JP4147073B2 - Manufacturing method of light emitting diode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-brightness compound semiconductor light-emitting diode used in indoor and outdoor display panels, vehicle-mounted display lamps, traffic lights, mobile phone backlights, and the like, and a photointerrupter and photocoupler that require directivity in emitted light. relates to a method for manufacturing a light emitting diode used for functional devices such as a fiber source.
[0002]
[Prior art]
Prior art documents related to the present invention include the following.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-131066 (FIG. 1)
[0004]
As a conventional light emitting diode element, for example, as shown in FIG. 5, a GaAlAs red light emitting diode 100 includes a p-type GaAs substrate 101, a p-type GaAlAs cladding layer 102, a GaAlAs active layer 103, an n-type GaAlAs cladding layer 104, and n It has a multilayer structure in which a type GaAlAs contact layer 105 is laminated. Electrodes 106 and 107 are formed on the lower surface of the p-type GaAs substrate 101 and the upper surface of the n-type GaAlAs contact layer 105, respectively. When a current is passed between the electrodes 106 and 107 of the light emitting diode 100, the GaAlAs active layer 103 and the n-type GaAlAs cladding layer 104 emit light. At this time, light is emitted outward from the top surface, side surface, and back surface of the element 100, and part of the light is repeatedly reflected inside the light emitting diode 100 and finally emitted outside the light emitting diode 100.
[0005]
However, light emitted from the light emitting layers 103 and 104 toward the top surface or light repeatedly reflected inside the crystal is absorbed by the crystal in the process until it is emitted to the outside of the diode 100, Since it is absorbed by the solder material for element bonding, the light extraction efficiency is not always good. In particular, when the light emitting diode 100 is used as a light source for a photo interrupter or an optical fiber, the directivity of emitted light is important, and it is desirable to emit light only in the top surface direction as much as possible.
[0006]
Therefore, in order to reduce absorption in the crystal of the light emitting diode 100, the aluminum mixed crystal ratio of the contact layer 105 is increased, and the material and shape of the electrode 106 on the back surface side are devised to improve the light external extraction efficiency. Is planned.
[0007]
As a conventional light emitting diode element, for example, as shown in FIG. 6, a GaAlInP light emitting diode 108 includes an n-type GaAs substrate 109, an n-type AlGaInP cladding layer 110, an AlGaInP active layer 111, and a p-type AlGaInP cladding layer 112. Having a multilayer structure. An n-type electrode 113 and a p-type electrode 114 are formed on the lower surface of the n-type GaAs substrate 109 and the upper surface of the p-type AlGaInP cladding layer 112, respectively. When a current is passed between the electrodes 113 and 114 of the light emitting diode 108, the n-type AlGaInP cladding layer 110 and the AlGaInP active layer 111 emit light. In the light-emitting diode 108, semiconductor crystals having different compositions are stacked in the crystal to form a semiconductor multilayer reflector or a light reflecting multilayer film 115 (DBR), and light emitted to the back side is directed toward the top surface. It is supposed to be reflected. Since it is difficult to form the DBR 115 by the liquid layer growth method, the DBR 115 is mainly formed in a quaternary light emitting diode centering on AlGaInP stacked by vapor phase growth. Furthermore, in addition to the DBR 115, an n-type AlGaInP cladding layer (current confinement layer) 116 is formed or light is forcibly emitted only in the direction of the top surface by shielding the light by devising the arrangement of the electrodes on the top surface. It has come to be.
[0008]
As another method, the light emitted from the side surface of the element is refracted by resin-molding the element, and the emission direction is changed to the top surface direction. As shown in FIG. A method is known which is arranged on the inner bottom of the mortar-shaped frame 117 and causes the light emitted from the side surface of the light emitting diode element 100 to reflect the luminance viewed from the top surface direction of the light emitting diode 100 by reflecting in the top surface direction. is there. However, since the light emitting diode element 100 is incorporated in the mortar-shaped frame 117, the manufacturing process is complicated.
[0009]
As another method for directing light emitted from the side surface of the light emitting diode element in the top surface direction, for example, light emitted from the light emitting layer of the light emitting diode in the horizontal direction is emitted from the light emitting layer. Is reflected by a reflective film provided on the slope of a V-groove formed around (see, for example, Patent Document 1). The reflective film and the electrode of this light emitting diode are made of an aluminum metal material. In order to improve the reliability of the light emitting diode, a silicon oxide film as a protective film is formed on the surface of the light emitting diode element. However, this light emitting diode has a problem that it is necessary to form a silicon oxide film in order to provide a protective film, which complicates the manufacturing process.
[0010]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide a simple method for manufacturing a light-emitting diode capable of improving the directivity of emitted light toward the top surface and preventing a decrease in luminance.
[0011]
[Means for Solving the Problems]
As a means for solving the above problems, the present invention provides:
In a method for manufacturing a light emitting diode in which a light emitting layer is stacked on a substrate,
V-grooves are formed around the light emitting layer by performing mesa etching deeper than the light emitting layer of the semiconductor layer,
Forming a reflective film made of gold on a side surface of the V-groove facing the light emitting layer;
The surface of the semiconductor layer is oxidized with an oxidizing solution and then annealed to form a protective film.
[0012]
According to the invention, since the reflective film made of gold is formed on the side surface facing the light emitting layer of the V groove formed around the light emitting layer, the directivity of the light emitted from the light emitting layer toward the top surface is improved. It improves and can reflect light effectively.
[0013]
According to the invention, since the protective film is formed by annealing, it can be simplified as compared with the conventional manufacturing method. Further, since the reflective film is made of gold, it is not eroded by the acid used during the annealing process.
[0014]
By forming a thin electrode of gold on the upper surface of the semiconductor layer when forming the reflective film, the manufacturing method can be simplified as compared with the conventional light emitting diode manufacturing method.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0016]
FIG. 1 shows a GaAlAs red light emitting diode 1 which is a light emitting diode according to the present invention. The light emitting diode 1 has a multilayer structure in which a p-type GaAs substrate 2, a p-type GaAlAs cladding layer 3, a GaAlAs active layer 4, an n-type GaAlAs cladding layer 5, and an n-type GaAlAs contact layer 6 are laminated. A p-type electrode 7 and an n-type electrode 8 are formed on the lower surface of the p-type GaAs substrate 2 and the upper surface of the n-type GaAlAs contact layer 6, respectively. The light emitting regions of the light emitting diode 1 are a GaAlAs active layer 4 and an n-type GaAlAs cladding layer 5. A V-groove 11 is formed around the light-emitting diode 1, and a reflective film 12 is formed on the outer side surface of the V-groove 11, that is, the side surface facing the light-emitting layers 4 and 5 of the V-groove 11. .
[0017]
A natural oxide film 9 is formed on the surface of the light emitting diode 1 as a protective film. As will be described later, the natural oxide film 9 is obtained by oxidizing the crystal surface by annealing the surface of the light-emitting diode 1 with an acid having a strong oxidizing property.
[0018]
Next, a manufacturing method for manufacturing the light emitting diode 1 will be described.
[0019]
2A, first, a p-type GaAlAs cladding layer 3, a GaAlAs active layer 4, an n-type GaAlAs cladding layer 5 and an n-type GaAlAs contact layer 6 are formed on a p-type GaAs substrate 2 by a liquid layer epitaxial growth method. Laminate sequentially. Here, the aluminum mixed crystal ratio (Ga _1-X Al _X As: mixed crystal ratio X) of each epitaxial layer is 0.6, 0.2, 0.4, and 0.6, 20 μm, 1 μm, 10 μm and 30 μm. It is preferable to use magnesium as the p-type dopant and tellurium as the n-type dopant.
[0020]
Next, as shown in FIG. 2B, part or all of the p-type GaAs substrate 2 is removed by etching, and the epitaxial wafer is processed to have a predetermined thickness.
[0021]
Subsequently, as shown in FIG. 3A, a thin electrode material is formed on the lower surface of the p-type GaAs substrate 2 by sputtering or vapor deposition to form a p-type electrode 7. Further, as shown in FIGS. 3A and 3B, patterning is performed by forming a mask 10 using a photosensitive resist. The mask 10 has a region 10a that protects a portion where the n-type electrode 8 is formed, and a lattice region 10b that passes through the center between the regions 10a.
[0022]
In this state, as shown in FIG. 4A, mesa etching is performed to a position deeper than the light emitting layers 4 and 5 (to the vicinity of the p-type GaAs substrate 2), and V grooves 11 are formed around the light emitting layers 4 and 5, respectively. Form. At this time, the top portion 11a located between the adjacent V grooves 11 does not have to be the same height as the electrode formation portion (the upper surface of the n-type GaAlAs contact layer 6), and the top portion 11a is compared with the light emitting regions 4 and 5. If it is in a high position. That is, side etching may proceed during mesa etching and the lattice-like region 10b may be peeled off.
[0023]
Then, as shown in FIG. 4B, after a thin film of gold (metal material) is formed in a wafer shape by sputtering or vapor deposition, the n-type electrode 8 and the reflective film 12 are left using a photosensitive resist. Perform patterning. Here, the n-type electrode 8 is formed in a predetermined region on the upper surface of the n-type GaAlAs contact layer 6, and the reflective film 12 is formed on the side surface of the V groove 11 facing the light emitting layers 4 and 5. By performing the electrode formation and the reflective film formation at the same time, a simpler light emitting diode manufacturing method can be realized as compared with the conventional manufacturing method. Further, in the electrode forming and reflecting film forming steps, a metal material may be formed into a thin film by vapor deposition after patterning with a resist or the like, and then formed by a lift-off method.
[0024]
Next, as shown in FIG. 4C, the light emitting diode 1 is treated with an oxidizing solution, and the crystal surface of the light emitting diode 1 is oxidized and annealed to form a protective film 9. At this time, since the n-type electrode 8 and the reflective film 12 are made of very stable gold, the reflectance of the reflective film 12 and the function as the reflective film are not deteriorated without being eroded by the oxidizing solution. . As a result, the protective film 9 is formed by annealing rather than the complicated silicon film forming step as in the conventional manufacturing method, so that the protective film 9 can be easily formed compared to the conventional manufacturing method. Can be formed.
[0025]
Then, as shown in FIG. 4D, the chip is divided with reference to the top portion 11a where the reflective film 12 is formed. As a chip division method, a scribe line may be inserted from the back side and division may be performed using cleaving, but division by dicing is desirable in order to reduce chip cracking and chip chipping.
[0026]
As shown in FIG. 1, the light emitting diode 1 manufactured as described above emits light emitted from the light emitting region (GaAlAs active layer 4, n-type GaAlAs clad layer 5) in the top surface direction. The emitted light passes through the n-type GaAlAs contact layer 6 and is emitted outward. Further, the light emitted in the horizontal direction is reflected in the top surface direction by the reflection film 12 located on the side surface of the V groove 11 facing the light emitting layers 4 and 5. Further, the light emitted toward the back surface is repeatedly reflected in the crystal of the light emitting diode 1 and finally emitted to the outside. Thereby, the GaAlAs red light emitting diode 1 with high directivity of the emitted light is obtained. This manufacturing process is not limited to GaAlAs light emitting diodes, but can be applied to other types of light emitting diode materials (for example, quaternary light emitting diodes, etc.) by changing processing conditions. is there.
[0027]
【The invention's effect】
The light emitting diode manufacturing method of the present invention forms a V groove around the light emitting layer by performing mesa etching deeper than the light emitting layer of the semiconductor layer, and a reflective film made of gold on the side surface facing the light emitting layer of the V groove. After the surface of the semiconductor layer is oxidized with an oxidizing solution, the protective film is formed by annealing, so that a highly reliable device can be manufactured and compared with the conventional light emitting diode manufacturing method. There is an effect that the manufacturing method is simplified without requiring special equipment .
[0028]
In particular, by forming a thin electrode of gold on the upper surface of the semiconductor layer when forming the reflective film, the manufacturing method can be further simplified as compared with the conventional light emitting diode manufacturing method.
The light-emitting diode manufactured by the method of the present invention includes a V-groove formed around the light-emitting layer to a position deeper than the light-emitting layer of the semiconductor layer, and a reflection made of gold formed on a side surface facing the light-emitting layer of the V-groove. Since the film and the surface of the semiconductor layer are oxidized with an oxidizing solution and then provided with a protective film formed by annealing, the light emitted from the side surface of the light emitting layer is efficiently reflected toward the top surface, The luminance of the light emitting diode can be improved and a light emitting diode having directivity can be obtained. Furthermore, the reflectance can be further improved by using gold as the reflective film. In addition, since the light emitting diode element itself has directivity, complicated steps such as resin mold and cup bottom arrangement, which have been conventionally performed, are not required when a unit such as a photo interrupter or an optical fiber light source is formed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a light emitting diode of the present invention.
FIGS. 2A and 2B are cross-sectional views illustrating the manufacturing time of the light emitting diode of FIG.
3A is a cross-sectional view showing the manufacturing time of the light-emitting diode of FIG. 1; (B) is a top view which shows the time of manufacture of the light emitting diode of FIG.
4 (a), (b), (c), and (d) are cross-sectional views showing the manufacturing time of the light emitting diode of FIG.
FIG. 5 is a cross-sectional view of a conventional light emitting diode.
FIG. 6 is a cross-sectional view of a conventional light emitting diode.
FIG. 7 is a cross-sectional view of a conventional light emitting diode.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light emitting diode 2 ... p-type GaAs substrate (substrate)
3 ... p-type GaAlAs cladding layer (semiconductor layer)
4 ... GaAlAs active layer (semiconductor layer, light emitting layer)
5 ... n-type GaAlAs cladding layer (semiconductor layer, light emitting layer)
6 ... n-type GaAlAs contact layer (semiconductor layer)
7 ... p-type electrode 8 ... n-type electrode 9 ... natural oxide film (protective film)
11 ... V-groove 12 ... Reflective film

Claims (2)

In a method for manufacturing a light emitting diode in which a light emitting layer is stacked on a substrate,
V-grooves are formed around the light emitting layer by performing mesa etching deeper than the light emitting layer of the semiconductor layer,
Forming a reflective film made of gold on a side surface of the V-groove facing the light emitting layer;
A method for manufacturing a light emitting diode, comprising forming a protective film by oxidizing a surface of the semiconductor layer with an oxidizing solution and then annealing the surface. Light emitting diode manufacturing method according to claim 1, wherein when the reflective film is formed, an electrode made of gold on the upper surface of the semiconductor layer, characterized in that the thin film formation.

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