JP2002241192A - Semiconductor crystal manufacturing method and semiconductor light emitting device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To obtain a high-quality semiconductor crystal with few dislocations. SOLUTION: On a base substrate having a large number of protrusions, III
Substrate layer made of group nitride compound (desired semiconductor crystal)
Is grown, a cavity in which no semiconductor crystal is stacked is formed between the projections depending on the size, arrangement interval, crystal growth conditions, and the like of the projections. For this reason, if the thickness of the substrate layer is made sufficiently large compared to the height of the projection, the internal stress or the external stress tends to concentrate on the projection. As a result, in particular, these stresses act as a shear stress or the like on the protrusion, and when this stress increases,
The protrusion breaks. Therefore, if this stress is utilized, it is possible to easily separate the base substrate and the substrate layer,
A semiconductor crystal independent from the base substrate can be obtained.
The larger the cavity is, the more the above-mentioned stress is likely to be concentrated on the protrusion, and the base substrate and the substrate layer can be more reliably separated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a semiconductor crystal for producing a crystal growth substrate by forming a substrate layer made of a group III nitride compound semiconductor on an underlying substrate by utilizing a lateral crystal growth effect. It relates to a manufacturing method.

[0002]

2. Description of the Related Art As illustrated in FIG. 5, gallium nitride (Ga) is formed on an underlying substrate made of, for example, silicon (Si).
It is generally known that when a nitride semiconductor such as N) is crystal-grown and then cooled to room temperature, a large number of dislocations and cracks enter the nitride semiconductor layer.

[0003]

As described above, when a large number of dislocations and cracks enter the growth layer (nitride semiconductor layer), when a device is fabricated thereon, lattice defects, dislocations, deformation, As a result, many cracks and the like are generated, which causes deterioration of device characteristics. Further, when an independent substrate (crystal) is to be obtained by removing the underlying substrate made of, for example, silicon (Si) and leaving only the growth layer, a large area (1
cm ² or more) cannot be obtained.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a high-quality semiconductor crystal (crystal growth substrate) having no cracks and low dislocation density. .

[0005]

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, the first means is a manufacturing step of obtaining a semiconductor crystal independent of the underlying substrate by forming a substrate layer made of a group III nitride compound semiconductor on the underlying substrate by utilizing a lateral crystal growth effect, A projecting portion forming step of forming a large number of projecting portions on the base substrate, and at least a part of the surface of the projecting portion is at least partially connected to each other as an initial growth surface on which the substrate layer starts crystal growth. A crystal growth step of growing the substrate layer until a series of substantially flat surfaces is formed, and a separation step of separating the substrate layer and the base substrate by breaking the projections are provided.

However, the term "III-nitride compound semiconductor" as used herein generally refers to binary, ternary or quaternary "Al _{x
Ga y In (1-xy)} N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦
x + y ≦ 1) ”, and a semiconductor to which a p-type or n-type impurity is added, and a semiconductor of any mixed crystal ratio represented by the general formula: Semiconductor ”. In addition, the above group III elements (Al, G
a, In) is partially converted to boron (B) or thallium (T).
1) or a semiconductor in which part of nitrogen (N) is replaced by phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), or the like. "Group III nitride-based compound semiconductor" in the book. As the p-type impurity, for example, magnesium (Mg) or calcium (Ca) can be added. Examples of the n-type impurities include silicon (Si), sulfur (S), and selenium (S
e), tellurium (Te), germanium (Ge), or the like can be added. In addition, two or more of these impurities may be added at the same time, or both types (p-type and n-type) may be added at the same time.

For example, as shown in FIG. 1, when a substrate layer (semiconductor crystal) made of a group III nitride compound is grown on a base substrate having a large number of projections, the size of the projections, the spacing between the projections, By adjusting various conditions for crystal growth and the like, it is possible to form a “cavity” in which no semiconductor crystal is stacked between each projection (side of the projection). For this reason, if the thickness of the substrate layer is made sufficiently large compared to the height of the projection, the internal stress or the external stress tends to concentrate on the projection. As a result, particularly, these stresses act as a shear stress or the like on the projection, and when the stress increases, the projection is broken. Therefore, if this stress is utilized, it is possible to easily separate (peel) the base substrate and the substrate layer. By this means, a crystal (substrate layer) independent of the underlying substrate can be obtained. Also, as the above-mentioned “cavity” becomes larger, stress (shear stress) tends to concentrate on the protrusion.

Further, as can be seen from FIG. 1, for example, by forming the above-mentioned projections, the contact portion between the base substrate and the substrate layer (or a desired semiconductor crystal layer) is narrowed and limited. Therefore, distortion based on the difference between the two lattice constants is less likely to occur, and "stress based on the difference between the lattice constants of the underlying substrate and the substrate layer" is reduced. Therefore, when the substrate layer (desired semiconductor crystal) grows, unnecessary stress acting on the growing substrate layer is suppressed, and the density of dislocations and cracks is reduced.

When the base substrate and the substrate layer are separated (peeled), a part of the substrate layer may remain on the base substrate side,
Alternatively, a part of the underlying substrate (eg, broken debris of the protrusion) may remain on the substrate layer side. That is, the above-mentioned separation step does not assume (completely require) complete separation of each material such that some of the debris of these materials is eliminated.

A second means for solving the above-mentioned problem is that in the first means, the substrate layer and the underlying substrate are cooled or heated to thereby obtain a difference in thermal expansion coefficient between the substrate layer and the underlying substrate. Is to generate a stress based on the above, and to use the stress to break the projection. According to this means, the above-mentioned stress can be easily generated.

A third means is that, in a manufacturing process for obtaining a semiconductor crystal by forming a substrate layer made of a group III nitride compound semiconductor on an underlying substrate by utilizing a lateral crystal growth effect, A projecting portion forming step of forming a large number of projecting portions thereon, and at least a part of the surface of the projecting portion is connected to each other as an initial growth surface where the substrate layer starts crystal growth, and at least a series of Providing a crystal growth step of growing the substrate layer until the substrate layer grows to a substantially flat surface. In this crystal growth step, by adjusting the raw material supply amount q of the group III nitride-based compound semiconductor, the valley between the protrusions of the base substrate is adjusted. Difference between the crystal growth rate a of the group III nitride compound semiconductor in at least a part of the exposed area of the portion and the crystal growth rate b at the top of the protrusion (b−
a) is controlled to a substantially maximum value.

According to this means, the crystal growth rate in the vicinity of the top of the projection becomes relatively high, and the crystal growth in the vicinity of the above-mentioned exposed region is relatively suppressed, and the crystal growth from the vicinity of the top is dominant. Become a target. As a result, the lateral growth (ELO) of the substrate layer starting from near the top of the protrusion becomes remarkable, and acts on the substrate layer during the crystal growth of the substrate layer based on “difference in lattice constant between the underlying substrate and the substrate layer”. Stress ”is relieved.
Therefore, the crystal structure of the substrate layer is stabilized, and dislocations and cracks are less likely to occur in the substrate layer. If the lateral growth (ELO) of the substrate layer becomes remarkable, for example, a relatively large cavity may be formed on the side of the projection (between the projections).

For example, as shown in FIG. 1, when irregularities are formed on the surface of an undersubstrate at an appropriate size, interval, or period, in general, the projections are formed on the surface of the undersubstrate except for the peripheral portion near the outer peripheral side wall. The supply amount of the crystal material per unit time / unit area tends to be smaller in the concave portion (valley portion) than in the vicinity of the upper surface of the portion (projection portion). This tendency also depends on the flow rate, temperature, direction, etc. of the gas flow of the crystal material, but by controlling these conditions optimally or suitably, the above-mentioned difference (ba) becomes substantially the maximum value. It becomes possible to control.

[0014] A fourth means is that, in the crystal growth step of the first or second means, the raw material supply amount q of the group III nitride-based compound semiconductor is adjusted so that the distance between the protruding portions of the base substrate is reduced. Difference between the crystal growth rate a of the group III nitride compound semiconductor in at least a part of the exposed region of the valley portion and the crystal growth rate b at the top of the protrusion (b−
a) is controlled to a substantially maximum value.

In this case as well, the "stress based on the lattice constant difference between the underlying substrate and the substrate layer" acting on the substrate layer during the crystal growth of the substrate layer is relaxed, and the crystal structure of the substrate layer is reduced. And dislocations and cracks are less likely to occur in the substrate layer. This action and effect becomes relatively remarkable when the lateral growth is remarkable such that a cavity is formed between the projections (side of the projections). Further, if cavities are formed on the sides of the projections (between the projections), the shear stress is easily concentrated on the projections, and the base substrate and the substrate layer are easily separated by the shearing stress in the above separation step. Become. This action and effect becomes more remarkable as the cavity between the projections (side of the projection) becomes larger.

The fifth means is the same as the third or fourth means, wherein the raw material supply amount q is 1 μmol / mi.
n or more and 100 μmol / min or less.

More preferably, the raw material supply amount q is:
The range is preferably from 5 μmol / min to 90 μmol / min. A more desirable value depends on the specifications of the underlying substrate, such as the size and shape of the projections to be formed, the arrangement interval, and the like, the type of the raw material, the direction of the supply flow, and various conditions such as the crystal growth method.
The ideal range is about 0 to 80 μmol / min. This value is
If the difference is too large, it is difficult to control the difference (ba) to a substantially maximum value.
It is difficult to form large cavities in the area. Therefore, in such a case, the stress in the crystal based on the lattice constant difference is relatively hard to be relaxed, and the crystallinity of the single crystal of the substrate layer tends to deteriorate, such as generation of dislocation, which is not desirable.

Further, even when the base substrate and the substrate layer are separated due to stress (shear stress), if there is no cavity on the side of the projection or this cavity is small, stress is less likely to concentrate on the projection. In addition, it is difficult to break the projection, which is not desirable. On the other hand, if the raw material supply amount q is too small, it takes too much crystal growth time, which is disadvantageous in terms of productivity and is not desirable.

Further, the sixth means includes the first to fifth means.
In any one of the means,
Using silicon (Si) or silicon carbide (SiC). Other materials for the underlying substrate include, for example, GaN, AlN, GaAs, InP, Ga
P, MgO, ZnO, MgAl ₂ O _{4 and the} like are useful, and sapphire, spinel, manganese oxide, lithium gallium oxide (LiGaO ₂ ), molybdenum sulfide (Mo)
S) can also be used. However, when separating the base substrate and the substrate layer using shear stress based on the difference in thermal expansion coefficient, it is desirable to select a combination that does not reduce the difference in thermal expansion coefficient between both materials. It is desirable to select a material that easily breaks.

Further, the seventh means includes the first through sixth means.
In any one of the means, the material of the underlying substrate may be S
i (111) is used to form a projection so that the Si (111) surface is not exposed in the exposed region of the valley between the projections of the base substrate in the projection formation step. According to this means, since the crystal growth rate a on the exposed surface of the valley can be suppressed to a small value, it is possible to stably substantially maximize the difference (ba) while maintaining the crystallinity. Becomes

Further, the eighth means includes the first to seventh means.
After the protrusion forming step of any one of the means, a step of forming a buffer layer made of “Al _x Ga ₁ -xN (0 <x ≦ 1)” at least on the surface of the protrusion is provided.

However, apart from the above-mentioned buffer layer, a composition substantially the same as that of the above-mentioned buffer layer (eg, AlN, Al
GaN) intermediate layers may be stacked periodically, alternately with other layers, or in a multilayer configuration.

By stacking such a buffer layer (or an intermediate layer), the crystallinity can be improved by the same operation principle as that of the related art such that the stress acting on the substrate layer (growth layer) caused by the lattice constant difference can be reduced. It is possible to do.

A ninth means is that, in the above-mentioned eighth means, the thickness of the buffer layer is formed to be equal to or less than the vertical height of the projection. Also, as an absolute guide,
The thickness of the buffer layer is desirably about 0.01 μm or more and 1 μm or less. By this means, only a desired crystal layer (eg, a GaN layer) formed on the buffer layer can be grown in the lateral direction with good quality. That is, by this means,
“Stress based on lattice constant difference” applied to the crystal layer formed on the buffer layer during crystal growth is reduced, and the dislocation density can be effectively reduced.

AlN or AlGa for forming a buffer layer or the like
N and the like are easily formed on substantially the entire exposed surface of the base substrate, and Ga is originally formed to form a desired crystal growth layer and the like.
Although N tends to grow in the lateral direction more easily than AlN, AlGaN, or the like, according to the above-described means, a large “cavity” can be formed more reliably on the side of the protrusion.

By this means, when the substrate layer is separated from the underlying substrate, the crystal layer (the desired layer formed on the buffer layer) is also formed on the back surface of the substrate layer (the surface on the side with the underlying substrate). Is exposed directly and widely. Therefore, when forming an electrode on the back surface of the substrate layer, it becomes easy to suppress the electric resistance.

Although the thickness of the buffer layer is generally about 0.01 μm to 1 μm as described above, it is generally reasonable.
More preferably, the thickness is 0.1 μm or more and 0.5 μm or less.
If the thickness is too large, the cavity tends to be small, which is not desirable. If the thickness is too small, it is difficult to form the buffer layer substantially uniformly. In particular, if unevenness in film formation of the buffer layer (a portion where the film is not sufficiently formed) occurs near the upper portion of the protrusion, unevenness tends to occur in crystallinity, which is not desirable.

A tenth means is that in the crystal growth step of any one of the first to ninth means, the thickness of the substrate layer is 50 μm or more.

The thickness of the substrate layer (group III nitride compound semiconductor) on which the crystal is grown is desirably about 50 μm or more. As this thickness increases, the tensile stress on the substrate layer is alleviated, and dislocation or dislocation of the substrate layer is reduced. Crack generation density can be reduced. Further, at the same time, the substrate layer can be strengthened, and the above-mentioned shear stress can be easily concentrated on the above-mentioned projections.

In the eleventh means, in the crystal growth step of any one of the first to tenth means, a crystal growth method having a low crystal growth rate is changed to a crystal growth method having a high crystal growth rate. It is to change the crystal growth method on the way.

For example, until the crystal growth surface becomes a series of substantially planar shapes, a crystal growth method (eg, MOVPE method) that easily makes the above difference (ba) substantially maximum is adopted. If a crystal growth method (e.g., HVPE method) is used, which can easily make the thickness more than 50 μm efficiently, a semiconductor crystal having good crystallinity can be obtained in a short time.

In a twelfth aspect, in the projection forming step of any one of the first to eleventh means, the projections are arranged such that the projections are arranged at substantially equal intervals or at a substantially constant period. Forming a part.

As a result, the growth conditions for the lateral growth become substantially uniform as a whole, and the crystal quality is less likely to be uneven. In addition, since local variation is unlikely to occur during the time until the upper part of the valley between the protrusions is completely covered by the substrate layer, for example, a crystal growth method with a low crystal growth rate is used. When the crystal growth method is changed to a fast crystal growth method in the middle, it is easy to determine the timing accurately, early, or uniquely. Further, according to this means, the above-mentioned cavities each have a substantially uniform size, and the above-mentioned shear stress can be distributed substantially evenly to each of the protrusions. Separation of the substrate and the substrate layer can be reliably performed.

In a thirteenth aspect, in the projection forming step of the twelfth aspect, the projection is formed on a lattice point of a two-dimensional triangular lattice based on a substantially equilateral triangle having one side of 0.1 μm or more. Is to form By this means, the first
The second means can be more accurately and reliably implemented, and thus the number of dislocations can be reliably reduced.

In a fourteenth aspect, in the protrusion forming step of any one of the first to thirteenth means, the horizontal cross-sectional shape of the protrusion is substantially regular triangle, substantially regular hexagon, substantially circular, Or it is formed in a quadrangle. By this means, the direction of the crystal axis of the crystal formed from the group III nitride-based compound semiconductor can be easily aligned at each part, or the horizontal length (thickness) of the protrusion relative to an arbitrary horizontal direction Can be substantially uniformly restricted, so that the number of dislocations can be suppressed. In particular, regular hexagons and regular triangles are more preferable because they easily match the crystal structure of the semiconductor crystal. In addition, there is an advantage in the light of the current state of the general processing technology that a circle or a square is easy to form in terms of manufacturing technology.

In a fifteenth aspect, in the projection forming step of any one of the first to fourteenth aspects, the arrangement interval (arrangement cycle) of the projections is 0.1 μm or more and 10 μm or more.
It is as follows. More preferably, the distance between the projections is 0.5 to 8 although it depends on the crystal growth conditions.
About μm is good. However, this arrangement interval refers to the distance between the center points of the respective protruding portions approaching each other.

By this means, it becomes possible to cover the upper part of the valley of the projection with the substrate layer, and at the same time, it is possible to form a cavity between the projections. If this value is too small,
The effect of ELO is hardly obtained, and the crystallinity deteriorates. In addition, the cavity formed is too small, and unless the thickness of the substrate layer is increased more than necessary, it is not easy to break the protrusion.

On the other hand, if this value is too large, it is impossible to reliably cover the upper part of the valley of the projection with the substrate layer, and it becomes impossible to obtain a crystal (substrate layer) having uniform crystallinity and good quality. Alternatively, if this value is too large, the exposed surface of the valley becomes too large, so that the effect of ELO is hardly obtained, and no cavities are formed at all. Unless the film thickness is excessively large, it is not easy to break the projection.

According to a sixteenth aspect, in the projection forming step of any one of the first to fifteenth aspects, the height of the projection in the vertical direction is 0.5 μm or more and 20 μm or less. It is. More preferably, the vertical height of the projection is 0.8 to 5 μm, although it depends on the crystal growth conditions.
Good degree. If the height is too short, the effect of ELO is hardly obtained as in the case where there is no protrusion, and the crystallinity is deteriorated. If the height is too short, the above-mentioned cavity will not be formed. On the other hand, if the height is too high, the formation of the projection itself becomes difficult, it takes more time than necessary to form the projection, and the material of the underlying substrate is unnecessarily consumed, which is not desirable. If the height is too high, the shear stress is dispersed in the longitudinal direction of the projection, and it is difficult to reliably break the projection.

In a seventeenth aspect, in the projection forming step of any one of the first to sixteenth aspects, the thickness, width, or diameter of the projection in the lateral direction is 0.1 μm or more. 1
0 μm or less. More preferably, depending on the crystal growth conditions, the lateral thickness of the protrusion,
The width or diameter is preferably about 0.5 to 5 μm. If the thickness is too large, the influence of stress acting on the substrate layer (growth layer) based on the lattice constant difference increases, and the number of dislocations in the substrate layer tends to increase. On the other hand, if the thickness is too small, it becomes difficult to form the projection itself, or the crystal growth rate b at the top of the projection becomes slow, which is not desirable.

Also, when the projection is broken by stress (such as shearing stress), if the projection is too large in width, width, or diameter, a portion that is not easily broken is likely to be formed, which is desirable. Absent. Further, the magnitude of the effect of the stress acting on the substrate layer (growth layer) based on the lattice constant difference does not depend only on the width (length) of the protrusions in the lateral direction, but also on the arrangement interval of the protrusions. Dependent. If these setting ranges are inappropriate, the influence of the stress based on the lattice constant difference increases as described above, and the number of dislocations in the substrate layer tends to increase, which is not desirable.

Also, since the lateral thickness, width, or diameter near the top of the projection has an optimum value or an appropriate range as described above, the shape of the top, bottom, or horizontal cross section of the projection is Is at least a locally closed shape (island shape),
It is preferable that the shape is closed in a convex shape toward the outside, and more preferably, the shape of the upper surface, the bottom surface, or the horizontal cross section is a substantially circular shape or a substantially regular polygon. With such a setting, it is easy to reliably realize the optimum value or the appropriate range in any horizontal direction.

In an eighteenth aspect, in any one of the first to seventeenth aspects, prior to the crystal growth step, various types of etching, electron beam irradiation, optical processing such as laser, chemical processing, and the like are performed. By degrading or changing the crystallinity or molecular structure of at least a part of the exposed region of the valley between the protrusions of the underlying substrate by physical treatment or physical treatment such as cutting or polishing, the group III in this exposed region The purpose is to reduce the crystal growth rate a of the nitride-based compound semiconductor. By this means, the difference (ba) between the crystal growth rates can be further increased. Therefore, according to this means, the crystal growth rate near the top of the protrusion becomes relatively large, and the same effect as described above acts on the substrate layer during the crystal growth of the substrate layer. The stress caused by the lattice constant difference between the layers is relaxed, and dislocations and cracks are less likely to occur in the substrate layer.

A nineteenth means is that, in any one of the above-mentioned separation steps, a substrate composed of a base substrate and a substrate layer is left in a reaction chamber of a growth apparatus, and a substantially constant flow rate of ammonia (NH ₃ ) gas is supplied. In this state, the substrate is cooled to approximately room temperature at a cooling rate of about “-100 ° C./min to −0.5 ° C./min” while being kept flowing in the reaction chamber. For example, by such means, while maintaining the crystallinity of the substrate layer at a high quality,
The above separation step can be performed.

In the twentieth means, at least after any one of the above-mentioned separation steps, a chemical or physical processing such as etching is performed on the broken debris of the protrusion remaining on the back surface of the substrate layer. Is to provide a debris removal step for removing the debris. According to this means, when an electrode such as a semiconductor light emitting element is formed on the back surface of the substrate layer (the surface on the side from which the underlying substrate has been peeled off), current unevenness and electric resistance generated near the interface between the electrode and the substrate layer are formed. Can be suppressed, thereby reducing the drive voltage and
Alternatively, the emission intensity can be improved.

Further, by removing the broken debris of the projection, when the electrode is also used as a reflecting mirror of a semiconductor light emitting device or the like, light absorption and scattering near the mirror surface are reduced, and the reflectance is improved. Therefore, the emission intensity is improved. Further, for example, when the debris removal step is performed by a physical processing such as polishing, the buffer layer on the back surface of the substrate layer is also removed, or the flatness of the back surface of the substrate layer is improved. Therefore, the above-mentioned effects such as suppression of current unevenness and electric resistance or reduction of light absorption and scattering near the mirror surface can be further reinforced.

A twenty-first means is a group III nitride compound semiconductor light emitting device, wherein the semiconductor crystal is manufactured by using the semiconductor crystal manufacturing method according to any one of the first to twentieth means. As a crystal growth substrate. According to this means, it becomes possible or easy to manufacture a group III nitride compound semiconductor light emitting device from a semiconductor having good crystallinity and low internal stress.

The twenty-second means may be formed by crystal growth using a semiconductor crystal manufactured by the method for manufacturing a semiconductor crystal according to any one of the first to twentieth means as a crystal growth substrate. It is to manufacture a group III nitride compound semiconductor light emitting device. According to this means, it becomes possible or easy to manufacture a group III nitride compound semiconductor light emitting device from a semiconductor having good crystallinity and low internal stress. With the above means, the above-mentioned problem can be solved.

[0049]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. However, the present invention is not limited to the embodiments described below. Hereinafter, an outline of a manufacturing procedure of a semiconductor crystal (crystal growth substrate) in an embodiment of the present invention will be exemplified.

[1] Projection Forming Step As shown in FIG. 2, a single crystal base substrate 1 made of silicon
On the Si (111) surface of No. 01, approximately columnar protrusions 101a having a diameter of about 1 μm and a height of about 1 μm were formed at an interval of about 2 μm by dry etching using photolithography. As an array form, one side is about 2 μm
So that the center of the cylindrical bottom surface of the projection 101a is arranged on each lattice point of the two-dimensional triangular lattice based on the substantially equilateral triangle of
The protrusion 101a was formed. However, the thickness of the base substrate 101 was about 200 μm.

[2] Crystal Growth Step In this crystal growth step, as shown in FIG. 4, the crystal growth surfaces are connected to each other from the upper surface (initial state) of the protrusion 101a and grow in a series of substantially planar shapes. Is performed according to the metalorganic compound vapor phase epitaxy (MOVPE) method. Thereafter, the growth step until the substrate layer (crystal layer) is grown to a thickness of about 200 μm is performed by the hydride vapor phase epitaxy (MOVPE) method. HVPE method). In this crystal growth step, ammonia (NH ₃ ) gas and carrier gas (H ₂ ,
N ₂ ), trimethylgallium (Ga (CH ₃ ) ₃ ) gas (hereinafter referred to as “TMG
]) And trimethylaluminum (Al (C
H _{3) 3)} using a gas (hereinafter referred to as "TMA").

(A) First, the base substrate 101 (FIG. 2) provided with the above-mentioned projections 101a is washed by organic washing and acid treatment, and is mounted on a susceptor placed in a reaction chamber of a crystal growth apparatus. Temperature 1100 ° C while flowing H ₂ into the reaction chamber at normal pressure
The base substrate 101 was baked.

[0053] (b) Next, on the underlying substrate 101, according to the MOVPE _{method, H 2, NH 3, TMG} , TM
A to supply the AlGaN buffer layer (substrate layer first layer)
102a was formed. This AlGaN buffer layer 102
The crystal growth temperature of a is about 1100 ° C. and the film thickness is about 0.3 μm
Met. (FIG. 3) (c) This AlGaN buffer layer (substrate layer first layer) 10
2a, a part of the substrate layer second layer, that is, a film thickness of about 5 μm
The GaN layer 102b was grown at a growth temperature of 1075 ° C. by supplying H ₂ , NH ₃ and TMG. By this step, as shown in FIG. 4, the second substrate layer (GaN layer 102) is formed.
Part b) grew in the lateral direction, and a large cavity was formed on the side of the valley, that is, the protrusion 101a. The TMG supply rate at this time is about 40 μmol / min, and the crystal growth rate of the second substrate layer (GaN layer 102 b) is about 1 μm / H.
r.

(D) Thereafter, the GaN layer (substrate layer second layer) is formed according to the hydride vapor phase epitaxy (HVPE).
The layer 102b was further grown to 200 μm. The crystal growth rate of the GaN layer 102b in this HVPE method was about 45 μm / Hr.

[3] Separation Step (a) After the above-described crystal growth step, the base substrate 101 is kept while flowing ammonia (NH ₃ ) gas into the reaction chamber of the crystal growth apparatus.
(AlGaN buffer layer 102a and GaN layer 102
b) was cooled to approximately room temperature. The cooling rate at this time is generally “−50 ° C./min to −5 ° C./min.
min ”.

(B) Thereafter, when these are taken out of the reaction chamber of the crystal growth apparatus, Ga separated from the underlying substrate 101 is removed.
N crystals were obtained. However, this crystal has a GaN layer 10
On the back surface of 2b, a small portion of the debris of the AlGaN buffer layer 102a and a broken debris of the protrusion 101a remained.

[4] Step of removing broken debris After the above separation step, the broken debris of the protrusion 101a made of Si remaining on the back surface of the GaN crystal is removed by etching using a mixture of hydrofluoric acid and nitric acid. Removed.

By the above manufacturing method, the film thickness is about 200 μm
Quality GaN crystal (GaN layer 1)
02b), that is, a desired semiconductor substrate independent of the base substrate 101 could be obtained.

In the above embodiment, as shown in FIG. 2, the projections and valleys of the base substrate are formed by a vertical plane and a horizontal plane. May be. Accordingly, the cross-sectional shape of the valley formed on the base substrate illustrated in FIG. 2C is not limited to a substantially rectangular concave shape, but may be, for example, a substantially U-shaped or substantially V-shaped shape. In general, these shapes, sizes, intervals, arrangements, orientations, and the like are arbitrary.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a base substrate having a projection and a partial fragment of a semiconductor crystal grown thereon illustrating the operation of the present invention.

FIG. 2 is a schematic perspective view (a), a plan view (b), and a cross-sectional view (c) of a partial fragment of a base substrate (Si substrate) 101 according to an embodiment of the present invention.

FIG. 3 is a substrate layer first layer (AlGaN buffer layer) 102;
5A is a schematic perspective view, FIG. 5B is a plan view, and FIG. 5C is a cross-sectional view of the base substrate 101 on which a is formed.

FIG. 4 is a schematic perspective view (a), a plan view (b), and a cross-sectional view (c) of an underlying substrate 101 on which a substrate layer 102 (layer 102a and layer 102b) is stacked.

FIG. 5 is a schematic cross-sectional view of a conventional semiconductor crystal on a base substrate.

[Explanation of symbols]

 101: Undersubstrate (Si substrate) 101a: Protrusion 102: Substrate layer (nitride semiconductor layer) 102a: First substrate layer (AlGaN buffer layer) 102b: Second substrate layer (GaN single crystal layer)

Continuation of the front page (72) Inventor Kazuyoshi Tomita 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture F-term in Toyota Central Research Laboratory Co., Ltd. 4G077 AA03 BE11 BE13 BE15 DB01 ED04 ED05 ED06 EE01 EE02 EF03 FJ03 TK01 TK04 TK06 TK10 TK11 5F041 AA40 CA33 CA40 CA67 CA77 5F045 AA04 AB09 AB14 AC08 AC12 AC15 AD14 AE29 AF02 AF03 BB01 BB02 BB11 BB12 BB13 CA09 CB02 DA53 EE12 HA01 HA02 HA08 HA09 HA11 HA12

Claims (22)

[Claims] 1. A method for obtaining a semiconductor crystal independent of an undersubstrate by forming a substrate layer made of a group III nitride compound semiconductor on an undersubstrate by utilizing a lateral crystal growth action. A projecting portion forming step of forming a large number of projecting portions on the base substrate; and at least a part of the surface of the projecting portion is a first growing surface on which the substrate layer starts crystal growth. A crystal growth step of crystal-growing the substrate layer until it is connected and grown to at least a series of substantially flat surfaces; and a separation step of separating the substrate layer and the base substrate by breaking the projections. A method for manufacturing a semiconductor crystal, comprising: 2. A method of cooling or heating the substrate layer and the underlying substrate to generate a stress based on a difference in thermal expansion coefficient between the substrate layer and the underlying substrate, and utilizing the stress to generate the protrusion. The method for producing a semiconductor crystal according to claim 1, wherein the semiconductor crystal is broken. 3. A method for obtaining a semiconductor crystal by forming a substrate layer made of a group III nitride-based compound semiconductor on an undersubstrate by utilizing a lateral crystal growth action, comprising: A projecting portion forming step of forming a large number of projecting portions, at least a part of the surface of the projecting portion is used as an initial growth surface on which the substrate layer starts crystal growth, and the growth surfaces are connected to each other to form at least a series of A crystal growth step of growing the substrate layer until it grows into a substantially flat surface. In the crystal growth step, the raw material supply amount q of the group III nitride compound semiconductor is adjusted, The difference (ba) between the crystal growth rate a of the group III nitride compound semiconductor in at least a part of the exposed region of the valley between the protrusions and the crystal growth rate b at the top of the protrusion. ) Is controlled to a substantially maximum value. 4. In the crystal growth step, a raw material supply amount q of the group III nitride-based compound semiconductor is adjusted so that at least a part of a valley between the protrusions of the base substrate is exposed in the exposed region. 2. The method according to claim 1, wherein a difference (ba) between a crystal growth rate a of the group III nitride-based compound semiconductor and a crystal growth rate b at the top of the protrusion is controlled to a substantially maximum value. A method for manufacturing a semiconductor crystal according to claim 2. 5. The method for producing a semiconductor crystal according to claim 3, wherein the raw material supply amount q is set to 1 μmol / min or more and 100 μmol / min or less. 6. The method of manufacturing a semiconductor crystal according to claim 1, wherein silicon (Si) or silicon carbide (SiC) is used as a material of the base substrate. 7. The method according to claim 1, wherein the base substrate is made of Si (11).
The method according to claim 1, wherein in the step of forming the protrusion, the protrusion is formed in an exposed region of a valley between the protrusions of the base substrate so that the Si (111) surface is not exposed. Item 1
A method for manufacturing a semiconductor crystal according to claim 6. 8. After the step of forming the protrusion, at least the surface of the protrusion has “Al _x Ga ₁ -xN (0
8. The method of manufacturing a semiconductor crystal according to claim 1, further comprising a step of forming a buffer layer composed of <x ≦ 1). 9. The method according to claim 8, wherein the buffer layer is formed to have a thickness equal to or less than a height of the protrusion in a vertical direction. 10. The method according to claim 1, wherein the thickness of the substrate layer is set to 50 μm or more in the crystal growth step. 11. The method according to claim 1, wherein in the crystal growth step, the crystal growth method is changed halfway from a crystal growth method with a low crystal growth rate to a crystal growth method with a high crystal growth rate. 11. The method for manufacturing a semiconductor crystal according to any one of items 10 to 10. 12. The method according to claim 1, wherein in the step of forming the protrusions, the protrusions are formed such that the protrusions are arranged at substantially equal intervals or at a substantially constant period. 2. The method for producing a semiconductor crystal according to claim 1. 13. The projection forming step, wherein the projection is formed on a lattice point of a two-dimensional triangular lattice based on a substantially equilateral triangle having one side of 0.1 μm or more. 3. The method for producing a semiconductor crystal according to item 1. 14. The projection according to claim 1, wherein in the projection forming step, a horizontal cross-sectional shape of the projection is formed into a substantially regular triangle, a substantially regular hexagon, a substantially circle, or a quadrangle. The method for producing a semiconductor crystal according to claim 1. 15. The semiconductor crystal according to claim 1, wherein, in the protrusion forming step, an interval between the protrusions is set to 0.1 μm or more and 10 μm or less. Manufacturing method. 16. The method according to claim 1, wherein the height of the protrusion in the vertical direction is 0.5 μm or more and 20 μm or less in the step of forming the protrusion.
13. The method for producing a semiconductor crystal according to the above item. 17. In the projecting portion forming step, the lateral thickness, width or diameter of the projecting portion is 0.1 μm or more,
17. The method of manufacturing a semiconductor crystal according to claim 1, wherein the thickness is set to 0 μm or less. 18. The projections of the undersubstrate by various etching, electron beam irradiation, optical processing such as laser, chemical processing, or physical processing such as cutting or polishing before the crystal growth step. By deteriorating or changing the crystallinity or molecular structure of at least a part of the exposed region of the valley between the parts, the crystal growth rate a of the group III nitride-based compound semiconductor in the exposed region is reduced. The method of manufacturing a semiconductor crystal according to claim 1, wherein 19. In the separating step, a substrate comprising the base substrate and the substrate layer is left in a reaction chamber of a growth apparatus, and a substantially constant flow rate of ammonia (NH ₃ ) gas is allowed to flow into the reaction chamber. Then, the substrate is generally moved from -100 ° C / min to -0.5 ° C / mi.
19. The method for manufacturing a semiconductor crystal according to claim 1, wherein the semiconductor crystal is cooled to substantially normal temperature at a cooling rate of about "n". 20. A debris removing step of removing a broken debris of the protrusion remaining on the back surface of the substrate layer by a chemical or physical processing such as etching at least after the separating step. 20. The method for manufacturing a semiconductor crystal according to claim 1, wherein the semiconductor crystal is a semiconductor crystal. 21. A group III nitride comprising the semiconductor crystal as a crystal growth substrate manufactured by using the method of manufacturing a semiconductor crystal according to claim 1. Based compound semiconductor light emitting device. 22. A semiconductor crystal produced by the method for producing a semiconductor crystal according to claim 1, wherein said semiconductor crystal is produced by crystal growth using said semiconductor crystal as a crystal growth substrate. A group III nitride compound semiconductor light emitting device.