JP4543621B2 - Nitride semiconductor device and method for manufacturing nitride semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nitride semiconductor device used for a light emitting diode (LED), a laser diode (LD), and the like, and a method for manufacturing the nitride semiconductor device, and more particularly to a nitride semiconductor device capable of improving light extraction efficiency and The present invention relates to a method for manufacturing a nitride semiconductor device.
[0002]
[Prior art]
Nitride semiconductors are used for various light sources such as full-color LED displays, traffic signal lights, and image scanner light sources as blue and green high-intensity light-emitting diode (LED) materials. A blue LED using a nitride semiconductor has been put into practical use as a white LED by combining with a phosphor emitting yellow fluorescence. White LEDs are expected as an alternative light source for white fluorescent lamps because they have LED characteristics such as long life and low power consumption.
[0003]
As such an LED structure, an N-type nitride compound semiconductor layer 200, a P-type nitride compound semiconductor layer 300, a P-type translucent electrode 400, and a P-type pad electrode 500 are formed on a translucent substrate 100. An element structure in which an N-type pad electrode 600 is arranged is known (FIG. 7).
[0004]
[Patent Document 1]
JP 2003-86843 A (FIG. 6)
[Patent Document 2]
Japanese Patent Laid-Open No. 50-122889
[Patent Document 3]
JP 52-37783 A
[Patent Document 4]
JP 57-149781 A
[Patent Document 5]
JP-A-9-213996
[Patent Document 6]
WO01 / 041219 (Japanese translations of PCT publication No. 2004-505434)
[Patent Document 7]
WO01 / 041225 (Japanese Patent Publication No. 2004-511080)
[Patent Document 8]
WO02 / 013281 (Japanese translations of PCT publication No. 2004-506331)
[Patent Document 9]
JP 2000-196152 A
[Patent Document 10]
Japanese Patent Application No. 2002-220564 (Japanese Patent Laid-Open No. 2004-063819)
[Patent Document 11]
Japanese Patent Application No. 2003-110113 (Japanese Patent Laid-Open No. 2005-005679)
[0005]
[Problems to be solved by the invention]
However, the conventional LED has a problem that the light output is reduced by being absorbed by the P-type electrode or the N-type electrode. For this reason, the LED having the conventional structure has a problem of reducing the light extraction efficiency extracted from the light emitting layer to the outside.
[0006]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a nitride semiconductor device capable of improving the light extraction efficiency extracted from the light emitting layer to the outside and a method for manufacturing the nitride semiconductor device. And
[0007]
[Means for Solving the Problems]
To achieve the above object, a nitride semiconductor device according to a first aspect of the present invention includes a nitride semiconductor layer having a light emitting layer, and a first electrode provided on the nitride semiconductor layer. The nitride semiconductor light emitting device, wherein the nitride semiconductor layer has a convex member on a surface on the first electrode side, and the convex member is a nitride semiconductor layer on the first electrode side. The light emitting layer is made of a translucent material having a refractive index comparable to that of the nitride semiconductor layer or having a refractive index difference of 20% or less with respect to the nitride semiconductor layer. The light from the light emitting layer can be reflected at the boundary surface with the first electrode.
In addition, a nitride semiconductor device according to the second aspect of the present invention includes a nitride semiconductor layer including a light emitting layer, and a first electrode provided in contact with the nitride semiconductor layer. In the light emitting device, the first electrode has a flat surface on the nitride semiconductor layer side, and the nitride semiconductor layer has a recess on the surface on the first electrode side. Includes a translucent convex member made of a material having a refractive index smaller than that of the nitride semiconductor layer on the first electrode side, and the convex member is a boundary between the concave semiconductor layer and the nitride semiconductor layer. The surface is capable of reflecting light from the light emitting layer.
Furthermore, the nitride semiconductor device according to the third aspect of the present invention includes a support substrate, a first electrode provided on the support substrate, and a nitridation provided on the first electrode and including a light emitting layer. A nitride semiconductor light emitting device comprising, in order, an oxide semiconductor layer, The first electrode has a flat surface on the nitride semiconductor layer side, The nitride semiconductor layer has a recess in the surface on the first electrode side, and the translucency is made of a material having a smaller refractive index than the nitride semiconductor layer on the first electrode side in the recess. The convex member is arranged, and the convex member can reflect light from the light emitting layer at a boundary surface between the concave portion and the nitride semiconductor layer.
Furthermore, the nitride semiconductor device according to the fourth aspect of the present invention is a nitride semiconductor light emitting device comprising a nitride semiconductor layer having a light emitting layer, and a first electrode provided on the nitride semiconductor layer. The nitride semiconductor layer has a convex member on the surface on the first electrode side, and the convex member has a refractive index smaller than that of the nitride semiconductor layer on the first electrode side. It consists of a translucent material, The said convex-shaped member can reflect the light from the said light emitting layer in the interface with the said nitride semiconductor layer, It is characterized by the above-mentioned.
[0008]
Furthermore, the nitride semiconductor device according to the fifth aspect of the present invention is such that the nitride semiconductor light emitting device further comprises a support substrate and a conductive layer on the support substrate, and the first electrode is the conductive layer. It is arranged above. With this configuration, in the counter electrode structure in which the first electrode and the second electrode face each other, light can be efficiently diffusely reflected on the electrode on the support substrate side, that is, the first electrode side, and the light emitting layer can be externally transmitted The light extraction efficiency of the extracted light can be improved.
[0009]
Furthermore, in the nitride semiconductor device according to the sixth aspect of the present invention, the nitride semiconductor layer includes a region where the first electrode is disposed on the first electrode side surface, and an insulating protective film. And a reflective film forming a boundary surface capable of reflecting light from the light emitting layer is disposed on the protective film.
Furthermore, in the nitride semiconductor device according to the seventh aspect of the present invention, the nitride semiconductor layer has a first conductivity type nitride semiconductor layer, a light emitting layer, and a second conductivity type nitride semiconductor layer. The first and second conductivity type nitride semiconductor layers are provided with a first electrode and a second electrode, respectively, and the first and second electrodes face each other across the nitride semiconductor layer. Features.
Furthermore, in the nitride semiconductor device according to the eighth aspect of the present invention, the first conductivity type nitride semiconductor layer is a p-type nitride semiconductor layer, and the first electrode is a p-electrode. Features. As a material capable of obtaining ohmic contact with a p-type nitride semiconductor, only a material having a low reflectance as compared with Al capable of obtaining ohmic contact with an n-type nitride semiconductor layer is conventionally known. Therefore, when the convex member is arranged between the p-type nitride semiconductor layer and the p electrode, light on the p electrode side can be efficiently diffused and light absorption by the p electrode can be reduced. Moreover, in the nitride semiconductor, the resistance of the p-type nitride semiconductor is larger than that of the n-type nitride semiconductor. Therefore, it is necessary to reduce the thickness of the p-type nitride semiconductor layer, and in particular, the resistance to movement in the carrier lateral direction (perpendicular to the crystal growth direction) increases. Therefore, the p-electrode in contact with the p-type nitride semiconductor layer is generally formed with a large area. For this reason, the light extraction efficiency extracted to the outside can be further improved by disposing the convex member between the p-electrode, which is an electrode having a larger area, and the nitride semiconductor layer.
[0010]
Further, in the nitride semiconductor element, the convex member is preferably made of a material having a refractive index smaller than that of the nitride semiconductor layer formed on the first electrode side.
[0011]
Further, in the nitride semiconductor element, the convex member is preferably made of a material having a refractive index comparable to that of the nitride semiconductor layer formed on the first electrode side. Here, the refractive index comparable to that of the nitride semiconductor layer means that the light from the light emitting layer can be sufficiently incident at the interface with the nitride semiconductor layer, and the refractive index of the nitride semiconductor layer. The difference is preferably 20% or less. As such a material, for example, Nb ₂ O _Five Niobium oxide, a material that does not absorb ₂ O _Five Such as tantalum oxide, ZrO ₂ Etc. are used, and in particular, Nb ₂ O _Five Niobium oxide, a material that does not absorb ₂ O _Five Tantalum oxide, which is a non-absorbing material, is preferred.
[0012]
Furthermore, the method for manufacturing a nitride semiconductor device according to the ninth aspect of the present invention includes a nitride semiconductor layer having a first conductivity type nitride semiconductor layer, a light emitting layer, and a second conductivity type nitride semiconductor layer in this order. A nitride semiconductor light emitting device comprising: a nitride semiconductor layer; and a first electrode and a second electrode on the first and second conductivity type nitride semiconductor layers, respectively, wherein the nitride is formed on a growth substrate. A step of forming a semiconductor layer, and the surface of the nitride semiconductor layer has a refractive index comparable to that of the nitride semiconductor layer of the first conductivity type or a refractive index difference with the nitride semiconductor layer of 20% or less, A step of forming a translucent convex member made of the above material, and a step of forming the first electrode on the surfaces of the nitride semiconductor layer and the convex member.
[0013]
Furthermore, the method for manufacturing a nitride semiconductor device according to the tenth aspect of the present invention includes a nitride semiconductor layer having a first conductivity type nitride semiconductor layer, a light emitting layer, and a second conductivity type nitride semiconductor layer in this order. A nitride semiconductor light emitting device comprising: a nitride semiconductor layer; and a first electrode and a second electrode on the first and second conductivity type nitride semiconductor layers, respectively, wherein the nitride is formed on a growth substrate. A step of forming a semiconductor layer, a step of forming a recess in the surface of the nitride semiconductor layer, and a refractive index smaller than that of the nitride semiconductor layer of the first conductivity type in the recess of the nitride semiconductor layer. The method includes a step of forming a translucent convex member made of a material, and a step of forming a first electrode on the surface of the nitride semiconductor layer and the convex member.
[0014]
Furthermore, in the method for manufacturing a nitride semiconductor device according to the eleventh aspect of the present invention, the step of forming a nitride semiconductor layer on the growth substrate includes the step of forming a second conductivity type nitride semiconductor layer on the growth substrate. A step of forming a light emitting layer and a first conductivity type nitride semiconductor layer in this order. The method for manufacturing a nitride semiconductor device includes a step of bonding a support substrate on the first electrode, and the growth. Removing the substrate and exposing the second conductive type nitride semiconductor layer; and forming a second electrode on the exposed surface of the second conductive type nitride semiconductor layer; It is characterized by providing. With this configuration, in the counter electrode structure in which the first electrode and the second electrode face each other, light can be efficiently diffusely reflected on the electrode on the support substrate side, that is, on the first electrode side, and the light emitting layer can be externally transmitted. It is possible to provide a method for manufacturing a nitride semiconductor device capable of improving the light extraction efficiency of the extracted light.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below exemplifies a nitride semiconductor device and a method for manufacturing the nitride semiconductor device for embodying the technical idea of the present invention. The manufacturing method of a physical semiconductor element is not specified as follows.
[0016]
Further, the present specification by no means specifies the members shown in the claims to the members of the embodiments. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Further, in the following description, the same name and reference numeral indicate the same or the same members, and detailed description will be omitted as needed.
[0017]
[Embodiment 1]
(Element structure)
FIG. 1 shows a schematic diagram of a nitride semiconductor device 1 according to Embodiment 1 of the present invention. FIG. 1B is a plan view of the nitride semiconductor device 1, and FIG. 1A is a side cross-sectional view taken along one-dot chain line XX ′ shown in FIG. The nitride semiconductor device 1 includes a first electrode 21, a nitride semiconductor layer 10 having a first conductivity type nitride semiconductor layer 11, a light emitting layer 13, and a second conductivity type nitride semiconductor layer 12; A second electrode 22.
[0018]
A convex member 31 is disposed between the first electrode 21 and the nitride semiconductor layer 10. For example, the convex member 31 is formed in a circular shape when viewed from above. In the example of FIG. 1, a plurality of convex members 31 are arranged in the region of the first electrode 21 as represented by the broken line in FIG. The convex member 31 preferably has an inclined surface (a surface inclined with respect to the semiconductor growth surface) when viewed from the side. The angle of the inclined surface which is the side surface of the convex member 31 is larger than 0 ° and smaller than 90 °. Preferably they are 30 degrees or more and 60 degrees or less. This is because with this configuration, the light from the light emitting layer 13 can be diffused more efficiently, and the light extraction efficiency extracted to the outside can be further improved. The convex member 31 is made of a material having a refractive index smaller than that of the first conductive type nitride semiconductor layer 11 which is a nitride semiconductor layer formed on the first electrode 21 side. As a material having a refractive index smaller than that of the nitride semiconductor layer, for example, SiO ₂ Etc. Thereby, the light from the light emitting layer 13 can be efficiently reflected at the boundary surface between the first conductive type nitride semiconductor layer 11 and the convex member 31.
[0019]
The nitride semiconductor device 1 further includes a support substrate 42 and a conductive layer 41 on the support substrate 42. The first electrode 21 is disposed on the conductive layer 41. A protective film 50 is disposed between the conductive layer 41 and the region where the first electrode 21 and the convex member 31 are not formed. The protective film 50 is also disposed on the exposed surface of the conductive layer 41, that is, the region where the nitride semiconductor layer 10 is not formed. Further, the protective film 50 may be partially disposed between the first electrode 21 and the conductive layer 41. Further, the protective film 50 may be made of the same material as the convex member 31. Furthermore, a reflective film made of a highly reflective material such as Al, Ag, or Rh may be disposed between the protective film 50 and the conductive layer 41. Thereby, the light from the light emitting layer 13 can be efficiently reflected at the boundary surface between the protective film 50 and the reflective film.
[0020]
The first conductivity type nitride semiconductor layer 11 is formed of, for example, a p-type nitride semiconductor layer, and the first electrode can be a p-electrode in contact with the p-type nitride semiconductor layer. In this case, the first electrode 21 as a p-electrode is formed with the same area as the n-electrode in contact with the n-type nitride semiconductor layer or with a larger area than the n-electrode. In the example of FIG. 1, as represented by the broken line in FIG. 1B, the first electrode 21 is substantially the same as the nitride semiconductor layer excluding the region where the second electrode 22 is formed as viewed from above. It is formed in the entire area. Materials for the p-electrode that can make ohmic contact with the p-type nitride semiconductor layer include Ni, Au, W, Pt, Ti, Al, Ir, Rh, Ag, Ni-Au, Ni-Au-RhO, and Rh-Ir. , Rh—Ir—Pt, and the like, and it is particularly preferable to use Rh, Ag, Ni, Au having a high reflectance. Ti-Al, W-Al, Al, etc. are mentioned as a material of n electrode from which an ohmic contact with an n-type nitride semiconductor layer is obtained. An n-side pad electrode is formed on the n electrode. Examples of the material for the n-side pad electrode include Ni—Au, W—Pt—Au, and Pt—Au.
[0021]
In the nitride semiconductor device 1 of the first embodiment, the first conductivity type nitride semiconductor layer 11 has a recess on the surface on the first electrode 21 side, and the convex member 31 is disposed in the recess. The convex member 31 has a height of 5 μm or less, preferably about 3 μm. The diameter of the convex member 31 is 1 μm or more and 10 μm or less.
[0022]
In FIG. 1A, the example in which the convex member 31 is provided in the first conductive type nitride semiconductor layer 11 has been described. However, the present invention is not limited to this example. For example, as shown in FIG. The convex member 31 can also be provided extending in the vertical direction so as to penetrate the nitride semiconductor layer 12 of the second conductivity type.
[0023]
〔Production method〕
Next, a method for manufacturing the nitride semiconductor device 1 according to the first embodiment will be described with reference to FIGS.
[0024]
(Nitride semiconductor layer)
First, as shown in FIG. 2A, a nitride semiconductor layer 10 having a second conductive type nitride semiconductor layer 12, a light emitting layer 13, and a first conductive type nitride semiconductor layer 11 on a growth substrate 60 is formed. Form. The growth substrate 60 may be any substrate that can epitaxially grow a nitride semiconductor, and the size and thickness of the growth substrate are not particularly limited. As this growth substrate, sapphire or spinel (MgAl) whose main surface is one of the C-plane, R-plane, and A-plane is used. ₂ O _Four Insulating substrates such as silicon carbide (6H, 4H, 3C), silicon, ZnS, ZnO, Si, GaAs, diamond, and oxides such as lithium niobate and neodymium gallate that are lattice-bonded to nitride semiconductors A substrate is mentioned. In addition, a nitride semiconductor substrate such as GaN or AlN can be used as long as it is thick enough to allow device processing (several tens of μm or more). The growth substrate may be off-angle, and when a sapphire C surface is used, the growth substrate has a range of 0.01 ° to 0.5 °, preferably 0.05 ° to 0.2 °.
[0025]
The nitride semiconductor is formed on the growth substrate via the buffer layer. The buffer layer is, for example, of the general formula Al _g Ga _1-g Nitride semiconductor represented by N (0 ≦ g <1), more preferably Al _g Ga _1-g A nitride semiconductor represented by N (0 ≦ g ≦ 0.5) is used. The film thickness of the buffer layer is preferably 0.002 to 0.5 μm, more preferably 0.005 to 0.2 μm, and still more preferably 0.01 to 0.05 μm. The growth temperature of the buffer layer is preferably 200 to 900 ° C, more preferably 400 to 800 ° C. Thereby, dislocations and pits on the nitride semiconductor layer can be reduced. Furthermore, Al is formed on the growth substrate by ELO (Epitaxial Lateral Overgrowth) method. _x Ga _1-x N (0 ≦ X ≦ 1) layers may be grown. The ELO method is to reduce dislocations by laterally growing a nitride semiconductor to bend and converge the threading dislocations.
[0026]
After forming the buffer layer on the growth substrate 60, it is preferable to form a high temperature growth layer grown at a higher temperature than the buffer layer. As the high temperature growth layer, undoped GaN or GaN doped with n-type impurities can be used. Preferably, the crystallinity can be grown well by using undoped GaN. The film thickness of the high temperature growth layer is 1 μm or more, preferably 3 μm or more. The growth temperature of the high-temperature growth layer is 900 to 1100 ° C., preferably 1050 ° C. or higher.
[0027]
Next, the second conductivity type nitride semiconductor layer 12 is formed on the high temperature growth layer. Here, an example in which the second conductivity type nitride semiconductor layer 12 is an n-type nitride semiconductor layer will be described. An n-type contact layer is formed on the high temperature growth layer. The n-type contact layer is a layer in which an n-electrode as the second electrode 22 is formed. For example, GaN doped with n-type impurities is used for the n-type contact layer. The n-type impurity concentration of the n-type contact layer is not particularly limited, but preferably 1 × 10. ¹⁷ ~ 1x10 ²⁰ / Cm ^Three , More preferably 1 × 10 ¹⁸ ~ 1x10 ¹⁹ / Cm ^Three It is. The thickness of the n-type contact layer is not particularly limited, but is preferably 1 μm or more, more preferably 3 μm or more.
[0028]
An n-side multilayer film layer is formed on the n-type contact layer. The n-side multilayer film has a composition larger than the band gap energy of the active layer described later, and Al _j Ga _1-j N (0 ≦ j <0.3) is preferable. For example, the n-side multilayer film has a three-layer structure of undoped GaN, GaN doped with n-type impurities, and undoped GaN. The n-type impurity concentration is not particularly limited, but preferably 1 × 10. ¹⁷ ~ 1x10 ²⁰ / Cm ^Three , More preferably 1 × 10 ¹⁸ ~ 1x10 ¹⁹ / Cm ^Three It is.
[0029]
Instead of the n-side multilayer film layer, Al having a concentration gradient set to the n-type impurity concentration _j Ga _1-j N (0 ≦ j <0.3) or Al with a composition gradient of Al set _j Ga _1-j N (0 ≦ j <0.3) can also be set. Further, the n-side multilayer film layer can be omitted. Further, the n-side multilayer layer is omitted, and the n-type contact layer is made of Al. _e Ga _1-e N (0 <e <0.3) can also be set. In this case, the removal of GaN from the high temperature growth layer can effectively reduce the absorption of light from the light emitting layer by the GaN layer. Furthermore, a second n-side multilayer film layer can be formed on the n-side multilayer film layer. The second n-side multilayer layer is, for example, In _r Ga _1-r N (0 <r <1), Al _s Ga _1-s N (0 ≦ s <1). In the case of a superlattice structure, the thickness of each layer forming the multilayer layer is preferably 100 mm or less, more preferably 70 mm or less, and further preferably 10 to 40 mm.
[0030]
The light emitting layer (active layer) used in the present invention is, for example, Al. _a In _b Ga _1-ab A well layer made of N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, a + b ≦ 1), Al _c In _d Ga _1-cd And a barrier layer made of N (0 ≦ c ≦ 1, 0 ≦ d ≦ 1, c + d ≦ 1). The nitride semiconductor used for the active layer may be any of non-doped, n-type impurity doped, and p-type impurity doped. However, it is preferable to increase the light emitting element by using a non-doped or n-type impurity doped nitride semiconductor. Can be output. As the barrier layer, a nitride semiconductor having a band gap energy larger than that of the well layer is used.
[0031]
Next, the first conductivity type nitride semiconductor layer 11 is formed on the light emitting layer 13. Here, an example in which the first conductivity type nitride semiconductor layer 11 is a p-type nitride semiconductor layer will be described. First, a p-type cladding layer is formed on the light emitting layer 13. The p-type cladding layer is made of a material having a composition larger than the band gap energy of the active layer. The p-type cladding layer is not particularly limited as long as carriers can be confined in the active layer. _k Ga _1-k N (0 ≦ k <1) is used and Al _k Ga _1-k N (0 <k <0.4) is preferred. The film thickness of the p-type cladding layer is not particularly limited, but is preferably 0.01 to 0.3 μm, more preferably 0.04 to 0.2 μm. The p-type impurity concentration of the p-type cladding layer is 1 × 10 ¹⁸ ~ 1x10 ^{twenty one} / Cm ^Three 1 × 10 ¹⁹ ~ 5x10 ²⁰ cm ^Three It is. When the p-type impurity concentration is within this range, the bulk resistance can be reduced without reducing the crystallinity. The p-type cladding layer may be a single layer or a multilayer film layer (superlattice structure). In the case of a multilayer film layer, the above Al _k Ga _1-k It is composed of a multilayer film composed of N and a nitride semiconductor layer having a smaller band gap energy. The multilayer layer is, for example, In _l Ga _1-l N (0 ≦ l <1), Al _m Ga _1-m N (0 <m <1). In the case of a superlattice structure, the thickness of each layer forming the multilayer layer is preferably 100 mm or less, more preferably 70 mm or less, and further preferably 10 to 40 mm. In addition, when the p-type cladding layer is a multilayer film composed of a layer having a large band gap energy and a layer having a small band gap energy, at least one of the layer having a large band gap energy and the layer having a small band gap energy is doped with a p-type impurity. You may let them. In addition, when doping both a layer having a large band gap energy and a layer having a small band gap energy, the doping amount may be the same or different.
[0032]
Next, a p-type contact layer is formed on the p-type cladding layer. The p-type contact layer is made of Al _f Ga _1-f N (0 ≦ f <1) is used, in particular Al _f Ga _1-f By configuring with N (0 ≦ f <0.3), good ohmic contact with the first electrode 21 becomes possible. The p-type impurity concentration is 1 × 10 ¹⁷ / Cm ^Three The above is preferable. The p-type contact layer preferably has a composition gradient that has a high p-type impurity concentration on the p-electrode side and a small mixed crystal ratio of Al. In this case, the composition gradient may change the composition continuously or may change the composition stepwise in a discontinuous manner. For example, the p-type contact layer is in contact with the ohmic electrode and has a first p-type contact layer having a high p-type impurity concentration and a low Al composition ratio, and a second p-type contact having a low p-type impurity concentration and a high Al composition ratio. It can also consist of layers. Good ohmic contact can be obtained by the first p-type contact layer, and self-absorption can be prevented by the second p-type contact layer.
[0033]
The nitride semiconductor described above can be formed using a vapor phase growth method such as a metal organic chemical vapor deposition (MOCVD) method, a halide vapor phase epitaxial growth (HVPE) method, or a molecular beam epitaxy (MBE) method.
[0034]
Next, when the nitride semiconductor is formed in the order of the n-type nitride semiconductor layer and the p-type nitride semiconductor layer, after growing the nitride semiconductor 2 on the growth substrate 60, the wafer is taken out from the reaction apparatus, Heat treatment is performed at 450 ° C. or higher in an atmosphere containing oxygen. As a result, hydrogen bonded to the p-type nitride semiconductor layer is removed, and a p-type nitride semiconductor layer exhibiting p-type conduction is obtained.
[0035]
(Convex member)
Next, as shown in FIG. 2B, a convex member 31 is formed on the surface of the nitride semiconductor layer, here the surface of the first conductivity type nitride semiconductor layer 11. The convex member 31 is formed in a plurality of minute circular concave portions having a diameter of, for example, about several μm formed on the surface of the first conductivity type nitride semiconductor layer 11 by etching or the like. The recess is formed in a desired shape by patterning using, for example, photolithography. As a material of the convex member 31, for example, SiO ₂ A light-transmitting material having a refractive index smaller than that of the nitride semiconductor layer is used.
[0036]
(First electrode)
Next, as shown in FIG. 2C, the first electrode 21 made of Rh, Ag, Ni, Au or the like is patterned on the surfaces of the first conductive type nitride semiconductor layer 11 and the convex member 31. . The first electrode 21 is formed so as to cover the convex member 31 in almost the entire region of the nitride semiconductor layer excluding the region where the second electrode 22 is formed. Then, heat treatment is performed in an atmosphere containing oxygen.
[0037]
Thereafter, a protective film 50 is formed in a region excluding the region where the first electrode 21 is formed, such as the peripheral portion of the nitride semiconductor element 1. The material of the protective film 50 is SiO ₂ , Al ₂ O _Three , ZrO ₂ TiO ₂ A single layer film or a multilayer film can be used. Further, a highly reflective metal film of Al, Ag, Rh, etc. may be formed between the protective film 50 and the conductive layer 41. Since the reflectance is increased by this metal film, the light extraction efficiency can be improved.
[0038]
(Semiconductor layer side conductive layer)
Next, a semiconductor layer side conductive layer 41 a for alloying at the time of bonding is formed on the first electrode 21. The semiconductor layer side conductive layer 41a is formed of an alloy containing at least one selected from the group consisting of Au, Sn, Pd, and In. The semiconductor layer side conductive layer 41a preferably has a three-layer structure including an adhesion layer, a barrier layer, and a eutectic layer. The adhesion layer contains at least one selected from the group consisting of Ni, Ti, RhO, W, and Mo. The barrier layer contains at least one selected from the group consisting of Pt, Ti, Pd, TiN, W, Mo, WN, and Au. The eutectic layer contains at least one selected from the group consisting of Au, Sn, Pd, and In. The film thickness of the semiconductor layer side conductive layer 41a is 5 μm or less.
[0039]
(Support substrate)
On the other hand, a support substrate 42 is prepared. Examples of the material of the support substrate 42 include a composite of metal and ceramic such as Cu—W, Cu—Mo, AlSiC, AlN, Si, SiC, and Cu—diamond. For example, the general formula of Cu-W and Cu-Mo is Cu _x W _100-x (0 ≦ x ≦ 30), Cu _x Mo _100-x (0 ≦ x ≦ 50). If AlN is used as a support substrate, it is an insulating substrate, which is advantageous when a chip is mounted on a circuit such as a printed circuit board. The advantage of using Si is that it is inexpensive and easy to chip. A preferable film thickness of the support substrate 42 is 50 to 500 μm. Heat dissipation is improved by setting the film thickness of the support substrate 42 within this range.
[0040]
The support substrate side conductive layer 41b is preferably formed also on the surface of the support substrate. The support substrate side conductive layer 41b preferably has a three-layer structure including an adhesion layer, a barrier layer, and a eutectic layer. The support substrate side conductive layer 41b is made of, for example, Ti—Pt—Au, Ti—Pt—Sn, Ti—Pt—Pd or Ti—Pt—AuSn, W—Pt—Sn, RhO—Pt—Sn, RhO—Pt—Au. , RhO—Pt— (Au, Sn) or the like.
[0041]
(Lamination process)
Then, the surface of the semiconductor layer side conductive layer 41a and the surface of the support substrate side conductive layer 41b are made to face each other (FIG. 3A), and the support substrate 42 is heated and pressed onto the first electrode 21 on the nitride semiconductor layer side. Bonding is performed (FIG. 3B). This heating and pressure welding is performed by applying heat of 150 ° C. or higher while pressing.
[0042]
In order to form eutectic in the bonding, it is preferable that an adhesion layer, a barrier layer, and a eutectic layer are provided on the adhesion surface between the support substrate side and the nitride semiconductor side, respectively. The adhesion layer is a layer that ensures high adhesion to the first electrode, and is preferably a metal of Ti, Ni, W, or Mo. The barrier layer is a layer that prevents the metal constituting the eutectic layer from diffusing into the adhesion layer, and is preferably Pt or W. In order to further prevent the metal in the eutectic layer from diffusing into the adhesion layer, an Au film having a thickness of about 0.3 μm may be formed between the barrier layer and the eutectic layer. At the time of bonding, the first electrode / Ti—Pt—AuSn—Pt—Ti / support substrate, the first electrode / RhO—Pt—AuSn—Pt—Ti / support substrate, and the first electrode / Ti—Pt— PdSn—Pt—Ti / support substrate, first electrode / Ti—Pt—AuSn—Pt—RhO / support substrate. This makes it possible to form an alloy that does not easily peel off. By using a conductive layer as a eutectic, bonding at a low temperature is possible, and the adhesive strength is also strong. Bonding at low temperature has a warping mitigating effect.
[0043]
The metal films of the semiconductor layer side conductive layer 41 a and the support substrate side conductive layer 41 b are alloyed by eutectic to form the conductive layer 41. Moreover, it is preferable that the surface metal of bonding differs in the support substrate side and the nitride semiconductor element side. This is because eutectic is possible at a low temperature and the melting point after eutectic is increased.
[0044]
(Growth substrate removal process)
Thereafter, as shown in FIG. 3C, the growth substrate is removed to expose the nitride semiconductor layer, the nitride semiconductor layer is divided into chips, and the exposed surface of the second conductivity type nitride semiconductor layer 12 is exposed. Then, the second electrode 22 is formed. The growth substrate 60 is removed by irradiating an excimer laser from the growth substrate side or by grinding. After removing the growth substrate 60, the exposed surface of the nitride semiconductor is subjected to a CMP (Chemical Mechanical Polish) process to expose the nitride semiconductor layer 12 of the second conductivity type, which is a desired film. At this time, by removing the GaN layer grown at a high temperature or reducing the film thickness, the influence of absorption can be reduced even in an LED having an emission wavelength in the ultraviolet region. By this treatment, the damage layer can be removed, the thickness of the nitride semiconductor layer can be adjusted, and the surface roughness can be adjusted. Next, in order to make the nitride semiconductor element into a chip, outer periphery etching is performed by RIE or the like, and the nitride semiconductor layer on the outer periphery is removed. In order to improve the light extraction efficiency, the exposed surface of the second conductivity type nitride semiconductor layer may be formed with irregularities (dimple processing) by RIE or the like.
[0045]
In the case where an n-type electrode is used as the second electrode 22, Ti—Al—Ni—Au, W—Al—W—Pt—Au, Al—Pt—Au, or the like is used. The second electrode has a thickness of 0.1 to 1.5 μm.
[0046]
Thereafter, the upper surface of the nitride semiconductor element except for the wire bonding region is covered with an insulating external protective film (not shown) and formed into a chip to form a nitride semiconductor element. External protective film is SiO ₂ , Nb ₂ O _Five , Al ₂ O _Three , ZrO ₂ TiO ₂ An insulating film such as is used. In order to improve the light extraction efficiency, the surface of the external protective film may be formed with an uneven shape by RIE or the like.
[0047]
[Embodiment 2]
(Element structure)
FIG. 4 shows a schematic diagram of a nitride semiconductor device 2 according to the second embodiment of the present invention. 4B is a plan view of the nitride semiconductor device 2, and FIG. 4A is a side cross-sectional view taken along the alternate long and short dash line XX ′ shown in FIG. 4B. In the nitride semiconductor device 2 according to the second embodiment, the first electrode 221 has a concave portion on the surface on the nitride semiconductor layer side, the convex member 32 is disposed in the concave portion, and in the second embodiment. The first conductivity type nitride semiconductor layer 211 is different from the first embodiment in that it does not have a recess on the surface on the support substrate 42 side, and the same reference numerals as those in the first embodiment are given. The members are the same as those in the first embodiment, and a description thereof will be omitted.
[0048]
A convex member 32 is disposed between the first electrode 221 and the nitride semiconductor layer 10. For example, the convex member 32 is formed in a circular shape when viewed from above. In the example of FIG. 4, a plurality of convex members 32 are arranged in the region of the first electrode 221 as represented by a broken line in FIG. The convex member 32 is formed of a material having a refractive index comparable to that of the nitride semiconductor layer formed on the first electrode side. As a material having a refractive index similar to that of the nitride semiconductor layer, Nb ₂ O _Five Niobium oxide and Ta which are materials that do not absorb ₂ O _Five Such as tantalum oxide, ZrO ₂ Etc., but Nb ₂ O _Five Niobium oxide, a material that does not absorb ₂ O _Five Tantalum oxide, which is a non-absorbing material, is preferred. Thereby, the reflection from the boundary surface between the first conductive type nitride semiconductor layer 211 and the convex member 32 can be reduced and the light from the light emitting layer 13 can be efficiently incident on the convex member 32. Therefore, the light from the light emitting layer 13 can be efficiently reflected at the boundary surface between the convex member 32 and the first electrode 211. Here, the refractive index comparable to that of the nitride semiconductor layer means that the light from the light emitting layer can be sufficiently incident at the interface with the nitride semiconductor layer, and the refractive index of the nitride semiconductor layer. The difference is preferably 20% or less. The convex member 32 preferably has an inclined surface (a surface inclined with respect to the growth surface of the semiconductor) as viewed from the side. This is because the light from the light emitting layer 13 can be efficiently diffused and reflected, and the light extraction efficiency extracted to the outside can be further improved.
[0049]
In the pattern of the first electrode 221 and the second electrode 22 shown in FIG. 4B, the second electrode 22 is arranged in a substantially rectangular shape at the corner on the diagonal line as shown in FIG. The pattern is such that the first electrode 221 occupies the entire surface of the remaining region. However, the electrode arrangement pattern is not limited to this example, and for example, the pattern shown in FIG. In the example of FIG. 9B, the pattern of the first electrode 221 is configured by a member that covers the periphery with two L-shaped members and a member that is substantially square and is evenly arranged inside. The pattern of the second electrode 22 includes a substantially rectangular member at the remaining area, that is, a corner of the diagonal line so as not to overlap with the first electrode 221, and a rectangular pattern of the first electrode 221 inside. A square pattern that is slightly larger than this is surrounded by a member that is opened. Although not shown, the convex member 32 can be provided on the rectangular first electrode 221. This further improves the light extraction efficiency.
[0050]
〔Production method〕
Next, a method for manufacturing the nitride semiconductor device 2 according to the second embodiment will be described. In the method for manufacturing nitride semiconductor device 2 according to the second embodiment, the first electrode 221 forms a recess on the surface of the nitride semiconductor layer, and the convex member 32 is formed in the recess. Unlike the first embodiment, the first conductive type nitride semiconductor layer 211 in FIG. 2 is different from the first embodiment in that no recess is formed.
[0051]
In the method of manufacturing the nitride semiconductor device 2 according to the second embodiment, a concave portion is not formed on the surface of the first conductivity type nitride semiconductor layer 211, and a plurality of minute plural pieces having a diameter of, for example, several μm are formed on the surface. A circular convex member 32 is formed. The convex member 32 is formed in a desired shape by forming a pattern using, for example, photolithography. The material of the convex member 32 is Nb ₂ O _Five Niobium oxide, a material that does not absorb ₂ O _Five Such as tantalum oxide, ZrO ₂ Etc. are used, but Nb ₂ O _Five Niobium oxide, a material that does not absorb ₂ O _Five Tantalum oxide, which is a non-absorbing material, is preferred.
[0052]
Next, the first electrode 221 made of Rh, Ag, Ni, Au, or the like is patterned on the surfaces of the first conductivity type nitride semiconductor layer 211 and the convex member 32. The first electrode 221 is formed so as to cover the convex member 32 in almost the entire region of the nitride semiconductor layer excluding the region where the second electrode 22 is formed.
[0053]
[Embodiment 3]
(Element structure)
FIG. 5 shows a schematic diagram of a nitride semiconductor device 3 according to the third embodiment of the present invention. 5B is a plan view of the nitride semiconductor device 3, and FIG. 5A is a side cross-sectional view taken along the alternate long and short dash line XX ′ shown in FIG. 5B. The nitride semiconductor device 3 according to the third embodiment is used as the nitride semiconductor device 3 as it is without removing the growth substrate 60 on which the nitride semiconductor layer 10 is grown, and a nitride semiconductor of the second conductivity type. Unlike the first embodiment, the layer 312 is exposed and the first electrode 321 and the second electrode 322 are arranged on the same surface side, and the same reference numerals as those in the first embodiment are given. The members are the same as those in the first embodiment, and a description thereof will be omitted.
[0054]
The convex member 31 is disposed between the first electrode 321 and the nitride semiconductor layer 10. For example, the convex member 31 is formed in a circular shape when viewed from above. In the example of FIG. 5, a plurality of convex members 31 are arranged in the region of the first electrode 321 as represented by a broken line in FIG. The convex member 31 preferably has an inclined surface (a surface inclined with respect to the semiconductor growth surface) when viewed from the side. This is because the light from the light emitting layer 13 can be efficiently diffused and reflected, and the light extraction efficiency extracted to the outside can be further improved. The convex member 31 is made of a material having a refractive index smaller than that of the first conductivity type nitride semiconductor layer 11 which is a nitride semiconductor layer formed on the first electrode 321 side. As a material having a refractive index smaller than that of the nitride semiconductor layer, for example, SiO ₂ Etc. Thereby, the light from the light emitting layer 13 can be efficiently reflected at the boundary surface between the first conductive type nitride semiconductor layer 11 and the convex member 31.
[0055]
〔Production method〕
Next, a method for manufacturing the nitride semiconductor device 3 according to the third embodiment will be described. The method for manufacturing nitride semiconductor layer 10 in nitride semiconductor element 3 according to the third embodiment is the same as that in the first embodiment, and a description thereof will be omitted.
[0056]
After forming the nitride semiconductor layer 10, the convex member 31 is formed on the surface of the nitride semiconductor layer, here the surface of the first conductivity type nitride semiconductor layer 11, and the first conductivity type nitride semiconductor layer is formed. 11 and the light emitting layer 13 are removed to partially expose the second conductive type nitride semiconductor layer 12. The convex member 31 is formed in a plurality of minute circular concave portions having a diameter of, for example, about several μm formed on the surface of the first conductivity type nitride semiconductor layer 11 by etching or the like. The recess is formed in a desired shape by patterning using, for example, photolithography. As a material of the convex member 31, for example, SiO ₂ A light-transmitting material having a refractive index smaller than that of the nitride semiconductor layer is used. On the other hand, the region where the second conductive type nitride semiconductor layer 312 is exposed is etched to expose the region where the second electrode 322 is formed in a substantially rectangular shape.
[0057]
Next, the second conductive type nitride semiconductor in which the first electrode 321 made of Rh, Ag, Ni, Au, or the like is exposed on the surfaces of the first conductive type nitride semiconductor layer 11 and the convex member 31. The layer 312 is patterned with second electrodes 322 made of Ti—Al—Ni—Au, W—Al—W—Pt—Au, Al—Pt—Au, or the like. The first electrode 321 is formed so as to cover the convex member 31 in almost the entire region of the first conductivity type nitride semiconductor layer 11. Then, heat treatment is performed in an atmosphere containing oxygen.
[0058]
Thereafter, outer peripheral etching is performed by RIE or the like to form a nitride semiconductor element into a chip, and the outer peripheral nitride semiconductor layer is removed. Then, the nitride semiconductor element is covered with an insulating external protective film (not shown) except for the wire bonding regions in the first electrode 321 and the second electrode 322, and formed into a chip, thereby forming the nitride semiconductor element. And External protective film is SiO ₂ , Nb ₂ O _Five , Al ₂ O _Three , ZrO ₂ TiO ₂ An insulating film such as is used.
[0059]
[Embodiment 4]
(Element structure)
FIG. 6 shows a schematic diagram of a nitride semiconductor device 4 according to the fourth embodiment of the present invention. FIG. 6B is a plan view of the nitride semiconductor device 3, and FIG. 6A is a side cross-sectional view taken along one-dot chain line XX ′ shown in FIG. 6B. In nitride semiconductor element 4 according to the fourth embodiment, first electrode 421 has a concave portion on the surface on the nitride semiconductor layer side, and convex member 34 is disposed in the concave portion. The first conductivity type nitride semiconductor layer 411 is different from the third embodiment in that the first conductive type nitride semiconductor layer 411 has no recess on the surface on the support substrate 42 side, and the same reference numerals as those in the third embodiment are given. The members are the same as those in the third embodiment, and a description thereof will be omitted.
[0060]
A convex member 34 is disposed between the first electrode 321 and the nitride semiconductor layer 10. For example, the convex member 34 is formed in a circular shape when viewed from above. In the example of FIG. 6, a plurality of convex members 34 are arranged in the region of the first electrode 321 as represented by the broken line in FIG. The convex member 34 is made of a material having a refractive index comparable to that of the nitride semiconductor layer formed on the first electrode side. As a material having a refractive index similar to that of the nitride semiconductor layer, Nb ₂ O _Five Niobium oxide and Ta which are materials that do not absorb ₂ O _Five Examples thereof include tantalum oxide, which is a material that does not absorb the above. Thereby, the reflection from the interface between the first conductive type nitride semiconductor layer 411 and the convex member 34 can be reduced and the light from the light emitting layer 13 can be efficiently incident on the convex member 34. Therefore, the light from the light emitting layer 13 can be efficiently reflected at the boundary surface between the convex member 34 and the first electrode 421. Here, the refractive index comparable to that of the nitride semiconductor layer means that the light from the light emitting layer can be sufficiently incident at the interface with the nitride semiconductor layer, and the refractive index of the nitride semiconductor layer. The difference is preferably 20% or less. The convex member 34 preferably has an inclined surface (a surface inclined with respect to the semiconductor growth surface) when viewed from the side. This is because the light from the light emitting layer 13 can be efficiently diffused and reflected, and the light extraction efficiency extracted to the outside can be further improved.
[0061]
〔Production method〕
Next, a method for manufacturing the nitride semiconductor device 4 according to the fourth embodiment will be described. In the method for manufacturing nitride semiconductor device 4 according to the fourth embodiment, the first electrode 421 forms a recess on the surface of the nitride semiconductor layer, and the convex member 34 is formed in the recess. Unlike the third embodiment, the first conductive type nitride semiconductor layer 411 in FIG. 4 is different from the third embodiment in that no recess is formed, and the description of the other member manufacturing methods is omitted.
[0062]
In the method of manufacturing the nitride semiconductor device 4 according to the fourth embodiment, a concave portion is not formed on the surface of the first conductivity type nitride semiconductor layer 411, and a plurality of minute plural pieces having a diameter of about several μm are formed on the surface. A circular convex member 34 is formed. The convex member 34 is formed in a desired shape by forming a pattern using, for example, photolithography. The material of the convex member 34 is Nb ₂ O _Five Niobium oxide and Ta which are materials that do not absorb ₂ O _Five For example, tantalum oxide, which is a material that does not absorb the same, is used.
[0063]
Next, the second conductivity type nitride semiconductor in which the first electrode 421 made of Rh, Ag, Ni, Au or the like is exposed on the surfaces of the first conductivity type nitride semiconductor layer 411 and the convex member 34. The layer 312 is patterned with second electrodes 322 made of Ti—Al—Ni—Au, W—Al—W—Pt—Au, Al—Pt—Au, or the like. The first electrode 421 is formed so as to cover the convex member 34 in substantially the entire region of the first conductivity type nitride semiconductor layer 11.
[0064]
【Example】
Examples of the present invention will be described in detail below. However, in the following examples, the present invention does not specify the nitride semiconductor element and the method for manufacturing the nitride semiconductor element as follows.
[0065]
[Example 1]
Hereinafter, a method for manufacturing the nitride semiconductor light-emitting diode of Example 1 will be described. First, a growth substrate 60 made of sapphire (C-plane) is set in a MOVPE reaction vessel. Then, while flowing hydrogen, the temperature of the growth substrate 60 is raised to 1050 ° C., and the growth substrate 60 is cleaned.
[0066]
(Buffer layer)
Subsequently, the temperature is lowered to 510 ° C., hydrogen is used as a carrier gas, ammonia and TMG (trimethylgallium) and TMA (trimethylaluminum) are used as a carrier gas, and a buffer layer made of GaN is formed on the growth substrate 60 with a thickness of about 100 mm. Grow with thickness.
[0067]
(High temperature growth layer)
After growing the buffer layer, a high temperature growth layer is formed. First, only TMG is stopped and the temperature is raised to 1050 ° C. After the temperature reaches 1050 ° C., similarly, TMG and ammonia gas are used as source gases, and an undoped GaN layer is grown to a thickness of 1.5 μm.
[0068]
(Second conductivity type nitride semiconductor layer)
Subsequently, at 1050 ° C., similarly, TMG, ammonia gas, and silane gas are used as source gas and silane gas as impurity gas. ¹⁸ /cm ^Three An n-type contact layer made of doped GaN is grown to a thickness of 2.25 μm. The film thickness of this n-type contact layer should just be 2-30 micrometers.
[0069]
Next, the silane gas alone was stopped, and at 1050 ° C., TMG and ammonia gas were used to grow an undoped GaN layer with a thickness of 3000 mm, and then silane gas was added at the same temperature to add Si to 4.5 × 10. ¹⁸ /cm ^Three A doped GaN layer is grown to a thickness of 300 mm, and then only the silane gas is stopped, and an undoped GaN layer is formed to a thickness of 50 mm at the same temperature. Side multilayer film
[0070]
Further, an undoped GaN layer is grown to a thickness of 40 mm, and subsequently the temperature is set to 800 ° C., and TMG, TMI, and ammonia are used to undoped In _0.13 Ga _0.87 The N layer is grown to a thickness of 20 mm. By repeating these operations, 10 layers are alternately stacked, and finally, a second n-side multilayer film having a superlattice structure in which an undoped GaN layer is grown to a thickness of 40 mm is formed to a thickness of 640 mm.
[0071]
(Light emitting layer)
Next, an undoped GaN layer is grown to a thickness of 40 mm at the same temperature. Next, the temperature is set to 800 ° C., and TMG, TMI, and ammonia are used. _0.13 Ga _0.87 N layer is grown 20 mm. By repeating these operations, 10 layers are alternately stacked, and finally, a superlattice structure layer formed by growing 40 nm of GaN layer is grown to a thickness of 640 mm.
[0072]
Next, a barrier layer made of undoped GaN is grown to a thickness of 200 mm, and subsequently the temperature is set to 800 ° C., and TMG, TMI, and ammonia are used to undoped In _0.4 Ga _0.6 A well layer made of N is grown to a thickness of 30 mm. Then, five barrier layers and four well layers are alternately stacked in the order of barrier + well + barrier + well... + Barrier, and an active layer (light emission) having a total quantum film thickness of 1120 mm. Grow layer).
[0073]
(First conductivity type nitride semiconductor layer)
Next, at a temperature of 1050 ° C., TMG, TMA, ammonia, Cp ₂ Mg (cyclopentadienylmagnesium) is used and Mg is 1 × 10 ²⁰ /cm ^Three Doped p-type Al _0.2 Ga _0.8 The N layer is grown to a thickness of 40 mm, followed by a temperature of 800 ° C., and TMG, TMI, ammonia, Cp ₂ 1 x 10 Mg with Mg ²⁰ /cm ^Three Doped In _0.03 Ga _0.97 The N layer is grown to a thickness of 25 mm. These operations are repeated, and five layers are stacked alternately, and finally p-type Al _0.2 Ga _0.8 A multilayer film having a superlattice structure in which the N layer is grown to a thickness of 40 mm is grown to a thickness of 365 mm.
[0074]
Subsequently, at 1050 ° C., TMG, ammonia, Cp ₂ Mg is used, and Mg is 1 × 10 ²⁰ /cm ^Three A p-type contact layer made of doped p-type GaN is grown to a thickness of 1200 mm.
[0075]
After completion of the reaction, the temperature is lowered to room temperature, and the wafer is annealed in a reaction vessel at 700 ° C. in a nitrogen atmosphere to further reduce the resistance of the p-type layer.
[0076]
(Convex member)
After the annealing, the wafer is taken out from the reaction vessel, and a plurality of circular recesses having a diameter of 3 μm, for example, formed on the surface of the p-type contact layer by etching using photolithography. These recesses have SiO ₂ Form.
[0077]
(First electrode)
Then, a p-electrode is used as the first electrode 21, and the convex member 31 is covered with a thickness of 2000 mm using Rh over almost the entire region of the nitride semiconductor layer excluding the region where the second electrode 22 is formed. To form. Then, after performing ohmic annealing at 600 ° C., the protective film SiO ₂ Is formed with a film thickness of 0.3 μm. Thereafter, in order to form the conductive layer 41a, an adhesion layer, a barrier layer, and a eutectic layer are formed in the order of Ti—Pt—Au—Sn—Au with a film thickness of 2000Å-3000Å-3000Å-30000Å-1000Å.
[0078]
(Support substrate)
On the other hand, a support substrate 42 is prepared. A conductive layer is formed on the surface of a support substrate having a thickness of 200 μm and made of Cu 15% and W 85% in the order of Ti—Pt—Pd with a thickness of 2000 mm to 3000 mm to 12000 mm.
[0079]
(Lamination process)
Next, the p-type electrode which is the first electrode 21 and the conductive layer 41 formed on the protective film and the metal film forming surface on the support substrate 42 side are bonded together. A press pressure is applied at a heater set temperature of 280 ° C. A eutectic is formed here.
[0080]
(Growth substrate removal process)
Then, after removing and exposing the sapphire substrate by grinding, the n-type contact layer, which is the exposed surface of the second conductive type nitride semiconductor layer 12, is polished to eliminate surface roughness.
[0081]
(Second electrode)
Next, using an RIE apparatus, SiO ₂ The nitride semiconductor layer is separated into chips using a mask. Next, an n-type electrode as the second electrode 22 is formed on the n-type contact layer in the order of Ti—Al—Ti—Pt—Au with a film thickness of 100Å-2500Å-1000Å-2000Å-6000Å.
[0082]
Next, SiO ₂ An external protective film made of is formed except for the wire bonding region of the n-electrode. Further, unevenness is formed on the external protective film at intervals of 3 μm. Thereafter, the support substrate 42 is polished to 100 μm, and Ti—Pt—Au is formed on the back surface of the support substrate 42 at 1000 to 2000 to 3000 and then dicing is performed.
[0083]
[Example 2]
Next, a method for manufacturing the nitride semiconductor light-emitting diode according to Example 2 will be described. In the method for manufacturing a nitride semiconductor light emitting diode according to the second embodiment, the p-electrode forms a recess in the surface on the nitride semiconductor layer side, and the protruding member 32 is formed in the recess, and the p-type contact in the second embodiment Unlike the first embodiment, no recess is formed in the layer, and the manufacturing method of other members is the same as that of the first embodiment, and the description thereof is omitted.
[0084]
In the method for manufacturing a nitride semiconductor light emitting diode according to the second embodiment, a plurality of circular convex members 32 having a diameter of 3 μm, for example, are formed on the surface of the p-type contact layer without forming a recess. . The convex member 32 is formed in a desired shape by forming a pattern using, for example, photolithography. The material of the convex member 32 is Nb ₂ O _Five Niobium oxide, a material that does not absorb ₂ O _Five Such as tantalum oxide, ZrO ₂ Etc. are used, but Nb ₂ O _Five Niobium oxide, a material that does not absorb ₂ O _Five Tantalum oxide, which is a non-absorbing material, is preferred.
[0085]
Next, a p-electrode made of Rh is formed in a pattern of 2000 mm on the surface of the p-type contact layer and the convex member 32. The p-electrode is formed so as to cover the convex member 32 in almost the entire region of the p-type contact layer except the region where the n-electrode is formed.
[0086]
[Example 3]
Next, a method for manufacturing the nitride semiconductor light emitting diode according to Example 3 will be described. The method for manufacturing the nitride semiconductor layer 10 in the nitride semiconductor light emitting diode according to the third embodiment is the same as that in the first embodiment, and a description thereof is omitted.
[0087]
After forming the nitride semiconductor layer 10, the convex member 31 is formed on the surface of the p-type contact layer, and the first conductive type nitride semiconductor layer, the light emitting layer, and the n-side multilayer film are removed to remove Si. 4.5 × 10 ¹⁸ /cm ^Three An n-type contact layer made of doped GaN is exposed. The convex member 31 is formed in a plurality of circular concave portions having a diameter of 3 μm, for example, formed on the surface of the p-type contact layer by etching or the like. The recess is formed in a desired shape by patterning using, for example, photolithography. As a material of the convex member 31, for example, SiO ₂ A light-transmitting material having a refractive index smaller than that of the nitride semiconductor layer is used. On the other hand, by etching the region where the n-type contact layer is exposed, the region where the n-electrode 322 is formed is exposed in a substantially rectangular shape.
[0088]
Next, a p-electrode made of Rh as the first electrode 321 is 2000 mm on the surface of the p-type contact layer and the convex member 31, and an n-type electrode is formed on the exposed surface of the n-type contact layer with Ti—Al—Ti—. Patterns are formed in the order of Pt—Au with a film thickness of 100Å-2500Å-1000Å-2000Å-6000Å. The p-electrode is formed so as to cover the convex member 31 in almost the entire region of the p-type contact layer. And ohmic annealing is performed at 600 degreeC.
[0089]
Thereafter, outer peripheral etching is performed by RIE or the like to form a nitride semiconductor element into a chip, and the outer peripheral nitride semiconductor layer is removed. Then, the upper surface of the nitride semiconductor element is made of SiO except for the wire bonding region in the p electrode and the n electrode. ₂ A nitride semiconductor light emitting diode is formed by covering with an external protective film made of and chipping. The nitride semiconductor light emitting diode of this embodiment is suitable for a flip chip type nitride semiconductor light emitting diode. This is because light from the light emitting layer can be efficiently extracted from the side surface of the light emitting diode and the growth substrate side.
[0090]
Example 4
Next, a method for manufacturing the nitride semiconductor light emitting diode according to Example 4 will be described. In the method for manufacturing a nitride semiconductor light emitting diode according to Example 4, the p-electrode forms a recess in the surface on the nitride semiconductor layer side, and the convex member 34 is formed in the recess, and the p-type contact in Example 4 Unlike the third embodiment, no recess is formed in the layer, and the manufacturing method of other members is the same as that of the third embodiment, and the description thereof is omitted.
[0091]
In the method for manufacturing a nitride semiconductor light emitting diode according to the fourth embodiment, a concave portion is not formed on the surface of the p-type contact layer, and a plurality of minute convex members 34 having a diameter of, for example, about several μm are formed on the surface. Is formed. The convex member 34 is formed in a desired shape by forming a pattern using, for example, photolithography. The material of the convex member 34 is Nb ₂ O _Five Niobium oxide, a material that does not absorb ₂ O _Five Such as tantalum oxide, ZrO ₂ Etc. are used, but Nb ₂ O _Five Niobium oxide, a material that does not absorb ₂ O _Five Tantalum oxide, which is a non-absorbing material, is preferred.
[0092]
Next, a p-electrode made of Rh as the first electrode 421 is 2000 mm on the surface of the p-type contact layer and the convex member 34, and an n-type electrode is Ti—Al—Ti—on the exposed surface of the n-type contact layer. Patterns are formed in the order of Pt—Au with a film thickness of 100Å-2500Å-1000Å-2000Å-6000Å. The p-electrode is formed so as to cover the convex member 34 in almost the entire region of the p-type contact layer. The nitride semiconductor light emitting diode of this embodiment is suitable for a flip chip type nitride semiconductor light emitting diode. This is because light from the light emitting layer can be efficiently extracted from the side surface of the light emitting diode and the growth substrate side.
[0093]
(Example 5)
Next, a nitride semiconductor light emitting diode according to Example 5 will be described. The nitride semiconductor light-emitting diode of Example 5 was manufactured under the same conditions as in Example 1 except that the first electrode 21 was formed in the order of Rh-Ir-Pt with a film thickness of 400 to 500 to 1000.
[0094]
(Example 6)
Next, a nitride semiconductor light emitting diode according to Example 6 will be described. The nitride semiconductor light emitting diode of Example 6 is the same as in Example 1 or Example 5 except that the second electrode 22 is formed in the order of Ti—Al—Ni—Au with a film thickness of 100Å-5000Å-800Å-7000Å. It manufactured on condition of.
[0095]
In the above example, the example in which the planar shape of the convex member is formed in a circular shape is shown. However, the present invention is not limited to this, and is a stripe shape, a lattice shape, a rectangular shape, or a polygonal shape such as a triangle or a hexagon. Etc., and various shapes can be employed. The convex members are preferably arranged densely.
[0096]
【The invention's effect】
As described above, in the present invention, the convex member is disposed between at least either the p-electrode or the n-electrode and the nitride semiconductor layer, so that the light from the light-emitting layer is efficiently diffusely reflected. The efficiency of extracting light that is extracted to the outside can be improved. By arranging the convex member between at least the electrode having the larger area and the nitride semiconductor layer, the light extraction efficiency extracted to the outside can be further improved. As a material capable of obtaining ohmic contact with a p-type nitride semiconductor, only a material having a low reflectance as compared with Al capable of obtaining ohmic contact with an n-type nitride semiconductor layer is conventionally known. Therefore, when the convex member is arranged between the p-type nitride semiconductor layer and the p electrode, light on the p electrode side can be efficiently diffused and light absorption by the p electrode can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a nitride semiconductor device according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram for explaining the method for manufacturing the nitride semiconductor device according to the first embodiment of the present invention.
FIG. 3 is a schematic diagram for explaining the method for manufacturing the nitride semiconductor device according to the first embodiment of the present invention.
FIG. 4 is a schematic view of a nitride semiconductor device according to the second embodiment of the present invention.
FIG. 5 is a schematic diagram of a nitride semiconductor device according to a third embodiment of the present invention.
FIG. 6 is a schematic diagram of a nitride semiconductor device according to a fourth embodiment of the present invention.
FIG. 7 is a schematic view of a conventional nitride semiconductor light emitting diode.
FIG. 8 is a cross-sectional view of another nitride semiconductor device according to the first embodiment of the present invention.
FIG. 9 is a plan view showing an example of electrode arrangement of the nitride semiconductor device according to the second embodiment of the present invention.
[Explanation of symbols]
1, 2, 3, 4... Nitride semiconductor element
10 ... Nitride semiconductor layer
11, 211, 411... First conductivity type nitride semiconductor layer
12, 312 ... Second conductivity type nitride semiconductor layer
13 ... Light emitting layer
21, 221, 321, 421... First electrode
22, 322 ... second electrode
31, 32, 34 ... convex member
41... Conductive layer
42 ... Support substrate
50 ... Protective film
60 ... Growth substrate

Claims (11)

A nitride semiconductor light emitting device comprising: a nitride semiconductor layer having a light emitting layer; and a first electrode provided on the nitride semiconductor layer,
The nitride semiconductor layer has a convex member on the surface on the first electrode side,
The convex member is made of a translucent material having a refractive index comparable to the nitride semiconductor layer on the first electrode side or a refractive index difference with the nitride semiconductor layer of 20% or less,
The convex member can enter light from the light emitting layer at a boundary surface with the nitride semiconductor layer, and can reflect light from the light emitting layer at a boundary surface with the first electrode. A nitride semiconductor light emitting device characterized by the above. A nitride semiconductor light emitting device comprising: a nitride semiconductor layer including a light emitting layer; and a first electrode provided in contact with the nitride semiconductor layer,
The first electrode has a flat surface on the nitride semiconductor layer side,
The nitride semiconductor layer has a recess on the surface on the first electrode side,
A translucent convex member made of a material having a refractive index smaller than that of the nitride semiconductor layer on the first electrode side is disposed in the concave portion,
The nitride semiconductor light emitting device, wherein the convex member is capable of reflecting light from the light emitting layer at a boundary surface between the concave portion and the nitride semiconductor layer. A nitride semiconductor light emitting device comprising: a support substrate; a first electrode provided on the support substrate; and a nitride semiconductor layer provided on the first electrode and including a light emitting layer. ,
The first electrode has a flat surface on the nitride semiconductor layer side,
The nitride semiconductor layer has a recess on the surface on the first electrode side,
A translucent convex member made of a material having a refractive index smaller than that of the nitride semiconductor layer on the first electrode side is disposed in the concave portion,
The nitride semiconductor light emitting device, wherein the convex member is capable of reflecting light from the light emitting layer at a boundary surface between the concave portion and the nitride semiconductor layer. A nitride semiconductor light emitting device comprising a nitride semiconductor layer having a light emitting layer, and a first electrode provided on the nitride semiconductor layer,
The nitride semiconductor layer has a convex member on the surface on the first electrode side,
The convex member is made of a light-transmitting material with a smaller refractive index than the nitride semiconductor layer on the first electrode side,
The nitride semiconductor light emitting element, wherein the convex member is capable of reflecting light from the light emitting layer at an interface with the nitride semiconductor layer. The nitride semiconductor light emitting device further includes a support substrate and a conductive layer on the support substrate,
The nitride semiconductor light emitting device according to claim 1, wherein the first electrode is disposed on the conductive layer. The nitride semiconductor layer has a region in which the first electrode is disposed and a region in which an insulating protective film is disposed on the first electrode side surface,
6. The nitride semiconductor light-emitting element according to claim 1, wherein a reflective film that forms a boundary surface capable of reflecting light from the light-emitting layer is disposed on the protective film.   The nitride semiconductor layer has a first conductivity type nitride semiconductor layer, a light emitting layer, and a second conductivity type nitride semiconductor layer. The nitride semiconductor according to claim 1, further comprising: one electrode and a second electrode, wherein the first and second electrodes face each other with the nitride semiconductor layer interposed therebetween. Light emitting element. The nitride semiconductor layer of the first conductivity type is a p-type nitride semiconductor layer,
The nitride semiconductor light-emitting element according to claim 1, wherein the first electrode is a p-electrode. A nitride semiconductor layer having a first conductivity type nitride semiconductor layer, a light emitting layer, and a second conductivity type nitride semiconductor layer in this order, and a first conductivity type nitride semiconductor layer and a first conductivity type nitride semiconductor layer respectively. A method for manufacturing a nitride semiconductor light emitting device comprising: a second electrode;
Forming the nitride semiconductor layer on a growth substrate;
A light-transmitting material made of a material having a refractive index comparable to that of the nitride semiconductor layer of the first conductivity type or a refractive index difference with the nitride semiconductor layer of 20% or less on the surface of the nitride semiconductor layer Forming a convex member;
Forming the first electrode on the surfaces of the nitride semiconductor layer and the convex member;
A method for manufacturing a nitride semiconductor device comprising: A nitride semiconductor layer having a first conductivity type nitride semiconductor layer, a light emitting layer, and a second conductivity type nitride semiconductor layer in this order, and a first conductivity type nitride semiconductor layer and a first conductivity type nitride semiconductor layer respectively. A method for manufacturing a nitride semiconductor light emitting device comprising: a second electrode;
Forming the nitride semiconductor layer on a growth substrate;
Forming a recess in the surface of the nitride semiconductor layer;
Forming a light-transmitting convex member made of a material having a refractive index smaller than that of the first conductive type nitride semiconductor layer in the concave portion of the nitride semiconductor layer;
Forming a first electrode on the surfaces of the nitride semiconductor layer and the convex member;
A method for manufacturing a nitride semiconductor device comprising: The step of forming the nitride semiconductor layer on the growth substrate includes the step of forming a nitride semiconductor layer having a second conductivity type on the growth substrate, a light emitting layer, and a nitride semiconductor layer having the first conductivity type in this order. A method for manufacturing a semiconductor light emitting device, comprising:
The method for manufacturing the nitride semiconductor device includes:
Bonding a support substrate on the first electrode;
Removing the growth substrate to expose the second conductive type nitride semiconductor layer;
Forming a second electrode on the exposed surface of the second conductivity type nitride semiconductor layer;
The method for manufacturing a nitride semiconductor device according to claim 9, further comprising:

Images