atmosphere, particularly for nitride semiconductor crystals formed while being doped with S. The heat treatment is performed by placing the nitride semiconductor crystal in an environment of usually 600 to 1070 ° C., preferably 700 to 1000 ° C., more preferably 750 to 950 ° C. Although the time of heat processing is based also on temperature, it is 1 to 30 minutes normally, Preferably it is 1 to 10 minutes, More preferably, it is 1 to 5 minutes. The heat treatment needs to be performed in a reducing atmosphere. The reducing atmosphere here refers to an atmosphere in which the partial pressure of a reducing gas such as hydrogen is 50% or more. For example, an H ₂ atmosphere in an annealing furnace can be used. Thermal conductivity is increased by performing heat treatment in a reducing atmosphere after crystal growth.

(Nitride semiconductor crystal-containing laminate)
The nitride semiconductor crystal-containing laminate according to the present invention has a structure in which a susceptor, an underlay support, a seed crystal having a nonpolar or semipolar surface as a main surface, and a nitride semiconductor crystal are sequentially laminated. In the nitride semiconductor crystal-containing laminate, the outer edge of the underlay support is disposed inside the outer edges of the seed crystal and the susceptor. In the nitride semiconductor crystal-containing laminate, the distance between the base substrate and the susceptor is 1 to 9 mm. The distance between the base substrate and the susceptor is 1 mm or more, preferably 1.5 mm or more, more preferably 2 mm or more, and further preferably 3 mm or more. The distance between the base substrate and the susceptor is 9 mm or less, preferably 8 mm or less, more preferably 7 mm or less, and preferably 6 mm or less.
As described above, by setting the distance between the base substrate and the susceptor within the above range, the nitride semiconductor crystal-containing stacked body enters the gas raw material for forming the nitride semiconductor crystal between the base substrate and the susceptor. Can have difficult space. For this reason, in the nitride semiconductor crystal-containing stacked body, it is suppressed that the polycrystalline body is continuously deposited across two or more members of the susceptor, the underlay support, and the seed crystal.

(Nitride semiconductor crystal)
The crystal system of the nitride semiconductor obtained by the manufacturing method of the present invention is preferably a hexagonal system. The nitride semiconductor crystal obtained is preferably a single crystal.
When the nitride semiconductor crystal is grown from the main surface of the seed crystal in the normal direction of the main surface, the nitride semiconductor crystal is preferably grown until the thickness becomes 2 mm to 10 cm. When performing slicing, grinding, polishing, laser irradiation, etc. after crystal growth, a crystal of a certain size is required. Therefore, the thickness of the nitride semiconductor crystal grown on the seed crystal is preferably 5 mm to 10 cm, 1 cm to 10 cm is more preferable.

  The nitride semiconductor crystal obtained by the production method of the present invention may be used as it is, but usually, only the nitride semiconductor crystal is taken out by using a process such as grinding or slicing. Here, the slice processing means (1) processing for making the quality of the main surface uniform so that the grown crystal can be used as a nitride semiconductor substrate, and (2) stress generated from dislocations inherent in the initial growth portion. In consideration of the fact that there is a possibility, the processing is performed to cut off the portion. In the case of (2), for example, the crystal grown near the surface of the seed crystal is discarded. Specifically, the slicing can be performed using an inner peripheral slicer, a wire source slicer, or the like. By slicing, crystals having substantially the same shape, lower dislocation density, and fewer surface defects can be manufactured.

According to the manufacturing method of the present invention, the nitride semiconductor can be doped.
The case of forming a nitride semiconductor while doping according to the production method of the present invention, it is preferable that O concentration is 1 × 10 ¹⁷ cm ^-3 or more, or, Si concentration is 1 × 10 ¹⁷ cm ^-3 or more Preferably there is.

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

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

Example 1
Gallium nitride (GaN) was grown on the sapphire substrate by metal organic chemical deposition (MOCVD). A GaN template having a C-plane main surface is prepared without adding a dopant, and a Si ₃ N ₄ mask is formed on the template. And a base substrate was prepared.
Next, the base substrate was disposed on the susceptor 107 so that the C-plane-GaN layer of the base substrate was exposed on the upper surface. At this time, the distance between the tip of the gas introduction tube 104 and the base substrate was 9 cm. Thereafter, the temperature of the reaction chamber was raised to 1010 ° C. to grow a GaN single crystal. In this single crystal growth step, the growth pressure is 1.01 × 10 ⁵ Pa, the partial pressure of the GaCl gas G3 is 6.55 × 10 ² Pa, and the partial pressure of the NH ₃ gas G4 is 7.58 × 10 ³ Pa. It was. The growth time was 64 hours.

  After the growth of the single crystal, the temperature was lowered to room temperature to obtain a GaN single crystal. A GaN single crystal having a thickness of 8.3 mm and a C-plane main surface (hereinafter referred to as C-plane-GaN single crystal) was obtained on the base substrate. When the growth rate was calculated from the thickness of the C-plane GaN single crystal and the growth time, it was 130 μm / h.

  From the obtained C-plane-GaN single crystal, the main plane is a plane having an off angle of −2 ° in the [0001] direction and 0 ° in the [-12-10] direction from the (10-10) plane. Then, slicing was performed to obtain a plurality of small piece substrates. From these, a GaN free-standing single crystal having a square of 50 mm long side × 5 mm short side and a thickness of 330 μm was prepared.

  A plurality of GaN free-standing single crystals obtained as described above were prepared, and as shown in Table 1, a rectangular seed crystal having a vertical length of 114 mm, a horizontal length of 114 mm, and a height of 0.3 mm. The tiles were arranged so as to be 110. Vertical length 120mm, horizontal length 120mm. On a susceptor 107 having a height of 20 mm, an underlay support 109 having a vertical length of 110 mm, a horizontal length of 110 mm, and a height of 3 mm was placed, and a seed crystal 110 was placed thereon. The reaction chamber temperature was raised to 850 ° C. and held for 15 minutes.

Thereafter, GaCl which is a Group 13 material and NH ₃ which is a nitrogen material are supplied from the main surface direction, and the temperature is raised to a growth temperature of 950 ° C. (temperature increase rate: 21 ° C./min). Was grown for 50 hours.
In this single crystal growth step, the growth pressure is 1.01 × 10 ⁵ Pa, the partial pressure of the GaCl gas G3 is 3.54 × 10 ² Pa, and the partial pressure of the NH ₃ gas G4 is 1.13 × 10 ⁴ Pa. It was. After completion of the single crystal growth step, the temperature was lowered to room temperature to obtain a GaN crystal. The film thickness in the m-axis direction of the obtained GaN single crystal was about 3 mm.

(Example 2)
As shown in Table 1, a GaN crystal was obtained in the same manner as in Example 1, except that the shapes of the seed crystal 110, the susceptor 107, and the underlay support 109 were changed. As the seed crystal 110, a seed crystal 110 having a vertical length of 60 mm, a horizontal length of 60 mm, and a height of 0.3 mm was used. A susceptor 107 having a diameter of 100 mm and a height of 20 mm was used. As the underlay support 109, a material having a vertical length of 56 mm, a horizontal length of 56 mm, and a height of 3 mm was used. The film thickness in the m-axis direction of the obtained GaN single crystal was about 3 mm.

(Comparative Example 1)
As shown in Table 1, a GaN crystal was obtained in the same manner as in Example 1, except that the shapes of the seed crystal 110, the susceptor 107, and the underlay support 109 were changed. As the seed crystal 110, a seed crystal 110 having a vertical length of 114 mm, a horizontal length of 114 mm, and a height of 0.3 mm was used. A susceptor 107 having a diameter of 100 mm and a height of 20 mm was used. As the underlay support 109, a material having a vertical length of 110 mm, a horizontal length of 110 mm, and a height of 3 mm was used. In Comparative Example 1, the outer edge of the underlay support 109 is larger than the outer edge of the susceptor 107 and is disposed outside. In Table 1, the value of T is expressed as a negative value as the width extending outward. The film thickness in the m-axis direction of the obtained GaN single crystal was about 3 mm.

(Comparative Example 2)
As shown in Table 1, a GaN crystal was obtained in the same manner as in Example 1, except that the shapes of the seed crystal 110, the susceptor 107, and the underlay support 109 were changed. As the seed crystal 110, a seed crystal 110 having a vertical length of 60 mm, a horizontal length of 60 mm, and a height of 0.3 mm was used. A susceptor 107 having a diameter of 75 mm and a height of 20 mm was used. As the underlay support 109, a material having a vertical length of 56 mm, a horizontal length of 56 mm, and a height of 20 mm was used. In Comparative Example 2, the thickness of the underlay support 109 is greater than 9 mm and 20 mm. In addition, a part of the outer edge of the underlay support 109 is larger than the outer edge of the susceptor 107 and is arranged outside. In Table 1, the value of T is expressed as a negative value as the width extending outward. The film thickness in the m-axis direction of the obtained GaN single crystal was about 3 mm.

The dislocation density of the obtained GaN crystal was evaluated by cathodoluminescence (CL) observation in a 3 kV, 100 pA, 1000-fold field in an as-grown state. When dislocations in the crystal were calculated from the dark spot density by CL observation, it was 9.4 × 10 ⁵ cm ⁻² . In all the examples, the dark density was similar.

As shown in Table 1, in Example 1 and Example 2, there was no crack in the grown crystal, and generation of a polycrystal was suppressed around the multilayer substrate. Also, no chucking occurred. The grown crystals obtained were also of very good quality.
On the other hand, in Comparative Example 1 and Comparative Example 2, polycrystals were generated around the multilayer substrate, and chucking occurred. As a result, cracks occurred in the grown crystal, and the crystal was divided.

  According to the present invention, it is possible to prevent the polycrystalline body from growing on the laminated substrate and causing chucking. For this reason, if the manufacturing method of this invention is used, the high quality nitride semiconductor crystal without a crack can be obtained. INDUSTRIAL APPLICABILITY According to the present invention, a semiconductor crystal can be efficiently produced on a seed crystal having a nonpolar plane or a semipolar plane as a main growth surface, and the industrial applicability is high.

100 Reactor 101 H ₂ Carrier Gas Pipe 102 N ₂ Carrier Gas Pipe 103 Periodic Table Group 13 Raw Material Pipe 104 Nitrogen Raw Material Pipe 105 Etching Gas Pipe 106 Heater 107 Susceptor 108 Exhaust Pipe 109 Underlay Support 110 Seed Crystal 111 Dummy seed 113 Periodic table Group 13 source reservoir G1 H ₂ carrier gas G2 N ₂ carrier gas G3 Periodic table Group 13 source gas G4 Nitrogen source gas G5 Etching gas P Polycrystal

Claims (9)

A method for growing a nitride semiconductor crystal on a seed crystal having a nonpolar plane or a semipolar plane as a main plane,
The seed crystal is attached to the susceptor via an underlay support,
The outer edge of the underlay support is disposed inside the outer edge of the seed crystal and the susceptor,
The method for producing a nitride semiconductor crystal, wherein a distance between the seed crystal and the susceptor is 1 to 9 mm.   The method for producing a nitride semiconductor crystal according to claim 1, wherein the shortest distance between the outer edge of the seed crystal and the outer edge of the underlay support is 0.1 to 30 mm.   The method for producing a nitride semiconductor crystal according to claim 1 or 2, wherein a shortest distance between an outer edge of the susceptor and an outer edge of the underlay support is 1 to 40 mm.   The ratio of the shortest distance between the outer edge of the seed crystal and the outer edge of the underlay support and the distance between the base substrate and the susceptor is 3: 1 to 1:10. The manufacturing method of the nitride semiconductor crystal of description.   The ratio of the shortest distance between the outer edge of the susceptor and the outer edge of the underlay support and the distance between the seed crystal and the susceptor is 3: 1 to 1:20. A method for producing a nitride semiconductor crystal.   6. The method for producing a nitride semiconductor crystal according to claim 1, wherein an outer edge of the seed crystal is disposed inside an outer edge of the susceptor.   The method for producing a nitride semiconductor crystal according to claim 1, wherein the seed crystal is a hexagonal crystal having an M plane as a main surface.   The method for producing a nitride semiconductor crystal according to claim 1, wherein the nitride semiconductor crystal has a thickness of 2 mm or more. It has a structure in which a susceptor, an underlay support, a seed crystal having a nonpolar or semipolar surface as a main surface, and a nitride semiconductor crystal are sequentially stacked,
The outer edge of the underlay support is disposed inside the outer edge of the seed crystal and the susceptor,
The nitride semiconductor crystal-containing laminate, wherein the distance between the base substrate and the susceptor is 1 to 9 mm.

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