JP2003077841A - Nitride semiconductor substrate and growth method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nitride semiconductor substrate where mass productivity and yields are improved, penetration dislocation is reduced, and crystallinity is excellent in a manufacturing method of the nitride semiconductor substrate for enabling a nitride semiconductor to be subjected to epitaxial growth on the substrate without using protective films. SOLUTION: A protection film is partially formed on a substrate, and is subjected to heat treatment, thus forming a nitrogen-containing region at an exposure section in the substrate. After that, the protective film is removed, and the nitride semiconductor is grown. In this case, in the nitride semiconductor device, growth is selectively advanced on the substrate as compared with the nitride-containing region. Additionally, continuous reaction is enabled to obtain a nitride semiconductor substrate having a nitride semiconductor layer whose surface is a mirror and is flat.

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 a nitride semiconductor substrate composed of 1) and a method for growing the same.

[0002]

2. Description of the Related Art Since there is no substrate lattice-matched with a nitride semiconductor, a different substrate different from the nitride semiconductor such as sapphire, spinel or silicon carbide is used as a growth substrate for the nitride semiconductor. A method of reducing threading dislocations on a sapphire substrate or the like through a buffer layer due to mismatch of lattice constants and thermal expansion coefficients, and a method utilizing lateral growth have been reported.

Japanese Patent Laid-Open No. 10-312971 discloses S
Patterning is performed on a substrate using a mask material such as iO ₂ and the selective growth is performed until the mask material is filled up. By bending the dislocation propagation direction in the crystal growth process on the mask, the dislocation density is reduced. It is a thing.

[0004]

In the above method, it is necessary to grow a nitride semiconductor layer on the substrate, pattern the mask, and re-grow the nitride semiconductor.
These steps cannot be carried out in a continuous reaction, and must be taken in and out of the reactor during the growth of the nitride semiconductor substrate. Therefore, there is a problem that the crystallinity of the nitride semiconductor is deteriorated due to surface oxidation.

Further, in the above method, when the mask material is embedded, lateral growth of the nitride semiconductor proceeds on the growth surface on the mask. As a result, the crystal axis of the nitride semiconductor is tilted, which causes tilt. When the tilted crystals are united with each other, a new dislocation defect is generated. Further, if the nitride semiconductor is grown in the state of having the mask, the mask is decomposed during the growth of the nitride semiconductor element, which causes the deterioration of the characteristics of the nitride semiconductor.

In view of the above problems, it is an object of the present invention to simplify the nitride semiconductor growth process. Another object is to obtain a nitride semiconductor substrate with reduced threading dislocations.

[0007]

A nitride semiconductor substrate of the present invention comprises a substrate having a partial nitrogen-containing region on its surface,
A nitride semiconductor substrate, comprising a nitride semiconductor layer epitaxially grown using a nitrogen-containing region of the substrate as a growth interface. The nitrogen-containing region is formed of aluminum nitride.

The nitride semiconductor substrate is characterized by having a cavity sandwiched between the substrate and the nitride semiconductor layer and adjacent to the nitrogen-containing region.

The method of growing a nitride semiconductor substrate according to the present invention comprises:
A method for growing a nitride semiconductor substrate for epitaxially growing a nitride semiconductor on a substrate, comprising: forming a protective film having an opening on the substrate; and containing nitrogen on the substrate exposed from the opening of the protective film. A step of forming a region, a step of removing the protective film, a step of selectively forming a nitride semiconductor nucleus on the nitrogen-containing region by a vapor phase growth method, a vertical direction from the nitride semiconductor nucleus and And a step of growing a nitride semiconductor laterally to form a nitride semiconductor layer having a flat uppermost surface. Here, the nitrogen-containing region is formed by a reaction between the substrate surface and the N element-containing raw material on a substrate such as sapphire (Al ₂ O ₃ ). Therefore, modification occurs on the surface of the substrate, and AlN and other compounds containing Al and N are formed. Further, this AlN or the like is preferable because it can selectively grow a nitride semiconductor.

The growth of the nitride semiconductor substrate according to claim 4, wherein the nitrogen-containing region formed on the first surface of the substrate is formed by heat treating the substrate at 800 ° C. or higher. Method.

The protective film removing step is characterized in that the protective film is treated with an acid solution selected from HF and BHF.

The protective film is made of SiO ₂ , SiN, SiO.
It is characterized by using a material selected from N and TiO ₂ .

In the step of forming the nitride semiconductor layer, the nitride semiconductor layer is grown from the nitride semiconductor nucleus so that a cavity is formed between the nitrogen-containing regions.

A planar shape of the protective film is formed in a stripe shape. In addition, the planar shape of the protective film is an island shape, a rectangular shape, a lattice shape, or a shape obtained by extracting these.

As shown in FIG. 3, a nitrogen-containing region is formed on the substrate, and then, selectively grown nitride semiconductor nuclei are formed on the nitrogen-containing region as shown in FIG. 4, and further, a flat surface shown in FIG. 5 is formed. The formation of the nitride semiconductor film is a continuous reaction. In the present invention, the nitride semiconductor is excellent in mass productivity since there are no working steps such as putting in and out of the reactor. In addition, conventional ELO
In the method, it was necessary to take it in and out of the reactor, so the substrate on which the nitride semiconductor was once grown is exposed to the atmosphere, and then the nitride semiconductor is regrown, so that dust etc. do not adhere to the nitride semiconductor. I was afraid. However,
The present invention can provide a nitride semiconductor substrate having good crystallinity without such a problem.

After forming the nitride semiconductor film, a cavity is formed adjacent to the nitride semiconductor nucleus. Since this cavity has an effect as an air gap, it can be expected to alleviate warpage caused by lattice mismatch between the substrate and the nitride semiconductor. Therefore, the subsequent steps of forming a light emitting element, a light receiving element, and other electronic devices using this nitride semiconductor substrate are facilitated. Further, by having this cavity, it is possible to recognize the position on the substrate.

A nitride semiconductor substrate having a nitride semiconductor layer as a thin film can be obtained by performing lateral growth selectively. The conditions for promoting the lateral growth include reducing the molar ratio (V / III ratio) of the group V raw material and the group III raw material, or reducing the pressure,
The lateral growth can be selectively performed under high temperature conditions, doping with Mg, and the like.

In the lateral growth of the nitride semiconductor layer in the present invention, the nitride semiconductor is partially shaved by dry etching typified by RIE or ICP to form irregularities in the nitride semiconductor to form recesses. It does not grow laterally from the side. Physically damaging the nitride semiconductor that serves as a growth nucleus by dry etching or the like causes deterioration of crystallinity of the nitride semiconductor formed during regrowth.
Therefore, the present invention does not require the etching as described above, and selectively forms a nitride semiconductor nucleus and laterally grows from the nitride semiconductor nucleus.

From the above, the nitride semiconductor selectively grown
There are many dislocation defects on the nucleus (first region)
Of the region laterally grown using this as a growth nucleus (second region
In this area, dislocation defects also bend and extend in the lateral direction.
A low dislocation region can be formed on the second region.
When the number of dislocations per unit area is used only in the buffer layer
It can be reduced by more than 2 digits compared to the actual value.
Dislocation density is 1 × 10 ⁷Pieces / cm^TwoIs a nitride
A semiconductor substrate can be provided.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. 1A to 1E are cross-sectional views for explaining a method for growing a nitride semiconductor according to the present invention. Here, 1 is a substrate, and 2 is a protective film partially formed on the substrate. Reference numeral 3 is a nitrogen-containing region formed by heat-treating the substrate surface.
Further, 4 is a nitride semiconductor nucleus formed during selective growth of the nitride semiconductor, and 5 is a nitride semiconductor layer formed by a continuous reaction from the nitride semiconductor nucleus 4. Figure 1
(E) shows the first region and the second region. Second
Region is formed by lateral growth and becomes a dislocation reduction region.

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. Figure 1
The second region shown in (e) is a region in which dislocation defects are significantly reduced, and the number of dislocations per unit area is 1 × 10 ⁷ /
cm ² or less, more preferably 1 × 10 ⁶ pieces / cm ² or less. In the first region, threading dislocations advancing in the vertical direction remain, so the number of dislocations is 1 × 10 ⁸ to 1 × 10 ¹⁰ / cm 3.
It will be about ² .

Hereinafter, each step in the embodiment of the present invention will be described in more detail with reference to the drawings. As this substrate 1,
An insulating substrate such as sapphire or spinel (MgAl ₂ O ₄ ) having a C-plane, R-plane, or A-plane as a main surface,
SiC (6H, 4H, 3C), ZnS, ZnO, GaA
An oxide substrate or the like that forms a lattice bond with s, Si, and a nitride semiconductor can be used. Further, when a single substrate of a nitride semiconductor of the same kind, preferably a substrate of a single crystal, is used, homoepitaxial growth is performed, so that the warpage of the nitride semiconductor substrate generated after growing the nitride semiconductor can be further suppressed. .

Next, the protective film 2 formed on the substrate 1 is one in which the nitride semiconductor does not grow or does not grow easily on the surface and has heat resistance against heat treatment such as annealing. If Specific examples of the protective film 2 include silicon oxide (SiO _x ), silicon nitride oxide (Si
O _x N _y ), titanium oxide (TiO _x ), zirconium oxide (ZrO _x ), and other oxides, as well as silicon nitride (Si
_x N _y ), a metal having a melting point of 1200 ° C. or higher, or a multilayer film thereof can be used.

As a method of forming the protective film 2, CV is used.
A film is formed by using D, sputtering, vapor deposition, or the like.
Further, the film thickness of the protective film is not particularly limited as long as it can protect the substrate surface under the protective film by heat treatment at 800 ° C. or more, but if the film thickness is formed in the range of 0.2 to 10 μm, It is possible to easily remove the protective film in a later step without deteriorating the surface of the substrate below the protective film. Further, the planar shape of the protective film is a stripe shape, but it may be a lattice shape, an island shape, a circle shape, or a polygon shape. It is also possible to use a protective film having a circular or polygonal opening which is formed into these extracted shapes. As an etching method for forming the opening in the protective film, there are methods such as wet etching and dry etching. The dry etching includes devices such as reactive ion etching (RIE), ICP, reactive ion beam etching (RIBE), electron cyclotron etching (ECR), and asher. 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.

For example, when the protective film has a stripe shape, the width of the opening is 1 to 100 μm, preferably 2 to
It is 15 μm. Further, if the ratio of the stripe width (S) of the protective film to the opening width (W) is S / W, it is 0.1 or more. In the subsequent step, it may be in the range where the surface can be flattened by growth from the nitride semiconductor nucleus, but preferably 1
/ 3 ≦ (S / W) ≦ 3. Specifically, both the stripe width (S) and the opening width (W) are 10 μm or the like.

If the substrate 1 is a sapphire substrate when the protective film 2 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. The protective film 2 may be formed. By doing so, the surface after growing the nitride semiconductor can be made more flat. Specifically, the range of θ = 0 ° to 5 ° is set to the left and right with respect to the vertical axis of the orientation flat surface. Further, the substrate used in the present invention may have a processed off-angle. For example, the off angle may be formed in steps. Here, the off angle is 0 ° to 2 °.

Next, a nitrogen-containing region is formed in the opening of the protective film 2. As a method of forming this nitrogen-containing region, the substrate 1 is heat-treated in an atmosphere containing a nitrogen raw material.
The atmosphere containing the nitrogen source is, for example, a nitrogen gas atmosphere or an ammonia gas atmosphere. The temperature for heat treatment is 700 ° C. or higher, preferably 800 ° C. or higher. The processing time is 5 minutes or more.

Next, the protective film is removed after forming the nitrogen-containing region. As a removing method, wet etching using BHF or HF is used, and dry etching is used otherwise.

After removing the protective film, a base layer (not shown) is grown on the substrate 1. As the base layer, Al
N, GaN, AlGaN, InGaN or the like is used.
This underlayer has a growth temperature of 300 ° C. or higher and 900 ° C. or lower,
Preferably, the temperature is 700 ° C. or lower, and the film is grown to have a film thickness of 10 Å or more and 0.5 μm or less. This is for alleviating the lattice constant mismatch with the nitride semiconductor layer grown on the substrate 1, and has an effect as a buffer layer for reducing dislocation defects.

Next, the nitride semiconductor layer 5 is formed on the substrate 1. First, the nitride semiconductor nucleus 4 is selectively formed using the nitrogen-containing region as a growth starting point. As the growth conditions, a group III element-containing compound and a compound having a nitrogen source are used as raw materials. Group III elements include Ga, Al, and In, and these trimethyl compounds and triethyl compounds are I
A group II element-containing compound is used. In addition, ammonia, N ₂ H _4, or the like is used as the compound having a nitrogen source. For example, II
When TMG (trimethylgallium) is used as the group I element-containing compound, TMG is 100 to 150 cc / min, ammonia is 5 to 10 L / min, and the reaction time is 180 minutes or less. The growth temperature is set to 900 ° C to 1200 ° C.
The film thickness is 1.0 μm or more, preferably 3 to 5 μm.

Further, the growth temperature is set higher than the growth temperature of the nitride semiconductor nucleus 4 by 30 ° C. or more to grow the nitride semiconductor layer 5. The raw material is the same as the nitride semiconductor nucleus. The growth conditions include, for example, TMG of 100 to 200 cc / min,
Ammonia is 1 to 5 L / min, and the reaction time is 500 minutes or less, preferably 400 minutes. Further, the pressure condition of this continuous reaction is normal pressure, but it can be carried out under reduced pressure condition (about 400 Torr). The film thickness of the nitride semiconductor layer 5 may be 5 μm or more, preferably 10 to 15 μm as long as the nitride semiconductor layers can be joined and planarized. From the above, as shown in FIG. 1E, the number of dislocations in the second region obtained by utilizing lateral growth is 1 × 10 ⁷ dislocations / cm ² or less, preferably 1 × 10 ⁶ dislocations / cm ^2. The following nitride semiconductor substrate can be provided.

In the present invention, the nitride semiconductor has the general formula I
_{n x Al y Ga 1-x} -y N (0 ≦ x, 0 ≦ y, x + y
Having a composition represented by ≦ 1). However, these may have different compositions during continuous reaction. Further, an undoped nitride semiconductor, a nitride semiconductor doped with n-type impurities such as Si, Ge, Sn, and S, or a nitride semiconductor doped with p-type impurities such as Mg and Zn, and n-type impurities and p
A nitride semiconductor that is co-doped with a type impurity can be used. The nitride semiconductor growth method of the present invention includes MOVPE (metal organic chemical vapor deposition), HVPE (halide vapor deposition), MBE (molecular beam epitaxy), MOCVD (metal organic chemical vapor deposition), and the like. The vapor phase growth method can be applied.

Further, there is a method in which a thick film is grown by a combination with the HVPE method and threading dislocations are uniformly reduced over the entire surface during the thick film growth. When a nitride semiconductor is grown by this HVPE method, for example, in the case of GaN, H
Reaction of Cl gas with Ga metal results in GaCl or GaC
l ₃ is formed, and this Ga chloride reacts with ammonia to deposit GaN on the substrate.
By changing the growth rate at the time of growing a nitride semiconductor by the HVPE method and performing two-step growth, crystal defects can be significantly reduced, and a single substrate made of a nitride semiconductor can be obtained in combination with the present invention. . As a method of removing only the substrate from the thick film nitride semiconductor substrate,
There is a method of removing the substrate by polishing, and a method of removing the substrate by irradiating the interface between the substrate and the nitride semiconductor with an electromagnetic wave such as an excimer laser. Therefore, even if it is a nitride semiconductor substrate grown on an insulating substrate such as a sapphire substrate, by removing the sapphire substrate it becomes a single substrate made of a nitride semiconductor, and a nitride semiconductor laser diode having a back electrode structure, etc. Can be provided.

Next, an embodiment for forming a semiconductor laser device on the nitride semiconductor substrate will be described. Al _x Ga _1-x N (0 ≦ X <1) doped with n-type impurities is grown as an n-side contact layer on the nitride semiconductor substrate to a thickness of about 1 to 5 μm. On the n-side contact layer, an n-type impurity-doped In _x Ga _1-x N (0 ≦
X <1) is grown to 0.1 to 0.3 μm. The crack prevention layer can be omitted. Then, an n-side cladding layer is grown on the crack prevention layer. The n-side cladding layer preferably has a superlattice structure, and includes a layer made of undoped Al _x Ga _1-x N (0 ≦ X <1) and a layer made of n-type GaN doped with n-type impurities. Are alternately laminated to grow an n-side clad layer having a superlattice structure with a total film thickness of 2.0 μm or less. Then, an n-side optical guide layer made of undoped GaN is used in an amount of 0.05 to 0.2
Grow with a film thickness of m. The n-side light guide layer may be doped with an n-type impurity.

Next, non-doped In _x Ga is formed on the barrier layer.
_1-x N (0≤X≤1) and n-type impurity doping I in well layer
An active layer having a single quantum well structure or a multiple quantum well structure made of n _x Ga _1-x N (0 ≦ X ≦ 1) is grown. In the case of the multiple quantum well structure, the barrier layers and the well layers are alternately laminated at the same temperature for about 2 to 5 times, and finally the barrier layers are formed to have a total film thickness of 200 to 500 Å.

Next, p-type Al _x doped with p-type impurities as a p-side cap layer (not shown) is formed on the active layer.
Ga _1−x N (0 ≦ X <1) is grown. This p-side cap layer is grown to a film thickness of about 50 to 500 Å. Then, a p-side optical guide layer made of undoped GaN was formed on the substrate.
It is grown to a film thickness of 05 to 0.5 μm. The p-side light guide layer may be doped with p-type impurities. Next, a p-side cladding layer is grown on the p-side light guide layer. The p-side clad layer preferably has a superlattice structure like the n-side clad layer, and is undoped Al _x Ga _1-x N.
A layer of (0 ≦ X <1) and a layer of p-type GaN doped with a p-type impurity are alternately laminated to form a total film thickness of 0.3.
A p-side cladding layer having a superlattice structure of about 0.8 μm is grown. Finally, on the p-side cladding layer is grown p-side contact layer made of p-type impurities doped at _{Al x Ga 1-x N (} 0 ≦ X ≦ 1).

Here, the impurity concentration is not particularly limited, but the n-type impurity and the p-type impurity are preferably 1 × 10 ¹⁸ / cm ³ to 1 × 10 ²⁰ / cm ³ . The n-type impurities include Si, Ge, Sn,
S, O, Ti, Zr, Cd and the like can be mentioned, and Be, Zn, Mn, Mg, Ca, Sr and the like can be mentioned as p-type impurities.

Next, after forming the semiconductor laser device, p
When the electrode and the n-electrode are formed on the same surface side, the n-side contact layer is exposed by etching in order to form the n-electrode. Next, a ridge is formed by etching to form a stripe-shaped optical waveguide region. Here, the etching is preferably anisotropic etching for forming a ridge, and for example, an RIE (reactive ion etching) device or the like is used. In the present invention, the ridge width formed here depends on the buried layer formed in a later step and the output, but the ridge width is 1.0 to 3.
It can be as wide as 0 μm. The etching depth is such that at least the p-side cladding layer in the nitride semiconductor element is etched. Further, the ridge shape includes a forward mesa type, an inverted mesa type, and a vertical type, and these shapes are preferable because they can confine light in the lateral direction.

After forming the ridge, a buried film (for example, ZrO, DLC, glass, etc.) made of an insulator is formed on the nitride semiconductor on both side surfaces of the ridge from the exposed side wall of the ridge by a sputtering method or the like. The effect of this buried film is current confinement and lateral optical confinement. In order to confine light in the lateral direction, it is necessary to provide a refractive index difference with the nitride semiconductor layer, and in order to confine light in the core region, a material having a smaller refractive index than the nitride semiconductor is embedded in the buried layer. Used for. In the vertical light confinement, light is confined in the core by providing a refractive index difference between the core region having a high refractive index and the p- and n-side cladding layers having a low refractive index.

After that, the buried layer formed on the uppermost surface of the ridge to form the p-electrode is removed by lift-off or the like. Next, after the removal, p-electrodes made of Ni / Au are formed in stripes on the exposed surface of the p-side contact layer, and p
After forming the electrodes, an n-electrode made of Ti / Al is formed in parallel with the ridge stripe on the surface of the n-side contact layer. Next, a pad electrode which is a take-out electrode is formed on the p electrode and the n electrode in the order of Ni / Ti / Au. Also, the p electrode is Ni / Au / RhO, and the p-side pad electrode is RhO / P.
A combination of t / Au is also possible. Before forming the pad electrode, a dielectric multilayer film made of SiO ₂ , TiO ₂ or the like may be formed on the resonator surface (light emission end surface side). By including this dielectric multilayer film, the end face deterioration of the light emitting end face at the time of high output can be suppressed.

Further, in the direction perpendicular to the striped electrodes, the substrate side is deviated into a bar shape, and the deviated surface ((1
A resonator is formed on the (1-00) plane, the plane corresponding to the side surface of the hexagonal system = M plane). A dielectric multilayer film is formed on this resonator surface, and the bar is cut in the direction parallel to the electrodes to obtain a nitride semiconductor laser device. This nitride semiconductor laser device is placed on a heat sink, wire-bonded, and sealed with a cap to obtain a nitride semiconductor laser diode.

The nitride semiconductor laser diode obtained as described above
When laser oscillation was attempted at room temperature using iodine,
Vibration wavelength 400-420 nm, threshold current density 2.9 kA /
cm ^TwoShows continuous oscillation at 30mW or higher,
Ripple does not occur even when light output of about 50 mW,
Shows life characteristics of 3000 hours or more.

[0043]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto. [Example 1] Using a sapphire substrate 1 having a C-plane as a main surface,
A protective film 2 made of SiO ₂ having a thickness of 0.3 μm is formed on the substrate 1 by a CVD method, a stripe-shaped photomask is formed, and a stripe width of 10 μm and an opening width of 10 μm are formed by ICP (dry etching). A protective film made of SiO ₂ is formed. This stripe direction is substantially perpendicular to the sapphire A surface.

Then, the patterned substrate is heat-treated in a nitrogen atmosphere. This modifies the exposed portion of the substrate 1 in the opening. The conditions are 900 ° C. and about 20 minutes. After that, the protective film 2 is covered with BHF (wet etching).
To remove.

Then, the film was carried into a MOCVD apparatus and the temperature was raised to 50.
0 ° C, hydrogen as carrier gas, ammonia and T as raw material gas
An underlayer (not shown) made of GaN is formed on the sapphire substrate 1 by using MG (trimethylgallium).
It is grown to a film thickness of 00 angstrom.

Further, a nitride semiconductor is grown by continuous reaction in the MOCVD apparatus. First, the growth temperature is 1
At 150 ° C., TMG was flowed at 100 cc / min and ammonia was flowed at 8 L / min for 60 minutes. 5μ
GaN, which is a nitride semiconductor nucleus, was formed in a stripe shape with a thickness of m. Further, a nitride semiconductor layer is grown using the nitride semiconductor nucleus as a growth starting point. Growth temperature 1180
C., TMG was 140 cc / min in the source gas, and ammonia was 4 L / min in the source gas, and the reaction was performed for 400 minutes to grow GaN to be the nitride semiconductor layer with a film thickness of 15 .mu.m. The nitride semiconductor substrate obtained as described above could be a nitride semiconductor substrate in which the number of dislocations per unit area on the surface was 1 × 10 ⁷ dislocations / cm ² or less. A CL photograph of the nitride semiconductor substrate obtained in this example is shown in FIG.

[Example 2] GaN is grown on the nitride semiconductor substrate obtained in Example 1 to have a thickness of 100 µm. As a raw material, Ga metal and HCl are used by the HVPE method.
Using gas and ammonia, GaCl partial pressure is 1.25 × 1
0 ^-3 atm, the ammonia partial pressure to 0.375Atm. After growing a 100 μm thick film, the sapphire substrate is removed by grinding to obtain a single substrate made of a nitride semiconductor.

Example 3 In Example 1, 1.7 × 10 ⁻³ silane gas was used as a growth condition in the nitride semiconductor.
The growth is performed in the same manner as in Example 1 except that μmol is added.
The nitride semiconductor substrate thus obtained is Si-doped n-type.
A type nitride semiconductor substrate can be obtained.

[0049]

As described above, according to the present invention, it is possible to provide a method for growing a nitride semiconductor substrate which is suitable for mass production with a simplified growth process. Further, since it is a nitride semiconductor substrate with low dislocation defects and the growth process is performed by continuous reaction in a reaction apparatus, it is possible to provide a substrate in which impurities are not mixed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a growth step in the present invention.

FIG. 2 shows a surface CL photograph of a nitride semiconductor substrate obtained by the present invention.

[Explanation of symbols]

1 ... Substrate 2 ... Protective film 3 ... Nitrogen-containing region 4 ... Nitride semiconductor core 5 ... Nitride semiconductor layer

Claims (10)

[Claims] 1. A nitride semiconductor substrate comprising a substrate partially having a nitrogen-containing region on its surface and a nitride semiconductor layer epitaxially grown with the nitrogen-containing region of the substrate as a growth interface. 2. The nitride semiconductor substrate according to claim 1, further comprising a cavity sandwiched between the substrate and the nitride semiconductor layer and adjacent to the nitrogen-containing region. 3. The nitride semiconductor substrate according to claim 1, wherein the nitrogen-containing region is made of aluminum nitride. 4. A method for growing a nitride semiconductor substrate, which comprises epitaxially growing a nitride semiconductor on a substrate, comprising: forming a protective film having an opening on the substrate; and exposing the protective film through the opening. Forming a nitrogen-containing region on the substrate, removing the protective film, and then selectively forming a nitride semiconductor nucleus on the nitrogen-containing region by vapor phase epitaxy, and the nitride semiconductor And a step of growing a nitride semiconductor in a vertical direction and a horizontal direction from a nucleus to form a nitride semiconductor layer having a flat uppermost surface. 5. The nitride semiconductor substrate according to claim 4, wherein the nitrogen-containing region formed on the first surface of the substrate is formed by heat treating the substrate at 800 ° C. or higher. How to grow. 6. The step of removing the protective film is performed using HF or BHF.
The method for growing a nitride semiconductor substrate according to claim 4 or 5, wherein the acid treatment is performed with. 7. The protective film is formed of SiO ₂ , SiN, SiO.
The method for growing a nitride semiconductor substrate according to claim 4, wherein a material selected from N and TiO ₂ is used. 8. The method according to claim 4, wherein in the step of forming the nitride semiconductor layer, a cavity is provided between the nitrogen-containing regions by growing a nitride semiconductor layer from a nitride semiconductor nucleus. A method for growing a nitride semiconductor substrate according to claim 1. 9. The method of growing a nitride semiconductor substrate according to claim 4, wherein the planar shape of the protective film is formed in a stripe shape. 10. The method for growing a nitride semiconductor substrate according to claim 4, wherein the planar shape of the protective film is an island shape, a rectangular shape, a lattice shape, or an extraction shape of these.