JP5338688B2 - Method for manufacturing light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a light-emitting device preventing coloring of glass. <P>SOLUTION: In the method of manufacturing the light-emitting device by mounting a light-emitting element 2 on an element mounting substrate 3 and sealing the light-emitting element 2 on the element mounting substrate 3 with heated glass 51, the light-emitting element 2 is sealed in an atmosphere of inert gas containing oxygen, thereby preventing a reduction action of the glass 51 during sealing. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing a light emitting device in which a light emitting element of a group III nitride semiconductor is sealed with glass.

  Patent Documents 1 and 2 disclose light-emitting devices using glass instead of a resin such as epoxy as a member for sealing a group III nitride semiconductor light-emitting element. When glass is used as the sealing material, the difference in thermal expansion coefficient between the sealing material and the light-emitting element can be reduced, and the lifetime of the light-emitting device can be extended. In Patent Documents 1 and 2, the light emitting element is sealed by heating glass in a nitrogen atmosphere.

International Publication No. 2004/82036 JP 2006-156668 A

  However, when glass sealing is performed in a nitrogen atmosphere, the oxygen component is released from the glass surface due to the reducing action at high temperature, and a phenomenon may occur in which coloring occurs on the glass surface or the joint between the glass and the element mounting substrate. is there. When the glass is colored, the light extraction efficiency of the light emitting device is lowered.

  This invention is made | formed in view of the said situation, The place made into the objective is to provide the manufacturing method of the light-emitting device which can suppress coloring of glass.

To achieve the above object, n-type layer made of a Group III nitride semiconductor, light emitting layer, p-type cladding layer, a light-emitting element manufactured by growing a p-type contact layer mounted on the element mounting substrate, the light emitting element the method for manufacturing a light emitting device sealed with glass which is heated, forming the p-type contact layer is higher than the growth temperature of the light emitting layer is performed at a growth temperature of less than 1000 ° C., sealing of the light emitting element There is provided a method for manufacturing a light emitting device that is stopped in a gas atmosphere containing oxygen by hot pressing using a mold made of an oxidation resistant material.

In the method for manufacturing a light emitting device, the glass is ZnO-based glass, Bi ₂ O ₃ -based glass, P ₂ O ₅ -based glass, Nb ₂ O ₅ -based glass, GeO ₂ -based glass, Ga ₂ O ₃ -based glass, Y ₂ O ₃ glass, La ₂ O ₃ glass, Gd ₂ O ₃ glass, or Ta ₂ O ₅ glass may be used.

  In the method for manufacturing the light emitting device, the element mounting board may be made of a polycrystalline ceramic material.

  In the method for manufacturing a light emitting device, the glass may include diffusing particles.

  In the manufacturing method of the light-emitting device, the light-emitting element may be sealed by melting and solidifying powdered glass.

In the method for manufacturing the light emitting device, the pre-Symbol p-type contact layer, Mg concentration may form 2 × ^{10 19} or more 8 × ¹⁰ 19 / cm ³ or less and so as.

  According to the present invention, coloring of glass after glass sealing can be suppressed.

FIG. 1 is a cross-sectional explanatory view of a light emitting device showing an embodiment of the present invention. FIG. 2 is a diagram illustrating the configuration of the LED element. FIGS. 3A and 3B are explanatory views of the fabrication state of the LED element, in which FIG. 3A shows a state in which a semiconductor layer is formed on a substrate, FIG. 3B shows a state in which a transparent electrode is formed, and FIG. The state which formed the pad electrode and the n electrode is shown. FIG. 4 is an explanatory diagram of a method for manufacturing a light emitting device showing a state before glass sealing. FIG. 5 is an explanatory diagram of a method for manufacturing a light emitting device showing a state after glass sealing. FIG. 6 shows a modification and is an explanatory view of a method for manufacturing a light-emitting device showing a state before glass sealing. FIG. 7 shows a modification and is an explanatory view of a method for manufacturing a light-emitting device showing a state after glass sealing. FIG. 8 shows a modification and is an explanatory view of a method for manufacturing a light emitting device showing a state before glass sealing. FIG. 9 shows a modified example and is an explanatory diagram of a method for manufacturing a light emitting device showing a state after glass sealing. FIG. 10 is a graph showing the relationship between the oxygen concentration during glass sealing and the difference in driving voltage of the LED element before and after glass sealing. FIG. 11 shows the Mg concentration of the first p-type contact layer and the second p-type contact layer of the LED element after glass sealing, and the difference in drive voltage between the LED elements before and after glass sealing at the time of 20 mA energization. It is a graph which shows the relationship. FIG. 12 is a graph showing the relationship between the Mg concentration of the first p-type contact layer and the second p-type contact layer of the LED element before glass sealing and the drive voltage of the LED element when 20 mA is energized. FIG. 13 is a graph showing the relationship between the growth temperature of each p-type contact layer and the drive voltage increase due to heat treatment.

  1 to 5 show an embodiment of the present invention, and FIG. 1 is a cross-sectional explanatory view of a light emitting device.

As shown in FIG. 1, the light emitting device 1 includes an LED element 2 made of a flip-chip group III nitride semiconductor, an element mounting substrate 3 on which the LED element 2 is mounted, an LED element 2 and an element mounting. It has the glass sealing part 5 as an inorganic sealing part adhere | attached on the board | substrate 3. FIG. Here, the group III nitride semiconductor is represented by a general formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). . The element mounting board 3 on which the circuit pattern 4 is formed is made of a polycrystalline sintered material of alumina (Al ₂ O ₃ ), and is formed in a 1.0 mm square with a thickness of 0.25 mm. The LED element 32 is 100 μm thick and 346 μm square. In the light emitting device 1, when a voltage is applied to the LED element 2, blue light is emitted from the LED element 2, and the blue light is emitted from the glass sealing portion 5 to the outside.

The element mounting board 3 is made of a polycrystalline sintered material of alumina (Al ₂ O ₃ ), has a thickness of 0.25 mm and a 1.0 mm square, and has a thermal expansion coefficient α of 7 × 10 ⁻⁶ / ° C. It is. The LED element 2 has a thickness of 100 μm and a 346 μm square, and has a thermal expansion coefficient of 7 × 10 ⁻⁶ / ° C. Here, although the thermal expansion coefficient of the GaN layer of the LED element 2 is 5 × 10 ⁻⁶ / ° C., the thermal expansion coefficient of the growth substrate made of sapphire occupying most is 7 × 10 ⁻⁶ / ° C., The thermal expansion coefficient of the LED element 2 body is equal to the thermal expansion coefficient of the growth substrate.

  The circuit pattern 4 includes a via pattern 41 formed in the via hole 6 of the element mounting substrate 3, a surface pattern 42 formed on the surface of the element mounting substrate 3 and electrically connected to the LED element 2, and the element mounting substrate 3. A back surface pattern 43 that is formed on the back surface and can be connected to an external terminal is continuously provided. The via pattern 41 can be made of W, and the front surface pattern 42 and the back surface pattern 43 can have, for example, a three-layer structure of a W layer, a Ni layer, and an Au layer. The LED element 2 mounted on is disposed so as to be sandwiched in plan view. In the present embodiment, the two via holes 6 are arranged so as to sandwich the LED element 2 in a direction parallel to one side of the element mounting substrate 3 (opposite side direction).

FIG. 2 is an explanatory diagram of the configuration of the LED element 2.
As shown in FIG. 2, the LED element 2 includes a buffer layer 21, an n-type contact layer 22, and the like by epitaxially growing a group III nitride semiconductor on the surface of a substrate 20 made of sapphire (Al ₂ O ₃ ). The n-type ESD layer 23, the n-type cladding layer 24, the MQW layer 25, the p-type cladding layer 26, the first p-type contact layer 27, and the second p-type contact layer 28 are formed in this order. Yes. The LED element 2 includes a transparent electrode 11 provided on the second p-type contact layer 27 and a p-pad electrode 12 formed on the transparent electrode 11. Further, the LED element 2 has an n electrode 13 formed on the n-type contact layer 22 exposed by etching a part from the second p-type contact layer 27 to the n-type contact layer 22. Furthermore, the upper surface of the LED element 2 is covered with a protective film 14 except for the outer edges of the p-pad electrode 12 and the n-electrode 13. The p pad electrode 12 and the n electrode 13 are electrically connected to the surface pattern 41 of the circuit pattern 4 through the bumps 7.

In the present embodiment, the buffer layer 21 is made of AlN, the n-type contact layer 22 is made of n ⁺ -GaN, and the n-type ESD layer 23 is made of GaN / n-GaN. The n-type cladding layer 24 is configured by repeatedly laminating InGaN / GaN / n-GaN, the MQW layer 25 is configured by repeatedly laminating InGaN / GaN, and the p-type cladding layer 26 is composed of p-InGaN / GaN. It is configured by repeatedly stacking p-AlGaN. The first and second p-type contact layers 27 and 28 are made of p-GaN, and the Mg concentration of the second p-type contact layer 28 is 1.5 to 3 times that of the first p-type contact layer 27. Here, it is desirable that the thickness of the first p-type contact layer 27 is 50 nm to 200 nm and the thickness of the second p-type contact layer 28 is 5 nm to 15 nm. The transparent electrode 11 is made of ITO (Indium Tin Oxide), the p pad electrode 12 is made of Ni / Au, and the n electrode 13 is made of Ni / Au, Al, or the like.

The glass sealing part 5 covers the LED element 2 mounting surface side of the element mounting substrate 3 together with the LED element 2 and has a thickness of 0.6 mm. The glass sealing portion 5 has an upper surface 5a parallel to the element mounting substrate 33, and a side surface 5b extending downward from the outer edge of the upper surface 5a and perpendicular to the element mounting substrate 3. In the present embodiment, the glass sealing portion 5 is, for example, ZnO—B ₂ O ₃ —SiO ₂ glass, and has a refractive index of 1.7. The composition of the glass is not limited to this, and for example, the glass may contain Nb ₂ O ₅ in order to obtain a high refractive index, or may contain TiO ₂ , Al ₂ O ₃ or the like. In order to lower the melting point, Na ₂ O, Li ₂ O and the like may be contained. Furthermore, ZrO ₂ , TiO ₂ or the like may be included as an optional component. Further, the glass can contain phosphor particles such as YAG (Yttrium Aluminum Garnet), silicic acid-based, nitride-based, and sulfide-based materials, and diffusing particles due to crystals. In addition, since the phosphor particles also have a diffusing action, they can be referred to as diffusing particles. Further, this glass is a heat-sealed glass fused to the element mounting substrate 3 by heating, and is different from a glass formed by utilizing a sol-gel reaction. The composition and refractive index of the glass are not limited to these.

The light emitting device 1 is manufactured through the following steps.
In producing the LED element 2, first, the substrate 20 is prepared. Then, as shown in FIG. 3A, a buffer layer 21, an n-type contact layer 22, an n-type ESD layer 23, an n-type cladding layer 24, MQW are formed on the substrate 20 by MOCVD (Metal Organic Chemical Vapor Deposition). The layer 25, the p-type cladding layer 26, the first p-type contact layer 27, and the second p-type contact layer 28 are sequentially stacked. Source gases include TMG (trimethylgallium) as a Ga source, TMA (trimethylaluminum) as an Al source, TMI (trimethylindium) as an In source, ammonia as an N source, silane as a Si source of an n-type dopant, and p-type Cp ₂ Mg (biscyclopentadienyl magnesium) can be used as the Mg source of the dopant. The first p-type contact layer 27 and the second p-type contact layer 28 of the LED element 2 are formed with a growth temperature of 780 ° C. or more and 1000 ° C. or less and an Mg concentration of 2 × 10 ¹⁹ or more and 8 × 10 ¹⁹ or less. Specifically, the growth temperature is 840 ° C. to 900 ° C. for the n-type ESD layer 23, 800 ° C. to 900 ° C. for the n-type cladding layer 24, 770 ° C. to 900 ° C. for the MQW layer 25, and the p-type cladding layer 26. Can be 800 ° C. or higher and 900 ° C. or lower.

  Next, as shown in FIG. 3B, ITO (Indium Tin Oxide) is deposited on the second p-type contact layer 28 at 420 ° C. or higher and 460 ° C. or lower and baked at 640 ° C. or higher and 690 ° C. or lower in an oxygen atmosphere. The transparent electrode 11 is formed in a predetermined shape by photolithography and wet etching. In this embodiment, the p-type impurity is activated in the steps of vapor deposition and baking of the transparent electrode 11, but the p-type impurity may be activated by performing heat treatment before vapor deposition of the transparent electrode 11.

  Thereafter, as shown in FIG. 3C, a mask having a predetermined shape is formed on the transparent electrode 11 and ICP (Inductively Coupled Plasma) etching is performed to expose the n-type contact layer 22. Then, the p-pad electrode 12 is formed on the transparent electrode 11 and the n-electrode 13 is formed on the n-type contact layer 22 exposed by etching, and an alloy process is performed. Thereafter, the protective film 14 is formed on the upper surface of the group III nitride semiconductor layer other than the outer edge portions of the p pad electrode 12 and the n electrode 13 and separated into individual LED elements 2 by dicing. The LED element 2 is produced through the above steps.

  Moreover, in producing the pre-sealing glass 51 that forms the glass sealing portion 5, the glass component oxide powder is heated to 1200 ° C. and stirred in a molten state. And after solidifying glass, it slices so that it may correspond to the thickness of the glass sealing part 5, and the glass 51 before sealing is processed into plate shape. In addition, you may form the recessed part corresponding to each LED element 2 in the glass 51 before sealing.

  On the other hand, the circuit pattern 4 is formed on the flat element mounting substrate 3. For example, the circuit pattern 4 is obtained by screen-printing a metal paste and baking the element mounting substrate 3 on the element mounting substrate 3 by heat-treating the element mounting substrate 3 at a predetermined temperature (for example, 1000 ° C. or higher), It can form by performing plating of.

  Thereafter, the plurality of LED elements 2 are mounted on the element mounting substrate 3 at equal intervals in the vertical and horizontal directions by flip chip connection via the bumps 7. The circuit pattern 4 of the element mounting substrate 3 may be formed only by a heat treatment of a metal paste, or may be formed by other methods such as a metal plating after metal sputtering.

  Then, as shown in FIG. 4, the element mounting substrate 3 on which each LED element 2 is mounted is set on the lower mold 91, and the upper mold 92 is disposed to face the mounting surface of the element mounting substrate 3. The pre-sealing glass 51 is disposed between the mounting substrate 3 and the upper mold 92 so that the mounting area of each LED element 2 is covered. Here, at least the surfaces of the lower mold 91 and the upper mold 92 are made of an oxidation resistant material, and are not oxidized even when heated in an oxidizing atmosphere. As an oxidation-resistant material, for example, stainless steel or tungsten carbide is used as a base material, and an inert metal such as platinum, gold, or rhodium, titanium-based nitride (for example, TiN-based, TiAlN-based, TiCN-based, etc.), chromium is used on the surface. Examples thereof include those having a compound coating such as a system nitride (for example, CrN system) and TaC.

  In addition, when there is no surface coating with an oxidation resistant material, it is not impossible to manufacture a light emitting device, but as the upper mold oxidation proceeds, chemical bonding with glass via an oxygen compound tends to occur, The surface is roughened. Eventually, glass is bonded to the upper mold and it becomes impossible to release the mold, which is not suitable for mass production.

  Thereafter, as shown in FIG. 5, the lower mold 91 and the upper mold 92 are pressurized, and hot pressing of the glass material softened by heating in an oxygen-containing nitrogen atmosphere is performed. At this time, in order to prevent bubbles remaining in the glass material after processing, the atmosphere is effective at 380 Torr or less, and preferably 76 Torr or less. Further, the atmosphere containing oxygen is not limited to nitrogen, but it is necessary to use an inert gas in order to prevent oxidation of the LED element 2 and the element mounting substrate 3. The volume% of oxygen in the inert gas is preferably 20% or less, and more preferably 5% or less.

  Through the above steps, the intermediate body 80 in a state where the plurality of light emitting devices 1 are connected is manufactured. Thereafter, the element mounting substrate 3 integrated with the glass sealing portion 5 is set in a dicing apparatus, and the glass sealing portion 5 and the element mounting substrate 3 are diced by the dicing blade so as to be divided for each LED element 2. Thus, the rectangular parallelepiped light emitting device 1 is completed.

  According to the light emitting device 1 manufactured as described above, since the glass sealing is performed in an atmosphere containing oxygen, the glass sealing portion 5 is not colored by the reducing action, and the LED element 2 Even if the emitted light is multiple-reflected for the following reason and then radiates externally from the light emitting device 1, it is possible to suppress a decrease in light extraction efficiency due to coloring. Multiple reflection occurs when the LED element 1 is incident on the glass interface at an angle equal to or greater than the critical angle of the glass, and is incident on the interface between the element mounting substrate 3 and the glass (especially when the element mounting substrate 3 is a polycrystalline material, The glass interface shape is uneven at the grain boundaries, and the number of multiple reflections increases beyond the plane), and there are diffusing particles (including phosphors) in the glass. This occurs when the light enters the interface or the interface between the element mounting substrate 3 and the glass. Further, since the lower mold 91 and the upper mold 92 are made of an oxidation resistant material, they are not oxidized, and deterioration due to oxidation of the mold and a decrease in productivity can be prevented.

Moreover, since glass sealing was performed in an atmosphere containing oxygen, an increase in driving voltage after glass sealing can be effectively suppressed. Furthermore, regarding the first p-type contact layer 27 and the second p-type contact layer 28 of the LED element 2, by setting the Mg concentration to 2 × 10 ¹⁹ or more and 8 × 10 ¹⁹ or less and the growth temperature to 780 ° C. or more and 1000 ° C. or less, The effect of suppressing an increase in drive voltage is increased.

In manufacturing the light emitting device 1, a plurality of LED element 2 samples are prepared in advance, and the growth temperature of each p-type contact layer 27, 28 and Mg based on the measurement result of the driving voltage of each sample. The density can be set. Hereinafter, the procedure in this case will be described. In this case, in each sample, the growth temperature of the p-type contact layers 27 and 28 is changed in the range of 780 ° C. or more and 1000 ° C. or less, and the Mg concentration is changed in the range of 2 × 10 ¹⁹ or more and 8 × 10 ¹⁹ or less. Make it. Then, the initial drive voltage of each of the fabricated samples is measured, and the Mg concentration and growth of the first p-type contact layer 27 of the sample in which the initial drive voltage is low and stable and pits that are lattice defects are not generated. The temperature is determined as the standard Mg concentration and the standard growth temperature.

  In the actual manufacture of the light emitting device 1, the LED element 2 is manufactured by the same manufacturing process as the sample except for the process of forming the p-type contact layers 27 and 28. Regarding the formation of the first p-type contact layer 27 and the second p-type contact layer 28, the growth temperature is set to a range of (standard growth temperature−50 ° C.) to the standard growth temperature, and the Mg concentration of the first p-type contact layer 27 is standard. It forms so that it may become 0.6 to 1.0 times of Mg concentration.

  More preferably, the growth temperature of the first p-type contact layer 27 and the second p-type contact layer 28 is set to a critical growth temperature, and the Mg concentration of the first p-type contact layer 27 is set to a critical Mg concentration. The critical growth temperature is a temperature at which the drive voltage rise due to glass sealing starts when the growth temperature of the sample of the LED element 2 is raised. The critical Mg concentration is the Mg concentration at which the initial driving voltage starts to increase when the Mg concentration of the sample of the LED element 2 described above is reduced. However, considering the measurement error, the growth temperature is in the range of 0.9 to 1.1 times the critical growth temperature, and the Mg concentration is in the range of 0.9 to 1.1 times the critical Mg concentration. Also good.

  Moreover, in the said embodiment, although what pre-shaped glass 51 before sealing from glass powder was previously shape | molded was shown, as shown, for example in FIG. 6, the glass 52 before sealing is powdery. There may be. In FIG. 6, after the LED element 2 is mounted on the element mounting board 3, powdery glass is filled on the element mounting board 3. Thereafter, the glass is heated to soften the glass powder and, as shown in FIG. 7, the glass 80 is pressed with the upper mold 92, whereby the intermediate body 80 similar to the above embodiment can be produced. . When powdered glass is used in this way, the surface area of the glass increases, so that it is easy to color. However, by performing glass sealing in the above-described reduced-pressure atmosphere, residual bubbles can be reduced and high permeability can be maintained.

  Furthermore, for example, as shown in FIGS. 8 and 9, the glass may be melted and solidified without pressing. In FIG. 8, wall portions 31 that partition the LED elements 2 are provided on the element mounting surface of the element mounting substrate 3, and the powder of the phosphor 53 and the glass 52 before sealing are formed in the space formed by the wall portions 31. Filled with powder. Then, by heating and solidifying the pre-sealing glass 52, the LED element 2 can be sealed by the glass sealing portion 5 in which the phosphor 53 is dispersed, as shown in FIG.

  As the phosphor 53, for example, a YAG (Yttrium Aluminum Garnet) phosphor, a silicate phosphor, or a mixture of YAG and a silicate phosphor at a predetermined ratio can be used. By combining them, white light can be obtained. In addition, you may make it obtain white light by the combination of the LED element which emits ultraviolet light, and a blue fluorescent substance, a green fluorescent substance, and a red fluorescent substance. Further, the glass sealing portion 5 may be made by applying a phosphor to the surface of the glass sealing portion 5 without containing the phosphor 53.

Further, in the above embodiment has been described by way of _ZnO-B 2 O 3 -SiO ₂ based glass which is a kind of ZnO-based glass as a sealing glass, may be another ZnO-based glass, Bi ₂ O ₃ glass, P ₂ O ₅ glass, Nb ₂ O ₅ glass, GeO ₂ glass, Ga ₂ O ₃ glass, Y ₂ O ₃ glass, La ₂ O ₃ glass, Gd ₂ O ₃ system Even if it is glass, Ta ₂ O ₅ type glass, etc., the same effect as the above-mentioned embodiment can be acquired. Examples of the ZnO-based glass include a ZnO—B ₂ O ₃ —SiO ₂ system, a ZnO—B ₂ O ₃ —TeO ₂ system, a ZnO—SiO—R ₂ O system (R: at least selected from group I elements) 1 type). The Bi ₂ O ₃ based glass, for _{example, Bi 2 O 3 -B 2 O} 3 -SiO 2 _{system, Bi 2 O 3 -B 2 O} 3 -TeO 2 _{system, Bi 2 O 3 -SiO-R} 2 O system (R: at least one selected from Group I elements). The P ₂ O ₅ based glass, for _example, P ₂ O 5 _-ZnO-based, can be mentioned P ₂ O 5 _-Al 2 _{O 3} system, and the like. The Nb ₂ O ₅ based glass, for _example, a Nb ₂ O 5 -SiO ₂ system, and the like.
Further, the protective film 14 of the LED element 2 may be omitted. In this case, an increase in drive voltage can be further suppressed.

Further, in the above embodiment shows what the element mounting substrate 3 made of alumina (Al 2 _{O 3),} may be formed from a ceramic other than alumina. Here, as a ceramic substrate made of a high thermal conductivity material that is more excellent in thermal conductivity than alumina, for example, BeO (thermal expansion coefficient α: 7.6 × 10 ⁻⁶ / ° C., thermal conductivity: 250 W / (m · k) ) May be used. Even in the substrate made of BeO, good sealing properties can be obtained by the pre-sealing glass.
Furthermore, for example, a W—Cu substrate may be used as another highly heat conductive substrate. As a W-Cu substrate, a W90-Cu10 substrate (thermal expansion coefficient α: 6.5 × 10 ⁻⁶ / ° C., thermal conductivity: 180 W / (m · k)), a W85-Cu15 substrate (thermal expansion coefficient α: By using 7.2 × 10 ⁻⁶ / ° C. and thermal conductivity: 190 W / (m · k)), it is possible to impart high thermal conductivity while ensuring good bonding strength with the glass sealing portion. Therefore, it is possible to cope with an increase in the amount of light and output of the LED with a margin.

  Moreover, in the said embodiment, although the LED element 2 was made into the flip chip type, the LED element of other structures, such as a face-up type and the structure which provided the electrode up and down, may be sufficient. Furthermore, although the LED element is illustrated as a light emitting element, a light emitting element is not limited to an LED element, Of course, it can be changed suitably also about a specific detailed structure.

[Example 1]
FIG. 10 is a graph showing the relationship between the oxygen concentration during glass sealing and the difference in driving voltage of the LED element before and after glass sealing. In acquiring the data of FIG. 10, the growth temperature of the first p-type contact layer 27 and the second p-type contact layer 28 of the LED element 2 is set to 1000 ° C., and the Mg concentration is set to 9.8 × 10 ¹⁹ / cm ³ . A plurality of sample bodies of the light emitting device 1 were manufactured by changing the oxygen gas concentration in the nitrogen gas as the inert gas. Specifically, the light-emitting device 1 was manufactured by changing the oxygen gas concentration to 0%, 0.3%, and 1.0%, and the driving voltage at the time of energizing 20 mA was measured.

  As shown in FIG. 10, in the sample body in which the oxygen gas concentration was 0%, the driving voltage increased by 0.6 V before and after glass sealing, but in the sample body in which the oxygen gas concentration was 0.3%. As a result, the drive voltage was suppressed from increasing. Furthermore, it was confirmed that when the oxygen gas concentration was 1.0%, the drive voltage increased to 0.1 V, and the drive voltage increase was significantly suppressed. Therefore, it can be understood that if oxygen gas is contained, an increase in driving voltage is suppressed, and that the effect is great when the oxygen gas concentration is 1.0% or more. Further, in each comparative example described later, when the oxygen gas concentration is 0%, the driving voltage is significantly increased when the growth temperature of the p-type contact layer is 1000 ° C. or higher. By doing so, the drive voltage does not increase significantly even in the region of 1000 ° C. or higher.

[Comparative Example 1]
FIG. 11 shows the Mg concentration of the first p-type contact layer 27 and the second p-type contact layer 28 of the LED element 2 after glass sealing in a nitrogen gas atmosphere with an oxygen gas concentration of 0%, and the glass sealing when 20 mA is energized. It is a graph which shows the relationship with the difference of the drive voltage in the LED element 2 before a stop and after glass sealing. FIG. 12 shows the Mg concentration of the first p-type contact layer 27 and the second p-type contact layer 28 of the LED element 2 before glass sealing in a nitrogen gas atmosphere with an oxygen gas concentration of 0%, and when 20 mA is applied. 5 is a graph showing a relationship with a driving voltage in the LED element 2. In the manufacturing process of the light emitting device 1 of the above embodiment, the LED element 2 has a growth temperature of the first p-type contact layer 27 and the second p-type contact layer 28 as a standard growth temperature, a temperature 25 ° C. lower than the standard growth temperature, and A total of nine conditions, three conditions of a temperature lower by 50 ° C. than the standard growth temperature, and three conditions of the Mg concentration being the standard Mg concentration, 0.8 times the standard Mg concentration, and 0.6 times the standard Mg concentration It was produced under the conditions. In Comparative Example 1, the standard growth temperature is 100 ° C., the standard Mg concentration of the first p-type contact layer 27 is 5 × 10 ¹⁹ / cm ^3, and the standard Mg concentration of the second p-type contact layer 28 is 8 × 10 ¹⁹ / cm ³ . In addition, the vapor deposition temperature of the transparent electrode 11 of LED element 2 was 460 degreeC, and the baking temperature was 690 degreeC. In FIGS. 11 and 12, the horizontal axis represents the ratio to the standard Mg concentration.

  As can be seen from the graph of FIG. 11, when the Mg concentration of each of the p-type contact layers 27 and 28 is decreased, the increase in the drive voltage of the LED element 2 after glass sealing can be reduced. Moreover, the result that the reduction of the drive voltage rise of the LED element 2 after glass sealing can also be aimed at was obtained also by making growth temperature low. In addition, the LED element 2 manufactured under the conditions of the standard Mg concentration and the standard growth temperature emitted light only at the end portion of the light emitting layer. However, the LED elements 2 manufactured under other conditions were all surface emitting, and the light emission pattern. Was normal.

  Further, as is apparent from the graph of FIG. 12, although the driving voltage rise of the LED element 2 manufactured under the conditions of the standard Mg concentration and the standard growth temperature is not as remarkable, if the Mg concentration is made too small, the initial driving voltage increases. Tend. At 0.6 times the standard Mg concentration, the initial drive voltage is increased although it is within 10% of the standard Mg concentration. Even if the growth temperature is lowered, the initial drive voltage tends to increase slightly.

From the above, when the oxygen gas concentration is 0%, in order to make the drive voltage after glass sealing as low as possible and to design with high luminous efficiency, the Mg concentration (critical Mg) is such that the initial drive voltage does not increase. It is understood that the growth temperature may be lower than the standard growth temperature. As shown in FIG. 12, when the growth temperature is 950 ° C. or higher and lower than 1000 ° C., the critical Mg concentration is 0.8 times the standard Mg concentration. Further, if the Mg concentration is smaller than the standard Mg concentration, an increase in driving voltage after glass sealing can be suppressed, and a desirable Mg concentration range is 2 × 10 ¹⁹ or more and 8 × 10 ¹⁹ / cm ³ or less. Can be guessed. Further, if the growth temperature is set to the standard growth temperature or lower, an increase in driving voltage after glass sealing can be suppressed, and the preferable growth temperature of the p-type contact layer is higher than the growth temperature of the light emitting layer and less than 1000 ° C. It can be inferred that These numerical values are only when the oxygen gas concentration is 0%, and as described above, an increase in driving voltage can be suppressed if the oxygen-containing atmosphere is not within the range of these numerical values. . Within the range of these values in the oxygen-containing atmosphere, it is possible to further suppress an increase in driving voltage, and a great effect can be obtained even if the oxygen concentration is relatively low.

  FIG. 13 is a graph showing the relationship between the growth temperature of each of the p-type contact layers 27 and 28 and the drive voltage increase due to heat treatment in a nitrogen gas atmosphere with an oxygen gas concentration of 0%. The data was obtained by changing the Mg concentration of each of the p-type contact layers 27 and 28 to a standard Mg concentration and changing the growth temperature every 25 ° C. within a range of 875 ° C. to 1000 ° C. The heat treatment was performed at 600 ° C. for 15 minutes in a nitrogen atmosphere as a treatment to replace glass sealing.

  As shown in FIG. 13, when the growth temperature is in the range of 875 ° C. or more and 950 ° C. or less, the drive voltage increase value is almost constant, but at 975 ° C., the drive voltage increase value is about 1.8 times that of 950 ° C. At ℃, the drive voltage increase value was about 2.8 times that of 950 ° C. As described above, when the oxygen gas concentration is 0%, when the growth temperature of each of the p-type contact layers 27 and 28 is increased, a constant driving voltage increase value starts to increase (in FIG. 13, the critical growth temperature). 950 ° C.) was present.

  Here, in the case where a flat sapphire substrate or a sapphire substrate with concavo-convex processing is used as a growth substrate, defects are likely to occur when a group III nitride semiconductor layer is grown at a low temperature. Therefore, it is desirable that the growth temperature of the first p-type contact layer 27 be as high as possible (critical growth temperature) within a range in which the drive voltage does not increase.

  On the other hand, when a GaN substrate is used as a growth substrate, defects do not easily occur even when grown at a low temperature below the critical growth temperature. For this reason, the first p-type contact layer 27 can be grown at a temperature equal to or lower than 950 ° C., further equal to or close to the growth temperature of the MQW layer 25 that is the light emitting layer, and is grown before the first p-type contact layer 27 is grown. It is possible to increase the accuracy of film formation control by suppressing thermal diffusion of the group III nitride semiconductor layer, and to achieve high efficiency.

  Further, in the light emitting device 1, the glass sealing portion 5 and the LED element 2 are in contact with each other, and the LED element 2 has a high temperature equivalent to that of glass at the time of glass sealing. Further, the LED element 2 is sealed by bonding the glass sealing portion 5 and the element mounting substrate 3 together. Many of the LED elements 2 in which the drive voltage rises due to glass sealing increase the drive voltage simply by leaving the LED element 2 in a nitrogen atmosphere at 400 ° C. or higher for 10 minutes without glass sealing. However, when the LED element 2 is sealed like glass sealing, the degree of increase is increased.

  In this case, if the members constituting the light emitting device 1 contain moisture or hydrogen, the degree of increase in the drive voltage tends to be further increased. For example, when melting glass, it dissolves in a dry nitrogen atmosphere, whereas when it dissolves in the air, the glass takes in moisture in the air. Alternatively, when the phosphor is dispersed in the glass, if the wet pulverization method or the precipitation method is used, the glass takes in moisture. Further, when a ceramic substrate is used as the element mounting substrate 3, the metal circuit pattern forming process by a general plating process such as Ni electroless plating using the reducing action of a hypophosphorous acid aqueous solution is accompanied by hydrogen generation, and the plated portion And the ceramic member will take in hydrogen. These effects can be reduced by glass sealing in an atmosphere containing oxygen gas.

Furthermore, a protective film made of SiO ₂ or the like may be provided after forming the electrode of the LED element, but this also tends to increase the degree of drive voltage increase. In the experiments by the inventors, after forming the p pad electrode 12 and the n electrode 13, the protective film 14 is formed at a region other than the p pad electrode 21 and the n electrode 13 at about 300 ° C., and when the protective film 14 is not formed. When the increase in drive voltage due to glass sealing was compared, the increase in drive voltage was about 1.5 times greater in the case where the protective film 14 was formed than in the case where the protective film 14 was not formed.

  Even in these cases, by reducing the growth temperature of the p-type contact layers 27 and 28 of the LED element 2, it can be made less susceptible to moisture and hydrogen from the sealing member, etc. under special conditions. There is no need to produce glass, and degassing treatment can be omitted. Furthermore, when the protective film 14 is formed, defects such as a short circuit when the light emitting element is mounted can be reduced, and productivity can be improved.

  In addition, regarding the light emitting element in which the Mg concentration of the first p-type contact layer 27 and the second p-type contact layer 28 is set to the standard Mg concentration and the growth temperature is set to the standard growth temperature, the temperature dependency at the time of glass sealing of the driving voltage rise is examined. As a result, it has been found that the higher the glass sealing temperature, the greater the increase in drive voltage.

  The glass has a correlation that the softening temperature is lower and the coefficient of thermal expansion is larger as the bond strength is smaller. For this reason, since the limit which lowers a softening point arises in order to make it the thermal expansion coefficient equivalent to the LED element 2 and the alumina which is white and has a high reflectance and high mechanical strength, a corresponding processing temperature is required. The drive voltage increase depending on the glass sealing temperature can be suppressed by lowering the growth temperature of the p-type layer of the LED element 2 or the like.

  In general, a resin-sealed LED has a processing temperature of less than 200 ° C. Therefore, the above-described problem due to the influence of the LED element 2 itself or the sealing material does not occur. From this, it is considered that this is a problem related to p-type conversion.

[Comparative Example 2]
The manufacturing method of the light emitting device 1 of Comparative Example 2 is the LED element 2 of Comparative Example 1 in which the first p-type contact layer 27 is formed at the standard Mg concentration and the standard growth temperature, and the second p-type contact layer 28 is not formed. Yes, the rest is the same manufacturing process.

  When the light-emitting device 1 manufactured by the manufacturing method of Comparative Example 2 and the light-emitting device 1 of Comparative Example 1 in which the second p contact layer 27 was formed at the standard Mg concentration and the standard growth temperature were compared, the light-emitting device of Comparative Example 1 was compared. The increase value of the drive voltage by the glass sealing of 1 was 1.76 V as shown in the graph of FIG. 11, whereas the increase value of the drive voltage of the light emitting device 1 of Comparative Example 2 was 0.26 V. In addition, the initial driving voltage was 2.97 V in the light emitting device 1 of Comparative Example 1, but it was 3.12 V in the light emitting device 1 of Comparative Example 2. Further, the driving voltage after glass sealing was 4.73 V in the light emitting device 1 of Comparative Example 1, whereas it was 3.38 V in the light emitting device 1 of Comparative Example 2. In the light emitting device 1 of Comparative Example 1, the driving voltage was increased by about 60% due to glass sealing, but in the light emitting device of Comparative Example 2, it was possible to suppress it to 15% or less.

  Thus, by omitting the layer with high Mg concentration in contact with the transparent electrode 11, the initial driving voltage is slightly higher, but an increase in driving voltage in glass sealing can be suppressed, and driving after glass sealing is performed. The voltage can be kept low.

[Comparative Example 3]
The manufacturing method of the light-emitting device 1 of the comparative example 3 adds the process shown below to the manufacturing method of the light-emitting device of the comparative example 1. FIG. This additional step may be performed after the second p-type contact layer 28 is formed and before the glass sealing.

  The step of adding is a step of performing heat treatment at 400 ° C. to 600 ° C. for 0.5 hours to 2 hours in an oxygen atmosphere. By adding this step to the method for manufacturing the light emitting device of Comparative Example 1, it is possible to further suppress an increase in driving voltage. This is presumably because hydrogen can be prevented from being recombined with Mg and deactivated by discharging hydrogen by heat treatment. When the heat treatment temperature is lower than 400 ° C. or the heat treatment time is shorter than 0.5 hour, inactivation cannot be sufficiently prevented and the effect of suppressing the drive voltage rise is low, which is not desirable. If the temperature is higher than 600 ° C., thermal damage higher than the glass sealing temperature is applied to the light-emitting element, which is undesirable because of deterioration of the electrodes and the like. This is not desirable because it causes extra heat damage to the light emitting element beyond the effect of preventing activation.

  Actually, in the manufacturing process of the light emitting device of Comparative Example 1, a heat treatment step at 600 ° C. for 0.5 hours in air was added after the LED element 2 was manufactured and before mounting on the element mounting substrate 3. It was confirmed that the drive voltage was increased by about 1/5 compared with the case where no process was added.

  By performing this added process after the formation of the transparent electrode 11, it is possible to prevent the formation of a surface oxide film that increases the resistance on the surface of the semiconductor layer. Alternatively, the step of removing the surface oxide film can be omitted. In addition, by performing the process before separating the light emitting elements individually, batch processing can be performed, and manufacturing effort can be prevented from being significantly increased. Thus, it is preferable to add the heat treatment step after the formation of the transparent electrode 11 and before the separation step of the light emitting element.

DESCRIPTION OF SYMBOLS 1 Light-emitting device 2 LED element 3 Element mounting board 4 Circuit pattern 5 Glass sealing part 6 Via hole 7 Bump 11 Transparent electrode 12 p pad electrode 13 n electrode 14 Protective film 20 Substrate 21 Buffer layer 22 n-type contact layer 23 n-type ESD layer 24 n-type cladding layer 25 MQW layer 26 p-type cladding layer 27 first p-type contact layer 28 second p-type contact layer 41 via pattern 42 surface pattern 43 back surface pattern 51 glass before sealing 51a recess 52 glass before sealing 53 phosphor 80 Intermediate 91 Lower mold 92 Upper mold

Claims (7)

N-type layer made of a Group III nitride semiconductor, light emitting layer, p-type cladding layer, a light-emitting element manufactured by growing a p-type contact layer mounted on the element mounting substrate, sealed with a glass which is heated to the light emitting element the method for manufacturing a light emitting device to be stopped,
The p-type contact layer is formed at a growth temperature higher than the growth temperature of the light emitting layer and less than 1000 ° C.,
The light emitting device is sealed by hot pressing using a mold made of an oxidation resistant material in a gas atmosphere containing oxygen. The glass is ZnO glass, Bi ₂ O ₃ glass, P ₂ O ₅ glass, Nb ₂ O ₅ glass, GeO ₂ glass, Ga ₂ O ₃ glass, Y ₂ O ₃ glass, La ₂ O. _The method for producing a light-emitting device according to claim 1, which is a ₃ glass, a Gd ₂ O ₃ glass, or a Ta ₂ O ₅ glass.   The method for manufacturing a light emitting device according to claim 1, wherein the element mounting substrate is made of a polycrystalline ceramic material.   The method for manufacturing a light-emitting device according to claim 1, wherein the glass includes diffusing particles.   The manufacturing method of the light-emitting device of any one of Claim 1 to 4 which seals the said light emitting element in the atmosphere pressure-reduced rather than atmospheric pressure.   The manufacturing method of the light-emitting device of any one of Claim 1 to 5 which melts and solidifies powdery glass and seals the said light emitting element. Manufacturing method of the preceding Symbol p-type contact layer, the light emitting device according to any one of claims 1 Mg concentration to form 2 × ^{10 19} or more 8 × ¹⁰ 19 / cm ³ or less and so as 6.

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