JP4084541B2 - Manufacturing method of semiconductor crystal and semiconductor light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor crystal manufacturing method for obtaining a crystal growth substrate by forming a substrate layer made of a group III nitride compound semiconductor on a base substrate by utilizing a lateral crystal growth action.
[0002]
[Prior art]
As illustrated in FIG. 5, when a nitride semiconductor such as gallium nitride (GaN) is grown on a base substrate made of, for example, silicon (Si), and then cooled to room temperature, dislocations and cracks are formed in the nitride semiconductor layer. It is generally known to enter a large number.
[0003]
[Problems to be solved by the invention]
In this way, when a large number of dislocations and cracks enter the growth layer (nitride semiconductor layer), when a device is fabricated thereon, a large number of lattice defects, dislocations, deformations, cracks, etc. occur in the device. It causes deterioration of characteristics.
In addition, when the base substrate made of silicon (Si) or the like is removed and only the growth layer is left to obtain an independent substrate (crystal), a large area (1 cm) is obtained due to the above-described dislocations and cracks. ² The above) is not obtained.
[0004]
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) free from cracks and having a low dislocation density.
[0005]
[Means for Solving the Problem, Action, and Effect of the Invention]
In order to solve the above problems, the following means are effective.
That is, the first means is a manufacturing process for obtaining a semiconductor crystal independent of the base substrate by forming a substrate layer made of a group III nitride compound semiconductor on the base substrate using a lateral crystal growth action. A protrusion forming step for forming a large number of protrusions on the base substrate, and at least a part of the surface of the protrusion as a first growth surface on which the substrate layer starts crystal growth; A crystal growth process for crystal growth of the substrate layer until it grows in a series of substantially flat surfaces and a separation process for separating the substrate layer and the base substrate by breaking the protrusions are provided. Then, by cooling or heating the substrate layer and the base substrate, a stress based on the difference in thermal expansion coefficient between the substrate layer and the base substrate is generated, and the protrusions are ruptured using this stress. That is.
[0006]
However, the “Group III nitride compound semiconductor” mentioned here is generally a binary, ternary or quaternary “Al”. _x Ga _y In _(1-xy) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) ”is included, and semiconductors having an arbitrary mixed crystal ratio represented by the general formula“ N ”are added, and p-type or n-type impurities are added. These semiconductors are also included in the category of “Group III nitride compound semiconductor” in this specification.
Further, a part of the above group III elements (Al, Ga, In) is replaced with boron (B), thallium (Tl), or the like, or a part of nitrogen (N) is phosphorus (P), Semiconductors substituted with arsenic (As), antimony (Sb), bismuth (Bi), and the like are also included in the category of “Group III nitride compound semiconductor” in this specification.
Moreover, as said p-type impurity, magnesium (Mg), calcium (Ca), etc. can be added, for example.
As the n-type impurity, for example, silicon (Si), sulfur (S), selenium (Se), tellurium (Te), germanium (Ge), or the like can be added.
Further, two or more elements of these impurities may be added simultaneously, or both types (p-type and n-type) may be added simultaneously.
[0007]
For example, as illustrated 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 protrusions, the size of the protrusions, the arrangement interval, the crystal growth By adjusting the conditions and the like, a “cavity” in which no semiconductor crystal is stacked can be formed between the protrusions (sides of the protrusions). For this reason, if the thickness of the substrate layer is made sufficiently larger than the height of the protrusion, internal stress or external stress tends to act on the protrusion. As a result, these stresses in particular act as shear stresses on the protrusions, and when the stresses increase, the protrusions break. Therefore, if this stress is used, the base substrate and the substrate layer can be easily separated (peeled). By this means, a crystal (substrate layer) independent of the base substrate can be obtained.
Further, the larger the “cavity” is, the more easily stress (shear stress) is concentrated on the protrusion.
[0008]
Further, as can be seen from FIG. 1, for example, by forming the projections as described above, the contact portion between the base substrate and the substrate layer (or a desired semiconductor crystal layer) is narrowly limited. The strain based on the difference in the lattice constant is less likely to occur, and “stress based on the difference in the lattice constant between the base substrate and the substrate layer” is relieved. For this reason, when the substrate layer (desired semiconductor crystal) grows, unnecessary stress acting on the growing substrate layer is suppressed, and the generation density of dislocations and cracks is reduced.
[0009]
Note that when separating (separating) the base substrate and the substrate layer, a part of the substrate layer may remain on the base substrate side, or a part of the base substrate (eg, a protrusion portion) on the substrate layer side. Breaking debris) may remain. That is, the above separation step does not assume (necessary conditions) the complete separation of each material so that some of the remnants of these materials are eliminated.
[0010]
Also, Based on the difference in thermal expansion coefficient between the substrate layer and the underlying substrate Stress can be easily generated.
[0011]
Also, Second In the manufacturing process of obtaining a semiconductor crystal by forming a substrate layer made of a group III nitride compound semiconductor on the base substrate using the lateral crystal growth action, a number of protrusions are formed on the base substrate. A projection layer forming step, and at least a part of the surface of the projection portion as a first growth surface on which the substrate layer starts crystal growth until the growth surfaces are connected to each other and grown to at least a series of substantially flat surfaces. A crystal growth step for crystal growth, and adjusting the raw material supply amount q of the group III nitride compound semiconductor in this crystal growth step, thereby exposing at least a part of the valleys between the protrusions of the base substrate Is to control the difference (b−a) between the crystal growth rate a of the group III nitride compound semiconductor and the crystal growth rate b at the top of the protrusion to a substantially maximum value.
[0012]
According to this means, the crystal growth rate in the vicinity of the top of the protrusion is relatively increased, the crystal growth in the vicinity of the exposed region is relatively suppressed, and the crystal growth from the vicinity of the top becomes dominant. . As a result, the lateral growth (ELO) of the substrate layer starting from the vicinity of the top of the protrusion becomes prominent, and acts on the substrate layer during the crystal growth of the substrate layer “based on the lattice constant difference between the base 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.
Further, if the lateral growth (ELO) of the substrate layer becomes significant, for example, a relatively large cavity may be formed on the side of the protrusion (between the protrusions).
[0013]
For example, as illustrated in FIG. 1, when irregularities are formed on the surface of the base substrate with an appropriate size, interval, or period, generally, a convex portion (protrusion) is formed in a portion other than the peripheral portion near the outer peripheral side wall of the base substrate. Compared with the vicinity of the upper surface of the portion), the amount of the crystal material supplied per unit time / unit area tends to be smaller in the concave portion (valley portion). This tendency depends on the flow rate, temperature, direction, etc. of the gas flow of the crystal material, but the above difference (b−a) is made to be approximately the maximum value by optimally or suitably controlling these conditions. It becomes possible to control.
[0014]
Also, Third Means above First In the crystal growth step of the means, by adjusting the raw material supply amount q of the group III nitride compound semiconductor, the group III nitride compound semiconductor in the at least part of the exposed region of the valley between the protrusions of the base substrate The difference (b−a) between the crystal growth rate a and the crystal growth rate b at the top of the protrusion is controlled to a substantially maximum value.
[0015]
In this case as well, as in the above-mentioned means, the “stress based on the lattice constant difference between the base substrate and the substrate layer” acting on the substrate layer during crystal growth of the substrate layer is relaxed, and the crystal structure of the substrate layer is stabilized. Dislocations and cracks are less likely to occur in the substrate layer. This action / effect becomes relatively remarkable when the lateral growth is so remarkable that a cavity is formed between the protrusions (sides of the protrusions).
Further, if a cavity is formed on the side of the protrusion (between the protrusions), the shear stress tends to concentrate on the protrusion, and the base substrate and the substrate layer can be easily separated by the shear stress in the separation process. Become. This action / effect becomes more prominent as the cavity between the protrusions (the sides of the protrusions) becomes larger.
[0016]
Also, 4th Means above Second or third In the means, the raw material supply amount q is set to 1 μmol / min or more and 100 μmol / min or less.
[0017]
More preferably, the raw material supply amount q is 5 μmol / min or more and 90 μmol / min or less. More desirable values depend on the specifications of the base substrate such as the size and shape of the projections to be formed, the arrangement interval, and other conditions such as the type of feed material, the feed flow direction, and the crystal growth method. About 80 μmol / min is ideal. If this value is too large, it becomes difficult to control the difference (b−a) to a substantially maximum value, so that it becomes difficult to form a large cavity between the protrusions (sides of the protrusions). Therefore, in such a case, the stress in the crystal based on the difference in lattice constant is relatively less relaxed, and dislocations are likely to occur. This makes the single crystal crystallinity of the substrate layer easily deteriorated, which is not desirable.
[0018]
Also, when the base substrate and the substrate layer are separated by stress (shear stress), if there is no cavity on the side of the protrusion or if this cavity is small, the stress is difficult to concentrate on the protrusion. This is not desirable because it is difficult to break.
On the other hand, if the raw material supply amount q is too small, it takes too much time for crystal growth, which is disadvantageous in terms of productivity, which is not desirable.
[0019]
Also, 5th Means above 1st to 4th In any one of the means, silicon (Si) or silicon carbide (SiC) is used as a material for the base substrate.
As other base substrate materials, for example, GaN, AlN, GaAs, InP, GaP, MgO, ZnO, MgAl ₂ O _Four Etc., and sapphire, spinel, manganese oxide, lithium gallium oxide (LiGaO ₂ ), Molybdenum sulfide (MoS), and the like 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 the two materials. For this, it is desirable to select a material that easily breaks.
[0020]
Also, 6th Means above 1st to 5th In any one of the means, Si (111) is used as the material of the base substrate, and the protrusion is formed so that the Si (111) surface is not exposed in the exposed region of the valley between the protrusions of the base substrate in the protrusion formation process. Is to form.
According to this means, since the crystal growth rate a of the exposed surface of the valley can be suppressed small, the difference (b−a) can be stably and substantially maximized while maintaining the crystallinity. It becomes.
[0021]
Also, 7th Means above 1st to 6th After the protrusion forming step of any one means, at least the surface of the protrusion is “Al _x Ga _1-x A step of forming a buffer layer made of N (0 <x ≦ 1) ”.
[0022]
However, in addition to the buffer layer, an intermediate layer of substantially the same composition (eg, AlN or AlGaN) as the buffer layer is formed periodically or alternately with other layers, or a multilayer structure is formed. As is done, they may be stacked.
[0023]
Crystallinity can be improved by the same principle of action as in the past, such as the buffer layer (or intermediate layer) being laminated to relieve stress acting on the substrate layer (growth layer) due to the difference in lattice constant. It becomes possible.
[0024]
Also, 8th Means above 7th In the means, the film thickness of the buffer layer is formed to be equal to or less than the height in the vertical direction of the protrusion. Also, as an absolute guide, the buffer layer thickness is preferably about 0.01 μm or more and 1 μm or less.
By this means, only a desired crystal layer (eg, GaN layer) formed on the buffer layer can be grown in the lateral direction with good quality. That is, by this means, the “stress based on the difference in lattice constant” applied to the crystal layer formed on the buffer layer during crystal growth is reduced, and the dislocation density can be effectively reduced.
[0025]
AlN, AlGaN, and the like that form the buffer layer and the like are easily formed on almost the entire exposed surface of the base substrate, and GaN that originally forms a growth layer of a desired crystal is more likely to be AlN or AlGaN. However, according to the above means, a large “cavity” can be more reliably formed on the side of the protrusion.
[0026]
Further, when the substrate layer is separated from the base substrate by this means, the crystal layer (desired layer formed on the buffer layer) is also formed on the back surface of the substrate layer (the surface on which the base substrate is present). Is directly exposed over a wide area. Therefore, it is easy to suppress the electrical resistance when forming the electrode on the back surface of the substrate layer.
[0027]
As described above, the thickness of the buffer layer is generally in the range of about 0.01 μm to 1 μm, more preferably 0.1 μm or more and 0.5 μm or less. If this film thickness is too thick, the cavity tends to be small, which is not desirable. If the film thickness is too thin, it is difficult to form the buffer layer substantially uniformly. In particular, if uneven film formation of the buffer layer (portion where film formation is not sufficient) occurs in the vicinity of the upper portion of the protrusion, unevenness of the crystallinity tends to occur, which is not desirable.
[0028]
Also, 9th Means above 1st to 8th In the crystal growth step of any one means, the film thickness of the substrate layer is set to 50 μm or more.
[0029]
The thickness of the substrate layer (Group III nitride compound semiconductor) for crystal growth is preferably about 50 μm or more. The thicker the thickness, the more the tensile stress on the substrate layer is relaxed, and the generation of dislocations and cracks in the substrate layer. Density can be reduced. Furthermore, the substrate layer can be strengthened at the same time, and the shear stress can be easily concentrated on the protrusions.
[0030]
Also, 10th Means above 1st to 9th In the crystal growth step of any one means, the crystal growth method is changed midway from a crystal growth method having a low crystal growth rate to a crystal growth method having a high crystal growth rate.
[0031]
For example, a crystal growth method (e.g., MOVPE method) that makes it easy to maximize the above difference (b−a) is adopted until the crystal growth surface becomes a series of substantially planar shapes. Employing a crystal growth method (eg, HVPE method) that can easily be 50 μm or more makes it possible to obtain a high-quality semiconductor crystal in a short time.
[0032]
Also, Eleventh Means above 1st to 10th In the protrusion forming step of any one means, the protrusions are formed so that the protrusions are arranged at substantially equal intervals or at a substantially constant period.
[0033]
As a result, the growth conditions for the lateral growth are substantially uniform as a whole, and unevenness in crystallinity is less likely to occur. In addition, since local variations are less likely to occur during the time until the upper portion of the valley between the protrusions is completely covered by the substrate layer, for example, from a crystal growth method with a slow crystal growth rate, When the crystal growth method is changed to a fast crystal growth method, it becomes easy to determine the timing accurately, early, or uniquely.
In addition, this means that the cavities are approximately equal in size, and the shear stress can be distributed substantially evenly to the respective protrusions. The substrate and the substrate layer can be reliably separated.
[0034]
Also, 12th Means above Eleventh In the protrusion forming step of the means, the protrusions are formed on the lattice points of a two-dimensional triangular lattice based on a substantially equilateral triangle having one side of 0.1 μm or more.
By this means, the above Eleventh The means can be implemented more specifically and accurately, and thus the number of dislocations can be reliably reduced.
[0035]
Also, Thirteenth Means above 1st to 12th In the projection forming step of any one means, the horizontal cross-sectional shape of the projection is formed into a substantially regular triangle, a substantially regular hexagon, a substantially circle, or a quadrangle.
This means that the crystal axis direction of the crystal formed from the group III nitride compound semiconductor can be easily aligned in each part, or the horizontal length (thickness) of the protrusion with respect to an arbitrary horizontal direction. Therefore, the number of dislocations can be suppressed. In particular, regular hexagons and regular triangles are more desirable because they easily match the crystal structure of the semiconductor crystal. Further, there is a merit in light of the current state of the general processing technology level that a circle or a rectangle is easy to form in terms of manufacturing technology.
[0036]
Also, 14th Means above 1st to 13th In the projection forming step of any one means, the arrangement interval (arrangement period) of the projections is set to 0.1 μm or more and 10 μm or less. More desirably, the arrangement interval of the protrusions is preferably about 0.5 to 8 μm, although it depends on the conditions of crystal growth. However, this arrangement | positioning space | interval means the distance between the center points of each projection part which mutually approaches.
[0037]
By this means, it is possible to cover the upper part of the valley of the protrusion with the substrate layer, and at the same time, it is possible to form a cavity between the protrusions.
If this value is too small, the effect of ELO is hardly obtained, and the crystallinity is deteriorated. In addition, the formed cavity becomes too small, and it is not easy to break the protrusion unless the film thickness of the substrate layer is increased more than necessary.
[0038]
Further, if this value becomes too large, the upper part of the valleys of the protrusions cannot be reliably covered with the substrate layer, and crystals having a uniform crystallinity and a good quality (substrate layer) cannot be obtained.
Alternatively, if this value is too large, the exposed surface of the valley becomes too large, and the effect of ELO is hardly obtained, and no cavities are formed at all, so that the crystallinity deteriorates and the substrate layer Unless the film thickness is increased more than necessary, it is not easy to break the protrusion.
[0039]
Also, 15th Means above 1st to 14th In the projection forming step of any one means, the vertical height of the projection is set to 0.5 μm or more and 20 μm or less. More desirably, although depending on the crystal growth conditions, the height of the protrusions in the vertical direction is preferably about 0.8 to 5 μm.
If this height is too short, as in the case where there is no protrusion, the effect of ELO is hardly obtained and the crystallinity deteriorates. On the other hand, if the height is too short, the above-mentioned cavity is not formed.
On the other hand, if the height is too high, the formation of the protrusion itself becomes difficult, it takes more time than necessary to form the protrusion, and the material of the base substrate is unnecessarily consumed. On the other hand, if the height is too high, the shear stress is dispersed in the longitudinal direction of the protrusions, making it difficult to reliably break the protrusions.
[0040]
Also, 16th Means above 1st to 15th In the projection forming step of any one means, the lateral thickness, width, or diameter of the projection is set to 0.1 μm or more and 10 μm or less. More desirably, the thickness, width, or diameter in the lateral direction of the protrusion is preferably about 0.5 to 5 μm, although it depends on the conditions for crystal growth.
If the thickness is too thick, the influence of stress acting on the substrate layer (growth layer) based on the difference in lattice constant increases, and the number of dislocations in the substrate layer tends to increase. On the other hand, if it is too thin, the formation of the projection itself becomes difficult, or the crystal growth rate b at the top of the projection becomes slow, which is not desirable.
[0041]
Also, when the protrusion is broken by stress (shear stress or the like), if the width, width, or diameter in the lateral direction of the protrusion is too large, a portion that is not surely broken is likely to occur, which is not desirable.
In addition, the magnitude of the influence of stress acting on the substrate layer (growth layer) based on the difference in lattice constant does not depend only on the lateral thickness (length) of the protrusions, but also on the arrangement interval of the protrusions, etc. Dependent. If these setting ranges are inappropriate, the influence of stress based on the lattice constant difference becomes large as described above, and the number of dislocations in the substrate layer tends to increase, which is not desirable.
[0042]
In addition, since the lateral thickness, width, or diameter in the vicinity of the top of the protrusion has an optimum value or an appropriate range as described above, the shape of the top surface, bottom surface, or horizontal section of the protrusion is at least A locally closed shape (island shape) or a convexly closed shape toward the outside is preferable. More preferably, the shape of the top surface, the bottom surface, or the horizontal cross section is substantially circular or substantially regular polygonal. Etc. are good. With such a setting, it becomes easy to reliably realize the optimum value or the appropriate range in any horizontal direction.
[0043]
Also, 17th Means above 1st to 16th In any one method, various etching and electron beam irradiation treatments are performed before the crystal growth step. ,light Chemical treatment, chemical treatment, or cutting and polishing Other The crystal growth of the group III nitride compound semiconductor in this exposed region is deteriorated or changed by degrading or changing the crystallinity or molecular structure of at least a part of the valley between the protrusions of the base substrate by physical treatment of It is to reduce the speed a.
By this means, the difference (b−a) in the crystal growth rate can be further increased. Therefore, according to this means, the crystal growth rate in the vicinity of the top of the protrusion is relatively increased. The stress based on the difference in the lattice constant between them is relaxed, and dislocations and cracks are less likely to occur in the substrate layer.
[0044]
Also, 18th In any one of the separation steps described above, the means leaves a substrate composed of a base substrate and a substrate layer in the reaction chamber of the growth apparatus, so that ammonia (NH _Three ) With the gas flowing in the reaction chamber, the substrate is cooled to approximately room temperature at a cooling rate of approximately “−100 ° C./min to −0.5 ° C./min”.
For example, the above separation step can be performed by such means while maintaining the crystallinity of the substrate layer in good quality.
[0045]
Also, 19th The means is that at least after any one of the above-described separation steps, the broken debris of the protrusions remaining on the back surface of the substrate layer Turn into It is to provide a debris removal step that is removed by chemical or physical processing.
According to this means, when an electrode such as a semiconductor light emitting device is formed on the back surface of the substrate layer (the surface on which the base substrate is peeled off), current unevenness and electrical resistance generated near the interface between the electrode and the substrate layer Therefore, it is possible to reduce the driving voltage or improve the light emission intensity.
[0046]
Furthermore, by removing the broken debris from the protrusions, when the electrode is also used as a reflector such as a semiconductor light emitting device, the absorption and scattering of light near the mirror surface is reduced and the reflectance is improved. The emission intensity is improved.
In addition, for example, when this debris removal step is performed by physical processing such as polishing, even the buffer layer on the back surface of the substrate layer is removed, or the flatness of the back surface of the substrate layer is improved. Therefore, it is possible to further reinforce the above-mentioned effects such as suppression of current unevenness and electrical resistance, or reduction of light absorption and scattering near the mirror surface.
[0047]
[0048]
Also, 20th Means above 1st to 19th A group III nitride compound semiconductor light emitting device is manufactured by crystal growth using a semiconductor crystal manufactured by a semiconductor crystal manufacturing method according to any one means as a crystal growth substrate.
According to this means, a group III nitride compound semiconductor light-emitting element can be produced or facilitated from a semiconductor with good crystallinity and low internal stress.
The above-described problems can be solved by the above means.
[0049]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on specific examples. However, the present invention is not limited to the following examples.
Hereinafter, the outline of the manufacturing procedure of the semiconductor crystal (crystal growth substrate) in the embodiment of the present invention will be exemplified.
[0050]
[1] Projection forming process
As shown in FIG. 2, a substantially cylindrical projection 101a having a diameter of about 1 μm and a height of about 1 μm is formed on the Si (111) surface of a single crystal base substrate 101 made of silicon by dry etching using photolithography. Were formed at an interval of about 2 μm. As the arrangement form, the protrusion 101a was formed so that the center of the cylindrical bottom surface of the protrusion 101a was arranged on each lattice point of a two-dimensional triangular lattice having a substantially equilateral triangle having a side of about 2 μm. However, the thickness of the base substrate 101 was about 200 μm.
[0051]
[2] Crystal growth process
In this crystal growth process, as shown in FIG. 4, the growth process is performed until the crystal growth surface is connected to each other from the upper surface (initial state) of the protrusion 101a to grow into a series of substantially planar shapes. It implemented according to the vapor phase epitaxy method (MOVPE method), and the growth process until this board | substrate layer (crystal layer) grew to about 200 micrometers thick film was implemented according to the hydride vapor phase epitaxy method (HVPE method) after that.
In this crystal growth process, ammonia (NH _Three ) Gas, carrier gas (H ₂ , N ₂ ), Trimethylgallium (Ga (CH _Three ) _Three ) Gas (hereinafter referred to as “TMG”), and trimethylaluminum (Al (CH _Three ) _Three ) Gas (hereinafter referred to as “TMA”) was used.
[0052]
(A) First, the base substrate 101 (FIG. 2) provided with the protrusion 101a is cleaned by organic cleaning and acid treatment, and is attached to a susceptor placed in a reaction chamber of a crystal growth apparatus, and is at normal pressure. H ₂ The base substrate 101 was baked at a temperature of 1100 ° C. while flowing into the reaction chamber.
[0053]
(B) Next, on the base substrate 101, according to the MOVPE method, H ₂ , NH _Three , TMG and TMA were supplied to form an AlGaN buffer layer (substrate layer first layer) 102a. The crystal growth temperature of the AlGaN buffer layer 102a was about 1100 ° C., and the film thickness was about 0.3 μm. (Figure 3)
(C) On this AlGaN buffer layer (substrate layer first layer) 102a, a part of the substrate layer second layer, that is, a GaN layer 102b having a thickness of about 5 μm, is ₂ , NH _Three And TMG were supplied to grow a crystal at a growth temperature of 1075 ° C. As a result of this step, as shown in FIG. 4, a part of the second substrate layer (GaN layer 102b) grew in the lateral direction, and a large cavity was formed on the side of the trough, that is, the protrusion 101a.
At this time, the TMG supply rate was about 40 μmol / min, and the crystal growth rate of the second substrate layer (GaN layer 102b) was about 1 μm / Hr.
[0054]
(D) Then, according to the hydride vapor phase epitaxy method (HVPE method), the above-mentioned GaN layer (substrate layer second 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.
[0055]
[3] Separation process
(A) After the above crystal growth step, ammonia (NH _Three The base substrate 101 and the substrate layer 102 (consisting of the AlGaN buffer layer 102a and the GaN layer 102b) were cooled to substantially room temperature while the gas was allowed to flow into the reaction chamber of the crystal growth apparatus. The cooling rate at this time was about “−50 ° C./min to −5 ° C./min”.
[0056]
(B) Thereafter, when these were taken out from the reaction chamber of the crystal growth apparatus, a GaN crystal separated from the base substrate 101 was obtained. However, this crystal was such that a small part of the AlGaN buffer layer 102a and a broken part of the protrusion 101a remained on the back surface of the GaN layer 102b.
[0057]
[4] Broken debris removal process
After the above separation step, the fracture debris of the protrusion 101a made of Si remaining on the back surface of the GaN crystal was removed by an etching process using a mixed solution in which nitric acid was added to hydrofluoric acid.
[0058]
With the above manufacturing method, a high-quality GaN crystal (GaN layer 102b) having a film thickness of about 200 μm and excellent crystallinity, that is, a desired semiconductor substrate independent of the base substrate 101 could be obtained.
[0059]
In the above embodiment, as illustrated in FIG. 2, the protrusions and valleys of the base substrate are constituted by a vertical surface and a horizontal surface. . Accordingly, the cross-sectional shape of the valley formed on the base substrate illustrated in FIG. 2C is formed in, for example, a substantially U-shape or a substantially V-shape other than the substantially rectangular concave shape. Generally, 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 partial fragment of a base substrate having protrusions and a semiconductor crystal grown thereon, for explaining the operation of the present invention.
FIG. 2 is a schematic perspective view (a), a plan view (b), and a 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 schematic perspective view (a), a plan view (b), and a sectional view (c) of a base substrate 101 on which a first substrate layer (AlGaN buffer layer) 102a is formed.
FIG. 4 is a schematic perspective view (a), a plan view (b), and a cross-sectional view (c) of a base 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 semiconductor crystal on a conventional base substrate.
[Explanation of symbols]
101 ... Base substrate (Si substrate)
101a ... Projection
102 ... Substrate layer (nitride semiconductor layer)
102a: substrate layer first layer (AlGaN buffer layer)
102b ... Substrate layer second layer (GaN single crystal layer)

Claims (20)

A method of obtaining a semiconductor crystal independent from the base substrate by forming a substrate layer made of a group III nitride compound semiconductor on the base substrate using lateral crystal growth action,
A protrusion forming step of forming a large number of protrusions on the base substrate;
Crystal growth of the substrate layer until at least a part of the surface of the protrusion is the first growth surface on which the substrate layer starts crystal growth, and the growth surfaces are connected to each other to grow to at least a series of substantially flat surfaces. Crystal growth process
A separation step of separating the substrate layer and the base substrate by breaking the protrusion,
By cooling or heating the substrate layer and the base substrate, a stress based on a difference in thermal expansion coefficient between the substrate layer and the base substrate is generated, and the protrusion is broken using the stress. A method for producing a semiconductor crystal. A method of obtaining a semiconductor crystal by forming a substrate layer made of a group III nitride compound semiconductor on a base substrate using a lateral crystal growth action,
A protrusion forming step of forming a large number of protrusions on the base substrate;
Crystal growth of the substrate layer until at least a part of the surface of the protrusion is the first growth surface on which the substrate layer starts crystal growth, and the growth surfaces are connected to each other to grow to at least a series of substantially flat surfaces. And a crystal growth step
In the crystal growth step, by adjusting the raw material supply amount q of the group III nitride compound semiconductor,
The difference (b) between the crystal growth rate a of the group III nitride compound semiconductor in the at least part of the exposed region of the valley between the projections of the base substrate and the crystal growth rate b at the top of the projection. -A) is controlled to a substantially maximum value. In the crystal growth step, by adjusting the raw material supply amount q of the group III nitride compound semiconductor,
The difference (b) between the crystal growth rate a of the group III nitride compound semiconductor in the at least part of the exposed region of the valley between the projections of the base substrate and the crystal growth rate b at the top of the projection. 2. The method for producing a semiconductor crystal according to claim 1 , wherein -a) is controlled to a substantially maximum value. 4. The method for producing a semiconductor crystal according to claim 2, wherein the raw material supply amount q is 1 μmol / min or more and 100 μmol / min or less. 5. The method of manufacturing a semiconductor crystal according to claim 1 , wherein silicon (Si) or silicon carbide (SiC) is used as a material for the base substrate. Si (111) is used as the material of the base substrate,
In the protrusion forming step, the exposed area of the valley between the protrusions of the base substrate, according to claim 1 to claim, characterized in that the Si (111) surface to form the protrusion so as not to expose 6. The method for producing a semiconductor crystal according to any one of 5 above. 2. The method according to claim 1, further comprising a step of forming a buffer layer made of “Al _x Ga _1-x N (0 <x ≦ 1)” on at least a surface of the protruding portion after the protruding portion forming step. 7. The method for producing a semiconductor crystal according to any one of items 6 . The method of manufacturing a semiconductor crystal according to claim 7 , wherein the buffer layer is formed to have a film thickness equal to or less than a vertical height of the protrusion. 9. The method of manufacturing a semiconductor crystal according to claim 1 , wherein in the crystal growth step, the thickness of the substrate layer is set to 50 μm or more. The crystal growth method according to any one of claims 1 to 9, wherein, in the crystal growth step, the crystal growth method is changed in the middle from a crystal growth method having a low crystal growth rate to a crystal growth method having a high crystal growth rate. A method for producing a semiconductor crystal according to Item . 11. The protrusion according to claim 1 , wherein in the protrusion forming step, the protrusion is formed so that the protrusions are arranged at substantially equal intervals or at a substantially constant period. Manufacturing method of semiconductor crystal. 12. The semiconductor crystal according to claim 11 , wherein, in the projecting portion forming step, the projecting portions are formed on lattice points of a two-dimensional triangular lattice based on a substantially equilateral triangle having a side of 0.1 [mu] m or more. Manufacturing method. 13. The method according to claim 1 , wherein, in the protrusion forming step, a horizontal cross-sectional shape of the protrusion is formed into a substantially regular triangle, a substantially regular hexagon, a substantially circular, or a quadrangle. The manufacturing method of the semiconductor crystal of description. 14. The method of manufacturing a semiconductor crystal according to claim 1 , wherein, in the protrusion forming step, an interval between the protrusions is 0.1 μm or more and 10 μm or less. The semiconductor crystal manufacturing method according to any one of claims 1 to 14, wherein, in the protruding portion forming step, a vertical height of the protruding portion is set to 0.5 µm or more and 20 µm or less. Method. 16. The method according to claim 1 , wherein, in the projecting portion forming step, a lateral thickness, width, or diameter of the projecting portion is set to 0.1 μm or more and 10 μm or less. A method for producing a semiconductor crystal. Before the crystal growth step,
Various etching, electron beam irradiation treatment, optical histological processing, chemical treatment, walk by physical treatment,
By reducing or changing the crystallinity or molecular structure of at least a part of the exposed region of the valley between the protrusions of the base substrate, the crystal growth rate a of the group III nitride compound semiconductor in the exposed region is increased. The method for manufacturing a semiconductor crystal according to any one of claims 1 to 16 , wherein the semiconductor crystal is reduced. In the separation step,
The substrate composed of the base substrate and the substrate layer is left in the reaction chamber of the growth apparatus, and a substantially constant flow rate of ammonia (NH ₃ ) gas is allowed to flow into the reaction chamber.
18. The substrate according to claim 1 or any one of claims 3 to 17, wherein the substrate is cooled to substantially room temperature at a cooling rate of approximately "-100 [deg.] C./min to -0.5 [deg.] C./min". A method for producing a semiconductor crystal according to Item . At least after the separation step,
Claim 1 or characterized in that it has a debris removing step of removing by the protrusions break debris to-chemical or physical processing of remaining on the back surface of the substrate layer, of claims 3 to 18 The manufacturing method of the semiconductor crystal of any one . 21. A group III nitride system produced by crystal growth using the semiconductor crystal produced by the method for producing a semiconductor crystal according to claim 1 as a crystal growth substrate. A method for producing a compound semiconductor light emitting device.

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