JP2001176813A - Method for manufacturing nitride semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a nitride semiconductor substrate which can obtain a nitride semiconductor substrate by satisfactorily removing a heterogeneous substrate of sapphire used to grow a nitride semiconductor substrate. SOLUTION: At a 1st stage, a base layer 3 is formed of a nitride semiconductor on a heterogeneous transparent substrate 1. At a 2nd stage, a surface where a nitride semiconductor can be grown laterally is exposed on a flank of recessed part, by making the base layer 3 uneven by etching up to the heterogeneous substrate 1. At a 3rd stage, a 1st nitride semiconductor 4 having dislocation reduced is formed by growing the 1st nitride semiconductor 4 on the uneven base layer 3, a gap is formed between the heterogeneous substrate 1 at the bottom of the recessed part and the 1st nitride semiconductor 4. At a 4th stage, the surface of the heterogeneous substrate 1 where the base layer 3 is not formed is irradiated with an electromagnetic wave, to separate the heterogeneous substrate on the interface between the base layer and heterogeneous substrate, thereby removing the heterogeneous substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light emitting device such as a light emitting diode (LED) and a laser diode (LD), a light receiving device such as a solar cell and an optical sensor, or an electronic device such as a transistor and a power device. Nitride semiconductors (In _X Al _Y Ga _{1 -XYN} , 0 ≦ X, 0 ≦
The present invention relates to a method for manufacturing a nitride semiconductor substrate used for an element or the like comprising Y, X + Y ≦ 1), and more particularly to a method for manufacturing a nitride semiconductor substrate by separating a heterogeneous substrate such as sapphire from a nitride semiconductor.

[0002]

2. Description of the Related Art In recent years, LEDs made of nitride semiconductors having good light emission output have been put to practical use, and LDs made of nitride semiconductors having good device characteristics such as life characteristics have been increasingly used. .

[0003] For example, Appl. Phys. Let
t. , Vol. 72, no. 16,20 April 1
998 pp. In the literature of 2014-2016, a method of growing GaN by a growth method capable of reducing dislocations by actively utilizing the lateral growth of a nitride semiconductor (hereinafter, may be simply referred to as ELOG growth). Describes an LD formed by growing an element structure on a GaN substrate consisting of only GaN obtained by the method described above. According to the above document, the same element structure is used for a substrate from which insulating sapphire is removed and a substrate having sapphire after growing GaN with reduced dislocations on the sapphire substrate by ELOG growth. An experiment is conducted in which two types of LDs are fabricated by forming them and the life characteristics of the LDs are compared. As a result, the LD on the substrate having sapphire has a continuous oscillation of about 200 hours at room temperature, while the LD on the GaN substrate from which the sapphire has been removed has a continuous oscillation of 78 hours under the same conditions.
0 hours or more. Such a difference in the life characteristics is that, in an LD having a sapphire substrate, heat generated by driving the element is difficult to dissipate because the sapphire is insulative, whereas the sapphire is removed by polishing to remove GaN.
It is presumed that in an LD having a GaN substrate composed of only GaN, the heat dissipation is good, so that a difference occurs in the progression speed of the element deterioration. Therefore, by removing the insulating sapphire and improving the heat dissipation, the life characteristics can be improved.

[0004]

SUMMARY OF THE INVENTION However, ELO
After G growth, the step of polishing and removing the sapphire substrate includes:
Not only does sapphire be hard, it takes much time to work, but care must be taken not to chip or break the GaN substrate, which complicates the manufacturing process.

On the other hand, as a method of separating sapphire from GaN other than polishing, for example, Appl. Phys. L
ett. 72 (5), 2 February 1998
pp. 599-601 has GaN on a sapphire substrate.
Is grown, and the grown GaN surface is fixed on a Si wafer via epoxy to form a structure of sapphire / GaN / epoxy / Si, and then KrF from the sapphire side.
Irradiation of pulsed excimer laser, sapphire and GaN
Describes a method of separating sapphire from GaN by separating the sapphire from the GaN on a shared surface in contact with the GaN. In this method, the laser irradiation causes the GaN to absorb the laser light on the shared surface where the GaN and sapphire are in contact with each other, causing decomposition of the GaN,
Although sapphire can be separated from GaN, sapphire cracks due to the gas pressure of N ₂ gas generated by the decomposition of GaN, and the cracks cause nicks on the GaN surface in contact with sapphire. I do. If such a scuffed scratch is present on the GaN surface, for example, a microcrack may occur. When microcracks occur, it is conceivable to cause deterioration of device characteristics such as deterioration of life characteristics and reduction of yield. Furthermore, if there is a scoring flaw on the surface that has been in contact with the GaN sapphire, it becomes difficult to form an n-electrode directly on this surface. And the number of work steps may increase, which may cause a decrease in yield. LD
It is desired to make device characteristics such as life characteristics good and to improve the yield in mass production, etc. in order to commercialize the device.

Accordingly, an object of the present invention is to provide a method for manufacturing a nitride semiconductor substrate which can obtain a nitride semiconductor substrate by satisfactorily removing a heterogeneous substrate such as sapphire used for growing a nitride semiconductor. That is.

[0007]

That is, the object of the present invention is to
This can be achieved by the following configurations (1) to (8). (1) A first step of growing a base layer made of a nitride semiconductor on a first surface of a transparent heterogeneous substrate having a first surface and a second surface and made of a material different from a nitride semiconductor A second step of, after the first step, partially etching the underlayer to a heterogeneous substrate to form irregularities, and exposing a surface on which the nitride semiconductor can grow in the lateral direction on the side surface of the concave part; ,
After the second step, a first nitride semiconductor is grown on the underlayer having the unevenness to form the first nitride semiconductor with reduced dislocation, and the first heterogeneous substrate at the bottom of the concave portion and the first nitride semiconductor are formed.
A third step of forming a gap between the substrate and the nitride semiconductor, and after the third step, irradiating the second surface of the heterogeneous substrate with an electromagnetic wave to separate at the interface between the base layer and the heterogeneous substrate And a fourth step of removing the dissimilar substrate by the method. (2) The method for manufacturing a nitride semiconductor substrate according to (1), wherein the unevenness has a stripe shape. (3) The method according to (1), wherein the unevenness formed in the second step has a shape formed by etching to a depth of 1000 angstroms or more from a contact surface between the underlayer and the dissimilar substrate. Alternatively, the method for manufacturing a nitride semiconductor substrate according to (2). (4) The method for manufacturing a nitride semiconductor substrate according to (1), wherein the thickness of the first nitride semiconductor grown in the third step is 100 μm or more. (5) The first nitride semiconductor in the third step has a growth rate of 0.5 μm on the underlayer having irregularities.
a third step of growing the second nitride semiconductor at a rate of not less than m / hour and not more than 10 μm / hour, and after the step 3-1, a growth rate of not less than 10 μm / hour and not more than 500 μm / hour. The method of manufacturing a nitride semiconductor substrate according to the above (1) or (4), wherein the method is formed by the step 3-2 of growing a nitride semiconductor. (6) The method for manufacturing a nitride semiconductor substrate according to (1), wherein the upper surface of the projections of the unevenness formed in the second step is an underlayer. (7) The method according to (1), wherein the upper surface of the projections of the irregularities formed in the second step is an underlayer covered with a protective film made of a material on which a nitride semiconductor is unlikely to grow or does not grow. The method for producing a nitride semiconductor substrate according to 1). (8) The method for manufacturing a nitride semiconductor substrate according to (1), wherein the electromagnetic wave is an electromagnetic wave having a wavelength of 370 nm or less.

That is, according to the present invention, as described above, when performing ELOG growth capable of reducing dislocations on a transparent dissimilar substrate, ELOG
By performing a specific ELOG growth method in which a void is partially generated near the contact surface between the heterogeneous substrate and the nitride semiconductor by LOG growth, Ga is generated by electromagnetic waves, for example, laser irradiation.
Since the N ₂ gas generated by the decomposition of N spreads into the voids formed between the heterogeneous substrate and the nitride semiconductor, cracking of sapphire due to gas pressure is prevented, and GaN caused by cracking of sapphire is caused. It can also suppress scouring.
Further, in the ELOG growth used in the present invention,
Since the base layer made of the nitride semiconductor is partially etched to the heterogeneous substrate to form irregularities, a gap is formed at the bottom of the concave portion, and the generation of the gap substantially brings the heterogeneous substrate into contact with the nitride semiconductor. Because there are fewer parts
The area of GaN decomposed by the laser irradiation is reduced, and the heterogeneous substrate can be satisfactorily separated from the nitride semiconductor.

As described above, the present invention is directed to a specific ELOG growth in which dislocations are reduced, a contact area between a heterogeneous substrate and a nitride semiconductor is small, and a void is formed between the heterogeneous substrate and the nitride semiconductor. And the step of removing a dissimilar substrate such as sapphire from the nitride semiconductor by laser irradiation or the like, whereby the dissimilar substrate can be separated well and a nitride semiconductor with reduced dislocations can be obtained. it can. Further, in the present invention, the N ₂ gas generated by the decomposition of GaN due to the irradiation of the electromagnetic wave spreads in the gap formed at the bottom of the concave portion, so that it does not cause the crack of the heterogeneous substrate or the generation of scuffing of GaN. on top,
It is considered that the gentle gas pressure of the N ₂ gas spread in the gap facilitates the separation of the different kinds of substrates.

Further, in the present invention, if the unevenness formed by partially etching the underlayer is in the form of a stripe, the gap formed between the heterogeneous substrate and the underlayer is in the form of a stripe, so that the gas can be favorably formed. This is preferable because it spreads in the voids and can more favorably prevent cracks caused by the gas pressure of the dissimilar substrate, and also facilitates good separation of the contact portion between the dissimilar substrate and the underlayer. In addition, if the shape of the concavo-convex is a stripe shape, a portion where dislocation is favorably reduced is formed in a similar stripe shape above the concave portion. It is preferable because a good laser element and the like can be formed in terms of characteristics and the like.

Furthermore, in the present invention, the fact that the irregularities formed in the second step are cut away from the contact surface between the underlayer and the dissimilar substrate to a depth of 1000 Å or more by etching, It is preferable to do.
The depth to which the different type of substrate is cut is not particularly limited as long as it is not less than 1000 Å, but the upper limit of the depth is preferably a depth which is smaller than the thickness of the different type of substrate and does not complicate the cutting operation. For example, it is preferably 1.0 μm or less. Further, it is preferable that the heterogeneous substrate is shaved at a depth of 2,000 to 3,000 angstroms in terms of formation of voids, reduction of dislocations, and work efficiency. Further, when the shaved depth is within the above range, voids are formed as spaces in which the N ₂ gas generated by the decomposition of GaN spreads favorably, and cracks in sapphire and scuffing of the nitride semiconductor due to the cracks are reduced. Can be prevented.

Still further, in the present invention, the thickness of the first nitride semiconductor grown in the third step is 100 μm.
Or more, preferably 200 μm or more, more preferably 30 μm or more.
When it is 0 μm or more, more preferably 500 μm or more, when irradiating electromagnetic waves or when forming an element structure,
This is preferable in terms of handling properties and the like, by preventing cracking or chipping of the nitride semiconductor substrate. Although the upper limit of the thickness of the first nitride semiconductor is not particularly limited, it is appropriately adjusted in consideration of an apparatus, a formation time, and the like, and is, for example, 1 mm or less.

Still further, in the present invention, the first nitride semiconductor in the third step is formed on the underlying layer having irregularities by growing the second nitride at a growth rate of 0.5 μm / hour or more and 10 μm / hour or less. Step 3-1 for growing the semiconductor, and after this step, the growth rate is set to 10 μm / hour or more.
When formed by the step 3-2 of growing the third nitride semiconductor at a speed of not more than 00 μm / hour,
Growth method with a low growth rate in the step of, for example, MOCVD,
In this case, it is preferable to reduce the occurrence of abnormal growth and the like when growing a thick nitride semiconductor by a growth method having a high growth rate in the 3-2 step, for example, HVPE.
When a thick nitride semiconductor is grown by a method with a slow growth rate, a long-time reaction occurs, and abnormal growth and the like are likely to occur. A third nitride semiconductor is preferably obtained. When a thin film nitride semiconductor is grown by a method with a high growth rate, the film thickness is difficult to adjust, but when a nitride semiconductor is grown by a growth method with a low growth rate, the nitride semiconductor on the side surface of the concave portion Is preferable because the growth in the lateral direction can be favorably performed and a second nitride semiconductor in which dislocations are favorably reduced can be obtained.

Still further, in the present invention, the upper surface of the projections of the concavities and convexities formed in the second step is an underlayer, or the upper surface of the projections is a protective film made of a material on which a nitride semiconductor is unlikely to grow or does not grow. The covered underlayer is preferable in that dislocations are reduced and voids are formed between the underlayer and the heterogeneous substrate. The ELOG growth in the present invention is not particularly limited as long as a void is formed at the bottom of the concave portion. For example, preferably, the upper surface of the convex portion of the concave and convex portions is a base layer or a protective film as described above. Method.

Still further, in the present invention, the electromagnetic wave
When the electromagnetic wave has a wavelength of 370 nm or less, the nitride semiconductor that can transmit the transparent heterogeneous substrate satisfactorily and is in contact with the heterogeneous substrate below the uneven protrusions can be decomposed satisfactorily. It is preferable because different kinds of substrates can be separated well.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to FIGS. FIG. 1 is a schematic cross-sectional view of an embodiment of the present invention, in which electromagnetic waves are irradiated from a heterogeneous substrate side after ELOG growth. 2 to 4 are schematic cross-sectional views of a wafer obtained by each step of ELOG growth used in the present invention. FIG. 5 is a plan view of the main surface of the substrate for explaining the direction of the stripes of the concavo-convex formed on the underlayer. FIG. 6 is a schematic cross-sectional view showing an enlarged part of a substrate in which the main surface of a heterogeneous substrate used in the present invention is stepped off-angle. FIG. 7 is a unit cell diagram showing the plane orientation of sapphire.

According to the present invention, as shown in FIG. 1, by growing a first nitride semiconductor 4 by ELOG growth on a base layer 4 having irregularities, the heterogeneous substrate 1 at the bottom of the concave portion and the first nitride semiconductor 4 are grown. A gap is formed between the semiconductor and the semiconductor 4,
By irradiating electromagnetic waves from the different substrate 1 side of the wafer in such a state, the wafer can be separated from the common surface where the different substrate 1 and the underlayer 3 are in contact, and the different substrate 1 can be removed.

As described above, the method for manufacturing a nitride semiconductor substrate according to the present invention includes at least the following first steps to
This is a method for producing a nitride semiconductor substrate by the fourth step. First, as shown in FIG.
Of a different kind of transparent substrate 1 having a first surface and a second surface and capable of transmitting electromagnetic waves made of a material different from that of the nitride semiconductor.
Is grown on the surface of the substrate.

Next, as shown in FIGS. 3 (a-1) and 3 (b-1), in the second step, the underlayer 3 made of a nitride semiconductor is partially etched to the heterogeneous substrate 1 to form irregularities. Is formed, a surface on which the nitride semiconductor can grow in the lateral direction is exposed on the side surface of the concave portion.

Next, FIG. 3 (a-2, a-3), (b-
As shown in (2, b-3), in the third step, the first nitride semiconductor 4 is grown on the base layer 3 having the unevenness, and the recess is formed by growing the first nitride semiconductor 4. A gap is formed between the bottom heterogeneous substrate 1 and the first nitride semiconductor 4. Since the inside of the recess is less likely to grow on the surface of the heterogeneous substrate 1 exposed at the bottom of the recess as compared to the nitride semiconductor surface of the underlying layer 3 exposed at the side surface,
The first nitride semiconductor 4 selectively starts growing from the lateral direction on the nitride semiconductor of the underlayer 3 exposed on the side surface of the concave portion, and grows from both side surfaces of the concave portion.
Are joined in the recess and cover the recess. At this time, since the first nitride semiconductor 4 hardly grows on the surface of the heterogeneous substrate 1 exposed at the bottom of the concave portion, a gap is formed between the heterogeneous substrate 1 at the bottom of the concave portion and the first nitride semiconductor 4. Is formed.

Next, as shown in FIG. 1, in a fourth step, an electromagnetic wave is irradiated from the second surface of the heterogeneous substrate 1 to form a nitride semiconductor on the contact surface of the underlayer 3 in contact with the heterogeneous substrate 1. To dissociate the heterogeneous substrate 1 and to spread the N ₂ gas generated by the decomposition along the voids, thereby preventing cracking of the heterogeneous substrate 1 caused by the gas pressure, It is also possible to prevent scuffing of the underlayer 3 caused by cracking of the substrate 1. Such first
By performing Steps 4 to 4, the heterogeneous substrate 1 is removed, and a nitride semiconductor substrate composed of only a nitride semiconductor with reduced dislocations can be manufactured. Hereinafter, each step of the present invention will be specifically described.

[First Step] The first step is a step of growing a base layer 3 on a heterogeneous substrate 1 as shown in FIG. In the present invention, the heterogeneous substrate 1 is not particularly limited as long as it is transparent at least to the extent that electromagnetic waves can be transmitted. Specific examples thereof include C-plane, R-plane, and A-plane.
Sapphire, spinel (Mg
A1 ₂ O ₄ ), an insulating substrate such as SiC (6H, 4H,
3C), a substrate material different from a conventionally known nitride semiconductor, such as ZnS, ZnO, GaAs, Si, and an oxide substrate lattice-matched with a nitride semiconductor can be used. Preferred heterosubstrates include sapphire and spinel. When sapphire is used as a dissimilar substrate, the orientation of the nitride semiconductor at the top of the protrusion and the side surface of the recess when the unevenness is formed tends to be specified depending on which surface is the main surface of the sapphire. Since the growth rate of the nitride semiconductor is slightly different depending on the type, the main surface may be selected so that a plane orientation that facilitates growth comes to the side surface of the concave portion. Further, the first surface and the second surface of the heterogeneous substrate 1 are described for convenience in order to show that the surface on which the underlayer 3 and the like are grown and the surface on which the electromagnetic wave is irradiated are different.

In the present invention, the underlayer 3 is not particularly limited as long as it is at least one or more nitride semiconductors. Preferably, the buffer layer 12 is grown at a low temperature on the heterogeneous substrate 1 and then grown at a high temperature. It is preferable to grow the nitride semiconductor 13 in terms of crystallinity and ELOG growth. As the buffer layer 12, AlN, GaN, AlG
aN, InGaN or the like is used. The buffer layer 12
For example, at a temperature of 900 ° C. or lower and 300 ° C. or higher, a film thickness of 0.
It is grown at 5 μm to 10 Å. As described above, when the buffer layer 12 is formed on the heterogeneous substrate 1 at a temperature of 900 ° C. or less, the heterogeneous substrate 1 and the nitride semiconductor 1 grown at a high temperature are formed.
3, the crystal defects of the nitride semiconductor 13 grown at a high temperature tend to be reduced. The nitride semiconductor 13 grown at a high temperature is not particularly limited, but is preferably, for example, undoped (in a state where impurities are not doped;
dope) GaN or GaN doped with at least one n-type impurity such as Si, Ge, and S can be used. The nitride semiconductor 13 grown at a high temperature is grown on the heterogeneous substrate 1 at a high temperature, for example, specifically, higher than about 900 ° C. to 1100 ° C., preferably 1050 ° C. When grown at such a temperature, the nitride semiconductor 13 grown at a high temperature
Becomes a single crystal.

The film thickness of the nitride semiconductor 13 grown at a high temperature is such that the upper surface of the convex portion of the unevenness formed in the second step is
The preferred film thickness differs depending on whether [a-1 to a-3 in FIG. 3] or [b-1 to b-3 in FIG. 3] which is the underlayer 3 covered with the protective film. Further, the shape of the unevenness formed in the second step, for example, the size of the width of the concave portion and the width of the convex portion is different.

Hereinafter, the case where the upper surface of the convex portion of the unevenness formed in the second step is the underlayer 3 [(a-1) to (a-
3)] is described. When the upper surface of the convex portion is the underlayer 3, the thickness of the nitride semiconductor 13 grown at a high temperature is not particularly limited, but the unevenness is set so as to suppress the vertical growth inside the concave portion and promote the lateral growth. The thickness is preferably such that the shape can be adjusted, and is formed to a thickness of at least 500 angstroms or more, preferably 5 μm or more, more preferably 10 μm or more. When the width of the opening of the concave portion is increased, it is preferable that the shape of the concave portion is made deep in order to prevent the nitride semiconductor from growing on the bottom surface of the concave portion.
Is appropriately adjusted depending on the width of the recess opening. Therefore, when increasing the width of the opening, the thickness of the nitride semiconductor 13 grown at a high temperature is preferably increased in the above thickness range. Subsequently, the second step in the case where the upper surface of the convex portion is the base layer 3 will be described below.

[Second Step: When the Upper Surface of the Convex Part is the Underlayer 3] Next, as shown in FIG. 3A-2, the underlayer 3 is formed on the heterogeneous substrate 1. (Buffer layer 12, nitride semiconductor 13 grown at a high temperature)
Is partially etched to the heterogeneous substrate 1 to form irregularities, and the nitride semiconductor constituting the base layer 3 is exposed on the side surfaces of the concave portions.

In the second step, the heterogeneous substrate 1 is partially
To form the unevenness by etching until the nitride semiconductor constituting the base layer 3 is exposed at least on the side surface of the concave portion,
Furthermore, a depression may be formed from the surface of the underlayer 3 toward the heterogeneous substrate 1 so that the heterogeneous substrate 1 is exposed at the bottom of the concave portion. The underlayer 3 may be provided with irregularities in any shape. . As the shape of the unevenness, for example, it can be formed into a random depression, a stripe, a grid, or a dot.
The preferred shape is a stripe shape. With this shape, abnormal growth is small, it is preferable to be buried more flat, and when forming a laser element, a ridge-shaped stripe is formed above a concave portion with less dislocation. It is preferable because it becomes easy.

The unevenness partially provided on the underlayer 3 is only required to expose at least the dissimilar substrate 1, and is preferably cut to a depth of 1000 Å or more from the contact surface between the underlayer 3 and the dissimilar substrate 1. It is preferable to form a gap. The preferred depth for forming the void is
There is no particular limitation as long as the thickness is 1000 angstroms or more, but the upper limit of the depth is preferably smaller than the thickness of the heterogeneous substrate so that the work of shaving is not complicated.
For example, the thickness is preferably 1.0 μm or less. Further, it is preferable that the heterogeneous substrate 1 is shaved at a depth of 2000 Å to 3000 Å in terms of formation of voids, reduction of dislocations, and work efficiency. Further, when the shaved depth is within the above range, voids are formed as spaces in which the N ₂ gas generated by the decomposition of GaN spreads favorably, and cracks in sapphire and scuffing of the nitride semiconductor due to the cracks are reduced. Can be prevented.

Further, as described above, the heterogeneous substrate 1 is provided at the bottom of the concave portion.
Is preferably exposed and preferably etched to a specific range of depth, in that dislocation is reduced by ELOG growth. That is, when the heterogeneous substrate 1 is at least exposed as described above, the growth from the bottom of the concave portion is easily suppressed, and the dislocation of the first nitride semiconductor 4 that grows to a thick film from the opening of the concave portion is easily reduced. It is preferable. Furthermore, when the heterogeneous substrate 1 is shaved at the above-described depth, the strain of the crystal at the junction of the first nitride semiconductor 4 growing from the side surface of the concave portion can be relaxed, and the occurrence of dislocation can be prevented. Good sex,
This is preferable because a nitride semiconductor having a good surface state can be grown. It is considered that the relaxation of the strain at the joint part is related to the void formed at the bottom of the concave part. In other words, although the bonding portion inside the concave portion tends to grow slightly downward, it is considered that the crystallinity is improved because the strain is reduced due to the presence of the void. Further, when voids are generated on the dissimilar substrate 1 which has been shaved, it becomes easy to distinguish between the surface of the upper portion of the concave portion having less dislocations and the surface of the upper portion of the convex portion having more dislocations. Ridge-shaped stripes can be easily formed, which is preferable from the viewpoint of improving the yield in the manufacturing process.

The shape of the concavities and convexities is not particularly limited, such as the length of the side surface of the concave portion, the width of the upper portion of the convex portion and the width of the bottom portion of the concave portion. It is preferable that the first nitride semiconductor 4 growing on the film is adjusted so as to grow laterally from the side surface of the concave portion. When the shape of the unevenness is a stripe shape, the shape of the stripe is not particularly limited. For example, the stripe width (width of the upper portion of the convex portion) is 1 to 20 μm, preferably 1 to 10 μm, and the stripe interval (width of the lower portion of the concave portion). Is 10 to 40 μm, preferably 15 to 35 μm. Having such a stripe shape is preferable in terms of reducing dislocations and improving the surface state. Further, when the width of the concave portion is within the above range, when forming a ridge-shaped stripe on the upper portion of the concave portion with less dislocation, it is formed so as to avoid the central portion of the concave portion and to be located in the portion with less dislocation. Preferred. It is possible to increase the portion of the first nitride semiconductor 4 growing from the opening of the concave portion by increasing the width of the bottom portion of the concave portion and narrowing the width of the upper portion of the convex portion. In this way, the dislocation is reduced. Can be more. When the width of the bottom of the recess is increased, it is preferable to increase the depth of the recess in order to prevent the growth in the vertical direction that may grow from the bottom of the recess.

As a method of providing the unevenness in the second step,
Any method may be used as long as the first nitride semiconductor 4 can be partially removed, for example, preferably etching. Dicing may be used as long as the crystallinity is not impaired. When the unevenness is partially (selectively) formed on the underlying layer 3 by etching, a mask such as a stripe or a grid is formed using mask patterns of various shapes in the photolithography technique, and a resist is formed. The pattern can be formed by forming a pattern on the underlayer 3 and etching it. The photomask is removed after etching to form irregularities. When dicing is performed, for example, it can be formed in a stripe shape or a grid shape.

The method of etching the underlayer 3 in the second step includes wet etching, dry etching and the like, and dry etching is preferably used to form a smooth surface. Dry etching includes, for example, devices such as reactive ion etching (RIE), reactive ion beam etching (RIBE), electron cyclotron etching (ECR), and ion beam etching. It can be formed by etching a nitride semiconductor. For example,
Specific means for etching a nitride semiconductor described in Japanese Patent Application Laid-Open No. H8-17803 previously filed by the present applicant can be used. In addition, when the unevenness is formed by etching, the etched surface (concave side surface) has a shape in which the end surface is substantially perpendicular to the heterogeneous substrate as shown in FIG. It may have a shape or a shape formed in a step shape. From the viewpoint of reduction of dislocations and good surface condition, vertical, inverted mesa and forward mesa are more preferable, and more preferable is vertical.

In the second step, when the shape of the unevenness is a stripe, as shown in FIG. 5, the stripe is an A-plane of sapphire, as shown in FIG. Either left or right, θ =
0.1 ° to 0.7 °, preferably θ = 0.1 ° to 0.5
It is preferable to form the crystal by shifting the crystal by a good angle because a good crystal having a more flat growth surface can be obtained. By the way, when θ in FIG. 5 is 0 °, the surface may not be flat, and when the element structure is formed on the growth surface in such a state, there is a tendency that the element characteristics are easily deteriorated. A flat surface is also preferable in terms of improving the yield.

Hereinafter, the case where the upper surface of the convex portion of the unevenness formed in the second step is the underlayer 3 covered with the protective film [(b-1) to (b-3) of FIG. 3] Describe. In the case where the upper surface of the convex portion is the underlayer 3 covered with the protective film 15,
Although the thickness of the nitride semiconductor 13 grown at a high temperature grown in the first step is not particularly limited, when forming the unevenness on the underlayer 3, the thickness of the underlying layer 3 exposed on the side surface of the recess relative to the bottom of the recess is reduced. In order to selectively give priority to the growth of the first nitride semiconductor 4, a film thickness enough to form irregularities in a shape capable of controlling the growth rate of the first nitride semiconductor 4, specifically, 1
It is desirable to form the layer with a thickness of at least 00 Å, preferably about 1 to 10 μm, and more preferably 1 to 5 μm. Next, a second step in the case where the upper surface of the convex portion is the underlayer 3 covered with the protective film 15 will be described.

[Second Step: In the Case of Having a Protective Film on the Upper Surface of the Convex Portion] Next, as shown in FIG. The base layer 3 (buffer layer 12, high-temperature grown nitride semiconductor 13) is partially etched to the heterogeneous substrate 1 to form irregularities, the nitride semiconductor constituting the base layer 3 is exposed on the side surfaces of the concave portions, and the upper surface of the convex portions is exposed. This is a step of forming the protective film 15 in FIG.

By forming projections and depressions on the underlayer 3, the end faces of the first nitride semiconductor layer 2 and the bottom faces of the recesses are exposed as surfaces on which growth is possible. A protective film 15 made of a material on which the nitride semiconductor is unlikely to grow or does not grow is formed on the upper surface of the convex portion. Further, the shape of the unevenness is adjusted so that the growth of the nitride semiconductor on the end surface of the underlayer 3 on the side surface of the concave portion has priority over the growth on the surface of the heterogeneous substrate 1 on the bottom surface of the concave portion.

The shape of the unevenness in this case is not particularly limited, but may be any shape as long as the nitride semiconductor is formed so as to grow preferentially on a specific surface as described above. Adjusts the length of the end surface of the underlayer 3 exposed on the side surface of the concave portion [d in FIG. 3 (b-1)] and the width of the opening portion of the concave portion [w in FIG. 3 (b-1)]. It is formed. More preferably, the shape of the unevenness is such that the relationship between the length (d) of the exposed end face of the base layer 3 and the width (w) of the opening of the concave portion, w / d is 0 <w / d ≦ 5, Preferably 0 <w /
When formed so as to satisfy d ≦ 3, more preferably 0 <w / d ≦ 1, the growth rate can be controlled well and the growth from the end face of the underlayer 3 can be promoted. Thus, by giving priority to the growth from the end surface of the underlayer 3, the growth of the nitride semiconductor on the bottom surface of the concave portion can be easily interrupted. It is sufficient that at least the heterogeneous substrate 1 is exposed on the bottom surface of the concave portion. Preferably, the heterogeneous substrate 1 is similar to the case where the upper portion of the convex portion is the base layer 3 (in the case of FIG. 3A-1). It is preferable that the etching is performed at a depth in order to reduce dislocations and remove the heterogeneous substrate 1.

As described above, when the heterogeneous substrate 1 is exposed at the bottom of the concave portion, preferably when the heterogeneous substrate 1 is etched to a specific depth, the growth of the first nitride semiconductor 4 to be grown in the third step Is performed preferentially on the underlying layer 3 exposed on the side surface of the concave portion, rather than on the heterogeneous substrate 1 on the bottom portion of the concave portion. At the bottom portion of the concave portion, a gap is formed between the first nitride semiconductor 4 and the heterogeneous substrate 1. In the gap, N ₂ gas generated by the decomposition of the nitride semiconductor by the electromagnetic wave in the fourth step is collected,
Cracking of the heterogeneous substrate 1 caused by the gas pressure and scouring of the underlayer caused by the cracking can be prevented. Further, it is preferable that the heterogeneous substrate 1 is etched to a depth in the above range, because the gas can be satisfactorily spread into the voids and the heterogeneous substrate 1 can be more effectively prevented from cracking. Further, when the heterogeneous substrate 1 is etched at a depth in the above range, the growth in the vertical direction from the bottom of the concave portion can be more favorably prevented, which is preferable in terms of reducing dislocations.

In the second step, the upper surface of the convex portion is
5 means that the underlying layer 3 is partially etched and the upper surface of the convex portion is formed in accordance with the shape of the unevenness appearing on the surface of the underlying layer 3, for example, as shown in FIG. , Protective film 1
5 is formed on the upper surface of the protrusion of the underlayer 3. The shape of the surface on which the protective film 15 is formed on the upper surface of the convex portion is not particularly limited, and may be any shape. For example, in addition to the above-described relationship of w / d, the underlayer 3 on which the unevenness is further formed is viewed from above. The shape is
It can be formed in random depressions, stripes, grids, or dots. It is preferably a stripe shape, and if such a shape is used, the dislocation is reduced and the first shape is obtained.
This is preferable because the surface condition of the nitride semiconductor is good, and it is also preferable in that a void at the bottom of the concave portion is formed and the foreign substrate 1 is removed.

When the concavities and convexities are in the form of a stripe, for example, specifically, the stripe width is 10 to 20 μm and the stripe interval (opening of the concave portion)
Of 2 to 5 μm can be formed. The above range is preferable in terms of reducing dislocations and forming voids.

As a method for forming the irregularities in the second step, any method may be used as long as the method can partially remove the underlayer 3, but etching is preferable.
Dicing may be used as long as the crystallinity is not impaired. When the unevenness is partially (selectively) formed on the underlying layer 3 by etching, a mask such as a stripe or a grid is formed using mask patterns of various shapes in the photolithography technique, and a resist is formed. The pattern can be formed by forming a pattern on the underlayer 3 and etching it. When dicing is performed, for example, it can be formed in a stripe shape or a grid shape.

In the method of etching the nitride semiconductor in the second step, the upper surface of the convex portion is formed on the base layer 3 [FIG.
To a-3)] can be used. Further, in the case where the unevenness is formed by etching, the etched surface is made of a heterogeneous substrate 1 as shown in FIG.
The shape of the base layer 3 may be substantially perpendicular to the end face of the base layer 3 or may be a forward mesa shape or an inverted mesa shape.
The shape is not particularly limited as long as the nitride semiconductor 4 can be grown. In the present invention, FIGS. 3 (b-1) to 3 (b-3)
In the case of (1), when the etched surface of the irregularities is a forward mesa shape or an inverted mesa shape, the length of the end surface of the underlayer 3 on the side surface of the concave portion is the height from the surface of the underlayer 3 (the upper surface of the convex portion) to the bottom surface of the concave portion. Is the length (d) of the end face of the underlayer 3.

As the protective film 15 used in the second step, whether a nitride semiconductor does not grow on the surface of the protective film 15
Alternatively, a material having a property of not easily growing can be used.
As the protective film 15, for example, silicon oxide (SiO _x ), titanium oxide (TiO _x ), zirconium oxide (ZrO _x ),
Oxides such as aluminum oxide (Al ₂ O ₃ ), nitrides such as silicon nitride (Si _x N _y ), and these multilayer films,
Metals having a melting point of 1200 ° C. or more, such as i, Mo, Ti, and W, can be given. These protective film materials are
It withstands the growth temperature of the nitride semiconductor of 600 ° C. to 1100 ° C. and has a property that the nitride semiconductor does not grow or hardly grows on its surface. In order to form the protective film material on the surface of the nitride semiconductor, for example, a vapor deposition technique such as vapor deposition, sputtering, or CVD can be used.

In the second step, the protective film 15
The method of forming the irregularities on the underlayer 3 is slightly different depending on whether the method is etching or dicing. First, when the unevenness is formed by etching, after forming the protective film 15 on the underlayer 3, a resist film is formed thereon, the pattern is transferred, exposed, and developed to partially form the protective film 15, and The unevenness is formed by etching the ground layer 3. Next, when a step is formed by dicing, a protective film 15 is formed on the surface of the underlayer 3 and irregularities are formed on the underlayer 3 in a desired shape from above by using a dicing saw. Only the protective film 15 remains.

The thickness of the protective film 15 is not particularly limited.
In the step, the first nitride semiconductor 4 which starts growing preferentially from the end face of the underlying layer 3 in the concave portion grows on the protective film 15 as if the first nitride semiconductor 4 grows in the lateral direction. Preferably, it is adjusted so as to be easily performed. For example,
It is considered that when the protective film 15 is formed to be thin, the first nitride semiconductors 4 that have grown adjacently on the protective film 15 are more easily bonded to each other. When the protective film 15 is formed on the upper surface of the convex portion, as one embodiment for preventing the vertical growth of the first nitride semiconductor 4 on the bottom surface of the concave portion, at least exposing the heterogeneous substrate 1 to the lower portion of the concave portion; Although adjusting the length of the exposed end face of the first nitride semiconductor layer and the width of the opening of the concave portion has been described, the present invention is not limited to this.

Next, the third step in the case where the upper surface of the convex portion is the underlayer 3 and the case where the upper surface is the underlayer 3 covered with the protective film 15 will be described. [Third Step: When the Upper Surface of the Convex Portion is the Underlayer 3 and the Protective Film] The third step is as shown in FIG. 3 (a-3, a-4) (b-
As shown in (3, b-4), this is a step of growing a first nitride semiconductor 4 on the underlayer 3 having the irregularities. The first nitride semiconductor 4 is not particularly limited, but is specifically preferably, for example, undoped (undoped, undope) GaN or S
GaN doped with at least one of n-type impurities such as i, Ge, and S can be used. The first nitride semiconductor 4 has an unevenness at a high temperature, for example, specifically, higher than about 900 ° C. to 1100 ° C., preferably 1050 ° C., similarly to the high-temperature grown nitride semiconductor 13 constituting the underlayer 3. It is grown on the formation 3. When grown at such a temperature, the first nitride semiconductor 4 becomes a single crystal. The thickness of the first nitride semiconductor 4 is not particularly limited.
When it is not less than 00 μm, preferably not less than 200 μm, more preferably not less than 300 μm, and still more preferably not less than 500 μm, when irradiating an electromagnetic wave or forming an element structure, the nitride semiconductor substrate is prevented from cracking or chipping. It is preferable in terms of handling properties and the like. The upper limit of the film thickness of the first nitride semiconductor 4 is not particularly limited, but is appropriately adjusted in consideration of an apparatus, a formation time, and the like, and is, for example, 1 mm or less.

Further, in the present invention, the first nitride semiconductor 4 in the third step is formed as shown in FIG.
As shown in 4), a third step of growing the second nitride semiconductor 17 at a growth rate of 0.5 μm / hour or more and 10 μm / hour or less on the uneven layer 3,
After this step, the growth rate is 10 μm / hour or more and 500 μm or more.
Preferably, it is formed by the third and second steps of growing the third nitride semiconductor 18 at m / hour or less. That is, dislocations can be satisfactorily reduced by a growth method having a low growth rate in the 3-1st step, for example, MOCVD.
-2, a growth method with a high growth rate, for example, HVP
In E, when a thick nitride semiconductor is grown, abnormal growth and the like are less likely to occur. When a thick nitride semiconductor is grown by a method having a low growth rate, a long-time reaction is caused and abnormal growth or the like is easily caused. However, when a nitride semiconductor is grown by a growth method having a high growth rate, abnormal growth can be prevented, which is preferable.
When a thin film nitride semiconductor is grown by a method with a high growth rate, the film thickness is difficult to adjust, but when a nitride semiconductor is grown by a growth method with a low growth rate, the nitride semiconductor on the side surface of the concave portion Of the first nitride semiconductor (No. 3) having good lateral growth and reduced dislocations
Step -1 is preferable because a second nitride semiconductor) can be obtained.

The 3-1st step and the 3-2th step will be described below in order. First, the step 3-1 is performed as shown in FIG.
As shown in 4), on the underlying layer 3 having irregularities, the growth rate is 0.5 μm / hour or more and 10 μm / hour or less, and the dislocation is reduced by utilizing the lateral growth of the nitride semiconductor. This is a step of growing the second nitride semiconductor 17. The growth rate for growing the second nitride semiconductor 17 is, as described above, 10 μm / hour or less, 0.5 μm / hour or more, preferably 7 μm / hour or less, 1 μm / hour or more,
More preferably, it is not more than 5 μm / hour and not less than 1.5 μm / hour. When the growth rate is in the above range, propagation of dislocations can be favorably suppressed during ELOG growth, and it is preferable to adjust the thickness of the second nitride semiconductor 17. A specific growth method having such a growth rate is not particularly limited, but includes, for example, MOCVD.

The second nitride semiconductor 17 is not particularly limited, but is preferably a nitride semiconductor made of GaN. Further, third nitride semiconductor 22 may be undoped or doped with impurities. The third nitride semiconductor 22 is preferably undoped in terms of crystallinity. Further, when the p-type impurity and / or the n-type impurity are doped at the time of the ELOG growth in the second step, similarly to the case of the ELOG growth in the first step, the lateral growth of the nitride semiconductor is increased. It is promoted and is preferable in terms of reduction of dislocations and prevention of generation of voids at a junction between adjacent nitride semiconductors. The thickness of the second nitride semiconductor 17 is not particularly limited and is at least a thickness capable of covering at least unevenness, for example, a specific thickness is preferably 1 to 50 μm, more preferably 2 to 50 μm. 40 μm, more preferably 7 to 20 μm
m. When the film thickness is within the above range, the unevenness can be covered well, which is preferable in terms of suppressing the propagation of dislocations.

Next, as shown in FIG.
In the step -2, the growth rate is set to 500 μm / m on the second nitride semiconductor 17 formed in the step 3-1.
The third nitride semiconductor 1 at a time of 10 μm / hour or less
Grow 8. In the step 3-2, the growth rate for growing the third nitride semiconductor 18 is 500 μm as described above.
m / hour or less 10 μm / hour or more, preferably 100 μm
m / hour or less and 50 μm / hour or more. When the growth rate of the third nitride semiconductor 18 is in the above range, when growing the third nitride semiconductor 18 to the above film thickness,
It is preferable that abnormal growth can be prevented and the growth surface of the third nitride semiconductor 18 becomes clean. Although a specific method for keeping the growth rate in the above range is not particularly limited, for example, HVPE and the like can be mentioned.

The third nitride semiconductor 18 grown in the step 3-2 is not particularly limited, but a nitride semiconductor made of GaN is preferable from the viewpoint of crystallinity and the like. The third nitride semiconductor 18 may be undoped or doped with an impurity, but is preferably undoped from the viewpoint of crystallinity.

The thickness of the third nitride semiconductor 18 is grown to be larger than the thickness of the second nitride semiconductor 17. Third
The thickness of the nitride semiconductor 18 is not particularly limited, but may be a physical value such as when irradiating an electromagnetic wave in the fourth step, removing the heterogeneous substrate 1 after irradiating the electromagnetic wave, or forming a device structure. It is desirable that the film thickness is not less than the film thickness that can withstand the strength and does not easily cause chipping or cracking, and the size of the apparatus and the range in which the operation is easy. For example, the specific thickness of the third nitride semiconductor 18 is preferably 50 μm to 1000 μm.
m, more preferably 80 μm to 500 μm. A film thickness in such a range is preferable because occurrence of chipping or cracking can be prevented.

Further, in growing the second nitride semiconductor 17 in the 3-1 step, impurities (for example, S
i, Ge, Sn, Be, Zn, Mn, Cr, and Mg
), Or by adjusting the molar ratio of the group III and group V components (the molar ratio of III / V), which are the raw materials of the nitride semiconductor, to grow the substrate in the horizontal direction. It is preferable in that the dislocation is promoted as compared with the growth in the direction, and is preferable in that the surface state of the surface of the second nitride semiconductor 17 is improved.

The second nitride semiconductor 17 may be grown under a pressure equal to or higher than the normal pressure when growing the second nitride semiconductor 17. It is preferable that the second nitride semiconductor 17 be grown under a reaction condition of normal pressure or higher in order to improve the surface condition of the surface of the second nitride semiconductor 17. Here, the pressurized condition of the normal pressure or more means that the reaction is performed under the condition that the pressure is intentionally applied by adjusting the apparatus and the like from the normal pressure (pressure in which no pressure is intentionally applied). Is to do. The specific pressure is not particularly limited as long as it is equal to or higher than normal pressure, but is preferably normal pressure (approximately 1 atm) to 2.5 atm, and preferable pressure is normal pressure to 1.5 atm. is there. It is preferable to grow the second nitride semiconductor 17 under such a pressure condition in that the surface state of the surface of the second nitride semiconductor 17 is improved.

In the third step, the upper surface of the convex portion is
In the case of, inside the concave portion, it is considered that there are a type that grows laterally from the side surface of the concave portion and a type that grows vertically from the bottom portion of the concave portion. The nitride semiconductors 4 are bonded to each other to suppress the growth from the bottom of the concave portion. In addition, since the heterogeneous substrate 1 is exposed at the bottom of the concave portion, the growth of the first nitride semiconductor 4 (including the second nitride semiconductor 17) starts with the lateral growth selectively on the side surface of the concave portion. The first nitride semiconductors 4 grown from the side surfaces are joined to each other. As a result, almost no dislocation is observed in the first nitride semiconductor 4 grown from the opening of the concave portion. It is considered that the vertical growth from the bottom of the recess has a slower growth rate or does not grow compared to the lateral growth from the side of the recess. As described above, when the surface of the bottom of the recess is made of a different kind of substrate 1 such as sapphire, preferably, the different kind of substrate 1 is cut to the above-described depth, the growth of the first nitride semiconductor 4 from the bottom of the recess is made. It is suppressed, and the growth of the first nitride semiconductor 4 from the side surface of the concave portion is improved, which is preferable in terms of reducing dislocation. Further, in the portion of the first nitride semiconductor 4 grown from the upper surface of the convex portion when the upper surface of the convex portion is the underlayer 3, slightly more dislocations are observed than those grown from the opening portion of the concave portion. However, the nitride semiconductor which starts growing vertically in the upper part of the convex part also tends to grow in the horizontal direction toward the opening of the concave part rather than the growth rate in the vertical direction. Dislocations are reduced as compared with the case where they are made.
Also, the second and third layers are formed on the first nitride semiconductor 4.
By repeating the above step, dislocations in the upper part of the protrusion can be eliminated. In addition, the first grown from the upper part of the convex part and the inside of the concave part.
Are joined during the growth process.

Further, in the third step, when growing the first nitride semiconductor 4, the surface of the first nitride semiconductor 4 is abnormal by adjusting the pressure to a pressure equal to or higher than the normal pressure. A good flat surface state with little growth is obtained.

When the second and third steps are repeated as described above, a protrusion formed on the first nitride semiconductor 4 is formed on the underlayer 3 above the recess formed on the underlayer 3. Irregularities are formed partially on the first nitride semiconductor 4 so that concave portions formed in the first nitride semiconductor 4 are located above the convex portions, respectively. Then, a new nitride semiconductor is grown on the first nitride semiconductor 4 having the unevenness.
The new nitride semiconductor is preferably a nitride semiconductor having few dislocations as a whole. The first as a new nitride semiconductor
A nitride semiconductor 4 is grown. Further, when the second and third steps are repeated, the first nitride semiconductor 4 is grown thinner than when it is not repeated, and the bottom surface of the concave portion formed in the first nitride semiconductor 4 is reduced. It is preferable that the first nitride semiconductor 4 is etched so as to be on one surface of a heterogeneous substrate such as sapphire, because a new nitride semiconductor having less dislocation and a good surface state is obtained.

On the other hand, in the third step, when the upper surface of the convex portion is the underlayer 3 covered with the protective film, the growth inside the concave portion is almost the same as described above, but the growth on the upper surface of the convex portion is performed. The first nitride semiconductor 4 is slightly different. That is, since the protective film 15 is formed on the upper surface of the convex portion, the first nitride semiconductor 4 does not directly grow on the upper surface of the convex portion, but the first nitride semiconductor 4 that has grown from inside the concave portion is formed. It grows by lateral growth on the protective film 15 and covers the protective film 15.
Thus, the first nitride semiconductor 4 does not grow directly,
The fact that the first nitride semiconductor 4 grown from the inside of the recess grows in the lateral direction is as if it grew on the protective film 15. Then, the first growing from inside the concave portion
Both of the nitride semiconductor 4 and the first nitride semiconductor 4 grown on the upper surface of the convex portion are nitride semiconductors with reduced dislocations and with almost no dislocations on the protective film 15. Also, when the protective film 15 is used, the second step and the third step are performed on the first nitride semiconductor 4 in order to further reduce the dislocation.
May be repeated.

Hereinafter, another preferred embodiment of the heterogeneous substrate 1 will be described. As the heterogeneous substrate 1, it is preferable to use a substrate in which the main surface of a material to be a heterogeneous substrate is off-angled, and further a substrate whose stepped off-angle is used (see FIG. 6). When a substrate with an off-angle is used, three-dimensional growth is not observed on the surface, and step growth appears, so that the surface tends to be flat. Furthermore, when the direction (step direction) along the step of the sapphire substrate that is off-angled in a step shape is formed perpendicular to the A-plane of sapphire, the step surface of the nitride semiconductor is aligned with the cavity direction of the laser. This is preferable because the laser light is less likely to be irregularly reflected due to the surface roughness.

As a more preferable heterogeneous substrate 1, (00
01) Sapphire whose main surface is [C-plane], (112−
0) Sapphire whose main surface is plane [A], or (111)
It is a spinel whose surface is the main surface. Here, the heterogeneous substrate 1
When the sapphire has a (0001) plane [C-plane] as a main surface, the stripe shape of the irregularities formed on the underlayer 3 is perpendicular to the (112-0) plane [A-plane] of the sapphire. It has a stripe shape shifted by 0.1 ° to 0.7 ° to the left or right from the axis [for example, from a nitride semiconductor such as <1-100] [M-axis direction], a vertical axis as shown in FIG. To form a stripe with a shift of θ = 0.1 ° to 0.7 ° to one of the right and left sides], and the off angle off angle θ (θ shown in FIG. 6) is preferably 0.
1 ° to 0.5 °, more preferably 0.1 ° to 0.2 °.

In the case of sapphire having the (112-0) plane [A-plane] as the principal plane, the stripe shape of the irregularities is defined by an axis perpendicular to the (11-02) plane [R-plane] of the sapphire. As in the case of the above-mentioned A-plane, it is preferable to have a shifted stripe-like shape. In the case of a spinel having a (111) -plane as a main surface, the uneven stripe-like shape is formed on the (110) -plane of the spinel. On the other hand, it is preferable that the sapphire has a stripe shape as in the case of sapphire. Here, the case where the unevenness is a stripe shape has been described.
Since the nitride semiconductor easily grows in the lateral direction on the (110) plane of the spinel and the spinel, it is preferable to consider the formation of the unevenness so that the end faces of the first nitride semiconductor 4 and the like are formed on these planes. . As described above, it is preferable in terms of surface morphology to form a stripe with a slight offset from the vertical axis with respect to each surface.

The heterogeneous substrate 1 used in the present invention will be described in more detail with reference to the drawings. FIG. 7 is a unit cell diagram showing the crystal structure of sapphire. First, a case will be described in which sapphire having a C surface as a main surface is used, and unevenness is formed in a stripe shape with reference to the sapphire A surface. For example, FIG. 5 is a plan view of a sapphire substrate on the main surface side. In this figure, the sapphire C plane is the main surface, and the orientation flat (orientation flat) surface is the A surface. As shown in FIG. 5, stripes parallel to each other are formed in a direction in which the uneven stripes are shifted by θ = 0.1 ° to 0.7 ° to the left or right of the axis perpendicular to the A-plane. As shown in FIG. 5, when a nitride semiconductor is selectively grown on a sapphire C plane, the nitride semiconductor tends to grow in a direction parallel to the A plane in the plane and hard to grow in a direction perpendicular to the A plane. It is in. Therefore, when the stripes are provided in the direction slightly shifted as described above with respect to the A plane, the nitride semiconductors between the stripes are connected to facilitate the growth, and it is thought that the ELOG growth can be easily performed. I'm not sure. Further, the surface morphology is improved.

Next, when a sapphire substrate having the A surface as the main surface is used, similarly to the case where the C surface is the main surface, for example, when the orientation flat surface is the R surface, the same as in the case of the A surface. By forming stripes parallel to each other in a direction slightly deviated from an axis perpendicular to the R-plane, the nitride semiconductor tends to grow easily in the stripe width direction. Layers can be grown and better surface morphology can be obtained.

Next, also for spinel (MgAl ₂ O ₄ ), the growth of the nitride semiconductor is anisotropic, and the growth surface of the nitride semiconductor is (111) plane, and the orientation flat surface is (11).
When the plane is the 0) plane, the nitride semiconductor tends to grow in a direction parallel to the (110) plane. Therefore, (11
If the stripes are formed in a direction substantially perpendicular to the 0) plane, preferably in a slightly displaced direction as in the case of the above-mentioned sapphire, the nitride semiconductor layer and the adjacent nitride semiconductor are connected at the upper part of the protective film, and dislocations are formed. Crystal with few defects can be grown. The spinel is not shown in the figure because it is tetragonal.

In the following, the direction along the step of the sapphire substrate that has been off-angled corresponds to the A of the sapphire substrate.
The case of being formed perpendicular to the plane will be described with reference to FIG. The dissimilar substrate 1, such as sapphire, which is off-angled in a step shape, has a substantially horizontal terrace portion A and a step portion B as shown in FIG. The surface irregularities of the terrace portion A are small and are formed almost regularly. The step portion having such an off angle θ is desirably formed continuously over the entire substrate, but may be formed particularly partially. The off-angle θ indicates the angle between a straight line connecting the bottoms of a plurality of steps and the horizontal plane of the uppermost step as shown in FIG. In addition, the off-angle of the heterogeneous substrate is 0.1 ° to 0.5 °.
°, preferably 0.1 ° to 0.2 °. When the off-angle is in the above range, the surface of the first nitride semiconductor 2 has a fine streak-like morphology, and the epitaxial growth surface (the surface of the second nitride semiconductor 3) has a wavy morphology, which is obtained using this substrate. The nitride semiconductor device is smooth and has characteristics such as long life, high efficiency, high output, and improved yield.

Next, a fourth step of removing the heterogeneous substrate 1 by irradiating an electromagnetic wave will be described. [Fourth Step] In a fourth step, as shown in FIG. 1, after growing the base layer 3 and the first nitride semiconductor 4 on the first surface of the heterogeneous substrate 1, Irradiation of electromagnetic waves from the second surface decomposes the underlayer 3 on the surface in contact with the heterogeneous substrate 1 and separates the heterogeneous substrate 1 and the underlayer 3 at the shared surface in contact therewith. This is the step of removing. Although there is no particular limitation on the electromagnetic wave, an electromagnetic wave that can absorb at least the nitride semiconductor constituting the underlayer 3 and further decompose the nitride semiconductor to remove the heterogeneous substrate 1 can be used. The electromagnetic wave that can be absorbed by the nitride semiconductor is an electromagnetic wave having a value larger than the band gap energy of the nitride semiconductor forming the underlayer 3, such as a laser. As a specific laser, any laser having an oscillation wavelength that can be absorbed by the underlayer 3 may be used. For example, various lasers that can oscillate laser light having an oscillation wavelength of about 370 nm or less are preferable. Such a laser having an oscillation wavelength of 370 nm or less is not particularly limited. For example, an excimer laser [ArF (193n)
m), KrF (248.5 nm), XeCl (308 n
m) etc.].

The irradiation time of the electromagnetic wave is not particularly limited, and the electromagnetic wave may be irradiated from the second surface of the heterogeneous substrate 1 so that the underlayer 3 is decomposed and the heterogeneous substrate 1 can be removed. Is appropriately adjusted according to the type of For example, as a specific example, a KrF excimer laser is used, the laser light is made into a linear shape of 1 mm × 50 mm, and the entire second surface of the heterogeneous substrate 1 is scanned and irradiated with the laser light.

When irradiating the second surface of the heterogeneous substrate 1 with an electromagnetic wave, the surface of the first nitride semiconductor 4 formed on the first surface of the heterogeneous substrate 1 via the underlayer 3 is removed. An electromagnetic wave may be emitted from the second surface of the heterogeneous substrate 1 while being fixed to a support. When the wafer is fixed and irradiated with electromagnetic waves in this way,
It is preferable in that cracking of the wafer is prevented. When fixing the surface of the first nitride semiconductor 4 to the support, waxes, a metal material, an adhesive, or the like may be used.

Before the surface of the first nitride semiconductor 4 is fixed to a support with a metal or the like, protection is performed so that the crystallinity of the first nitride semiconductor 4 is not impaired by formation of a metal or the like. A film may be formed. The protective film is not particularly limited, but SiO ₂ , SiN or the like can be used. Examples of the support include, but are not particularly limited to, a material that can withstand high temperatures, is hard and is hardly cracked, and has physical strength. For example, sapphire or the like can be specifically used.

When a nitride semiconductor such as the base layer 3 is grown on the heterogeneous substrate 1, warpage occurs due to a difference in lattice constant. However, when irradiating an electromagnetic wave such as laser light, the second semiconductor substrate 1 It is preferable to make the surface flat so that the electromagnetic wave can be satisfactorily irradiated and the dissimilar substrate 1 can be removed well.

When the second surface of the heterogeneous substrate 1 is irradiated with an electromagnetic wave, the nitride semiconductor on the contact surface between the heterogeneous substrate 1 and the underlayer 3 is decomposed, and the heterogeneous substrate 1 can be removed. When removing the foreign substrate 1 by irradiating the wafer with an electromagnetic wave while fixing the wafer to the support, after removing the foreign substrate 1, the metal material, waxes, adhesive, or the like used for fixing is removed from each material. Removed by a suitable method. The method of removing the material used for fixing is not particularly limited, but a method that does not adversely affect the crystallinity and the like of the nitride semiconductor is preferable.

The device structure constituting the nitride semiconductor element formed on the nitride semiconductor substrate obtained by the method for manufacturing a nitride semiconductor substrate of the present invention is not particularly limited, and any device structure may be grown. Is also good. The nitride semiconductor substrate obtained by the method of the present invention has a reduced number of dislocations, can prevent cracking of the heterogeneous substrate 1, and has no scuffs formed in the nitride semiconductor. An element having a device structure formed thereon has good element characteristics. For example, the nitride semiconductor constituting the nitride semiconductor element is not particularly limited, and it is sufficient that at least an n-type nitride semiconductor, an active layer, and a p-type nitride semiconductor are stacked. For example, an n-type nitride semiconductor having an n-type nitride semiconductor layer having a superlattice structure as an n-type nitride semiconductor layer and capable of forming an n-electrode in the n-type layer having the superlattice structure is formed. And the like. An example of the active layer is an active layer having a multiple quantum well structure containing InGaN. In addition, any other structure such as an electrode and an element shape may be applied to other structures for forming the nitride semiconductor element structure.
Although one embodiment of the nitride semiconductor device has been described as a reference example in an example, the present invention is not limited to this.

In the present invention, the method for growing the nitride semiconductor is not particularly limited, but is MOVPE (metal organic chemical vapor deposition), HVPE (halide vapor deposition), MBE.
All methods known for growing nitride semiconductors, such as (molecular beam epitaxy) and MOCVD (metal organic chemical vapor deposition) can be applied. The preferred growth method is
This is an MOCVD method, and crystals can be grown cleanly. However, since the MOCVD method takes time, when the film thickness is large, it is preferable to perform the method with a short time. Further, it is preferable to appropriately select various methods for growing a nitride semiconductor depending on the purpose of use and grow the nitride semiconductor.

[0074]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment which is an embodiment of the present invention will be described below. However, the present invention is not limited to this.

Example 1 Each step in Example 1 will be described with reference to FIGS.

[First Step] As shown in FIG. 6, as the heterogeneous substrate 1, the C-plane which is off-angled in a step-like manner is used as the main surface, the off-angle angle θ = 0.15 °, the step height is about 20 Å, A sapphire substrate 1 having a terrace width W of about 800 angstroms and an orientation flat surface A is used.

<Underlayer 3> On the sapphire substrate 1,
The following buffer layer 12 and nitride semiconductor 13 grown at a high temperature are grown to form the underlayer 3 (see FIG. 2). (Buffer layer 12) This sapphire substrate 1 is
And the temperature was set to 510 ° C., and hydrogen was used as a carrier gas, ammonia and TMG (trimethylgallium) were used as source gases, and Ga was placed on the sapphire substrate 1.
A buffer layer 12 of N is grown to a thickness of 200 angstroms. (Nitride semiconductor 13 grown at high temperature) After growing the buffer layer, T
Stopping only MG, raising the temperature to 1050 ° C.
When the temperature reaches 50 ° C., a high-temperature grown nitride semiconductor 13 made of undoped GaN is grown to a thickness of 5 μm using TMG and ammonia as source gases.

[Second Step] Next, after growing the buffer layer 12 and the underlying layer 3 made of the nitride semiconductor 13 grown at a high temperature, a stripe-shaped photomask is formed, and the stripe width (of the convex portion) is formed by a CVD apparatus. A patterned SiO ₂ film is formed with an upper part of 3 μm and a stripe interval (a part of the concave bottom) of 15 μm, and then a nitride semiconductor grown at a high temperature in a part where no SiO ₂ film is formed by an RIE apparatus. 13 exposes the sapphire substrate 1 and further etches the sapphire substrate 1 to a depth of approximately 2000 angstroms to form irregularities.
The surface of the nitride semiconductor constituting base layer 3 is exposed on the side surface of the concave portion. After forming the irregularities, the irregularities are formed by removing the SiO ₂ above the convexities (see FIG. 3A-1). As shown in FIG. 5, the direction of the stripes of the concavo-convex formed on the underlayer 3 is a direction shifted by 0.35 ° to the right from an axis perpendicular to the orientation flat surface.

[Step 3-1] Next, after forming irregularities on the underlayer 3, the wafer is transferred to a MOCVD reaction vessel.
At 1050 ° C., TMG, ammonia, Cp
_{2 Using} Mg (cyclopentadienyl magnesium)
A second nitride semiconductor 17 made of undoped GaN is grown to a thickness of 15 μm [see FIGS. 4 (a-4) and 3 (a-2)]. However, the growth rate of the second nitride semiconductor 17 was 3 μm / hour. In addition, a void is formed in a stripe shape at the bottom of the concave portion by the step 3-1. Also, the second nitride semiconductor 17 grown above the concave portion has almost no dislocation.

[Step 3-2] Next, a third nitride semiconductor 18 made of undoped GaN is grown on the second nitride semiconductor 17 to a thickness of 200 μm by an HVPE apparatus [FIG. 4]. (A-4) and FIG. 3 (a-3)]. However, the growth rate of the third nitride semiconductor 18 is 5
0 μm / hour.

[Fourth Step] Next, as shown in FIG.
From a surface of the sapphire substrate 1 where the third nitride semiconductor 18 is not formed, a laser beam of 1 m is output at a power of 600 J / cm ² using a KrF excimer laser having a wavelength of 248 nm.
The entire surface of the second surface of the sapphire substrate 1 on which the underlayer 3 and the like are not formed is scanned and irradiated in a linear shape of mx 50 mm. By irradiating the laser, the interface between the sapphire substrate 1 and the underlying layer 3 is decomposed, whereby the sapphire substrate 1 can be removed, and the underlying layer 3, the second nitride semiconductor 17, and the third nitride A nitride semiconductor substrate made of the semiconductor 18 can be obtained. The obtained nitride semiconductor substrate can prevent cracking of the sapphire substrate 1 when irradiating the laser, and no scuffing occurs on the surface of the underlayer 3 from which the sapphire substrate 1 has been removed. Since the substrate can be removed, the substrate has a good removal surface and reduced dislocations.

Example 2 A nitride semiconductor substrate is manufactured in the same manner as in Example 1, except that the second step is changed as follows.

[Second Step] After growing the underlayer 3, a stripe-shaped photomask is formed on the underlayer 3, and SiO 2 having a stripe width of 15 μm and a stripe interval (width of the opening of the concave portion) of 2 μm is formed by a CVD apparatus. _A protective film 15 made of ₂ is formed to a thickness of 1 μm, and then etched to the sapphire substrate 1 by the RIE device.
Is etched to a depth of about 2000 angstroms to form irregularities, thereby exposing the nitride semiconductor surface constituting the underlayer 3 (see FIG. 3 (b-1)). A protective film 15 is formed on the upper surface of the projection. As shown in FIG. 5, the direction of the stripes of the concavo-convex formed on the underlayer 3 is 0.35 to the right from the axis perpendicular to the orientation flat surface.
° formed in shifted directions.

After the second step as described above, the 3-1 step, the 3-2 step, and the fourth step are performed as in the first embodiment, and the sapphire substrate 1 is removed. Obtain a nitride semiconductor. Here, after the second nitride semiconductor 17 is grown in the step 3-1, the second nitride semiconductor 17 is grown above the protrusion covered with the protective film 15 and is grown above the recess. Almost no dislocation is observed in the second nitride semiconductor 17 thus obtained. In addition, a gap is formed between the sapphire substrate 1 and the second nitride semiconductor 17 at the bottom of the concave portion. The nitride semiconductor substrate obtained as described above can remove the sapphire substrate 1 satisfactorily by irradiating a laser beam, and has no scuffing damage as in Example 1, and also has a good reduction in dislocations. Have been.

[0085]

As described above, according to the method for manufacturing a nitride semiconductor substrate of the present invention, a gap is partially formed between a heterogeneous substrate and a nitride semiconductor grown on the heterogeneous substrate by using a specific ELOG growth. When an electromagnetic wave is applied to a heterogeneous substrate in such a state, the nitride semiconductor in contact with the heterogeneous substrate is decomposed and the heterogeneous substrate can be separated and removed. Furthermore, the nitride semiconductor is decomposed by irradiating electromagnetic waves, and the N ₂ gas generated at this time is E ₂
Spreading into the voids formed by the LOG growth, cracking of the dissimilar substrate due to gas pressure can be prevented well, and scuffing of the nitride semiconductor caused by the cracking can also be well prevented. As a result, it is possible to obtain a nitride semiconductor substrate having good crystallinity and surface state with reduced dislocations without scuffing. Furthermore, the method for manufacturing a nitride semiconductor substrate of the present invention is simplified as compared with the conventional technique, and the yield can be further improved.
Furthermore, with the manufacturing method of the present invention, a large-diameter substrate can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an embodiment of the present invention, in which a wafer is irradiated with an electromagnetic wave.

FIG. 2 is a schematic sectional view of a wafer obtained by each step of ELOG growth used in the present invention.

FIG. 3 is a schematic cross-sectional view of a wafer obtained by each step of ELOG growth used in the present invention.

FIG. 4 is a schematic cross-sectional view of a wafer obtained by each step of ELOG growth used in the present invention.

FIG. 5 is a plan view of a main surface of the substrate for explaining a stripe direction of unevenness formed on an underlayer.

FIG. 6 is a schematic cross-sectional view showing, on an enlarged scale, a part of the substrate when the main surface of the heterogeneous substrate used in the present invention is off-angled in a step shape.

FIG. 7 is a unit cell diagram showing a plane orientation of sapphire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Different substrate 3 ... Underlayer 4 ... 1st nitride semiconductor 12 ... Buffer layer 13 ... Nitride semiconductor grown at high temperature 15 ... Protective film 17 ... 2nd Nitride semiconductor 18 ... third nitride semiconductor

Continued on front page F-term (reference) 4K030 AA11 AA13 AA17 BA08 BA38 CA01 CA12 DA08 FA10 HA03 LA12 5F041 AA31 AA40 CA23 CA40 CA46 CA65 CA67 CA74 CA75 5F045 AA04 AB09 AB14 AB17 AB18 AC08 AC12 AD07 AD08 AD09 AD10 AD11 AD12 AF13 AD13 AF04 AF09 AF12 AF13 AF20 BB12 BB13 CA10 CA12 CA13 DA53 HA11 HA12

Claims (8)

[Claims] 1. A first method for growing a base layer made of a nitride semiconductor on a first surface of a transparent heterogeneous substrate having a first surface and a second surface and made of a material different from a nitride semiconductor. And after the first step, the underlayer is partially etched to a heterogeneous substrate to form irregularities, and a second surface is exposed on a side surface of the concave portion where a nitride semiconductor can be grown in a lateral direction. After the step and the second step, a first nitride semiconductor is grown on the base layer having the irregularities to form the first nitride semiconductor with reduced dislocations, and a heterogeneous substrate at the bottom of the recess is formed. A third step of forming a gap between the first substrate and the first nitride semiconductor;
A step of irradiating the surface with an electromagnetic wave and separating at the interface between the base layer and the dissimilar substrate to remove the dissimilar substrate. 2. The method for manufacturing a nitride semiconductor substrate according to claim 1, wherein the unevenness has a stripe shape. 3. The method according to claim 1, wherein the unevenness formed in the second step is 100% away from the contact surface between the underlayer and the different substrate by etching.
3. The method for manufacturing a nitride semiconductor substrate according to claim 1, wherein the method has a shape obtained by shaving at a depth of 0 Å or more. 4. 4. The method according to claim 1, wherein the thickness of the first nitride semiconductor grown in the third step is 100 μm or more. 5. The method according to claim 3, wherein the first nitride semiconductor in the third step has a growth rate of 0.
A third step of growing the second nitride semiconductor at a rate of 5 μm / hour or more and 10 μm / hour or less, and a third step of growing the second nitride semiconductor at a rate of 10 μm / hour or more and 500 μm / hour or less after the step 3-1. 3. The step of growing a nitride semiconductor according to step 3-2.
Or the method for producing a nitride semiconductor substrate according to 4. 6. The method for manufacturing a nitride semiconductor substrate according to claim 1, wherein the upper surface of the projections of the unevenness formed in the second step is an underlayer. 7. The method according to claim 1, wherein the upper surface of the convex portion of the concavo-convex formed in the second step is an underlayer covered with a protective film made of a material on which a nitride semiconductor is unlikely to grow or does not grow. A method for manufacturing the nitride semiconductor substrate according to claim 1. 8. The method according to claim 1, wherein the electromagnetic wave is an electromagnetic wave having a wavelength of 370 nm or less.