JP5512735B2 - Nitride semiconductor light emitting device and manufacturing method thereof - Google Patents

Description

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

  Conventionally, as a nitride semiconductor light emitting device, an n-type nitride semiconductor layer, a light emitting layer, a p-type nitride semiconductor layer, and the like are stacked on an insulating sapphire substrate, and a p-side electrode and A one-sided two-electrode structure in which an n-side electrode is arranged is known. However, such a single-sided two-electrode nitride semiconductor light-emitting device does not have both electrodes formed symmetrically on the upper and lower sides of the chip, so that the emission intensity is not uniform in the plane, and the p-side electrode or n-side There is a problem that light emission is concentrated on the electrode, and due to such a problem, it is difficult to increase the size of the chip, and it is easy to deteriorate due to aging. . Furthermore, since both electrodes are provided on one side surface, the ratio of the pad electrode to the chip surface area is large, and it is difficult to reduce the size of the chip.

  In order to solve the above problem, for example, in Patent Document 1, an n layer made of a gallium nitride based semiconductor, a gallium nitride based semiconductor active layer, and a p layer made of a gallium nitride based semiconductor are sequentially grown on a substrate, and the p A p-side ohmic electrode such as a Ni-Pt electrode and a first conductive adhesive layer made of Au-Sn are sequentially formed on the layer, and then a layer made of Au and a second conductive adhesive made of Au-Sn The upper and lower electrode structures obtained by joining the conductive substrate formed with the layers sequentially to the substrate by joining the second conductive adhesive layer and the first conductive adhesive layer, and separating the substrate. Nitride semiconductor light emitting devices have been proposed. However, the nitride semiconductor light emitting device described in the document has a problem that the light extraction efficiency is poor because the reflectance of the electrode is low.

  As an element structure for improving the light extraction efficiency, a distributed Bragg reflector (DBR) is used. For example, in Patent Document 2, after an n-type GaN layer, a multi-type quantum well (MQW) layer, and a p-type GaN layer are formed in this order on a sapphire substrate, Ni / Au or the like is formed on the p-type GaN layer. A method of manufacturing a semiconductor device is disclosed in which a p-type contact is formed using a p-type contact metal, a DBR layer made of indium tin oxide (ITO) is further formed thereon, and then a support substrate is formed by plating. . However, in such a structure, the light extraction efficiency is not sufficiently improved because the light absorption by the contact metal such as Ni / Au is large. Furthermore, although the light absorption of ITO is negligible when it is as thin as about 300 nm, when a thick film such as a multilayer film is formed using ITO to form a DBR layer, the light absorption is large. In addition, the improvement of the light extraction efficiency becomes a factor that becomes insufficient. In addition, the reference does not disclose a specific method for producing DBR using ITO, but it is difficult to increase the difference in refractive index if the same material as the high refractive index layer is used for the low refractive index layer. As a result, there is a problem that the reflectance of the DBR layer made of ITO cannot be increased.

Patent Document 3 discloses a nitridation having a DBR formed on a p-type contact layer and having a dielectric layer in which SiO ₂ layers and Ta ₂ O ₅ layers are alternately stacked and having a quarter wavelength. A physical resonator semiconductor structure is disclosed. A support substrate is attached on the DBR, and the growth substrate is removed. Then, the n-type layer and the active layer are removed by dry etching to expose the p-type layer, and a p-type electrode is formed on the exposed p-type layer. Form. In the case of the semiconductor structure described in the document, although the dielectric layer has a high reflectance, the dielectric layer is formed directly on the entire surface of the p-type contact layer, and thus the surface of the p-type contact layer opposite to the dielectric layer is formed. It has a structure in which a part is exposed and a p-type electrode must be formed on the part. However, as is well known in the art, the p-type nitride semiconductor layer has a very high resistance, and current cannot be diffused laterally from the portion where the electrode is formed. Even if the current is diffused, the resistance becomes very high. Moreover, this structure has to be a single-sided two-electrode structure, and has the same problem as described above.

  The vertical cavity surface emitting laser element disclosed in Patent Document 4 is composed of a Si-doped n-type AlAs / AlGaAs quarter-wavelength laminated semiconductor layer formed on a semiconductor substrate made of n-type GaAs. A DBR is provided. When a DBR having a structure similar to that of the DBR is to be realized by a nitride semiconductor light emitting device, a GaN substrate or a SiN substrate is usually used as the conductive substrate, but both are very expensive and inexpensive LEDs. In addition, when trying to construct a DBR from a multilayer structure of GaN and AlGaN that can be formed by epitaxial growth on the substrate, the refractive index difference is small, so it must be grown in a very multi-period, such as cracks Therefore, there is a problem that it is difficult to construct a DBR. Moreover, the quality of the active layer grown on such a DBR is poor, and the internal quantum efficiency is lowered.

  Further, in Patent Document 5, a DBR made of conductive ZnSSe and MgS / ZnCdSe superlattice is formed on a conductive GaAs substrate, and this DBR is fused to a nitride semiconductor on a sapphire substrate by wafer bonding. It is disclosed. However, when fusing without using an adhesive, the surface flatness of both wafers is indispensable, and wafer bonding is impossible if there are even slight protrusions in the wafer. In the case of an actual nitride semiconductor, dust or the like that has peeled off from the inside of the reactor during epitaxial growth often adheres to the surface of the epi-wafer, and it is difficult to eliminate one dust in the wafer.

  Further, although Patent Document 6 does not have an upper and lower electrode structure, in order to improve reflection, a mesh type DBR reflection layer is formed on a p layer of a flip chip type light emitting element, and the mesh type DBR reflection layer is A light emitting device in which a contact electrode is formed in a portion where it is not formed is disclosed. This mesh type DBR reflection layer is formed of a nitride semiconductor. As described above, a DBR made of a nitride semiconductor is difficult to manufacture, and even if it can be manufactured, since it has a high resistance, no current is injected into the DBR region, and the injection area becomes small. . As a result, the current density is increased, so that the light emission efficiency is lowered. Further, if the contact electrode portion has a low reflectance, the light extraction efficiency is also lowered. Furthermore, in this document, as the ohmic contact layer, Ag, Ni, Al, Ph, Pd, Ir, Ru, Mg, Zn, Pt, Au, and the like are mentioned, but all except Ag and Al are listed. Al having a low reflectivity and a high reflectivity does not become ohmic with the p-type semiconductor layer but has a high resistance. When Ag is used as the ohmic contact layer, electromigration occurs, and a short circuit occurs when migrating to the n side.

  As described above, a nitride semiconductor light emitting device that has been excellent in internal quantum efficiency, light extraction efficiency, drive voltage, and mass productivity has not been realized.

Japanese Patent No. 3893874 Special table 2007-536725 gazette JP 2003-234542 A JP 2004-119831 A Special table 2008-506259 gazette JP 2006-54420 A

  The present invention has been made in view of the above points, and an object of the present invention is a nitride semiconductor light emitting device that can adopt an upper and lower electrode structure, which is excellent in internal quantum efficiency, light extraction efficiency, and driving voltage, and is mass-productive. It is another object of the present invention to provide a nitride semiconductor light emitting device that is excellent in manufacturing method and a method for manufacturing the same.

The present invention includes the following.
[1] A reflective layer made of a dielectric, a transparent conductive layer, a p-type nitride semiconductor layer, a light emitting layer, and an n-type nitride semiconductor layer are included in this order,
The length in the direction perpendicular to the thickness direction of the transparent conductive layer is smaller than the length in the direction perpendicular to the thickness direction of the p-type nitride semiconductor layer,
The reflective layer made of the dielectric is in contact with both side surfaces of the transparent conductive layer and the reflective layer side surface of the transparent conductive layer made of the dielectric, and the transparent conductive layer of the p-type nitride semiconductor layer The nitride semiconductor light emitting element which is in contact with the surface which is a part of side surface, and is not in contact with the said transparent conductive layer.

  [2] The nitride semiconductor light-emitting element according to [1], including a support substrate, a reflective layer made of a dielectric, a transparent conductive layer, a p-type nitride semiconductor layer, a light-emitting layer, and an n-type nitride semiconductor layer in this order.

  [3] The nitride semiconductor light emitting element according to [1] or [2], wherein the transparent conductive layer is made of a conductive metal oxide.

  [4] The nitride semiconductor light-emitting element according to [1] or [2], wherein the transparent conductive layer is made of an n-type nitride semiconductor.

  [5] The reflective layer made of a dielectric has a laminated structure in which layers made of a dielectric having a high refractive index and layers made of a dielectric having a low refractive index are alternately laminated. ] The nitride semiconductor light-emitting device in any one of.

  [6] The nitride semiconductor according to any one of [1] to [5], wherein the reflective layer made of the dielectric has a reflectance of 80 to 100% with respect to the emitted light emitted from the light emitting layer. Light emitting element.

  [7] Of the surfaces of the nitride semiconductor layer made of the p-type nitride semiconductor layer, the light emitting layer, and the n-type nitride semiconductor layer, the surface on the side where the reflective layer made of the dielectric is formed is flat. The nitride semiconductor light-emitting device according to any one of [1] to [6].

  [8] Of the surface of the nitride semiconductor layer made of the p-type nitride semiconductor layer, the light emitting layer, and the n-type nitride semiconductor layer, the surface opposite to the side on which the reflective layer made of the dielectric is formed Is a nitride semiconductor light emitting device according to any one of [1] to [7], which has an uneven shape.

  [9] The nitride semiconductor light emitting element according to any one of [1] to [8], wherein the reflective layer made of the dielectric has a through-hole penetrating in the thickness direction in a region immediately below the transparent conductive layer.

  [10] The nitride semiconductor light emitting element according to any one of [1] to [9], wherein the p-type nitride semiconductor layer includes a current blocking region formed in contact with the transparent conductive layer.

  [11] The nitride semiconductor light-emitting element according to [10], wherein the through hole included in the reflective layer made of the dielectric is located immediately below the current blocking region.

  [12] A single-layer or multi-layer eutectic bonding layer made of a metal containing a eutectic bonding metal or an alloy containing the same is provided between the support substrate and the reflective layer made of the dielectric. [11] The nitride semiconductor light-emitting device according to any one of [11].

  [13] The nitride semiconductor light-emitting element according to [12], which has an adhesion layer between the reflective layer made of the dielectric and the eutectic bonding layer.

  [14] The nitride semiconductor light emitting device according to any one of [2] to [11], wherein the support substrate is a substrate made of a plated metal or alloy.

  [15] The nitride semiconductor light-emitting element according to any one of [1] to [14], wherein the reflective layer made of the dielectric has a thickness of 0.2 to 5 μm.

[16] The method for producing a nitride semiconductor light emitting device according to [2],
A step (A) of laminating an n-type nitride semiconductor layer, a light emitting layer, and a p-type nitride semiconductor layer in this order on a growth substrate;
Forming a transparent conductive layer on the surface of the p-type nitride semiconductor layer (B);
Forming a reflective layer made of a dielectric on the exposed surface of the obtained laminate (C);
A step (D) of laminating a support substrate;
Removing the growth substrate (E);
A step (F) of obtaining a plurality of nitride semiconductor light emitting devices by dividing the chip;
A method for manufacturing a nitride semiconductor light-emitting device comprising:

  [17] After the step (C), the method further includes a step (G) of forming a through-hole penetrating in the thickness direction in the reflective layer made of the dielectric and exposing a part of the transparent conductive layer. 16]. A method for producing a nitride semiconductor light-emitting device according to 16).

  [18] The method for manufacturing a nitride semiconductor light-emitting element according to [17], wherein in the step (G), the through-hole is formed by etching, and the transparent conductive layer serves as an etching stop layer.

  [19] A step of forming recesses at substantially regular intervals from the n-type nitride semiconductor layer side between the step (E) and the step (F) to expose the reflective layer made of the dielectric (H The manufacturing method of the nitride semiconductor light-emitting device according to any one of [16] to [18].

  [20] The nitride semiconductor light-emitting element according to any one of [16] to [19], further including a step (I) of forming irregularities on the surface of the n-type nitride semiconductor layer after the step (E). Manufacturing method.

  [21] The method for manufacturing a nitride semiconductor light-emitting element according to [19] or [20], wherein in the step (F), the chip dividing position is any position on the bottom surface of the recess.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the nitride semiconductor light-emitting device of the upper-lower electrode structure or the single-sided two-electrode structure which was excellent in internal quantum efficiency, light extraction efficiency, and drive voltage, and was excellent also in mass productivity.

It is a schematic sectional drawing which shows an example of the nitride semiconductor light-emitting device of this invention. FIG. 2 is a schematic cross-sectional view showing a method for manufacturing the nitride semiconductor light emitting device shown in FIG. 1. FIG. 2 is a schematic cross-sectional view showing a method for manufacturing the nitride semiconductor light emitting device shown in FIG. 1. FIG. 2 is a schematic cross-sectional view showing a method for manufacturing the nitride semiconductor light emitting device shown in FIG. 1. FIG. 2 is a schematic cross-sectional view showing a method for manufacturing the nitride semiconductor light emitting device shown in FIG. 1. FIG. 2 is a schematic cross-sectional view showing a method for manufacturing the nitride semiconductor light emitting device shown in FIG. 1. FIG. 2 is a schematic cross-sectional view showing a method for manufacturing the nitride semiconductor light emitting device shown in FIG. 1. It is a schematic sectional drawing which shows another example of the nitride semiconductor light-emitting device of this invention. 6 is a schematic cross-sectional view showing a nitride semiconductor light emitting device fabricated in Example 4. FIG.

Hereinafter, the method of the present invention will be described in detail with reference to embodiments.
<First Embodiment>
FIG. 1 is a schematic cross-sectional view showing an example of the nitride semiconductor light emitting device of the present invention. 1 includes a support substrate 101, a eutectic bonding layer 104 made of a second bonding layer 102 and a first bonding layer 103, a reflective layer 105 made of a dielectric, a transparent conductive layer 106, A p-type nitride semiconductor layer 109 composed of a p-type GaN layer 107 and a p-type AlGaN layer 108, a light emitting layer 110, and an n-type nitride semiconductor layer 111 composed of n-GaN are stacked in this order. A first electrode (n-side electrode) 112 is formed on the n-type nitride semiconductor layer 111, and a second electrode (p-side) is formed on the surface of the support substrate 101 opposite to the eutectic bonding layer 104 side. Electrode) 113 is formed, and has an upper and lower electrode structure.

  As described above, the nitride semiconductor light emitting device of the present invention is characterized in that a laminated structure of a reflective layer made of a dielectric and a transparent conductive layer is provided between the support substrate and the p-type nitride semiconductor layer. With such a configuration, current can be efficiently injected into the entire light emitting element by the transparent conductive layer, so that the resistance is low, and the light radiated from the light emitting layer to the support substrate side by the reflective layer made of a dielectric is efficiently used. Since it can reflect well, the light extraction efficiency can be improved. Further, when a DBR is produced by crystal growth, the quality of the active layer grown on the DBR is deteriorated and the internal quantum efficiency is lowered, but the DBR according to the present invention does not affect the crystal. That is, according to the present invention, the internal quantum efficiency can be increased because crystal growth is possible with a layer structure and growth conditions that improve crystal quality. Furthermore, since the transparent conductive layer is formed on almost the entire surface of the p layer, as in Patent Document 3, a high resistance is obtained as in the case where a part of the p layer is exposed and an electrode is formed on a part thereof. In other words, the drive voltage can be reduced.

The reflective layer 105 is a layer made of a dielectric material and is not particularly limited as long as it has a good reflectance with respect to the radiated light emitted from the light emitting layer 110. Since a reflective layer having a high reflectivity is easily obtained, it is preferable to have a laminated structure in which layers made of a dielectric material having a high refractive index and layers made of a dielectric material having a low refractive index are alternately laminated. The dielectric having a high refractive index is a dielectric having a refractive index of about 1.7 to 3, preferably about 2 to 3, for example, SiN (refractive index) at an emission wavelength of emitted light of 450 nm. 2.1), TiO ₂ (refractive index 2.4-3), GaN (refractive index 2.4), Ta ₂ O ₃ and Ta ₂ O ₅ (refractive index 2.2-2.3), Nb ₂ O ₅ (refractive index 2.3), ZrO, ZrO ₂ , CeO, Al ₂ O ₃ , CeF _{3 and the} like. The dielectric having a low refractive index is a dielectric having a refractive index of about 1 to 2, preferably about 1 to 1.8 at an emission wavelength of emitted light of 450 nm. For example, SiO ₂ (Refractive index 1.47), MgF ₂ (refractive index 1.38), CaF ₂ (refractive index 1.43), Al ₂ O ₃ , CeF _{3 and the} like. The intermediate refractive index Al ₂ O ₃ or CeF ₃ can be used for a layer having a high refractive index and a layer having a low refractive index. When the reflective layer has a laminated structure in which such a layer made of a dielectric material having a high refractive index and a layer made of a dielectric material having a low refractive index are alternately laminated, a layer made of a dielectric material having a high refractive index The dielectric material is selected so that the refractive index of the layer is larger than the refractive index of the layer made of a dielectric material having a low refractive index.

  When one period of the dielectric layer having a high refractive index and one dielectric layer having a low refractive index is defined as one period, the number of periods of the laminated structure included in the reflective layer is not particularly limited. From the viewpoint of improving the refractive index, the layer on the support substrate 101 side which is the lowest layer in FIG. 1 is a layer made of a dielectric having a high refractive index, and the layer on the transparent conductive layer 106 side which is the uppermost layer is a low refractive index. It is preferable to use a layer made of a dielectric having

  The thickness of the dielectric layer having a high refractive index and the dielectric layer having a low refractive index constituting the reflective layer 105 has better reflection characteristics with respect to light incident on the reflective layer 105 in the vertical direction. Therefore, the wavelength [nm] of the light incident on the reflective layer (the wavelength [nm] of the light emitted from the light emitting layer) × (the refractive index of the layer) / 4 [nm], respectively. It is preferable. For example, when the layer made of a dielectric having a high refractive index is made of SiN and the wavelength of light emitted from the light emitting layer is 450 nm, the thickness of the layer made of SiN is preferably about 53 nm.

  In addition, in order to obtain a good reflectance even for light incident on the reflective layer 105 in an oblique direction, the multilayer structure of the reflective layer 105 is a multilayer having a thickness calculated from the above formula. In addition to the structure portion, a stacked structure portion including a layer made of a dielectric material having a high refractive index and a layer made of a dielectric material having a low refractive index may be provided.

  The total thickness of the reflective layer 105 depends on the number of periods of the laminated structure and is not particularly limited, but may be, for example, 0.2 to 5 nm. In the method for manufacturing a nitride semiconductor light emitting device of the present invention to be described later, a step of forming a recess reaching the reflective layer 105 from the n-type nitride semiconductor layer 111 side by etching (for example, dry etching) is preferably provided. In this case, it is preferable that the reflective layer 105 functions as an etching stop layer, and for that purpose, the thickness of the reflective layer 105 is preferably 0.2 to 5 nm.

  The reflective layer 105 preferably has a reflectance of 80 to 100%, preferably 90 to 100%, with respect to the radiation emitted from the light emitting layer 110.

The transparent conductive layer 106 is a layer laminated in contact with the reflective layer 105 made of the dielectric, and a material having good conductivity is preferably used. Examples of such a conductive material include ITO (indium tin oxide), IZO (indium zinc oxide), In ₂ O ₃ (indium oxide), and the like. Alternatively, an n-type nitride semiconductor (for example, n-type Al _x In _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1)) may be used. The use of an n-type nitride semiconductor is advantageous in that the film can be continuously formed in MOCVD and the transmittance with respect to light having a wavelength of 450 nm is higher than that of ITO or the like. The thickness of the transparent conductive layer 106 is not particularly limited, but may be, for example, 50 to 1000 nm, and is preferably 80 to 500 nm from the viewpoint of improving transmittance.

  Here, in the present embodiment, the lateral length of the transparent conductive layer 106 (the length in the direction perpendicular to the thickness direction) is more specifically set to the p-type nitride semiconductor layer 109 stacked thereon. Is smaller than the lateral length of the p-type GaN layer 107 (the length in the direction perpendicular to the thickness direction), and the both sides of the transparent conductive layer 106 and the surface of the reflective layer 105 are covered with the reflective layer 105. . At this time, the reflective layer 105 is formed so as to be in contact with the surface of the p-type GaN layer 107 on the transparent conductive layer 106 side that is not in contact with the transparent conductive layer 106. Such a configuration is preferable because the end of the transparent conductive layer and the PN junction can be separated from each other and leakage can be prevented. In addition, a reflective film made of a dielectric can be used as an etching stop layer at the time of dry etching for forming a recess for dividing a chip, which is preferable.

  The nitride semiconductor light emitting device of this embodiment has a current blocking region 114 so that the p-type GaN layer 107 is in contact with the transparent conductive layer 106. By forming the current blocking region and arranging the first electrode 112 at a position immediately above the current blocking region, it is possible to prevent a decrease in light extraction efficiency.

  Further, the reflective layer 105 of the present embodiment has a through-hole 115 that penetrates in the thickness direction of the reflective layer 105 at a portion located directly below the transparent conductive layer 106. A conductive material constituting the first bonding layer 103 disposed below the reflective layer 105 is embedded in the through-hole 115. The through hole 115 has a ring shape when the nitride semiconductor light emitting element is viewed from above. The ring-shaped through hole 115 is preferably formed so as to be within the region of the current blocking region 114 when the nitride semiconductor light emitting element is viewed from above. It is preferable that such a ring-shaped through-hole be provided in the reflective layer because the transparent conductive layer 106 and the first bonding layer 103 can be electrically connected with low resistance. The ring width (W1 shown in FIG. 1) is not particularly limited. For example, the ring width can be set to 0.5 to 50 μm so as not to protrude from the current blocking region and to form with a high yield. The thickness is preferably 1 to 30 μm.

  In the nitride semiconductor light emitting device of the present invention, the current blocking region and the through hole may be omitted, but are preferably provided from the viewpoint of improving light extraction efficiency and reducing resistance.

  As the structures and constituent materials of the p-type nitride semiconductor layer 109, the light emitting layer 110, and the n-type nitride semiconductor layer 111, conventionally known materials can be applied. In order to improve the light extraction efficiency to the outside, the surface of the n-type nitride semiconductor layer 111 is preferably provided with an uneven shape as shown in FIG. The light emitting layer 110 can have, for example, a multiple quantum well structure in which well layers and barrier layers having different band gaps are alternately stacked.

  The surface of the nitride semiconductor layer composed of the p-type nitride semiconductor layer 109, the light emitting layer 110, and the n-type nitride semiconductor layer 111 opposite to the side on which the dielectric reflective layer 105 is formed (n-type nitride semiconductor layer) 111 is preferably a concave-convex shape. Thereby, the light extraction efficiency can be improved. Of the surface of the nitride semiconductor layer, the surface on the side where the reflective layer 105 made of dielectric is formed (the surface on the side where the reflective layer 105 made of dielectric in the p-type nitride semiconductor layer 109 is formed). Is preferably flat from the viewpoint of improving the reflectance.

  As the support substrate 101, for example, Si, GaAs, SiC, GaP, metal, alloy, or the like can be used.

  Next, a method for manufacturing the nitride semiconductor light emitting device shown in FIG. 1 will be described with reference to FIGS. In the following description and FIGS. 2 to 7, the case where three light emitting elements are obtained from one wafer will be described. However, in the present invention, the number of light emitting elements obtained from one wafer is not particularly limited. .

  First, on a growth substrate 201 such as a sapphire substrate, SiC substrate, or GaN substrate, a buffer layer 202 made of GaN, an n-type nitride semiconductor layer 111 made of an n-type GaN layer, a light emitting layer 110, and a p-type AlGaN layer 108. Then, a p-type nitride semiconductor layer 109 made of the p-type GaN layer 107 is grown in this order (step (A), see FIG. 2). As a growth method, a metal organic chemical vapor deposition method (MOCVD method) or the like can be used. Next, in order to form the current blocking region 114, for example, a photoresist mask in which circular openings are formed at a constant pitch is formed on the p-type GaN layer 107. Next, the p-type GaN layer 107 exposed in the opening of the photoresist mask is increased in resistance by plasma irradiation or the like to form a current blocking region 114.

  Next, after removing the photoresist mask, a layer constituting the transparent conductive layer is laminated on the entire surface of the p-type GaN layer 107. When the transparent conductive layer is made of ITO or the like, this layer can be formed by sputtering or the like. When the transparent conductive layer is made of an n-type nitride semiconductor or the like, this layer can be formed by MOCVD or the like. Next, three photoresist masks having a certain shape (for example, a square or a rectangle) are formed at a certain pitch. The photoresist mask is preferably arranged so that the center position of the photoresist mask and the center position of the current blocking region 114 substantially overlap. Next, etching is performed to obtain a stacked body having the structure shown in FIG. 2 in which the transparent conductive layer 106 is formed at regular intervals (step (B)).

  Next, after the photoresist mask is removed, for example, the reflective layer 105 having a multilayer structure of a dielectric layer having a high refractive index and a dielectric layer having a low refractive index is used by MOCVD or the like. Then, it is formed over the entire exposed surface of the laminate (see step (C), FIG. 3). Next, in order to form the ring-shaped through-hole 115, a photoresist mask having a ring-shaped opening is manufactured. The photoresist mask is preferably aligned such that its ring-shaped opening is within the current blocking region 114 region. Next, the reflective layer in the opening is removed by etching, and the transparent conductive layer 106 is exposed to obtain the laminate shown in FIG. 3 (step (G)). At this time, when ITO, IZO, GaN, or the like is used as the transparent conductive layer 106, the transparent conductive layer 106 can function as an etching stop layer. In the case where the ring-shaped through hole is not provided, the step (G) is unnecessary.

  Next, after removing the photoresist mask, the first bonding layer 103 is formed on the entire exposed surface. The first bonding layer 103 is provided in order to stack a support substrate on the stacked body by eutectic bonding. Examples of the eutectic bonding metal constituting the first bonding layer 103 include Au, AuSn, AuSi, and AuGe, and an alloy containing any of these may be used. In order to improve the adhesive strength between the first bonding layer 103 and the reflective layer 105, an adhesion layer (not shown) may be formed on the surface of the reflective layer 105 before the formation of the first bonding layer 103. . The adhesion layer may have a conventionally known configuration, for example, a laminated structure of a Ti layer and a Pt layer.

  Next, the support substrate 101 is prepared, and the second bonding layer 102 is formed on the surface thereof (see FIG. 4). The eutectic bonding metal constituting the second bonding layer 102 is not particularly limited as long as it can be eutectic bonded to the eutectic bonding metal constituting the first bonding layer 103. Next, the stacked body including the growth substrate 201 and the stacked body including the support substrate 101 are bonded together by eutectic bonding of the first bonding layer 103 and the second bonding layer 102, and the growth substrate 201 is bonded. The support substrate 101 is laminated on the laminated body having (Step (D)). The eutectic bonding layer 104 in FIG. 1 includes a first bonding layer 103 and a second bonding layer 102.

  Next, the growth substrate 201 is removed (step (E), see FIG. 5). When the growth substrate 201 is a sapphire substrate, a SiC substrate, a GaN substrate, or the like, laser peeling using the laser beam 203 can be preferably adopted for the peeling removal of the growth substrate 201.

  In the subsequent process, three photoresist masks are formed at a constant pitch on the exposed n-type nitride semiconductor layer 111. The photoresist mask is preferably arranged so that the center position of the photoresist mask and the center position of the transparent conductive layer 106 substantially overlap. Next, a recess 601 is formed from the n-type nitride semiconductor layer 111 side by dry etching or the like to expose the reflective layer (step (H), see FIG. 6). Such a recess 601 is preferably formed in order to facilitate chip division.

  Next, after removing the photoresist mask, irregularities are formed on the exposed surface of the n-type nitride semiconductor layer 111. Such surface unevenness is not necessarily formed, but it is preferable to form surface unevenness in order to improve external light extraction efficiency. Next, the first electrode 112 is formed on the surface unevenness, and the second electrode 113 is formed on the back surface of the support substrate 101 (see FIG. 7). It is preferable that the first electrode 112 be formed so as to be within the region of the current blocking region 114 because a decrease in light extraction efficiency can be prevented. Finally, by dividing the chip, three nitride semiconductor light emitting devices are obtained (step (F), see FIG. 7). As the chip dividing position, any position (for example, the position of the dotted line shown in FIG. 7) on the bottom surface of the recess 601 (that is, the exposed surface of the reflective layer 105) is preferably employed.

<Second Embodiment>
FIG. 8 is a schematic cross-sectional view showing another example of the nitride semiconductor light emitting device of the present invention. The nitride semiconductor light emitting device shown in FIG. 8 has a plating base layer 803 and a plating layer 801 instead of the eutectic bonding layer 104, the support substrate 101, and the second electrode 113 of the nitride semiconductor light emitting device shown in FIG. Is different from the nitride semiconductor light emitting device of FIG. That is, the nitride semiconductor light emitting device shown in FIG. 8 includes a plating layer 801, a plating base layer 803, a reflective layer 805 made of a dielectric, a transparent conductive layer 806, a p-type GaN layer 807, and a p-type AlGaN layer 808. It has a stacked structure in which a type nitride semiconductor layer 809, a light emitting layer 810, and an n-type nitride semiconductor layer 811 made of n-GaN are stacked in this order. A first electrode (n-side electrode) 812 is formed on the n-type nitride semiconductor layer 811. In the present embodiment, the plating layer 811 plays both a role as a support substrate and a role as a p-side electrode. Therefore, the nitride semiconductor light emitting device of FIG. 8 also has an upper and lower electrode structure. A current blocking region 814 is formed in the p-type GaN layer 807 as in the first embodiment. Also in the nitride semiconductor light emitting device having such a configuration, the same effect as that of the first embodiment can be obtained.

  Also in the present embodiment, the reflective layer 805 has a ring-shaped through hole 815, and the positional relationship among the through hole 815, the current blocking region 814, and the first electrode 812 is the same as in the first embodiment. is there. In the case of this embodiment, the inside of the through-hole 815 is embedded with a conductive material constituting the plating base layer 803.

  In the present embodiment, conventionally known materials can be used as the material constituting the plating base layer 803, and examples thereof include Au, Ni, Cu, Sn, Pd, Ti, and W. The thickness of the plating base layer 803 is not particularly limited as long as the thickness is equal to or larger than the ring-shaped through-hole 815 is filled.

  For example, Cu, Ni, Au, and an alloy containing any of these metals can be used for the plating layer 801, and the thickness thereof can be, for example, 30 to 500 μm, preferably 70 to 200 μm. By using a substrate formed by such a plating method as a support substrate, the support substrate can be formed with high yield even when a light-emitting element with a large area is manufactured. Compared with the method in which two bonding layers are formed, and these bonding layers are bonded by eutectic bonding and the supporting substrate is laminated, the plating layer is plated on the reflective layer 805 when the plating layer is used as the supporting substrate. By forming the base layer 803 and forming the plating layer 801 thereon, the support substrate can be directly laminated, which is advantageous in manufacturing.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
A nitride semiconductor light emitting device having the structure shown in FIG. 1 was fabricated by the following method. Hereinafter, a manufacturing method will be described with reference to FIGS. First, on a growth substrate 201 made of sapphire, six cycles of a buffer layer 202 made of GaN, an n-type nitride semiconductor layer 111 made of an n-type GaN layer having a thickness of 4 μm, a barrier layer made of GaN, and a well layer made of InGaN. The light emitting layer 110 (thickness 100 nm) which is an MQW layer having the structure, the p-type nitride semiconductor layer 109 consisting of the p-type AlGaN layer 108 (thickness 20 nm) and the p-type GaN layer 107 (thickness 80 nm) in this order are MOCVD methods. (See step (A), FIG. 2). Next, in order to form the current blocking region 114, a photoresist mask in which circular openings having a diameter of 90 μm were formed at a pitch of 400 μm was formed on the p-type GaN layer 107. Next, plasma irradiation was performed to increase the resistance of the p-type GaN layer 107 exposed in the opening of the photoresist mask, and the current blocking region 114 was formed.

  Next, after removing the photoresist mask, ITO was formed to a thickness of 100 nm on the entire surface of the p-type GaN layer 107 by sputtering. Next, a 320 μm × 320 μm photoresist mask was formed at a pitch of 400 μm so that the center position of the photoresist mask and the center position of the current blocking region 114 substantially overlap each other. Next, ITO was etched using hydrochloric acid-containing etching to obtain a laminate having the structure shown in FIG. 2 in which the transparent conductive layer 106 was formed (step (B)).

Next, after removing the photoresist mask, the p-type nitride semiconductor layer 109 was activated, the resistance of ITO was lowered, and the transparency was made simultaneously by alloying in an atmosphere containing oxygen. Next, as the reflective layer 105, the SiO ₂ layer (thickness 76 nm) / SiN layer (thickness 53 nm) was set as one cycle, and a total of 7 cycles were laminated by the MOCVD method (step (C), see FIG. 3). Note that the first layer to be laminated was an SiO ₂ layer, and the last layer was an SiN layer. Next, in order to form the ring-shaped through-hole 115, a photoresist mask in which ring-shaped openings (ring outer diameter 70 μm, ring width (opening width) 3 μm) are formed at a pitch of 400 μm is used as a reflective layer. 105 was formed. At this time, the photoresist mask was aligned so that the ring-shaped opening was within the region of the current blocking region 114 formed by the region having a diameter of 90 μm. Next, by dry etching using CHF ₃ , SiO ₂ and SiN in the ring-shaped opening were removed, and the transparent conductive layer 106 made of ITO was exposed to obtain the laminate shown in FIG. (Process (G)). Here, since the selection ratio of SiO ₂ and SiN to ITO in dry etching using CHF ₃ is 5 or more, ITO functioned as a good etching stop layer.

  Next, after removing the photoresist mask, 200 nm of Ti and 100 nm of Pt were formed as the adhesion layer, and then Au (thickness 1000 nm) was formed as the first bonding layer 103. Next, a Si substrate was prepared as the support substrate 101, and Ti 200 nm, Pt 100 nm, Au 500 nm, and AuSn 3 μm were formed in this order as the second bonding layer 102 on the surface (see FIG. 4). Next, the stacked body including the growth substrate 201 and the stacked body including the support substrate 101 are eutectic bonded to the first bonding layer 103 and the second bonding layer 102 by thermocompression bonding. The support substrate 101 was stacked on the stack including the substrate 201 (step (D)).

  Next, the growth substrate 201 was peeled off by irradiating laser light from the back surface of the growth substrate 201 (step (E), see FIG. 5), and then the damaged layer on the peeled surface was removed by dry etching.

  Next, a 340 μm × 340 μm photoresist mask is applied on the exposed n-type nitride semiconductor layer 111 at a pitch of 400 μm so that the center position of the photoresist mask and the center position of the transparent conductive layer 106 substantially overlap. Formed. Next, a recess 601 was formed from the n-type nitride semiconductor layer 111 side by dry etching to expose the reflective layer 105 (step (H), see FIG. 6).

  Next, after removing the photoresist mask, hexagonal pyramid uneven shapes were formed on the exposed surface of the n-type nitride semiconductor layer 111 using KOH. Next, a first electrode 112 made of Ti / Au was formed on the surface irregularities using a photoresist mask by lift-off. At this time, the first electrode 112 was formed so as to be within the region of the current blocking region 114. In addition, even if a slight misalignment occurs, the diameter of the first electrode 112 is 70 μm so that the first electrode 112 is within the region of the current blocking region 114 formed from the region having a diameter of 90 μm. It was. Next, a second electrode 113 made of Ti / Au was formed on the back side of the support substrate 101 (see FIG. 7). Finally, a nitride semiconductor light emitting device was obtained by dividing the chip at the position of the dotted line shown in FIG. 7 (see step (F), FIG. 7).

  The light output of the nitride semiconductor light emitting device of this example obtained as described above was 25 mW, and the drive voltage was 3.2V.

<Example 2>
As the reflective layer 105, a total of 3 periods including one period of SiO ₂ layer (thickness 102 nm) / SiN layer (thickness 72 nm), and then a total of 7 periods including one period of SiO ₂ layer (thickness 76 nm) / SiN layer (thickness 53 nm). A nitride semiconductor light emitting device was obtained in the same manner as in Example 1 except for the formation. In the obtained nitride semiconductor light emitting device, good reflectivity was exhibited even for light incident on the reflective layer 105 in an oblique direction, and the light extraction efficiency was further improved. The light output of the nitride semiconductor light emitting device of this example was 26 mW, and the drive voltage was 3.2V.

<Example 3>
The process up to the step of forming the ring-shaped through hole 815 in the reflective layer 805 is performed in the same manner as in Example 1, and then 2 μm of Au is formed as the plating base layer 803, and then the thickness of Cu is formed by electrolytic plating. An 80 μm plating layer 801 was formed. Subsequent steps were performed in the same manner as in Example 1 to obtain the nitride semiconductor light emitting device shown in FIG. The light output of the nitride semiconductor light emitting device of this example was 25 mW, and the drive voltage was 3.2V.

<Example 4>
First, referring to FIG. 9, a sapphire substrate having an uneven surface was prepared as a growth substrate 901. The period of the unevenness is 5 μm. Moreover, the convex part in this unevenness | corrugation has the shape which cut the upper part of the cone whose bottom face is circular, or a shape like a convex lens, The cross section is a trapezoid or a semicircle or a semi-elliptical shape. . The diameter of the convex portion (the bottom of the cross-sectional shape) is 2.5 μm. Note that the shape and size of the protrusions are not limited to this example, but the sapphire substrate surface has such a shape, so that the interface with the nitride semiconductor layer formed thereon has an uneven shape. Therefore, the light extraction efficiency can be improved. Further, lateral growth is promoted, threading dislocations can be suppressed, and a light-emitting element with high internal quantum efficiency can be created.

  Next, on the uneven surface of the sapphire substrate, a buffer layer (not shown) made of GaN, an n-type nitride semiconductor layer 902 made of an n-type GaN layer having a thickness of 4 μm, a barrier layer made of GaN, and a well made of InGaN. A light emitting layer 903 (thickness 100 nm), which is an MQW layer having a six-period structure of layers, a p-type nitride semiconductor layer 906 comprising a p-type AlGaN layer 904 (thickness 20 nm) and a p-type GaN layer 905 (thickness 80 nm) are arranged in this order. Then, it was grown by the MOCVD method.

  Next, ITO was formed to a thickness of 200 nm on the entire surface of the p-type GaN layer 905 by sputtering. Next, a photoresist mask of approximately 230 μm × 480 μm was formed at a pitch of 250 μm × 500 μm. Next, ITO was etched using etching containing hydrochloric acid to form a transparent conductive layer 907.

  Next, after the photoresist mask was removed, the p-type nitride semiconductor layer 906 was activated, the resistance of ITO was lowered, and transparency was simultaneously performed by alloying in an atmosphere containing oxygen. Next, an approximately 240 μm × 490 μm photoresist mask for mesa etching is formed at a pitch of 250 μm × 500 μm, and then dry etching is performed to form a p-type GaN layer 905, a p-type AlGaN layer 904, a light emitting layer 903, and an n-type GaN. A part of the n-type nitride semiconductor layer 902 made of the layer was etched to expose the n-type GaN layer.

Next, an SiO ₂ layer having a thickness of 200 nm was formed as the reflective layer 908. This reduces the total reflection critical angle. Next, four periods of SiO ₂ with a thickness of 102 nm and SiN with a thickness of 72 nm were formed so that the reflectance increased in the direction of about 25 °. Next, seven periods of SiO ₂ with a thickness of 76 nm and SiN with a thickness of 53 nm were formed so that the reflectance was maximized in the vertical direction. By forming the reflective layer 908 made of a dielectric with such a configuration, first, the light totally reflected by the influence of the critical angle is increased, and then the light within the critical angle is caused by interference in an oblique 25 ° direction. By combining the periodic structure in which the reflectance is maximized and the periodic structure in which the reflectance is maximized in the vertical direction, the reflectance can be increased for light emitted from the MQW layer in all directions.

Then, to make a hole approximately 30μmφ the position for forming the pad electrode, forming a photoresist mask by dry etching using CHF ₃ gas, and SiO ₂ portion photoresist mask is not formed The SiN was removed to expose the ITO and n-type GaN layer. Here, since the selection ratio of SiO ₂ or SiN to ITO by CHF ₃ is 5 or more, ITO serves as a good etching stop layer. Similarly, since the selection ratio between SiO ₂ or SiN and n-type GaN layer by CHF ₃ is 5 or more, n-type GaN works as a good etch stop layer.

  Next, a photoresist mask for forming the pad electrode by lift-off was formed, and Ti 15 nm, Mo 20 nm, and Au 500 nm were deposited as the pad electrodes 910 and 920 and lifted off. The pad electrode was formed on the p side and the n side simultaneously. The light-emitting element manufactured in this manner was 25 mW, and the driving voltage was 3.2V.

The light-emitting element fabricated as described above has low resistance because current is efficiently injected into the entire surface of the light-emitting element by the ITO electrode (transparent conductive layer 907), and the multilayer film of SiO ₂ and SiN is highly reflective. Therefore, the light emitted from the light emitting layer to the dielectric reflecting layer side is efficiently reflected, and the light is efficiently extracted to the sapphire substrate side by the unevenness at the interface between the sapphire substrate and the nitride semiconductor layer. Thus, light is efficiently extracted from the back surface of the sapphire substrate or the side surface of the sapphire substrate to the outside.

  In the light emitting device of this embodiment, the sapphire substrate side may be mounted on a pedestal such as a frame, and light may be extracted from the side surface of the sapphire substrate, or the pad electrode side may be mounted with bumps or the like like a flip chip. Thus, light may be extracted from the back and side surfaces of the sapphire substrate.

  Whether wire bonding to the pad electrode or flip chip mounting with bumps or the like, the pad electrode size is generally required to be about 80 μmφ in general. This is because it is determined by the ball size or bump size of the ball bond. Further, generally used pad electrode material requires a material having a poor reflectance such as Au, but a central 30 μmφ region between the pad electrode having a poor reflectance and the light emitting layer as in this embodiment. In other cases, since a reflective layer made of a dielectric is formed, light emitted in the direction of the pad electrode from the light emitting layer is reflected by the reflective layer made of a dielectric except for the central 30 μmφ region. It is possible to greatly prevent the light from being absorbed.

  Even when the chip size is reduced, the pad electrode cannot be made small, so most of the chip surface will be covered with a pad electrode with poor reflectivity, but by forming a reflective layer made of a dielectric Thus, a light-emitting element with high light extraction efficiency can be produced without being affected by the pad electrode having poor reflectance.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 101 Support substrate, 102 2nd joining layer, 103 1st joining layer, 104 Eutectic joining layer, 105,805,908 Reflective layer, 106,806,907 Transparent conductive layer, 107,807,905 p-type GaN layer , 108,808,904 p-type AlGaN layer, 109,809,906 p-type nitride semiconductor layer, 110,810,903 light emitting layer, 111,811,902 n-type nitride semiconductor layer, 112,812 first electrode , 113 Second electrode, 114, 814 Current blocking region, 115, 815 Through hole, 201, 901 Growth substrate, 202 Buffer layer, 203 Laser light, 601 Recess, 801 Plating layer, 803 Plating underlayer, 910, 920 Pad electrode.

Claims (20)

Including a supporting substrate, a reflective layer made of a dielectric, a transparent conductive layer, a p-type nitride semiconductor layer, a light emitting layer, and an n-type nitride semiconductor layer in this order;
The length in the direction perpendicular to the thickness direction of the transparent conductive layer is smaller than the length in the direction perpendicular to the thickness direction of the p-type nitride semiconductor layer,
The reflective layer made of the dielectric is in contact with both side surfaces of the transparent conductive layer and the reflective layer side surface of the transparent conductive layer made of the dielectric, and the transparent conductive layer of the p-type nitride semiconductor layer The nitride semiconductor light emitting element which is in contact with the surface which is a part of side surface, and is not in contact with the said transparent conductive layer. The nitride semiconductor light emitting element according to claim 1, wherein the transparent conductive layer is made of a conductive metal oxide. The nitride semiconductor light emitting element according to claim 1, wherein the transparent conductive layer is made of an n-type nitride semiconductor. The reflective layer made of a dielectric body, to any one of claims 1 to 3 having a laminated structure formed by laminating alternately a layer of dielectric material having a layer and a low refractive index made of a dielectric material having a high refractive index The nitride semiconductor light emitting device described. The reflective layer made of a dielectric material, to the radiation emitted from the light emitting layer, the nitride semiconductor light emitting device according to any one of claims 1 to 4 having a reflectance of 80% to 100%. Of the surfaces of the nitride semiconductor layer made of the p-type nitride semiconductor layer, the light emitting layer, and the n-type nitride semiconductor layer, the surface on the side where the reflective layer made of the dielectric is formed is flat. Item 6. The nitride semiconductor light-emitting device according to any one of Items 1 to 5 . Of the surfaces of the nitride semiconductor layer composed of the p-type nitride semiconductor layer, the light emitting layer, and the n-type nitride semiconductor layer, the surface opposite to the side on which the reflective layer composed of the dielectric is formed is uneven. the nitride semiconductor light emitting device according to any one of claims 1 to 6 having a shape. The reflective layer made of a dielectric body, in a region immediately below the transparent conductive layer, the nitride semiconductor light emitting device according to any one of claims 1 to 7 having a through hole penetrating in the thickness direction. The p-type nitride semiconductor layer, a nitride semiconductor light emitting device according to any one of claims 1-8 comprising a current blocking region formed in contact with the transparent conductive layer. 10. The nitride semiconductor light emitting device according to claim 9 , wherein the through hole of the reflective layer made of the dielectric is located immediately below the current blocking region. Between the reflective layer of the dielectric and the support substrate, any of claims 1 to 10 having a eutectic bonding layer having a single layer or a multilayer structure composed of a metal or which contains an alloy comprising eutectic bonding metal A nitride semiconductor light emitting device according to claim 1. The nitride semiconductor light-emitting element according to claim 11 , further comprising an adhesion layer between the reflective layer made of the dielectric and the eutectic bonding layer. The nitride semiconductor light emitting device according to any one of claims 1 to 10 , wherein the support substrate is a substrate made of a plated metal or alloy. The thickness of the reflective layer made of a dielectric material is a nitride semiconductor light emitting device according to any one of claims 1 to 13, which is a 0.2 to 5 .mu.m. A method for manufacturing a nitride semiconductor light emitting device according to claim 1 ,
A step (A) of laminating an n-type nitride semiconductor layer, a light emitting layer, and a p-type nitride semiconductor layer in this order on a growth substrate;
(B) forming a layer made of a conductive material on the surface of the p-type nitride semiconductor layer, and then forming a plurality of transparent conductive layers spaced apart from the layer at a predetermined interval ;
Forming a reflective layer made of a dielectric on the entire exposed surface of the obtained laminate (C);
A step (D) of laminating a support substrate;
Removing the growth substrate (E);
A step (F) of obtaining a plurality of nitride semiconductor light emitting devices by dividing the chip;
A method for manufacturing a nitride semiconductor light-emitting device comprising: After the step (C), the reflective layer of the dielectric, and forming a through hole penetrating in the thickness direction, to claim 15, further comprising a step (G) to expose a portion of the transparent conductive layer The manufacturing method of the nitride semiconductor light-emitting device of description. The method for manufacturing a nitride semiconductor light emitting element according to claim 16 , wherein in the step (G), the through hole is formed by etching, and the transparent conductive layer serves as an etching stop layer. Between the step (E) and the step (F), a step (H) is further provided in which concave portions are formed at substantially constant intervals from the n-type nitride semiconductor layer side to expose the reflective layer made of the dielectric. method of manufacturing a nitride semiconductor light emitting device according to any one of claims 15-17 comprising. Wherein after step (E), method of manufacturing the nitride semiconductor light emitting device according to any one of claims 15-18, further comprising a step (I) for forming irregularities on the surface of the n-type nitride semiconductor layer. In the step (F), location, method of manufacturing the nitride semiconductor light emitting device according to claim 18 or 19 which is any position on the bottom surface of the recess for chip division.

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