JP2021134118A - Substrate and light-emitting element - Google Patents

Abstract

To provide a substrate having an aluminum nitride layer excellent in crystallinity.SOLUTION: A substrate 10 includes an aluminum nitride layer L1 containing crystalline aluminum nitride, and a sapphire layer L2 containing crystalline α-alumina. The aluminum nitride layer L1 is directly piled on the surface of the sapphire layer L2, and the (0001) plane of the aluminum nitride is approximately parallel to the surface of the sapphire layer, and the (11-20) plane of the α-alumina is approximately parallel to the surface of the sapphire layer, and the (11-20) plane of the aluminum nitride is approximately parallel to the (1-100) plane of the α-alumina.SELECTED DRAWING: Figure 1

Description

The present invention relates to a substrate and a light emitting element.

Nitride of Group 13 element such as aluminum nitride (AlN) is a semiconductor. Nitride crystals of Group 13 elements are attracting attention as materials for light emitting devices or power transistors that emit short wavelength light from the blue band to the ultraviolet band.

For example, a light emitting element such as a deep ultraviolet light emitting diode includes a buffer layer made of AlN crystals. This buffer layer is formed on the surface of the sapphire substrate. Then, a light emitting device is manufactured by sequentially laminating nitride semiconductor layers such as an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer on the surface of the buffer layer. By interposing the buffer layer between the nitride semiconductor layer and the sapphire substrate _{, the lattice mismatch between the nitride semiconductor and sapphire (α-Al 2} O ₃ ) is suppressed, and through-dislocations due to the lattice mismatch are suppressed. It is suppressed. As a result, the crystallinity of the nitride semiconductor layer such as the light emitting layer is improved, and the luminous efficiency of the light emitting element is improved.

In the case of a general substrate used for a light emitting element, the (0001) plane of the buffer layer is formed on the (0001) plane of the sapphire substrate. On the other hand, in the case of the substrate described in Patent Document 1 below, the (0001) surface of the buffer layer is formed on the (11-20) surface of the sapphire substrate via the aluminum nitride layer, and the (1-100) surface of the buffer layer is formed. ) Plane is parallel to the (1-100) plane of the sapphire substrate. In the method for producing a substrate described in Patent Document 1 below, in order to improve the crystallinity of the buffer layer, the aluminum nitride layer and the buffer layer are formed of the sapphire substrate by direct reduction nitriding of the sapphire substrate. Formed on the surface of. Further, in the case of the substrate described in Patent Document 2 below, in order to improve the crystallinity of the buffer layer, the (0001) plane of the buffer layer is formed on the (0001) plane or the (110) plane of the sapphire substrate. Also in the method for manufacturing a substrate described in Patent Document 2 below, a buffer layer is formed on the surface of the sapphire substrate by direct reduction nitriding of the sapphire substrate.

Japanese Unexamined Patent Publication No. 2004-137142 JP-A-2019-64870

When the buffer layer is grown on the surface of the substrate described in Patent Documents 1 and 2 by the Metalorganic Chemical Vapor Deposition (MOCVD), the crystallinity of the buffer layer gives good crystallinity of the substrate. It is difficult to take over. For example, the full width at half maximum of the locking curve of the (0001) plane of the buffer layer in the Out-оf-Plane direction is larger than the full width at half maximum of the locking curve of the (0001) plane of the AlN layer originally formed on the surface of the substrate. Then, as the thickness of the buffer layer increases, the full width at half maximum of the locking curve of the (0001) plane of the buffer layer tends to increase. That is, as the buffer layer grows, the crystallinity of the buffer layer deteriorates. When the buffer layer is inferior in crystallinity, the crystallinity of the nitride semiconductor layer (light emitting layer or the like) formed on the buffer layer also deteriorates. As a result, the luminous efficiency of the light emitting element is lowered.

An object of the present invention is to provide a substrate having an aluminum nitride layer having excellent crystallinity, and a light emitting device provided with the substrate.

The substrate according to one aspect of the present invention includes an aluminum nitride layer containing crystalline aluminum oxide and a sapphire layer containing crystalline α-alumina, and the aluminum nitride layer directly overlaps the surface of the sapphire layer. The (0001) plane of aluminum oxide is substantially parallel to the surface of the sapphire layer, the (11-20) plane of α-alumina is substantially parallel to the surface of the sapphire layer, and the (11-20) plane of aluminum nitride. ) Plane is substantially parallel to the (1-100) plane of α-alumina.

The full width at half maximum (FWHM) of the locking curve of the (1-100) plane of aluminum nitride measured in the in-plane direction of the surface of the aluminum nitride layer is 0 seconds. It may be 5 seconds or more and 500 seconds or less (0 arcsecоnd or more and 500 arcsecоnds or less).

The full width at half maximum of the locking curve of the (1-100) plane of aluminum nitride measured in the in-plane direction of the surface of the aluminum nitride layer may be 50 seconds or more and 300 seconds or less.

The aluminum nitride layer may contain at least one additive element selected from the group consisting of rare earth elements, alkaline earth elements and alkali metal elements.

Of the aluminum nitride layer, the boundary region along the boundary between the aluminum nitride layer and the sapphire layer may contain an additive element, and the additive element is at least one selected from the group consisting of rare earth elements, alkaline earth elements and alkali metal elements. It may be an element, and the total content of the added elements in the boundary region may be 0.1 mass ppm or more and 200 mass ppm or less.

The thickness of the aluminum nitride layer may be 50 nm or more and 1000 nm or less.

The thickness of the aluminum nitride layer may be 50 nm or more and 500 nm or less.

RC1 (1-100) may be the locking curve of the (1-100) plane of aluminum nitride measured in the in-plane direction of the surface of the aluminum nitride layer, and RC2 (1-100) may be the locking curve of the aluminum nitride layer. Of these, the locking curve of the (1-100) plane of aluminum nitride contained in the region where the distance from the surface of the sapphire layer is 100 nm or less may be, and RC2 (1-100) is substantially parallel to the surface of the sapphire layer. It may be measured in the in-plane direction, and the half-price full width of RC1 (1-100) may be smaller than the half-price full width of RC2 (1-100).

The substrate according to one aspect of the present invention may be used as a light emitting device.

The light emitting element according to one aspect of the present invention includes the above-mentioned substrate.

The light emitting device according to one aspect of the present invention includes the above substrate, an n-type semiconductor layer overlapping the aluminum nitride layer, a light emitting layer overlapping the n-type semiconductor layer, and a p-type semiconductor layer overlapping the light emitting layer. You may be prepared.

According to the present invention, a substrate having an aluminum nitride layer having excellent crystallinity and a light emitting device including the substrate are provided.

FIG. 1 is a schematic cross-sectional view of a substrate according to an embodiment of the present invention. FIG. 2 is a schematic perspective view of the crystal structure of aluminum nitride. FIG. 3 is a schematic diagram showing a basic vector, a crystal orientation, and a crystal plane in a unit cell of the crystal structure of aluminum nitride. FIG. 4 is a perspective view and a top view of the crystal structure of α-alumina. FIG. 5 is a schematic diagram showing a basic vector, a crystal orientation, and a crystal plane in a unit cell of the crystal structure of α-alumina. FIG. 6 is a schematic view showing the orientation of the crystal planes of aluminum nitride and α-alumina contained in the substrate according to the embodiment of the present invention. FIG. 7 is a schematic view showing the orientation of the crystal planes of aluminum nitride and α-alumina contained in the conventional substrate. FIG. 8 is a schematic view showing a method of measuring a locking curve (φ scan) in the in-plane direction. FIG. 9 shows an example of RC1 (1-100) and an example of RC2 (1-100). FIG. 10 is a schematic cross-sectional view of a light emitting device including a substrate according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the drawings, equivalent components are labeled with equivalent reference numerals. The present invention is not limited to the following embodiments. X, Y and Z shown in FIGS. 1, 8 and 10 mean three coordinate axes orthogonal to each other. The directions indicated by the coordinate axes are common to FIGS. 1, 8 and 10.

(substrate)
The substrate according to this embodiment includes an aluminum nitride layer and a sapphire layer. The structure of the substrate according to this embodiment is shown in FIG. Figure 1 is a cross-section of a vertical substrate 10 on the surface _{S L2} of the surface _{S L1} and sapphire layer L2 of the aluminum nitride layer L1. As shown in FIG. 1, an aluminum nitride layer L1 is overlapped directly on the surface S _L2 of the sapphire layer L2. Surface _{S L1} of the aluminum nitride layer L1 may be flat. Surface _{S L2} of the sapphire layer L2 may also be flat. The thickness T of the aluminum nitride layer L1 in the stacking direction Z may be substantially uniform. The thickness of the sapphire layer L2 in the stacking direction Z may also be substantially uniform. The thickness of the entire substrate 10 in the stacking direction Z may also be substantially uniform.

The aluminum nitride layer L1 contains crystalline aluminum nitride (AlN). The crystalline aluminum nitride may be a single crystal of aluminum nitride. The aluminum nitride layer L1 may be composed of only crystalline aluminum nitride. The aluminum nitride layer L1 may further contain an additive element M described later in addition to the crystalline aluminum nitride. The additive element M may be contained in crystalline aluminum nitride. The aluminum nitride layer L1 may be composed of only aluminum (Al), nitrogen (N) and the additive element M. As long as the crystallinity of aluminum nitride is not impaired, the aluminum nitride layer L1 may contain other elements (impurities and the like) in addition to Al, N and the additive element M. For example, in the aluminum nitride layer L1, the boundary region along the boundary between the aluminum nitride layer L1 and the sapphire layer L2 may contain a trace amount of oxygen (O). That is, the region of the aluminum nitride layer L1 facing the sapphire layer L2 may contain a small amount of oxygen. The aluminum nitride layer L1 may be composed of only Al, N, and additive elements M and O. The boundary between the aluminum nitride layer L1 and the sapphire layer L2 may be specified by the presence or absence of nitrogen. That is, the boundary may be defined as the interface between the layer in which both Al and N are detected (aluminum nitride layer L1) and the layer in which Al and O are detected and N is not detected (sapphire layer L2).

The crystal structure of aluminum nitride contained in the aluminum nitride layer L1 is a hexagonal wurtzite type structure. The wurtzite structure of aluminum nitride is shown in FIG. The unit cell of the wurtzite type structure is shown in FIG. Atoms in FIG. 3 are omitted for the purpose of notation of the basic vector, crystal orientation and crystal plane, but aluminum is present at each of the 12 vertices of the unit cell uc1 (regular hexagonal prism) of the Ulz ore type structure. Be placed. _{A 1} , a _2, a ₃ and c in FIG. 3 are basic vectors (crystal axes) constituting the unit cell uc1 of the wurtzite type structure. orientation of a ₁ is [1000]. orientation of a ₂ is [0100]. orientation of a ₃ is a [0010]. The orientation of c is [0001]. The lengths of a ₁ , a ₂ and a ₃ are equal to each other. All of a ₁ , a ₂ and a ₃ are perpendicular to c. The _{angle formed by a 1} , a ₂ and a ₃ with each other is 120 degrees. As shown in FIGS. 2 and 3, the crystal structure of aluminum nitride has rotational symmetry with respect to the c-axis, so that the (11-20) plane, (-2110) plane, and (1-210) plane of aluminum nitride are , Equivalent in plane orientation. Therefore, the (-2110) and (1-210) planes may be considered as (11-20) planes. The angle between the (1-100) plane of aluminum nitride and the (11-20) plane of aluminum nitride is 90 degrees. Since the angle between the (11-20) plane and the (-2110) plane is 60 degrees, the angle between the (1-100) plane and the (-2110) plane is 90 degrees + 60 degrees (that is, 150 degrees). Degree). Since the angle between the (11-20) plane and the (1-210) plane is -60 degrees, the angle between the (1-100) plane and the (1-210) plane is 90 degrees -60 degrees. Degree (ie 30 degrees). Therefore, when the (-2110) and (1-210) planes are regarded as the (11-20) planes in the crystal structure of aluminum nitride, the (1-100) planes of aluminum nitride and the (11-20) planes of aluminum nitride are considered. ) The angles to the surface are 90 degrees, 150 degrees, and 30 degrees. If the angle between the (1-100) plane of α-alumina and the (1-100) plane of aluminum nitride is ± 30 degrees, the (1-100) plane of aluminum nitride and the (11-) plane of aluminum nitride 20) The angles between the planes are 90 degrees, 150 degrees, and 30 degrees, so the angle between the (1-100) plane of α-alumina and the (11-20) plane of aluminum nitride is ± 30 degrees +90 degrees, ± 30 degrees +150 degrees, and ± 30 degrees +30 degrees. That is, if the angle between the (1-100) plane of α-alumina and the (1-100) plane of aluminum nitride is ± 30 degrees, the (1-100) plane of α-alumina and the (1-100) plane of aluminum nitride The angles to the (11-20) plane are 0 degrees (180 degrees), 60 degrees and 120 degrees. Therefore, when the angle between the (1-100) plane of α-alumina and the (1-100) plane of aluminum nitride is ± 30 degrees, the (11-20) plane of aluminum nitride is that of α-alumina. It is parallel to the (1-100) plane. That is, when the angle between the (1-100) plane of α-alumina and the (1-100) plane of aluminum nitride is ± 30 degrees, the (11-20) plane, the (-2110) plane and the (1) plane are The crystal plane of any one of the −210) planes is always parallel to the (1-100) plane of α-alumina. The (11-20) plane of aluminum nitride is perpendicular to the (0001) plane of aluminum nitride. The (1-100) plane of aluminum nitride is also perpendicular to the (0001) plane of α-alumina. The (11-20) plane of aluminum nitride may be paraphrased as the a-plane of aluminum nitride. The (1-100) plane of aluminum nitride may be paraphrased as the m-plane of aluminum nitride. The (0001) plane of aluminum nitride may be paraphrased as the c-plane of aluminum nitride.

The sapphire layer L2 contains crystalline α-alumina (α-Al ₂ O ₃ ). The crystalline α-alumina may be a single crystal of α-alumina (ie, sapphire). The sapphire layer L2 may be composed of only crystalline α-alumina. The sapphire layer L2 may contain elements (impurities and the like) other than aluminum and oxygen as long as the crystallinity of α-alumina is not impaired. For example, in the sapphire layer L2, the boundary region along the boundary between the aluminum nitride layer L1 and the sapphire layer L2 may contain a trace amount of the additive element M. That is, the region of the sapphire layer L2 facing the aluminum nitride layer L1 may contain a trace amount of the additive element M.

The crystal structure of α-alumina contained in the sapphire layer L2 is a corundum type structure. The corundum-type structure is more accurately a rhombohedral crystal, but the corundum-type structure may be approximated by a hexagonal crystal. The corundum-type structure of α-alumina is shown in FIG. The hexagonal figure shown in FIG. 4 shows the arrangement of aluminum atoms and oxygen atoms in a corundum-shaped structure (regular hexagonal prism) seen from the c-axis direction. The unit cell of the corundum type structure is shown in FIG. Atoms in FIG. 5 are omitted for the purpose of notation of the basic vector, crystal orientation and crystal plane, but oxygen is arranged at each of the 12 vertices of the corundum-type unit cell uc2 (regular hexagonal prism). Will be done. _{Reference numeral a 1} , a _2, a ₃ and c in FIG. 5 are basic vectors (crystal axes) constituting the unit cell uc2 having a corundum-type structure. orientation of a ₁ is [1000]. orientation of a ₂ is [0100]. orientation of a ₃ is a [0010]. The orientation of c is [0001]. The lengths of a ₁ , a ₂ and a ₃ are approximately equal to each other. All of a ₁ , a ₂ and a ₃ are substantially perpendicular to c. The _{angle formed by a 1} , a ₂ and a ₃ with each other is approximately 120 degrees. The (1-100) plane of α-alumina is approximately perpendicular to the (11-20) plane of α-alumina. The (0001) plane of α-alumina is substantially perpendicular to the (11-20) plane of α-alumina. The (1-100) plane of α-alumina is approximately perpendicular to the (0001) plane of α-alumina. The (11-20) plane of α-alumina may be paraphrased as the a-plane of α-alumina. The (1-100) plane of α-alumina may be paraphrased as the m-plane of α-alumina. The (0001) plane of α-alumina may be paraphrased as the c plane of α-alumina.

In the following, the aluminum nitride layer L1 and aluminum nitride may be used as synonyms. In the following, the sapphire layer L2 and α-alumina may be used as synonyms.

The (0001) plane of aluminum nitride in the aluminum nitride layer L1 _{is substantially parallel to the surface SL2} of the sapphire layer L2, and the (11-20) plane of α-alumina in the sapphire layer L2 is also the surface of the sapphire layer L2. it is substantially parallel to the S _L2. (0001) plane of the aluminum nitride in the aluminum nitride layer L1 may be substantially parallel to the surface _{S L1} of the aluminum nitride layer L1, also (11-20) plane of α- alumina in the sapphire layer L2, aluminum nitride substantially it may be parallel to the surface _{S L1} of the layer L1. In other words, the plane orientation of the surface _{S L1} of the aluminum nitride layer L1 is [0001] plane orientation of the surface _{S L2} of the sapphire layer L2 is [11-20], the aluminum nitride in the aluminum nitride layer L1 (0001 The plane) is substantially parallel to the (11-20) plane of α-alumina in the sapphire layer L2. The (11-20) plane of aluminum nitride in the aluminum nitride layer L1 is substantially parallel to the (1-100) plane of α-alumina in the sapphire layer L2. (11-20) plane of aluminum nitride in the aluminum nitride layer L1 is substantially perpendicular to the surface _{S L2} of the surface _{S L1,} and sapphire layer L2 of the aluminum nitride layer L1. (1-100) plane of α- alumina in the sapphire layer L2 is also substantially perpendicular to the surface _{S L2} of the surface _{S L1,} and sapphire layer L2 of the aluminum nitride layer L1.

The relative relationship between the orientations of the crystal planes of aluminum nitride and α-alumina described above is shown in FIG. For convenience of illustration, in FIG. 6 (and FIG. 7 described later), the (0001) plane of aluminum nitride (uc1) does not overlap the (11-20) plane of α-alumina (uc2), but in reality, The (0001) plane of aluminum nitride overlaps the (11-20) plane of α-alumina. The (0001) plane of aluminum nitride is parallel to the (11-20) plane of α-alumina so that the (11-20) plane of aluminum nitride is substantially parallel to the (1-100) plane of α-alumina. when formed, the aluminum nitride layer L1 to be grown on the surface S _L2 of the sapphire layer L2 is likely take over the high crystallinity sapphire layer L2. As a result, the substrate 10 according to the present embodiment can have the aluminum nitride layer L1 having excellent crystallinity.

As shown in FIG. 7, the (0001) plane of aluminum nitride is (11-) of α-alumina so that the (1-100) plane of aluminum nitride is substantially parallel to the (1-100) plane of α-alumina. when formed parallel to 20) surface, an aluminum nitride layer L1 grown on the surface S _L2 of the sapphire layer L2 is hardly takes over the high crystallinity sapphire layer L2. Therefore, a surface orientation of the surface _{S L1} of the aluminum nitride layer L1 is [0001], a surface orientation of the surface _{S L2} of the sapphire layer L2 is [11-20], the aluminum layer L1 nitride (1-100) plane Is substantially parallel to the (1-100) plane of the sapphire layer L2, it is difficult for the substrate 10 to have the aluminum nitride layer L1 having excellent crystallinity.

Crystalline aluminum nitride layer L1 may be evaluated based on the rocking curve of (1-100) plane of the aluminum nitride measured in-plane direction of the surface S _L1 of the aluminum nitride layer L1. The smaller the full width at half maximum of the locking curve of the (1-100) plane, the higher the degree of orientation of the (1-100) plane of the aluminum nitride layer L1, and the better the crystallinity of the aluminum nitride layer L1. Rocking curve is measured by φ scan of the surface S _L1 of the aluminum nitride layer L1.

An outline of the φ scan is shown in FIG. The φ scan is a type of In Plane measurement. For convenience of explanation, the substrate 10 is a disc (wafer), the shape of the surface S _L1 of the aluminum nitride layer L1 is circular. The φ scan, the substrate 10 is rotated relative to the center of the surface S _L1 of the aluminum nitride layer L1. That is, the center of the surface S _L1 of the aluminum nitride layer L1 is the rotation center of the substrate 10, phi is the angle of rotation of the substrate 10. The unit of φ is seconds (arcsecоnd). The φ scan, the incident X-rays are irradiated from the X-ray source XR to the center of the surface S _L1 of the aluminum nitride layer L1. The direction d1 is the direction of the incident X-ray. incident X-rays used in the φ scan is substantially parallel to the surface S _L1 of the aluminum nitride layer L1. The incident X-rays are diffracted on the (1-100) plane of the aluminum nitride and detected by the detector D as diffracted X-rays. diffracted X-rays measured by φ scan is substantially parallel to the surface S _L1 of the aluminum nitride layer L1. Reference points, when the incident X-ray on the surface S _L1 of the aluminum nitride layer L1 is defined as a position to be irradiated (i.e. the center of the surface S _L1), direction d2 is the direction from the reference point to the detector D .. That is, the direction d2 is the direction of the detector D with respect to the position where the incident X-ray is irradiated. 2θ ₂ is the diffraction angle of the diffracted X-rays derived from the (1-100) plane of aluminum nitride. In φ scan, the angle between the direction d1 and the direction d2 is _{fixed at the diffraction angle 2θ 2,} and the intensity of the diffracted X-rays derived from the (1-100) plane of aluminum nitride is continuously increased with the change of φ. It is a method of measuring. The locking curve of the (1-100) plane of aluminum nitride can be rephrased as the twist distribution of the intensity of the diffracted X-rays derived from the (1-100) plane of aluminum nitride. The unit of the intensity of the diffracted X-ray may be, for example, cps (cоunts per secоnd).

RC1 (1-100) and RC2 (1-100) shown in Figure 9, the aluminum nitride measured in-plane direction of the surface _{S L1} of the aluminum nitride layer L1 (1-100) plane of the rocking curve of the specific This is an example. The horizontal axis of each locking curve is Δφ. The vertical axis of each locking curve is the intensity of diffracted X-rays. The origin on the horizontal axis of each locking curve corresponds to φ, which has the maximum intensity of diffracted X-rays derived from the (1-100) plane of aluminum nitride. When φ ₀ is defined as φ, which has the maximum intensity of diffracted X-rays derived from the (1-100) plane of aluminum nitride, the locking curve of the (1-100) plane of aluminum nitride has φ (φ). ₀ -Derutafai) is higher (phi ₀ + [Delta] [phi) less is in the range (1-100) of the intensity of the diffracted X-ray of the plane distribution. The incident X-ray may be a characteristic X-ray (CuKα ray) of copper (Cu). _{The diffraction angle 2θ 2} of the diffracted X-rays derived from the (1-100) plane of aluminum nitride may be 33.22 degrees (degries).

Measured in-plane direction of the surface _{S L1} of the aluminum nitride layer L1 of aluminum nitride (1-100) plane full width at half maximum of the rocking curve, 0 seconds 500 seconds or less, preferably a below 300 seconds 50 seconds You can. The locking curve of the (1-100) plane shows the average crystallinity of the entire aluminum nitride layer L1. Due to the lattice mismatch between the aluminum nitride layer L1 and the sapphire layer L2, the crystallinity of the aluminum nitride located near the boundary between the aluminum nitride layer L1 and the sapphire layer L2 is not good. However, in the present embodiment, for the reasons described above, the aluminum nitride layer L1 to be grown on the surface S _L2 of the sapphire layer L2 is likely take over the high crystallinity sapphire layer L2. Thus, with increasing distance of the aluminum nitride from the surface S _L2 of the sapphire layer L2, it increases the crystallinity of the aluminum nitride. As a result, the full width at half maximum of the locking curve of the (1-100) plane of the aluminum nitride layer L1 after growth becomes smaller than the full width at half maximum of the locking curve of the (1-100) plane of the aluminum nitride layer L1 at the initial stage of growth. easy. In other words, as the thickness T of the aluminum nitride layer L1 increases (growth of the aluminum nitride layer L1), the full width at half maximum of the locking curve of the (1-100) plane of the aluminum nitride layer L1 tends to decrease. When the half-value total width of the locking curve of the (1-100) plane is 500 seconds or less, the aluminum nitride layer L1 has sufficiently high crystallinity, and therefore the nitride semiconductor layer (light emitting layer) formed on the aluminum nitride layer L1. Etc.), the crystallinity tends to increase. As a result, the luminous efficiency of the light emitting element formed from the substrate 10 tends to increase. Theoretically, the most preferable full width at half maximum of the locking curve is zero, but the full width at half maximum that can be easily achieved in this embodiment is about 50 seconds. Measured in-plane direction of the surface _{S L1} of the aluminum nitride layer L1 of aluminum nitride (1-100) plane full width at half maximum of the rocking curve, 100 seconds or more 470 or less, than 170 seconds 470 seconds, or 100 seconds or more It may be 280 seconds or less.

When the aluminum nitride layer is formed by directly reducing and nitriding the surface of the sapphire substrate, the full width at half maximum of the locking curve of the (1-100) plane of aluminum nitride in the in-plane direction tends to be larger than 500 seconds. Even when the aluminum nitride layer directly overlapping the sapphire substrate and the aluminum nitride layer directly overlapping the aluminum oxynitride layer are formed by directly reducing and nitriding the surface of the sapphire substrate, the aluminum nitride (1-) in the in-plane direction is formed. 100) The half-value full width of the surface locking curve tends to be larger than 500 seconds.

When the aluminum nitride layer is formed by directly reducing and nitriding the surface of the sapphire substrate, the full width at half maximum of the locking curve of the (1-100) plane of aluminum nitride in the in-plane direction is the thickness of the aluminum nitride layer (buffer layer). It does not necessarily decrease sufficiently as the sapphire increases. When the aluminum nitride layer is formed by directly reducing and nitriding the surface of the sapphire substrate, the full width at half maximum of the locking curve of the (1-100) plane of aluminum nitride in the in-plane direction is the thickness of the aluminum nitride layer (buffer layer). It may increase as the sapphire increases.

RC1 (1-100) in FIG. 9 may be a rocking curve of (1-100) plane of the aluminum nitride measured in-plane direction of the surface _{S L1} of the aluminum nitride layer L1. RC2 (1-100) in Figure 9, the distance from the surface _{S L2} of the sapphire layer L2 of the aluminum nitride layer L1 is aluminum nitride contained in the region is 100nm or less (1-100) in plane rocking curve It may be there. RC2 (1-100) is measured in a plane substantially parallel in the direction to the surface _{S L2} of the sapphire layer L2. It focused ion beam; by cutting (Focused Ion Beam FIB) by the surface _{S L1} of the aluminum nitride layer L1, after adjusting the thickness T of the aluminum nitride layer L1 to 100nm or less, the same φ scan and RC1 (1-100) RC2 (1-100) may be measured by. RC2 (1-100) may be measured when the thickness T of the aluminum nitride layer L1 is 100 nm or less in the process of forming the aluminum nitride layer L1, and RC1 (1-100) is measured when the growth of the aluminum nitride layer L1 is completed. 100) may be measured. As described above, as the thickness T of the aluminum nitride layer L1 increases (growth of the aluminum nitride layer L1), the full width at half maximum of the locking curve of the (1-100) plane of the aluminum nitride layer L1 tends to decrease. Therefore, the full width at half maximum of RC1 (1-100) is smaller than the full width at half maximum of RC2 (1-100).

As shown in FIG. 7, the (0001) plane of aluminum nitride is α-alumina (11-) so that the (1-100) plane of aluminum nitride is substantially parallel to the (1-100) plane of α-alumina. 20) When formed parallel to the plane, the half-price full width of RC1 (1-100) is larger than the half-price full width of RC2 (1-100).

The thickness T of the aluminum nitride layer L1 may be 50 nm or more and 1000 nm or less, preferably 50 nm or more and 500 nm or less. When the thickness T of the aluminum nitride layer L1 is 50 nm or more, the aluminum nitride layer L1 is sufficiently thick, and the influence of the stress applied to the aluminum nitride layer L1 from the sapphire layer L2 is likely to be reduced. As a result, the full width at half maximum of the rocking curve of (1-100) plane of the aluminum nitride measured in-plane direction of the surface S _L1 of the aluminum nitride layer L1, prone to 500 seconds or more 00 seconds. When the thickness T of the aluminum nitride layer L1 is 500 nm or more, the time required for forming the aluminum nitride layer L1 is long, and the productivity of the substrate 10 is lowered. When the thickness T of the aluminum nitride layer L1 is 1000 nm or more, the ratio of the decrease in the full width at half maximum of the locking curve to the increase in the thickness T of the aluminum nitride layer L1 becomes small. That is, when the thickness T of the aluminum nitride layer L1 is 1000 nm or more, the cost-effectiveness of thickening the aluminum nitride layer L1 is small. The thickness T of the aluminum nitride layer L1 is not limited to the above range. For example, the thickness T of the aluminum nitride layer L1 may be 50 nm or more and 5 μm or less. The thickness of the aluminum nitride layer L1 may be measured by an ellipsometer.

The thickness of the sapphire layer L2 may be, for example, 50 μm or more and 3000 μm or less. The thickness of the entire substrate 10 is the sum of the thickness of the sapphire layer L2 and the thickness T of the aluminum nitride layer L1.

The additive element M contained in the aluminum nitride layer L1 is at least one selected from the group consisting of rare earth elements, alkaline earth elements and alkali metal elements. That is, the additive element M is scandium (Sc), ytterbium (Y), lanthanum (La), cerium (Ce), placeodim (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), and europium (Eu). ), Gadolium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Elbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu), Calcium (Ca), Strontium (Sr) ), Barium (Ba), Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Thulium (Cs) and Radium (Ra).

When the aluminum nitride layer L1 contains the additive element M, the (11-20) plane of the aluminum nitride layer L1 tends to be substantially parallel to the (1-100) plane of the sapphire layer L2, and the aluminum nitride layer L1 has high crystallinity. Easy to hold. In the case of aluminum nitride layer L1 contains an additive element M, in the process of forming an aluminum nitride layer L1, liable thickness T of the aluminum nitride layer L1 is increased, prone surface S _L1 of the aluminum nitride layer L1 becomes smooth. Due to the smoothness of the high crystallinity and surface of the aluminum nitride layer L1 including the additional element M, liable crystal defects is suppressed in the semiconductor layer formed on the surface S _L1 of the aluminum nitride layer L1, increased crystallinity of the semiconductor layer , The smooth surface of the semiconductor layer is easily formed.

The additive element M may be present near the boundary between the aluminum nitride layer L1 and the sapphire layer L2. For example, in the aluminum nitride layer L1, the boundary region along the boundary between the aluminum nitride layer L1 and the sapphire layer L2 may contain the above-mentioned additive element M. When the boundary region contains the additive element M, stress is likely to be concentrated in the boundary region, and the warp of the entire aluminum nitride layer L1 is likely to be suppressed. The substrate 10 provided with the aluminum nitride layer L1 in which the warp is suppressed is suitable for manufacturing a light emitting element. When the boundary region contains an additive element M having an ionic radius larger than that of Al, O and N, stress tends to concentrate in the boundary region. At least a part of the additive element M contained in the boundary region may be at least one of Eu and Ca. When the boundary region contains at least one of Eu and Ca, the above-mentioned effect due to the boundary region can be easily obtained. The total content of the additive element M in the boundary region may be 0.1 mass ppm or more and 200 mass ppm or less, or 10 mass ppm or more and 200 mass ppm or less. The maximum value of the total content of the additive element M in the boundary region may be 0.1 mass ppm or more and 200 mass ppm or less, or 10 mass ppm or more and 200 mass ppm or less. When the total content of the additive element M in the boundary region is 0.1 mass ppm or more (preferably 10 mass ppm or more), the aluminum nitride layer L1 tends to have high crystallinity and a sufficient thickness T. When the total content of the additive element M in the boundary region is 200 mass ppm or less, it is difficult for a composition other than aluminum nitride and α-alumina (for example, a compound derived from the additive element M) to be formed in the substrate 10. The aluminum nitride layer L1 tends to have high crystallinity. The total content of the additive element M in the portion of the aluminum nitride layer L1 excluding the boundary region may be smaller than the total content of the additive element M in the boundary region. The portion of the aluminum nitride layer L1 excluding the boundary region does not have to contain the additive element M. The total content of additive element M in the aluminum nitride layer L1 may be reduced along a direction from the surface S _L1 of the aluminum nitride layer L1 on the surface S _L2 of the sapphire layer L2.

The above boundary region, the distance from the surface _{S L2} of the sapphire layer L2 of the aluminum nitride layer L1 is 1000nm or less, 500 nm or less, 200 nm or less, 100 nm or less, or a region is 50nm or less. The boundary region may contain at least one element selected from Al, O, N, and the additive element M. The boundary region may be composed of only Al, N and the additive element M. The boundary region may be composed of only Al, N, O and the additive element M. The boundary region may be composed of only Al, N and O. The content of N in the boundary region may be reduced along a direction from the surface S _L1 of the aluminum nitride layer L1 on the surface S _L2 of the sapphire layer L2. On the other hand, the content of O in the border area may be increased along the direction from the surface S _L1 of the aluminum nitride layer L1 on the surface S _L2 of the sapphire layer L2.

The aluminum nitride layer L1 may contain a trace amount of aluminum nitride as long as the crystallinity of the aluminum nitride layer L1 is not impaired. For example, the boundary region of the aluminum nitride layer L1 may contain a trace amount of aluminum nitride. However, aluminum nitride tends to impair the crystallinity of the aluminum nitride layer L1. Further, aluminum nitride contributes to the reflection of light and tends to impair the light emitting ability of the light emitting element provided with the substrate 10. Therefore, it is preferable that the aluminum nitride layer L1 does not contain aluminum nitride. The specific composition of aluminum nitride is not limited, but for example, aluminum nitride may be represented by the following chemical formula 1. Vp in the following chemical formula 1 is a cation pore, and x in the following chemical formula 1 is larger than 2 and less than 6.
Al _{(64 + x) / 3} Vp _{(8-x) / 3} O _32-x N _x (1)

Crystalline aluminum nitride layer L1 may be evaluated on the basis of the rocking curve of the (0001) plane of the aluminum nitride measured in Out-оf-Plane direction of the surface _{S L1} of the aluminum nitride layer L1. The smaller the full width at half maximum of the locking curve of the (0001) plane, the higher the degree of orientation of the (0001) plane of the aluminum nitride layer L1 in the Out-оf-Plane direction, and the better the crystallinity of the aluminum nitride layer L1. Rocking curve (0001) plane of the aluminum nitride is measured by ω scan of the surface _{S L1} of the aluminum nitride layer L1.

RC1 (0001) is a locking curve of the (0001) plane of aluminum nitride measured in the Out-оf-Plane direction of the surface of the aluminum nitride layer L1, and RC2 (0001) is a sapphire layer of the aluminum nitride layer L1. It is a locking curve of the (0001) plane of aluminum nitride contained in the region where the distance from the surface of the aluminum nitride is 100 nm or less, and RC2 (0001) is measured in the Out-оf-Plane direction substantially perpendicular to the surface of the sapphire layer. , The half-price full width of RC1 (0001) may be smaller than the half-price full width of RC2 (0001). As the thickness T of the aluminum nitride layer L1 increases (growth of the aluminum nitride layer L1), the full width at half maximum of the locking curve of the (0001) plane of the aluminum nitride layer L1 in the Out-оf-Plane direction tends to decrease. The cutting of the surface _{S L1} of the aluminum nitride layer L1 by FIB, after adjusting the thickness T of the aluminum nitride layer L1 to 100nm or less, RC1 (0001) and may be measured RC2 (0001) by the same ω scan. RC2 (0001) may be measured when the thickness T of the aluminum nitride layer L1 is 100 nm or less in the process of forming the aluminum nitride layer L1, and RC1 (0001) is measured when the growth of the aluminum nitride layer L1 is completed. May be done.

(Substrate manufacturing method)
The method for manufacturing the substrate 10 includes at least a sputtering step and a reduction nitriding step following the sputtering step. The method for manufacturing the substrate 10 may further include a MOCVD step in addition to the sputtering step and the reduction nitriding step. The details of each process are as follows.

In the sputtering step, an aluminum nitride layer is formed on one surface of the sapphire substrate by sputtering. The sapphire substrate corresponds to the sapphire layer L2 constituting the substrate 10. The orientation of the surface of the sapphire substrate is [11-20]. That is, the surface of the sapphire substrate on which the aluminum nitride layer is formed is parallel to the (11-20) plane of α-alumina constituting the sapphire substrate. The dimensions and shape of the sapphire substrate are not particularly limited. The thickness of the sapphire substrate may be, for example, 50 μm or more and 3000 μm or less. The sapphire substrate may be a disk (wafer). The diameter of the wafer may be, for example, 50 mm or more and 300 mm or less. The aluminum nitride layer is a layer containing Al, O and N. The composition and structure of the aluminum nitride layer are not limited. The thickness of the aluminum nitride layer may be, for example, 50 nm or more and 1000 nm or less. The thickness of the aluminum nitride layer may be controlled by the duration of sputtering and the input power (power density) given to the target (elemental substance of Al) during sputtering. The aluminum nitride layer is a precursor of the aluminum nitride layer formed in the reduction nitriding step. The thickness of the aluminum nitride layer may be substantially the same as the thickness of the aluminum nitride layer formed in the reduction nitriding step. Therefore, the thickness of the aluminum nitride layer formed in the reduction nitriding step may be controlled based on the thickness of the aluminum nitride layer. The thickness of the aluminum nitride layer may be measured by an ellipsometer. Sputtering may be carried out in a mixed gas (raw material gas) of nitrogen (N ₂ ), oxygen (O _{2) and argon (Ar).} N and O constituting the aluminum nitride layer are derived from the raw material gas.

In the reduction nitriding step, the aluminum oxynitride layer is reduced and nitrided by heating the sapphire substrate on which the aluminum oxynitride layer is formed in nitrogen gas. By the reduction nitride of the aluminum nitride layer, oxygen in the aluminum nitride layer is replaced with nitrogen, and the aluminum nitride layer becomes the aluminum nitride layer L1a. By reducing and nitriding the aluminum nitride layer instead of the surface of the sapphire substrate, the (0001) plane of the aluminum nitride layer L1a becomes substantially parallel to the (11-20) plane of the sapphire layer L2, and the (11-20) plane of the aluminum nitride layer L1a ( The 11-20) plane is substantially parallel to the (1-100) plane of the sapphire layer L2. In the reduction nitriding step, the entire aluminum nitride layer may be the aluminum nitride layer L1a. That is, the aluminum nitride layer does not have to remain after the reduction nitriding step.

In the reduction nitriding step, the aluminum nitride layer is reduced and nitrided instead of the surface of the sapphire substrate. Therefore, in the reduction nitride process, not only the oxygen in the aluminum nitride layer is replaced by nitrogen, but also the aluminum nitride layer Al inside is also easy to move due to heat. The reason is that the Al in the aluminum nitride layer is not Al derived from the sapphire substrate, but Al deposited on the surface of the sapphire substrate by the sputtering process, and is not fixed in the strong crystal structure. .. Since the position of Al as well as nitrogen is likely to fluctuate in the process of reduction nitriding, the orientation of the crystal plane of the aluminum nitride layer L1a in the in-plane direction of the surface ((11-20) plane) of the sapphire substrate is likely to fluctuate. The crystal structure of the aluminum nitride layer L1a is likely to be stabilized in a low energy state. As a result, the (11-20) plane of the aluminum nitride layer L1a becomes substantially parallel to the (1-100) plane of the sapphire layer L2.

When the aluminum nitride layer is formed on the surface of the sapphire substrate by directly reducing and nitriding the surface ((11-20) surface) of the sapphire substrate, oxygen in the sapphire substrate is replaced by nitrogen, but the sapphire substrate is used. The constituent Al is difficult to move. As a result, in the process of reduction nitride, the orientation of the crystal plane of the aluminum nitride layer in the in-plane direction of the surface of the sapphire substrate is not easily changed, and it is easy to match the orientation of the crystal plane of the sapphire substrate. Therefore, when the surface of the sapphire substrate is directly reduced and nitrided, the (0001) plane of the aluminum nitride layer can be substantially parallel to the (11-20) plane of the sapphire layer, but the (1-100) plane of the aluminum nitride layer. The surface tends to be substantially parallel to the (1-100) surface of the sapphire layer. For the same reason, by directly reducing and nitriding the surface ((11-20) surface) of the sapphire substrate, an aluminum nitride layer overlapping the surface of the sapphire layer and an aluminum nitride layer overlapping the aluminum oxynitride layer are formed. Also in this case, the (0001) plane of the aluminum nitride layer can be substantially parallel to the (11-20) plane of the sapphire layer, but the (1-100) plane of the aluminum nitride layer is the (1-100) plane of the sapphire substrate. It tends to be almost parallel to.

The reason why the (11-20) plane of the aluminum nitride layer L1a is substantially parallel to the (1-100) plane of the sapphire layer L2 is not limited to the above mechanism in the reduction nitriding step.

Prior to the reduction nitriding step, the additive element M is preferably adhered to a part or the whole of the surface of the aluminum nitride layer. For example, a solution of an organometallic compound containing the additive element M may be applied to the surface of the aluminum nitride layer. Further, by heating the sapphire substrate coated with the solution in the air, only the organic component may be decomposed and burned. As a solution of the organometallic compound containing the additive element M, a solution of the organometallic compound used in the organometallic decomposition method (MOD) may be used.

In the reduction nitriding step, the additive element M promotes reduction nitriding of the aluminum oxynitride layer. That is, when the aluminum nitride layer to which the additive element M is attached is heated in nitrogen gas, the additive element M ^{extracts oxygen (O2-} ) from the surface of the aluminum nitride layer, and the oxygen defect is the aluminum nitride layer. Formed on the surface. Nitrogen is introduced into the oxygen defect and easily diffuses heat from the surface of the aluminum nitride layer to the inside of the aluminum nitride layer through the oxygen defect. In the reduction nitriding step, the additive element M may react with nitrogen gas to form a nitride of the additive element M. The nitride of M may react with oxygen in the aluminum nitride layer to form an oxide of the additive element M and AlN. Due to the action of the additive element M as described above, the (0001) plane of the aluminum nitride layer L1a tends to be substantially parallel to the (11-20) plane of the sapphire layer L2, and the (11-20) plane of the aluminum nitride layer L1a tends to be substantially parallel. The plane tends to be substantially parallel to the (1-100) plane of the sapphire layer L2, and the crystallinity of the aluminum nitride layer L1a tends to increase. The additive element M may remain in the aluminum nitride layer L1a. At least a part of the additive element M may be separated from the aluminum nitride layer L1a as an oxide of the additive element M.

At least a part of the additive element M adhering to the surface of the aluminum nitride layer is preferably at least one of europium and calcium. It is more preferable that at least a part of the additive element M adhering to the surface of the aluminum nitride layer is europium. Europium or calcium is an element with a relatively low electronegativity. ^{Therefore, europium or calcium tends to extract oxygen (O2-} ) from the surface of the aluminum nitride layer, and oxygen defects are likely to be formed on the surface of the aluminum nitride layer. As a result, nitrogen easily diffuses into the aluminum nitride layer through oxygen defects. Europium or calcium is an element having a relatively low melting point among the additive elements M. Therefore, europium or calcium tends to diffuse to the entire surface of the aluminum nitride layer as a semi-liquid phase even at a low temperature. As a result, the (0001) plane of the aluminum nitride layer L1a tends to be substantially parallel to the (11-20) plane of the sapphire layer L2, and the (11-20) plane of the aluminum nitride layer L1a is the (1-20) plane of the sapphire layer L2. -100) The aluminum nitride layer L1a tends to be substantially parallel to the plane, and the crystallinity of the aluminum nitride layer L1a tends to increase.

When the temperature of the sapphire substrate in the reduction nitriding step becomes 1630 ° C. or higher, aluminum nitride, which is one of the causes of light reflection, is likely to be formed in the sapphire substrate. In particular, when the temperature of the sapphire substrate is 1700 ° C. or higher, aluminum nitride is likely to be formed in the sapphire substrate. However, when the aluminum nitride layer to which the additive element M is attached is heated in nitrogen gas at a temperature of 1680 ° C. or lower, the aluminum nitride layer is sufficiently suppressed while the formation of aluminum nitride in the sapphire substrate is sufficiently suppressed. Can be reduced and nitrided.

As described above, europium and calcium are likely to be sufficiently diffused over the entire surface of the aluminum nitride layer even at a relatively low temperature, and oxygen is easily extracted from the surface of the aluminum nitride layer. Therefore, even if the temperature of the sapphire substrate heated in nitrogen gas is low at which aluminum nitride is difficult to form, high crystals can be obtained by reducing nitriding of the aluminum nitride layer by using at least one of europium and calcium. It is easy to form the aluminum nitride layer L1a having a property. The low temperature at which aluminum nitride is difficult to form is, for example, less than 1630 ° C or 1600 ° C or lower. However, by using the additive element M, it is possible to form the aluminum nitride layer L1a having high crystallinity at a temperature of less than 1630 ° C. while suppressing the formation of aluminum nitride in the sapphire substrate.

When the additive element M having a melting point higher than that of europium and calcium is used, the sapphire substrate must be heated at a higher temperature than when europium or calcium is used in order to diffuse the additive element M over the entire surface of the aluminum nitride layer. It doesn't become. However, the higher the temperature of the sapphire substrate, the easier it is for aluminum nitride, which contributes to the reflection of light, to be formed in the sapphire substrate.

The temperature of the sapphire substrate heated in nitrogen gas (reduction nitriding temperature) may be 1550 ° C. or higher and 1700 ° C. or lower, 1600 ° C. or higher and 1680 ° C. or lower, or 1600 ° C. or higher and lower than 1630 ° C. In order to thermally diffuse the nitrogen gas into the aluminum nitride layer, the reduction nitriding temperature is preferably at least 1550 ° C. or higher. When the reduction nitriding temperature is 1700 ° C. or lower, more preferably less than 1630 ° C., the formation of aluminum nitride in the sapphire substrate can be suppressed. When the additive element M is not used, aluminum nitride is likely to be formed in the sapphire substrate at a reduction nitriding temperature of 1630 ° C. or higher. On the other hand, when the additive element M is used, the aluminum nitride layer can be reduced-nitrided at a reduction nitriding temperature of less than 1630 ° C or 1600 ° C or less while suppressing the formation of aluminum nitride in the sapphire substrate. When the reduction nitriding temperature is 1600 ° C. or higher and lower than 1630 ° C., the (0001) plane of the aluminum nitride layer L1a tends to be substantially parallel to the (11-20) plane of the sapphire layer L2, and the (11-) surface of the aluminum nitride layer L1a tends to be substantially parallel. 20) The plane tends to be substantially parallel to the (1-100) plane of the sapphire layer L2, and the crystallinity of the aluminum nitride layer L1a tends to increase.

The duration of reduction nitriding, the amount of additive element M used, and the partial pressure or supply of nitrogen gas may be controlled according to the thickness of the aluminum nitride layer. The longer the duration of reduction nitriding, the more the reduction nitriding of the aluminum oxynitride layer is promoted. The greater the amount of the additive element M adhering to the surface of the aluminum oxynitride layer, the more the reduction nitriding of the aluminum oxynitride layer is promoted. The larger the partial pressure or supply of nitrogen gas, the more the reduction nitriding of the aluminum nitride layer is promoted.

The reduction nitriding step may be carried out at least twice. For example, when the additive element M is used, the sapphire substrate may be heated at the above reduction nitriding temperature for a short time, and then the sapphire substrate may be heated at the above reduction nitriding temperature for a longer period of time. By the first heating, the additive element M tends to diffuse uniformly over the entire surface of the aluminum nitride layer. By the subsequent heating for a long time for a second time, nitrogen is easily diffused from the surface of the aluminum nitride layer to the inside without unevenness. The duration of the first reduction nitriding step may be 1 hour or more and 8 hours or less. The duration of the second reduction nitriding step may be 1 hour or more and 108 hours or less.

The reduction nitriding of the aluminum nitride layer in nitrogen gas may be carried out in the presence of carbon powder. Oxygen extracted from the aluminum nitride layer by the additive element M reacts with carbon in the atmosphere to generate carbon monoxide.

By the above method, direct overlap aluminum nitride layer L1a on the surface S _L2 of the sapphire layer L2 is formed. The substrate 10 may be completed by the above method. For convenience of explanation, the aluminum nitride layer L1a formed in the reduction nitriding step is referred to as a base aluminum nitride layer L1a. The base aluminum nitride layer L1a corresponds to the boundary region described above.

The base aluminum nitride layer L1a may be further grown by the MOCVD step following the reduction nitriding step. For convenience of explanation, the aluminum nitride layer that grows on the surface of the underlying aluminum nitride layer L1a is referred to as a buffer layer L1b. That is, the aluminum nitride layer L1 is an aluminum base nitride layer L1a overlapping directly on the surface S _L2 of the sapphire layer L2, may consist a buffer layer L1b overlapping directly to the aluminum base nitride layer L1a. Material of the buffer layer L1b used in MOCVD process may be, for example, trimethyl aluminum _{(C 6 H} 18 Al ₂₎ and ammonia (NH _3).

The crystal orientation of the buffer layer L1b coincides with the crystal orientation of the underlying aluminum nitride layer L1a. In other words, (0001) plane of the aluminum nitride in the buffer layer L1b is substantially parallel to the surface _{S L2} of the sapphire layer L2, the aluminum nitride in the buffer layer L1b (11-20) plane, in the sapphire layer L2 It is substantially parallel to the (1-100) plane of α-alumina. The buffer layer L1b can inherit the high crystallinity of the base aluminum nitride layer L1a and can have higher crystallinity than the base aluminum nitride layer L1a. For example, the full width at half maximum of the locking curve of the (1-100) plane of aluminum nitride measured in the in-plane direction of the surface of the buffer layer L1b is that of the aluminum nitride measured in the in-plane direction of the surface of the underlying aluminum nitride layer L1a. It is smaller than the full width at half maximum of the locking curve of the (1-100) plane. As the thickness of the buffer layer L1b increases, the full width at half maximum of the locking curve of the (1-100) plane of aluminum nitride measured in the in-plane direction of the surface of the buffer layer L1b tends to decrease.

Since the buffer layer L1b has sufficiently high crystallinity, the crystallinity of the nitride semiconductor layer (light emitting layer or the like) formed on the buffer layer L1b is also improved. As a result, the luminous efficiency of the light emitting element formed from the substrate 10 is increased. Therefore, the MOCVD step may be carried out in the manufacturing process of the light emitting device described later.

Temporarily, the (0001) surface of aluminum nitride in the underlying aluminum nitride layer L1a _{is substantially parallel to the surface SL2} of the sapphire layer L2, and the (11-20) surface of α-alumina in the sapphire layer L2 is the sapphire layer. When it is substantially parallel to the surface SL2 of _L2 and the (1-100) plane of aluminum nitride in the underlying aluminum nitride layer L1a is substantially parallel to the (1-100) plane of α-alumina in the sapphire layer L2. The (1-100) plane of aluminum nitride in the buffer layer L1b is also substantially parallel to the (1-100) plane of α-alumina in the sapphire layer L2, and the buffer layer L1b is crystalline of the underlying aluminum nitride layer L1a. The crystallinity of the buffer layer L1b is inferior to that of the underlying aluminum nitride layer L1a.

RC1 (1-100) may be the locking curve of the (1-100) plane of the buffer layer L1b measured in the in-plane direction of the surface of the buffer layer L1b, and RC2 (1-100) is the underlying aluminum nitride. It may be the locking curve of the (1-100) surface of the underlying aluminum nitride layer L1a measured in the in-plane direction of the surface of the layer L1a, and the full width at half maximum of RC1 (1-100) is that of RC2 (1-100). It may be smaller than the full width at half maximum.

RC1 (0001) may be the locking curve of the (0001) plane of the buffer layer L1b measured in the Out-оf-Plane direction of the surface of the buffer layer L1b, and RC2 (0001) may be the locking curve of the base aluminum nitride layer L1a. It may be the locking curve of the (0001) plane of the base aluminum nitride layer L1a measured in the Out-оf-Plane direction of the surface, and the full width at half maximum of RC1 (0001) is smaller than the full width at half maximum of RC2 (0001). good.

(Light emitting element)
The substrate 10 according to this embodiment may be used as a light emitting element. That is, the light emitting element according to the present embodiment includes the above-mentioned substrate 10. Since the light emitting element includes the substrate 10, the light emitting element can have high luminous efficiency. For example, the light emitting element according to this embodiment may be a light emitting diode. The light emitting diode may be, for example, a deep ultraviolet light emitting diode such as a UVC LED or a DUV LED. In the following, the light emitting diode 100 shown in FIG. 10 will be described as an example of the light emitting element including the substrate 10. However, the structure of the light emitting diode according to the present embodiment is not limited to the laminated structure shown in FIG.

The light emitting diode 100 according to the present embodiment includes a substrate 10, an n-type semiconductor layer 40 that overlaps the aluminum nitride layer L1 (buffer layer L1b), a light emitting layer 42 that overlaps the n-type semiconductor layer 40, and p that overlaps the light emitting layer 42. It includes a type semiconductor layer 44, a first electrode 48 installed on the surface of the n-type semiconductor layer 40, and a second electrode 46 installed on the surface of the p-type semiconductor layer 44. A barrier layer (electron block layer) may be interposed between the light emitting layer 42 and the p-type semiconductor layer 44.

By arranging the aluminum nitride layer L1 (buffer layer L1b) between the sapphire layer L2 and the n-type semiconductor layer 40, the lattice mismatch between the sapphire layer L2 and the n-type semiconductor layer 40 is suppressed, and the substrate Crystal defects of each semiconductor layer laminated on 10 are easily suppressed. Another buffer layer may be interposed between the aluminum nitride layer L1 (buffer layer L1b) and the n-type semiconductor layer 40. Another buffer layer may consist of, for example, a single crystal of a nitride of a Group 13 element. For example, another buffer layer may be a single crystal of at least any nitride of Al and Ga.

The n-type semiconductor layer 40 may include, for example, n-type gallium nitride (n-GaN) or n-type aluminum gallium nitride (n-AlGaN). The n-type semiconductor layer 40 may further contain silicon (Si). The n-type semiconductor layer 40 may be composed of a plurality of layers. The light emitting layer 42 may include, for example, gallium nitride (GaN), aluminum gallium nitride (AlGaN), or indium gallium nitride (InGaN). The light emitting layer 42 may be composed of a plurality of layers. The p-type semiconductor layer 44 may include, for example, p-type gallium nitride (p-GaN) or p-type aluminum gallium nitride (p-AlGaN). The p-type semiconductor layer 44 may further contain magnesium (Mg). The p-type semiconductor layer 44 may be composed of a plurality of layers. For example, the p-type semiconductor layer 44 may have a p-type clad layer that overlaps the light emitting layer 42 and a p-type contact layer that overlaps the p-type clad layer. The first electrode 48 installed on the n-type semiconductor layer 40 may contain, for example, indium (In). The second electrode 46 installed on the p-type semiconductor layer 44 may contain, for example, at least one of nickel (Ni) and gold (Au).

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

For example, the application of the substrate 10 according to this embodiment is not limited to the light emitting diode. The substrate 10 according to the present embodiment may be a substrate provided in a semiconductor laser oscillator such as an ultraviolet laser. That is, the light emitting element according to this embodiment may be a semiconductor laser oscillator. The substrate 10 according to this embodiment may be used as a power transistor. The substrate 10 according to this embodiment may be used as a substrate for various semiconductor elements. By using the substrate 10 as the substrate of the semiconductor element, the power loss of the semiconductor element is reduced. The substrate 10 may be used for a piezoelectric element (for example, a piezoelectric thin film element). By using the substrate 10 for the piezoelectric element, the piezoelectric characteristics of the piezoelectric element are improved.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples.

(Example 1)
<Manufacturing of substrate>
In the sputtering process, an aluminum nitride layer was formed on one surface of the sapphire substrate by DC magnetron sputtering. The sapphire substrate is a substrate made of a single crystal of α-alumina. The orientation of the surface of the sapphire substrate was [11-20]. That is, the surface of the sapphire substrate on which the aluminum nitride layer was formed was parallel to the (11-20) plane of α-alumina. The sapphire substrate was a disk (wafer). The diameter of the sapphire substrate was 2 inches. The thickness of the sapphire substrate was 430 μm. The thickness of the sapphire substrate was uniform. The thickness T0 of the aluminum nitride layer was adjusted to the values shown in Table 1 below. The thickness T0 of the aluminum nitride layer was uniform. The duration of sputtering was 10 minutes. A metal Al (a simple substance of Al) was used as the target for sputtering. The input power (power density) given to the target was 700 W. The temperature of the sapphire substrate during sputtering was room temperature. Sputtering was performed in a mixed gas of nitrogen, oxygen and argon.

By spin coating, the MOD solution was applied to the entire surface of the aluminum nitride layer. The MOD solution contained a Ca compound (organic compound). Ca is an additive element M. The concentration [Ca] of the compound of Ca in the MOD solution was adjusted to the value shown in Table 1 below. Spin coating was performed at 2000 rpm for 20 seconds. After applying the MOD solution, the sapphire substrate was dried on a hot plate at 150 ° C. for 10 minutes. After drying the sapphire substrate, the sapphire substrate was heated in air at 600 ° C. for 2 hours. The above-mentioned process using the MOD process is referred to as a MOD process.

The sapphire substrate after the MOD process was placed on the alumina plate, and 5 mg of carbon powder (20 mg of carbon in total) was placed in each of the four locations around the substrate. The surface to which the MOD solution was applied (the surface of the aluminum nitride layer) was exposed without being in contact with the alumina plate. The dimensions of the alumina plate were 100 mm in length × 100 mm in width. Subsequently, after covering the entire sapphire substrate with an alumina saggar, the sapphire substrate was installed on a sample setting table in the nitriding furnace. The dimensions of the alumina saggar were 75 mm in length × 75 mm in width × 70 mm in height. As the nitriding furnace, a resistance heating type electric furnace using carbon as a heater was used. Before heating the sapphire substrate in the nitriding furnace, the inside of the furnace was degassed to 0.03 Pa using a rotary pump and a diffusion pump. Then, nitrogen gas was flowed into the furnace until the pressure in the furnace reached 100 kPa (atmospheric pressure), and then the supply of nitrogen gas was stopped. After supplying the nitrogen gas into the furnace, in the reduction nitriding step, the sapphire substrate in the furnace was heated at 1600 ° C. for 20 hours. The time during which the sapphire substrate is heated at 1600 ° C. in the reduction nitriding step is referred to as "reduction nitriding time". The elevating temperature rate in the furnace in the reduction nitriding step was adjusted to 600 ° C./hour. After the lapse of the reduction nitriding time, the sapphire substrate was cooled to room temperature, and then the sapphire substrate was taken out of the furnace.

The substrate of Example 1 was produced by the above procedure. A plurality of the same substrates were made as the substrates of Example 1 for the analysis and measurement described below.

<Analysis 1>
In the following X-ray diffraction (XRD) method, Cu characteristic X-rays (CuKα rays) were used as incident X-rays. The surface of the substrate described below corresponds to the surface coated with the MOD solution in the MOD process.

The XRD pattern on the surface of the substrate was measured in the Out-оf-Plane direction of the substrate. The XRD pattern of Example 1 had a peak of diffraction lines derived from the (0002) plane of AlN. The polar map of the (1102) plane of AlN was measured by the XRD method. The polar map had 6 peaks showing 6 rotational symmetries. The XRD pattern did not have diffraction line peaks derived from crystal phases other than AlN and α-alumina. For example, the XRD pattern did not have a peak derived from the crystal phase of aluminum nitride (AlON). The above measurement results showed that the aluminum nitride layer made of a single crystal of AlN directly overlapped the surface of the sapphire layer (sapphire substrate). The above measurement results also showed that the (0001) plane of the aluminum nitride layer was parallel to the surface of the sapphire layer. That is, the (0001) plane of the aluminum nitride layer was parallel to the (11-20) plane of the sapphire layer.

The XRD pattern was measured in the in-plane direction of the surface of the aluminum nitride layer. Based on this XRD pattern, the angle between the (1-100) plane of α-alumina and the (1-100) plane of aluminum nitride was identified. The angle between the (1-100) plane of α-alumina and the (1-100) plane of aluminum nitride was 30 degrees. Therefore, the (11-20) plane of aluminum nitride was parallel to the (1-100) plane of α-alumina.

The φ-scan measured the locking curve of the (1-100) plane of aluminum nitride in the in-plane direction of the surface of the aluminum nitride layer. The full width at half maximum FWHMa of the locking curve of the (1-100) plane of aluminum nitride in the in-plane direction is shown in Table 1 below.

The composition of the substrate was analyzed along the depth direction from the surface of the aluminum nitride layer while gradually digging the surface of the substrate of Example 1 by sputtering. The depth direction is perpendicular to the surface of the aluminum nitride layer and is a direction from the surface of the aluminum nitride layer to the surface of the sapphire layer. For the analysis of the composition, ESCA (Electron Spectroscopy for Chemical Analysis) and SIMS (Secondary Ion Mass Spectrometry) were used. In the analysis along the depth direction, a portion containing only Al and N was detected, and then a portion containing a mixture of aluminum, nitrogen and oxygen was detected. Ca (additive element M) was also detected in the portion where aluminum, nitrogen and oxygen were mixed. That is, the result of the analysis showed that the aluminum nitride layer contained Ca (additive element M). The Ca content in the portion where aluminum, nitrogen and oxygen were mixed was higher than that in the other portion. The maximum value <Ca> max of the Ca content in the aluminum nitride layer is shown in Table 1 below.

The thickness T of the aluminum nitride layer of Example 1 was measured with an ellipsometer. The thickness T of the aluminum nitride layer of Example 1 is shown in Table 1 below.

The aluminum nitride layer identified by the above analysis is a base aluminum nitride layer.

<Formation of buffer layer>
The aluminum nitride layer was grown on the surface of the underlying aluminum nitride layer by the MOCVD step. That is, by the MOCVD step, a buffer layer made of a single crystal of AlN was formed on the surface of the underlying aluminum nitride layer. Trimethylaluminum and ammonia were used as raw materials for the buffer layer. The thickness of the buffer layer was adjusted to 2 μm.

<Analysis 2>
The XRD pattern was measured on the surface of the buffer layer in the same manner as in Analysis 1. The orientation of each crystal plane of aluminum nitride identified from the XRD pattern measured on the surface of the buffer layer coincides with the orientation of each crystal plane of aluminum nitride identified from the XRD pattern measured on the surface of the underlying aluminum nitride layer. bottom.

The φ scan measured the locking curve of the (1-100) plane of aluminum nitride in the in-plane direction of the surface of the buffer layer. The full width at half maximum FWHMb of the locking curve of the (1-100) plane of aluminum nitride in the in-plane direction of the buffer layer is shown in Table 1 below.

(Examples 2 to 5)
In each of the sputtering steps of Examples 2 to 5, the thickness T0 of the aluminum nitride layer was adjusted to the value shown in Table 1 below. In each of the MOD steps of Examples 2 to 5, the concentration [Ca] of the compound of Ca in the MOD solution was adjusted to the value shown in Table 1 below. In each of the reduction nitriding steps of Examples 2 to 5, the reduction nitriding time was adjusted to the values shown in Table 1 below. Except for these matters, the substrates of Examples 2 to 5 were produced in the same manner as in Example 1. The buffer layers of Examples 2 to 5 were formed in the same manner as in Example 1.

Analysis 1 of each of Examples 2 to 5 was performed in the same manner as in Example 1. In all of Examples 2 to 5, the base aluminum nitride layer made of a single crystal of AlN directly overlapped the surface of the sapphire layer. In all of Examples 2 to 5, the (0001) plane of the underlying aluminum nitride layer was parallel to the surface of the sapphire layer. That is, in each of Examples 2 to 5, the (0001) plane of the base aluminum nitride layer was parallel to the (11-20) plane of the sapphire layer.

In all of Examples 2-5, the (11-20) plane of aluminum nitride was parallel to the (1-100) plane of α-alumina.

In all of Examples 2 to 5, in the analysis along the depth direction, a portion containing only Al and N was detected, and then a portion containing a mixture of aluminum, nitrogen and oxygen was detected. In all of Examples 2 to 5, Ca was also detected in the portion where aluminum, nitrogen and oxygen were mixed. That is, in all of Examples 2 to 5, the base aluminum nitride layer contained Ca. In all of Examples 2 to 5, the Ca content in the portion where aluminum, nitrogen and oxygen were mixed was higher than that in the other portions.

Analysis 2 of each of Examples 2 to 5 was performed in the same manner as in Example 1. In any of Examples 2 to 5, the orientation of each crystal plane of the aluminum nitride identified from the XRD pattern measured on the surface of the buffer layer is specified from the XRD pattern measured on the surface of the underlying aluminum nitride layer. It coincided with the orientation of each crystal plane of aluminum nitride.

The <Ca> max of each of Examples 2 to 5 is shown in Table 1 below. The thickness T of each of the base aluminum nitride layers of Examples 2 to 5 is shown in Table 1 below. The FWHMa of Examples 2 to 5 are shown in Table 1 below. The FWHMbs of Examples 2 to 5 are shown in Table 1 below.

(Comparative Example 1)
In the production of the substrate of Comparative Example 1, the sputtering step was not carried out, and the aluminum nitride layer was not formed. In the MOD step of Comparative Example 1, the MOD solution was directly applied to the entire surface of the sapphire substrate. In the MOD step of Comparative Example 1, the concentration [Ca] of the compound of Ca in the MOD solution was adjusted to the value shown in Table 1 below. In the reduction nitriding step of Comparative Example 1, the reduction nitriding time was adjusted to the values shown in Table 1 below. The substrate of Comparative Example 1 was produced in the same manner as in Example 1 except for these matters. The buffer layer of Comparative Example 1 was formed in the same manner as in Example 1.

Analysis 1 of Comparative Example 1 was performed in the same manner as in Example 1. In the case of Comparative Example 1, the base aluminum nitride layer made of a single crystal of AlN directly overlapped the surface of the sapphire layer. In the case of Comparative Example 1, the (0001) plane of the base aluminum nitride layer was parallel to the surface of the sapphire layer. That is, in the case of Comparative Example 1, the (0001) plane of the base aluminum nitride layer was parallel to the (11-20) plane of the sapphire layer.

In the case of Comparative Example 1, the angle between the (1-100) plane of α-alumina and the (1-100) plane of aluminum nitride was zero degree. Therefore, in the case of Comparative Example 1, the (1-100) plane of aluminum nitride was parallel to the (1-100) plane of α-alumina.

In the case of Comparative Example 1, in the analysis along the depth direction, a portion containing only Al and N was detected, and then a portion containing a mixture of aluminum, nitrogen and oxygen was detected. In the case of Comparative Example 1, Ca was also detected in the portion where aluminum, nitrogen and oxygen were mixed. That is, in the case of Comparative Example 1, the base aluminum nitride layer contained Ca. In the case of Comparative Example 1, the Ca content in the portion where aluminum, nitrogen and oxygen were mixed was higher than that in the other portion.

Analysis 2 in the case of Comparative Example 1 was performed in the same manner as in Example 1. In the case of Comparative Example 1, the orientation of each crystal plane of the aluminum nitride identified from the XRD pattern measured on the surface of the buffer layer is each of the aluminum nitrides identified from the XRD pattern measured on the surface of the underlying aluminum nitride layer. It coincided with the orientation of the crystal plane.

<Ca> max in the case of Comparative Example 1 is shown in Table 1 below. The FWHMa of Comparative Example 1 is shown in Table 1 below. The FWHMb of Comparative Example 1 is shown in Table 1 below.

The substrate according to the present invention is used, for example, as a substrate for a deep ultraviolet light emitting diode.

L1 ... Aluminum nitride layer, L1a ... Base aluminum nitride layer, L1b ... Buffer layer, L2 ... Sapphire layer, _SL1 ... Aluminum nitride layer L1 surface, _SL2 ... Sapphire layer L1 surface, 10 ... Substrate, 40 ... n type Semiconductor layer, 42 ... light emitting layer, 44 ... p-type semiconductor layer, 46 ... second electrode, 48 ... first electrode, 100 ... light emitting diode (light emitting element).

Claims (11)

An aluminum nitride layer containing crystalline aluminum nitride,
A sapphire layer containing crystalline α-alumina and
With
The aluminum nitride layer directly overlaps the surface of the sapphire layer.
The (0001) plane of the aluminum nitride is substantially parallel to the surface of the sapphire layer.
The (11-20) plane of the α-alumina is substantially parallel to the surface of the sapphire layer.
The (11-20) plane of the aluminum nitride is substantially parallel to the (1-100) plane of the α-alumina.
substrate. The full width at half maximum of the locking curve of the (1-100) surface of the aluminum nitride measured in the in-plane direction of the surface of the aluminum nitride layer is 0 seconds or more and 500 seconds or less.
The substrate according to claim 1. The full width at half maximum of the locking curve of the (1-100) surface of the aluminum nitride measured in the in-plane direction of the surface of the aluminum nitride layer is 50 seconds or more and 300 seconds or less.
The substrate according to claim 1 or 2. The aluminum nitride layer contains at least one additive element selected from the group consisting of rare earth elements, alkaline earth elements and alkali metal elements.
The substrate according to any one of claims 1 to 3. Of the aluminum nitride layer, the boundary region along the boundary between the aluminum nitride layer and the sapphire layer contains an additive element.
The additive element is at least one element selected from the group consisting of rare earth elements, alkaline earth elements and alkali metal elements.
The total content of the additive elements in the boundary region is 0.1 mass ppm or more and 200 mass ppm or less.
The substrate according to any one of claims 1 to 4. The thickness of the aluminum nitride layer is 50 nm or more and 1000 nm or less.
The substrate according to any one of claims 1 to 5. The thickness of the aluminum nitride layer is 50 nm or more and 500 nm or less.
The substrate according to any one of claims 1 to 6. RC1 (1-100) is a locking curve of the (1-100) plane of the aluminum nitride measured in the in-plane direction of the surface of the aluminum nitride layer.
RC2 (1-100) is a locking curve of the (1-100) plane of the aluminum nitride contained in a region of the aluminum nitride layer in which the distance from the surface of the sapphire layer is 100 nm or less, and is the RC2. (1-100) was measured in an in-plane direction substantially parallel to the surface of the sapphire layer.
The full width at half maximum of RC1 (1-100) is smaller than the full width at half maximum of RC2 (1-100).
The substrate according to any one of claims 1 to 5. Used for light emitting elements,
The substrate according to any one of claims 1 to 8. The substrate according to any one of claims 1 to 9 is provided.
Light emitting element. With the substrate
An n-type semiconductor layer that overlaps the aluminum nitride layer and
A light emitting layer that overlaps the n-type semiconductor layer,
A p-type semiconductor layer that overlaps the light emitting layer and
To prepare
The light emitting element according to claim 10.

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