JP2012216603A - Nitride semiconductor light-emitting element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride semiconductor light-emitting element by which a high-quality buffer layer with suppressed crack generation can be formed on a heterogeneous substrate.SOLUTION: This nitride semiconductor light-emitting element has: a heterogeneous substrate 10 composed of a material different from a nitride semiconductor; a sputter film 20 formed on a principal surface 10a of the heterogeneous substrate 10 and composed of the nitride semiconductor; and a light-emitting element part formed on the sputter film 20 and composed of the nitride semiconductor. The heterogeneous substrate 10 includes a recessed part 15 formed to a part of the principal surface 10a. The recessed part 15 has an inclined plane 16 and is formed substantially in V shape in a cross-sectional view. In the inclined plane 16, an inclination angle on a bottom side of the recessed part 15 is equal to or less than an inclination angle on the principal surface 10a side.

Description

  The present invention relates to a nitride semiconductor light emitting device and a method for manufacturing the same.

  Nitride semiconductors typified by GaN, AlN, InN, and mixed crystals thereof have characteristics that they have a large band gap Eg and are direct transition type semiconductor materials compared to AlGaInAs semiconductors and AlGaInP semiconductors. Yes. For this reason, these nitride semiconductors constitute semiconductor light emitting devices such as a semiconductor laser device capable of emitting light in a wavelength range from ultraviolet to green and a light emitting diode device capable of covering a wide light emission wavelength range from ultraviolet to red. It is attracting attention as a material, and is widely considered for applications such as projectors, full-color displays, and environmental and medical fields.

  In recent years, semiconductor light emitting devices using nitride semiconductors can be applied in a very wide range of fields such as sterilization / water purification, various medical fields, and high-speed decomposition treatment of pollutants by shortening the emission wavelength. The research and development of semiconductor light-emitting elements that emit light in the ultraviolet region are being actively conducted by each research institution.

  In a semiconductor light emitting device using a nitride semiconductor, a sapphire substrate is generally used as a substrate. In addition, a c-plane ((0001) plane) that is a polar plane is used as the growth plane. A nitride semiconductor light emitting device is formed by laminating a nitride semiconductor layer including an active layer on the c-plane.

  However, in the semiconductor light emitting device as described above, there has been an inconvenience so far that it is difficult to improve the quality of AlN, AlGaN, and AlInGaN crystals. Therefore, there is a problem that it is difficult to improve the light emission efficiency of the light emitting element.

  Here, when a heterogeneous substrate made of a material different from a nitride semiconductor such as a sapphire substrate is used as the substrate of the nitride semiconductor light emitting device, it is formed on the substrate due to lattice mismatch with the substrate. There is a disadvantage that the crystal quality of the nitride semiconductor layer is lowered. Therefore, in order to suppress the deterioration of the crystal quality, a method of forming a nitride semiconductor layer on the buffer layer after forming a buffer layer made of a nitride semiconductor on the main surface of the heterogeneous substrate is generally used. ing.

  In order to improve the light emission efficiency of the light emitting element, it is important to improve the quality of the buffer layer made of a nitride semiconductor formed on a heterogeneous substrate (for example, a sapphire substrate).

  As a technique for improving the quality of the buffer layer, for example, in Patent Document 1, an AlN buffer layer is formed on a main surface of a heterogeneous substrate by sputtering, and then nitrided by crystal growth on the AlN buffer layer. A technique for forming a physical semiconductor layer is disclosed. Since the light-emitting element disclosed in Patent Document 1 is a nitride semiconductor light-emitting element that emits light in the blue region, a GaN foundation layer is formed on an AlN buffer layer formed by sputtering so as to be in contact with the AlN buffer layer. ing. A laminated structure made of a nitride semiconductor is formed on the GaN foundation layer.

  In nitride semiconductor light emitting devices that emit light in the deep ultraviolet region, a technique using a template substrate in which an AlN layer is crystal-grown on a sapphire substrate is known (see, for example, Non-Patent Document 1).

  Non-Patent Document 1 discloses a technique in which a recess is formed in an AlN layer of a template substrate, and an AlN buffer layer is regrown on the template substrate. In this non-patent document 1, since the recess is formed in the AlN layer of the template substrate, a void is formed in the AlN buffer layer grown thereon. And since the distortion of the AlN buffer layer is relieved by this void, the quality of the buffer layer is improved. In Non-Patent Document 1, the concave portion is formed by etching, and the shape thereof is substantially rectangular when viewed in cross section.

JP 2008-205267 A

Phys. Status Solidi C6, No. 52, (2009) 5356-5359

In order to realize a high-efficiency light-emitting element that emits light in the deep ultraviolet region, the inventors of the present application use an AlN buffer layer (sputtered film) on a main surface of a different substrate by using a method (for example, sputtering method) that is not a crystal growth method. ), And a method of forming a buffer layer by a crystal growth method so as to be adjacent to (in contact with) the sputtered film has been studied to improve crystal quality. Then, on the AlN layer formed by sputtering, MOCVD (Metal Organic Chemical Vapor Deposition ) method Al high Al composition ratio using _{x In y Ga z N (x} + y + z = 1, Al composition ratio x, for example 0. It has been found that there is a problem that cracks frequently occur when directly growing (85 to 1.00). Further, when the Al composition ratio is increased, cracks tend to increase. In particular, when an AlN film is grown using a crystal growth method, the occurrence of cracks is very remarkable.

  Note that such a phenomenon is not observed when a GaN layer (underlayer) is grown on an AlN buffer layer (sputtered film) formed by sputtering (see Patent Document 1).

  In general, when a semiconductor layer is formed on a buffer layer, the closer the composition of the semiconductor layer is to the composition of the buffer layer, the smaller the lattice mismatch difference and the like, so that cracks are less likely to occur. However, when the nitride semiconductor layer is formed by the crystal growth method on the AlN buffer layer (sputtered film) formed by the sputtering method, an opposite result to the normal case occurs. Although the manufacturing method is different from the sputtered film, the phenomenon that the more the nitride semiconductor layer formed on the sputtered film is closer to the same material as the sputtered film, in other words, the more the cracks occur as the Al composition ratio is increased and closer to AlN. It is a very unique phenomenon. This is a particular problem that occurs when a nitride semiconductor layer having a high Al composition ratio is grown on an AlN sputtered film.

  Here, in order to suppress the occurrence of cracks, it is conceivable to use a method of forming a recess in the AlN layer as in Non-Patent Document 1 above. In this case, since voids are formed in the AlN buffer layer formed on the substrate, it is expected that the generation of cracks is suppressed by the voids.

  However, in this case, since a relatively large void is formed in the AlN buffer layer, the surface of the AlN buffer layer is likely to be uneven. That is, there is an inconvenience that it is difficult to flatten the surface of the AlN buffer layer. Although it is possible to flatten the surface of the layer by increasing the thickness of the AlN buffer layer, in this case, there is a disadvantage that the raw material efficiency is lowered. In addition, throughput is also reduced. Furthermore, if the thickness of the AlN buffer layer is too large, cracks may occur. Therefore, even when the method disclosed in Non-Patent Document 1 is used, it is difficult to effectively improve the quality of the buffer layer.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to form a high-quality buffer layer on which a crack is suppressed on a heterogeneous substrate. And a method for manufacturing the same.

  Another object of the present invention is to provide a nitride semiconductor light emitting device capable of improving luminous efficiency and a method for manufacturing the same.

  As a result of intensive studies by the inventors of the present invention to achieve the above object, the formation of a recess in the main surface portion of a dissimilar substrate and the change of the shape (cross-sectional shape) of the recess suppress the generation of cracks. However, it has been found that the surface of the nitride semiconductor layer (buffer layer) grown on the sputtered film can be easily planarized.

  That is, the nitride semiconductor light emitting device according to the first aspect of the present invention includes a heterogeneous substrate made of a material different from the nitride semiconductor, and a sputter formed on the main surface of the heterogeneous substrate and made of the nitride semiconductor. And a light emitting element portion formed on the sputtered film and made of a nitride semiconductor. In addition, a recess is formed in the main surface portion of the dissimilar substrate. The recess has an inclined surface and is formed in a substantially V shape when viewed in cross section. In addition, the inclined surface of the recess has an inclination angle on the bottom side of the recess that is equal to or less than an inclination angle on the main surface side.

  In the nitride semiconductor light emitting device according to the first aspect, as described above, the shape of the recess formed in the heterogeneous substrate is substantially V-shaped (a shape close to V-shape) when viewed in cross section, The inclined surface is configured such that the inclination angle on the bottom side of the recess is equal to or less than the inclination angle on the main surface side. For this reason, even when a sputtered film is formed on the main surface of the heterogeneous substrate and a nitride semiconductor layer (buffer layer) is grown on the sputtered film, the surface of the buffer layer can be planarized. That is, by forming the recesses as described above, the recesses are relatively easily filled when the buffer layer is grown. Therefore, the layer surface can be planarized without increasing the thickness of the buffer layer. In addition, it is preferable that the recessed part is made into the shape which hardly contains a flat part in the bottom part except the case where it arises by a manufacturing error.

  In addition, by forming the concave portion of the different type of substrate as described above (cross-sectional shape), it is possible to form minute voids (voids) in the buffer layer, so that a nitride having a high Al composition ratio is formed on the sputtered film. Even when the semiconductor layer is grown as a buffer layer, it is possible to suppress the occurrence of cracks in the buffer layer due to the minute holes.

  In addition, when the concave portion of the different substrate has the above shape, the concave portion is easily embedded, so that the surface of the layer is easily flattened. On the other hand, the concave portion is easily embedded, so that the pores are extremely small or completely. It may become extinct.

  In general, it is considered that the crack suppressing effect is brought about by stress relaxation due to voids. For this reason, as described above, when the vacancies become very small or completely disappear, it is considered that the crack suppressing effect is reduced and the cracks are frequently generated.

  However, as a result of various studies by the inventors of the present application, when a nitride semiconductor layer is grown as a buffer layer on a sputtered film, the generation of cracks is suppressed even when the vacancies are very small or no vacancies are formed. I found out that

  As described above, in the first aspect, by forming a recess having the above-described shape on a different substrate, it is possible to suppress cracks generated by growing a nitride semiconductor layer having a high Al composition ratio on the sputtered film. it can. In addition, the surface of the nitride semiconductor layer (buffer layer) can be planarized. Thereby, a high-quality nitride semiconductor layer having a high Al composition ratio can be formed as a buffer layer on a heterogeneous substrate.

  In addition, when a nitride semiconductor layer as a buffer layer is grown on the sputtered film, the crystal quality of the buffer layer is good. Although the crystal quality of the buffer layer increases as the layer thickness increases, a buffer layer of the same quality can be formed with a small thickness by growing the buffer layer on the sputtered film as described above. Even when the thickness of the buffer layer is reduced, as described above, the surface of the layer can be suppressed and unevenness can be suppressed and the surface can be flattened. In addition, by reducing the thickness of the buffer layer, it is possible to suppress the occurrence of cracks due to the buffer layer becoming too thick. Furthermore, by reducing the thickness of the buffer layer, the raw material efficiency can be improved and the throughput can be improved. Therefore, by configuring as described above, the light emission efficiency of the nitride semiconductor light emitting device can be improved. Note that the crystal quality can be improved by increasing the thickness of the buffer layer.

  In the nitride semiconductor light emitting device according to the first aspect, the sputtered film is preferably made of AlN. If comprised in this way, the quality of the buffer layer which consists of a nitride semiconductor with a high Al composition ratio can be improved easily.

  In the nitride semiconductor light emitting device according to the first aspect, the recess is preferably formed such that the opening width is larger than the depth. That is, it is preferable that the recess is formed with a shallow depth. If comprised in this way, since a recessed part can be made easy to be embedded easily, the buffer layer surface can be planarized easily.

  In the above inclined surface, when the angle between the bottom side region of the recess and the normal line of the main surface is θ1, and the angle between the main surface side region and the main surface is θ2, θ1 And θ2 preferably satisfy the relationship of θ2 ≦ θ1 and θ1 is larger than 45 degrees and smaller than 90 degrees. If comprised in this way, it will generate | occur | produce when a buffer layer (for example, AlN layer) which consists of a nitride semiconductor with a high Al composition ratio is grown on an AlN sputtered film, for example on a dissimilar substrate. Cracks can be easily suppressed. Moreover, when the shape of the concave portion is substantially rectangular, the concave portion is difficult to be filled, but the concave portion can be easily filled by forming the concave portion having the above-mentioned angle. For this reason, it is possible to easily form a buffer layer having a flatter surface.

  In this case, the angle θ1 is preferably greater than 60 degrees and smaller than 80 degrees. It is more preferable that the angle θ1 is greater than 65 degrees and smaller than 75 degrees.

  In this case, the angle θ1 is preferably larger than the angle θ2. If comprised in this way, the high quality buffer layer by which generation | occurrence | production of the crack was suppressed can be more easily formed on a dissimilar board | substrate.

  In the nitride semiconductor light emitting device according to the first aspect described above, it is preferable that the inclined surface of the recess is formed in a parabolic shape convex downward when viewed in cross section. Further, the inclined surface of the concave portion may have a shape similar to a downwardly convex parabola (for example, a polygonal shape) or a shape close to a straight line.

In the nitride semiconductor light emitting device according to the first aspect, a sputtered film made of AlN is formed on the main surface of the heterogeneous substrate, and the light emitting device portion is formed of Al _x In formed in contact with the sputtered film. It includes a nitride semiconductor layer made of _{y Ga z N (x + y} + z = 1), the nitride semiconductor layer, the Al and the composition ratio x 0.85 to 1.00, and, Al composition ratio x> Ga composition It is preferable that the relationship of ratio z> In composition ratio y is satisfied.

In the nitride semiconductor light emitting device according to the first aspect, a sputtered film made of AlN is formed on the main surface of the heterogeneous substrate, and the light emitting element portion is formed in contact with the sputtered film. _A nitride semiconductor layer made of _x Ga _1-x N may be included, and the Al composition ratio x of the nitride semiconductor layer may be 0.85 or more and 1.00 or less.

  The nitride semiconductor layer is preferably composed of AlGaN having an Al composition ratio of 0.85 or more and 1.00 or less, and may be composed of AlGaN having an Al composition ratio of 0.90 or more and 1.00 or less. More preferred. The nitride semiconductor layer is more preferably made of AlN.

  In addition, as the heterogeneous substrate, for example, a sapphire substrate, a Si substrate, a SiC substrate, a spinel substrate, a graphite substrate, or the like can be used. As the substrate material has a larger difference in thermal expansion coefficient and lattice constant from the nitride semiconductor, the effect obtained by forming the recess having the above shape becomes more remarkable. Therefore, it is preferable to use a sapphire substrate or a Si substrate as the heterogeneous substrate.

  The nitride semiconductor light emitting device according to the first aspect is suitable for application to a deep ultraviolet light emitting device composed of a nitride semiconductor having a high Al composition ratio. Therefore, in the nitride semiconductor light emitting device according to the first aspect, the light emitting device portion includes an active layer having a quantum well structure, and the active layer includes a well layer including Al and containing a nitride semiconductor, It is preferable that the Al composition ratio of the layer is 0.30 or more and 0.75 or less. Moreover, it is more preferable if the Al composition ratio of the well layer is 0.40 or more and 0.65 or less.

  The method for manufacturing a nitride semiconductor light emitting device according to the second aspect of the present invention includes a step of preparing a dissimilar substrate made of a material different from the nitride semiconductor, and a step of forming a recess in a main surface portion of the dissimilar substrate. Forming a light emitting element portion made of a nitride semiconductor on the main surface of the different substrate. And the process of forming a recessed part includes the scribe process using a point scriber.

  In the nitride semiconductor light emitting device manufacturing method according to the second aspect, as described above, the concave portion having the shape according to the first aspect can be easily formed by a scribing process using a point scriber. That is, by scribing the main surface of the dissimilar substrate using a point scriber, the recess having the above shape can be easily formed. As the point scriber, for example, a material using a high hardness material such as diamond is preferable.

Further, it is preferable to form a protective film on the main surface of the different substrate before scribing the substrate. As the protective film, a dielectric film such as a resist or SiO ₂ can be used. After the scribing process, the protective film is removed. As described above, by forming the protective film before scribing, it is possible to remove the adverse effect of the residue (debris) generated by scribing the substrate.

  A sputtered film formed by a sputtering method can also be used as the protective film. In this case, the sputtered film is preferably an AlN sputtered film.

  As described above, according to the present invention, it is possible to easily obtain a nitride semiconductor light emitting device capable of forming a high-quality buffer layer on which generation of cracks is suppressed on a heterogeneous substrate, and a method for manufacturing the same. .

  Further, according to the present invention, a nitride semiconductor light emitting device capable of improving the light emission efficiency and a method for manufacturing the same can be easily obtained.

FIG. 4 is a cross-sectional view of a dissimilar substrate used in the nitride semiconductor device according to the first embodiment of the present invention (a view corresponding to a cross section taken along line A1-A1 in FIG. 3). FIG. 4 is a cross-sectional view of a dissimilar substrate used in the nitride semiconductor device according to the first embodiment of the present invention (a view corresponding to a cross section taken along line A1-A1 in FIG. 3). 1 is a plan view of a different type substrate according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a state where a buffer layer is formed on a different substrate according to the first embodiment of the present invention. It is a perspective view for demonstrating the manufacturing method of the nitride semiconductor device by 1st Embodiment of this invention. It is a figure (perspective view which showed the point scriber) for demonstrating the manufacturing method of the nitride semiconductor device by 1st Embodiment of this invention. FIG. 7 is a view for explaining the method for manufacturing the nitride semiconductor device according to the first embodiment of the present invention (a view of the point scriber in FIG. 6 viewed from the B direction). FIG. 8 is a view for explaining the method for manufacturing the nitride semiconductor device according to the first embodiment of the present invention (a view of another example when the point scriber of FIG. 6 is viewed from the P direction). It is sectional drawing for demonstrating the manufacturing method of the nitride semiconductor device by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride semiconductor device by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride semiconductor device by 1st Embodiment of this invention. It is sectional drawing for demonstrating the other manufacturing method (other formation method of a recessed part) of the nitride semiconductor element by 1st Embodiment. It is sectional drawing for demonstrating the other manufacturing method (other formation method of a recessed part) of the nitride semiconductor element by 1st Embodiment. FIG. 6 is a view showing a transmission observation image of sample A. It is the figure which showed the crack seen in the transmission observation image of the sample A (figure which traced the crack of FIG. 14). FIG. 6 is a view showing a transmission observation image of sample B. It is a cross-sectional microscope picture of the recessed part provided in the dissimilar board | substrate by 1st Embodiment. FIG. 6 is a cross-sectional view illustrating a nitride semiconductor light emitting device according to a second embodiment of the present invention. FIG. 5 is a cross-sectional view schematically showing a configuration of an active layer of a nitride semiconductor light emitting device according to a second embodiment of the present invention. It is a typical sectional view of a semiconductor optical device carrying a nitride semiconductor light emitting element by a 2nd embodiment of the present invention. FIG. 23 is a cross-sectional view of the dissimilar substrate according to the third embodiment of the present invention (a view corresponding to a cross section taken along line A2-A2 of FIG. 22). FIG. 9 is a plan view illustrating a part of a dissimilar substrate according to a third embodiment of the present invention. FIG. 6 is a perspective view of a dissimilar substrate according to a third embodiment of the present invention. It is a top view (figure showing an example of arrangement of a crevice) of a dissimilar board of a 3rd embodiment of the present invention. It is a top view (figure which showed other examples of arrangement of a crevice) of a dissimilar board of a 3rd embodiment of the present invention. It is sectional drawing (figure which showed the other shape of a recessed part) which showed the dissimilar board | substrate by the 1st modification of this invention. It is sectional drawing (figure which showed the other shape of a recessed part) which showed the dissimilar board | substrate by the 2nd modification of this invention. It is sectional drawing (figure which showed the other shape of a recessed part) which showed the dissimilar board | substrate by the 3rd modification of this invention. It is a top view (figure showing other examples of formation of a groove-like crevice) showing a dissimilar board by a modification of a 1st embodiment. It is a top view (figure showing other examples of formation of a groove-like crevice) showing a dissimilar board by a modification of a 1st embodiment. It is a top view (figure showing other examples of formation of a groove-like crevice) showing a dissimilar board by a modification of a 1st embodiment. It is sectional drawing which showed the structure of the conventional nitride semiconductor element roughly.

  Prior to describing specific embodiments of the present invention, knowledge obtained by various studies by the inventors will be described.

  The inventors of the present application have made various studies in order to improve the quality of the buffer layer formed on the heterogeneous substrate when a heterogeneous substrate made of a material different from the nitride semiconductor is used. At that time, an attempt was made to form a sputtered film on a different substrate and grow a nitride semiconductor layer on the sputtered film.

Specifically, first, a sputtered film made of AlN was formed on the main surface (upper surface) of a different substrate using a magnetron sputtering method or the like. The thickness of the AlN sputtered film is about 50 nm. This AlN sputtered film, high _{Al x In y Ga z N (} x + y + z = 1) made of a nitride semiconductor layer (Al composition ratio x of Al composition ratios by using the MOCVD method, for example 0.70 to 1.00 ) Was directly grown to a thickness of about 1 μm. When the grown nitride semiconductor layer was observed, a phenomenon was observed in which many cracks occurred in the nitride semiconductor layer despite its small thickness of about 1 μm. In addition, the occurrence of cracks tended to increase as the Al composition ratio increased, and the occurrence of cracks was particularly prominent when an AlN layer was grown.

  When a nitride semiconductor layer having a high Al composition ratio was grown on the sputtered film, cracks frequently occurred as described above, but high crystal quality was obtained in a region where no cracks occurred.

  As described above, when the nitride semiconductor layer having a high Al composition ratio is grown on the sputtered film as a buffer layer, the inventors of the present application have a problem that the crystal quality of the nitride semiconductor layer is improved but cracks frequently occur. Found.

  Therefore, the inventors of the present application diligently studied, and formed a recess in the main surface portion of the dissimilar substrate and made the cross-sectional shape of the recess different from a rectangular shape, thereby suppressing the generation of cracks. It was found that a buffer layer was obtained.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings.

(First embodiment)
1 and 2 are cross-sectional views of different types of substrates used in the nitride semiconductor device according to the first embodiment of the present invention. FIG. 3 is a plan view of a dissimilar substrate according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating a buffer layer formed on a different substrate according to the first embodiment of the present invention. First, a heterogeneous substrate used in the nitride semiconductor device according to the first embodiment of the present invention will be described with reference to FIGS.

  The dissimilar substrate 10 according to the first embodiment is composed of, for example, a sapphire substrate, and as shown in FIGS. 1 and 2, a concave portion 15 is formed on the main surface 10a portion (upper surface portion). The recess 15 is formed in a substantially V shape (a shape close to a V shape) different from a rectangular shape when viewed in cross section.

  As shown in FIG. 1, the concave portion 15 has an inclined surface 16 and a bottom portion 17. The inclined surface 16 has an inclination angle on the bottom 17 side (bottom side) equal to or smaller than an inclination angle on the main surface 10a side. It is said that.

  In this case, in the inclined surface 16 of the concave portion 15, the angle formed by the region 16a on the bottom side of the concave portion 15 (the inclined surface close to the bottom) and the normal line P (perpendicular to the substrate surface) of the main surface 10a is θ1, and the main surface The angle θ1 and the angle θ2 satisfy the relationship θ2 ≦ θ1 when the angle between the region 16b on the 10a side (the slope close to the flat portion (main surface 10a)) and the normal line P is θ2, and the angle It is preferable that θ1 be larger than 45 ° and smaller than 90 °.

  The angle θ1 is more preferably an angle greater than 60 degrees and less than 80 degrees, and more preferably an angle greater than 65 degrees and less than 75 degrees.

  The recess 15 of the heterogeneous substrate 10 preferably has a shape that hardly includes a flat portion at the bottom 17 except when it is caused by a manufacturing error.

  Moreover, it is preferable that the inclined surface 16 of the recess 15 has an angle of inclination that is relatively small (angle θ1 and angle θ2 are large). Moreover, the recessed part 15 may be formed so that the inclined surface 16 may become a shape close | similar to a straight line by making the difference of angle (theta) 1 and angle (theta) 2 small. Further, by making the angle θ1 larger than the angle θ2, the concave portion 15 may be formed so that the inclined surface 16 has a shape similar to a downwardly convex parabola. The shape of the inclined surface 16 may be linear as described above, but it is preferable that the inclined surface 16 is on a downwardly convex parabola by setting the angle θ1> the angle θ2.

  Moreover, it is preferable that the depth H of the recessed part 15 is 0.1 to 1.0 micrometer. The depth H of the recess 15 is more preferably 0.7 μm or less, and further preferably 0.2 μm or more and 0.5 μm or less. The width W (opening width) of the recess 15 has a relationship of W to 2H tan θ1 depending on the depth H and the angles θ1 and θ2. In satisfying the relationship, the width W of the recess 15 is preferably 0.2 μm or more and 10.0 μm or less. The width W of the recess 15 is more preferably 7.0 μm or less, and further preferably 5.0 μm or less. Moreover, it is preferable that the said recessed part 15 is formed so that the width W may become larger than the depth H. FIG. That is, the recess 15 is preferably formed in a shape having a shallow depth H and a wide width W.

  As shown in FIG. 3, the concave portion 15 can have a groove shape extending in a predetermined direction. The groove-like recess 15 is preferably formed in a stripe shape. That is, it is preferable that a plurality of recesses 15 extending in parallel with each other be formed in the main surface 10a portion of the different substrate 10. In this case, the interval R (see FIG. 2) between the recesses 15 can be set to, for example, about 100 μm to 500 μm. This range is preferable because a film with good flatness can be obtained. Moreover, since the crack prevention effect mentioned later becomes remarkable, so that the space | interval R is small, if it is 100 micrometers or less, it is more preferable. A more preferable value is 20 μm or less. By making the distance R 20 μm or less, the quality improvement effect becomes more remarkable. More preferably, it is 10 μm or less. Further, the interval R between the recesses 15 may be configured to be larger than the width W of the recesses 15. The interval R between the recesses 15 may be constant, but the interval R can be formed non-uniformly if it is preferable depending on the design of the element (for example, a light emitting element).

  Thus, in 1st Embodiment, while the recessed part 15 is formed in the main surface 10a part of the dissimilar board | substrate 10, the recessed part 15 is made into the substantially V-shaped cross-sectional shape with a shallow depth. For this reason, unlike the case where it is formed in a substantially rectangular shape, the volume of the recess 15 is small, and the source atoms (Al atoms) are easy to move in the recess 15. Therefore, it can be said that the recess 15 has a shape that is relatively easily embedded by the nitride semiconductor.

In the first embodiment, as shown in FIG. 4, the sputtered film 20 is formed on the main surface 10 a (on the upper surface) of the different substrate 10. The sputtered film 20 is made of, for example, AlN and has a thickness of about 20 nm to about 100 nm (for example, about 50 nm). A nitride semiconductor layer (Al composition ratio x is 0.70 or more and 1.00 or less, for example) made of Al _x In _y Ga _z N (x + y + z = 1) having a high Al composition ratio is buffered on the sputtered film 20. Formed as layer 30.

  The buffer layer 30 directly grown on the sputtered film 20 has an Al composition ratio x of 0.85 or more and 1.00 or less, and an Al composition ratio x> Ga composition ratio z> In composition ratio y. It is preferable that it is comprised.

The buffer layer 30 is more preferably composed of Al _x Ga _1-x N having an Al composition ratio x of 0.85 or more and 1.00 or less. By not including In in the buffer layer, the flatness of the buffer layer surface is further improved. The buffer layer 30 is more preferably made of Al _x Ga _1-x N having an Al composition ratio x of 0.90 or more and 1.00 or less. In this case, it is more preferable that the buffer layer 30 is made of AlN.

  The thickness of the buffer layer 30 is preferably 0.5 μm or more. When the buffer layer 30 is thick, the crystal quality is improved. Therefore, the thickness of the buffer layer 30 is more preferably 0.8 μm or more, and further preferably 1.8 μm or more. In addition, as will be described later, the thickness of the buffer layer 30 is preferably 10 μm or less from the viewpoint of cost-effectiveness considering quality improvement effect and raw material consumption.

  FIG. 32 is a cross sectional view schematically showing a configuration of a conventional nitride semiconductor device. Next, referring to FIG. 32 as well, the configuration of the first embodiment will be described in more detail while comparing with the conventional configuration.

  As shown in FIG. 32, a conventional nitride semiconductor device (for example, see Non-Patent Document 1) uses a template substrate 1010 in which an AlN layer 1020 is grown on a sapphire substrate 1000 as a substrate. In the main surface portion of the template substrate 1010 (AlN layer 1020), a rectangular recess 1015 is formed in a sectional view. Then, a buffer layer 1030 made of AlN is formed on the template substrate 1010 in which the recesses 1015 are formed by using the MOCVD method or the like. In addition, since a rectangular recess 1015 is formed in the main surface portion of the template substrate 1010, a relatively large void 1040 is formed in the buffer layer 1030 formed on the template substrate 1010.

  If a void 1040 is formed in the buffer layer 1030, a crack suppressing effect can be obtained. However, if a large void 1040 is formed, the buffer layer 1030 needs to be increased in thickness in order to form a layer in which the void 1040 is formed. . Further, the higher the Al composition ratio of the buffer layer 1030, the harder the void 1040 is embedded in the layer. For example, when the buffer layer 1030 is made of AlN, it is necessary to stack the buffer layer 1030 by 10 μm or more. For this reason, raw material efficiency falls and there exists a subject in cost. Further, when a relatively large void 1040 is formed, it is difficult to ensure the flatness of the layer surface even when the thickness of the buffer layer 1030 is increased. Therefore, there is a problem in flatness.

  In contrast, in the first embodiment, as shown in FIGS. 1 to 4, the recess 15 of the heterogeneous substrate 10 has the above shape (cross-sectional shape), so that the recess 15 can be easily embedded with a nitride semiconductor. It has become. Therefore, the void formed in the buffer layer 30 can be reduced. Therefore, even when the layer includes voids, it is not necessary to increase the thickness of the buffer layer 30. In addition, since the inside of the recess 15 is easily filled with a nitride semiconductor and the formed void is minute, even when the thickness of the buffer layer 30 is reduced, the flatness of the layer surface is improved.

  Further, in the first embodiment, since the minute holes are formed in the buffer layer 30 by forming the recess 15 having the above shape, the nitride semiconductor layer having a high Al composition ratio is buffered on the sputtered film 20. Even when grown as the layer 30, it is possible to suppress the occurrence of cracks in the buffer layer 30 due to the minute holes.

  Furthermore, in the first embodiment, by reducing the growth rate in the growth direction and promoting in-plane growth, it is possible to make the void very small or to eliminate the void completely. And by comprising in this way, it becomes possible to make the flatness of the layer surface of the buffer layer 30 favorable easily.

  Here, it is considered that the crack suppressing effect is brought about by stress relaxation due to voids. For this reason, as described above, when the void becomes very small or completely disappears, it is easily considered that the crack suppressing effect is lowered and the cracks are frequently generated. For this reason, when the concave portion 15 is provided in order to suppress cracks, it is usual to use a shape (for example, a rectangular shape) that does not fill the concave portion as in the conventional structure.

  However, as a result of intensive studies by the inventors of the present application, by providing the concave portion 15 having the above-described shape, not only a minute void is formed in the buffer layer 30, but also a crack is generated even when the void has completely disappeared. Was found to be suppressed. This is a very unique phenomenon. Although details are not clear, when the sputtered film 20 is formed on the heterogeneous substrate 10 and a nitride semiconductor having a high Al composition ratio is grown on the sputtered film 20, it has the above shape as compared with the substrate having a flat surface. By providing the recess 15, it is presumed that stress relaxation occurs, and as a result, cracks can be suppressed.

  As described above, in the first embodiment, the recess 15 formed in the main surface 10a portion of the heterogeneous substrate 10 has the above-described shape, whereby the AlN sputtered film 20 is formed on the heterogeneous substrate 10, and high Al is formed thereon. Even when a nitride semiconductor layer (buffer layer 30) having a composition ratio is grown, it is possible to form a high-quality buffer layer 30 in which the generation of cracks is suppressed.

  5 to 11 are views for explaining a method of manufacturing a nitride semiconductor device according to the first embodiment of the present invention. Next, with reference to FIG. 1 and FIGS. 5 to 11, a method of forming a recess having the above shape on a dissimilar substrate used in the nitride semiconductor device according to the first embodiment of the present invention will be described.

  The concave portion 15 having the shape shown in FIG. 1 is formed by, for example, scribing (scribing process) using a material having high hardness such as diamond as a scribing needle (point scriber). Specifically, as shown in FIG. 5, for example, a sapphire substrate is prepared as the heterogeneous substrate 10, and the main surface 10 a of the heterogeneous substrate 10 is set in a predetermined direction using a scriber 400 (for example, a diamond scriber) as shown in FIG. 6. Scribe. As a result, a substantially V-shaped recess 15 is formed as viewed in cross section, as shown in FIG.

  By adjusting the tip shape of the scriber 400 (see FIG. 6) and the load pressure applied to the scriber 400 (see FIG. 6) at the time of scribing, the shape of the recess 15 (for example, the inclination angle of the inclined surface 16) can be appropriately adjusted. It can be shaped. The scriber 400 is not particularly limited. For example, as shown in FIG. 7, a point scriber having three cut points at the tip part, or a cut point at the tip part as shown in FIG. 8. A point scriber with 4 points can be used. In addition, for example, an 8-point point scriber can be used. Further, the load pressure applied to the point scriber can be, for example, about 0.1N to 0.4N.

  The scribing can also be performed directly on the main surface 10 a of the different substrate 10. In this case, however, residue (debris) may be generated on the substrate surface by scribing the substrate. In such a case, it is preferable to form a protective film on the surface of the heterogeneous substrate 10 before the scribing step.

Specifically, as shown in FIG. 9, a protective film 500 is formed on the main surface 10 a of the heterogeneous substrate 10. The protective film 500 can be a resist film or a dielectric film such as SiO ₂ . Next, as shown in FIG. 10, the heterogeneous substrate 10 is scribed from the formed protective film 500. At this time, the load pressure applied to the point scriber is adjusted so that the recess 15 is formed in the main surface 10a portion of the different substrate 10 through the protective film 500. Thereafter, as shown in FIG. 11, the protective film 500 is removed. Thereby, generation | occurrence | production of the residue by a scribe is suppressed.

  The protective film 500 is more preferably a sputtered film formed by a sputtering method. By using the protective film 500 as the sputtered film, processing-processed irregularities (edges (parts surrounded by a broken line M) that become the boundary between the recess 15 and the flat part (main surface 10a) that are concerned by scribing are generated. It is possible to suppress the adverse effects of The sputtered film constituting the protective film 500 is preferably an AlN sputtered film. Thus, an advantageous effect can be obtained by using a sputtered film (particularly an AlN sputtered film) for the protective film 500. Although the reason why this effect is obtained is not clear, it is considered that the adhesion between the protective film 500 and the substrate 10, the stress of the film itself, and the stress of the substrate 10 and the protective film 500 are affected.

  Even when a sputtered film is formed as the protective film 500, a process of removing the protective film is performed after the scribing process as described above. For removal of the AlN sputtered film after the scribing step, for example, a tetramethylammonium hydroxide (TMAH) aqueous solution or a potassium hydroxide (KOH) aqueous solution can be used.

  In addition to the scribe process, the recess 15 having the above-described shape can be formed by using, for example, a photolithography technique and an etching technique.

  12 and 13 are cross-sectional views for explaining another method for manufacturing the nitride semiconductor device according to the first embodiment. Next, with reference to FIG. 12 and FIG. 13, a method for forming the recess 15 having the above-described shape using a photolithography technique and an etching technique will be described.

  First, as shown in FIG. 12, a protective film 510 is formed on the main surface 10a of the heterogeneous substrate 10 with a photoresist or the like. Next, a substantially V-shaped groove 511 is patterned in a section corresponding to the recess when viewed in cross section. Then, etching is performed using an etching technique such as wet etching or dry etching to selectively remove the main surface 10a portion of the heterogeneous substrate 10 as shown in FIG. Thereafter, the protective film 510 is removed. As a result, the recess 15 having the above-described shape is formed in the main surface 10a portion of the heterogeneous substrate 10.

  In the first embodiment, as described above, the shape of the concave portion 15 formed in the heterogeneous substrate 10 is substantially V-shaped (a shape close to V-shape) when viewed in cross section, and the inclined surface 16 is formed. The inclination angle on the bottom side of the recess 15 is set to be equal to or less than the inclination angle on the main surface 10a side. Therefore, even when the sputtered film 20 is formed on the main surface 10a of the heterogeneous substrate 10 and the nitride semiconductor layer (buffer layer 30) is grown on the sputtered film 20, the surface of the buffer layer 30 is flattened. be able to. That is, by forming the recess 15 as described above, the recess 15 is easily filled when the buffer layer 30 is grown. Therefore, the surface of the buffer layer 30 is planarized without increasing the thickness of the buffer layer 30. can do.

  In addition, by forming the concave portion 15 of the different substrate 10 as described above, it is possible to form minute voids in the buffer layer 30, so that a nitride having a high Al composition ratio is formed on the sputtered film 20. Even when the semiconductor layer is grown as the buffer layer 30, it is possible to suppress the occurrence of cracks in the buffer layer 30 due to the minute holes.

  In addition, by making the concave portion 15 of the heterogeneous substrate 10 have the above shape, the pores can be made very small or completely eliminated. This makes it possible to easily form a flat film. As described above, the occurrence of cracks can be suppressed even in such a configuration.

  As described above, in the first embodiment, by forming the recess 15 having the above-described shape on the heterogeneous substrate 10, cracks generated by growing a nitride semiconductor layer having a high Al composition ratio on the sputtered film 20 are suppressed. can do. In addition, the layer surface of the nitride semiconductor layer (buffer layer 30) can be planarized. Thereby, a high-quality nitride semiconductor layer having a high Al composition ratio can be formed on the heterogeneous substrate 10 as the buffer layer 30.

  Further, when a nitride semiconductor layer as a buffer layer is grown on the sputtered film 20, the crystal quality of the buffer layer 30 is good. Although the buffer layer 30 is improved in crystal quality as the layer thickness is increased, as described above, the buffer layer 30 is grown on the sputtered film 20 to form a buffer layer of the same quality with a small thickness. Can do. Even when the thickness of the buffer layer 30 is reduced, as described above, it is possible to suppress the occurrence of unevenness on the surface of the layer and to flatten the surface. In addition, by reducing the thickness of the buffer layer 30, it is possible to suppress the occurrence of cracks due to the buffer layer 30 becoming too thick. Furthermore, by reducing the thickness of the buffer layer 30, the raw material efficiency can be improved and the throughput can be improved.

  As described above, the crystal quality of the buffer layer 30 can be improved by increasing the thickness of the buffer layer 30. Moreover, the crack prevention effect can be acquired notably by setting the thickness of the buffer layer 30 to 0.8 μm or more. Furthermore, the crack prevention effect can be more remarkably obtained by setting the thickness of the buffer layer 30 to 1.8 μm or more. Although the crystal quality is improved if the thickness of the buffer layer 30 is increased, problems such as material efficiency, throughput, and cracks occur if the thickness is increased excessively. For this reason, the thickness of the buffer layer 30 is preferably 10 μm or less from the viewpoint of cost-effectiveness considering the quality improvement effect and raw material consumption.

  The sputtered film 20 is preferably made of AlN as described above. If comprised in this way, the quality of the buffer layer which consists of a nitride semiconductor with a high Al composition ratio can be improved easily.

  In the first embodiment, the recess 15 can be easily embedded by forming the recess 15 so that the width W is larger than the depth H. Can be flattened.

  Further, by configuring the angle θ1 shown in FIG. 1 to be larger than 45 degrees and smaller than 90 degrees, for example, an AlN sputtered film 20 is formed on the heterogeneous substrate 10, and the Al composition ratio is high thereon. Cracks generated when a buffer layer 30 (for example, an AlN layer) made of a nitride semiconductor is grown can be easily suppressed. Moreover, when the shape of the recessed part 15 is substantially rectangular shape, the recessed part 15 becomes difficult to be filled, but the recessed part 15 can be made easy to fill by forming the recessed part 15 which has the said angle. For this reason, it is possible to easily form the buffer layer 30 having a flatter surface.

Furthermore, by smaller angle than the greater 80 ° than 60 ° the angle .theta.1, Al composition ratio is high on the heterogeneous substrate _{10 Al x In y Ga z N} (Al composition ratio 0.70 to 1.00, In the case of forming a buffer layer 30 made of AlN, for example, the migration length of Al atoms is short. Therefore, if a concave portion having a shape close to a conventional rectangle is formed, the concave portion is difficult to fill, but the concave portion 15 having the above angle is formed. Then, the concave portion 15 is more easily filled. For this reason, it is possible to form a flatter buffer layer 30. In addition, the composition uniformity of the formed buffer layer 30 can be improved.

  Furthermore, by setting the angle θ1 to be larger than 65 degrees and smaller than 75 degrees, in addition to the crack prevention effect, the crystal quality of the buffer layer 30 formed on the heterogeneous substrate 10 and having a high Al composition ratio x can be improved. can do. As the quality improvement effect, when the concave portion 15 having the above-described angle is formed, a growth mode of the flat surface (main surface 10a) and a growth mode of the inclined surface 16 of the concave portion 15 exist. It is considered that crystal defects can be eliminated by effectively combining these growth modes.

  In the first embodiment, if the angle θ1 is larger than the angle θ2, the high-quality buffer layer 30 in which the generation of cracks is suppressed can be more easily formed on the heterogeneous substrate 10.

In the first embodiment, by providing the concave portion 15 having the above shape, the concave portion 15 can effectively prevent cracks in a material with small atomic migration. It is considered that the migration of atoms tends to increase as the atomic radius increases in the order of Ga atoms and In atoms in the order of Ga atoms and In atoms in the order of Al atoms among the adsorbed atoms that have reached the substrate. As can be seen from this, when growing a buffer layer having a high Al composition ratio, it is necessary to treat the heterogeneous substrate 10 having the recess 15 as being completely different from, for example, growing a GaN layer. That is, when the Al composition ratio of Al _x In _y Ga _z N is preferably set to be as high as 0.85 or more and 1.00 or less, and Al composition ratio x> Ga composition ratio z> In composition ratio y Good.

In the first embodiment, the buffer layer 30 is preferably made of Al _x Ga _1-x N having an Al composition ratio x of 0.85 or more and 1.00 or less. If constituted in this way, since the buffer layer 30 does not contain In, the flatness is further improved.

Also, the higher the Al composition ratio, the more remarkable the effect of preventing cracks. Therefore, the higher the Al composition ratio of the buffer layer 30, the better. Therefore, the buffer layer 30 is more preferably made of Al _x Ga _1-x N having an Al composition ratio of 0.90 or more and 1.00 or less, and more preferably made of AlN.

  In addition to the sapphire substrate, for example, a Si substrate, a SiC substrate, a spinel substrate, a graphite substrate, or the like can be used as the heterogeneous substrate 10. As the substrate material has a larger difference in thermal expansion coefficient and lattice constant from the nitride semiconductor, the effect obtained by forming the recess 15 having the above-described shape becomes more prominent. Therefore, it is preferable to use a sapphire substrate or a Si substrate as the heterogeneous substrate.

  A sample A in which an AlN film was formed on a c-plane sapphire substrate by a magnetron sputtering method to a thickness of about 50 nm and a sample B consisting of a c-plane sapphire substrate on which nothing was formed were prepared. Next, using sample A and sample B, an AlN film having a thickness of about 1.0 μm (0.9 μm) was formed by MOCVD under the same conditions. And about the sample A and sample B which formed the AlN film | membrane, the transmission image observation with a microscope was performed.

  FIG. 14 is a diagram showing a transmission observation image of sample A, and FIG. 15 is a diagram showing a crack seen in the transmission observation image of sample A (a diagram obtained by tracing the crack in FIG. 14). FIG. 16 is a view showing a transmission observation image of sample B. FIG. As shown in FIGS. 14 and 15, cracks occurred frequently in Sample A in which an AlN film was grown on an AlN sputtered film. On the other hand, in Sample B in which no AlN sputtered film was formed, no crack was observed as shown in FIG. As described above, it was confirmed that when a sputtered film was formed on a heterogeneous substrate and a nitride semiconductor layer having a high Al composition ratio was grown on the sputtered film, many cracks occurred.

  Next, a sample C (Example) was prepared in which a concave portion having the shape shown in the first embodiment was formed on a c-plane sapphire substrate. The concave portion was formed as follows.

First, an SiO ₂ film having a thickness of about 200 nm was formed on the sapphire substrate as a protective film by sputtering. Next, groove processing (concave processing) was performed by scribing from above the protective film. After the scribing step, the SiO ₂ film as a protective film was removed with buffered hydrofluoric acid.

  A scribe needle made of diamond (Diamond Scriber 3PA Diamond Scriber 3PA) was used to form the recess. A plurality of grooves (recesses) were formed in stripes by attaching the scriber to a scribing device and scribing at a load pressure of about 0.2N. The interval between the recesses (groove interval) at this time is about 20 μm. The depth of the recess was about 0.35 μm, and the width of the recess was 2.850 μm. The angle θ1 of the inclined surface was about 75 degrees, and the angle θ2 was also about 75 degrees. A cross-sectional photomicrograph of the formed recess is shown in FIG.

  Next, an AlN film having a thickness of about 50 nm was formed on the sapphire substrate having the recesses by magnetron sputtering. This substrate was used as Sample C.

  Subsequently, when an AlN film was grown on Sample C under the same conditions as Samples A and B by MOCVD, an AlN film with suppressed cracks was obtained.

  When an AlN film having been crystal-grown using Sample B and Sample C was evaluated by the XRC spectrum half-width, the XRC spectrum half-width of the (0002) plane was 183 seconds for Sample C and 742 seconds for Sample B. It was. That is, it was confirmed that sample C had better crystal quality of the grown AlN film than sample B. From this, it was possible to obtain a high-quality film free of cracks by forming a recess in the c-plane sapphire substrate and having an AlN sputtered film. The XRC spectrum half width of the (10-12) plane was 1017 seconds for sample C and 1280 seconds for sample B.

  In sample C, an AlN film (growth film) was formed with a thickness of 0.9 μm. However, when sample D (example) with an AlN film thickness of 2.0 μm was created, cracks were also generated in this sample D. Was not recognized. When an AlN film was grown to a thickness of 2.0 μm under the same conditions on the same sapphire substrate as that of Sample B (no recesses or sputtered film formed), the occurrence of cracks was observed. From this, it was confirmed that in the sample in which the sputtered film was formed on the substrate having the concave portion having the above shape, the generation of cracks was suppressed even when the thickness of the AlN growth film formed thereon was increased. It was done.

  In addition, the XRC spectrum half width of the (0002) plane was 224 seconds in the sample D, and the XRC spectrum half width of the (10-12) plane was 715 seconds in the sample D. The value of the XRC spectrum half width of the (10-12) plane increases as the number of edge dislocations increases. By increasing the thickness, edge dislocations are reduced, and it is considered that the XRC spectrum half width of the (10-12) plane is reduced.

  The cause of the increase in film thickness is the generation of cracks. The recess (groove) shown in the first embodiment is formed on the sapphire substrate, the AlN sputtered film is formed, and the AlN film is grown by MOCVD. By making it, generation | occurrence | production of a crack can be suppressed. For this reason, further improvement in quality is expected.

(Second Embodiment)
FIG. 18 is a cross-sectional view illustrating a nitride semiconductor light emitting device according to a second embodiment of the present invention. FIG. 19 is a cross-sectional view schematically showing the configuration of the active layer of the nitride semiconductor light emitting device according to the second embodiment of the present invention. A nitride semiconductor light emitting device 200 according to a second embodiment of the present invention is now described with reference to FIGS. In addition, in each figure, the same code | symbol is attached | subjected to a corresponding component, and the overlapping description is abbreviate | omitted suitably.

  The nitride semiconductor light emitting device 200 according to the second embodiment includes a light emitting diode device (deep ultraviolet light emitting device) that emits light in the deep ultraviolet region. The nitride semiconductor light emitting device 200 according to the second embodiment is formed using the heterogeneous substrate 10 shown in the first embodiment. Since the light emitting element that emits light in the deep ultraviolet region includes a nitride semiconductor layer having a high Al composition ratio, the heterogeneous substrate according to the first embodiment is suitable for use as a deep ultraviolet light emitting element.

  The heterogeneous substrate 10 is composed of, for example, a sapphire substrate, and as shown in FIG. 18, a concave portion 15 (see FIG. 1) similar to that of the first embodiment is formed on the main surface 10a portion. . An AlN film 21 is formed on the main surface 10 a of the different substrate 10. The AlN film 21 is a sputtered film formed by using a sputtering method.

On the AlN film 21 is thus in contact with the AlN film 21, Al composition ratio is high nitride semiconductor layer _{(Al x In y Ga z N} : x + y + z = 1) buffer layer 30 made of is formed. The Al composition ratio x of the buffer layer 30 is set to, for example, 0.85 or more and 1.00 or less (for example, AlN). The buffer layer 30 is an example of the “nitride semiconductor layer” in the present invention.

  An element structure 100 including an active layer 50 is formed on the buffer layer 30. This element structure 100 is configured by stacking a plurality of semiconductor layers, and includes an n-side nitride semiconductor layer 110 and a p-side nitride semiconductor layer 120. The n-side nitride semiconductor layer 110 and the p-side nitride semiconductor layer 120 are formed so as to sandwich the active layer 50 therebetween. The buffer layer 30 and the element structure 100 formed on the AlN film 21 constitute a light emitting element portion. However, the light emitting element portion may not include the buffer layer 30. That is, a configuration in which the light emitting element portion is formed on the buffer layer 30 may be used.

  In the specific structure of the second embodiment, as described above, the AlN film 21 is formed on the heterogeneous substrate 10 (for example, sapphire substrate) provided with the recess 15 by sputtering or the like. A buffer layer 30 is formed on the AlN film 21 by a crystal growth method. An n-type AlInGaN layer 40 (110) having a thickness of about 1.8 μm to about 3.5 μm is formed on the buffer layer 30. The active layer 50 is formed on the n-type AlInGaN layer 40.

  On the active layer 50, a carrier block layer 60 made of p-type AlInGaN having a thickness of about 15 nm is formed. A p-type AlInGaN layer 70 having a thickness of about 10 nm is formed on the carrier block layer 60. On the p-type AlInGaN layer 70, a p-type contact layer 80 made of p-type AlInGaN having a thickness of about 50 nm is formed. The p-type contact layer 80 may be made of AlGaN or GaN.

As shown in FIG. 19, the active layer 50 has a quantum well structure in which barrier layers 51 and quantum well layers 52 are alternately stacked. The quantum well layer 52 constituting the active layer 50 is composed of a semiconductor layer represented by a composition formula of Al _x1 In _y1 Ga _{1 -x1-y1} N (0 <x1 ≦ 1, 0 ≦ y1 ≦ 1). . The barrier layer 51 is composed of a semiconductor layer represented by a composition formula of Al _x2 In _y2 Ga _{1 -x2-y2} N (0 <x2 ≦ 1, 0 ≦ y2 ≦ 1). x2 is larger than the Al composition ratio x1 of the quantum well layer 52.

  The Al composition ratio x1 of the quantum well layer 52 is preferably in the range of 0.15 ≦ x1 ≦ 0.90, and more preferably in the range of 0.30 ≦ x1 ≦ 0.75. A range of 0.40 ≦ x1 ≦ 0.65 is more preferable. The In composition ratio y1 is preferably in the range of 0.00 ≦ y1 ≦ 0.12.

  The Al composition ratio x2 of the barrier layer 51 is preferably in the range of 0.20 ≦ x2 ≦ 1.00. The Al composition ratio x2 of the barrier layer 51 is more preferably in the range of 0.30 ≦ x2 ≦ 1.00. More preferably, it is in the range of 0.50 ≦ x2 ≦ 1.00. The In composition ratio y2 is preferably in the range of 0.00 ≦ y2 ≦ 0.08.

  The quantum well layer 52 may be made of AlInGaN containing In or may be made of AlGaN not containing In. Similarly, the barrier layer 51 may be made of AlInGaN containing In or may be made of AlGaN not containing In. When the barrier layer 51 includes In, the In composition ratio y2 is preferably configured to be smaller than the In composition ratio y1 of the quantum well layer 52.

  Note that the Al composition ratio and the In composition ratio of the n-type AlInGaN layer 40 may be set to be the same as those of the barrier layer 51. The composition ratio of the n-type AlInGaN layer 40 and the barrier layer 51 may be different, but it is preferable to set the same as described above because the lattice mismatch difference at the interface is eliminated. When the compositions are different, the band gap of the n-type AlInGaN layer 40 may be configured to be larger than the band gap of the barrier layer 51. When configured in this manner, carriers can be effectively confined in the active layer 50.

  Further, the Al composition ratio and the In composition ratio of the p-type AlInGaN layer 70 may be set to be the same as those of the barrier layer 51 as in the case of the n-type AlInGaN layer 40. The composition ratio between the p-type AlInGaN layer 70 and the barrier layer 51 may be different.

  In the second embodiment, as shown in FIG. 18, the nitride semiconductor light emitting element 200 is configured as a light emitting diode element having a so-called lateral structure. For this reason, a part of the element structure 100 formed on the heterogeneous substrate 10 (for example, a sapphire substrate) is dug to a depth in the middle of the n-type AlInGaN layer 40 from the p-type contact layer 80 by dry etching or the like. . An n-side electrode 140 is formed on the bottom surface of the dug portion (n-type AlInGaN layer 40). The n-side electrode 140 is made of, for example, an Al electrode, or an Ag / Cu electrode having a multilayer structure in which an Ag layer and a Cu layer are sequentially stacked from the substrate side. On the other hand, a p-side electrode 130 is formed on the p-type contact layer 80. The p-side electrode 130 is composed of, for example, a Ni / Au electrode having a multilayer structure in which an Ni layer (not shown) and an Au layer (not shown) are sequentially laminated from the p-type contact layer 80 side. Thus, in the second embodiment, the p-side electrode 130 and the n-side electrode 140 are formed on the upper surface side (growth main surface 10a side) of the heterogeneous substrate 10 (nitride semiconductor layer 20). .

  The nitride semiconductor light emitting element 200 configured as described above is mounted on a can type package 300a and configured in the semiconductor optical device 300, for example, as shown in FIG.

  A method for manufacturing the nitride semiconductor light emitting device 200 according to the second embodiment of the present invention is now described with reference to FIGS.

  First, a different substrate 10 such as a sapphire substrate is prepared. Next, a recess 15 having the same shape is formed in the main surface 10a portion of the different substrate 10 by using the same method as in the first embodiment.

  Next, as shown in FIG. 18, an AlN film 21 is formed on the main surface 10a of the heterogeneous substrate 10 by using a method other than the crystal growth method. The AlN film 21 is preferably a sputtered film using a sputtering method. The thickness of the AlN film 21 can be, for example, about 20 nm to about 100 nm (for example, about 50 nm).

  Subsequently, a plurality of nitride semiconductor layers are stacked on the AlN film 21 by using, for example, the MOCVD method.

Specifically, first, on the AlN film 21, Al composition ratio is high nitride semiconductor layer: forming an _{(Al x In y Ga z N} x + y + z = 1) buffer layer 30 made of. The Al composition ratio x of the buffer layer 30 is preferably 0.85 or more and 1.00 or less (for example, AlN). The composition of the buffer layer 30 is preferably Al composition ratio x> Ga composition ratio z> In composition ratio y. Furthermore, the thickness of the buffer layer 30 is preferably 0.5 μm or more and 10 μm or less, for example. In addition, since the crystal quality improves as the thickness of the buffer layer 30 increases, the thickness of the buffer layer 30 is preferably larger.

  Next, on the buffer layer 30, an n-type AlInGaN layer 40 having a thickness of about 1.8 μm to about 3.5 μm, an active layer 50, a carrier block layer 60 made of p-type AlInGaN having a thickness of about 15 nm, about 10 nm. A p-type AlInGaN layer 70 having a thickness of 1 mm and a p-type contact layer 80 made of p-type AlInGaN having a thickness of about 50 nm are sequentially grown. The p-type contact layer 80 may be made of AlGaN or GaN.

  Further, as shown in FIG. 19, the active layer 50 is configured in a quantum well structure by alternately stacking barrier layers 51 and quantum well layers 52.

  Then, as shown in FIG. 18, a part of the element structure 100 is selectively removed from the p-type contact layer 80 to a depth in the middle of the n-type AlInGaN layer 40 by using a photolithography technique and a dry etching technique. . Thereby, a part of the n-type AlInGaN layer 40 is exposed.

  Thereafter, an n-side electrode 140 is formed on the exposed surface of the n-type AlInGaN layer 40 using a vacuum deposition method or the like, and a p-side electrode 130 is formed on the p-type contact layer 80. Finally, the substrate is diced into individual light emitting elements. Thus, the nitride semiconductor light emitting device 200 according to the second embodiment is formed.

  In the second embodiment, as described above, a high-quality buffer in which cracks are suppressed by forming a light emitting element using the heterogeneous substrate 10 (substrate provided with the recess 15) shown in the first embodiment. An element structure 100 (light emitting element portion) can be formed over the layer 30. Thereby, a deep ultraviolet light emitting element with high luminous efficiency can be obtained.

  In the second embodiment, since the high-quality buffer layer 30 having a flattened layer surface can be formed without increasing the thickness, the raw material efficiency and throughput can be improved.

  In Example 2, a sapphire substrate was used as the heterogeneous substrate, and a groove-shaped recess was formed on the sapphire substrate by a scribing method. At that time, before processing the sapphire substrate, an AlN film was formed as a protective film with a thickness of about 70 nm by magnetron sputtering. Thereafter, scribing was performed at a weighted pressure of about 0.4 N to form a recess having the same cross-sectional shape as in the first embodiment. Similar to Example 1, a plurality of recesses were formed in stripes. The interval between the recesses (groove interval) at this time is about 20 μm. The depth of the recess was about 0.50 μm, and the width of the recess was 2.360 μm. The angle θ1 of the inclined surface was about 70 degrees, and the angle θ2 was also about 70 degrees. After the formation of the recess (groove), the AlN film as a protective film was removed with a tetramethylammonium hydroxide (TMAH) aqueous solution.

  Next, an AlN film was again formed on the sapphire substrate having the recesses (grooves) by about 40 nm by magnetron sputtering. Then, an AlN buffer layer (buffer layer) was grown by MOCVD on a sapphire substrate having a recess and an AlN sputtered film.

Subsequently, an n-type Al _0.65 Ga _0.35 N layer (n-type AlInGaN layer) having a thickness of approximately 2.0 μm, an active layer, and a p having a thickness of approximately 15 nm are formed on the AlN buffer layer (buffer layer) by MOCVD. Carrier block layer made of p-type Al _0.80 Ga _0.20 N, p-type Al _0.65 Ga _0.35 N layer (p-type AlGaN layer) having a thickness of about 10 nm, p-type made of p-type Al _0.10 Ga _0.90 N having a thickness of about 50 nm Contact layers were grown sequentially.

Moreover, the active layer was comprised in the quantum well structure by laminating | stacking a barrier layer and a quantum well layer alternately. The number of quantum well layers was five. In Example 2, the quantum well layer was Al _0.45 Ga _0.55 N, and the barrier layer was Al _0.65 Ga _0.35 N.

  In the configuration of Example 2 above, Sample E (Example) in which an AlN buffer layer having a layer thickness of 1.5 μm was grown on a sapphire substrate having a recess (groove) and an AlN sputtered film, and a layer thickness of 3.5 μm. Sample F (Example) with an grown AlN buffer layer was produced. The structure above the AlN buffer layer was the same for Sample E and Sample F.

  As a comparative example, a sample G in which an AlN buffer layer is formed with a thickness of 1.5 μm on a sapphire substrate not provided with a recess (groove), and a sample H in which an AlN buffer layer is formed with a thickness of 3.5 μm And prepared. In Sample G and Sample H, an AlN buffer layer was formed directly on the sapphire substrate without forming an AlN sputtered film.

  Further, Sample I was prepared in which an AlN buffer layer was formed to a thickness of 3.5 μm on a sapphire substrate having a recess (groove) formed by the above method. Sample I does not have a sputtered film. That is, in Sample I, the AlN buffer layer was formed directly on the sapphire substrate.

Samples E to I have the same structure above the n-type Al _0.65 Ga _0.35 N layer.

  When microscopic observation was performed using Samples E to I, no cracks were observed in Samples E and F. Also, the flatness was good.

  In Samples G and H in which an AlN buffer layer was formed on a sapphire substrate having no recess without a sputtered film, no crack was observed in Sample G with a relatively small thickness of the AlN buffer layer. In sample H where the thickness of the buffer layer was large, many cracks occurred. Further, no crack was observed in Sample I in which a recess (groove) was formed.

  From this, the crack suppression effect by providing the recessed part which has an above-described shape in a board | substrate was confirmed.

  Subsequently, the optical output was compared using samples (samples E, F, G, and I) in which no crack was observed.

  As a result, the optical output during the 20 mA current injection operation was 0.8 mW in the sample G having no recess (groove) and the AlN sputtered film, whereas in the sample E having the recess (groove) and the AlN sputtered film. It increased to 1.3 mW and about 1.6 times. Further, in the sample F in which the thickness of the AlN buffer layer was increased, the light output thereof was 1.3 mW to 1.9 mW. Since it was 0.8 mW in the comparative sample G, the result that the sample E increased compared with the comparative sample G was obtained.

  In Sample I having a recess (groove) and the thickness of the AlN buffer layer increased, the optical output was 1.2 mW, which was about the same as Sample E. Compared with sample G with an optical output of 0.8 mW, sample I also resulted in an increase in optical output. From this, it was confirmed that the optical output increases by increasing the thickness of the AlN buffer layer.

  In addition, since the optical outputs of Sample E and Sample I are approximately the same, it was confirmed that the AlN buffer layer can have a small thickness when the AlN sputtered film is used to obtain approximately the same optical output.

  As described above, it is confirmed that the formation of a recess having the above-described cross-sectional shape on a heterogeneous substrate suppresses the generation of cracks, and the formation of a sputtered film makes it possible to form a buffer layer of the same quality with a small thickness. It was done.

(Third embodiment)
FIG. 21 is a cross-sectional view of a dissimilar substrate according to the third embodiment of the present invention. FIG. 22 is a plan view illustrating a part of a dissimilar substrate according to the third embodiment of the present invention. FIG. 23 is a perspective view of a dissimilar substrate according to the third embodiment of the present invention. 24 and 25 are plan views of different types of substrates according to the third embodiment of the present invention. Next, with reference to FIGS. 12, 13, and 21 to 25, a heterogeneous substrate according to a third embodiment of the present invention will be described. In addition, in each figure, the same code | symbol is attached | subjected to a corresponding component, and the overlapping description is abbreviate | omitted suitably.

  In the heterogeneous substrate 10 according to the third embodiment, as shown in FIGS. 21 to 23, the recess 15 (15a) is formed in a hole shape. That is, the third embodiment is different from the first and second embodiments in that the concave portion 15 is formed in a hole shape and the concave portion is formed in a groove shape extending in a predetermined direction.

  The hole-shaped recess 15 is formed of a substantially inverted conical recess. Therefore, the hole-shaped recess 15 is formed in a circular shape when viewed in a plan view. Further, as shown in FIG. 21, the cross-sectional shape is the same shape as the first embodiment described above (substantially V-shape (shape close to V-shape)).

  Also in the third embodiment, it is preferable that the concave portion 15 of the heterogeneous substrate 10 has a shape that hardly includes a flat portion at the bottom portion 17 except when it is caused by a manufacturing error.

  Further, as shown in FIGS. 23 to 25, it is preferable that a plurality of hole-shaped recesses 15 are periodically provided in the main surface 10 a portion of the different substrate 10. In this case, it is preferable that the interval between adjacent recesses 15 is a periodic structure having a constant interval. In addition, the arrangement | sequence of the recessed part 15 can be made into the grid | lattice form as shown to FIG. 24 and FIG. However, the arrangement of the recesses 15 may be an arrangement other than the arrangement shown in FIGS.

  The depth H (see FIG. 21) of the recess 15 is preferably 0.1 μm or more and 1.0 μm or less, as in the first embodiment. The depth H of the recess 15 is more preferably 0.7 μm or less, and further preferably 0.2 μm or more and 0.5 μm or less.

  The diameter D (W) (see FIG. 21) of the recess 15 has a relationship of D to 2H tan θ1 depending on the depth H and the angles θ1 and θ2. In satisfying the relationship, the diameter D of the recess 15 is preferably 0.2 μm or more and 10.0 μm or less. The diameter D of the recess 15 is more preferably 7.0 μm or less, and further preferably 5.0 μm or less. Moreover, it is preferable that the said recessed part 15 is formed so that the diameter D may become larger than the depth H. FIG. That is, the recess 15 is preferably formed in a shape having a shallow depth H and a wide diameter D.

  Further, as shown in FIGS. 24 and 25, the interval R (R1, R2) between the recesses 15 can be, for example, about 10 μm to 50 μm. This range is preferable because a film with good flatness can be obtained. Moreover, since the crack prevention effect becomes remarkable as the space | interval R is small, More preferably, 20 micrometers or less are good. A more preferable value is 10 μm or less. By making the distance R 10 μm or less, the quality improvement effect becomes more remarkable. Furthermore, it is preferable to set the interval R to 30 μm or less because the effect of improving the light extraction efficiency due to scattering appears.

  Such a hole-like recess 15 can be formed using a photolithography technique and an etching technique. Specifically, as shown in FIGS. 12 and 13, a protective film 510 such as a photoresist is formed on the heterogeneous substrate 10, and dry etching or the like is performed using the protective film 510 as a mask. Thereafter, by removing the protective film 510, it is possible to periodically form the hole-shaped recess 15 described above.

  Other configurations of the third embodiment are the same as those of the first and second embodiments.

  In addition, even when the recess 15 is formed in a hole shape in the main surface 10a portion of the heterogeneous substrate 10, the same operation and effect as in the first embodiment can be obtained.

  In Example 3, as shown in FIGS. 12 and 13, periodic holes (recesses 15) were formed in the main surface 10a portion of the dissimilar substrate 10 made of a sapphire substrate using a dry etching method.

  Specifically, as shown in FIG. 12, a photoresist was formed as a protective film 510 on the main surface 10 a of the heterogeneous substrate 10. S1830 manufactured by Dow Chemical Company was used for this photoresist. Next, as shown in FIG. 13, after the dry etching was performed using the protective film 510 as a mask, the protective film 510 was removed. In this way, a recess 15 having a cross-sectional shape as shown in FIG. 21 was formed. At this time, the diameter of the recess (hole) was 1.850 μm, and the depth of the recess (hole) was about 0.40 μm. The angle θ1 of the inclined surface was about 68 degrees, and the angle θ2 was about 67 degrees. The interval between the recesses (holes) was 10 μm.

  As a comparative sample, a substrate (sapphire substrate) on which a groove-like recess similar to the first embodiment (Example 1) was formed was prepared. The width of the groove-shaped recess is 1.850 μm and the depth is about 0.40 μm. The interval between the grooves (recesses) was 10 μm.

  Using the sample according to Example 3 and the comparative sample, an AlN sputtered film similar to that of Example 2 was formed on the main surface. Then, the same AlN buffer layer as in Example 2 and the structure thereon were grown by MOCVD. Thereafter, a part of the element structure was removed by etching, and then an electrode was formed to produce a light emitting diode element. Note that the thickness of each AlN buffer layer was about 4.8 μm.

  When these samples were observed with a microscope, no cracks were observed in any of the samples. Further, the flatness of the layer surface was good.

  Next, these samples were used to compare the light output during a 20 mA current injection operation. As a result, in the comparative sample (the sample in which the groove-shaped concave portion was formed), the light output was 1.8 mW. On the other hand, in the sample (Example 3) in which the periodic hole-shaped concave portions were formed, the light output was 2.2 mW, and the light output increased compared to the comparative sample. This is presumably because the light and the extraction efficiency were improved by the periodic structure of the hole-like recesses.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first to third embodiments, an example in which a sputtered film (AlN sputtered film) made of AlN is formed on a heterogeneous substrate is shown. However, the present invention is not limited to this, and the sputtered film is an AlN sputtered film. It may be other than. Examples of the sputtered film other than AlN include sputtered films such as AlON, GaN, GaON, GaO, AlGaN, SiC, and ZnO.

  In the first to third embodiments, an example is shown in which a sputtered film is formed on a heterogeneous substrate using a sputtering method, and a buffer layer is formed on the sputtered film by a crystal growth method. For example, a film (for example, an AlN film) may be formed on a different substrate using a method other than sputtering, and a buffer layer may be formed on the film. That is, as long as the orientation of the nitride semiconductor layer crystal-grown thereon is maintained, the method for forming the film may be a method other than sputtering. Examples of methods other than sputtering include molecular beam growth (MBE), electron beam evaporation, and plasma CVD. When a method other than the sputtering method is used, any method can be used as long as the film quality and effects equivalent to those of a film (for example, an AlN film) formed by the sputtering method can be obtained. Alternatively, the buffer layer may be directly grown on the heterogeneous substrate without forming a sputtered film.

  Moreover, in the said 1st-3rd embodiment, although the example which made the cross-sectional shape of the recessed part substantially V-shaped was shown, this invention is not restricted to this, The cross-sectional shape of a recessed part is other than substantially V-shaped, Also good. In this case, the cross-sectional shape of the concave portion is preferably a shape in which the concave portion is easily embedded. For example, as shown in FIG. 26, the cross-sectional shape of the recess 15 may be a shape that is slightly closer to a U shape than a substantially V shape. As shown in FIG. 27, the cross-sectional shape of the recess 15 may be a polygonal shape in which the inclined surface is composed of a plurality of surfaces having different inclination angles. Furthermore, as shown in FIG. 28, the cross-sectional shape of the recess 15 may be substantially arcuate. In addition, the cross-sectional shape of the recessed part 15 may be shapes other than these.

  In the first to third embodiments, the MOCVD method is used as the crystal growth method. However, the present invention is not limited to this, and the crystal growth method is not limited to the MOCVD method, for example, the MBE method or the CBE method. It may be.

  In the first to third embodiments, the buffer layer made of a nitride semiconductor having a high Al composition ratio is formed on the sputtered film. However, the present invention is not limited to this, and the buffer layer is made of Al. The composition ratio can be appropriately set including a relatively low range. For example, the Al composition ratio of the buffer layer may be a value lower than 0.7. However, since an advantageous effect can be obtained by configuring the buffer layer from a nitride semiconductor having a high Al composition ratio, the Al composition ratio of the buffer layer is preferably 0.7 or more.

  Moreover, in the said embodiment, the off angle (off angle of a main surface) of a board | substrate is not specifically limited. If there is a special off-angle such as improvement in flatness, it is possible to make that angle.

  In the first and second embodiments, the groove-like recess means a shape including a fluctuation that appears as a manufacturing error unintentionally when a groove (recess) is formed.

  In the first and second embodiments, the shape of the groove (concave portion) is not limited to the stripe shape. For example, as shown in FIGS. 29 and 30, the recesses 15 may be formed in a lattice shape. Moreover, as shown in FIG. 31, the recessed part 15 may be wavy. Furthermore, the shape which combined these may be sufficient.

  Moreover, in the said 2nd Embodiment, although the example which applied this invention to the light emitting diode element which is an example of the nitride semiconductor light emitting element was shown, this invention is not restricted to this, Nitride semiconductor light emission other than a light emitting diode element The present invention can also be applied to an element. For example, the present invention can be applied to a nitride semiconductor laser element which is an example of a nitride semiconductor light emitting element. The present invention can also be applied to semiconductor elements such as electronic devices.

  In the above embodiment, the element structure (nitride semiconductor layers) formed on the substrate can be appropriately combined with or changed in thickness, composition, or the like according to desired characteristics. is there. For example, the semiconductor layers may be added or deleted, or the order of the semiconductor layers may be partially changed. Further, the electrode material and the like are only examples, and are not limited to the above examples.

  In the second embodiment, the light emitting diode element that emits light in the ultraviolet wavelength region (deep ultraviolet wavelength region) has been described as an example of the light emitting diode device. However, the present invention is not limited to this, and other than ultraviolet (deep ultraviolet). It is also possible to obtain a light emitting element that emits light in the wavelength region.

  Further, in the second embodiment, the example in which the nitride semiconductor light emitting element is mounted on the can type package has been shown. However, the present invention is not limited to this, and the nitride semiconductor may be used in a package other than the package shown in the above embodiment. A light emitting element can also be mounted.

  In the second embodiment, the example in which the nitride semiconductor light emitting element is configured in a horizontal structure has been described. However, the present invention is not limited to this, and the nitride semiconductor light emitting element can also be configured in a vertical structure. is there. For example, when a conductive substrate is used, the nitride semiconductor light emitting device can have a vertical structure. Of course, a horizontal structure may be used. In addition, when a non-conductive substrate is used, the nitride semiconductor light emitting element can be configured in a lateral structure as shown in the above embodiment.

  Moreover, in the said 3rd Embodiment, the example which formed the recessed part in circular shape seeing planarly was shown, However, this invention is not restricted to this, The planar shape of a recessed part is shapes other than circular shape, Also good. For example, a triangular shape, a quadrangular shape, or a polygonal shape having five or more corners may be used. In the third embodiment, an example in which the hole-shaped concave portion is formed in the shape of an inverted conical recess has been shown, but an inverted triangular pyramid shape, an inverted quadrangular pyramid shape, or an inverted polygonal pyramid shape having five or more pentagons may be used. Good.

  Moreover, in the said 3rd Embodiment, although the example which formed the hole-shaped recessed part by the etching was shown, this invention is not restricted to this, It can also form using methods other than an etching. For example, a hole-shaped recess can be formed by pressing a needle-like member such as a point scriber against the substrate surface. In addition, for example, it is possible to use a technique such as imprinting using a mold provided with a plurality of convex portions corresponding to the hole-shaped concave portions. In this case, a plurality of recesses can be easily formed at a time.

  Embodiments obtained by appropriately combining the techniques (configurations) disclosed above are also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Different substrate 10a Main surface 15 Recess 16 Inclined surface 16a Region 16b Region 17 Bottom 20 Sputtered film 21 AlN film 30 Buffer layer (nitride semiconductor layer)
40 n-type AlInGaN layer layer 50 active layer 51 barrier layer 52 quantum well layer 60 carrier block layer 70 p-type AlInGaN layer layer 80 p-type contact layer 100 device structure 110 n-side nitride semiconductor layer 120 p-side nitride semiconductor layer 130 p Side electrode 140 N-side electrode 200 Nitride semiconductor light emitting element 300 Semiconductor optical device 400 Point scriber 500, 510 Protective film

Claims (18)

A heterogeneous substrate made of a material different from a nitride semiconductor;
A sputtered film formed on the main surface of the heterogeneous substrate and made of a nitride semiconductor;
A light emitting element portion formed on the sputtered film and made of a nitride semiconductor;
The heterogeneous substrate includes a recess formed in the main surface portion,
The concave portion has an inclined surface and is formed in a substantially V shape when viewed in cross section.
The nitride semiconductor light emitting device, wherein the inclined surface has an inclination angle on a bottom side of the recess that is equal to or less than an inclination angle on the main surface side.   The nitride semiconductor light emitting device according to claim 1, wherein the sputtered film is made of AlN.   The nitride semiconductor light emitting device according to claim 1, wherein an opening width of the recess is larger than a depth. In the inclined surface,
When the angle between the bottom side region of the recess and the normal of the main surface is θ1, and the angle between the main surface side of the main surface and the normal of the main surface is θ2,
The nitride semiconductor light emitting device according to claim 1, wherein θ1 and θ2 satisfy a relationship of θ2 ≦ θ1, and θ1 is greater than 45 degrees and smaller than 90 degrees.   5. The nitride semiconductor light emitting device according to claim 4, wherein the angle θ <b> 1 is larger than 60 degrees and smaller than 80 degrees.   5. The nitride semiconductor light emitting device according to claim 4, wherein the angle θ <b> 1 is larger than 65 degrees and smaller than 75 degrees.   The nitride semiconductor light emitting device according to claim 4, wherein the angle θ1 is larger than the angle θ2.   The nitride semiconductor light emitting device according to any one of claims 1 to 7, wherein the inclined surface of the concave portion is formed in a parabolic shape convex downward when viewed in cross section. A sputtered film made of AlN is formed on the main surface of the heterogeneous substrate,
The light emitting element portion includes a nitride semiconductor layer made of Al _x In _y Ga _z N (x + y + z = 1) formed in contact with the sputtered film,
9. The nitride semiconductor layer according to claim 1, wherein the nitride semiconductor layer has an Al composition ratio x of 0.85 or more and 1.00 or less and satisfies a relationship of x>z> y. The nitride semiconductor light emitting device according to item. A sputtered film made of AlN is formed on the main surface of the heterogeneous substrate,
The light emitting element portion includes a nitride semiconductor layer made of Al _x Ga _1-x N formed in contact with the sputtered film,
9. The nitride semiconductor light emitting device according to claim 1, wherein an Al composition ratio x of the nitride semiconductor layer is 0.85 or more and 1.00 or less.   The nitride semiconductor light emitting device according to claim 10, wherein the nitride semiconductor layer is made of AlN.   The nitride semiconductor light-emitting element according to claim 1, wherein the heterogeneous substrate is one of a sapphire substrate, a Si substrate, a SiC substrate, a spinel substrate, and a graphite substrate.   The nitride semiconductor light-emitting element according to claim 1, wherein the heterogeneous substrate is a sapphire substrate.   The nitride semiconductor light-emitting element according to claim 1, wherein the heterogeneous substrate is a Si substrate. The light emitting element portion includes an active layer having a quantum well structure,
The active layer has a well layer made of a nitride semiconductor containing Al,
The nitride semiconductor light-emitting element according to claim 1, wherein an Al composition ratio of the well layer is 0.30 or more and 0.75 or less. Preparing a heterogeneous substrate made of a material different from a nitride semiconductor;
Forming a recess in a main surface portion of the heterogeneous substrate;
Forming a light emitting element portion made of a nitride semiconductor on the main surface of the heterogeneous substrate,
The method of manufacturing a nitride semiconductor light emitting device, wherein the step of forming the recess includes a scribing step using a point scriber. The step of forming the recess includes
Forming a protective film on the main surface of the heterogeneous substrate prior to the scribing step;
The method for manufacturing a nitride semiconductor light emitting device according to claim 16, further comprising a step of removing the protective film after the scribing step.   The method of manufacturing a nitride semiconductor light emitting element according to claim 17, wherein the step of forming the protective film includes a step of forming the protective film from AlN using a sputtering method.