JP2008205229A - Semiconductor light-emitting element, semiconductor light-emitting apparatus, and manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem where a light from a light-emitting element travels in all directions, because a light other than the light advancing in a lighting direction cannot be utilized effectively, even though a means is proposed in which an inclined plane is attached to the side of semiconductor light-emitting element, and a reflecting layer is formed therein, the inclined plane is attached by methods such as etching, and processing requires time and the control of the inclined plane is difficult. <P>SOLUTION: The inclined plane for reflection is formed by mechanical processing on a thick substrate in which a light-emitting layer is formed, and the reflecting layer is formed. Thereafter, after filling with a reinforcing member from the light-emitting plane, the substrate is ground until the reflecting film appears in the surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting element in which a reflective layer is disposed on a side surface in order to effectively utilize light emitted from the side surface of the semiconductor light emitting element, a semiconductor light emitting device using the same, and a manufacturing method.

  In the semiconductor light emitting device, light is emitted from a light emitting layer formed of p-type and n-type semiconductors sandwiching an active layer. Therefore, light is emitted in all directions. However, as a light source, it is often desired to irradiate light in one direction. In that case, light traveling in a direction different from the irradiation direction is wasted. Considering the efficient use of light, it is preferable to reflect these lights in the light emitting direction of the semiconductor light emitting device.

  In order to deal with such a problem, a semiconductor light emitting device having a side surface inclined so as to face the light emitting surface has been proposed. For example, Patent Document 1 discloses a semiconductor light emitting device having a side surface that is inclined on an electrode and has a reflective layer. This semiconductor light emitting device has electrodes formed on both sides of a light emitting layer. Further, in order to increase the light extraction efficiency from the light emitting layer, the sapphire substrate used for forming the light emitting layer is peeled off later with a laser.

Further, in Patent Document 2, an electrode is formed on one of the transparent substrates, and an inclined surface with an angle is formed on the bottom surface which is the opposite surface of the emission surface so that the light generated by the light emitting layer does not strike the electrode. A semiconductor light emitting device is shown.
JP 2006-128659 A JP-A-6-268252

  In order to efficiently use the light emitted from the semiconductor light emitting device, a structure in which a reflective layer is applied with the side surface as an inclined surface is desirable. However, if a technique such as etching as in Patent Document 1 is used to form the inclined surface, it takes time to manufacture. On the other hand, to form the inclined surface mechanically, a thick substrate is required to protect the light emitting layer from impact during processing. That is, there is a problem that it is difficult to form an inclined surface on the side surface by mechanical processing using a thin substrate. In particular, in the case where the substrate is a cleaved crystal such as GaN or SiC, if the thickness is thin, inclining the side surface by mechanical processing causes the substrate to be easily broken, resulting in a low yield.

  In that regard, as disclosed in Patent Document 2, when a sufficiently thick substrate is used, it is easy to form an inclined surface that reflects light. However, a portion where the reflective layer is not formed remains on the side surface portion. The light leaking from the side surface on which the reflecting surface is not formed is merely lost light.

  Therefore, a side structure that can leak light is not preferable from the viewpoint of effective use of light. From the viewpoint of improving the light extraction efficiency, it is not preferable to form an electrode on the light emitting surface. The present invention has been conceived to solve the above-described problems, and a semiconductor light emitting device in which an inclined surface is formed on a side surface by mechanical processing, and the inclined surface is entirely a reflective surface, and is used. A semiconductor light emitting device and a manufacturing method thereof are provided.

  In order to solve the above problems, the present invention provides a light emitting layer on a thick substrate, forms an inclined surface by mechanical processing, and forms a reflective layer on the inclined surface. Further, the substrate is manufactured by grinding from the side opposite to the side where the light emitting layer is provided to the slope portion. In addition, the p-side electrode and the n-side electrode are formed on the opposite side of the substrate as the light emitting surface.

  By such a manufacturing method, a substrate having one surface as a light emitting surface, an n-type layer formed on the surface of the substrate opposite to the light emitting surface, an n-side electrode formed on the n-type layer, A p-type layer formed on the n-type layer, at least one active layer disposed between the n-type layer and the p-type layer, and a p-side electrode formed on the p-type layer; A semiconductor light emitting device having an angle formed with the light emitting surface and greater than 0 degrees and smaller than 90 degrees and a side surface on which a reflective film is formed is obtained.

  By the method for manufacturing a semiconductor light emitting device of the present invention, an inclined surface that reflects light emitted from the light emitting layer in the lateral direction to the light emitting surface side can be produced by mechanical processing, and all of the side surfaces become reflecting surfaces. Therefore, it is possible to obtain a semiconductor light emitting element that does not generate light leakage from the side surface that is merely a loss.

  In addition, since both the p-side and n-side electrodes are formed on one side of the substrate, the area of the light emitting surface is not reduced by the electrodes.

  Further, when the substrate is ground, the amount of grinding can be known by the degree of appearance of the reflective film, and there is an effect that the processing becomes easy.

(Embodiment 1)
FIG. 1 shows a semiconductor light emitting device 1 of the present invention. The semiconductor light emitting device 1 has a structure in which a semiconductor light emitting element 10 is fixed on a submount 21.

  Lead electrodes 22 and 23 are formed on the submount 21. The extraction electrode is an electrode for applying a current to the semiconductor light emitting element 10. There are an n-side extraction electrode 22 connected to the n-type layer side of the semiconductor light emitting device and a p-side extraction electrode 23 connected to the p-type layer side. Further, in FIG. 1, the extraction electrode is connected to the back surface electrodes 28 and 29 through the through holes 26 and 27. As a result, current can flow from the back electrodes 28 and 29 to the semiconductor light emitting device. The back electrode also includes an n-side back electrode 28 and a p-side back electrode 29.

  Bumps 24 and 25 are formed on the extraction electrode. Similar to the lead electrode, the bump includes an n-side bump 24 connected to the n-type layer and a p-side bump 25 connected to the p-type layer. Although there are a plurality of p-side bumps in FIG. Of course, there may be a plurality of n-side bumps.

  The lead electrode and the semiconductor light emitting element are directly connected by this bump. Therefore, this bump is a connection line. The submount, extraction electrode, back electrode, through hole, and bump are collectively referred to as the support 20. In some embodiments, the back electrode, the through hole, and the bump may be omitted from the support 20.

  For the submount 21, a silicon Zener diode, a silicon diode, silicon, aluminum nitride, alumina, other ceramics, or the like can be used.

  The through hole is a through hole formed in the submount and includes a conductive material such as copper, aluminum, and gold inside. The back electrodes 28 and 29 are electrically joined to the through holes and are made of a conductive material such as copper, silver, or gold. For the extraction electrode, a conductive material such as copper, aluminum, gold, or silver is used.

  The bumps serve to fix the semiconductor light emitting element 10 on the submount 21 and to electrically couple the lead electrodes 22 and 23 to each other.

  As the material for the bump, gold, gold-tin, solder, indium alloy, conductive polymer, or the like can be used, but a material mainly containing gold or gold is particularly preferable. Using these materials, it can be formed using a plating method, a vacuum deposition method, a screen printing method, a droplet injection method, a wire bump method, or the like.

  For example, a gold wire is prepared by a wire bump method, and one end of the gold wire is bonded to a lead electrode on a submount with a bonder, and then the wire is cut to form a gold bump. In addition, a liquid in which fine nanoparticles of highly conductive material such as gold are dispersed in a volatile solvent is printed by a method similar to inkjet printing, and the solvent is removed by volatilization to form bumps as an aggregate of nanoparticles. A drop ejection method can also be used.

  FIG. 2 is a cross-sectional view of the semiconductor light emitting device 10, and FIG. 3 is a plan view from the top of the substrate. The semiconductor light emitting device 10 includes a substrate 11, an n-type layer 12, an active layer 13, a p-type layer 14, an n-side electrode 16, and a p-side electrode 17.

  The substrate 11 plays a role of holding the light emitting layer. As a material, insulating sapphire can be used. However, since the light emission efficiency and the light emitting part are made of gallium nitride (GaN), the refractive index equivalent to that of the light emitting layer is reduced in order to reduce the reflection of light at the interface between the n-type layer 12 and the substrate 11. It is preferable to use GaN, SiC, AlGaN, or AlN.

  The n-type layer 12, the active layer 13, and the p-type layer 14 that are light emitting layers are sequentially stacked on the substrate 11. The material is not particularly limited but is preferably a gallium nitride compound. Specifically, the n-type layer 12 of GaN, the active layer 13 of InGaN, and the p-type layer 14 of GaN, respectively. As the n-type layer 12 and the p-type layer 14, AlGaN or InGaN may be used, or a buffer layer made of GaN or InGaN may be used between the n-type layer 12 and the substrate 11. It is. For example, the active layer 13 may have a multilayer structure (quantum well structure) in which InGaN and GaN are alternately stacked.

  Thus, the active layer 13 and the p-type layer 14 are removed from a part of the n-type layer 12, the active layer 13 and the p-type layer 14 laminated on the substrate 11, and the n-type layer 12 is exposed. An n-side electrode 16 is formed on the exposed n-type layer 12. Similarly, a p-side electrode 17 is formed on the p-type layer 14. That is, by removing the active layer 13 and the p-type layer 14 and exposing the n-type layer 12, the light emitting layer, the p-side electrode, and the n-side electrode can be formed on the same side of the substrate.

  The p-side electrode 17 uses a first electrode made of Ag, Al, Rh or the like having high reflectivity in order to reflect the light emitted from the light emitting layer to the substrate 11 side. That is, the top surface side of the substrate 11 becomes the light emitting surface 55. In order to reduce the ohmic contact resistance between the p-type layer 14 and the p-side electrode 17, it is more desirable to use an electrode layer such as Pt, Ni, Co, or ITO between the p-type layer 14 and the p-side electrode. The n-side electrode 16 can use Al, Ti, or the like. It is desirable to use Au or Al on the surface of the p-side electrode 17 and the n-side electrode 16 in order to increase the adhesive strength with the bump. These electrodes can be formed by vacuum deposition, sputtering, or the like.

  The size of the semiconductor light emitting element 10 is not particularly limited, but in order to obtain a light source with a large amount of light and near surface emission, it is preferable that the entire area is wide, and it is desirable that one side is 600 μm or more.

  The inclined surface 31 is formed on the side surface of the semiconductor light emitting element 10 at an angle such that the length L increases from the light emitting layer side toward the light emitting surface. A reflective layer 33 is formed on the inclined surface 31 over the entire inclined surface. The reflective layer 33 is made of a highly reflective material such as Al, Ag, Rh, Zn, and is mainly produced by a technique such as sputtering, vapor deposition, or plating. Of course, the reflective layer may be formed by applying or printing a coating material in which these fine particles are dispersed in a medium such as a resin.

  The inclined surface 31 reflects the light emitted from the light emitting layer in the side surface direction toward the light emitting surface 55. Therefore, the angle 34 formed by the light emitting surface 55 and the inclined surface 31 is smaller than 90 degrees. When this angle 34 becomes large, the reflected light enters at a shallow angle with respect to the light emitting surface, so that the total reflected light increases. That is, the light extraction efficiency from the semiconductor light emitting element is reduced.

  On the other hand, when the angle 34 is small, the length of the substrate on which the light emitting layer is formed and the length of the light emitting surface side are significantly different, and the strength of the semiconductor light emitting element is lowered. Therefore, the angle 34 is more preferably in the range of 20 degrees to 70 degrees, preferably 30 degrees to 60 degrees.

  FIG. 4 shows a method for manufacturing a semiconductor light emitting element and a semiconductor light emitting device of the present invention. First, an n-type semiconductor 12, an active layer 13, and a p-type semiconductor 14 are formed on a material to be the substrate 11 (FIG. 4A). Note that the material for the substrate is referred to as a wafer 41. Next, the p-type semiconductor 14 and a part of the active layer 13 are removed by etching to expose the n-type semiconductor (FIG. 4B).

  An n-side electrode 16 and a p-side electrode 17 are formed on the exposed n-type semiconductor and the p-type semiconductor, respectively (FIG. 4C). Then, a notch 42 is provided for each portion to be a semiconductor light emitting element. The notch 42 is a dicing blade having a taper angle at the cutting edge, and makes a cut (FIG. 4D). The depth of the notch 42 is adjusted so as to be equal to or greater than the thickness of the light emitting element to be finally produced. From the viewpoint of maintaining the mechanical strength of the light emitting element, the depth of the notch 42 is 10 μm or more. From the viewpoint of reduction, the depth is desirably 100 μm or less. Therefore, the thickness of the substrate that occupies most of the thickness of the light emitting element should be 100 μm or less.

  Next, the reflective layer 33 is formed at the notch 42 (FIG. 4E). Needless to say, when the reflective layer is formed by vacuum treatment, a photoresist is formed in addition to the notch portion. A metal layer is cut by laser scribing at the bottom 43 of the valley of the notch 42, and a notch is made in the substrate. By doing so, it is possible to prevent the reflective layer from being divided at locations other than the bottom 43 of the valley when separating from the back surface side of the substrate by applying a cutter along the notch (FIG. 4). (F)). The separated portion is a light emitting element portion 9. When only the semiconductor light emitting element is obtained, the wafer 41 is ground until the reflection layer comes out in the state of FIG.

  FIG. 5 shows a manufacturing method for manufacturing a semiconductor light emitting device using the light emitting element portion 9 manufactured in FIG. Lead electrodes 22 and 23 are formed on the material to be the submount 21. Through holes and back electrodes are also formed as necessary. Bumps 24 and 25 are formed on the extraction electrodes 22 and 23, respectively. Then, the light emitting element portion 9 is welded (FIG. 5A).

  Next, the entire submount is filled with the reinforcing material 44 (FIG. 5B). The reinforcing material 44 is preferably a material having a certain level of strength and easy to remove. For example, a resin material such as electron wax is suitable.

  And this is ground. For grinding, a lap master or the like can be used. Grinding is performed until the reflective layer 33 appears on the polishing surface 47 (FIG. 5C). By doing in this way, all the side surfaces of a semiconductor light emitting element can be made into the inclined surface provided with the reflection layer. Grinding until the reflective layer appears on the polished surface also has the effect of knowing the grinding target. In addition, the substrate can be thinned with high yield, and the light emission efficiency can be increased.

  Finally, the reinforcing material is removed to obtain the semiconductor light emitting device 1 of the present invention (FIG. 5D). Thereafter, the submount can be cut to obtain individual semiconductor light-emitting devices, or a plurality of semiconductor light-emitting devices may be connected.

(Embodiment 2)
FIG. 6 shows the configuration of the semiconductor light emitting device 2 of the present embodiment. In the semiconductor light emitting device 2, the light reflection surface 55 is subjected to an antireflection treatment 57. By performing the antireflection treatment, the light traveling through the substrate is prevented from being totally reflected at a shallow angle on the light emitting surface, and the light extraction efficiency from the semiconductor light emitting element is improved.

  FIG. 7 shows a method for manufacturing the semiconductor light emitting device 2. The light emitting element portion 9 is welded onto a submount on which extraction electrodes and bumps are formed, filled with a reinforcing material, and then polished, as in the case of FIG. 5 (FIG. 7C).

  Next, a fine uneven structure is formed on the polished light emitting surface 55 (FIG. 7D). The minute concavo-convex structure prevents total reflection on the light emitting surface and improves light extraction efficiency.

  If microfabrication using a nanoimprint technique is used for the fine concavo-convex structure, it is possible to form a fine pattern of the same scale as the wavelength of light or a smaller scale depending on the wavelength of light used. In addition, various patterns such as a groove shape, a weight shape, and a semi-spherical shape can be formed. Note that the surface on which nanoimprinting is performed needs to be flat, but since the ground surface composed of the semiconductor light emitting device 2 and the reinforcing material 44 is very flat, a fine pattern can be formed with high accuracy. When nanoimprinting is performed, a polymer resist such as PMMA (polymethylmethacrylate) is applied to the light emitting surface 55, dried and baked, and then the uneven shape formed on the mold surface is transferred.

  The formation of the concavo-convex shape on the surface by etching is simple and improves the light extraction effect. However, it is difficult to accurately control the uneven shape, and the same uneven shape cannot be formed on many substrate surfaces. Etching can be used by either wet etching or dry etching. In dry etching, there are an ion milling method and a chlorine gas method. In wet etching, etching can be performed using an etchant mainly composed of alkali.

  In addition, by adjusting the grain size of the grindstone used at the end of the grinding step, it is possible to finish the surface roughness within a certain range in a state where the grinding is finished, thereby obtaining a concavo-convex structure on the substrate surface.

  In addition, a concavo-convex structure can be formed on the substrate surface by an ink jet printing method. Since this method does not include a step of etching the substrate, it can be easily performed. The light extraction effect can be obtained by adjusting the refractive index of the concavo-convex structure itself to be created. Then, after forming a micro uneven structure on the light emitting surface 55, the reinforcing material 44 is removed to obtain the semiconductor light emitting device 2 (FIG. 7E).

(Embodiment 3)
FIG. 8 shows the configuration of the semiconductor light emitting device 3 of the present embodiment. The semiconductor light emitting device 3 has a structure in which a phosphor-containing sealing layer 59 is formed around the semiconductor light emitting device 2. FIG. 9 shows the manufacturing method. The process is the same as that shown in FIG. 7E until the light-reflecting surface 55 is subjected to the antireflection treatment 57 having a minute uneven structure (FIG. 9D). Then, the semiconductor light emitting device 3 then forms the phosphor-containing sealing layer 59 around the semiconductor light emitting element 10. The forming method is not particularly limited, but it is easy to apply the coating material for the phosphor-containing sealing layer by printing because the production time is short.

  The phosphor-containing sealing layer 59 is obtained by dispersing particles of an inorganic or organic phosphor material in a transparent medium such as a resin or glass.

For example, when the semiconductor light emitting element 10 emits blue light and the emission color of the semiconductor light emitting device 3 itself is white, the phosphor that receives blue light from the semiconductor light emitting element 10 and converts the wavelength to yellow and emits it. It is. As such a phosphor material, a rare earth-doped nitride-based or rare earth-doped oxide-based phosphor is preferable. More specifically, (Y · Sm) ₃ (Al · Ga) ₅ O ₁₂ : Ce or (Y _0.39 Gd _0.57 Ce _0.03 Sm _0.01 ) ₃ Al ₅ O ₁₂ of the rare earth doped alkaline earth metal sulfide rare earth doped garnet. Rare earth doped alkaline earth metal orthosilicate, rare earth doped thiogallate, rare earth doped aluminate and the like can be suitably used. Further, silicate phosphor _{(Sr 1-a1-b2-} x Ba a1 Ca b2 Eu x) 2 SiO 4 or alpha sialon _{(α-sialon: Eu) M} x (Si, Al) 12 (O, N) 16 a It may be used as a phosphor material that emits yellow light.

  As the medium, a resin mainly composed of silicon resin, epoxy resin, and fluorine resin can be used. In particular, as the non-silicon resin, siloxane-based resins, polyolefins, silicone / epoxy hybrid resins, and the like are suitable.

A glass material prepared by a sol-gel method can be used instead of the resin. Specifically, it is a compound represented by the general formula Si (X) _n (R) _4-n (n = 1 to 3). Here, R is an alkyl group, and X is selected from halogen (Cl, F, Br, I), a hydroxy group (—OH), and an alkoxy group (—OR). A phosphor or an alkoxide represented by the general formula M (OR) _n can also be added to this glass material. The refractive index of the concavo-convex structure can be changed by adding an alkoxide.

  Some of these glass materials have a curing reaction temperature of about 200 degrees Celsius, and can be said to be suitable materials considering the heat resistance of materials used for bumps and electrode portions. A state in which the phosphor material and the medium are mixed is called a phosphor paint.

  Throughout this specification, Al is aluminum, N is nitrogen, O is oxygen, Ag is silver, Rh is rhodium, Pt is platinum, Ni is nickel, Co is cobalt, Ti is titanium, Au is gold, Y is yttrium, Sm represents samarium, Ce represents cerium, Sr represents strontium, Ba represents barium, Ca represents calcium, Eu represents europium, and Mg represents magnesium.

  The present invention can be used for a semiconductor light emitting device having a light emitting efficiency by forming a reflective layer on the side surface.

The figure showing the structure of the semiconductor light-emitting device of this invention The figure which shows the cross section of the semiconductor light-emitting device of this invention The top view which looked at the semiconductor light-emitting device of this invention from the light emission surface side The figure which shows the manufacturing method of the semiconductor light-emitting device of this invention The figure which shows the manufacturing method of the semiconductor light-emitting device of this invention The figure which shows the other structure of the semiconductor light-emitting device of this invention. FIG. 6 is a view showing a method for manufacturing the semiconductor light emitting device of the present invention in FIG. The figure which shows the other structure of the semiconductor light-emitting device of this invention. FIG. 8 shows a method for manufacturing the semiconductor light emitting device of the present invention in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor light-emitting device 10 Semiconductor light-emitting device 11 Substrate 12 N-type layer 13 Active layer 14 P-type layer 16 n-side electrode 17 p-side electrode 20 Support body 21 Submount 22 n-side extraction electrode 23 p-side extraction electrode 24 n-side bump 25 P-side bump 26, 27 Through hole 33 Reflective layer 42 Notch 44 Reinforcement material 55 Light emitting surface 57 Light emitting surface subjected to total reflection prevention 59 Phosphor-containing sealing layer

Claims (8)

A substrate having one surface as a light emitting surface;
An n-type layer formed on an opposite surface of the substrate to the light emitting surface;
An n-side electrode formed on the n-type layer;
A p-type layer formed on the n-type layer;
At least one active layer disposed between the n-type layer and the p-type layer;
A p-side electrode formed on the p-type layer;
A semiconductor light emitting element having a side surface on which a reflection film is formed and an angle formed with the light emitting surface is larger than 0 degree and smaller than 90 degrees. The semiconductor light emitting device according to claim 1, wherein the substrate is GaN or SiC having a thickness of 100 μm or less. The semiconductor light emitting element according to claim 1, wherein the light emission surface is subjected to a total reflection prevention treatment. A semiconductor light emitting device according to any one of claims 1 to 3,
A semiconductor light-emitting device comprising: a submount on which an extraction electrode connected to the n-side and p-side electrodes of the semiconductor light-emitting element is formed. The semiconductor light-emitting device according to claim 4, wherein a phosphor layer is disposed around the semiconductor element. The semiconductor light-emitting device according to claim 5, wherein the phosphor layer contains inorganic glass. Forming a light emitting layer comprising an n-type layer, an active layer and a p-type layer on a substrate;
Removing a part of the active layer and the p-type layer and forming an extraction electrode on the n-type layer and the p-type layer;
Forming a notch in the substrate;
Forming a reflective layer in the notch;
A method for manufacturing a semiconductor light emitting device, comprising: grinding a surface of a substrate opposite to the side on which the light emitting layer is formed until at least a part of the notch is exposed. Forming a light emitting layer comprising an n-type layer, an active layer and a p-type layer on a substrate;
Removing a part of the active layer and the p-type layer and forming an n-side electrode and a p-side electrode on the n-type layer and the p-type layer, respectively;
Forming a notch in the substrate;
Forming a reflective layer in the notch;
Connecting the n-side electrode and the p-side electrode to a submount on which an extraction electrode is formed;
Filling the submount with a reinforcing agent;
Grinding the surface of the substrate opposite to where the light emitting layer is formed until at least a portion of the notch is exposed;
A method for manufacturing a semiconductor light emitting device, including a step of removing the reinforcing agent.

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