JP2004091278A - Method of manufacturing semiconductor crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high-quality semiconductor crystal (single crystal) independent of a substrate. <P>SOLUTION: Light used in a crystal separation process is, e.g. light emitted from a Q-switched Nd:YAG laser apparatus or the like, and its irradiation conditions are, e.g. an emission wave length of 355 nm, irradiation intensity of 400-600 mJ/cm<SP>2</SP>, and a temperature of the substrate of 1,150-600°C. Since such laser light functions as an energy liquefying or vaporizing the semiconductor crystal locally with a shallow depth of a few μm at the vicinity of the interface with the substrate, the substrate and the semiconductor crystal are well exfoliated at about the growth temperature of a desired semiconductor crystal formed from a group III nitride compound semiconductor or the like. Thus, the generation of stress acting on the semiconductor crystal and caused by the difference in thermal expansion coefficients and the effect of temperature down is effectively suppressed and the high-quality thick-layer semiconductor crystal without defects and cracks is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor crystal manufacturing method for obtaining an independent semiconductor crystal by separating a substrate used for crystal growth of a semiconductor from a semiconductor crystal grown on the substrate. Such an independent semiconductor crystal obtained according to the present invention is useful as a substrate material of a semiconductor device.
[0002]
[Prior art]
As a conventional technique for obtaining a single crystal such as a group III nitride compound semiconductor useful for a crystal growth substrate or the like, for example, a thick group III nitride compound semiconductor is formed on a base substrate such as sapphire. A method of performing any one of the following steps A to C after removing a semiconductor from a crystal growth apparatus is known.
[0003]
(A) An etching-removable substance (eg, zinc oxide) formed or arranged in advance between a base substrate and a desired semiconductor crystal is used. That is, peeling is performed by etching using such a substance as a base point.
As such a conventional technique, for example, a technique described in Patent Literature 1 below relating to a method of manufacturing a group III nitride semiconductor is generally widely known.
[0004]
(B) The underlying substrate is removed by a polishing process.
(C) Laser light is applied to the vicinity of the interface between the base substrate and the desired semiconductor crystal to be separated.
[0005]
[Patent Document 1]
JP-A-7-202265
[0006]
[Problems to be solved by the invention]
However, in any of the above-described conventional techniques, since the separation process or the removal process is performed after the desired semiconductor crystal is taken out from the crystal growth apparatus, the temperature of the base substrate or the semiconductor crystal is increased immediately after the completion of the crystal growth. It falls significantly compared to.
As a result, when starting any one of the above-described steps A to C, for example, as illustrated in FIG. 4, whether a desired semiconductor crystal has already been warped, cracked, or defective, or During execution of any one of steps C to C, a desired semiconductor crystal is warped, cracked, or defective.
[0007]
The cause of the occurrence of the warpage, crack or defect is a relatively large difference in thermal expansion coefficient between the base substrate and the semiconductor crystal. However, any one of the above-described steps A to C can be performed. And, as the underlying substrate that can eliminate the difference between these two thermal expansion coefficients, for example, it is not impossible to use the same or similar semiconductor crystal, etc., but within the cost range that is industrially suitable, A substance that can be used as a material for such an undersubstrate has not been found yet. For this reason, it is currently industrially difficult to obtain a sufficiently high-quality semiconductor crystal based on the above-mentioned conventional technology.
[0008]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to use a different material having a different coefficient of thermal expansion as a base substrate (first crystal growth substrate) and obtain a high-quality material independent of the base substrate. Is to obtain a suitable semiconductor crystal.
[0009]
Means for Solving the Problems, Functions and Effects of the Invention
In order to solve the above-mentioned problems, the following means are effective.
That is, a first means of the present invention is a semiconductor crystal manufacturing process for obtaining an independent semiconductor crystal by separating a substrate used for crystal growth of a semiconductor from a semiconductor crystal grown on the substrate. A crystal growth step of growing a semiconductor crystal on a substrate; and a crystal separation step of separating the substrate and the semiconductor crystal by irradiating light near an interface between the substrate and the semiconductor crystal. In the separation step, the temperature of the substrate is maintained at substantially the same temperature as or around the crystal growth temperature of the semiconductor crystal in the crystal growth step, and either the semiconductor crystal or the substrate has a relatively large band gap. From the side, light having a wavelength corresponding to the band gap between the band gap of the semiconductor crystal and the band gap of the substrate is irradiated.
[0010]
FIG. 1 is a state transition diagram of a group III nitride-based compound semiconductor (desired semiconductor crystal) showing the action of the crystal separation step of the present invention. As the light in FIG. 1 irradiated for the above-mentioned purpose, for example, output light from a Q-switched Nd: YAG laser device or the like can be used. As one example thereof, for example, a laser beam under the following conditions is useful.
(1) Emission wavelength: 355 nm
(2) Beam diameter: 7mm
(3) Irradiation intensity: 400 to 600 mJ / cm ²
(4) Irradiation direction: substantially perpendicular to the interface with the semiconductor crystal from the base substrate side (5) Irradiation method: scanning (6) Temperature of base substrate: 1150 ° C to 600 ° C (temperature immediately before laser irradiation)
[0011]
Such a laser beam acts as energy for liquefying or vaporizing the semiconductor crystal in the vicinity of the interface between the underlying substrate and the semiconductor crystal in a depth direction, which is locally shallow and is as thin as several μm. The physical action principle of such a laser beam on a semiconductor crystal is as follows.
[0012]
That is, since the band gap of the material on the incident side is larger than the energy of each incident photon, the photon energy of the laser light is basically not absorbed by the material on the incident side. For this reason, the laser light transmits through the material on the incident side (the base substrate side in the above case). However, the light that reaches the interface between the underlying substrate and the semiconductor crystal is incident on a material having a band gap smaller than the energy of the photon, and the photon energy of the light is immediately absorbed by the material. You.
[0013]
Therefore, according to the first means of the present invention, the base substrate and the semiconductor crystal can be separated from each other at around the growth temperature of a desired semiconductor crystal formed from a group III nitride compound semiconductor or the like. The generation of stress acting on a desired semiconductor crystal can be effectively suppressed based on the difference between the thermal expansion coefficients and the temperature drop effect, and thus, by this action, for example, as shown in FIG. A high-quality semiconductor crystal can be obtained with no thick film.
[0014]
Further, according to the means of the present invention, since light is irradiated at a high temperature, it is possible to separate a semiconductor crystal of significantly higher quality than the conventional one from the underlying substrate even with a laser light having a lower irradiation intensity than the conventional one. is there.
For example, when an independent gallium nitride (GaN) single crystal is manufactured, even if the temperature is lowered from the crystal growth temperature to about 600 ° C., a single crystal of clearly higher quality than before can be obtained. In other words, the peripheral temperature of the crystal growth temperature of the semiconductor crystal in the crystal growth step of the present invention includes up to this temperature.
[0015]
Further, the second means of the present invention is the first means, wherein a buffer layer laminating step of laminating a buffer layer for reducing a lattice constant difference between the substrate and the semiconductor crystal at the interface between the substrate and the semiconductor crystal. It is to provide.
According to this means, the difference in lattice constant between the substrate and the semiconductor crystal is effectively reduced, so that a high-quality semiconductor crystal can be obtained.
[0016]
The third aspect of the present invention, in the crystal growth step of the first or second means, as a semiconductor crystal, whether or not added impurity is added, the main component "Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) ”is to grow a group III nitride compound semiconductor.
[0017]
The above-mentioned semiconductor materials are not particularly limited. However, for example, a semiconductor substrate or a semiconductor light-emitting device can be applied when you want to configure a group III nitride-based compound semiconductor, as a well stackable semiconductor, at least _{Al x Ga y In 1-x} -y N (0 ≦ Group III nitride-based compound semiconductors composed of binary, ternary or quaternary semiconductors represented by x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). Some of these group III elements may be replaced with boron (B), thallium (Tl), etc., and some of nitrogen (N) may be replaced with phosphorus (P), arsenic (As), antimony ( Sb), bismuth (Bi) or the like may be used.
[0018]
Further, when an n-type group III nitride compound semiconductor layer is formed using these semiconductors, Si, Ge, Se, Te, C, or the like can be added as an n-type impurity. As the p-type impurity, Zn, Mg, Be, Ca, Sr, Ba, or the like can be added. These impurities may be added in a mixture of both p-type and n-type impurities. By using these semiconductor-forming elements, a desired high-quality semiconductor crystal can be obtained.
[0019]
According to a fourth aspect of the present invention, in the crystal separation step of any one of the first to third means, light is irradiated from the substrate side.
For example, when the material of the base substrate is sapphire and gallium nitride (GaN) is selected as the material of the semiconductor crystal, the bandgap of the base substrate becomes larger. Laser light can be effectively absorbed by the semiconductor crystal located near the interface with the semiconductor crystal.
[0020]
In a fifth aspect of the present invention, in the crystal separation step of any one of the first to third means, light is irradiated from the semiconductor crystal side.
This method is effective when the underlying substrate has a smaller band gap, contrary to the above-described means.
[0021]
Examples of such a material for the base substrate having a relatively small band gap include silicon (Si) and gallium arsenide (GaAs).
That is, a sixth means of the present invention is that, in the fifth means, silicon (Si) or gallium arsenide (GaAs) is used as a material of the substrate.
[0022]
According to a seventh aspect of the present invention, in the crystal growth step of any one of the first to sixth means, a semiconductor crystal is grown using a lateral growth method (ELO growth method). Is to form a cavity locally or periodically in the vicinity of the interface between the semiconductor crystal and the substrate by dispersing in the lateral direction.
[0023]
According to this method, the bonding area between the semiconductor crystal and the substrate is reduced due to the formation of the cavity, and the stress acting due to a difference in lattice constant and the like is concentrated at the bonding portion between the two. At this time, on the desired semiconductor crystal side, stress is unlikely to act on the contrary, and at the same time, the irradiation efficiency of light to the joint surface between the two is improved with a decrease in the joint area. In addition, the base substrate and the semiconductor crystal can be efficiently separated, and a high-quality semiconductor crystal can be obtained.
[0024]
Further, an eighth means of the present invention is characterized in that, in the crystal separation step of any one of the first to seventh means, light is irradiated in the same apparatus as the crystal growth apparatus which executed the crystal growth step. is there.
[0025]
According to such a means, it is not necessary to take out the semiconductor crystal once out of the crystal growth apparatus before irradiating the light, so that the temperature of the semiconductor crystal can be easily maintained at the temperature immediately after the completion of the crystal growth. . That is, according to the above means, it is possible or easy to maintain the temperature of the substrate in the crystal separation step of the present invention at substantially the same temperature as the crystal growth temperature of the semiconductor crystal in the crystal growth step or at a temperature around the same.
[0026]
In addition, as a method for growing these semiconductor layers by crystal, halide vapor phase epitaxy (HVPE), metal organic vapor phase epitaxy (MOVPE) and the like are effective.
By the means of the present invention described above, the above problems can be effectively or rationally solved.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on specific examples. However, the present invention is not limited to the embodiments described below.
〔Example〕
(1) Crystal growth step (a) Buffer layer lamination step An AlN low-temperature deposition buffer layer is formed on a sapphire substrate by MOVPE at about 0.03 μm at about 400 ° C.
(B) Next, GaN is grown at about 1150 ° C. on the AlN low-temperature deposition buffer layer by MOVPE at about 2 μm.
(C) Further, GaN (desired semiconductor crystal) is grown on the first GaN layer at about 1000 ° C. at about 250 μm by HVPE.
[0028]
(2) Crystal separation step After that, while maintaining the desired semiconductor crystal growth temperature, a laser beam is introduced into the growth chamber (reaction tube), and the base substrate (sapphire substrate) and the semiconductor crystal (GaN single crystal) are introduced. ).
[0029]
FIG. 2 is a cross-sectional view of a crystal growth apparatus 200 developed for performing the present crystal separation step. The present crystal growth apparatus 200 is provided with a laser light intake window 210, which is characterized by being designed so that a sample (target object) can be irradiated with laser light from this window. .
[0030]
The wavelength of the irradiation light can be suitably or optimally adjusted so that the irradiation light efficiently transmits through the base substrate and is efficiently absorbed by a desired semiconductor crystal. For example, the band gap of the desired semiconductor crystal (typical) and E _1, when the band gap of the base substrate (typical) and E _2, by preparing a laser beam having a wavelength λ which satisfies the following formula (1) Good.
(Equation 1)
λ = ch / E,
E = (E ₁ + E ₂ ) / 2 (1)
[0031]
Here, c is the speed of light and h is Planck's constant. Needless to say, the above band gaps (representative values) should be values under the temperature conditions at the time of performing the laser beam irradiation process. It is more desirable to consider that the temperature conditions of the underlying substrate and the semiconductor crystal at the time of performing the irradiation process may change with time even during the execution of the irradiation process.
[0032]
As laser light to be actually irradiated, for example, output light from a Q-switched Nd: YAG laser device or the like can be used. More specifically, for example, laser light under the following conditions is useful.
(1) Emission wavelength: 355 nm
(2) Beam diameter: 7mm
(3) Irradiation intensity: 400 to 600 mJ / cm ²
(4) Irradiation direction: substantially perpendicular to the interface with the semiconductor crystal from the base substrate side (5) Irradiation method: scanning
For example, by sequentially performing the manufacturing steps as described above, a high-quality semiconductor crystal (GaN single crystal) having a thick film substantially free from defects and cracks can be obtained.
[0034]
[Modification 1]
In the first embodiment, a sapphire substrate is used as a base substrate. However, a material having a smaller band gap than a group III nitride compound semiconductor, such as silicon (Si) or gallium arsenide (GaAs), may be used. It can also be used as a base substrate. In such a case, after the crystal growth step of the group III nitride-based compound semiconductor is completed, while the base substrate is maintained at a temperature near the crystal growth temperature, the desired semiconductor crystal side (ie, the group III nitride-based compound semiconductor (From the side). Irradiation light can be transmitted through a desired semiconductor crystal efficiently and its wavelength can be suitably or optimally adjusted so as to be efficiently absorbed by the underlying substrate. The base substrate and the semiconductor crystal can also be satisfactorily separated from each other by absorbing light to the side.
[0035]
[Modification 2]
Hereinafter, in the crystal growth step of the present invention, a semiconductor crystal is grown using a lateral growth method (ELO growth method), so that the junction area between the semiconductor crystal and the substrate at the interface is reduced. A method for manufacturing a semiconductor crystal will be described.
[0036]
As a technique for growing a semiconductor crystal using a lateral growth method (ELO growth method), for example, Japanese Patent Application Laid-Open Nos. 11-145516, 2001-313259, 2001-160627 And Japanese Unexamined Patent Application Publication No. 2000-091252, and Japanese Patent Application Laid-Open Publication No. 2000-091253 are widely known in general.
[0037]
In these techniques, high-quality semiconductor crystals can be grown by lateral growth, and at the same time, local or periodic cavities are formed in the vicinity of the interface between the underlying substrate and the semiconductor crystals, dispersed in the horizontal direction. As a result, the junction area between the semiconductor crystal and the substrate at the interface between the two may be reduced.
[0038]
Therefore, when a semiconductor crystal is grown using a lateral growth method (ELO growth method) according to these techniques, the bonding area between the semiconductor crystal and the substrate at the interface between the semiconductor crystal and the substrate can be reduced. Are concentrated, and it becomes difficult for stress to act on a desired semiconductor crystal. At the same time, since the joint area between the two is reduced, the efficiency of light irradiation on the joint surface between the two is improved. Therefore, a synergistic effect of these actions allows the base substrate and the semiconductor crystal to be efficiently separated. At the same time, a high-quality semiconductor crystal can be obtained.
[0039]
FIG. 3 is a schematic cross-sectional view of the semiconductor crystal according to the present embodiment. As described above, the procedure of the lateral growth method that can be used in combination with the method of the first embodiment (that is, the desired procedure) Of manufacturing a semiconductor crystal).
Hereinafter, each manufacturing process will be described in the order of execution.
[0040]
1. In this embodiment, a seed layer (a group III nitride-based compound semiconductor) composed of a first seed layer (AlN buffer layer 302) and a second seed layer (GaN layer 303) is formed using an organic metal compound vapor phase. The film was formed by vapor phase growth by a growth method (hereinafter, referred to as “MOVPE”). The gases used there were ammonia (NH ₃ ), carrier gas (H ₂ or N ₂ ), trimethylgallium (Ga (CH ₃ ) ₃ , hereinafter referred to as “TMG”), and trimethylaluminum (Al (CH ₃ ) ₃ ). , Hereinafter referred to as “TMA”).
[0041]
First, a sapphire substrate 301 (underlying substrate) of 1 inch square and about 250 μm thick was cleaned by organic cleaning and heat treatment (baking). Using the a-plane of the single crystal base substrate 301 as a crystal growth surface, H ₂ was supplied at 10 L / min, NH ₃ was supplied at 5 L / min, TMA was supplied at 20 μmol / min, and the AlN buffer layer 302 (seed layer) was supplied. The first layer) was grown to a thickness of about 200 nm. At this time, the crystal growth temperature was about 400 ° C.
[0042]
Further, the temperature of the sapphire substrate 301 was raised to 1000 ° C., H ₂ was introduced at 20 L / min, NH ₃ was introduced at 10 L / min, TMG was introduced at 300 μmol / min, and the GaN layer 303 having a thickness of about 1.5 μm was introduced. (Seed layer second layer) was formed (FIG. 3A).
[0043]
2. Erosion Debris Forming Step Next, using a hard bake resist mask, a striped erosion debris having an arrangement period L ≒ 20 μm was formed by selective dry etching using reactive ion etching (RIE) (FIG. 3). (B)).
[0044]
That is, the erosion debris having a substantially rectangular cross section was formed by etching the substrate in a stripe shape with a stripe width (seed width S) Ｓ5 μm and a wing width W ≒ 15 μm until the substrate was etched by about 0.1 μm. The above resist mask was formed such that the side wall of the erosion debris remaining in the stripe shape was the {11-20} plane of the GaN layer 303 (second seed layer).
By this etching, a striped erosion debris having a seed layer including a GaN layer 303 (seed layer second layer) and an AlN buffer layer 302 (seed layer first layer) on the flat top is formed substantially periodically, Part of the sapphire substrate 301 was exposed at the valley of the wing.
[0045]
3. Crystal Growth Step Next, the target semiconductor crystal A made of a GaN single crystal was formed by HVPE using the exposed surface of the erosion debris remaining in the stripe shape as the first crystal growth surface.
[0046]
Finally, the target semiconductor crystal A is grown to about 250 μm. At this time, GaN grows in the horizontal direction and the vertical direction in the initial stage of growth, and once the parts are connected and flattened into a series of substantially planar shapes, the GaN crystal grows in the vertical direction.
In the HVPE method, ammonia (NH ₃ ) was used as a group V source material, and GaCl obtained by reacting Ga and HCl was used as a group III source material.
[0047]
Thus, the lateral sides of the seed layer were mainly filled by the lateral epitaxial growth, and thereafter, the semiconductor crystal A (GaN single crystal) having the target film thickness was obtained by the vertical growth (FIG. 3C). In addition, the code | symbol R in a figure has shown "cavity".
By separating the GaN single crystal thus obtained from the base substrate 301 without lowering the temperature based on the means of the present invention, a high-quality semiconductor crystal can be obtained.
[0048]
[Modification 3]
Further, in the above-described first embodiment, the method of irradiating the entire surface of the interface between the base substrate and the semiconductor crystal with laser light by scanning using a laser device having a beam diameter of about 7 mm has been described. The form may be surface irradiation.
In other words, the irradiation mode of the laser beam used for carrying out the present invention is not particularly limited as long as the irradiation mode can secure an irradiation intensity of about 400 to 600 mJ / cm ² .
[0049]
[Modification 4]
Note that the part to be separated is not necessarily limited to the vicinity of the interface between the base substrate and the semiconductor crystal stacked thereabove. For example, by laminating or arranging a material having a smaller band gap than any of the materials at an arbitrary position, light can be absorbed by the material and the material can be separated at the place. As such a material having a small band gap, for example, silicon (Si), gallium arsenide (GaAs), zinc oxide (ZnO), or the like can be used.
[0050]
[Other modifications]
The present invention is not limited to the above-described examples and modifications, and various other embodiments (modifications and combinations of techniques) can be considered. For example, the Group III nitride-based compound semiconductor, of course _Ga x _{In 1-x} N _(eg: Ga _{0.08 In 0.92} N) made of such a layer, other ternary or 4 of any mixed crystal ratio The original AlGaInN may be used. More specifically, _{"Al x Ga y In 1-x} -y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) " consisting formula ternary represented (GaInN, (AlInN, AlGaN) or a quaternary (AlGaInN) group III nitride compound semiconductor can also be used. Further, a part of nitrogen (N) of the compound may be replaced with a group V element such as P or As.
[0051]
Further, for example, when laminating a group III nitride-based compound semiconductor on a sapphire substrate, a buffer layer for correcting lattice mismatch with the sapphire substrate, as exemplified in the first embodiment, for example, in order to form with good crystallinity. Although it is preferable to form it, it is desirable to provide a buffer layer even when using another substrate. The buffer layer, III-nitride was formed at a low temperature-based compound semiconductor _{Al x Ga y In 1-x} -y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1), more preferably the _{Al x Ga 1-x N (} 0 ≦ x ≦ 1) is used.
[0052]
This buffer layer may be a single layer or a multilayer having different compositions and the like. The buffer layer may be formed at a low temperature of 300 to 500 ° C., or may be formed by MOCVD at a temperature of 1000 to 1100 ° C.
[0053]
Alternatively, a buffer layer made of AlN can be formed by a reactive sputtering method using a high-purity metal aluminum and a nitrogen gas as raw materials using a DC magnetron sputtering apparatus. Similarly general formula _{Al x Ga y In 1-x} -y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1, the composition ratio is optional) can form a buffer layer. Further, an evaporation method, an ion plating method, a laser ablation method, and an ECR method can be used. The buffer layer formed by physical vapor deposition is desirably formed at 200 to 600 ° C.
[0054]
Further, the temperature is desirably 300 to 600 ° C, and more desirably 350 to 450 ° C. When a physical vapor deposition method such as the sputtering method is used, the thickness of the buffer layer is desirably 100 to 3000 °. More preferably, it is 100 to 400 °, most preferably 100 to 300 °. As the multi-layer, for example, there is a method of alternately forming a layer composed of Al _x Ga _1-x N (0 ≦ x ≦ 1) and a GaN layer.
[0055]
Of course, may be a combination of these, multi-layer three or more Group III nitride compound semiconductor _{Al x Ga y In 1-x} -y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) may be laminated. Generally, the buffer layer is amorphous, and the Group III nitride compound semiconductor layer thereon is single crystal. The buffer layer and the single-crystal group III nitride compound semiconductor layer may be formed in a plurality of periods as one period, and the repetition may be an arbitrary period.
Alternatively, a high-temperature buffer layer may be formed on the low-temperature buffer layer, and the main group III nitride compound semiconductor may be formed thereon.
[0056]
In the buffer layer and the upper group III nitride-based compound semiconductor layer, a part of the composition of the group III element can be replaced with boron (B) or thallium (Tl), or a part of the composition of nitrogen (N) can be replaced. The present invention can be substantially applied even if it is replaced with phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi) or the like. Further, these elements may be doped to such an extent that they cannot be displayed in composition.
[0057]
For example, Al _x Ga _1-x N (0 ≦ x ≦ 1), which is a group III nitride compound semiconductor, is made of indium (In) or nitrogen (N) having an atomic radius larger than that of aluminum (Al) or gallium (Ga). By doping arsenic (As) having an atomic radius larger than that of ()), the expansion strain of the crystal due to the escape of nitrogen atoms may be compensated for by the compression strain to improve the crystallinity. In this case, since the acceptor impurity easily enters the position of the group III atom, a p-type crystal can be obtained by as-grown.
[0058]
When the buffer layer and the group III nitride compound semiconductor layer are formed in two or more cycles, it is more preferable to dope each group III nitride compound semiconductor layer with an element having a larger atomic radius than the main constituent element. When a light emitting element is used, it is originally desirable to use a binary or ternary system of a group III nitride compound semiconductor.
[0059]
When forming an n-type group III nitride compound semiconductor layer, a group IV element such as Si, Ge, Se, Te, and C or a group VI element can be added as an n-type impurity. In order to obtain a p-type layer, an acceptor impurity such as magnesium may be doped. In addition, as the p-type impurity, a group II element or a group IV element such as Zn, Be, Ca, Sr, and Ba can be added. A plurality of these may be doped simultaneously, or, for example, an n-type impurity and a p-type impurity may be doped in the same layer.
[0060]
The structure of each layer may be arbitrarily reduced by using lateral epitaxial growth to reduce dislocations in the group III nitride compound semiconductor layer. At this time, a method using a mask or a method using a mask that forms a step and forms a lateral growth layer on a concave portion can be adopted. As a method using a step, a method of forming a spot or stripe-shaped concave portion on a substrate, growing a group III nitride-based compound semiconductor thereon, and laterally growing the concave portion on the concave portion can be adopted.
[0061]
In addition, there may be a gap between the lateral growth layer and the layer or substrate thereunder. In the case where there is a gap, the entry of stress strain is prevented, so that the crystallinity can be further improved. The conditions for the lateral growth include a method of increasing the temperature, a method of increasing the supply amount of the group III element gas, and a method of adding magnesium (Mg).
[0062]
As a method for forming the group III nitride-based compound semiconductor layer, a halide vapor deposition method (Halide VPE) is preferable. Alternatively, for example, a metal organic chemical vapor deposition method (MOVPE) may be used. May be formed by different growth methods.
[Brief description of the drawings]
FIG. 1 is a state transition diagram of a group III nitride-based compound semiconductor (desired semiconductor crystal) showing an operation of a crystal separation step of the present invention.
FIG. 2 is a sectional view of a crystal growth apparatus developed to carry out the present invention.
FIG. 3 is a schematic cross-sectional view of a semiconductor crystal illustrating a manufacturing process of the semiconductor crystal according to the embodiment (Modification 2) of the present invention.
FIG. 4 is a cross-sectional view of a group III nitride-based compound semiconductor (desired semiconductor crystal) before separation according to a conventional technique.
[Explanation of symbols]
101 base substrate 120 group III nitride compound semiconductor (desired semiconductor crystal)
200: Crystal growth apparatus 210: Laser light capturing window

Claims (8)

A method of manufacturing a semiconductor crystal for obtaining an independent semiconductor crystal by separating a substrate used for crystal growth of a semiconductor and a semiconductor crystal grown on the substrate,
A crystal growth step of growing the semiconductor crystal on the substrate;
A crystal separation step of separating the substrate and the semiconductor crystal by irradiating light near the interface between the substrate and the semiconductor crystal,
In the crystal separation step,
Holding the temperature of the substrate at substantially the same temperature as the crystal growth temperature of the semiconductor crystal in the crystal growth step or a peripheral temperature thereof,
From either the semiconductor crystal or the substrate, from the layer side having a relatively large band gap,
A method of manufacturing a semiconductor crystal, comprising irradiating light having a wavelength corresponding to a band gap between a band gap of the semiconductor crystal and a band gap of the substrate. 2. The semiconductor crystal according to claim 1, further comprising a buffer layer stacking step of stacking a buffer layer at an interface between the substrate and the semiconductor crystal to reduce a lattice constant difference between the substrate and the semiconductor crystal. 3. Production method. In the crystal growth process, the as semiconductor crystals, whether or not added impurity is added, the main component _{"Al x Ga y In 1-x} -y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1, The method for producing a semiconductor crystal according to claim 1, wherein a group III nitride-based compound semiconductor that satisfies 0 ≦ x + y ≦ 1) is grown. 4. The method according to claim 1, wherein the light is irradiated from the substrate side in the crystal separation step. 5. 4. The method of manufacturing a semiconductor crystal according to claim 1, wherein in the crystal separation step, the light is irradiated from a side of the semiconductor crystal. 5. The method according to claim 5, wherein silicon (Si) or gallium arsenide (GaAs) is used as a material of the substrate. In the crystal growth step,
By growing the semiconductor crystal using a lateral growth method (ELO growth method), cavities are formed locally or periodically in the vicinity of the interface between the semiconductor crystal and the substrate by being dispersed in the horizontal direction. The method for manufacturing a semiconductor crystal according to claim 1, wherein: 8. The semiconductor crystal according to claim 1, wherein, in the crystal separation step, the light is irradiated in the same apparatus as a crystal growth apparatus that has performed the crystal growth step. 9. Method.

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