JP2002175985A - Method for manufacturing nitride semiconductor epitaxial wafer and the nitride semiconductor epitaxial wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride semiconductor epitaxial wafer and a method of manufacturing the same, with which few crystal defects, bending or cracks occur, and to provide a nitride semiconductor epitaxial wafer which can provide large area. SOLUTION: An intermediate layer 2, 12 is obtained by implanting ions of hydrogen, nitrogen, oxygen, etc., into a nitride semiconductor layer 11 to be peeled, which is formed in the vicinity of the surface of a sapphire substrate 1 or on a hetero substrate 10. Since these intermediate layers 2, 12 have amorphous structures, deformation is absorbed and relieved, thereby reducing cracks, bending, etc. Since the intermediate layers 2, 12 are heated during growth of a nitride semiconductor layer 3, 14 voids occur. The voids are highly effective in absorbing and relieving deformation, reduces cracks, bending, etc., and reduces crystal relaxation, and since the substrate surface is a hetero substrate 10 or the nitride semiconductor layer 14, the deformation absorbing effect of the intermediate layer 2, 12 having voids is increased, and thus a nitride semiconductor epitaxial wafer having high quality and large diameter can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for manufacturing a nitride semiconductor epitaxial wafer and a nitride semiconductor epitaxial wafer.

[0002]

2. Description of the Related Art In recent years, in order to achieve high output and high efficiency of a light emitting diode (LED) and a laser diode (LD), a band gap is large (3.4 eV), a direct transition type, and a band is used. Since the gap can be controlled in a wide range, a nitride semiconductor has been used.

[0003]

However, since GaN or its mixed crystal, such as AlGaN or InGaN, does not have a practical substrate of the same kind, crystal growth is performed on a heterogeneous substrate such as sapphire or SiC. These dissimilar substrates have a lot of crystal defects in the growth layer because the lattice constant is significantly different from that of the growth layer. Also, since the expansion coefficients are greatly different, warpage and cracks occur during and after the growth of a thick film. These warpages and cracks become serious problems especially when growing a nitride semiconductor thick film.

[0004] Therefore, in order to fundamentally solve such a problem, development of a GaN substrate has been advanced, and a high-temperature high-pressure method (S. Porow) for synthesizing a GaN single crystal under high temperature and high pressure has been developed.
Ski et al, J. Mol. Cryst. Growth
178 (1997) p174) or H on a sapphire substrate.
A method of obtaining a GaN free-standing single crystal substrate by removing a sapphire substrate after growing a thick film of about several hundred μm by VPE method (Michael K. Kelly et.
al, Jpn. J. Appl. Phys. 38 (19
99) Pt. 2, No. 3A, pp. L217) and the like are typical.

However, in the high-temperature and high-pressure method, since the crystal is grown in an ultra-high-pressure cell, the size of the obtained GaN single crystal cannot be increased so much.
Only about mm is obtained. Moreover, the production cost is very high and not practical. HVPE (Hydride Vapor Pha)
(Se Epitaxy) directly on the sapphire substrate
Although a method of growing an N-thick film is more realistic, even in this case, crystal defects are considerably large, and there is no practical method for removing the sapphire substrate. In addition, there is a problem that the GaN thick film remains warped even after the removal.

During the epitaxial growth of the nitride semiconductor, the warpage of the sapphire substrate causes non-uniform contact with a heated object such as a graphite susceptor during the epitaxial growth of the nitride semiconductor. Uneven characteristics. In particular, in InGaN, this uneven concentration is fatal. Also, warpage of the sapphire substrate after growth poses a major problem in exposing fine patterns in photolithography.

Further, the crystal defects deteriorate the light emitting characteristics and reliability of the optical device, and cause leakage current, nonlinearity,
This may cause a decrease in reliability.

As a countermeasure for this, an ELO method (OH Namet) utilizing lateral growth by selective growth is used.
al, Appl. phys. Lett. 71 (199
7) 2472) and the FIELO method (A. Sakai et.
al, Appl. Phys. Lett. 71 (199
7) 2259) has been developed, but there is a problem that crystal defects still exist at about 10 ⁶ to 10 ⁷ cm ⁻³ , and the problem of warpage has not been improved at all.

On the other hand, with respect to a method of reducing the warpage, as disclosed in, for example, Japanese Patent Application Laid-Open No. 9-223819, a relaxation layer and a release layer are formed below the surface of a Si substrate by ion implantation of oxygen or nitrogen. Further, there is a method in which a nitride semiconductor is grown on a Si substrate whose surface is carbonized to form SiC, and the Si substrate is removed by etching thereafter.

However, in this method, in order to reduce the stress on the nitride semiconductor, the balance between the thickness of the Si substrate and the thickness of the SiC layer, the AlGaN buffer layer, and the structure of the nitride semiconductor layer formed on the Si substrate is precisely controlled. Must. In particular, when the nitride semiconductor layer formed by implanting nitrogen is used as a strain relaxation layer, Si is placed between the SiC layer and the strain relaxation layer to remove the Si substrate by etching.
Must be left, the conditions for surface carbonization are severe, and the strain relaxation layer is far from the nitride semiconductor growth layer, so that the strain relaxation effect is reduced. In addition, it is difficult to perform surface carbonization so as to completely cover the substrate surface when considering mass production.

An object of the present invention is to solve the above-mentioned problems and to provide a method of manufacturing a nitride semiconductor epitaxial wafer having few crystal defects and having less warpage and cracks, and a nitride semiconductor epitaxial wafer.

Further, an object of the present invention is to solve the above-mentioned problems, and to provide a method of manufacturing a nitride semiconductor epitaxial wafer and a nitride semiconductor epitaxial wafer capable of obtaining a large-area nitride semiconductor epitaxial with less crystal defects, warpage and cracks. To provide.

[0013]

In order to achieve the above object, a method for manufacturing a nitride semiconductor epitaxial wafer according to the present invention comprises forming an intermediate layer near the surface of a sapphire substrate with a mechanical strength lower than that of a sapphire substrate; A nitride semiconductor layer for a device is epitaxially grown on a sapphire substrate on which a layer is formed.

According to a method of manufacturing a nitride semiconductor epitaxial wafer of the present invention, a peeling nitride semiconductor layer is formed on a sapphire substrate, and the mechanical strength of the peeling nitride semiconductor layer is increased near the surface of the peeling nitride semiconductor layer. An intermediate layer weaker than the semiconductor layer is formed, and a nitride semiconductor layer for a device is epitaxially grown on the nitride semiconductor layer for separation on which the intermediate layer is formed.

In addition to the above structure, in the method for manufacturing a nitride semiconductor epitaxial wafer of the present invention, it is preferable that the thickness of the nitride semiconductor layer for a device is 10 μm or less.

In addition to the above structure, the method of manufacturing a nitride semiconductor epitaxial wafer of the present invention forms the intermediate layer by implanting ions from the surface of the peeling nitride semiconductor layer or the surface of the sapphire substrate to a depth at which the intermediate layer is to be formed. Is preferred.

In addition to the above configuration, in the method for manufacturing a nitride semiconductor epitaxial wafer of the present invention, it is preferable to use at least one of hydrogen ions, nitrogen ions and oxygen ions as ions.

In addition to the above structure, the method for manufacturing a nitride semiconductor epitaxial wafer of the present invention has an ion implantation acceleration voltage of 1 keV or more and 1 MeV or less, and an ion dose of 1 × 10 ¹⁵ cm ⁻² or more and 1 ×. It is preferably 10 ¹⁹ cm ^-2 or less.

In addition to the above structure, the method of manufacturing a nitride semiconductor epitaxial wafer of the present invention recovers damage caused by ion implantation of the surface crystal layer of the sapphire substrate or the nitride semiconductor layer for peeling after heat treatment after ion implantation. At the same time, the intermediate layer may be formed by generating fine voids and aggregates of voids in the vicinity of the surface.

In addition to the above configuration, in the method for manufacturing a nitride semiconductor epitaxial wafer of the present invention, it is preferable to control the size, quantity, density, distribution, etc. of the voids and the aggregates of the voids by heat treatment.

In addition to the above structure, in the method of manufacturing a nitride semiconductor epitaxial wafer of the present invention, it is preferable that the heat treatment is performed in an atmosphere of H ₂ or NH ₃ or a mixture of both.

In addition to the above structure, in the method for manufacturing a nitride semiconductor epitaxial wafer of the present invention, it is preferable that a portion from the intermediate layer to the sapphire substrate is removed by peeling off the intermediate layer.

In addition to the above structure, the method for manufacturing a nitride semiconductor epitaxial wafer of the present invention comprises the steps of: attaching another substrate to the surface of the nitride semiconductor layer for a device; It may be separated and removed at the boundary.

In addition to the above structure, the method of manufacturing a nitride semiconductor epitaxial wafer according to the present invention is characterized in that a semiconductor such as Si or a high thermal conductive substrate such as AlN or C
A metal such as u or Al may be used.

In addition to the above structure, the method for manufacturing a nitride semiconductor epitaxial wafer according to the present invention provides a device nitride semiconductor device in which a part of the sapphire substrate remaining in the device nitride semiconductor layer from which the sapphire substrate has been removed or the sapphire substrate has been removed. A part of the peeling nitride semiconductor layer remaining on the semiconductor may be removed by a method such as polishing.

The nitride semiconductor epitaxial wafer of the present invention is manufactured by any one of the methods described above, and is manufactured by using In _x A
_{l y Ga 1-xy N (} x, y ≧ 1, x + y ≦ 1) and has a composition.

According to the present invention, an intermediate layer obtained by implanting ions such as hydrogen, nitrogen, and oxygen into a separation nitride semiconductor layer formed near the surface of a sapphire substrate different from a nitride semiconductor or on a sapphire substrate. Has an amorphous structure, so that it absorbs and relaxes distortion and reduces cracks and warpage. The intermediate layer implanted with hydrogen is heated during the growth of the nitride semiconductor layer, so that voids are generated. Voids have high strain absorption and relaxation effects, reduce cracks and warpage, and reduce crystal defects. Since the substrate surface is a sapphire substrate or a nitride semiconductor, and the interlayer having voids has a large strain absorption effect and a large strain relaxation effect, there is no need for complicated surface carbonization treatment or precise control of the film thickness balance of multiple layers. Thus, a high-quality, large-diameter nitride semiconductor epitaxial wafer can be obtained.

[0028]

Embodiments of the present invention will be described below.

According to the method for manufacturing a nitride semiconductor epitaxial wafer of the present invention, an intermediate layer having a lower mechanical strength than a sapphire substrate is formed near the surface of a sapphire substrate, and a device nitride is formed on the sapphire substrate on which the intermediate layer is formed. The target semiconductor layer is grown epitaxially. The layer structure to be grown is an epitaxial structure of one or more layers.
It may have a semiconductor structure such as an N junction or a hetero junction. A layer structure suitable for various semiconductor elements such as a light emitting diode, a laser, a light receiving element, a field effect transistor, HEMT, and HBT, or an epitaxial layer structure constituting a part thereof.

The intermediate layer is a layer whose mechanical strength is made smaller than that of the sapphire substrate by implanting ions such as hydrogen, nitrogen and oxygen into the vicinity of the surface of the sapphire substrate. By applying heat treatment to the sapphire substrate after the ion implantation, a large number of fine voids can be generated in the intermediate layer, and the mechanical strength of the intermediate layer can be further reduced.

Since the intermediate layer functions as a buffer layer for alleviating the difference in thermal expansion between the nitride semiconductor crystal for a device and the sapphire substrate, cracks and warpage, which have conventionally been problems, are eliminated, and a high-quality nitride semiconductor is obtained. An epitaxial wafer is obtained. Further, the portion from the intermediate layer to the sapphire substrate can be easily peeled and removed.

The method of peeling includes natural peeling by heating during the process of growing the crystal film of the nitride semiconductor layer for a device, or peeling by subsequent heat treatment, peeling by a nitrogen jet from the side, peeling by a water jet, and peeling by laser irradiation. Various methods can be used.

By removing a part of the sapphire substrate slightly remaining on the back surface of the nitride semiconductor layer for device after peeling by polishing or the like, a large-diameter flat flat freestanding nitride semiconductor epitaxial wafer can be easily obtained. .

[0034] In addition to the above-described manufacturing method, the method for manufacturing a nitride semiconductor epitaxial wafer of the present invention further comprises forming a peeling nitride semiconductor layer on a sapphire substrate, and forming a nitride semiconductor layer near the surface of the peeling nitride semiconductor layer. An intermediate layer whose mechanical strength is weaker than that of the peeling nitride semiconductor layer may be formed, and the device nitride semiconductor layer may be epitaxially grown on the peeling nitride semiconductor layer on which the intermediate layer has been formed.

The thickness of the nitride semiconductor layer for the device is 10 μm.
m or less is preferable. This is to prevent the sapphire substrate from warping, and if the sapphire substrate has a greater thickness, the substrate is warped due to a difference in thermal expansion between the nitride semiconductor and the sapphire.

The acceleration voltage for ion implantation is preferably 1 keV or more and 1 MeV or less. This is to make the formation depth of the intermediate layer appropriate and keep the crystal state of the sapphire substrate surface favorable. If it is 1 keV or less, the position where the intermediate layer is formed is too shallow, which adversely affects the crystallinity of the sapphire substrate surface. Conversely, at 1 MeV or more, the damage caused by the implanted ions to the crystal on the substrate surface cannot be ignored. In addition, the position at which the intermediate layer is formed is too deep, and the strain buffering effect of the intermediate layer is reduced, or sapphire or the like remaining on the back surface of the nitride semiconductor crystal for device after the sapphire substrate is peeled becomes thicker, and polishing for removal is performed. This is because it takes time.

The dose amount is 1 × 10 ¹⁵ cm ⁻² or more and 1 × 10 5
^It is preferably ¹⁹ cm- ² or less. This is for suppressing the damage of the crystal on the surface of the sapphire substrate to a negligible range, relaxing the warp, and generating voids sufficient for buffering the strain and peeling the substrate. Dose amount is 1 × 10 ¹⁵ c
In the case of m ⁻² or less, the density of voids is low, so that the strain buffering effect is small, and it is insufficient to peel the substrate. Conversely, if the dose is 1 × 10 ¹⁹ cm ⁻² or more, the damage caused by the implanted ions to the crystal on the surface of the sapphire substrate cannot be ignored.

[0038]

(Embodiment 1) FIGS. 1A to 1E are process diagrams showing one embodiment of a method for manufacturing a nitride semiconductor substrate according to the present invention.

As a substrate, a sapphire substrate (having a diameter of about 50
mm and a thickness of about 0.33 mm) (FIG. 1).
(A)).

Hydrogen ions are implanted into the sapphire substrate 1. The condition is that the dose is 1 × 10 ¹⁷ cm ^-2 ,
At an acceleration voltage of 100 keV, an intermediate layer 2 having a thickness of 0.1 μm is formed at a depth of 0.5 μm from the surface of the sapphire substrate 1. A single crystal layer is maintained in the vicinity 1a of the surface of the sapphire substrate 1 into which hydrogen has been implanted.
There is an implanted layer of hydrogen, that is, an intermediate layer 2 underneath (a) (FIG. 1 (b)).

On the surface of the sapphire substrate 1a, a 2 μm GaN single crystal serving as the device nitride semiconductor layer 3 was epitaxially grown by metal organic chemical vapor deposition (MOVPE). As a growth furnace, a horizontal atmospheric pressure MOVPE furnace was used, and ammonia gas and trimethylgallium were used as raw materials, and a mixed gas of hydrogen and nitrogen was used as a carrier gas.

First, the substrate is heated to 1100 ° C. in a hydrogen atmosphere to clean oxides and the like on the surface. Subsequently, the substrate temperature is lowered to 550 ° C., and GaN is grown to 20 nm, and further, the substrate temperature is raised to 1050 ° C., and GaN is grown to 2 μm.

When one of the GaN epitaxial growth substrates taken out of the MOVPE furnace was split and its cross section was observed with a scanning electron microscope, it was observed that many fine voids were generated in the intermediate layer.

The manufactured GaN epitaxial growth substrate 4
A GaN single crystal is epitaxially grown to a thickness of 300 μm using the HVPE method. The apparatus uses a horizontal normal pressure HVPE furnace. Ammonia gas and metal Ga as raw materials and H
GaCl obtained by reacting Cl gas at 850 ° C. is used, and hydrogen gas is used as a carrier gas. Growth temperature 105
0 ° C. and the growth rate was 80 μm / h (FIG. 1).
(C)).

After the completion of the epitaxial growth, the part from the intermediate layer 2 to the sapphire substrate 1b is naturally separated from the intermediate layer (void layer) 2 in the cooling process from the growth temperature to room temperature (FIG. 1D).

The thin sapphire layer 1a remaining on the back surface of the obtained nitride semiconductor layer for device 3 made of GaN single crystal
Was removed by polishing to obtain a GaN free-standing single crystal substrate having a diameter of about 50 mm and a thickness of about 300 μm. This substrate was colorless and transparent, and had no cracks or warpage (FIG. 1 (e)). (Embodiment 2) FIGS. 2A to 2F are process diagrams showing another embodiment of the method for manufacturing a nitride semiconductor epitaxial wafer of the present invention.

As a substrate, a sapphire substrate (having a diameter of about 50
A GaN single crystal serving as the peeling nitride semiconductor layer 11 is epitaxially grown to a thickness of 2 μm using a metal organic chemical vapor deposition method (MOVPE method) to a thickness of about 0.33 mm.
A horizontal atmospheric pressure MOVPE furnace is used as a growth furnace, and ammonia gas and trimethylgallium are used as raw materials, and a mixed gas of hydrogen and nitrogen is used as a carrier gas.

The sapphire substrate 10 is placed in a hydrogen atmosphere at 11
It was heated to 00 ° C. to clean oxides and the like on the surface.
Subsequently, the temperature of the substrate was lowered to 550 ° C., and GaN was grown to a thickness of 20 nm.
Is grown to about 2 μm (FIG. 2A).

Hydrogen is ion-implanted into the nitride semiconductor layer 11 for separation made of the grown GaN single crystal layer. The conditions are a dose of 1 × 10 ¹⁷ cm ⁻² and an accelerating voltage of 10
0 keV, an intermediate layer 12 having a thickness of about 0.1 μm and a depth of about 0.5 μm from the surface of the nitride semiconductor layer 11 for separation.
To form A single crystal layer is maintained on the surface of the nitride semiconductor layer 11 for separation into which hydrogen has been implanted, and a hydrogen implantation layer (intermediate layer) 12 exists below the surface of the nitride semiconductor layer 11 for separation. (FIG. 2B).

The hydrogen-implanted GaN epitaxial growth substrate 13 is heat-treated at 800 ° C. for 30 minutes in an ammonia atmosphere. When a cross section of the same sample as the GaN epitaxial growth substrate 13 after the heat treatment was observed with a scanning electron microscope, the intermediate layer was a void layer in which many fine voids were generated (FIG. 2C).

On the heat-treated GaN epitaxial growth substrate 13a, a GaN single crystal serving as the device nitride semiconductor layer 14 is epitaxially grown to about 300 μm by HVPE. The apparatus used was a horizontal normal pressure HVPE furnace. As a raw material, GaCl obtained by reacting ammonia gas and metal Ga with HCl gas at 850 ° C. is used, and SiH ₂ Cl ₂ is simultaneously flowed to obtain an n-type conductivity type. Hydrogen gas is used as a carrier gas. When the growth temperature was set to 1050 ° C., the growth rate was 80 μm / h (FIG. 2).
(D)).

After the completion of the epitaxial growth, the intermediate layer 12 consisting of voids is formed in a cooling process from the growth temperature to room temperature.
After that, the part from the intermediate layer 12 to the sapphire substrate 10 is spontaneously separated (FIG. 2E).

The removal nitride semiconductor layer 11a remaining on the back surface of the obtained device nitride semiconductor layer 14 made of n-type GaN single crystal is polished and removed to obtain a diameter of about 5 mm.
An n-type GaN free-standing single crystal substrate having a thickness of 0 mm and a thickness of about 300 μm was obtained. This substrate was colorless and transparent, and had no cracks or warpage (FIG. 2 (f)). (Embodiment 3) FIG. 3 is a schematic structural view of a laser diode using a nitride semiconductor epitaxial wafer of the present invention.

A case in which an LD element having a structure as shown in FIG. 3 is formed on the n-type GaN free-standing single crystal substrate obtained in Example 2 by MOVPE will be described.

The LD structure is composed of a Si-doped GaN buffer layer (about 2 μm, n = 5 × 10 ¹⁷ cm ⁻³ ) 22 and a Si-doped Al
_0.07 Ga _0.93 N cladding layer (about 1.0 μm thick, n = 5
× 10 ¹⁷ cm ⁻³ ) 23, Si-doped GaN SCH layer (thickness: about 0.1 μm, n = 1 × 10 ¹⁷ cm ⁻³ ) 24, undoped In _0.2 Ga _0.8 N / In _0.05 Ga _0.95 N multiple quantum well layer (3 nm / 5 nm × 3) 25, Mg-doped A
l _0.2 Ga _0.8 N overflow prevention layer (thickness: about 20 n
m, p = 2 × 10 ¹⁹ cm ⁻³ ) 26, Mg-doped GaN light confinement layer (thickness: about 0.1 μm, p = 2 × 10 ¹⁹ cm ⁻³ ) 2
7, Mg-doped Al _0.07 Ga _0.93 N cladding layer (thickness: about 0.5 μm, p = 2 × 10 ¹⁹ cm ⁻³ ) 28; Mg-doped GaN contact layer (thickness: about 50 nm, p = 2 × 10 ¹⁹⁾
cm ⁻³ ) 29.

The width of the p-side is about 4 μm by dry etching.
A ridge structure having a depth of about 0.4 μm and a depth of about 0.4 μm was manufactured, and current constriction was performed. A Ni / Au electrode 30 was formed on the ridge to form a p-type ohmic electrode. A Ti / Al electrode 20 was formed on the entire surface of the backside of the self-standing GaN substrate to form an n-type ohmic electrode. A high reflection coating film made of TiO ₂ / SiO ₂ was formed on both end surfaces. Element length is about 50
By setting the thickness to 0 μm, an LD element was obtained.

When power is supplied to such an LD element, the threshold current density is about 4.5 kA / cm ² and the threshold voltage is about 5.5.
And continuous oscillation at room temperature. Further, since the crystal defects were reduced, the life of the LD element was excellent at 5,000 hours when driven at 30 mW at an air temperature of 25 ° C.

Further, the self-standing substrate according to the present invention has no warpage and is easy to cleave as compared with the case where an LD structure is formed on a sapphire substrate. And good characteristics were obtained. Embodiment 4 Next, a light emitting diode using the nitride semiconductor epitaxial wafer of the present invention will be described. FIG.
FIG. 1 is a schematic structural view of a light emitting diode using a nitride semiconductor epitaxial wafer of the present invention. This light emitting diode is formed on the GaN epitaxial growth substrate selected in the steps from FIG. 2A to FIG.
An ED structure is formed, a Ni / Au layer is vacuum-deposited on the LED structure, an Al substrate is fused on the Ni / Au layer at 660 ° C. in a nitrogen atmosphere in an electric furnace, and then a sapphire substrate Was removed from the intermediate layer, and a Ti / Al electrode was formed on the surface where the sapphire substrate had been removed and removed.

The structure of the light emitting diode thus obtained is such that the Ni / Au layer 41 and the Mg
Doped GaN layer (50 nm thick, p = 2 × 10 ¹⁹ c
m ⁻³ ) 42, Mg-doped Al _0.2 Ga _0.8 N layer (thickness 0.5 μm, p = 2 × 10 ¹⁹ cm ⁻³ ) 43, undoped quantum well layer (In _0.2 Ga _0.8 N) 44, Si-doped Ga
N cladding layer (thickness 3 μm, n = 5 × 10 ¹⁷ cm ⁻³ ) 4
5 and an n-type electrode (Ti / Al electrode) 46.

When the LED element was energized, the emission wavelength was 450 nm, and the emission output was about 7 m when 20 mA was applied.
W. Unlike a light-emitting diode grown on a sapphire substrate without an intermediate layer, it has few crystal defects and good heat dissipation characteristics, so the reliability of the element is high. In an environment of 40 ° C. and 100% humidity in a resin molded state , 20m
When a continuous energization test was performed for 1000 hours at A,
Even after the current supply for 00 hours, the light emission output was almost the same as the initial state.

In the above-described embodiment, a case was described in which a sapphire substrate or a sapphire substrate having a nitride semiconductor formed on the surface was used as the substrate and hydrogen was used as the ion to be implanted. Ions may be used.

As the epitaxial growth method of the nitride semiconductor, there are various known methods such as the MOVPE method, the HVPE method and the MBE method, which can be used. A two-step growth method using a low-temperature buffer layer of gallium nitride or aluminum nitride, a method of directly growing at a high temperature,
Various known methods such as an ELO method and a FIELO method for reducing dislocations by lateral growth using microfabrication and regrowth during growth can be used.

The intermediate layer may be formed as a void layer either during the temperature increase before the growth of the other nitride semiconductor layer, during the cooling, or after the growth,
Alternatively, it can be performed in all or some of the steps. Alternatively, heat treatment may be performed after ion implantation and before the start of growth of another nitride semiconductor layer.

The sapphire substrate can be peeled off from the intermediate layer by various methods such as peeling by heat treatment after growth, peeling by a nitrogen jet from a side surface, peeling by a water jet, and peeling by laser irradiation.

In the fourth embodiment, peeling was performed after attaching an Al substrate. However, for example, a metal substrate such as a Si substrate, a glass substrate, a metal substrate such as Cu, or a thin film having good thermal conductivity such as AlN was laminated. A substrate such as a substrate suitable for a subsequent element manufacturing process can be used.

Here, conventionally, epitaxial growth of a nitride semiconductor has been performed on a substrate such as sapphire having a significantly different coefficient of thermal expansion, so that many crystal defects occur, and when a thick film is grown, warpage and cracks occur. There was a problem. In order to fundamentally solve this problem, the development of nitride semiconductor substrates has also been carried out, but since the production of nitride semiconductor substrates was performed under ultra-high pressure, the cost was extremely high,
Only about 10 mm was obtained. Also, HVP
It is more realistic than a method of obtaining a GaN free-standing substrate by growing a GaN thick film of about several hundred μm on a sapphire substrate by the E method and then removing the sapphire substrate, but the heat between the sapphire substrate and the nitride semiconductor is more realistic. Warpage and cracks due to the difference in expansion coefficient occur, and crystal defects are quite large.
There are no practical methods for removing the sapphire substrate, and there are problems such as warpage remaining after the removal.

However, according to the present invention, the intermediate layer formed in the substrate by hydrogen implantation and heat treatment functions as a buffer layer for reducing the difference in thermal expansion coefficient.
It is possible to easily obtain a high-quality nitride semiconductor epitaxial wafer in which crystal defects, which have conventionally been a problem, are significantly reduced and warpage and cracks are eliminated. In addition, the nitride semiconductor layer is separated from the substrate with the intermediate layer as a boundary, so that a large-area flat freestanding epitaxial wafer of the nitride semiconductor can be easily obtained.

[0068]

In summary, according to the present invention, the following excellent effects can be obtained.

A method for manufacturing a nitride semiconductor epitaxial wafer having few crystal defects and free from warpage and cracks and the provision of a nitride semiconductor epitaxial wafer can be realized.

[Brief description of the drawings]

FIGS. 1A to 1E are process diagrams showing an example of a method for manufacturing a nitride semiconductor epitaxial wafer according to the present invention.

2 (a) to 2 (f) are process diagrams showing another embodiment of the method for manufacturing a nitride semiconductor epitaxial wafer of the present invention.

FIG. 3 is a schematic structural view of a laser diode using the nitride semiconductor epitaxial wafer of the present invention.

FIG. 4 is a schematic structural view of a light emitting diode using the nitride semiconductor epitaxial wafer of the present invention.

[Explanation of symbols]

 1, 1a, 1b Sapphire substrate 2 Intermediate layer 3 Device nitride semiconductor layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA03 AA11 AA13 AA17 AA18 BA02 BA08 BA11 BA38 CA01 DA03 DA08 FA10 JA01 JA06 LA11 5F041 AA40 CA05 CA34 CA40 CA46 CA57 CA65 CA67 CA71 CA73 CA82 CA92 5F045 AA04 AB14 AB18 AC08 AC12 AD14 AF03 AF09 BB12 BB16 CA10 CA12 DA53 HA05 5F073 AA45 AA74 CA07 CB05 CB07 DA05 DA14 DA35

Claims (14)

[Claims] An intermediate layer having a lower mechanical strength than the sapphire substrate is formed near the surface of the sapphire substrate, and a nitride semiconductor layer for a device is epitaxially grown on the sapphire substrate on which the intermediate layer is formed. Of manufacturing a nitride semiconductor epitaxial wafer. 2. A nitride semiconductor layer for separation is formed on a sapphire substrate, and an intermediate layer whose mechanical strength is weaker than that of the nitride semiconductor layer for separation is formed near a surface of the nitride semiconductor layer for separation. A method for manufacturing a nitride semiconductor epitaxial wafer, comprising epitaxially growing a device nitride semiconductor layer on the peeling nitride semiconductor layer on which the intermediate layer is formed. 3. The method for manufacturing a nitride semiconductor epitaxial wafer according to claim 1, wherein the thickness of the device nitride semiconductor layer is 10 μm or less. 4. The intermediate layer according to claim 1, wherein ions are implanted from a surface of the nitride semiconductor layer for separation or a surface of the sapphire substrate to a depth at which the intermediate layer is to be formed. Of manufacturing a nitride semiconductor epitaxial wafer. 5. The method for manufacturing a nitride semiconductor epitaxial wafer according to claim 4, wherein at least one of hydrogen ions, nitrogen ions, and oxygen ions is used as said ions. 6. An accelerating voltage for ion implantation is 1 k
6. The method for producing a nitride semiconductor epitaxial wafer according to claim 5, wherein the nitride semiconductor epitaxial wafer has an eV of not less than 1 MeV and a dose of the ions of not less than 1 × 10 ¹⁵ cm ^{−2 and not} more than 1 × 10 ¹⁹ cm ⁻² . 7. After the ion implantation, heat treatment is performed to recover damage caused by ion implantation of the surface crystal layer of the sapphire substrate or the nitride semiconductor layer for exfoliation, and to form minute voids and voids near the surface. The method for manufacturing a nitride semiconductor epitaxial wafer according to any one of claims 4 to 6, wherein the intermediate layer is formed by forming an aggregate. 8. The method for manufacturing a nitride semiconductor epitaxial wafer according to claim 7, wherein the size, quantity, density, distribution, and the like of the voids and the aggregate of the voids are controlled by heat treatment. 9. The method of manufacturing a nitride semiconductor epitaxial wafer according to claim 7, wherein the heat treatment is performed in an atmosphere of H ₂ or NH ₃ or a mixture of both. 10. The method for manufacturing a nitride semiconductor epitaxial wafer according to claim 1, wherein a portion from said intermediate layer to said sapphire substrate is removed by separating said intermediate layer from said intermediate layer. 11. The device according to claim 10, wherein a portion from the intermediate layer to the sapphire substrate is peeled off and removed from the intermediate layer after attaching another substrate to the surface of the nitride semiconductor layer for device. Of manufacturing a nitride semiconductor epitaxial wafer. 12. The method of manufacturing a nitride semiconductor epitaxial wafer according to claim 11, wherein a semiconductor such as Si, a high thermal conductive substrate such as AlN, or a metal such as Cu or Al is used as the other substrate. 13. A part of the sapphire substrate remaining in the device nitride semiconductor layer from which the sapphire substrate has been removed or a part of the peeling nitride semiconductor layer remaining in the device nitride semiconductor from which the sapphire substrate has been removed. The method for producing a nitride semiconductor epitaxial wafer according to claim 10, wherein the nitride semiconductor epitaxial wafer is removed by a method such as polishing. 14. produced by the method according to any of claims _{1 13, In x Al y Ga} 1-xy N (x, y
≧ 1, x + y ≦ 1) A nitride semiconductor epitaxial wafer having a composition of: