JP2006303001A - Light emitting diode and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-luminance light emitting diode, especially, a high-luminance white-color light emitting diode, using an LED chip, and also to provide its manufacturing method. <P>SOLUTION: The light emitting diode 21 contains, on the LED chip 24, an inorganic phosphor layer 26 which absorbs at least part of light emitted from the LED chip, converts the wavelength thereof, and emits wavelength-converted light. The filling factor of an inorganic phosphor is 60-97% in the inorganic phosphor layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light emitting diode and a method for manufacturing the same.

  Since the invention of GaN-based blue light-emitting diodes (hereinafter, light-emitting diodes are also referred to as LEDs), progress in LED technology has been remarkable. Among them, white LEDs have recently attracted attention as a highly efficient and highly reliable white illumination light source, and some of them have already been used as a small power small light source. This type of LED is generally a blue LED element coated with a mixture of a yellow phosphor and a transparent resin, and white LEDs and phosphors for white LEDs of this type are disclosed (for example, patents). References 1-3).

  However, since blue light has large energy, the resin is liable to deteriorate. Therefore, when the white LED having such a structure is used for a long time, the resin changes color and the color tone changes. Recently, there has been a movement to develop a white illumination light source using a high-power LED element. In this case, a very strong blue light is irradiated to a limited part, so that the resin is significantly deteriorated and the emission color changes. It happens in a very short time. Moreover, since the heat dissipation from the resin-molded LED element is poor, there is a problem that the temperature easily rises and the color tone of the emitted color shifts to the yellow side as the temperature rises.

  Further, a white LED having a combination of an ultraviolet LED element and three kinds of phosphors of blue, green, and red is also known (see, for example, Patent Document 4). This type of white LED has the advantage that a white color having higher color rendering properties can be realized, but there is a problem that the deterioration of the resin is more remarkable because the ultraviolet ray has higher energy than the blue light described above.

  Further, the color of the formed white LED tends to be difficult to be formed as desired. In other words, the LED chip is as small as about 300 μm square. In addition, a very small amount of phosphor that converts light from the LED chip is required. Therefore, it is extremely difficult to apply and arrange the phosphor. In particular, in a white diode that determines the emission color by mixing light from an LED chip and light that is excited by the light and is different from the light from the LED, the display color is greatly different due to a slight color shift. When mass production of light emitting diodes using mixed colors of phosphors, the range of this color shift is wide, so that it is difficult to form in a desired chromaticity range, and the yield tends to decrease.

  In order to solve such a problem, a method of forming a light emitting diode in which an inorganic phosphor is formed on an LED chip by sputtering is proposed (for example, see Patent Document 5). Although this method can partially solve the above problems, there is a problem that the light emission luminance of the inorganic phosphor layer is insufficient. In addition, there are the following problems in forming an inorganic phosphor thin film by sputtering. First, high vacuum is required and production equipment is expensive. Next, the film formation rate is extremely slow, and the productivity is insufficient. In this connection, it is difficult to form a phosphor layer having a sufficient thickness.

For the reasons described above, there is a need for a method of forming an inorganic phosphor layer on an LED chip without using a resin to obtain a high-intensity inorganic phosphor layer, and a high-intensity white light-emitting diode manufactured by the method. It was.
Japanese Patent Laid-Open No. 10-163535 International Publication No. 98/05078 Pamphlet JP 2002-43624 A Japanese Patent Laid-Open No. 2002-226846 Japanese Patent No. 3407608

  This invention is made | formed in view of the said subject, The objective is to use a LED chip, and to provide a high-intensity light emitting diode, especially a high-intensity white light emitting diode, and its manufacturing method.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
A light emitting diode having an inorganic phosphor layer that absorbs at least a part of light emitted from the LED chip and converts the wavelength to emit light on the LED chip, and the filling ratio of the inorganic phosphor in the inorganic phosphor layer 60 to 97% of a light emitting diode.

(Claim 2)
The light emitting diode according to claim 1, wherein a filling factor of the inorganic phosphor in the inorganic phosphor layer is 80 to 95%.

(Claim 3)
3. The method for manufacturing a light emitting diode according to claim 1, wherein the inorganic phosphor layer of the light emitting diode is formed by an aerosol deposition method.

  ADVANTAGE OF THE INVENTION According to this invention, a high-intensity light emitting diode, especially a high-intensity white light emitting diode, and its manufacturing method can be provided using an LED chip.

  As a result of intensive studies, the present inventor has a light-emitting diode having an inorganic phosphor layer on the LED chip that absorbs at least part of light emitted from the LED chip and emits light by wavelength conversion. It has been found that a light-emitting diode having a filling ratio of the inorganic phosphor in the layer of 60 to 97% can provide a high-intensity light-emitting diode, particularly a high-intensity white light-emitting diode.

  As a result of studying various thin film forming methods that do not use a resin binder other than the sputtering method, the present inventor has found that an inorganic phosphor thin film (inorganic phosphor layer) formed by an aerosol deposition (AD) method, which is a novel thin film forming method. It has been found to provide high brightness. The film formed by the AD method showed a brightness about several percent higher than that of the equivalent film formed by the sputtering method.

  Although the cause of this is not clear, as a result of various investigations, the film formed by the sputtering method becomes a dense film with a filling rate of 100%, but the film formed by the AD method has a filling rate of about 95%, which is very slight. The presence of voids was confirmed. The minute gaps scatter the excitation light from the LED chip and slightly reduce the extraction of the excitation light from the phosphor thin film. However, since the excitation light density in the thin film increases, the inorganic phosphor layer (hereinafter referred to as phosphor) It is considered that the efficiency of light emission converted by a layer) is increased. As a result of various studies, it has been found that the effect of the present invention can be selectively obtained by setting the filling ratio of the inorganic phosphor in the inorganic phosphor layer to 60 to 97%, and the present invention has been achieved.

  Hereinafter, the light emitting diode of the present invention, in particular, the white light emitting diode and the manufacturing method thereof will be described in detail.

  FIG. 2 is a diagram showing an example of a cross-sectional configuration of the white light emitting diode of the present invention. The LED chip 24 is so-called flip-chip connected, in which a bump electrode 25 is formed on the surface of the semiconductor layer and then turned over and connected to the electrode 23 on the substrate 22. Furthermore, the phosphor layer 26 is formed on the LED chip 24 by a film forming method in which the phosphor particles according to the present invention are deposited by high-speed collision, that is, a so-called aerosol deposition method. As shown in FIG. 2, an embodiment in which a sealing layer 27 made of a transparent inorganic oxide is further formed on the phosphor layer 26 may be employed.

  Another example is shown in FIGS. In this embodiment, the phosphor layer 201 is formed directly on the surface of the semiconductor layer 202 of the LED chip. It is possible to obtain a phosphor layer having a uniform thickness regardless of the unevenness of the LED chip surface. However, it is necessary to protect the electrode wiring portion with a resist in advance and remove the resist and connect (bond) after forming the phosphor layer.

  Hereinafter, the individual components will be described in detail mainly based on the embodiments shown in FIGS.

(LED chip 102)
The LED chip 102 used in the present invention is capable of exciting the phosphor layers 26 and 201. Preferably, a nitride-based compound semiconductor (general formula In _i Ga _j Al _k N, where 0 ≦ i is capable of efficiently emitting ultraviolet light or visible light having a relatively short wavelength capable of efficiently exciting the phosphor layers 26 and 201. , 0 ≦ j, 0 ≦ k, i + j + k = 1) and the like. The LED chip 24 which is a light emitting element forms a semiconductor layer 202 such as InN, AlN, GaN, InGaN, AlGaN, InGaAlN or the like as a light emitting layer on a substrate 203 by MOCVD or the like. Examples of the structure of the semiconductor layer 202 include a homostructure having a MIS junction, a PIN junction, and a PN junction, a heterostructure, or a double hetero configuration. Various emission wavelengths can be selected depending on the material of the semiconductor layer 202 and the degree of mixed crystal thereof. In addition, a single quantum well structure or a multiple quantum well structure in which the semiconductor active layer is formed in a thin film in which a quantum effect is generated can be used.

When a gallium nitride-based compound semiconductor is used, a material such as sapphire, spinel, SiC, Si, ZnO, or GaN is preferably used for the substrate 203. In order to form gallium nitride with good crystallinity, it is more preferable to use a sapphire substrate. When the semiconductor layer 202 is grown on the sapphire substrate, it is preferable to form a gallium nitride semiconductor having a PN junction formed thereon by forming a buffer layer such as GaN or AlN. Further, a GaN single crystal itself selectively grown on a sapphire substrate using SiO ₂ as a mask can be used as the substrate. In this case, the light emitting element and the sapphire substrate can be separated by etching away SiO ₂ after forming each semiconductor layer.

  However, in the case of flip-chip connection as shown in FIG. 2, the substrate is limited to a transparent substrate over the entire visible light region such as a sapphire substrate.

  Gallium nitride-based compound semiconductors exhibit N-type conductivity without being doped with impurities. When forming a desired N-type gallium nitride semiconductor, for example, to improve luminous efficiency, it is preferable to appropriately introduce Si, Ge, Se, Te, C, etc. as an N-type dopant. On the other hand, when a P-type gallium nitride semiconductor is formed, a P-type dopant such as Zn, Mg, Be, Ca, Sr, or Ba is doped. Since a gallium nitride compound semiconductor is difficult to become P-type only by doping with a P-type dopant, it is preferable to make it P-type by heating in a furnace, low-speed electron beam irradiation, plasma irradiation, or the like after introducing the P-type dopant.

  The specific LED chip layer structure includes an N-type contact layer, which is a gallium nitride semiconductor, and an aluminum nitride / gallium semiconductor on a sapphire substrate or silicon carbide having a buffer layer formed of gallium nitride, aluminum nitride or the like at a low temperature. An N-type cladding layer, an active layer that is an indium gallium nitride semiconductor doped with Zn and Si, a P-type cladding layer that is an aluminum / gallium nitride semiconductor, and a P-type contact layer that is a gallium nitride semiconductor Are preferable.

  In the case of an LED chip having a sapphire substrate in order to form an LED chip, after the exposed surfaces of the P-type semiconductor and N-type semiconductor are formed by etching or the like, in the case of the embodiment of FIGS. The phosphor layers 26 and 201 having a desired shape are formed by using the film forming method according to the present invention. Further, a first electrode 204 and a second electrode 205 connected to each conductivity type are formed by a sputtering method, a vapor deposition method, a film forming method of the present invention, or the like. In the case of a SiC substrate, a pair of electrodes can be formed through a semiconductor using the conductivity of the substrate itself.

  Next, the semiconductor wafer on which the phosphor layer is formed is directly fully cut by a dicing saw rotating with a blade having a diamond cutting edge, or a groove having a width wider than the cutting edge width is cut (half cut). The semiconductor wafer is broken by external force. Alternatively, after a very thin scribe line (meridian line) is drawn on the semiconductor wafer by, for example, a grid pattern by a scriber in which the diamond needle at the tip moves reciprocally linearly, the wafer is divided by an external force and cut into chips. Thus, the LED chip 102 which is a nitride compound semiconductor that can be used in the present invention can be formed.

(Phosphor layer)
In the present invention, the filling rate of the inorganic phosphor (hereinafter also referred to as phosphor) in the phosphor layer needs to be 60 to 97%, and more preferably 80 to 95%.

  The filling rate of the phosphor in the phosphor layer is the ratio of the volume occupied by the inorganic phosphor in the phosphor layer. A region that the inorganic phosphor does not occupy in the phosphor layer is a void, and it is relatively easy to measure the volume of the void, so the filling rate is defined by (1−porosity). Specifically, the volume of the void portion is determined and calculated from an electron micrograph of the phosphor layer cross section.

  In order to adjust the filling rate of the phosphor in the phosphor layer to 60 to 97%, various spraying techniques including a plasma spraying method, a gas deposition method, a cold spray method, an aerosol deposition method, and the like can be given. Of these, the aerosol deposition method is preferred in the present invention.

  The phosphor layer used in the present invention refers to phosphor layers 26 and 201 that are excited by light emitted from at least the semiconductor light emitting layer of the LED chip 102 and emit light.

  When the light emitted from the LED chip 102 and the light emitted from the non-particulate phosphor layer are in a complementary color relationship, white light can be emitted by mixing each light.

  Specifically, the light from the LED chip 102 and the light of the phosphor layers 26 and 201 that are excited and emitted by the light are emitted from the three primary colors (red, green, and blue) of the light and the LED chip 102, respectively. Examples thereof include light of the phosphor layers 26 and 201 that emit blue light when excited by blue. By selecting the phosphor type used in the phosphor layers 26 and 201 and the main emission wavelength of the LED chip 102 which is a light emitting element, it is possible to provide an arbitrary color tone such as a light bulb color including white.

  The phosphor layers 26 and 201 excited by light from the LED chip 102 can be variously selected according to light emitted from the LED chip 102 serving as an excitation light source.

(Phosphor composition that can be selected when the main emission peak of the LED chip is 400 to 530 nm)
When the main light emission peak of the LED chip is 400 to 530 nm, the light emission of the LED chip is blue light, and the emission color of the phosphor layer needs to emit broad yellow light when the light emission peak is around 580 nm.

Specific examples of the composition of the phosphor layer include sapphire activated with chromium, yttrium / aluminum / garnet-based phosphor activated with cerium, and erbium (III) oxide. In particular, in a high luminance mode and the long-term use _{(Re 1-x Sm x)} 3 (Al 1-y Ga y) 5 O 12: Ce (0 ≦ x <1,0 ≦ y ≦ 1, however, Re Is at least one element selected from the group consisting of Y, Gd, and La). Particularly phosphor _{(Re 1-x Sm x)} 3 (Al 1-y Ga y) 5 O 12: Ce is preferable.

_{(Re 1-x Sm x)} 3 (Al 1-y Ga y) 5 O 12: Ce phosphor, for garnet structure, heat, resistant to light and moisture, the peak of the excitation spectrum be the 470nm near the like Can do. In addition, the emission peak is in the vicinity of 580 nm, and a broad emission spectrum that extends to 720 nm can be provided. Moreover, the emission wavelength is shifted to a short wavelength by substituting part of Al of the composition with Ga, and the emission wavelength is shifted to a long wavelength by substituting part of Y of the composition with Gd. In this way, it is possible to continuously adjust the emission color by changing the composition. Therefore, it has ideal conditions for converting blue light emission of a nitride compound semiconductor capable of emitting light with high brightness into white light emission, such as the intensity on the long wavelength side being continuously changed by the composition ratio of Gd. ing.

  This phosphor uses oxides, or compounds that easily become oxides at high temperatures, as raw materials for Y, Gd, Ce, Sm, Al, La, and Ga, and mix them well in a stoichiometric ratio. Get raw materials. Alternatively, a coprecipitated oxide obtained by firing a solution obtained by coprecipitation of a solution obtained by dissolving a rare earth element of Y, Gd, Ce, or Sm in an acid at a stoichiometric ratio with oxalic acid, and aluminum oxide or gallium oxide. Mix to obtain a mixed raw material. An appropriate amount of fluoride such as ammonium fluoride is mixed with this as a flux and pressed to obtain a molded body. The molded body is packed in a crucible and fired in air at a temperature range of 1350 to 1450 ° C. for 2 to 5 hours to obtain a sintered body having the light emission characteristics of a phosphor.

(Phosphor composition that can be selected when the main emission peak of the LED chip is 400 nm or less)
When the emission wavelength of the LED chip is 250 to 400 nm, the excitation light from the LED chip is ultraviolet light, and the phosphor can constitute white in various combinations, but the so-called three primary colors blue phosphor, green fluorescence It is desirable that white is constituted by a combination of the body and the red phosphor.

  The blue phosphor has an emission peak wavelength of 400 to 500 nm, the green phosphor has an emission peak wavelength of 500 to 600 nm, and the red phosphor has an emission peak wavelength of 600 to 800 nm. Peaks of excitation spectra of all phosphors Is preferably 250 to 400 nm.

As a specific example, in blue phosphor, Sr ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu ²⁺ , CaS: Bi, CaSrS: Bi, Ba _1-a Eu _a MgAl ₁₀ O ₁₇ , in green phosphor, ZnS : Cu, Al, Ba ₂ SiO ₄ : Eu, ZnGe ₂ O ₄ : Eu, and red phosphor, Y ₂ O ₂ S: Eu ³⁺ , CaS: Eu, 3.5MgO · 0.5MgF ₂ · GeO ₂ : Mn, K ₅ Eu2.5 (WO ₄ ) _{6.25 and the} like.

In addition to the phosphor, a transparent inorganic oxide may be mixed in the phosphor layer according to the present invention. Examples of the transparent inorganic oxide that can be used in the present invention include SiO ₂ and Al ₂ O ₃ .

(Method for forming phosphor layer)
In the present invention, the phosphor layer is formed by using a so-called aerosol deposition method in which a fine particle of a phosphor as a raw material or a fine particle of a transparent inorganic oxide collides with an LED chip as a substrate at high speed to form a film.

  As a film forming apparatus based on the aerosol deposition method, a configuration disclosed in “Applied Physics”, Vol. 68, No. 1, page 44, JP-A-2003-215256, etc. can be used.

  FIG. 1 is a schematic configuration diagram of an aerosol deposition film forming apparatus used in the present invention. The aerosol deposition film forming apparatus includes a holder 9 for holding a substrate 10, an XYZθ stage 11 for operating the holder three-dimensionally with XYZθ, a nozzle 8 having a narrow opening for ejecting a raw material to the substrate, an aerosol forming chamber 4 for the nozzle, The chamber 7 includes a connecting pipe 6, the high-pressure gas cylinder 1 for storing the carrier gas, the aerosol forming chamber 4 in which the fine particle raw material 12 and the carrier gas are stirred and mixed, and the connecting pipe 2 connecting them. A temperature control mechanism using a Peltier element is installed on the back surface of the stage, and the substrate can be maintained at an optimum temperature.

  Further, the fine particle raw material in the aerosol chamber is formed on the LED chip as the substrate by the following procedure.

  A fine particle material having a particle size of preferably 0.02 to 5 μm, more preferably 0.1 to 2 μm, filled in the aerosolization chamber, is introduced into the aerosolization chamber through a pipe from a high-pressure gas cylinder storing a carrier gas. Together with the carrier gas, it is agitated and agitated.

  Examples of the particle size measuring method of the raw material particles include a general laser diffraction type particle size measuring device. Specifically, HELOS (manufactured by JEOL), Microtrac HRA (manufactured by Nikkiso Co., Ltd.), SALD-1100 (Shimadzu Corporation) And Coulter Counter (manufactured by Beckman Coulter). Particularly preferred is Microtrac HRA.

  The aerosolized fine particle raw material passes through a pipe and is sprayed together with a carrier gas from a nozzle having a narrow opening in the chamber to form a coating film. The chamber is evacuated by a vacuum pump or the like, and the degree of vacuum in the chamber is adjusted as necessary. In the present invention, the degree of vacuum is preferably 0.01 to 10000 Pa, more preferably 0.1 to 1000 Pa. Hereinafter, since the holder of the substrate can be moved three-dimensionally by the XYZθ stage, a phosphor layer having a necessary thickness can be formed on a predetermined portion of the substrate. If necessary, a sealing layer can be provided on the phosphor layer formed on the substrate.

  The aerosolized raw material particles are preferably transported by a carrier gas having a flow rate of 100 to 400 m / sec, and can be deposited by colliding with the substrate. The particles carried by the carrier gas are bonded to each other by impact of collision to form a film.

  In the manufacturing method of the present invention, an inert gas such as nitrogen gas or He gas is preferable as the carrier gas for accelerating / spouting the raw material particles. Nitrogen gas can be particularly preferably used.

  Moreover, it is preferable to hold | maintain the temperature of the board | substrate with which raw material microparticles | fine-particles collide between -100 degreeC-200 degreeC. When the substrate temperature is heated to 300 ° C. or higher, the film may become cloudy, and light may not be extracted, resulting in a decrease in brightness of the white LED.

  The formation of the phosphor layer requires at least the fine particles of the phosphor, and may further mix the fine particles of the transparent inorganic oxide as necessary. The aerosol formation chamber of the film forming apparatus is provided for the phosphor and the transparent inorganic oxide, and the phosphor distribution in the phosphor layer can be controlled by appropriately switching the supply materials. The transparent inorganic oxide can control the phosphor concentration in the phosphor layer by appropriately mixing with the phosphor. When a layer of only transparent inorganic oxide is formed on the outermost surface, it can be used as a transparent sealing layer. On the contrary, a layer of only a transparent inorganic oxide may be formed on the LED chip surface. It is also possible to form a layer made only of a phosphor without using a transparent inorganic oxide.

(Conductive wire 103)
The conductive wire 103 is required to have good ohmic properties, mechanical connectivity, electrical conductivity and thermal conductivity with the electrodes 204 and 205 of the LED chip 102. Specific examples include conductive wires using metals such as gold, copper, platinum, and aluminum, and alloys thereof. Such a conductive wire 103 can easily connect the electrodes 204 and 205 of each LED chip 102 to the inner lead, the mount lead, and the like by a wire bonding apparatus.

(Package 104)
The package 104 has an external electrode 105 that fixes and protects the LED chip 102 in the recess and can be electrically connected to the outside.

  The package 104 can also be provided with a mold member 106 which is a translucent protector in order to further protect the LED chip 102 from the external environment. The package 104 preferably has high adhesiveness with the mold member 106 and high rigidity. It is desirable to have an insulating property in order to electrically cut off the LED chip 102 and the outside. Furthermore, when the package 104 is affected by heat from the LED chip 102 or the like, it is preferable that the package 104 has a low coefficient of thermal expansion in consideration of adhesion to the mold member 106.

  The package 104 may be formed integrally with the external electrode 105, or the package 104 may be divided into a plurality of parts and combined by fitting or the like. Such a package 104 can be formed relatively easily by injection molding or the like. Examples of the package material include polycarbonate resin, polyphenylene sulfide (PPS), liquid crystal polymer (LCP), ABS resin, epoxy resin, phenol resin, acrylic resin, PBT resin, ceramics, and the like.

  Adhesion between the LED chip 102 and the package 104 can be performed with a thermosetting resin or the like. Specifically, an epoxy resin, an acrylic resin, an imide resin, etc. are mentioned. Further, Ag paste, carbon paste, ITO paste, metal bump, or the like is preferably used to place and fix the LED chip 102 and to be electrically connected to the external electrode 105 in the package 104.

(External electrode 105)
The external electrode 105 is used to supply power from the outside of the package 104 to the LED chip 102 disposed inside. There are various types such as a conductive pattern provided on the package 104 and a pattern using a lead frame. The external electrode 105 can be formed in various sizes in consideration of heat dissipation, electrical conductivity, characteristics of the LED chip 102, etc. Specific materials of the external electrode 105 are on the surface of copper or phosphor bronze plate. What gave metal plating, solder plating, etc., such as silver, palladium, or gold | metal | money is used suitably.

(Mold member 106)
The mold member 106 can be provided to protect the LED chip 102, the conductive wire 103, the phosphor layer 101, and the like from the outside according to the use application of the light emitting diode. The mold member 106 can be formed using various resins, glass, and the like. As a specific material of the mold member 106, a transparent resin or glass having excellent weather resistance such as an epoxy resin, a urea resin, or a silicone resin is preferably used.

  The white light emitting diode of the present invention is formed from the above configuration.

  The white light emitting diode of the present invention can emit white light by applying a rated DC load of up to 5 V and 30 mA and emitting light.

  Hereinafter, although an Example demonstrates further more concretely, this invention is not limited to these description.

Example [Production of Light-Emitting Diode]
(Production of light-emitting diode 1)
As the LED chip, an In _0.2 Ga _0.8 N semiconductor having a main emission peak of 460 nm was used. The LED chip is formed by flowing a TMG (trimethylgallium) gas, a TMI (trimethylindium) gas, a nitrogen gas and a dopant gas together with a carrier gas on a cleaned sapphire substrate, and forming a gallium nitride compound semiconductor by MOCVD. Formed. By switching between SiH ₄ and Cp ₂ Mg (cyclopentadienylmagnesium, [Mg (C ₅ H ₅ ) ₂ ]) as dopant gas, gallium nitride semiconductor having N-type conductivity and nitriding having P-type conductivity A gallium semiconductor is formed to form a PN junction. The semiconductor light emitting device includes a contact layer that is an N-type conductivity gallium nitride semiconductor, a cladding layer that is a P-type conductivity gallium aluminum nitride semiconductor, and a contact layer that is a P-type conductivity gallium nitride semiconductor. Formed. An active layer of non-doped InGaN having a single quantum well structure having a thickness of about 3 nm was formed between the contact layer having N-type conductivity and the cladding layer having P-type conductivity. Note that a gallium nitride semiconductor was formed on the sapphire substrate at a low temperature to form a buffer layer. The semiconductor having P-type conductivity was annealed at 400 ° C. or higher after film formation.

  Thereafter, the surface of each PN semiconductor on the sapphire substrate was exposed by etching. Further, there are a plurality of portions where the surface of each PN semiconductor is exposed for each LED chip finally formed. Further, the semiconductor layer is partially removed up to the sapphire substrate so that it can be divided into rectangles according to the size of each LED chip. A resist was formed in advance on the pad electrode forming surface for attaching a gold wire to be a conductive wire to form a semiconductor wafer.

A yellow phosphor layer was formed on the fabricated LED chip using the aerosol deposition film forming apparatus shown in FIG. (Y _0.8 Gd _0.2 ) ₃ Al ₅ O ₁₂ : Ce0.035 phosphor particles having an average particle size of 0.2 μm are filled in an aerosol chamber, N ₂ gas having a flow rate of 200 m / s is used as a carrier gas, and the chamber is vacuumed. The temperature was 100 Pa, the substrate temperature was 20 ° C., and the film was sprayed onto the LED chip to form a film of 2 μm. Thereafter, the resist was removed by lift-off to form a smooth and inorganic phosphor layer only on the desired semiconductor wafer.

  The semiconductor wafer thus formed with the phosphor layer was diced with a dicer along an etching line for dividing the semiconductor wafer into LED chips, and then a scribe line was formed with a scriber. Pressing with a roller along the scribe line from the sapphire substrate side, the LED chip was divided and formed with a phosphor layer.

  Further, a chip type LED package was formed using polycarbonate resin by insert molding. The chip type LED package includes an opening in which the LED chip is disposed. In the package, a silver-plated copper plate is disposed as an external electrode. The LED chip on which the phosphor layer was formed inside the package was fixed using an epoxy resin or the like. Gold wires, which are conductive wires, were wire-bonded to and electrically connected to the electrodes of the LED chip and the external electrodes provided in the package. Thus, 4000 white light emitting diodes 1 of the present invention were produced.

(Production of light-emitting diode 2)
A film having a thickness of 2 μm was formed in the same manner as the light-emitting diode 1 except that (Y _0.8 Gd _0.2 ) ₃ Al ₅ O ₁₂ : Ce0.035 phosphor particles having an average particle diameter of 0.4 μm were used. 4000 white light emitting diodes 2 were produced.

(Production of light-emitting diode 3)
The same procedure as in the production of the light-emitting diode 1 except that (Y _0.8 Gd _0.2 ) ₃ Al ₅ O ₁₂ : Ce 0.035 phosphor particles having an average particle size of 0.9 μm were used and N ₂ gas having a flow rate of 170 m / s was used. Film formation of 2 μm was performed, and 4000 white light-emitting diodes 3 of the present invention were produced.

(Production of light-emitting diode 4)
The phosphor layer is formed by fabricating the light-emitting diode 1 except that a coating portion obtained by mixing (Y _0.8 Gd _0.2 ) ₃ Al ₅ O ₁₂ : Ce0.035 phosphor in an epoxy resin is formed on the LED chip. In the same manner, 4000 white light emitting diodes 4 of the comparative example were manufactured.

(Production of light-emitting diode 5)
In order to form a phosphor layer, a solution obtained by dissolving rare earth elements of Y, Gd, and Ce in acid at a stoichiometric ratio was coprecipitated with oxalic acid. A co-precipitated oxide obtained by baking this and aluminum oxide were mixed to obtain a mixed raw material. This was mixed with ammonium fluoride as a flux, and a molded body was formed at 400 N / cm ² in 5 seconds. The molded body was packed in a crucible and fired in air at 1350 ° C. for 3 hours to obtain a fired product.

After the end surface of the fired product was cut so as to be _{smooth, (Y 0.8 Gd 0.2) 3} Al 5 O 12: using as a target having a Ce0.035 phosphor composition. A target and an LED chip were fixed in a vacuum chamber of a bipolar sputtering apparatus. Argon gas was allowed to flow through the vacuum chamber of the sputtering apparatus, and an AC voltage was applied to each electrode. A voltage was applied to form a 2 μm phosphor film on the LED chip. Except for the formation of the phosphor layer, 4000 white light-emitting diodes 5 of comparative examples were produced in the same manner as the production of the light-emitting diodes 1.

[Measurement and evaluation]
(Measurement of filling rate)
The volume of the void was determined from the electron micrograph of the phosphor layer cross section and calculated. Specifically, the void portion was identified from the difference in density of the cross-sectional images, and a rough filling ratio was obtained from the cross-sectional area ratio with the phosphor portion. Fifty sections of the phosphor cross section were prepared, and the cross-sectional area ratio was averaged to calculate the phosphor filling rate.

  For the light-emitting diode 2, a larger amount of sections were prepared, and the filling rate was measured with a mercury porosimeter. The filling rate values obtained by the electron microscope method and the porosimeter method agreed with two-digit accuracy.

(Evaluation of white light intensity, 460 nm peak intensity, 560 nm peak intensity)
The obtained light emitting diode was made to emit light by supplying power, and the white light intensity (integrated value of 400 to 800 nm), the emission intensity of 460 nm, and the emission intensity of 560 nm were evaluated from the front of the light emitting diode.

(Evaluation of luminescence variation)
The obtained light emitting diode was made to emit light by supplying electric power, color temperature and color rendering were measured from the front of the light emitting diode, and the variation was measured as an area on the chromaticity coordinate.

  The white light intensity, the 460 nm peak intensity, the 560 nm peak intensity, and the variation are shown as relative values with the light emitting diode 5 being 1.00. The results of measurement and evaluation are shown in Table 1.

  From Table 1, it can be seen that the light-emitting diodes of the present invention are superior in white light intensity and have less emission variation than the comparative example.

It is a schematic block diagram of an aerosol deposition film-forming apparatus. It is an example of the cross-sectional structure of the white light emitting diode of this invention. It is a schematic diagram of the LED chip which is the light emitting diode of this invention, FIG. 3 (A) is typical sectional drawing, FIG.3 (B) is a schematic front view. It is typical sectional drawing of chip type LED which is a light emitting diode of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High pressure gas cylinder 2, 6 Piping 3, 5 Valve 4 Aerosolization chamber 7 Chamber 8 Nozzle 9 Holder 10, 22, 203 Substrate 11 XYZθ stage 12 Fine particle raw material 21 White LED
22, 203 Substrate 23 Electrode 24, 102 LED chip 25 Bump electrode 26, 201 Phosphor layer 27 Sealing layer 100 Chip type LED
101, 201 Non-particulate inorganic phosphor layer 103 Conductive wire 104 Package 105 External electrode 106 Mold member 202 Semiconductor layer 204 First electrode connected to semiconductor layer having N-type conductivity 205 P-type conductivity Second electrode connected to semiconductor layer having

Claims (3)

A light emitting diode having an inorganic phosphor layer that absorbs at least a part of light emitted from the LED chip and converts the wavelength to emit light on the LED chip, and the filling ratio of the inorganic phosphor in the inorganic phosphor layer 60 to 97% of a light emitting diode. The light emitting diode according to claim 1, wherein a filling factor of the inorganic phosphor in the inorganic phosphor layer is 80 to 95%. 3. The method for manufacturing a light emitting diode according to claim 1, wherein the inorganic phosphor layer of the light emitting diode is formed by an aerosol deposition method.

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