KR20120079308A - Light emitting diode and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a light emitting diode and a method of manufacturing the same, comprising: forming an etchable buffer layer on a growth substrate; Forming a light emitting structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer on the buffer layer; Providing a support substrate on the light emitting structure; Separating the buffer layer and the light emitting structure from the growth substrate; Selectively etching the buffer layer to form protrusions; And etching the surfaces of the buffer layer and the first conductive semiconductor layer to form a plurality of nanostructures that provide a texture, thereby improving light extraction efficiency and widening the light extraction surface.

Description

LIGHT EMITTING DIODE AND MANUFACTURING METHOD THEREOF

The present invention relates to a light emitting diode, and more particularly, to a light emitting diode having improved light extraction efficiency and a method of manufacturing the same.

Light Emitting Diode (LED) is a semiconductor device that converts electrical energy into light energy, and is composed of compound semiconductors that emit light of a specific wavelength according to energy band gap, and displays such as optical communication, mobile display, computer monitor, Its use is expanding from the LCD back light unit (BLU) to the area of illumination.

In particular, the development of general lighting using light emitting diodes has recently been fueled by the commercialization of mobile phone keypads, side viewers, camera flashes, etc. using gallium nitride (GaN) based light emitting diodes, which have been actively developed and used. Its applications such as backlight units of large TVs, automotive headlamps, and general lighting have moved from small portable products to larger, higher output, and more efficient products, requiring light sources that exhibit the characteristics required for such products.

One of the objects of the present invention is to provide a light emitting diode in which the light emitting efficiency is improved by improving the light extraction efficiency.

Another object of the present invention is to provide a method of manufacturing a light emitting diode in which the light emission efficiency is improved by improving the light extraction efficiency.

Method of manufacturing a light emitting diode according to the present invention comprises the steps of forming an etchable buffer layer on a growth substrate; Forming a light emitting structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer on the buffer layer; Providing a support substrate on the light emitting structure; Separating the buffer layer and the light emitting structure from the growth substrate; Selectively etching the buffer layer to form protrusions; And etching the surfaces of the buffer layer and the first conductive semiconductor layer to form a plurality of nanostructures that provide a texture.

In addition, the buffer layer may be an undoped-semiconductor layer, and the undoped-semiconductor layer may be an undoped-GaN layer.

In addition, the protrusion may be formed in a lattice shape or a stripe shape.

In this case, the plurality of nanostructures may be formed by wet etching, and the plurality of nanostructures formed on the buffer layer and the first conductive semiconductor layer may be formed in different sizes due to the difference in wet etching rates. .

The light emitting diode according to the present invention comprises: a light emitting structure comprising a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer formed on a support substrate; And a protrusion formed by etching a buffer layer on the light emitting structure, wherein a plurality of nanostructures are formed on surfaces of the first conductive semiconductor layer and the buffer layer, and the buffer layer may be an undoped semiconductor layer. The undoped-semiconductor layer may be an undoped-GaN layer.

In addition, the plurality of nanostructures formed on the buffer layer and the first conductivity type semiconductor layer may be formed in different sizes due to the difference in wet etching rates.

The light emitting diode and the method of manufacturing the same according to the present invention have the effect that the nanostructure is formed on the protrusion to improve the light extraction efficiency, and the light extraction surface is widened.

1A to 1I are schematic side cross-sectional views illustrating a method of manufacturing a light emitting device according to an embodiment of the present invention.
FIG. 2 is a plan view of a protrusion formed on the light emitting diode of FIG. 1.
3 is a side cross-sectional view schematically showing a light extraction path of a light emitting diode manufactured according to an embodiment of the present invention.

Hereinafter, embodiments according to the present invention will be described with reference to the accompanying drawings.

These examples are provided to illustrate the scope of the invention to those skilled in the art with respect to the present invention. Therefore, the present invention is not limited to the following embodiments, but may be embodied in various forms suggested by the claims of the present invention. Therefore, the shape and size of the components shown in the drawings may be exaggerated for more clear description, components having substantially the same configuration and function in the drawings will use the same reference numerals.

1A to 1I are schematic side cross-sectional views illustrating a method of manufacturing a light emitting device according to an exemplary embodiment of the present invention, FIG. 2 is a plan view of a protrusion 43 formed on the light emitting diode of FIG. 1, and FIG. 3. Is a side cross-sectional view briefly showing a light extraction path of a light emitting diode manufactured by an embodiment of the present invention.

First, as shown in FIG. 1A, a growth substrate 10 is prepared. The growth substrate 10 may include a sapphire substrate, a silicon carbide (SiC) substrate, a silicon (Si) substrate, a zinc oxide (ZnO) substrate, a gallium arsenide (GaAs) substrate, and a gallium phosphide (GaP) substrate. Any one of them can be used, and in this embodiment, a sapphire substrate can be used.

Next, a buffer layer 30 is formed on the growth substrate 10.

In general, the buffer layer 30 is a layer for protecting the first conductivity-type semiconductor layer 42 to be formed thereon, and is removed in the manufacturing process. However, in the present invention, the buffer layer 30 is formed as a protrusion 43 so that light Improve the extraction efficiency. As the buffer layer 30, a semiconductor layer that is not doped may be used, and in the present embodiment, an undoped-GaN 41 may be used. In addition, before the buffer layer 30 is formed, as shown in FIG. 1B, the sacrificial layer 20 is formed to separate the growth layer 10 by the chemical lift-off method. It is also possible to prevent 30 from being damaged.

Next, the light emitting structure 40 including the first conductive semiconductor layer 42, the active layer 45, and the second conductive semiconductor layer 47 is formed on the buffer layer 30.

The light emitting structure 40 includes a semiconductor layer having a multilayer structure, and the semiconductor layer includes a first conductive semiconductor layer 42, an active layer 45, and a second conductive semiconductor layer 47. The first conductive semiconductor layer 42 includes an n-type semiconductor layer, and the second conductive semiconductor layer 47 includes a p-type semiconductor layer.

As described above, an undoped-GaN is formed as a buffer layer 41 under the n-type semiconductor layer to protect the n-type semiconductor layer, which is the first conductivity-type semiconductor layer 42, which will be described later. The protrusion 43 is formed.

The n-type semiconductor layer and the p-type semiconductor layer employed in the present embodiment are Al _x n _y Ga _(1-xy) N composition formula (where 0≤x≤1, 0≤y≤1, 0≤x + y≤ N-type impurity and p-type impurity doped with a semiconductor material, and typically, GaN, AlGaN, InGaN. In addition, Si, Ge, Se, Te or C may be used as the n-type impurity, and the p-type impurity may be representative of Mg, Zn or Be.

In this embodiment, a GaN layer is used as a semiconductor layer, and an n-GaN layer may be used as the n-type semiconductor layer and a p-GaN layer may be used as the p-type semiconductor layer.

The light emitting structure 40 may be grown by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and hybrid vapor phase epitaxy (HVPE). .

The active layer 45 may be a layer for emitting visible light (eg, about 350-680 nm wavelength range, preferably 450-490 nm), and may have a single or multiple quantum well (MQW) structure. It is composed of a doped nitride semiconductor layer.

The active layer 45 alternately deposits a barrier layer and a well layer to form In _{1 - x} Ga _{1 - y} Al _{1 - z} N / In _{1 - x} Ga _{1 - y} Al _{1 - z} It is preferable to form an N-structure multiple quantum well, and select a ratio appropriate to the wavelength of light to be output by adjusting 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ z ≦ 1.

In this case, the active layer 45 may be grown by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or the like.

Next, as shown in FIG. 1D, the supporting substrate 50 is attached onto the light emitting structure 40.

The support substrate 50 is a substrate to which the light emitting structure 40 is attached, and various kinds of substrates may be used, and the support substrate 50 is not limited to a specific type of substrate.

Next, as shown in FIGS. 1E and 1F, the growth substrate 10 is formed on top by a physical method such as a laser lift-off (LLO) or a chemical lift-off method. The buffer layer 30 and the light emitting structure 40 are separated from the growth substrate 10 so that the buffer layer 30 is exposed.

In this case, as shown in FIG. 1E, if the sacrificial layer 20 described above remains under the buffer layer 30, it is preferable to remove the sacrificial layer 20.

Next, as shown in FIG. 1G, a portion of the buffer layer 30 is etched to form the protrusion 43 on the first conductive semiconductor layer 24.

Forming the protrusion 43 may be performed through a photolithography process.

The photolithography process may be specifically carried out by the process illustrated below.

After the photoreaction polymer is applied to the upper surface of the buffer layer 30 through a photolithography process to a thickness of 0.1 μm to 5 μm, the photoreaction polymer is spaced from 0.5 μm to 5 μm using a photoreaction and a mask. The photoresist pattern is formed by patterning into a predetermined shape. However, the photoresist pattern may not be formed on a predetermined portion of the buffer layer 30 in consideration of a portion where the n-type electrode 100 is to be formed in the following process.

In this embodiment, by using a lattice-shaped mask as the mask, the photoreaction polymer can be patterned to have a rectangular parallelepiped shape having a spacing of 0.5 μm to 5 μm.

The protrusions 43 formed by the mask may be formed to have a lattice pattern or a sprite pattern, as shown in FIGS. 2 (a) to 2 (c). It can be formed in various patterns such as.

In this case, the shape of the mask is preferably formed in accordance with the light extraction characteristics of the light emitting diode to be manufactured.

Thereafter, the rectangular parallelepiped photoresist pattern is reflowed at a temperature of 100 to 150 ° C. for about 1 minute to 5 minutes to form a hemispherical photoresist pattern on the buffer layer 30.

Then, the thickness of the buffer layer 30 is selectively etched using the hemispherical photoresist pattern as a mask. In this case, the etching process may be performed using BCl ₃ and HBr gas by the ICP-RIE method.

Then, since the hemispherical photoresist pattern and a portion of the buffer layer 30 are etched together, as shown in FIG. 1G, the hemispherical protrusion 43 is formed on the first conductive semiconductor layer 42. The buffer layer 30a having is etched.

Then, as shown in FIG. 1H, the buffer layer 30a is etched without a separate mask to form a buffer layer 30b on which the nanostructures 44 are formed. At this time, the upper surface of the first conductivity-type semiconductor layer 42 positioned below the buffer layer 30a is also partially etched so that a surface having a texture is formed like the surface of the buffer layer 30 having the protrusion 43. Is formed. In other words, a cone-shaped nanostructure 44 is also formed on the upper surface of the first conductive semiconductor layer. In this case, the etching process may be performed using the ICP-RIE method.

As such, a plurality of nanostructures 44 are formed on the surface of the protrusion 43 and the surface of the first conductive semiconductor layer by the etching process, and the direction and structure of the nanostructure 44 are etched. It is determined by the crystallization direction of and may have a fine structure having a light scattering effect. The present wet etching process for obtaining the preferred nanostructure 44 may be carried out using an etchant such as KOH at a temperature of about 75 to 100 ° C.

As such, when the undoped-GaN layer as the buffer layer 30 and the n-GaN layer as the first conductive semiconductor layer 42 are simultaneously etched by wet etching, the etching rate of the n-GaN layer is higher than that of the undoped-GaN. Since the nanostructure 44 is fast, the nanostructure 44 is formed in a different size from the buffer layer 30 and the first conductivity type semiconductor layer 42, and generally, the nanostructure 44 formed in the first conductivity type semiconductor layer is large. .

In addition, when the nanostructures 44 are formed by wet etching, as described above, the direction and structure of the nanostructures 44 may be variously modified by the crystallization direction of the layer to be etched, even on the same layer. There is a diversifying effect.

Next, as shown in FIG. 1I, an n-type electrode 100 is formed on the first conductive semiconductor layer 41a on which the plurality of nanostructures 44 are formed, and then laser scribing and wet type. The device isolation process may be performed through an etching or dry etching process, or the n-type electrode 100 may be formed after the device isolation process to form a light emitting diode device.

Meanwhile, in the present embodiment, in order to improve the current diffusion effect, the transparent conductor layer may be formed on the entire upper surface of the first conductivity-type semiconductor layer before the n-type electrode 100 is selectively formed.

Since the light emitting diode manufactured as described above is formed with a fine cone-shaped nanostructure 44 on the protrusion 43 having a large bend, as shown in FIG. 3, a cone structure is formed on the same plane. The light extraction path is diversified to improve the light extraction efficiency. In addition, the surface area is widened by the protrusions 43 and the nanostructures 44, so that the light emitting surface of the light emitting diodes can be widened.

10: growth substrate 20: sacrificial layer
30, 30a, 30b: buffer layer 40: light emitting structure
42, 42a: first conductive semiconductor layer 43: protrusion
44 nanostructure 45 active layer
47: second conductivity type semiconductor layer 50: support substrate
100: n-type electrode

Claims (11)

Forming an etchable buffer layer on the growth substrate;
Forming a light emitting structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer on the buffer layer;
Providing a support substrate on the light emitting structure;
Separating the buffer layer and the light emitting structure from the growth substrate;
Selectively etching the buffer layer to form protrusions; And
And etching a surface of the buffer layer and the first conductive semiconductor layer to form a plurality of nanostructures that provide a texture.
The method of claim 1,
The buffer layer is a light emitting diode manufacturing method, characterized in that the undoped-semiconductor layer.
The method of claim 2,
The undoped semiconductor layer is a light emitting diode manufacturing method, characterized in that the undoped-GaN layer.
The method of claim 1,
The protrusion is a light emitting diode manufacturing method, characterized in that the grid or stripe (stripe) type.
The method of claim 1,
The plurality of nanostructures is a light emitting diode manufacturing method, characterized in that formed by wet etching.
The method of claim 5,
The plurality of nanostructures formed on the buffer layer and the first conductivity type semiconductor layer is a light emitting diode manufacturing method, characterized in that formed in different sizes by the difference in wet etching rate.
A light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer formed on the support substrate; And
On the light emitting structure, the buffer layer comprises a protrusion formed by etching,
A light emitting diode, characterized in that a plurality of nanostructures are formed on the surface of the first conductive semiconductor layer and the buffer layer.
The method of claim 7, wherein
The buffer layer is a light emitting diode, characterized in that the undoped-semiconductor layer.
The method of claim 8,
The undoped-semiconductor layer is an undoped-GaN layer.
The method of claim 7, wherein
The plurality of nanostructures are light emitting diodes, characterized in that formed by wet etching.
The method of claim 10,
The plurality of nanostructures formed on the buffer layer and the first conductivity type semiconductor layer are light emitting diodes, characterized in that formed in different sizes by the difference in wet etching rate.

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