JP2003037066A - Nitride semiconductor substrate and its growing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nitride semiconductor substrate in which dislocation defect is reduced by growing a nitride semiconductor on a substrate. SOLUTION: A first nitride semiconductor layer is grown on a substrate and a protective film having an opening is grown thereon. A nitride semiconductor nucleus is then grown from the opening and, at the same time, the underlying nitride semiconductor is decomposed thermally. Subsequently, the protective film is removed and a second nitride semiconductor layer is grown using the nitride semiconductor nucleus as the starting point of growth, thus obtaining a nitride semiconductor substrate. The nitride semiconductor nucleus preferably has a reverse trapezoidal cross-section.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a nitride semiconductor (In
_{x Al y Ga 1-x-} y N, 0 ≦ X, 0 ≦ Y, X + Y ≦
The present invention relates to the growth method of 1), and more particularly to a nitride semiconductor substrate that can be used for a light emitting element, a light receiving element, an electronic device, and the like, and a growth method thereof.

[0002]

2. Description of the Related Art In recent years, various studies have been conducted to grow a nitride semiconductor on a heterogeneous substrate different from a nitride semiconductor such as sapphire, spinel or silicon carbide. This is because it is difficult to obtain a bulk single crystal of a nitride semiconductor having good crystallinity that can be used for a light emitting device or the like. Therefore, the nitride semiconductor substrate is formed by growing the nitride semiconductor on a different substrate different from the nitride semiconductor. However, if the lattice constant or the coefficient of thermal expansion is a nitride semiconductor (for example,
Since there is no heterogeneous substrate that matches GaN), growing a nitride semiconductor directly on the heterogeneous substrate causes many dislocation defects in the nitride semiconductor. Therefore, the following method has been reported to solve such a problem.

As a method of reducing dislocation defects as described above, a nitride semiconductor substrate is formed by utilizing lateral growth. JPN. J. App
l. Phys. Vol. 37 (1998) pp. L30
9-L312, a protective film such as SiO ₂ is partially formed on the nitride semiconductor grown on the C surface of sapphire,
It is disclosed that a nitride semiconductor is laterally grown on this protective film at a reduced pressure of 100 Torr to obtain a nitride semiconductor with few dislocation defects. According to this method, the dislocations can be bent in the lateral direction, which is the growth direction of the nitride semiconductor, by laterally growing the nitride semiconductor on the protective film. Furthermore, by continuing the growth of the nitride semiconductors, the nitride semiconductors are bonded to each other on the protective film,
Flatten the surface. As described above, according to this method, the dislocation defects are generated in the range where the protective film is not provided, but the nitride semiconductor substrate having the region where the dislocation defects are reduced can be formed on the protective film.

[0004]

However, in the above-described growth method, although the low dislocation defect region can be formed on the protective film, the nitride semiconductor is laterally grown on the protective film and the nitride is grown. Contamination occurred due to decomposition of the protective film during the growth of the semiconductor element. Further, when a nitride semiconductor is grown on the protective film, stress is generated, and when the laterally grown nitride semiconductors are joined on the protective film, tilt is generated. Therefore, the deterioration of the characteristics of the semiconductor element has become a problem. When forming a nitride semiconductor element used for an electronic device such as an LED element, an LD element, a light receiving element or the like, if a substrate made of a nitride semiconductor with few dislocation defects and good crystallinity can be formed, the nitride semiconductor The crystallinity of the nitride semiconductor device grown on the substrate is dramatically improved.
Therefore, an object of the present invention is to provide a low-dislocation-defect nitride semiconductor substrate having good crystallinity and a method for growing the same, which solves the above problems.

[0005]

The constitution of the present invention, which is a means for achieving the object of the present invention, is shown below. A nitride semiconductor substrate in which a nitride semiconductor layer is grown on a substrate, wherein the nitride semiconductor layer has a first nitride semiconductor layer on the substrate and an opening on the first nitride semiconductor layer. And a second nitride semiconductor layer grown from the nitride semiconductor nucleus, and the first nitride semiconductor layer and the second nitride semiconductor layer have a laminated structure. It is characterized in that it has a cavity or a polycrystalline region on both sides of the nitride semiconductor nucleus which is an interface with the layer. From the above, the first
The interface between the nitride semiconductor layer and the second nitride semiconductor layer of
Except for the nitride semiconductor nucleus, it is a cavity or a polycrystalline region. If this interface is hollow, the first nitride semiconductor layer to the second nitride semiconductor layer
Propagation of dislocation defects that proceed in the vertical direction to the nitride semiconductor layer is suppressed. Therefore, in the second nitride semiconductor layer grown from the adjacent nitride semiconductor nuclei, many dislocation defects exist on the nitride semiconductor nuclei, but dislocation defects from the nitride semiconductor nuclei exist in the laterally grown region. Although dispersed, the number of dislocation defects per unit area can be reduced by two digits or more. Further, by continuing the lateral growth, the second nitride semiconductor layers are joined together. At this time, since the second nitride semiconductor layer is not bonded on the protective film,
It is possible to obtain a nitride semiconductor substrate made of a nitride semiconductor that does not cause tilt and has a flat surface and is a mirror surface. The region where the dislocation defects are reduced is shown in the first region of FIG. In addition, even when the interface between the first nitride semiconductor layer and the second nitride semiconductor layer is a polycrystalline region, the dislocation defect propagates from the first nitride semiconductor layer to the second nitride semiconductor layer. Can be suppressed. This is because the growth rate of the second nitride semiconductor layer grown from this polycrystalline region is slower than that of the second nitride semiconductor layer grown from the nitride semiconductor nucleus. That is, this is because the second nitride semiconductor layers grown from the adjacent nitride semiconductor nuclei are joined by the lateral growth before the second nitride semiconductor layers grow from the polycrystalline region. As a result, a cavity is formed on the polycrystalline region, and the propagation of dislocation defects from below is suppressed. From the above, a nitride semiconductor substrate with reduced dislocation defects can be obtained even when it has a polycrystalline region as in the case where it has a cavity.

Next, the nitride semiconductor nucleus is characterized in that its cross-sectional shape is an inverted trapezoid. This means that the upper surface of the nitride semiconductor nucleus is wider than the lower surface that is the interface with the first nitride semiconductor layer. Therefore, the distance between adjacent nitride semiconductor nuclei becomes short, and the second nitride semiconductor layers grown from the nitride semiconductor nuclei are easily bonded to each other. If the growth interface of the nitride semiconductor nucleus with the first nitride semiconductor layer becomes narrow and the cavity width can be widened, the substrate can be separated at the interface. This is because there are many dislocation defects at the growth interface and the crystallinity is poor, so the interface is peeled off by polishing from the substrate side. Therefore, a single substrate made of a nitride semiconductor or a thin film nitride semiconductor substrate can be formed.

Next, the nitride semiconductor nucleus is characterized in that the planar shape is a stripe shape or a lattice shape. By growing the second nitride semiconductor layer from the growth nucleus having such a shape, it becomes possible to perform lateral growth without a protective film. The nitride semiconductor substrate formed by this growth method is one in which the second nitride semiconductor layer is grown mainly from the upper surface of the nitride semiconductor nucleus having the opening grown on the first nitride semiconductor layer. is there. This growth is
This method utilizes vertical and horizontal growth of a nitride semiconductor, but does not have a protective film when the second nitride semiconductor layer is grown, so that the protective film is decomposed unlike lateral growth on the protective film. By doing so, there is no concern that the crystallinity will deteriorate.

The nitride semiconductor nucleus is not formed by cutting the nitride semiconductor layer by etching such as RIE. For example, the side surface of the nitride semiconductor nucleus is formed by removing the protective film by wet etching using phosphoric acid, sulfuric acid, and hydrofluoric acid. Therefore, the side surface of the nitride semiconductor nucleus in the present invention has no damage due to etching. The second nitride semiconductor layer laterally grown from this nitride semiconductor nucleus has good crystallinity.

A method for growing a nitride semiconductor substrate in which a nitride semiconductor is grown on a substrate by an epitaxial growth method, wherein a first nitride semiconductor layer and a patterned protective film are formed on the substrate. At the same time as the step of forming and forming a nitride semiconductor nucleus from the opening of the protective film,
And a step of thermally decomposing the nitride semiconductor under the protective film, and thereafter removing the protective film and forming a second nitride semiconductor layer using the nitride semiconductor nucleus as a growth starting point. Characterize. The first nitride semiconductor layer is exposed in the opening of the protective film described above, and the nitride semiconductor nucleus is grown using this exposed portion as a growth starting point. During the growth of the nitride semiconductor nucleus, the growth temperature causes the nitride semiconductor under the protective film to be thermally decomposed. The nitride semiconductor in the thermally decomposed region becomes polycrystalline. Further, after removing the protective film, the second nitride semiconductor layer is grown. At this time, since the growth rate from the nitride semiconductor nucleus is higher than the growth rate of the nitride semiconductor from the polycrystalline region, the second nitride semiconductor layer is formed on the polycrystalline regions on both sides of the nitride semiconductor nucleus. After growth, cavities or polycrystalline regions remain.

The method for growing a nitride semiconductor substrate is characterized in that the nitride semiconductor nucleus is grown at a higher temperature than that of the first nitride semiconductor layer. Preferably, the nitride semiconductor nuclei are grown at a temperature higher than the first nitride semiconductor layer by 10 ° C. or higher, preferably 20 ° C. or higher. As a result, the portion under the protective film can be decomposed without reducing the growth rate of the nitride semiconductor. Further, the upper limit is a high temperature until the temperature difference is 50 ° C., preferably 30 ° C. This is because if it exceeds this, the nitride semiconductor is decomposed and the growth rate becomes slow. The growth temperature of the nitride semiconductor nucleus is 700 ° C. or higher.

The method of growing a nitride semiconductor substrate is characterized in that the nitride semiconductor nuclei are formed in a stripe shape, a stripe shape, or a lattice shape.

A method for growing a nitride semiconductor substrate, wherein a nucleus or layer made of a nitride semiconductor is grown as an underlayer on the substrate, and the first nitride semiconductor layer is interposed via the underlayer. It is characterized by growing. By growing this underlayer on the substrate at a low temperature of 700 ° C. or lower, it has an effect as a buffer layer.

ELO (epitaxial lateral overgrowth)
During the growth, stress was generated when the nitride semiconductor was laterally grown on the protective film, and a step was formed at the joint formed by joining the nitride semiconductors. However, in the growth method of the present invention, the nitride semiconductor is not grown laterally by force, but is grown laterally without stress from the nitride semiconductor nucleus. Further, the second nitride semiconductor grows in the vertical direction and the horizontal direction, and the second nitride semiconductors are bonded to each other to form a bonded portion. Therefore, the above problem does not occur, and the surface shape is flat and mirror-finished. can do. In addition, since cavities and polycrystalline regions are formed on both sides of the nitride semiconductor nucleus, propagation of dislocation defects from the first nitride semiconductor layer to the second nitride semiconductor layer can be suppressed. Therefore, it is possible to provide a nitride semiconductor substrate in which dislocation defects are reduced by two digits or more per unit area.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to the drawings. 1 to 5 are schematic views showing stepwise an embodiment of a nitride semiconductor substrate and a growth method thereof according to the present invention.

As an embodiment of the method for growing a nitride semiconductor substrate according to the present invention, first, as shown in FIG. 1, a first nitride semiconductor layer 2 is grown on a substrate 1 and a protective film 3 is formed thereon. To form a film. Next, as shown in FIG.
To form an opening. After that, as shown in FIG. 3, the nitride semiconductor nucleus 4 is grown at a temperature higher than that of the first nitride semiconductor layer 2 through the opening of the protective film 3, and the growth is stopped at a height not exceeding the protective film 3. Next, as shown in FIG. 4, the protective film 3 is removed. Further, as shown in FIG. 5, the second nitride semiconductor layer 5 is grown from the nitride semiconductor nucleus 4, and the second nitride semiconductor layers are bonded to each other to form a nitride semiconductor substrate.

The growth method of this embodiment described above does not grow a nitride semiconductor on the protective film. Therefore, the nitride semiconductor substrate is formed by laterally growing from the nitride semiconductor nucleus without causing stress by forcibly laterally growing on the protective film. Also,
At the interface between the first nitride semiconductor layer 3 and the second nitride semiconductor layer 5, a region other than the nitride semiconductor nucleus 4 has a cavity or a polycrystalline region. Therefore, propagation of dislocation defects from the first nitride semiconductor layer in the vertical direction can be suppressed. The first region shown in FIG. 5 is a region in which dislocation defects are significantly reduced, and the number of dislocations per unit area is 1 × 1.
0 of ⁶ / cm ² or less. Further, the number of dislocations is 1 × 10 ⁸ to 1 ×, since threading dislocations that progress in the vertical direction remain in the second region.
It becomes 10 ¹⁰ pieces / cm ² .

The above steps will be described in more detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view in which a step of growing a first nitride semiconductor layer 2 on a substrate 1 and further forming a protective film 3 is performed. The substrate 1 has a C surface,
Sapphire having an R surface or an A surface as a main surface, an insulating substrate such as spinel (MgAl ₂ O ₄ ), SiC
(6H, 4H, 3C), ZnS, ZnO, GaAs, S
An oxide substrate or the like that has a lattice junction with i and a nitride semiconductor can be used. Alternatively, a nitride semiconductor that is a substrate of the same type can be used.

Further, the first nitride semiconductor 2 may be grown on the substrate 1 via an underlayer (not shown). As the underlayer, AlN, GaN, AlGaN, I
nGaN or the like is used. This underlayer has a growth temperature of 3
The temperature is set to 00 ° C. or more and 900 ° C. or less, preferably 700 ° C. or less, and the film is grown to have a film thickness of 10 angstrom or more and 0.5 μm or less. This is for alleviating the lattice constant mismatch between the substrate 1 and the first nitride semiconductor 2, and is preferable in that it reduces dislocation defects.

Next, as the first nitride semiconductor layer 2 grown on the substrate 1, an undoped nitride semiconductor and S are used.
A nitride semiconductor doped with an n-type impurity such as i, Ge, Sn, and S can be used, and the first nitride semiconductor layer 2 grows on a heterogeneous substrate at a growth temperature of 900 ° C to 1100 ° C. The thickness of the first nitride semiconductor layer 2 is not particularly limited, but is preferably 1.5 μm or more because a mirror surface with few pits can be formed on the surface.

Next, as the protective film 3 formed on the surface of the first nitride semiconductor 2, it is assumed that the nitride semiconductor does not grow or does not grow easily on the surface. By doing so, it is possible to form an opening in the protective film and selectively grow the nitride semiconductor nucleus by using the first nitride semiconductor layer as a growth starting point. Specific examples of this protective film include silicon oxide (SiO _x ), silicon nitride (Si _x N _y ), silicon nitride oxide (SiO _x N _y ), and titanium oxide (Ti).
O _x ), oxides such as zirconium oxide (ZrO _x ), nitrides, multilayer films of these, and metals having a melting point of 1200 ° C. or higher.

As a method for forming the protective film 3, for example, CVD, sputtering, vapor deposition or the like is used. The thickness of the protective film is not particularly limited as long as it has a film thickness capable of forming a nitride semiconductor nucleus to be grown in a later step, but it can be formed in the range of 0.2 to 10 μm.

FIG. 2 is a schematic cross-sectional view in which an opening is formed in the protective film after the first nitride semiconductor layer 2 and the protective film 3 are formed on the substrate 1. By forming an opening in this protective film, the first nitride semiconductor layer is exposed, and a nitride semiconductor nucleus is grown from this exposed portion as a growth starting point.

The protective film 3 may have any planar shape as long as the nitride semiconductor can grow from the opening of the protective film, and may have a stripe shape, a lattice shape, or a stripe shape, a circular shape, or a polygonal shape. Some have. Moreover, a hexagonal shape is mentioned as a concrete pattern shape of the polygonal opening. In addition, the cross-sectional shape of the protective film 3 is a second semiconductor grown from a nitride semiconductor nucleus grown after the protective film is formed.
The nitride semiconductor layer is laterally grown and has a cross-sectional shape that facilitates bonding. Therefore, it is preferable that the cross-sectional shape of the nitride semiconductor nucleus has a wide upper surface. Therefore, the cross-sectional shape of the protective film 3 is trapezoidal.

The size of the opening of the protective film 3 may be any width as long as the second nitride semiconductors can be bonded to each other after the protective film is removed in the subsequent step. For example, when the protective film has a stripe shape, the width of the opening is 1 to
It is 100 μm, preferably 2 to 15 μm. When the width of the opening is 2 to 15 μm, the nitride semiconductor substrate can be thinned. The width of the protective film 3 is 10 to 200 μ
m, preferably 20 to 100 μm. In addition, even if the opening is wide, in the first region shown in FIG. 5, there is almost no growth from below because of the polycrystalline region under the protective film,
Low dislocations can be achieved over a wide range.

If the substrate 1 is a sapphire substrate when the protective film 3 is formed in a stripe shape, the orientation flat surface is the A surface of sapphire and is shifted to the left or right with respect to the vertical axis of the orientation flat surface. You may form. This makes it possible to obtain a flat surface after growing the nitride semiconductor. Specifically, it may be in the range of θ = 0 ° to 5 ° to the left and right with respect to the vertical axis of this orientation flat surface.

Here, the protective film 3 preferably has a trapezoidal sectional view. This is because the cross-sectional shape of the nitride semiconductor nucleus grown from the opening of the protective film in the next step has an inverted trapezoidal shape. For forming the protective film, anisotropic etching such as RIE or ICP, or isotropic etching such as asher can be used. Therefore, it is preferable to use an asher to form a trapezoidal cross section.

Next, as shown in FIG. 3, a protective film 3 having an opening is formed on the first nitride semiconductor 2 in the previous step, and then a nitride semiconductor nucleus 4 is grown from this opening. The width of the opening of the protective film is the bottom width of the nitride semiconductor nucleus, and the width is preferably 2 to 15 μm. Under this condition, if the nitride semiconductor nuclei are formed in an inverted trapezoidal shape, the substrate can be easily peeled off by polishing. The nitride semiconductor nuclei 4 are grown using the exposed surface of the first nitride semiconductor layer as a growth starting point, but the growth is preferably stopped within a range not exceeding the height of the protective film 3. The growth temperature of the nitride semiconductor nucleus 4 is higher than that of the first nitride semiconductor layer 2. Preferably, the growth temperature is raised by 10 ° C. or higher, preferably 10 ° C. or higher. If the first nitride semiconductor layer is grown under the growth conditions of the underlayer, the growth temperature of the nitride semiconductor nucleus is 700.
C. or higher, preferably 710.degree. C. or higher. The first nitride semiconductor 2

When grown under the conditions shown in (1), the growth temperature of the nitride semiconductor nuclei is 960 ° C to 1150 ° C. By growing the nitride semiconductor nuclei at a higher growth temperature than the growth temperature of the first nitride semiconductor layer, the nitride semiconductor under the protective film 3 is thermally decomposed and polycrystallized. You can

Next, as shown in FIG. 4, after forming the nitride semiconductor nucleus 4, the protective film 3 is removed. As a method for removing this protective film, dry etching, wet etching, or the like is used. The surface of the first nitride semiconductor layer, which becomes an exposed surface after removing the protective film 3, becomes a polycrystalline region. By removing this protective film, SiO in ELO etc.
There is no problem of decomposition and diffusion of SiO ₂ when the nitride semiconductor is laterally grown on the protective film such as ₂ . Problems such as abnormal growth of the nitride semiconductor and deterioration of crystallinity that occur due to this can be suppressed.

Further, as shown in FIG. 5, the second nitride semiconductor layer 5 is grown using the nitride semiconductor nucleus 4 as a growth nucleus. After removing the protective film 3, the second nitride semiconductor layer 5 is grown from the nitride semiconductor nucleus 4. As a result, the second nitride semiconductor layers are joined together to form a nitride semiconductor substrate having a flat mirror surface. Here, since it is difficult for the nitride semiconductor to grow from the first nitride semiconductor layer 2 which is a polycrystalline region, the propagation of dislocation defects from the first nitride semiconductor layer 2 to the second nitride semiconductor layer is prevented. Can be suppressed. In addition, a cavity can be formed in this region by laterally growing the second nitride semiconductor layer from the nitride semiconductor nucleus 4. With this cavity, it is possible to suppress the stress generated during the growth of laterally growing the second nitride semiconductor layer 5 grown from the nitride semiconductor nucleus 4.

As the second nitride semiconductor layer 5, an undoped nitride semiconductor and Si, Ge, Sn, S are used.
Semiconductor doped with n-type impurities such as
A nitride semiconductor doped with a p-type impurity such as g or Zn, or a nitride semiconductor co-doped with an n-type impurity and a p-type impurity can be used. The growth temperature of the second nitride semiconductor layer 5 is 900 to 1100 ° C. The film thickness of the second nitride semiconductor layer 5 may be 3 μm or more, preferably 5 to 30 μm as long as the nitride semiconductors can be bonded to each other in order to form the nitride semiconductor substrate. As described above, it is possible to obtain a nitride semiconductor substrate in which dislocation defects are reduced and the number of dislocations per unit area is 1 × 10 ⁶ / cm ² or less.

In the present invention, a base layer (not shown), the first nitride semiconductor layer 2, the nitride semiconductor nucleus, the second layer
All of the nitride semiconductor layers 5 of the general formula In _x Al _y G
_{a 1 -x-y N (0} ≦ x, 0 ≦ y, x + y ≦ 1) having a composition represented by. However, these may have different compositions. Further, as a method for growing a nitride semiconductor of the present invention, MOVPE (metal organic chemical vapor deposition),
HVPE (halide vapor phase epitaxy), MBE (molecular beam epitaxy), MOCVD (metal organic chemical vapor deposition)
A vapor phase growth method such as the above can be applied.

As an etching method for forming the opening in the protective film, there are methods such as wet etching and dry etching. As the dry etching, there are devices such as reactive ion etching (RIE), reactive ion beam etching (RIBE), and electron cyclotron etching (ECR). In any of the methods shown here, etching for forming an opening in the protective film can be performed by appropriately selecting an etching gas.

[0034]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto. [Example 1] A sapphire substrate 1 having a C-plane as a main plane and an orientation flat plane as an A-plane was used, a temperature was 500 ° C, hydrogen was used as a carrier gas, and ammonia and TMG (trimethylgallium) were used as a source gas. And are used to grow an underlayer of GaN on the sapphire substrate 1 to a film thickness of 200 angstroms.

Next, the temperature of the substrate is set to 1050 ° C. under the atmospheric pressure in the MOCVD apparatus, and TMG is used as the source gas.
(Trimethylgallium) 230 μmol / min (V
/ III ratio = 910), ammonia 0.2 mol / mi
Using n, the first nitride semiconductor layer 2 made of undoped GaN is grown to a film thickness of 2.5 μm.

CVD is performed on the first nitride semiconductor layer 2.
Method, a protective film 3 made of SiO ₂ is formed to a film thickness of 5 μm, a stripe-shaped photomask is formed, and a stripe width of 17 μm and an opening width of 3 μm are formed by an asher.
A protective film 3 made of O ₂ is formed. In addition, this protective film 3
The stripe direction is perpendicular to the sapphire A surface, the cross-sectional shape is trapezoidal, and the upper base width is 5 μm and the lower base width is 17 μm.

After that, in the MOCVD apparatus, the nitride semiconductor nucleus 4 is grown with the first nitride semiconductor layer 2 which is the opening of the protective film 3 as a growth starting point. This nitride semiconductor nucleus has a height not exceeding the protective film and has a thickness of 3 μm.
Grow with. As a growth condition, TMG2 is used as a source gas.
30 μmol / min (V / III ratio = 910), ammonia is used, undoped GaN is 400 Torr, and temperature is 1070 ° C. Next, the protective film is completely removed with buffer hydrofluoric acid.

Thereafter, in the MOCVD apparatus, the second nitride semiconductor layer 5 is grown in the vertical direction and the horizontal direction with the nitride semiconductor nucleus 4 as a growth starting point, and the adjacent second nitride semiconductor layers are bonded to each other. To make a nitride semiconductor substrate.
The growth conditions are as follows: TMG 230 μmol / source gas
min (V / III ratio = 790), 0.2m ammonia
undoped GaN at normal pressure and temperature of 1050 ° C., and the film thickness is 15 μm on the nitride semiconductor nucleus.
To grow.

The nitride semiconductor substrate obtained as described above is the second
The surface of the nitride semiconductor layer 5 can be a nitride semiconductor substrate having low dislocation defects.

[Embodiment 2] The same growth as in Embodiment 1 is carried out except that silane gas is added to the growth conditions for the second nitride semiconductor layer in Embodiment 1. The obtained nitride semiconductor substrate can be a Si-doped n-type nitride semiconductor substrate.

[Embodiment 3] In Embodiment 1, the SiO ₂
The protective film 3 made of is formed with a film thickness of 5 μm. Next, the protective film is patterned to have a stripe width of 18 μm and an opening width of 2 μm. After that, the nitride semiconductor nucleus 4 is formed with a lower bottom layer of 2 μm and an upper bottom layer of 16 μm having an inverted trapezoidal cross section. Others are grown in the same manner as in Example 1. From the above, a nitride semiconductor substrate having a nitride semiconductor film thickness of 15 μm or more and low dislocation defects can be obtained.

[Embodiment 4] A film thickness of 100 μm is formed on the nitride semiconductor substrate obtained in Embodiment 1 by the HVPE method.
After growing GaN by, the sapphire substrate is removed by polishing. Further, the peeling surface is made into a mirror surface by chemical polishing. From the above, a single substrate of nitride semiconductor is obtained.

[0043]

As described above, according to the method for growing a nitride semiconductor of the present invention, the nitride semiconductor is not grown on the protective film in a stressed state, but rather in the vertical direction from the nitride semiconductor nucleus. Further, the second nitride semiconductor layer can be grown laterally to provide a nitride semiconductor substrate with low dislocation defects.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a nitride semiconductor substrate obtained in each step of the present invention.

FIG. 2 is a schematic cross-sectional view showing the structure of a nitride semiconductor substrate obtained in each step of the present invention.

FIG. 3 is a schematic cross-sectional view showing the structure of a nitride semiconductor substrate obtained in each step of the present invention.

FIG. 4 is a schematic cross-sectional view showing the structure of a nitride semiconductor substrate obtained in each step of the present invention.

FIG. 5 is a schematic cross-sectional view showing the structure of a nitride semiconductor substrate obtained in each step of the present invention.

[Explanation of symbols]

1 ... Substrate 2 ... First nitride semiconductor layer 3 ... Protective film 4 ... Nitride semiconductor core 5 ... Second nitride semiconductor layer

Claims (8)

[Claims] 1. A nitride semiconductor substrate in which a nitride semiconductor layer is grown on a substrate, wherein the nitride semiconductor layer includes a first nitride semiconductor layer on the substrate and the first nitride semiconductor. A nitride semiconductor nucleus having an opening on the layer, the second semiconductor grown from the nitride semiconductor nucleus
And a nitride semiconductor layer, and has a cavity or a plurality of holes on both sides of the nitride semiconductor nucleus which is an interface between the first nitride semiconductor layer and the second nitride semiconductor layer. A nitride semiconductor substrate having a crystalline region. 2. The nitride semiconductor substrate according to claim 1, wherein the nitride semiconductor nucleus has an inverted trapezoidal cross section. 3. The nitride semiconductor substrate according to claim 1, wherein the nitride semiconductor nucleus has a planar shape of a stripe shape or a lattice shape. 4. A method for growing a nitride semiconductor substrate, which comprises growing a nitride semiconductor on a substrate using an epitaxial growth method, comprising: a first nitride semiconductor layer on the substrate; and a protection layer patterned on the first nitride semiconductor layer. A step of forming a film, a step of forming a nitride semiconductor nucleus from the opening of the protective film, and a step of thermally decomposing the nitride semiconductor under the protective film, and thereafter, after removing the protective film, And a step of forming a second nitride semiconductor layer by using the nitride semiconductor nucleus as a growth starting point. 5. The method for growing a nitride semiconductor substrate according to claim 4, wherein the nitride semiconductor nucleus is grown at a temperature higher than that of the first nitride semiconductor layer. 6. The growth temperature of the nitride semiconductor nucleus is 70.
The method for growing a nitride semiconductor substrate according to claim 4, wherein the temperature is 0 ° C. or higher. 7. The method for growing a nitride semiconductor substrate according to claim 4, wherein the nitride semiconductor nuclei are formed in a stripe shape, a stripe shape, or a lattice shape. 8. A core comprising a nitride semiconductor on the substrate,
Alternatively, the layer is grown as a base layer, and the first nitride semiconductor layer is grown through the base layer, and the method for growing a nitride semiconductor substrate according to claim 4.