Light-emitting element and method for manufacturing light-emitting element

Abstract

The invention relates to a light-emitting element and a method for manufacturing the light-emitting element. The purpose of the invention is to obtain a light-emitting element having excellent adhesion between a protective film and a semiconductor layer. This light-emitting element is a flip-chip-type light-emitting element, and is provided with: a buffer layer formed on the main surface of a substrate; an n-type AlGaN layer formed on the buffer layer; and a light-emitting layer and a p-type AlGaN layer that are sequentially formed on at least a part of the n-type AlGaN layer, the light-emitting element being characterized in that an exposed surface of the substrate is provided at an end of the main surface of the substrate, and in a cross section of the light-emitting element, the exposed surface is inclined at an acute angle [theta] s of 45 DEG or less with respect to a horizontal line of an interface between the substrate and the buffer layer.

Description

Technical Field

[0001] The present invention relates to GaN-based and AlGaN-based light-emitting elements and a method for manufacturing the light-emitting elements. Background Art

[0002] GaN-based and AlGaN-based Group III nitride semiconductors are used for light-emitting elements in the ultraviolet wavelength region of 200 nm to 280 nm (UVC), 280 nm to 320 nm (UVB), and 320 nm to 400 nm (UVA).

[0003] For example, Patent Document 1 describes that at least one of the end face of the light-emitting layer or the outer side face of the insulating film in contact with the end face of the light-emitting layer is tilted relative to the surface parallel to the light-emitting layer in such a manner that the angle formed between its normal and the surface parallel to the light-emitting layer is greater than a predetermined angle. This is because when the end face of the light-emitting layer of the light-emitting element is tilted relative to the surface parallel to the light-emitting layer, reflected light that could not be extracted from the light extraction surface can be extracted by end face reflection.

[0004] In a conventional flip-chip light-emitting element, etching is performed to expose an n-type semiconductor layer in order to form an n-type electrode, and then etching is performed to form a street region.

[0005] Patent document 2 describes the following sequence of steps: a mask is formed to expose the n-type semiconductor layer, and reactive ion etching (RIE) is performed using SiCl4 gas and Cl2 gas. Then, after removing the mask, a mask having a pattern of a predetermined chip size is applied, and etching is performed by RIE until the sapphire substrate is exposed, thereby forming a scribe line area.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2003-347589

[0009] Patent Document 2: Japanese Patent Application Publication No. 2000-4066 Summary of the invention

[0010] Problem that the invention aims to solve

[0011] In recent years, while further improving the luminous efficiency of light-emitting elements, it is also required to improve the reliability of light-emitting elements. In light-emitting elements, an insulating film such as SiO2 or SiN is often provided as a protective film in a manner that completely covers the group III nitride semiconductor to suppress leakage current and protect the element from moisture, etc. When such a protective film peels off or cracks, the adhesion between the protective film and the semiconductor layer deteriorates, which may damage the reliability of the element.

[0012] Patent Document 1 shows that the end portion on the main surface of the substrate has an exposed surface of the substrate and the exposed surface is also covered with a protective film. However, Patent Document 1 does not consider the peeling of the protective film and the inclination of the exposed surface of the substrate. Patent Document 2 also does not consider the protective film.

[0013] An object of the present invention is to provide a light-emitting element in which peeling, cracking, etc. of a protective film are unlikely to occur, and a method for producing the light-emitting element.

[0014] Solutions for solving problems

[0015] The inventors of the present invention have repeatedly conducted in-depth studies to achieve the above technical problems, and as a result, found that the angle at which the protective film contacts the semiconductor layer on the surface where the substrate contacts the semiconductor layer is important in order to prevent peeling and cracking of the protective film. In addition, the inventors of the present invention have found that in order to set such an angle, after etching to the substrate to form a scribe line region, it is appropriate to perform etching to expose the n-type semiconductor layer in order to form an n-type electrode.

[0016] That is, the gist of the present invention is as follows.

[0017] (1) A light-emitting element, which is a flip-chip type light-emitting element, comprising: a buffer layer formed on a main surface of a substrate; an n-type AlGaN layer formed on the buffer layer; and a light-emitting layer and a p-type AlGaN layer formed in sequence on at least a portion of the n-type AlGaN layer, characterized in that an exposed surface of the substrate is provided at an end portion on the main surface of the substrate, and in a cross section of the light-emitting element, the exposed surface has an inclined portion inclined at an acute angle θs of less than 45° relative to a horizontal line of an interface between the substrate and the buffer layer.

[0018] (2) The light emitting element according to (1) above, wherein the acute angle θs is 2°<θs<30°.

[0019] (3) A light-emitting element according to (1) or (2) above, wherein when the angle formed by the interface and the side surface of the buffer layer in the buffer layer is set to θb, θs<30°≤θb≤75°, and θs+(180°-θb) is greater than 120°.

[0020] (4) In the light emitting element according to any one of (1) to (3) above, an end portion where an exposed surface of the n-type AlGaN layer intersects a side surface of the n-type AlGaN layer is formed in an R-plane shape.

[0021] (5) The light-emitting element according to any one of (1) to (4) above, wherein the substrate includes a sapphire substrate, and the buffer layer includes at least an undoped AlN buffer layer.

[0022] (6) The light-emitting element according to any one of (1) to (5) above, further comprising a protective film, the protective film covering at least the side surfaces of the p-type AlGaN layer, the light-emitting layer, the n-type AlGaN layer and the buffer layer, and covering at least the inclined portion.

[0023] (7) A method for manufacturing a light-emitting element, characterized in that it comprises: a first step, which includes a step of forming a buffer layer on a main surface of a substrate, a step of forming an n-type AlGaN layer on the buffer layer, and a step of sequentially forming a light-emitting layer and a p-type AlGaN layer on the n-type AlGaN layer; a second step of etching at least a portion of the p-type AlGaN layer, the light-emitting layer, the n-type AlGaN layer and the buffer layer to the substrate to form a scribed area on the substrate; and a third step of, after the second step, again etching the p-type AlGaN layer and the light-emitting layer to expose a portion of the n-type AlGaN layer, wherein in a cross section after the third step, the scribed area of ​​the substrate has an inclined portion inclined at an acute angle θs of less than 45° relative to a horizontal line of an interface between the substrate and the buffer layer.

[0024] (8) The method for manufacturing a light-emitting element according to (7) above also includes a fourth step of forming a protective film on at least the side surfaces of the p-type AlGaN layer, the light-emitting layer, the n-type AlGaN layer and the buffer layer formed by etching in the second and third steps, and forming a protective film on at least the inclined portion of the scribed area of ​​the substrate.

[0025] Effects of the Invention

[0026] According to the present invention, a light-emitting element in which peeling, cracking, and the like of a protective film are unlikely to occur and a method for manufacturing the light-emitting element can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic cross-sectional view for explaining the angle θs and the angle θb in the present invention.

[0028] Figure 2 It is a schematic cross-sectional view showing the structure of a light emitting element according to the present invention.

[0029] Figure 3A This is a first process diagram for explaining the method for manufacturing the light emitting element according to the present invention.

[0030] Figure 3B This is a second process diagram for explaining the method for manufacturing the light emitting element according to the present invention.

[0031] Figure 3C This is a third process diagram for explaining the method for manufacturing the light emitting element according to the present invention.

[0032] Figure 4A This is a first process diagram for explaining a manufacturing method when a light-emitting element similar to that of the present invention is manufactured using a conventional manufacturing method.

[0033] Figure 4B This is a second process diagram for explaining a manufacturing method when a light-emitting element similar to that of the present invention is manufactured using a conventional manufacturing method.

[0034] Figure 4C This is a third process diagram for explaining a manufacturing method when a light-emitting element similar to that of the present invention is manufactured using a conventional manufacturing method.

[0035] Figure 5 This is a diagram showing a cross-sectional SEM image of the light-emitting element according to Example 1.

[0036] Figure 6 This is a diagram showing a cross-sectional SEM image of the light-emitting element according to Example 2. DETAILED DESCRIPTION

[0037] Before describing the embodiment according to the present invention, the following points will be described in advance.

[0038] Figure 1 It is a part of the cross-sectional view of the light-emitting element in this embodiment. A buffer layer 20 and an n-type AlGaN layer 30 are sequentially stacked on the substrate 10, and an n-type electrode 130 is formed on a part of the n-type AlGaN layer 30. Except near the center of the upper surface of the n-type electrode 130 and near the separation predetermined portion of the substrate 10, a protective film is formed on the exposed surface of the substrate 10, the side surface of the buffer layer 20, the side surface of the n-type AlGaN layer 30, the upper surface of the n-type AlGaN layer 30, the side surface of the n-type electrode 130, and the periphery of the upper surface. The back side of the substrate 10 is a light extraction surface.

[0039] <Angle θs>

[0040] The angle θs is Figure 1The angle BAC is obtained when the contact point between the exposed substrate 10 and the buffer layer 20 is set as A, an arbitrary point on the inclined portion of the exposed substrate 10 (exposed surface) is set as B, and an arbitrary point on the horizontal line of the interface between the substrate 10 and the buffer layer 20 and located outside the light-emitting element is set as C. Figure 1 The horizontal line of the interface between the substrate 10 and the buffer layer 20 is more inclined toward the light extraction surface. When the exposed surface on the substrate 10 is inclined in a straight line, point B can be any point on the straight line. When the exposed surface on the substrate 10 is inclined in a broken line or a curved line, point B can be set at the position of the straight line that contacts the exposed surface of the substrate 10 starting from the contact point A. The exposed substrate 10 refers to a state where there is no semiconductor layer between the protective film and the substrate 10, including a state covered by a protective film. Among them, in Figure 2 Hereinafter, the illustration of the protective film will be omitted. Figure 1 The inclined portion (between AB in the figure) is called the inclined portion.

[0041] <Angle θb>

[0042] exist Figure 1 In the figure, angle θb is the angle between the interface between the substrate 10 and the buffer layer 20 and the side surface of the buffer layer 20. When the side surface of the buffer layer 20 is a straight line, it can be the angle formed with the straight line. When the side surface of the buffer layer 20 is a broken line or a curve, a straight line contacting the side surface of the buffer layer 20 is drawn from the contact point A as the starting point, and the angle formed with the straight line can be set.

[0043] The evaluation of the above-mentioned tilt angle (θs, θb) in this embodiment is performed as follows: a cross section is formed on the light-emitting element using FIB (focused ion beam) or the like, a cross-sectional SEM (scanning electron microscope) image is obtained, and the angle of the image is measured. For example, in this embodiment, a cross-sectional SEM image of 20,000 times is obtained, the horizontal line of the interface between the substrate 10 and the buffer layer 20 of the image is drawn, a straight line contacting the exposed surface of the substrate 10 starting from the contact point A, and a straight line contacting the side surface of the buffer layer 20 are drawn, and these angles are measured.

[0044] The evaluation of the adhesion of the protective film in this embodiment is performed by obtaining a cross-sectional SEM image and confirming whether there are cracks, voids or peeling of the protective film in the image. For example, in this embodiment, the vicinity of the contact point A is confirmed by a cross-sectional SEM image at a magnification of 20,000 times.

[0045] In this embodiment, "AlGaN" means AlGaN when the Al composition ratio is a. a Ga 1-aN. The value of the Al composition ratio a of AlGaN in this embodiment is determined by the wavelength observed by photoluminescence measurement performed on the surface of each layer when each layer is grown. Unless otherwise specified, the Al composition ratio a is greater than or equal to 0 and less than or equal to 1. As a method for determining the Al composition ratio from the cross section of the light-emitting element, for example, EDS (energy dispersive X-ray analysis) can be used.

[0046] The principal surface of the semiconductor layer in this embodiment refers to a surface most suitable for crystal growth among the crystal plane orientations.

[0047] The dopant concentration in the present invention uses a value measured by SIMS (Secondary Ion Mass Spectrometry). In this specification, when no specific impurities such as Si or Mg are intentionally added and the layer does not function electrically as a p-type or n-type, it is referred to as "i" type or "undoped". Undoped layers may be mixed with unavoidable impurities during the manufacturing process. Specifically, when the dopant density is small and close to the detection limit in SIMS (for example, less than 4×10 16 / cm 3 ), it is regarded as “unadulterated” in this specification.

[0048] The evaluation of crystallinity in this embodiment is based on the half-value width (arcsec) of the X-ray rocking curve of the X-ray diffractometer. The half-value width can be calculated automatically by the application software attached to the X-ray diffractometer.

[0049] Hereinafter, one embodiment of the present invention will be described.

[0050] (Light-emitting element)

[0051] The light-emitting element obtained by this embodiment is described. The light-emitting element involved in this embodiment is a flip-chip type light-emitting element 100, which includes: a buffer layer 20 formed on the main surface 10A of a substrate 10; an n-type AlGaN layer 30 formed on the buffer layer 20; and a light-emitting layer 40 and a p-type AlGaN layer 50 formed in sequence on at least a portion of the n-type AlGaN layer 30.

[0052] like Figure 2 As shown, the buffer layer 20 preferably includes an AlN buffer layer 21 and may include a first buffer layer 22 or a second buffer layer 23 made of AlGaN. A p-type cladding layer 60 or a p-type contact layer 70 may also be formed on the p-type AlGaN layer 50 in sequence.

[0053] In the light emitting element 100, the substrate 10 has an exposed surface at an end on the main surface 10A, and the exposed surface is characterized by having an inclined portion inclined at an acute angle θs of less than 45° relative to the horizontal line of the interface between the substrate 10 and the buffer layer 20. In addition, the substrate 10 is preferably a sapphire substrate. The entire exposed surface may be an inclined portion, and a portion of the exposed surface may not be inclined. In the case where a portion of the exposed surface is not inclined, the non-inclined portion may be horizontal.

[0054] The angle θs is preferably 2°<θs<30°, and more preferably 5°≤θs≤15°. The angle θb is preferably 30°≤θb≤75°, and more preferably 45°≤θb≤65°. As the relationship between the angle θs and the angle θb, θs+(180°-θb) is preferably 120° or more, and more preferably 125° or more.

[0055] In the light emitting element 100 , the end portion where the exposed surface on the principal surface of the n-type AlGaN layer 30 intersects the side surface of the n-type AlGaN layer 30 inclined at the angle θb is preferably formed in an R-plane shape.

[0056] When forming a protective film covering the light emitting element 100, it is preferred that the protective film does not produce peeling and cracks. The protective film is preferably formed in a manner that covers the buffer layer 20, the n-type AlGaN layer 30, the light emitting layer 40, the p-type AlGaN layer 50, the p-type cladding layer 60, the side surfaces of the p-type contact layer 70 and the inclined portion of the substrate 10. The protective film is preferably not formed at least on the central portion (joint region) of the upper surface of the p-side electrode and the n-type electrode, and may cover the outer periphery of the p-side electrode and the n-type electrode.

[0057] By forming a protective film on the light emitting element 100 according to the present invention, a light emitting element can be obtained in which the protective film is less likely to peel off or crack. Hereinafter, each configuration will be described in detail by describing an embodiment of a manufacturing method for obtaining the light emitting element 100 and each step thereof.

[0058] (Method for manufacturing light emitting element)

[0059] Figure 3A to Figure 3C FIG. 1 is a process diagram of a method for manufacturing the light emitting element 100. Figure 3A to Figure 3C As shown, the method for manufacturing the light emitting element 100 according to the present invention comprises: a first step ( Figure 3A ), epitaxially growing each semiconductor layer on the main surface 10A of the substrate 10 to form a film; the second step ( Figure 3B ), etching the semiconductor layer formed in the first step to the substrate 10 to form a scribe line region; and a third step ( Figure 3C ), and dry etching is performed again to expose the main surface of the n-type AlGaN layer 30.

[0060] 《Step 1》

[0061] In the first step, a substrate 10 is first prepared. A substrate manufactured by a conventional method can be used as the substrate 10. The substrate 10 preferably includes a sapphire substrate.

[0062] The buffer layer 20, the n-type AlGaN layer 30, the light-emitting layer 40 and the p-type AlGaN layer 50 are sequentially formed on the substrate 10 to form a light-emitting element 100 ( Figure 3A ). Hereinafter, each layer constituting the light emitting element 100 will be briefly described.

[0063] First, the buffer layer 20 is epitaxially grown on the substrate 10. The buffer layer 20 can be formed by, for example, a metal organic vapor deposition (MOCVD: Metal Organic Chemial Vapor Deposition) method. The buffer layer 20 preferably includes an AlN buffer layer 21, and further, a first buffer layer 22 or a second buffer layer 23 composed of AlGaN can be sequentially stacked on the AlN buffer layer 21. The film thickness of the AlN buffer layer 21 is preferably greater than 0.3 μm and less than 0.7 μm. The AlN buffer layer 21 is preferably undoped. The Al composition ratio of AlGaN in the first buffer layer 22 and the second buffer layer 23 may be the same or different. In the case where the Al composition ratios of the first buffer layer 22 and the second buffer layer 23 are different, the Al composition ratio of the first buffer layer 22 is preferably higher. The film thickness of the first buffer layer 22 is preferably greater than 10 nm and less than 50 nm, and the film thickness of the second buffer layer 23 is preferably greater than 200 nm and less than 2000 nm. In addition, the first buffer layer 22 and the second buffer layer 23 are preferably undoped.

[0064] Next, an n-type AlGaN layer 30 is stacked on the buffer layer 20. The film thickness of the n-type AlGaN layer 30 may be sufficient to supply carriers, and is preferably 300 nm to 3000 nm, for example. Here, elements doped in the n-type AlGaN layer 30 include Si and the like.

[0065] Next, a light-emitting layer 40 is stacked on the n-type AlGaN layer 30. The light-emitting layer 40 is preferably a layer including a layer composed of AlGaN. The light-emitting layer 40 may be a single-layer structure or a multi-quantum well structure in which a plurality of barrier layers and well layers are alternately stacked. In the figure of this embodiment, a multi-quantum well structure is exemplarily illustrated. In addition, although not illustrated, an undoped AlGaN layer having a film thickness of 1 nm or more and 5 nm or less may be provided on the light-emitting layer 40 in contact therewith.

[0066] Next, a p-type AlGaN layer 50 is stacked on the above-mentioned light-emitting layer 40. In addition, a p-type cladding layer 60 may be provided on the p-type AlGaN layer 50. The p-type cladding layer 60 is composed of p-type AlGaN, and preferably has an Al composition ratio lower than that of the p-type AlGaN layer 50. As the elements doped in the p-type AlGaN layer 50 and the p-type cladding layer 60, Mg and the like can be listed. In order to facilitate the formation of electrodes, a p-type contact layer 70 composed of p-type AlGaN may be provided on the p-type cladding layer 60. The p-type contact layer is preferably composed of a p-type GaN layer, and as the doped elements, Mg and the like can be listed.

[0067] 《Step 2》

[0068] In the second step, first, preferably using a CVD (Chemical Vapor Deposition) device, an insulating film is formed on the entire surface of the p-type contact layer 70. As the insulating film that can be used, for example, SiO2 or SiN can be listed. In this embodiment, the insulating film is set as a SiO2 layer for description. This SiO2 layer can play the role of a mask during RIE described later.

[0069] Next, for the SiO2 layer on the p-type contact layer 70, a mask pattern is preferably formed using a resist, and then the SiO2 layer is removed by etching in a well-shaped area having a scribe width (scribe area, scribe width range: 50 to 150 μm) sufficient to allow the separation predetermined line based on the laser scriber to be located near the center. Then, the resist is preferably removed. Then, as Figure 3B As shown, the III-nitride layer in the scribe line region not covered by the SiO 2 layer is completely etched using an RIE device, thereby exposing the substrate 10 in the scribe line region. Figure 3B is a schematic diagram at the end of etching. Figure 3B The diagram schematically shows the result of etching the III-nitride layer in the depth direction and side etching, with the side of the III-nitride layer being inclined and forming an eave on the mask of the SiO2 layer. The vertical and horizontal dimensions of the figure do not represent the ratio of the actual object, but are exaggerated for ease of understanding. Figure 3C , Figure 4B , Figure 4C The same is true in China.

[0070] 《Step 3》

[0071] In the third step, if Figure 3CAs shown, in order to form an n-type electrode later, the main surface of the n-type AlGaN layer 30 is exposed. First, preferably, a mask pattern is formed using a resist, and the SiO2 layer on the p-type contact layer 70 in the region (light-emitting region) desired to be retained in the p-type semiconductor layer (p-type contact layer 70, p-type cladding layer 60, and p-type AlGaN layer 50) and the light-emitting layer 40 is retained, and the other SiO2 layers are removed by etching. Then, as shown in FIG. Figure 3C As shown, the n-type AlGaN layer 30 in the area not covered by the SiO2 layer is exposed using an RIE apparatus. By performing the third step after the second step, the substrate 10 in the scribe line region exposed in the scribe line forming step is subjected to a second etching.

[0072] In the second process of the scribing formation process, it is necessary to etch all of the p-type contact layer 70, the p-type cladding layer 60, the p-type AlGaN layer 50, the light-emitting layer 40, the n-type AlGaN layer 30 and the buffer layer 20. Since the etching depth is deep, more than several 1000nm, it is preferred to use a combination of gases with a high etching rate for AlGaN. For example, a combination of (Cl2 gas, BCl3 gas) can be used. Through this etching, the depth of the III-nitride layer to be etched can be determined according to the thickness of the epitaxially grown light-emitting element.

[0073] On the other hand, in the process of exposing the n-type AlGaN layer 30 in the third process, the p-type contact layer 70, the p-type cladding layer 60, the p-type AlGaN layer 50 and the light-emitting layer 40 can be etched. Since the etching depth is about 10 nm to 100 nm, it is preferable to use a combination of gases whose etching rate of AlGaN is lower than that in the scribing formation process. For example, a combination of (Cl2 gas, SiCl4 gas) can be used. Thus, an angle θs is formed on the substrate 10 that has been exposed away from the mask, and an inclined portion is formed in the scribing area. Through this etching, the depth of the group III nitride to be etched can be determined according to the thickness of the epitaxially grown light-emitting element. It is preferable to reliably expose the surface of the n-type AlGaN layer 30 by advancing the etching until a part of the light-emitting layer side of the n-type AlGaN layer 30 is etched.

[0074] In addition, it is preferred that the etching conditions based on the RIE device for achieving a low aspect ratio in the second and third steps, and the etching conditions of the SiO2 layer in the third step are optimized respectively, so that the end portion where the exposed surface of the main surface of the n-type AlGaN layer 30 intersects with the side surface of the n-type AlGaN layer 30 is formed in the shape of an R-face.

[0075] As described above, after partially exposing the n-type AlGaN layer 30, the SiO2 layer on the p-type contact layer 70 may be removed by etching. It is preferable to remove at least the SiO2 layer at a position where the p-side electrode 120 described later is to be formed.

[0076] It is preferable to form a p-side electrode 120 on the p-type contact layer 70. It is preferable that the p-side electrode 120 is a known electrode that can be used for the p-type contact layer 70, and is preferably a reflective electrode. As the p-side electrode 120, for example, the first metal (Ni) and the second metal (Rh), or a conductive metal nitride can be used.

[0077] Furthermore, it is preferable to form an n-type electrode 130 on the exposed portion of the n-type AlGaN layer 40. As the n-type electrode 130, a known electrode may be selected, and for example, the first metal (Ti) and the second metal (Al), or a conductive metal nitride may be used.

[0078] The p-side electrode 120 and the n-type electrode 130 can be stacked using a known film growth method, such as sputtering. The electrode patterning of the p-side electrode 120 and the n-type electrode 130 is preferably formed using a lift-off method using a resist.

[0079] In the manufacturing method of the present invention, after the etching for forming the scribe area in the second step, the etching for exposing the n-type AlGaN layer 30 in the third step is performed. In the past, the etching for forming the scribe area was usually performed after the etching for exposing the n-type semiconductor layer. However, by performing the etching for exposing the n-type semiconductor layer after the etching for forming the scribe area, it is possible to form an angle θs with the exposed surface of the substrate 10 relative to the horizontal line of the interface between the substrate 10 and the buffer layer 20. In addition, the angle θb formed by the interface between the substrate 10 and the buffer layer 20 and the inclined surface of the buffer layer 20 is smaller than before. As a result, it is difficult to produce peeling and cracking of the protective film described later.

[0080] 《Step 4》

[0081] The protective film is formed at least in the area except for the central part (joint area) of the upper surface of the p-side electrode and the n-type electrode. In addition, in order to prevent the protective film from evaporating and reattaching due to laser irradiation to contaminate the electrode surface or the protective film surface, it is preferred that there is no protective film at the laser irradiation position of the laser scriber, exposing the sapphire substrate.

[0082] The fourth step as a step of forming a protective film is a step of forming a protective film on at least the side surfaces of the p-type AlGaN layer, the light-emitting layer, the n-type AlGaN layer and the buffer layer formed by etching in the second and third steps, and at least the inclined portion of the scribed area of ​​the substrate. The thickness of the protective film can be set to 0.2 μm to 3 μm. The protective film is preferably set to SiO2, SiN, SiON or a combination thereof.

[0083] Finally, after contact annealing using an infrared lamp annealing heating device, it is preferred to use a laser scriber to separate the individual rectangular components with a chip size of 500 μm×500 μm or more and 1500 μm×1500 μm or less. In addition, the thickness of the sapphire substrate after component separation is preferably 100 μm or more and 600 μm or less.

[0084] Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to the following examples.

[0085] [Example 1]

[0086] (Experimental Example 1)

[0087] A sapphire substrate (diameter: 2 inches, film thickness: 430 μm, plane orientation (0001), m-axis deviation angle θ: 0.5°) was prepared, and an AlN buffer layer with a central film thickness of 600 nm was grown on the sapphire substrate by MOCVD with a growth temperature set to 1200° C. Then, it was heated at 1650° C. for 4 hours in a heat treatment furnace under a nitrogen atmosphere.

[0088] The half value width of the (10-12) X-ray rocking curve of the AlN layer of the AlN template substrate measured by an X-ray diffraction apparatus (D8 DISCOVER AUTOWAFS; manufactured by Bruker AXS, CuKα1 ray) was 288 seconds, which was 300 seconds or less.

[0089] After obtaining the AlN template substrate, an undoped Al 0.40 Ga 0.60 Next, a first buffer layer composed of undoped Al was formed. 0.25 Ga 0.75 The second buffer layer with a film thickness of 1000 nm was composed of N. The total film thickness of the undoped first buffer layer and the second buffer layer measured from the cross-sectional SEM image was 1030 nm.

[0090] Next, Si-doped Al is formed on the second buffer layer. 0.25 Ga 0.75N with a thickness of 2400 nm. In addition, after the growth temperature was changed from 1200°C to 1100°C, Si-doped Al was formed on the n-type semiconductor layer. 0.25 Ga 0.75 The n-type guide layer is composed of N and has a thickness of 25 nm.

[0091] Next, the Si-doped Al 0.25 Ga 0.75 The barrier layer is composed of 12 nm N and the undoped Al 0.10 Ga 0.90 A well layer with a film thickness of 2.4 nm composed of N is formed to form a light-emitting layer with a quantum well structure.

[0092] Then, an undoped Al 0.25 Ga 0.75 Then, the supply of the Group III raw material gas was stopped while the Group V raw material gas was still being supplied. The nitrogen gas as the carrier gas was stopped and the carrier gas was changed to hydrogen gas. The supply of the Group III raw material gas was started 1 minute after the start of the hydrogen supply to form an Al doped with Mg. 0.4 Ga 0.6 Next, a 22 nm thick p-type electron blocking layer composed of N was formed. 0.22 Ga 0.78 N with a thickness of 64nm, and then a p-type contact layer (p-type GaN contact layer) with a thickness of 4nm is formed by Mg-doped GaN. With the change of the above carrier gas, the Ga component of the i-type guide layer is volatilized and decomposed, and the i-type guide layer with a thickness of 1.0nm and an Al composition ratio of about 1 is transformed.

[0093] A SiO2 layer is formed on the entire surface of the p-type contact layer using a CVD device. This SiO2 layer serves as a mask during RIE.

[0094] For the SiO2 layer on the p-type contact layer, a mask pattern is formed using a resist, and then, after removing the SiO2 layer in the band-shaped scribe area (scribe width: 100 μm) containing the separation predetermined line based on the laser scriber using buffered hydrofluoric acid, the resist is also removed. Using an RIE device, etching is performed for 16 minutes using Cl2 gas and BCl3 gas as etching gas. As a result, the III-nitride layer in the scribe area not covered by the SiO2 layer is completely etched, exposing the sapphire substrate in the scribe area.

[0095] Next, a mask pattern is formed using a resist, and the SiO2 layer on the p-type semiconductor layer (p-type contact layer, p-type cladding layer, and p-type electron blocking layer) and the area (light-emitting area) desired to be retained in the light-emitting layer is retained. After removing the other SiO2 layers using buffered hydrofluoric acid, the resist is also removed. Using RIE, Cl2 gas and SiCl4 gas are used as etching gases for 9 minutes and 30 seconds to expose the n-type semiconductor layer in the range not covered by the SiO2 layer. The thickness from the interface between the AlN buffer layer and the first buffer layer to the surface of the exposed n-type semiconductor layer was measured from the cross-sectional SEM image, and the result was 3000nm.

[0096] When the n-type semiconductor layer is exposed, the sapphire substrate in the scribe line region exposed in the scribe line forming step is subjected to a second etching. Then, the SiO2 layer (mask) on the p-type contact layer is removed using buffered hydrofluoric acid.

[0097] Next, a Ni layer with a thickness of 7 nm and a Rh layer with a thickness of 50 nm were formed on the p-type contact layer to form a reflective electrode serving as a p-side electrode.

[0098] Furthermore, a Ti layer with a thickness of 20 nm and an Al layer with a thickness of 150 nm were formed on a portion of the exposed n-type semiconductor layer to form an n-type electrode.

[0099] The p-side electrode and the n-type electrode were stacked by sputtering, and the p-side electrode and the n-type electrode were patterned by lift-off using a resist.

[0100] In addition, contact annealing is performed at 550°C for 10 minutes using an infrared lamp annealing heating device. Next, a protective film composed of SiO2 with a target thickness of 1 μm is formed on the entire surface except for the separation predetermined line based on the laser scriber and the central part of the upper surface of the p-side electrode and the n-type electrode (joining area). Then, a laser scriber is used to separate the individual elements into rectangular elements with a chip size of 1000 μm×1000 μm to produce the ultraviolet light-emitting element involved in Example 1 (hereinafter sometimes referred to as the light-emitting element). The side surface of the sapphire substrate is perpendicular to the main surface, and the thickness of the sapphire substrate after the element separation is 430 μm.

[0101] (Example 2)

[0102] The light emitting element according to Example 2 was obtained in the same manner as in Example 1 except that the thickness of the second buffer layer was changed to 250 nm. The total thickness of the undoped first buffer layer and the second buffer layer measured by the cross-sectional SEM image was 280 nm. The thickness from the interface between the AlN buffer layer and the first buffer layer to the surface of the exposed n-type semiconductor layer was measured by the cross-sectional SEM image and was 2050 nm.

[0103] (Comparative Example)

[0104] Reference Figure 4A to Figure 4C , shows a process diagram for making the same light-emitting element using the existing manufacturing method. First, a semiconductor layer is epitaxially grown on a sapphire substrate to form a light-emitting element ( Figure 4A ). This step is the same as the first step in the embodiment.

[0105] Next, a SiO2 layer is formed on the entire surface of the p-type contact layer 70 using a CVD device, and a mask pattern is formed using a resist, so that the SiO2 layer on the p-type contact layer 70 in the region (light-emitting region) of the p-type semiconductor layer (p-type contact layer 70, p-type cladding layer 60, and p-type AlGaN layer 50) and the light-emitting layer 40 that is desired to be retained is retained, and the other SiO2 layers are removed by etching. Then, as Figure 4B As shown, the n-type AlGaN layer 30 in the area not covered by the SiO 2 layer is exposed using an RIE device.

[0106] As described above, after a portion of the n-type semiconductor layer is exposed, a scribing formation process is performed. Since the SiO2 layer outside the light-emitting area has been removed in the process of exposing the n-type semiconductor layer, a SiO2 layer is formed again in the scribing formation process to cover the area outside the scribing area including the exposed upper surface of the n-type semiconductor layer. Using this SiO2 layer as a mask during RIE, the etching time in the scribing formation process is changed from 16 minutes to 12 minutes, and the group III nitride layer in the scribing area that is not covered by the SiO2 layer is completely etched to expose the sapphire substrate in the scribing area. Here, the light-emitting element involved in the comparative example is obtained in the same manner as in Example 1, except that the order of the scribing formation process and the process of exposing the n-type semiconductor layer is reversed and the etching time in the scribing formation process is changed. Unlike Example 1 or Example 2, in the light-emitting element involved in the comparative example, the sapphire substrate in the scribing area is only etched once in the scribing formation process. In this case, as Figure 4C As shown, no inclined portion is generated on the sapphire substrate in the scribe line region.

[0107] The cross-sectional SEM images of Examples 1 and 2 are shown in Figure 5 , Figure 6. The figure records the horizontal line of the interface between the sapphire substrate and the AlN buffer layer on the AlN template substrate, the angle (θs) between the horizontal line and the inclined portion of the sapphire substrate, and the angle (θb) between the horizontal line and the AlN buffer layer. In Example 1, θs is 7° and θb is 61°. In Example 2, θs is 5° and θb is 55°. Here, in Examples 1 and 2, the sapphire substrate is tilted 2μm horizontally to the right from the contact point between the sapphire substrate and the side of the AlN layer on the cross-sectional SEM image. The area that exceeds 2μm to the horizontal right is flat. On the other hand, in the comparative example, the angle (θs) between the horizontal line and the inclined portion of the sapphire substrate is 0, and no inclined portion is generated. In addition, the angle (θb) between the boundary line and the AlN buffer layer is 82°.

[0108] Table 1 shows the evaluation of θs, θb, 0s+(180°-θb) and the adhesion between the protective film and the semiconductor layer in Examples 1, 2 and the Comparative Example. θs+(180°-θb) is the angle at which the protective film contacts the semiconductor layer on the surface where the sapphire substrate contacts the side of the AlN layer. Regarding the value of θs+(180°-θb), it is 126° in Example 1 and 130° in Example 2. Since the value of θs+(180°-θb) is large enough, no gaps or cracks are observed between the protective films, and the adhesion is sufficient. On the other hand, in the Comparative Example, the value of θs+(180°-θb) is 98°, which is close to a right angle, and gaps or cracks are sometimes observed locally in the portion where the protective film contacts.

[0109] [Table 1]

[0110] θs θb θs+(180°-θb) Adhesion Example 1 7° 61° 126° ○ Example 2 5° 55° 130° ○ Comparative Example 0° 82° 98° ×

[0111] Based on the above results, by controlling the angles θs and θb so that θs+(180°-θb) is equal to or greater than 120°, a semiconductor device can be obtained in which peeling and cracking of the protective film are unlikely to occur.

[0112] Description of Reference Numerals

[0113] 100 Light emitting elements

[0114] 10 Sapphire substrate

[0115] 20 Buffer layer

[0116] 30 n-type AlGaN layer

[0117] 40 Luminous Layer

[0118] 50 p-type AlGaN layer

[0119] 60 p-type cladding

[0120] 70 p-type contact layer

[0121] 120 p side electrode

[0122] 130 n-type electrode

Claims

1. A light emitting element, which is a flip chip type light emitting element, comprising: a buffer layer formed on a major surface of the substrate; an n-type AlGaN layer formed on the buffer layer; and The light emitting layer and the p-type AlGaN layer are sequentially formed on at least a portion of the n-type AlGaN layer, characterized in that: The end portion on the main surface of the substrate has an exposed surface of the substrate, In a cross section of the light emitting element, the exposed surface has an inclined portion inclined at an acute angle θs of 45° or less with respect to a horizontal line of an interface between the substrate and the buffer layer.

2. The light-emitting element according to claim 1, wherein The acute angle θs is 2°<θs<30°.

3. The light-emitting element according to claim 1, wherein When the angle between the interface and the side surface of the buffer layer in the buffer layer is θb, θs<30°≤θb≤75°, θs+(180°-θb) is greater than or equal to 120°.

4. The light-emitting element according to claim 1, wherein An end portion where an exposed surface of the n-type AlGaN layer intersects a side surface of the n-type AlGaN layer is formed in an R-plane shape.

5. The light emitting element according to claim 1, wherein The substrate comprises a sapphire substrate, The buffer layer at least includes an undoped AlN buffer layer. 6 . The light emitting element according to claim 1 , further comprising a protective film, the protective film covering at least the side surfaces of the p-type AlGaN layer, the light emitting layer, the n-type AlGaN layer, and the buffer layer, and covering at least the inclined portion.

7. A method for manufacturing a light emitting element, characterized in that: include: A first step includes forming a buffer layer on a main surface of a substrate, forming an n-type AlGaN layer on the buffer layer, and sequentially forming a light emitting layer and a p-type AlGaN layer on the n-type AlGaN layer; In a second step, at least a portion of the p-type AlGaN layer, the light-emitting layer, the n-type AlGaN layer, and the buffer layer is etched down to the substrate, thereby forming a scribe line region on the substrate; as well as A third step is to further etch the p-type AlGaN layer and the light emitting layer after the second step, thereby exposing a portion of the n-type AlGaN layer. In the cross section after the third step, the scribe region of the substrate has an inclined portion inclined at an acute angle θs of 45° or less with respect to a horizontal line of an interface between the substrate and the buffer layer.

8. The method for manufacturing a light-emitting element according to claim 7 further includes a fourth step of forming a protective film on at least the side surfaces of the p-type AlGaN layer, the light-emitting layer, the n-type AlGaN layer and the buffer layer formed by etching through the second and third steps, and forming a protective film on at least the inclined portion of the scribed area of ​​the substrate.

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