KR20070119427A - Light-emitting diode shaped by decline etching and manufacturing method thereof - Google Patents

Abstract

A slope-etched LED(light emitting diode) is provided to increase light extraction efficiency by lowering the total internal reflection ratio of photons emitted from a light emitting layer through a sloped transformation of a chip shape and by increasing partial transmissivity of the lateral surface of the chip. A slope-etched LED includes a chip formed of a predetermined shape which lowers the total internal reflection ratio of photons generated from a light emitting layer. The predetermined shape of the chip including a sloped surface is formed by a dry etch process while the chip is sloped. The angle of the sloped surface is 0-90 degrees.

Description

Inclined-etched light emitting diode and its manufacturing method {LIGHT-EMITTING DIODE SHAPED BY DECLINE ETCHING AND MANUFACTURING METHOD THEREOF}

1 is a cross-sectional view showing a reflection of photons emitted from a light emitting diode according to an embodiment of the prior art.

2 is a cross-sectional view illustrating an etching method of a light emitting diode and a structure thereof according to an embodiment of the prior art.

3 is a cross-sectional view and a plan view illustrating a tilted etching method and a structure thereof of a light emitting diode according to an exemplary embodiment of the present invention.

4 is a cross-sectional view showing a reflection of photons emitted from a light emitting diode according to an embodiment of the present invention.

5 is a cross-sectional view and a plan view showing the reflection and re-reflection of the photons emitted from the light emitting diode according to an embodiment of the present invention.

{Description of symbols for main parts of the drawing}

10,20: substrate 11,21: epitaxial layer

12,22: photo-resist 23: metal electrode layer

24: reflective metal

The present invention relates to a light emitting diode and a method of manufacturing the same, and more particularly, to lower the internal total reflectance of photons generated in the light emitting layer of the light emitting diode, and to re-reflect the photons emitted in an undesirable direction from the light emitting diode The present invention relates to a high-efficiency light emitting diode and a method of manufacturing the same, which improve light extraction efficiency by inducing to be emitted in a desired direction.

Generally, a light emitting diode is a diode in which an active layer capable of emitting light is located between a p-type and n-type semiconductor thin film layer.

Light emitting diodes are widely used in modules ranging from short distance communication to large display devices such as various outdoor billboards.

In order to increase the efficiency of such a light emitting diode, it is necessary to effectively extract photons emitted from the active layer of the light emitting diode, and to transmit or reflect the extracted photons in a desired direction.

For this purpose, studies have been actively conducted on buffer layers or intermediate layers which can reduce the density of defects due to lattice mismatch between the semiconductor layer of the light emitting diode and the layer to be deposited, and the arrangement and structure of these layers.

In addition, studies have been made to increase the photoemission efficiency of photons in terms of the shape of the semiconductor chip of the light emitting diode.

The shape of the semiconductor chip is generally formed in the etching step of the semiconductor layer. In the semiconductor process, a conventional technique for etching a metal film is to deposit a metal film on a material wafer, apply a photosensitive material, and then expose and develop a circuit pattern. Since the metal film is etched, the metal film is etched in a substantially upright state with respect to the wafer when viewed in cross section.

In this case, the semiconductor chip is manufactured in the shape of a cube or a cuboid. When photons generated in the inner light emitting layer come out, reflection and transmission due to the difference in refractive index occur at the interface between the chip and the external medium. As can be seen in Figure 1, when the photon has a reflection angle of more than the critical angle, a total reflection phenomenon occurs in which all of the reflection is reflected at the interface between the chip and the external medium. In this case, if the shape of the chip is a cube or a cuboid, photons totally reflected on the surface are more likely to be totally reflected on the side, and infinite reflection may occur inside the chip. As a result, the photons generated in such a case are more likely to disappear as heat is trapped or collided with defects inside the chip, and thus the light extraction efficiency is very low.

As one of the methods for overcoming the above problems, the prior art of deforming the shape of the chip has been studied, and there is a method of deforming the shape of the chip by a wet etching method.

2 is a cross-sectional view schematically illustrating a structure of an LED with a modified shape of a chip and an etching method thereof according to an embodiment of the related art.

Referring to FIG. 2, group III-V compounds, such as indium phosphorus (InP) and gallium arsenide (GaAs), which are generally wet-etched, are grown on the substrate 10 as an epitaxial layer 11 and used as a photoresist 13. The patterned semiconductor is etched along the etching direction in the etching process (a).

It can be seen that due to the wet etching, anisotropic etching with different etching speeds occurs in a specific surface (b), and the shape of the chip has a top surface direction of the substrate and a direction of the outer surface of the etched epitaxial layer, respectively ( 100) and (111) inclined surfaces are included.

In the end, the finished chip shape is the same as (c) and has a truncated pyramid structure.

However, there is a limit in effectively extracting photons generated by the prior art, and there is a problem in that the light extraction is not greatly improved due to the insufficiency to prevent total reflection of photons that are structurally formed on the side of the chip. In the manufacturing method of the present invention, it is difficult to form an inclined surface of the chip by an etching process.

An object of the present invention is to reduce the internal total reflectance of photons generated in the active layer of the light emitting diode to solve the problems of the prior art as described above, and to increase the light extraction efficiency through the re-reflection of the photons emitted from the chip To provide a diode.

Another object of the present invention is to provide a method of manufacturing a light emitting diode which performs an etching process in a state of an inclined chip to increase the luminous efficiency of light.

In order to achieve the above object, the obliquely etched light emitting diode of the present invention includes a chip molded into a predetermined shape to lower the total internal reflectance of photons generated in the light emitting layer.

In the present invention, the predetermined chip shape includes an inclined inclined surface, and the chip shape including the inclined inclined surface is formed by performing a dry etching method in the inclined state of the chip.

In the present invention, the angle of the inclined inclined surface includes 0 ° to 90 °.

In the present invention, preferably, the dry etching method is reactive ion etching (RIE), capacitively coupled plasma etching (CCP), inductively coupled plasma etching (ICP). And electron resonance plasma etching (Electron Cyclotron Resonance, ECR) is any one selected from the method.

In the present invention, the predetermined chip shape includes a polygonal or cylindrical shape formed by performing a dry etching method while stepping or continuously rotating the chip in an inclined state.

In the present invention, the predetermined shape further includes depositing a reflective metal on the surface of the molded chip to reflect back photons escaped from the molded chip upwards.

In the present invention, the reflective metal includes a metal having high reflectance in the visible, infrared, and ultraviolet wavelength ranges. Preferably, the reflective metal is nickel (Ni), aluminum (Al), gold (Au), or silver. (Ag), palladium (Pd), and platinum (Pt) any one selected from metals.

In order to achieve the above object, a method of manufacturing an obliquely etched light emitting diode of the present invention comprises the steps of growing an epitaxial thin film on a substrate and applying a photo-resist (PR) on the epitaxy deposition layer and exposing as a pattern. Developing and etching the chip to a predetermined shape including an inclined surface by performing a dry etching method while stepping or continuously rotating the chip at an angle of 0 ° to 90 °.

The method may further include depositing a reflective metal on the surface of the formed chip after the etching, wherein the reflective metal includes a metal having a high reflectance in the visible, infrared, and ultraviolet wavelength ranges. .

In the present invention, preferably, the reflective metal is any one selected from nickel (Ni), aluminum (Al), gold (Au), silver (Ag), palladium (Pd), and platinum (Pt). .

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

3 is a cross-sectional view (a) and a plan view (b) illustrating an etching method and a structure thereof according to an inclined etched light emitting diode according to an embodiment of the present invention.

In the above embodiment, the predetermined chip shape for lowering the probability that the photons generated in the light emitting layer of the light emitting diode are totally reflected at the interface between the chip and the air is preferably configured to include an inclined surface having a slanted side surface.

Referring to FIG. 3, in order to modify the shape of a chip, an epitaxial layer 21 including an active layer is formed on a substrate 20, and a circuit is patterned with a photoresist 22 on the substrate 20 to etch the light emitting diode. During the process, the entire semiconductor device is tilted to be etched.

Since the etching method mainly uses a dry etching method using plasma, radicals or ion particles formed by ionizing and decomposing a source gas are anisotropically etched by vertical collision from the upper surface of the semiconductor chip. As shown in FIG. 3, when the semiconductor chip itself is tilted and processed by the etching method, the side surface of the epitaxial layer as shown in FIG. 3A may be inclined.

In addition, according to the inclined dry etching method, it is possible to manufacture a variety of shapes on the top view of the semiconductor chip in addition to the side shape of the chip of the light emitting diode by changing the chip rotation method. That is, as can be seen in Figure 3 (b), if the semiconductor chip is rotated uniformly as a whole, the top surface of the chip can be manufactured in a circular shape, and if rotated stepwise by a predetermined angle the top surface of the chip is produced in a polygonal shape can do. The upper part of the chip can be manufactured in the shape of a quadrangle when the fourth stage is rotated at a 90 degree angle.

4 is a cross-sectional view of a light emitting diode according to an embodiment of the present invention, showing a reflection of photons emitted from a light emitting layer.

In the above embodiment, the epitaxial layer 21 formed on the substrate is composed of p-type gallium phosphide (GaP) and n-type gallium phosphide (GaP), and aluminum indium gallium phosphide (AlGaInP) is used as an active layer. And a light emitting diode chip structure including a metal electrode layer 23 on the bottom surface thereof.

In the above embodiment, photons generated in the active layer of aluminum indium gallium may be internally refracted by the crystal lattice and transmitted to the front part of the chip, or may be incident at an angle greater than the critical angle and totally reflected at the interface between the chip and the air and partially transmitted to the side of the chip. do.

Since the inclined etched light emitting diode according to the embodiment is partially transmissive through the inclined structural side of the side surface and the photons totally reflected through this, the probability of total reflection is lower than that of the conventional light emitting diode chip.

5 is a cross-sectional view (a) and a plan view (b) illustrating the reflection and re-reflection of photons emitted from an inclined etched light emitting diode according to an embodiment of the present invention.

In the above embodiment, the chip formed so as to incline the side surface by the dry etching method in the inclined state is deposited epitaxial layer 21 and the metal electrode layer 23 on the substrate 20. In addition, a highly reflective multilayer distributed Bragg reflector formed between the substrate 20 and the epitaxial layer 21 to reduce the absorption of the substrate to the light portion emitted toward the substrate 20 to achieve more directional and improved light emission characteristics. (DBR) Mirror layer included. A highly reflective multilayer distributed Bragg reflector (DBR) mirror layer typically refers to an alternating growth of two layers with different refractive indices in order to reflect light of a specific wavelength in a semiconductor laser or a light emitting diode.

In this embodiment, a reflecting metal 24 is deposited on the top of the formed chip which allows the photons emitted inside the active layer to totally reflect and partially reflect to the side and thus reflect and utilize the photons to be lost.

FIG. 5A illustrates a chip in which a highly reflective multilayer distributed Bragg reflector (DBR) mirror layer, an epitaxial layer 21 and a metal electrode layer 23 are deposited and formed according to the above embodiment. It is sectional drawing which shows the light emitting diode structure in which the reflective metal is arrange | positioned on the upper substrate, and shows the reflection form of photon.

A plan view of the light emitting diode according to the embodiment and viewed from above is as shown in FIG. That is, the metal electrode layer 23 is disposed at the center of the rectangular chip by step rotation at an angle of 90 degrees, and the reflective metal 24 reflecting photons emitted from the chip is formed around the molded chip. Able to know.

In one embodiment of the present invention, the inclined etching method is a dry etching method, which is a plasma etching method, depending on the method of forming plasma, reactive ion etching (RIE), capacitively coupled plasma etching method (Capacitively Coupled Plasma) , CCP), Inductively Coupled Plasma (ICP), and Electron Resonance Plasma Etch (ECR). The chip of the light emitting diode is formed by the above method, but preferably, reactive ion etching (RIE) and inductively coupled plasma etching (ICP) are used.

In general, the etching method is to anisotropically etch the substrate and the materials on the substrate by colliding radicals or ionic particles generated by decomposition or ionization of the source gas.

The inclination angle to be etched is preferably in the range of more than 0 ° and less than 90 °.

In the above embodiment, the reflective metal for re-reflecting the photons escaped from the molded chip of the obliquely etched light emitting diode according to the present invention in an upward direction is a metal having high reflectance in the visible, infrared and ultraviolet wavelength ranges. desirable.

According to the characteristics of the light emitting diode, photons are generated in a desired wavelength region, and a metal having the highest reflectance in the wavelength region can be selected.

Generally, metals having high light reflectance include nickel (Ni), aluminum (Al), gold (Au), silver (Ag), palladium (Pd), and platinum (Pt).

As described above, the present invention has been described with reference to a preferred embodiment of the present invention, but those skilled in the art can vary the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. It will be appreciated that modifications and variations can be made.

As described above, according to the present invention, through the inclined deformation of the chip shape, it is possible to lower the total reflectance inside the chip of the photon emitted from the light emitting layer and increase the partial transmittance to the side to increase the light extraction efficiency as a whole.

In addition, there is an effect of increasing light extraction efficiency by reflecting back photons that can be lost due to irregular transmission directions so that photons can be emitted in a desired direction.

As a result, the light emitting diode produced using the present invention has an effect of providing a high value added reliable product in terms of efficiency and quality of light extraction efficiency is increased.

Claims (12)

An inclined etched light emitting diode comprising a chip formed into a predetermined shape to lower the total internal reflectance of photons generated in the light emitting layer. The inclined etched light emitting diode of claim 1, wherein the predetermined chip shape includes an inclined inclined surface. The inclined etched light emitting diode of claim 2, wherein an angle of the inclined surface is 0 to 90 degrees. The inclined etched light emitting diode of claim 2, wherein the chip shape including the inclined inclined surface is formed by performing a dry etching method while the chip is inclined. The method of claim 4, wherein the dry etching method comprises reactive ion etching (RIE), capacitively coupled plasma etching (CCP), and inductively coupled plasma etching (ICP). And an electron resonance plasma etching method (Electron Cyclotron Resonance, ECR), characterized in that any one of the methods selected from the etched light emitting diode. The inclined chip according to claim 1 or 2, wherein the predetermined chip shape includes a polygonal column or a cylindrical shape formed by performing a dry etching method while stepping or continuously rotating the chip in an inclined state. Etched Light Emitting Diode. 3. The method of claim 1 or 2, wherein the predetermined shape further comprises depositing a reflective metal on the surface of the shaped chip to reflect back photons escaped from the shaped chip upwards. Inclined etched light emitting diodes. The inclined etched light emitting diode of claim 7, wherein the reflecting metal is a metal having high reflectance in the visible, infrared, and ultraviolet wavelength ranges. The metal of claim 8, wherein the reflective metal is any one selected from nickel (Ni), aluminum (Al), gold (Au), silver (Ag), palladium (Pd), and platinum (Pt). Inclined etched light emitting diodes. Growing an epitaxial thin film on the substrate; Applying photo-resist (PR) onto the epitaxy deposition layer, and exposing and developing the photo pattern according to a pattern; And And etching the chip into a predetermined shape including an inclined surface by performing a dry etching method while stepping or continuously rotating the chip at an angle of 0 ° to 90 °. Method of manufacturing a diode. The method of claim 10, further comprising depositing a reflective metal on a surface of the formed chip after the etching, wherein the reflective metal is a metal having high reflectance in visible, infrared, and ultraviolet wavelength regions. Method of manufacturing a slope-etched light emitting diode, characterized in that. The metal of claim 11, wherein the reflective metal is any one selected from nickel (Ni), aluminum (Al), gold (Au), silver (Ag), palladium (Pd), and platinum (Pt). Method of manufacturing the etched light emitting diode to be.

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