KR100941136B1 - Light emitting diode in which electrode with mesh structure is formed and method for manufacturing the same - Google Patents

Abstract

The present invention discloses a light emitting device having an electrode layer formed of a mesh structure and a method of manufacturing the same. According to the present invention, an electrode layer having a mesh structure is formed on a semiconductor layer, whereby transmittance is improved and contact resistance is reduced, thereby obtaining a light emitting device having good electrical characteristics. In addition, the present invention forms an electrode layer having a mesh structure using Ni, Pt, Pd, Rh and Ag having a high work function on a semiconductor layer (particularly, a P-GaN layer), thereby ensuring good ohmic contact characteristics. In addition to these effects, such a material is cheaper than ITO, which is widely used as a transparent electrode layer in the prior art, thereby reducing the manufacturing cost of the light emitting device. In addition, the present invention can easily adjust the spacing of the mesh structure and the width of the electrode string by adjusting the size and spacing of the columnar pattern used to form the electrode layer of the mesh structure, so that the light extraction efficiency and electrical characteristics are considered There is an effect that can produce a light emitting device.

Description

Light emitting diode in which electrode with mesh structure is formed and method for manufacturing the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device and a method of manufacturing the same, and more particularly, to a light emitting device having an electrode layer having a mesh structure and a method of manufacturing the same.

GaN-based light emitting diodes (LEDs) that emit blue, green, and UV light, as well as small and large display boards, are widely used in society such as indicators, backlights of LCD devices, and backlights of mobile phone keypads.

Currently, cyan LEDs are replacing existing traffic lights, various LEDs are used as light sources for automobiles and indirect lighting, and when the LEDs with higher light efficiency are developed, current lamps can be replaced with LEDs.

In order to manufacture LEDs used in various fields, a thin film is conventionally formed on a sapphire substrate or a SiC substrate by a method such as metal organic chemical vapor deposition (MOCVD) to form an LED using GaN material.

1A and 1B are diagrams illustrating a method of manufacturing a light emitting device using the conventional technique. Referring to FIGS. 1A and 1B, a conventional method forms a buffer layer (Un-doped GaN) 12 by MOCVD on a substrate 11 such as sapphire, SiC, GaN, and the like, and then forms N-GaN on the buffer layer 12. A layer 13, an active layer (In _x Ga _1-x N (x = 0 to 1); 14), and a P-GaN layer 15 are sequentially formed (see FIG. 1A (a)).

Thereafter, heat treatment is performed at about 600 ° C. for about 20 minutes to activate impurities in the P-GaN layer 15, and then a portion of the N-GaN layer 13 is exposed to form an N-type electrode. Etching is performed from the GaN layer 15 downward (see (b) of FIG. 1A).

Thereafter, a thin ohmic contact metal (or transparent conductive thin film) 16 is formed on the entire surface of the P-GaN layer 15 (see (c) of FIG. 1A), and a pad for bonding upon assembling the chip thereon. P-type ohmic contact 17 is formed (see (d) of FIG. 1B).

Thereafter, on the etched N-GaN layer 13, an electrode layer 18 which is simultaneously used as ohmic and pad metal is formed to complete the chip (see (e) of FIG. 1B).

As shown in FIGS. 1A and 1B, a large work function of about 7.5 eV is conventionally used to realize ohmic contact between a metal to form a p-GaN layer and an electrode due to a large bandgap energy of a GaN material. It was necessary to form the electrode layer on the p-GaN layer using a metal material having a). Generally Ni having a high work function is used as a p-GaN ohmic material. However, the electrode layer using the metal material has a problem that the luminous efficiency is lowered due to the low transmittance while the ohmic contact is made.

Recently, many studies have been conducted to form an electrode layer in the form of a transparent conductive oxide (TCO) layer on a p-GaN layer using transparent electrode materials capable of ohmic contact with low light absorption. Among the materials of ITO, IZO, CIO, ZnO, etc., Indium Tin Oxide (ITO) is in the spotlight as a transparent electrode material of LED because of its relatively good electrical conductivity and transparent band-gap in the visible region of 2.5 eV or more.

However, the TCO has a high driving voltage for driving the light emitting device due to high contact resistance in spite of excellent optical characteristics.

The problem to be solved by the present invention is to provide a light emitting device having a high transmittance and good ohmic contact characteristics and a light emitting device and a manufacturing method thereof.

The light emitting device of the present invention for solving the above problems is a semiconductor layer for generating light; And an electrode layer formed in a mesh structure on the semiconductor layer.

In addition, the electrode layer described above is spaced apart from each other a plurality of first electrode string formed in parallel; And a plurality of second electrode rows spaced apart from and parallel to each other to cross the first electrode rows.

In addition, the above-described first and second electrode strings may be formed to be orthogonal to each other.

In addition, the electrode layer described above may be formed of any one of Ni, Pt, Pd, and Rh.

In the semiconductor layer described above, an N-GaN layer, an active layer, and a P-GaN layer may be sequentially formed on the substrate, and the electrode layer may be formed on the P-GaN layer.

On the other hand, the light emitting device manufacturing method of the present invention for solving the above problems comprises the steps of (a) forming a semiconductor layer for generating light on the substrate; And (b) forming an electrode layer in a mesh structure on the semiconductor layer.

In addition, the above step (b) comprises the steps of (b1) forming a columnar aligned pattern on the semiconductor layer; (b2) forming an electrode layer having a mesh structure by depositing an electrode layer material in a region between the pillar-shaped patterns; And (b3) removing the pattern.

In addition, in the step (b2) described above, the electrode layer material may be deposited on the region between the pillar-shaped patterns by reducing the angle at which the electrode layer forming material is incident by tilting the substrate with respect to the source emitting the electrode layer forming material.

In addition, in the step (b2) described above, the columnar patterns may be aligned in line with the source to deposit an electrode layer material in an area between the columnar patterns.

In addition, step (b2) described above may include forming a first electrode string by depositing an electrode layer material in a region between the pillar-shaped patterns; And depositing an electrode layer material in a region between the pillar-shaped patterns so that the substrate on which the first electrode string is formed is rotated by 90 degrees to be orthogonal to the first electrode string.

In addition, the above-described method, by adjusting the spacing between the columnar patterns to adjust the line width of the electrode strings forming the mesh structure, and by adjusting the size of the columnar pattern to adjust the spacing between the electrode strings forming the mesh structure Can be.

In addition, the electrode layer described above may be formed of any one of Ni, Pt, Pd, and Rh.

As described above, according to the present invention, the transmittance is improved by forming an electrode layer having a mesh structure on the semiconductor layer, and the contact resistance is reduced, thereby obtaining an effect of obtaining a light emitting device having good electrical characteristics.

In addition, the present invention by forming the electrode layer having a mesh structure using a high work function Ni, Pt, Pd, Rh and the like on the semiconductor layer (especially P-GaN layer), it is possible to ensure good ohmic contact characteristics In addition, such a material is cheaper than ITO, which is widely used as a transparent electrode layer in the prior art, thereby reducing the manufacturing cost of the light emitting device.

In addition, the present invention can easily adjust the spacing of the mesh structure and the width of the electrode string by adjusting the size and spacing of the columnar pattern used to form the electrode layer of the mesh structure, so that the light extraction efficiency and electrical characteristics are considered There is an effect that can produce a light emitting device.

Hereinafter, a nitride light emitting device in which the electrode layer of the present invention is formed on the nitride layer will be described.

2 is a view showing the structure of an electrode layer formed in accordance with a preferred embodiment of the present invention. 2, the electrode layer 700 of the present invention is formed in a mesh structure on a semiconductor layer (p-GaN layer 500 of the nitride layer) formed by various methods of the prior art.

Specifically, the plurality of first electrode rows 710 and the plurality of first electrode rows 710 formed on the p-GaN layer and spaced apart from each other in parallel to each other in the first direction are spaced apart from each other in the second direction in parallel. It is composed of a plurality of second electrode string 720 formed.

In a preferred embodiment of the present invention, the first direction and the second direction are directions perpendicular to each other, such that the first electrode string 710 and the second electrode string 720 are orthogonal to each other to form a rectangular mesh structure. Although the present invention is not limited thereto, the first electrode pole 710 and the second electrode string 720 may cross each other at an arbitrary angle and may have a rectangular mesh structure that is not rectangular.

Meanwhile, the first electrode string 710 and the second electrode string 720 constituting the electrode layer 700 according to the preferred embodiment of the present invention shown in FIG. 2 are formed to be orthogonal to each other. It is preferable that a) is 10 micrometers-10 mm, It is preferable that the width | variety w of each electrode string is 10 micrometers-10 mm, and it is preferable that the thickness of each electrode string is 10 micrometers-10 micrometers.

3 to 6 illustrate a method of forming an electrode layer 700 according to a preferred embodiment of the present invention. First, referring to FIG. 3, the buffer layer 200, the first semiconductor layer 300, the active layer 400, and the second semiconductor layer 500 are sequentially formed on the substrate 100, and the second semiconductor layer 500 is formed. The photoresist 600 is formed thereon.

In a preferred embodiment of the present invention, the substrate 100 may be a silicon substrate, a sapphire substrate, a SiC substrate, a GaN substrate, or the like, and the buffer layer 200 may be formed as an un-doped GaN layer by MOCVD. .

In addition, the first semiconductor layer 300 is an N-GaN layer, the active layer 400 is In _x Ga _1-x N (x = 0 to 1), and the second semiconductor layer 500 is sequentially disposed on the buffer layer 200. ) Are formed of P-GaN layers, respectively, and the photoresist 600 is formed on the second semiconductor layer 500 with a thickness of 1 nm to 10 mm.

The photoresist 600 is then etched using Holo lithography or other known applicable methods to form a pattern in which columnar photoresist materials are aligned at regular intervals.

4A is a diagram showing a cross section in which a pattern is formed, and FIG. 4B is a diagram showing a plane in which a pattern is formed. Referring to FIG. 4B, as will be described later with reference to FIGS. 5A to 6, the width of the electrode rows becomes W1 or W2, and the interval between the electrode rows becomes a1 or a2, depending on the direction in which the electrode material is deposited. That is, the width of the electrode rows is controlled by the spacing interval of the columnar pattern, the spacing between the electrode columns is adjusted by the size (diameter) of the columnar pattern.

Thereafter, as shown in FIG. 5A, metals having a high work function exhibiting ohmic contact characteristics with respect to the P-GaN layer between the pillar-shaped patterns may be used, and in the preferred embodiment of the present invention, Ni, An electrode layer forming material such as Pt, Pd, Rh, and Ag is deposited to form a first electrode string 710 in the region between the photoresist patterns.

At this time, when the substrate is tilted with respect to the e-beam source 900 or the like that emits the electrode layer forming material, the incident angle at which the deposition material is incident becomes close to 90 degrees with respect to the normal of the substrate, that is, in the horizontal direction with respect to the substrate. The electrode material is deposited, so that the electrode material is deposited in the regions between the columnar patterns arranged at regular intervals, but the electrode material is deposited in the region 520 of the second semiconductor layer corresponding to the back side of the columnar pattern. It doesn't work. Thus, the electrode string is formed in the region between the columnar patterns. FIG. 5B is a cross-sectional view taken along the line AA ′ of FIG. 5A.

When the first electrode string 710 is formed, as shown in FIG. 6, the substrate is rotated 90 degrees to deposit the electrode material in the same manner as the first electrode string 710 to form the first electrode string 710. ) To form a second electrode string 720. The second electrode string 720 is formed by depositing a portion by rotating 90 degrees to the left with respect to the first electrode string 710 and by depositing a portion by rotating 90 degrees to the right with respect to the first electrode string 710. Can be.

In addition, the first electrode string 710 and the second electrode string 720 may be simultaneously formed while rotating the substrate by 90 degrees with respect to the source 900 emitting the electrode forming material at regular time intervals.

After the first electrode string 710 and the second electrode string 720 are formed, the photoresist patterns 600 positioned between the first electrode string 710 and the second electrode string 720 are removed to thereby remove the photoresist patterns 600. The electrode layer 700 of the mesh structure as shown is completed.

Thereafter, the electrode pad is formed on the electrode layer 700 in the same manner as a general light emitting device manufacturing process, and then a post process is performed to complete the device.

7 and 8 are graphs of reflectance, transmittance, and absorbance calculated as a function of wavelength when the electrode layer 700 of the mesh structure is formed of Ag according to a preferred embodiment of the present invention.

 FIG. 7 shows a transmittance of 80% or more in the visible region when the gap between the rows of electrodes is 400 nm, the width of the rows of electrodes is 100 nm, and the height of the electrodes is 500 nm. In this sub-micron electrode string width, the electrical characteristics of the electrode are expected to be largely no problem.

FIG. 8 is a calculated value of the transmittance of an electrode when the height of the electrode string is changed from 100 nm to 500 nm in 100 nm units in FIG. 7. It can be seen that when the electrode thickness is 100 nm, the transmittance shows an improvement of 90% or more in the visible light region.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1A and 1B illustrate a method of manufacturing a light emitting device according to the prior art.

2 is a view showing the structure of an electrode layer formed in accordance with a preferred embodiment of the present invention.

3 to 6 illustrate a method of forming an electrode layer according to a preferred embodiment of the present invention.

7 and 8 are graphs of reflectance, transmittance, and absorbance calculated as a function of wavelength when an electrode layer having a mesh structure is formed of Ag according to a preferred embodiment of the present invention.

Claims (12)

delete delete delete delete delete delete (a) forming a semiconductor layer that generates light on the substrate; And (b) forming an electrode layer in a mesh structure on the semiconductor layer, Step (b) is (b1) forming a columnar aligned pattern on the semiconductor layer; (b2) forming an electrode layer of the mesh structure by depositing an electrode layer material in an area between the pillar-shaped patterns; And (b3) a method of manufacturing a light emitting device, comprising the step of removing the pattern. The method of claim 7, wherein step (b2) And depositing an electrode layer material in an area between the columnar patterns by tilting the substrate with respect to a source emitting the electrode layer forming material to reduce an angle at which the electrode layer forming material is incident. The method of claim 8, wherein step (b2) And arranging the columnar patterns in a line with respect to the source to deposit an electrode layer material in an area between the columnar patterns. The method of claim 9, wherein step (b2) Depositing an electrode layer material in a region between the pillar-shaped patterns to form a first electrode string; And And depositing an electrode layer material in a region between the pillar-shaped patterns such that the substrate on which the first electrode string is formed is rotated by 90 degrees to be orthogonal to the first electrode string. Light emitting device manufacturing method. The method of claim 7, wherein Adjusting the spacing between the columnar patterns to adjust the line width of the electrode strings forming the mesh structure, and by adjusting the size of the columnar pattern to adjust the spacing between the electrode lines forming the mesh structure. A light emitting element manufacturing method characterized by the above-mentioned. The method according to any one of claims 7 to 11, The electrode layer is formed of any one of Ni, Pt, Pd, Rh, and Ag.

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