JP2007123613A - Light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance light extraction efficiency of a light-emitting device, by suppressing decline in external quantum efficiency of a light-emitting device caused by a pad electrode. <P>SOLUTION: The light-emitting device 1 comprises a light-emitting diode 2, having an n-type nitride semiconductor layer 22, a p-type nitride semiconductor layer 24 formed on the n-type nitride semiconductor layer 22, a p-type electrode 25 formed on the surface of the p-type nitride semiconductor layer 24, a mounting substrate 4, having an n-side conductive portion 43 connected electrically with the n-type nitride semiconductor layer 22, and a p-side conductive portion 45 connected electrically to the p-type electrode 25, and an anisotropic conductive layer 6 including a resin adhesive layer 62 for bonding the mounting substrate 4 and the light-emitting diode 2 and conductive particles 64 dispersed into the resin adhesive layer 62, wherein at least the surface of the conductive particles 64 is formed of a metal material and the conductive particles 64 come into direct contact with the n-type nitride semiconductor 22, the n-side conductive portion 43, the p-type electrode 25 and the p-side conductive portion 45. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light emitting device including a light emitting element, and more particularly, to a light emitting device in which the light emitting element is flip-chip mounted.

  As a general semiconductor nitride element, there is a light emitting diode as shown in the cross-sectional view of FIG. 10, and an sapphire substrate 21 has an n-type nitride semiconductor layer 22, an active layer 23, a p-type nitride semiconductor layer 24, And the conductive oxide electrode 25 are laminated in this order, and a stepped portion 26 is formed in a part to expose the n-type nitride semiconductor layer 22. An n-side pad electrode 52 is formed on the exposed n-type nitride semiconductor layer 22, and a p-side pad electrode 54 is formed on the conductive oxide electrode 25.

  When the light emitting diode 2 is flip-chip mounted, bumps made of Au, solder, or the like are provided on the n-side and p-side pad electrodes 52, 54, and a conductive paste or anisotropic conductive paste is used for the electrodes of the mounting substrate. There is known a method of electrical connection (see, for example, Patent Document 1). As another electrical bonding method, Au bumps are formed on the n-side and p-side pad electrodes 52 and 54, and the electrodes of the mounting substrate are formed from Al, and the eutectic of Au bumps and Al is formed. Bonding is known depending on the composition (see, for example, Patent Document 2).

  In mounting by bump or eutectic, the conductive material protrudes from the pad electrode due to the bump protruding or the eutectic layer having a low melting point, and the p-type nitride semiconductor layer 24 and the n-type nitride semiconductor layer 22 are short-circuited. There is a fear. Therefore, like the light-emitting diode 2 in FIG. 10, the entire upper surface except the pad electrode is covered with a protective film 60 made of an insulating material, and the p-type nitride semiconductor layer 24 and the n-type nitride semiconductor layer 22 are short-circuited. Is preventing.

As another method for flip-chip mounting a light emitting diode, a method of connecting a light emitting diode and a substrate using an anisotropic conductive material is known (see, for example, Patent Document 3). An anisotropic conductive material is a material in which minute conductive particles are dispersed in a resin adhesive. By using this material, the light-emitting diode and the substrate are fixed by the adhesive, and the light-emitting diode is formed by the conductive particles. The electrical connection between the electrode and the electrode formed on the substrate is achieved at the same time.
JP-A-11-168235 Japanese Patent Laid-Open No. 11-354848 Japanese Patent Laid-Open No. 9-8360

  While it is desired to improve the luminance of the light emitting device, it is indispensable not only to improve the internal quantum efficiency of the light emitting diode but also to improve the external quantum efficiency, that is, the light extraction efficiency of the light emitting diode. Furthermore, it is important to reduce the light loss caused by mounting the light emitting diode on the mounting substrate and improve the light extraction efficiency as the light emitting device.

  When an n-side pad electrode made of Ti / Au or the like is directly formed on an n-type nitride semiconductor exposed from a step portion of a light emitting diode, the n-side pad electrode absorbs light inside the semiconductor with a high probability. To do. That is, light that is emitted from the active layer and propagates in the lateral direction while reflecting the inside of the semiconductor stacked body reaches the interface between the n-side pad electrode and the n-type semiconductor layer, and instead of being reflected, the n-side pad electrode To be absorbed. For this reason, there has been a problem that the light extraction efficiency to the outside is lowered due to the light absorption by the n-side pad electrode.

  A p-side electrode is formed on the entire surface of the p-side nitride semiconductor to spread the current to the p-side nitride semiconductor, and a p-side pad electrode is further formed thereon. The p-side electrode needs to be formed from a material that is in ohmic contact with the p-type nitride semiconductor. For example, a conductive oxide such as ITO or a Ni / Au film can be used. The p-side pad electrode needs to be formed from a material having good adhesion to the p-side electrode. For example, when the p-side electrode is a conductive oxide electrode, Rh or Au is used as the p-side pad electrode. Noble metals such as are preferred. However, since Rh and Au have a light reflectance that is not so high, there is a problem that light loss occurs at the interface between the p-side electrode and the p-side pad electrode.

  In view of the above, an object of the present invention is to provide a light-emitting device that improves light extraction efficiency and has good electrical performance.

  A first light emitting device according to the present invention includes (a) an n-type nitride semiconductor layer, a p-type nitride semiconductor layer stacked on the n-type nitride semiconductor layer, and a surface of the p-type nitride semiconductor layer. A light emitting device having a p-side electrode formed; (b) an n-side conductive portion electrically connected to the n-type nitride semiconductor layer; and a p-side conductive portion electrically connected to the p-side electrode. And (c) a resin adhesive layer that adheres the mounting substrate and the light emitting element, and an anisotropic conductive layer including conductive particles dispersed in the resin adhesive layer, The conductive particles are formed of a metal material at least on the surface, and are in direct contact with the n-type nitride semiconductor and the n-side conductive portion.

  In the first light emitting device of the present invention, the n-type nitride semiconductor of the light emitting element and the conductive particles of the anisotropic conductive layer are in direct contact, that is, the n-side pad electrode is not provided. The absorption of light caused by can be removed. Instead, the conductive particles in contact with the n-type nitride semiconductor layer absorb the light propagating in the lateral direction, but the contact area between the conductive particles and the n-type nitride semiconductor layer is different from that of the n-side pad electrode and n-type nitride. Since it is much smaller than the contact area with the physical semiconductor layer, the amount of absorbed light can be reduced as a whole. As a result, the light extraction efficiency of the light emitting device can be improved.

  A second light emitting device according to the present invention includes (a) an n-type nitride semiconductor layer, a p-type nitride semiconductor layer stacked on the n-type nitride semiconductor layer, and the p-type nitride semiconductor layer. A light emitting device having a p-side electrode formed on substantially the entire surface; (b) an n-side conductive portion electrically connected to the n-type nitride semiconductor layer; and electrically connected to the p-side electrode. A p-side conductive portion, an anisotropic conductive layer including (c) a resin adhesive layer that adheres the mounting substrate and the light emitting element, and conductive particles dispersed in the resin adhesive layer The conductive particles are in direct contact with the p-side electrode and the p-side conductive part.

  In the second light emitting device of the present invention, the conductive particles of the anisotropic conductive layer are connected to the electrodes of the mounting substrate instead of the p side pad electrodes of the light emitting elements, and the adhesion between the p side electrodes and the conductive particles is improved. Is held by the resin adhesive layer of the anisotropic conductive layer. Therefore, the conductive particles do not require adhesion with the p-side electrode, and the material of the conductive particles can be arbitrarily selected.

  The third light emitting device according to the present invention includes (a) an n-type nitride semiconductor layer, a p-type nitride semiconductor layer stacked on the n-type nitride semiconductor layer, and a p-type nitride semiconductor layer. A light emitting device having a p-side electrode formed on substantially the entire surface; (b) an n-side conductive portion electrically connected to the n-type nitride semiconductor layer; and electrically connected to the p-side electrode. A p-side conductive portion, an anisotropic conductive layer including (c) a resin adhesive layer that adheres the mounting substrate and the light emitting element, and conductive particles dispersed in the resin adhesive layer The conductive particles are formed of a metal material at least on the surface, and are in direct contact with the n-type nitride semiconductor and the n-side conductive portion, and are in direct contact with the p-side electrode and the p-side conductive portion. It is characterized by.

  Since the third light-emitting device of the present invention has the configurations of the first and second light-emitting devices, it is possible to eliminate a decrease in light extraction efficiency caused by the n-side and p-side pad electrodes. , The light extraction efficiency can be improved. Furthermore, since the step of forming the pad electrode can be omitted from the manufacturing process of the light emitting element, the manufacturing cost of the light emitting device can be reduced.

  In any of the first to third light emitting devices according to the present invention, it is possible to improve the light extraction efficiency of the light emitting device by suppressing a decrease in the external quantum efficiency of the light emitting element due to the pad electrode.

  In the second and third light-emitting devices, when the p-side electrode is translucent, a part of the light traveling from the inside of the light-emitting element toward the p-side electrode is transferred from the gap between the conductive particles to the mounting substrate. By forming a metal film having a high reflectivity on the surface of the mounting substrate, it becomes possible to reflect light more than a conventional p-side pad electrode. At this time, the material for forming the metal film does not need to have good adhesion to the p-side electrode, and a material having good light reflectance can be arbitrarily selected. Materials that reflect efficiently can be used. In addition, by using a highly reflective material for the conductive particles, light reaching the conductive particles can be reflected.

Embodiment 1
The light-emitting device 1 of the present invention shown in FIG. 1 includes a light-emitting diode 2, a mounting substrate 4 for flip-chip mounting the light-emitting diode 2, and an anisotropic conductive layer 6 for fixing the light-emitting diode 2 and the mounting substrate 4. It consists of and.

  The light emitting diode 2 is formed by sequentially stacking an n-type nitride semiconductor layer 22, an active layer 23, and a p-type nitride semiconductor layer 24 on a sapphire substrate 21, and further, the p-type nitride semiconductor layer 24 and the active layer are activated. A stepped portion 26 is formed by partially cutting or selectively growing the layer 23. Part of the n-type nitride semiconductor layer 22 is exposed at the step portion 26. Further, almost the entire surface of the p-type nitride semiconductor layer 24 is covered with a light-transmitting conductive oxide electrode 25 as a p-side electrode.

  In the light emitting diode 2, a voltage is applied between the conductive oxide electrode 25 and the n-type nitride semiconductor layer 22, and the n-type nitride semiconductor layer 22 passes from the p-type nitride semiconductor layer 24 through the active layer 23. It emits light by passing a current up to. Since light emission occurs in the active layer 23, all portions except the exposed portion 27 of the n-type nitride semiconductor layer 22 exposed from the stepped portion 26 from which the active layer 23 has been removed become light emitting regions.

  The step portion 26 of the light emitting diode 2 is formed in the center portion when viewed from the conductive oxide electrode 25 side, and the periphery thereof is surrounded by the p-type semiconductor layer 24. As another form, the step part 26 can also be formed in the corner | angular part or side part of the rectangular light-emitting diode 2, and as another form, it can also be made into the groove | channel shape which crosses the light-emitting diode 2. FIG. In any case, it is preferable that the area of the exposed portion 27 of the n-type nitride semiconductor layer 22 formed in the step portion 26 is made as small as possible to ensure a wide light emitting region.

  In the light emitting diode 2 used for the light emitting device 1 of the present invention, the light emitted from the active layer 23 is partially in the direction of the sapphire substrate 21 and partially in the direction opposite to the sapphire substrate 21, that is, a conductive oxide electrode. A part further proceeds in a direction parallel to the sapphire substrate while repeating multiple reflections in the direction of 25. The light traveling in the direction of the sapphire substrate 21 passes through the substrate 21 as it is and is extracted outside. The light traveling in the direction of the conductive oxide electrode 25 passes through the conductive oxide electrode, is reflected by the mounting substrate 4, returns to the inside of the light emitting diode 2, passes through the sapphire substrate 21, and is extracted. Then, the light traveling parallel to the sapphire substrate 21 propagates inside the nitride semiconductor layer and is taken out from the side surface of the light emitting diode 2.

  As described above, the light generated in the active layer 23 can be extracted to the outside in any direction, but the light extraction efficiency is different. For example, part of the light traveling in the direction of the light-transmitting conductive oxide electrode 25 passes through the conductive oxide electrode 25 and reaches the mounting substrate 4. At this time, if the reflectance of the mounting substrate 4 is low, a loss of light occurs, and the extraction efficiency of the light emitting device decreases. Therefore, in the present embodiment, the surface region of the mounting substrate 4 facing the conductive oxide electrode 25, that is, the p-side conductive portion 45 is formed from a metal material having a reflectance of 75% or more at the emission wavelength. As a result, the amount of light loss can be reduced as compared with the conventional p-side pad electrode, so that the light extraction efficiency of the light emitting device is improved. Examples of the metal material suitable for the p-side conductive portion 45 include Al, Ag, Pt, Rh, and alloys thereof as long as the emission wavelength of a light emitting diode made of a nitride semiconductor.

  The light traveling parallel to the sapphire substrate 21 is absorbed at the interface between the conductive particles 64 in the anisotropic conductive layer 6 and the n-type nitride semiconductor layer 22 while propagating through the nitride semiconductor layer. Happens. However, the area of the contact portion of the metal-n-type nitride semiconductor layer where light absorption occurs is the total area of a plurality of dot-like portions where the conductive particles 64 and the n-type nitride semiconductor layer 22 are in contact, and the n-side Compared with the conventional light emitting diode 2 provided with a pad electrode, it can be suppressed to a very small contact area. That is, the contact area of the metal-n-type nitride semiconductor layer in which light absorption occurs can be greatly reduced by omitting the n-side pad electrode and conducting by the anisotropic conductive layer 6, and as a result. , Light loss due to absorption can be greatly reduced.

In the present invention, the n-side pad electrode and the p-side pad electrode are omitted by using the anisotropic conductive layer 6 that can make ohmic contact with the n-type nitride semiconductor layer 22.
That is, conductive particles 64 made of a metal material capable of making ohmic contact with the n-type nitride semiconductor at least on the surface are dispersed in the anisotropic conductive layer 6, and the conductive particles 64 are the n-type nitride semiconductor 22. And in direct contact with the n-side conductive portion 43 and in direct contact with the p-side electrode 25 and the p-side conductive portion 45.

In the light emitting device 1, the ohmic contact with the n-type nitride semiconductor layer 22, which is conventionally achieved by the n-side pad electrode, is achieved by the conductive particles 64, so that the performance of the light emitting diode 22 is not degraded. The side pad electrode can be omitted. Thereby, in the light emitting device 1 of the present embodiment, the n-side pad electrode is omitted, and the contact area between the n-type nitride semiconductor 22 and the metal that contributes to the absorption amount of light propagating through the semiconductor stacked body in the lateral direction is greatly increased. The amount of light absorbed in the light emitting diode 2 is reduced.
Here, “ohmic contact” means that the contact resistance with the semiconductor to be connected is small.

  In addition, since the light emitting device 1 omits the p-side pad electrode that also functions as a light reflecting film, a light reflecting film that does not directly contact the p-side electrode can be prepared. This light reflection film is the p-side conductive portion 45 of the mounting substrate 4 and does not require adhesion to the p-side electrode, so that a metal material having a high reflectance can be arbitrarily selected. Since the light-emitting device 1 omits the n-side and p-side pad electrodes, the process of forming the pad electrodes can be omitted from the light-emitting diode manufacturing process, so that the manufacturing cost of the light-emitting device can be reduced.

  The light emitting device of the present invention eliminates the need for metal bumps and eutectic layers by connecting the light emitting diode 2 and the mounting substrate 4 with the anisotropic conductive film 6. Thereby, there is no possibility that the n-type nitride semiconductor layer 22 and the p-type nitride semiconductor layer 24 are short-circuited due to the protrusion of the metal bump or the eutectic layer, and the protective film 60 can be omitted. That is, in the conventional light emitting device using the light emitting diode, the connection surfaces of the n-type nitride semiconductor layer 22 and the p-type nitride semiconductor layer 24 to the mounting substrate are partially covered with the protective film 60. In the light-emitting device 1 of the invention, the connection surfaces of the n-type nitride semiconductor layer 22 and the p-type nitride semiconductor layer 24 with the mounting substrate are all exposed and are in contact with the anisotropic conductive layer 6. The connection surfaces of the n-type and p-type nitride semiconductor layers 22 and 24 are directly covered by the resin adhesive layer 62 of the anisotropic conductive layer 6. As a result, the light lost by the protective film 60 can be extracted to the outside, so that it is expected that the extraction efficiency of the light emitting device is improved. Further, since the upper surface of the conventional light emitting diode 2 is all insulated by the protective film 60 except for the upper surface portions of the n-side pad electrode and the p-side pad electrode, the conductive oxide electrode 25 and the substrate electrode are directly connected. I couldn't. In the light emitting device of this embodiment, by omitting the protective film 60, the p-side conductive portion 43 can be conducted over the entire surface of the conductive oxide electrode 25, so that the luminance distribution of the light emitting diode 2 is uniform. There is an effect. In addition, there is an advantage that the process required for forming the insulating layer 60 becomes unnecessary, and the cost of the light emitting device can be reduced.

  The mounting substrate 4 of the present invention has a unique form for flip-chip mounting the light emitting diode 2 with the anisotropic conductive layer 6, and the stepped portion of the light emitting diode 2 on the mounting surface 41 side of the mounting substrate 4. The protrusion part 46 corresponding to 26 recessed part shapes is provided. Since the step portion 26 is formed near the center when the light emitting diode 2 in FIG. 1 is viewed from the nitride semiconductor layer side, the protruding portion 46 of the mounting substrate 4 is also viewed from the mounting surface 41 side. It is formed near the center.

The mounting substrate 4 can be formed from a conductive material or an insulating material. Depending on the electrical properties of these mounting boards, the n-side conductive portion and the p-side conductive portion are different in form.
The light emitting device of FIG. 1 uses a conductive mounting substrate 4, and has an n-side conductive portion 43 made of a metal film directly on the upper surface 47 of the protruding portion 46 of the mounting substrate 4. And continuity. It is also possible to omit the metal film on the upper surface 47 of the protruding portion 46 and use the protruding portion 46 of the mounting substrate 4 as it is as the n-side conductive portion 43. The p-side conductive portion 45 is formed of a metal film laminated on the mounting surface 41 side of the mounting substrate 4 excluding the upper surface and side surfaces of the protrusion 46 via an insulating film 44. The n-side conductive portion 43 and the p-side conductive portion 45 are preferably formed from an Ag film, and can be formed at predetermined positions by plating.
The material for producing the conductive mounting substrate 4 is preferably a material that has good adhesion to the resin adhesive layer 62 of the anisotropic conductive layer 6 and that conducts well to the conductive particles 64. For example, a semiconductor such as Si, Cu / A composite material of metal such as W is preferable.

  On the other hand, FIGS. 2 to 4 show examples in the case where the insulating mounting substrate 4 is used. The insulating mounting substrate 4 can be formed from, for example, a glass epoxy laminated substrate, a liquid crystal polymer substrate, a polyimide resin substrate, a ceramic substrate such as AlN, or the like.

  2 includes a through hole 48 penetrating from the upper surface 47 of the protrusion 46 to the lower surface of the mounting substrate 4, and the through hole 48 is filled with a conductive material such as a metal paste. An n-side conductive portion 43 made of a metal film that is electrically connected to the conductive material in the through hole 48 is provided on the upper surface 47 of the protruding portion 46. The p-side conductive portion 45 is formed of a metal film formed on the mounting surface 41 side of the mounting substrate 4 excluding the protrusions 46. The n-side conductive portion 43 and the p-side conductive portion 45 are preferably formed from an Ag film, and can be formed at predetermined positions by vapor deposition, sputtering, plating, or printing. In particular, the plating method can satisfactorily form a film with uneven surfaces such as a step, can easily form a film having a complicated shape, and can be formed at a low cost in a short time even with a thick film. This is preferable because it is an excellent method.

The insulating mounting substrate 4 of FIG. 3 has a groove 49 that extends from the lower end of the protrusion 46 toward the edge of the mounting substrate 4, and the n-side conductive portion 43 extends from the upper surface 47 of the protrusion 46 along the side surface. It further extends to the edge of the mounting substrate 4 through the groove 49. The p-side conductive portion 45 is formed of a metal film formed on the mounting surface 41 side of the mounting substrate 4 excluding the protruding portion 46 and the groove portion 49. The n-side conductive portion 43 and the p-side conductive portion 45 are preferably formed from an Ag film, and can be formed at predetermined positions by vapor deposition, sputtering, plating, or printing. In particular, the plating method can satisfactorily form a film with uneven surfaces such as a step, can easily form a film having a complicated shape, and can be formed at a low cost in a short time even with a thick film. This is preferable because it is an excellent method.
Since the n-side conductive portion 43 in the groove 49 is positioned below the p-side conductive portion 45 on the surface of the mounting substrate 4, when the light emitting diode 2 and the mounting substrate 4 are mounted by the anisotropic conductive layer 6, The n-side conductive part 43 and the conductive oxide electrode 25 in the groove part 49 are insulated by the resin adhesive layer 62 filled in the groove part 49.

  In the insulating mounting substrate 4 of FIG. 4, a metal film constituting the n-side conductive portion 43 is formed on the entire mounting surface 41 of the mounting substrate 4. An insulating film 44 and a metal film for the p-side conductive portion 45 are sequentially stacked on the n-side conductive portion 43 excluding the upper surface and side surfaces of the protruding portion 46 of the mounting surface 41. The n-side conductive portion 43 and the p-side conductive portion 45 are preferably formed from an Ag film, and can be formed at predetermined positions by vapor deposition, sputtering, plating, or printing. In particular, the plating method can satisfactorily form a film with uneven surfaces such as a step, can easily form a film having a complicated shape, and can be formed at a low cost in a short time even with a thick film. This is preferable because it is an excellent method.

  5 differs from FIGS. 2 to 4 in that the protruding portion 46 is made of a metal material. The entire protruding portion 46 is the n-side conductive portion 43, and is formed integrally with or separately from the metal film formed on the entire mounting surface 41 of the mounting substrate 4 except the protruding portion 46. The protrusion 46 and the metal film on the mounting surface 41 are electrically connected. An insulating film 44 and a metal film for the p-side conductive portion 45 are sequentially stacked on the n-side conductive portion 43 excluding the upper surface and side surfaces of the protruding portion 46 of the mounting surface 41. The n-side conductive portion 43 is preferably formed from Cu, and the p-side conductive portion 45 is preferably formed from an Ag film. Each conductive portion is formed at a predetermined position by vapor deposition, sputtering, plating, or printing. be able to. In particular, the plating method can satisfactorily form a film with uneven surfaces such as a step, can easily form a film having a complicated shape, and can be formed at a low cost in a short time even with a thick film. This is preferable because it is an excellent method.

  As described above, any of the mounting substrates 4 of FIGS. 1 to 5 includes the n-side conductive portion 43 that is electrically connected to the exposed portion 27 of the n-type nitride semiconductor layer 22 exposed at the step portion 26 of the light emitting diode 2, and the conductive property. The p-side conductive portion 45 that is electrically connected to almost the entire surface of the oxide electrode 25 is provided, and when the light emitting diode 2 is mounted by the anisotropic conductive layer 6, the conductive oxide electrode 25 is not short-circuited. A substantially uniform current can flow over the entire surface. Accordingly, a light-emitting element with high reliability and less luminance unevenness can be obtained.

  The anisotropic conductive layer 6 of the present invention is composed of an insulating resin adhesive layer 62 and conductive particles 64 dispersed in the resin adhesive layer 62, and the conductive particles 64 are added to a paste-like resin adhesive. Can be formed from an anisotropic conductive paste in which a conductive particle 64 is dispersed, or an anisotropic conductive sheet in which conductive particles 64 are dispersed in a resin adhesive sheet formed into a sheet shape.

  The anisotropic conductive layer 6 is in a state in which the resin adhesive layer 61 is softened when the light emitting diode 2 is mounted, and when pressure is applied between the mounting substrate 4 and the light emitting diode 2, The resin adhesive layer 61 is pushed out from the gap between the upper surface 47 of the protrusion 46 and the exposed portion 27 of the n-type nitride semiconductor layer 22 of the light emitting diode 2, and the p-side conductive portion 45 of the mounting substrate 4 and the light emitting diode 2 The resin adhesive layer 61 is also pushed out from the gap with the conductive oxide electrode 25. Thereby, the conductive particles 64 dispersed in the resin adhesive layer 61 are sandwiched between the upper surface 47 of the mounting substrate 4 and the exposed portion 27 of the n-type nitride semiconductor layer 22 of the light emitting diode 2, Further, it is sandwiched between the p-side conductive portion 45 of the mounting substrate 4 and the conductive oxide electrode 25 of the light emitting diode 2. As a result, the n-side conductive portion 43 and the n-type nitride semiconductor layer 22 exposed at the exposed portion 27 are electrically connected, and the p-side conductive portion 45 and the conductive oxide electrode 25 are electrically connected.

  The anisotropic conductive layer 6 does not push out the resin adhesive layer 61 in a direction in which no pressure is applied during mounting, and therefore conduction through the conductive particles 64 does not occur. Therefore, no electrical contact is generated between the side surface of the protrusion 46 of the mounting substrate 4 and the side surface of the stepped portion 26. Further, in the light emitting device 1 of the present invention, the gap between the light emitting diode 2 and the mounting substrate 4 may be filled with the anisotropic conductive layer 6, and the side surface (n-type nitridation) of the stepped portion 26 of the light emitting diode 2. The particle diameter of the conductive particles 64 is between the physical semiconductor layer 22, the active layer 23, the p-type nitride semiconductor layer 24, and the conductive oxide electrode 25) and the protrusion 46 of the mounting substrate 4. If it is larger than this, since it is insulated by the resin adhesive layer 6, there is no possibility of short circuit.

  FIG. 6 shows a cross section of the conductive particles 64. As shown in FIG. 6A, the conductive particles 64 are preferably formed from particles of a material that is in ohmic contact with the n-type nitride semiconductor 22. As a material for forming the particles, it is preferable that the material is formed from any one of Ti, Zr, Hf, Cr, Mo, W, Al, or an alloy thereof because the ohmic contact with the n-type nitride semiconductor layer 22 is good. .

  In addition, as shown in FIG. 6B, the conductive particles 64 can have a two-layer structure having core particles 66 inside the particles. For the core particle 66, a resin material or a metal material can be used. In particular, it is preferable to use a metal material having a high light reflectance such as Al, Ag, Pt, Rh, Ni, or an alloy thereof. Here, the “core particle 66” is a substantially spherical or substantially oval spherical particle located inside the conductive particle 64, and is used as the conductive particle 64 by covering the surface with a metal. In the conductive particle 64 having a two-layer structure in which the core particle 66 is made of a metal material having a high light reflectance, the core particle 66 emits light that strikes the conductive particle 64 out of the light leaking into the anisotropic conductive layer 6. It can be expected that the light is efficiently reflected in the direction of the light emitting diode 2 and the extraction efficiency of the light emitting device is improved. Al is most preferably used for the core particle 66, and the ohmic characteristics of the conductive particle 64 and the n-type nitride semiconductor layer 22 are the best compared to the conductive particle 64 including the core particle 66 of another material. become.

When the surface layer 68 covering the core particles 66 of the conductive particles 64 is formed of Ti, Zr, Hf, Cr, Mo, W, Al, or an alloy thereof, like the conductive particles 64 without the core particles 66, n-type nitriding is performed. This is preferable because good ohmic contact can be made with the physical semiconductor layer 22 and the conductive oxide electrode 25.
Furthermore, the surface layer 68 can also be made into the laminated body which laminated | stacked the material of two or more layers. The outermost layer of the surface layer 68 is formed of a conductive material, and in particular, when formed of any one of Ti, Zr, Hf, Cr, Mo, W, Al, or an alloy thereof, n This is preferable because good ohmic contact can be made with the type nitride semiconductor layer 22 and the conductive oxide electrode 25. The layer other than the outermost layer of the surface layer 68 can include a layer formed of an arbitrary material. For example, a metal layer formed of an arbitrary metal material or a polymer formed by polymer coating the core material 66. Layers can be included. The conductive particles 64 including such a surface layer 68 can reliably conduct the light emitting diode 2 and the mounting substrate 4 by at least the outermost layer made of a conductive material.

  In addition, the light emitting device of the present embodiment can omit the two steps of forming the n-side and p-side pad electrodes and the protective film forming step in the manufacturing process of the light emitting diode to be used. Manufacturing costs can be reduced compared to a light emitting device using a light emitting diode.

Embodiment 2
The light emitting device 1 according to the second embodiment is the same as that of the first embodiment except that the light emitting diode 2 includes the p-side pad electrode 54 and does not include the n-side pad electrode 52.
As shown in FIG. 7, the p-side pad electrode 54 is formed on the upper surface of the p-side electrode 25 in the light-emitting diode 2 of the light-emitting device 1 of the present embodiment. The p-side pad electrode 54 is formed from a material having good adhesion to the p-side electrode 25. For example, when the p-side electrode 25 is formed of a metal film such as a Ni / Au film or a conductive oxide film such as ITO, ZnO, In ₃ O ₃ , SnO ₂ , or MgO, the p-side pad The electrode 54 can be formed from a Ti / Au laminated film, a Rh / Pt / Au laminated film, a Ti / Rh laminated film, or a W / Pt / Au laminated film.

  The p-side pad electrode 54 may be formed on a part of the surface of the p-side electrode 25 as shown in FIG. 7, but is preferably formed on the entire surface of the p-side electrode 25. The current can flow uniformly throughout. Further, when the p-side electrode 25 has translucency, part of the light emitted from the light emitting diode passes through the p-side electrode 25 and reaches the p-side pad electrode 54. Therefore, the material used for the p-side pad electrode 54 is preferably a material having a reflectivity as high as possible with respect to light of the light emitting wavelength of the light emitting diode, such as Rh, and can maintain good light extraction efficiency. .

  In the light emitting device 1 of the present embodiment, since the p-side pad electrode 54 is provided, the p-side conductive portion 45 and the p-side pad electrode 54 are electrically connected by the conductive particles 64 of the anisotropic conductive film 6. Similarly to the first embodiment, the n-side conductive portion 43 and the n-type nitride semiconductor layer 22 exposed at the exposed portion 27 are electrically connected by the conductive particles 64. Therefore, when the metal material on at least the surface side of the conductive particles 64 is selected from Ti, Zr, Hf, Cr, Mo, W, Al, or an alloy thereof, good ohmic contact with the n-type nitride semiconductor layer 22 This is preferable.

  In the present embodiment, since there is no n-side pad electrode 52 of the light emitting diode, absorption of light propagating in the lateral direction is reduced, and light extraction efficiency of the light emitting diode is improved. Thereby, a light emitting device with high luminance can be obtained.

Embodiment 3
The light-emitting device 1 according to the third embodiment is the same as that of the first embodiment except that the light-emitting diode 2 includes the n-side pad electrode 52 and does not include the p-side pad electrode 54.
As shown in FIG. 8, in the light emitting diode 2 of the light emitting device 1 of the present embodiment, an n-side pad electrode 52 is formed on the n-type nitride semiconductor 22 exposed from the step portion 26. The n-side pad electrode 52 is made of a material that can make ohmic contact with the n-type nitride semiconductor 22, and can be made of a material containing, for example, W, Pt, or Au.

  The p-side electrode 25 is made of a light-transmitting conductive oxide, and part of the light emitted from the light emitting diode passes through the p-side electrode 25 and reaches the p-side conductive portion 45. Therefore, when the material used for the p-side conductive portion 45 is formed of a metal material having a reflectance of 75% or more with respect to light having the emission wavelength of the light-emitting diode, the amount of light loss is reduced as compared with the conventional p-side pad electrode. Therefore, the light extraction efficiency of the light emitting device is improved. Examples of the metal material suitable for the p-side conductive portion 45 include Al, Ag, Pt, Rh, and alloys thereof as long as the emission wavelength of a light emitting diode made of a nitride semiconductor. Thus, in the light emitting device of this embodiment, the p-side conductive portion 45 is not in direct contact with the p-side electrode 25 and is not limited by the adhesiveness unlike the p-side pad electrode 54. A material having a good light reflectivity can be arbitrarily selected.

In the light emitting device 1 of the present embodiment, since the n-side pad electrode 52 is provided, the n-side conductive portion 43 and the n-side pad electrode 52 are electrically connected by the conductive particles 64 of the anisotropic conductive film 6. When the n-side pad electrode 52 is thicker than that shown in FIG. 8 and its surface is substantially flush with or slightly protruding from the p-side electrode 25, the mounting substrate 4 on which the convex portion 46 is not formed. Can also be used.
As in the first embodiment, the p-side conductive part 45 and the n-side electrode 25 are electrically connected by the conductive particles 64.

  In this embodiment, since there is no p-side pad electrode of the light emitting diode, light leaking from the light-transmitting p-side electrode 25 is not reflected by the p-side pad electrode. Therefore, instead of the p-side pad electrode, whose reflectivity cannot be increased due to adhesion with the p-side electrode 25, a material having high reflectance is used for the p-side conductive portion 45 formed on the mounting substrate 4. The reflectance of the light leaking from the p-side electrode 25 is increased, and the light extraction efficiency of the light emitting device can be improved.

The light emitting device of this embodiment will be described with reference to FIG.
In the light-emitting diode 2, a buffer layer (not shown) made of AlGaN and a non-doped GaN layer (not shown) are stacked on a sapphire substrate 21, and an n-type nitride semiconductor layer 22 is formed thereon as a Si-doped semiconductor layer 22. An n-type contact layer made of GaN, a superlattice n-type clad layer in which GaN layers and InGaN layers are alternately laminated are laminated, and further, a barrier layer made of undoped GaN and then made of InGaN. As a multi-quantum well structure active layer 23 and a p-type nitride semiconductor layer 24 formed by alternately and alternately stacking second barrier layers made of undoped GaN with well layers and first barrier layers made of InGaN. A p-type cladding layer of a superlattice in which Mg-doped AlGaN layers and Mg-doped InGaN layers are alternately stacked, and a p-type contour made of Mg-doped GaN Coat layer which are stacked in this order.

In a partial region of the n-type nitride semiconductor layer 22, the active layer 23 and the p-type nitride semiconductor layer 24 stacked on the n-type nitride semiconductor layer 22 are removed by etching to form a stepped portion 26, and the n-type nitride is further removed. A part of the semiconductor layer 22 itself in the thickness direction is also removed to form the n-type nitride semiconductor layer 22.
On the p-type nitride semiconductor layer 24, a conductive oxide electrode 25 made of ITO is formed on almost the entire surface.

The light emitting device 1 of Example 1 was manufactured by the following manufacturing method.
<Formation of Semiconductor Layers 22-24>
Using a MOVPE reactor on a 2-inch φ sapphire substrate 1, a buffer layer made of Al _0.1 Ga _0.9 N is 100 mm, a non-doped GaN layer is 1.5 μm, an n-type nitride semiconductor layer 22 is made of Si-doped GaN An n-type contact layer of 2.165 μm, a superlattice n-type clad layer in which a GaN layer (40 cm) and an InGaN layer (20 cm) are alternately stacked 10 times are 640 mm, and the first is an undoped GaN film having a thickness of 250 mm. And a well layer made of In _0.3 Ga _0.7 N with a thickness of 30 と, a first barrier layer made of In _0.02 Ga _0.98 N with a thickness of 100 と, and a thickness of A multi-quantum well structure active layer 23 (total thickness 1930 Å) formed by alternately stacking six second barrier layers made of 150 Å undoped GaN, p-type nitride half As the body layer 24, made Mg-doped Al _0.1 Ga _0.9 N layer (40 Å) and Mg-doped InGaN layer alternately superlattice formed by laminating 10 times the p-type cladding layer and (20 Å) 0.2 [mu] m, than Mg-doped GaN A p-type contact layer is grown in this order with a thickness of 0.5 μm to produce a wafer.

<Formation of the step part 26>
The obtained wafer is annealed in a reaction vessel at 600 ° C. in a nitrogen atmosphere to further reduce the resistance of the p-type cladding layer and the p-type contact layer.
After annealing, the wafer is taken out from the reaction vessel, a mask having a predetermined shape is formed on the surface of the uppermost p-type contact layer, and a step portion 26 is formed by etching from above the mask with an etching apparatus. Was exposed.

<Formation of Conductive Oxide Electrode 25>
After removing the mask, a wafer is placed in the sputtering apparatus, an oxide target made of a sintered body of In ₂ O ₃ and SnO ₂ is placed in the sputtering apparatus, and an ITO conductive oxide at an acceleration voltage of 200 kV. An electrode 25 was formed.

  The light emitting diode 2 is obtained by dividing the obtained wafer at a predetermined location. The light-emitting diode 2 used in the light-emitting device of the present invention does not include the n-side and p-side pad electrodes on the exposed portion 27 of the n-type nitride semiconductor layer 22 and the conductive oxide electrode 25.

<Formation of mounting substrate 4>
The mounting substrate 4 was formed into a shape having a protrusion 46 from Si, which is a conductive material. On the mounting substrate 4, an insulating film 44 and a p-side conductive portion 45 made of an Ag film were laminated in this order on the mounting surface 41 side of the mounting substrate 4 excluding the protrusions 46. An n-side conductive portion 43 made of an Ag film is formed on the upper surface 47 of the protrusion 46. Both the p-side conductive portion 45 and the n-side conductive portion 43 can be formed by plating.

<Mounting of light emitting diode 2>
Al particles having a central particle diameter of 5 μm were used as core particles 66, and a Ti surface layer 68 was coated on the surface thereof to a thickness of 100 mm to obtain conductive particles 64. A silicone resin was used as a resin adhesive, and 5 vol% of conductive particles 64 were added therein to obtain an anisotropic conductive paste.
This anisotropic conductive paste is applied to the mounting surface 41 of the mounting substrate 4 so as to have a thickness in the range of 10 μm to 20 μm, and then the light-emitting diode 2 is mounted on the mounting surface of the mounting substrate 4 with the conductive oxide electrode 25. It is placed on the mounting surface 41 of the mounting substrate 4 so as to face the surface 41 and so that the protruding portion 46 of the mounting substrate 4 fits into the stepped portion 26 of the light emitting diode 2. Then, pressure is applied in a direction in which the mounting substrate 4 and the light emitting diode 2 are brought close to each other, and the silicone resin is heat-cured in a state where conduction of a predetermined region between the mounting substrate 4 and the light emitting diode 2 is established. The light emitting device 1 was obtained.

  The light emitting device 1 obtained as described above had a driving voltage of 20 mA, a dominant wavelength of 470 nm, a forward voltage of 3.2 V, and a brightness of 15.5 mW.

(Comparative example)
The light emitting element of the comparative example shown in FIG. 9 will be described. Example 1 is the same as Example 1 except that a p-side pad electrode 54 is provided on the surface of the conductive oxide electrode 25 and an n-side pad electrode 52 is provided on the exposed surface of the n-type nitride semiconductor layer 22.

<Formation of n-side and p-side pad electrodes>
An n-side pad electrode 52 containing W, Pt, and Au for bonding was formed on the exposed portion 27 of the n-type nitride semiconductor layer 22 exposed by etching. On the other hand, on the conductive oxide electrode 25 formed on the surface of the p-type nitride semiconductor 24, the same member as the n-side pad electrode 52 containing W, Pt, and Au is formed in the same process as the n-side pad electrode 52. A p-side pad electrode 54 was formed.

  The light-emitting element 1 including the light-emitting diode 2 provided with the n-side and p-side pad electrodes 52 and 54 has a driving voltage of 20 mA, a dominant wavelength of 470 nm, a forward voltage of 3.1 V, and a brightness of 14 mW. The device was darker than the light emitting device of the invention. In addition, since the process of forming the n-side and p-side pad electrodes is included in the manufacture of the light-emitting diode, the cost is higher than that in Example 1.

  The light-emitting device of the present invention can be suitably used for various light sources such as a backlight light source, a display, illumination, and a vehicle lamp, and as the light-emitting element, not only a light-emitting diode but also a nitride semiconductor laser element is used. You can also. Furthermore, it is applicable not only to a light emitting device but also to a device including other semiconductor elements such as a light receiving device.

It is sectional drawing which shows the light-emitting device concerning Embodiment 1 of this invention. It is sectional drawing which shows the light-emitting device concerning Embodiment 1 of this invention. It is sectional drawing which shows the light-emitting device concerning Embodiment 1 of this invention. It is sectional drawing which shows the light-emitting device concerning Embodiment 1 of this invention. It is sectional drawing which shows the light-emitting device concerning Embodiment 1 of this invention. It is sectional drawing which shows the electrically-conductive particle in the anisotropic conductive layer used for the light-emitting device of this invention (A, B). It is sectional drawing which shows the light-emitting device concerning Embodiment 2 of this invention. It is sectional drawing which shows the light-emitting device concerning Embodiment 3 of this invention. It is sectional drawing which shows the light-emitting device of a comparative example. It is sectional drawing which shows the conventional light emitting diode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light-emitting device 2 Light emitting diode 4 Mounting board 6 Anisotropic conductive layer 22 N-type nitride semiconductor layer 24 P-type semiconductor layer 23 Step part 27 Lower part 43 N side conductive part 45 p side conductive part 46 Protrusion part 62 Resin adhesion layer 64 conductive particles

Claims (9)

a light emitting device having an n-type nitride semiconductor layer, a p-type nitride semiconductor layer stacked on the n-type nitride semiconductor layer, and a p-side electrode formed on the surface of the p-type nitride semiconductor layer;
A mounting substrate having an n-side conductive portion electrically connected to the n-type nitride semiconductor layer and a p-side conductive portion electrically connected to the p-side electrode;
A resin adhesive layer that adheres the mounting substrate and the light emitting element, and an anisotropic conductive layer that includes conductive particles dispersed in the resin adhesive layer,
The conductive particle is formed of a metal material at least on the surface, and is in direct contact with the n-type nitride semiconductor and the n-side conductive portion. Light emission having an n-type nitride semiconductor layer, a p-type nitride semiconductor layer stacked on the n-type nitride semiconductor layer, and a p-side electrode formed on almost the entire surface of the p-type nitride semiconductor layer Elements,
A mounting substrate having an n-side conductive portion electrically connected to the n-type nitride semiconductor layer and a p-side conductive portion electrically connected to the p-side electrode;
A resin adhesive layer that adheres the mounting substrate and the light emitting element, and an anisotropic conductive layer that includes conductive particles dispersed in the resin adhesive layer,
The light-emitting device, wherein the conductive particles are in direct contact with the p-side electrode and the p-side conductive part. Light emission having an n-type nitride semiconductor layer, a p-type nitride semiconductor layer stacked on the n-type nitride semiconductor layer, and a p-side electrode formed on almost the entire surface of the p-type nitride semiconductor layer Elements,
A mounting substrate having an n-side conductive portion electrically connected to the n-type nitride semiconductor layer and a p-side conductive portion electrically connected to the p-side electrode;
A resin adhesive layer that adheres the mounting substrate and the light emitting element, and an anisotropic conductive layer that includes conductive particles dispersed in the resin adhesive layer,
The conductive particles have at least a surface formed of a metal material, are in direct contact with the n-type nitride semiconductor and the n-side conductive portion, and are in direct contact with the p-side electrode and the p-side conductive portion. A light emitting device characterized.   4. The conductive particle according to claim 1, wherein at least a surface thereof is made of one selected from the group consisting of Ti, Zr, Hf, Cr, Mo, W, Al, and alloys thereof. The light emitting device according to item.   5. The light emitting device according to claim 4, wherein the conductive particles are made of a metal selected from the group consisting of Al, Ag, Pt, Rh, Ni, and alloys thereof.   6. The light emitting device according to claim 1, wherein at least a surface of the p-side conductive portion is made of a metal material having a reflectance of 75% or more at an emission wavelength of the light emitting element.   7. The light emitting device according to claim 6, wherein at least the surface of the p-side conductive portion is made of one selected from the group consisting of Al, Ag, Pt, Rh, and alloys thereof.   8. The connection surface of the n-type nitride semiconductor layer and the p-type nitride semiconductor layer with a mounting substrate is directly covered with a resin adhesive layer of the anisotropic conductive layer. The light emitting device according to any one of the above. The light-emitting element has a step portion formed so that a part of the n-type nitride semiconductor layer is exposed on the surface on the p-type nitride semiconductor layer side,
9. The light emitting device according to claim 1, wherein the mounting substrate includes a substrate protruding portion formed corresponding to the shape of the stepped portion of the light emitting element.

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