KR20070073042A - Vertical type light emitting device and fabricating method thereof - Google Patents

Abstract

A vertical type light emitting device and a fabricating method of the same are provided to prevent deterioration of electrical characteristics such as short circuit and leakage current by forming a high reflective layer on a light emitting structure and a p-ohmic layer. A light emitting structure(110) includes an active layer for generating the light. An ohmic layer(120) is formed on the light emitting structure. A high reflective layer(130) is formed to cover the remaining region of the light emitting structure except for a lower part and the ohmic layer. One or more openings are formed in the high reflective layer in order to expose a part of the ohmic layer. A seed metal(140) is formed on the high reflective layer in order to fill up the opening. A first electrode(150) is formed on the seed metal. A second electrode(160) is formed on the lower part of the light emitting structure.

Description

Vertical Type Light Emitting Device And Fabricating Method Thereof}

1 is a cross-sectional view for schematically illustrating the structure of a vertical light emitting device according to the prior art.

2A to 2H are cross-sectional views schematically illustrating a method of manufacturing a vertical light emitting device according to the prior art.

3 is a cross-sectional view for explaining a preferred embodiment of the vertical light emitting device according to the present invention.

4A to 4I are cross-sectional views for explaining a preferred embodiment of the vertical light emitting device manufacturing method according to the present invention.

5 is a cross-sectional view schematically illustrating a structure of a light emitting structure formed in FIG. 4B.

6 is a plan view of FIG. 4E.

<Description of main parts of drawing>

100. Substrate 110. Light emitting structure

110a. n-semiconductor layer 110b. Active layer

110c. p-semiconductor layer 120. p-Ohmic Layer

130. Oxide-based high reflective film 140. Seed metal

150. First electrode 160. Second electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical light emitting device and a method of manufacturing the same. In particular, by forming a high reflective film thickly using an oxide-based material, the reflectivity of the light emitting device can be improved, and a short circuit of the light emitting device can be achieved. The present invention relates to a vertical light emitting device capable of preventing degradation of electrical characteristics such as) and leakage current, and a method of manufacturing the same.

Hereinafter, a vertical light emitting device and a method of manufacturing the same according to the related art will be described with reference to the accompanying drawings and a problem will be described.

1 is a cross-sectional view schematically illustrating the structure of a vertical light emitting device according to the prior art.

As shown in the figure, a conventional vertical light emitting device generally includes a light emitting structure 11; p-Ohmic Layer 12; Reflective film 13; Seed metal 14; First electrode 15; It consists of the second electrode 16.

First, the light emitting structure 11 includes an active layer for generating light, specifically, an n-GaN layer, an active layer, and a p-GaN layer are sequentially stacked, and the active layer is also gallium nitride (GaN). ) Is composed of a series of materials.

The p-ohmic layer 12 is formed on the light emitting structure 11.

In addition, a reflective film 13 is formed on a side surface of the light emitting structure 11 and the p-ohmic layer 12 of a metal-based material such as aluminum (Al) or silver (Ag). 13 is a passivation layer, and also serves to insulate the side surface of the light emitting structure 11.

On the other hand, the seed metal 14 is formed on the front surface of the p-omic layer 12 and the outside of the reflective film 13 along the side portion.

In this case, the seed metal 14 is a seed layer for forming the first electrode 15, and is a layer for plating or depositing the first electrode 15 well.

Subsequently, the first electrode 15 is formed on an upper front surface of the seed metal 14, and the first electrode 15 is made of a metal having good electrical conductivity such as copper (Cu).

Lastly, a second electrode 16 is formed below the light emitting structure 11, and the second electrode 16 has a pad shape in order to emit light through the bottom of the light emitting structure 11. It is formed of a transparent electrode material.

2A to 2H are cross-sectional views schematically illustrating a method of manufacturing a vertical light emitting device according to the prior art.

2A shows the step of preparing the substrate 10.

The substrate 10 is a substrate on which a light emitting device epi layer is grown, and a gallium nitride (GaN) substrate is best, but a gallium nitride (GaN) substrate is difficult and expensive to manufacture. A hetero substrate such as (Al ₂ O ₃ ) or silicon carbide (SiC) is used, and an undoped gallium nitride (GaN) layer is further formed thereon to form a light emitting device epi layer.

2B illustrates a step of forming the light emitting structure 11 on the substrate 10.

In general, the light emitting structure 11 is formed by sequentially stacking an n-GaN layer, an active layer, and a p-GaN layer.

Here, the n-GaN layer is made by adding an n-type impurity to the gallium nitride layer, serves to supply electrons to the active layer, the active layer serves to generate light with the remaining energy through the recombination of electrons and holes. The p-GaN layer is made by adding a p-type impurity to the gallium nitride layer, and serves to supply holes to the active layer.

FIG. 2C illustrates a step of forming a p-ohmic layer 12 on the light emitting structure 11.

The p-ohmic layer 12 is formed between the semiconductor layer of the light emitting structure 11 and an electrode to be formed later, thereby reducing contact resistance.

FIG. 2D illustrates a step in which the reflective film 13 is formed as a thin layer on the exposed portion of the upper portion of the substrate 10 and on the side surfaces of the light emitting structure 11 and the p-ohmic layer 12.

The reflective film 13 is a method of reflecting light using an aluminum or silver-based reflective electrode, and has an overall insulating property.

In this case, there is a problem of reflectance deterioration due to the interdiffusion phenomenon between the reflective film and the p-omic layer during the heat treatment process.

In addition, when the front seed metal and the first electrode are plated directly on the thin reflective film as described above, the gap between the light emitting structure and the seed metal is narrow, so that a short circuit of the device may occur during the laser lift off (LLO) process. It is also very likely to cause problems such as leakage current.

FIG. 2E illustrates a step in which a seed metal 14 is wrapped around the p-omic layer 12 and outside the reflective layer 13.

The seed metal is a seed layer for forming a first electrode to be formed later.

2F illustrates a step of forming the first electrode 15 on the seed metal 14.

The first electrode 15 is formed of a metal material having good electrical conductivity such as copper (Cu) by a method such as electroplating.

2G illustrates a step of inverting the first electrode 15 downward and removing the substrate 10 to expose the top surface of the light emitting structure 11.

The substrate 10 is removed through a laser lift off (LLO) method.

In addition, the upper surface of the light emitting structure 11 refers to the upper surface of the structure upside down, that is, the surface of the n-GaN layer.

FIG. 2h illustrates a step of forming a vertical light emitting device according to the prior art by forming a second electrode 16 on the exposed upper surface of the light emitting structure 11.

As mentioned above, the upper surface of the light emitting structure 11 corresponds to an n-GaN layer.

In addition, the second electrode 16 may be formed of a transparent electrode material in the form of a pad so as to emit light well.

According to the related art, a problem of lowering the reflectivity of the reflective film during the heat treatment process, a lowering of the insulation and adhesion problems of the thinly formed reflective film during the laser lift off (LLO) process, or a short or There is a big disadvantage that electrical defects such as leakage current are likely to occur.

In order to solve the above problems of the prior art, the present invention forms a high reflective film using only an oxide-based material, and thus, in the conventional reflective film using a metal such as aluminum (Al) or silver (Ag). It is an object of the present invention to provide a highly reflective vertical light emitting device and a method of manufacturing the same by improving the problem of reducing the reflectivity of the reflective film by inter-diffusion with the p-omic layer during the heat treatment process.

In addition, another object of the vertical light emitting device and a method of manufacturing the same according to the present invention, by forming a high reflective film on the outer front surface of the light emitting structure and the p-omic layer (Ohmic-Metal), laser lift off (Laser Lift Off, In the LLO process, it is possible to reduce the electrical characteristics of the device such as short-circuit or leakage current in the device due to metal flakes or melting of the metal material in the conventional reflective film. This provides a high reliability vertical light emitting device.

According to the vertical light emitting device of the present invention, a light emitting structure including an active layer for generating light; An ohmic layer formed on the light emitting structure; A high reflective (HR) film surrounding the remaining region except the lower portion of the light emitting structure and the ohmic layer, and having at least one opening formed therein to expose a portion of the upper portion of the ohmic layer; A seed metal filling the opening and formed on the high reflective film; A first electrode formed on the seed metal; And a second electrode formed under the light emitting structure.

According to the vertical light emitting device manufacturing method of the present invention, forming a light emitting structure including an active layer for generating light on the substrate; Forming an ohmic layer on the light emitting structure; Forming a high reflective (HR) film surrounding the remaining region except the lower portion of the light emitting structure and the ohmic layer; Forming at least one opening in the high reflection film of the upper region of the ohmic layer to expose a portion of the upper portion of the ohmic layer; Filling the openings and forming a seed metal on the high reflective film; Forming a first electrode on top of the seed metal; Removing the substrate and exposing the bottom of the light emitting structure; And forming a second electrode under the exposed light emitting structure.

Hereinafter, a preferred embodiment of a vertical light emitting device according to the present invention with reference to the drawings will be described in detail.

3 is a cross-sectional view for explaining a preferred embodiment of the vertical light emitting device according to the present invention.

As shown in the figure, the vertical light emitting device of the present invention, the light emitting structure 110; p-Ohmic Layer 120; High reflective film 130; Seed metal 140; First electrode 150; The second electrode 160 is configured.

First, the light emitting structure 110 includes an active layer that generates light, specifically, an n-GaN layer, an active layer, and a p-GaN layer are sequentially stacked, and the active layer is also gallium nitride (GaN). It is preferable that it is made of a) series material.

The p-ohmic layer 120 is formed on the light emitting structure 110.

In this case, the p-ohmic layer is preferably made of indium tin oxide (ITO) material.

In addition, the high reflection film 130 having at least one or more openings for exposing a portion of the upper portion of the p-ohmic layer 120 in the remaining regions except the lower portion of the light emitting structure 110 and the p-ohmic layer 120. ) Is formed, the opening is characterized in that it is formed for the electrical connection of the p- ohmic layer 120 and the seed metal (140).

Meanwhile, the high reflection film 130 serves as an insulating layer on the side of the light emitting structure 110 as a passivation layer.

In this case, the high reflection film 130 has a constant height relative to the lowest surface of the light emitting structure, it is preferably formed higher than the p- ohmic layer.

On the other hand, the high reflection film 130 is preferably formed of any one of SiO ₂ or TiO ₂ material.

The seed metal 140 fills at least one or more openings formed in the high reflective film 130 and is formed on the high reflective film.

The seed metal 140 is a seed layer for forming the first electrode 150 and is a layer for plating or depositing the first electrode 150 well.

Subsequently, the first electrode 150 is formed on the upper front surface of the seed metal 140. The first electrode 150 is made of a metal having good electrical conductivity such as copper (Cu). It is preferable to form through a plating method such as electroplating.

Meanwhile, a second electrode 160 is formed below the light emitting structure 110, and the second electrode 160 is transparent in the form of a pad in order to emit light through the bottom of the light emitting structure 110. It is preferable to form with electrode material.

4A to 4I are cross-sectional views for describing a preferred embodiment of the manufacturing method of the vertical light emitting device according to the present invention.

4A illustrates a step of preparing the substrate 100.

The substrate 100 is a substrate on which a light emitting device epi layer is grown, and a gallium nitride (GaN) substrate is best, but a gallium nitride (GaN) substrate is difficult and expensive to manufacture, and generally, sapphire It is preferable to use a different substrate such as (Al ₂ O ₃ ) or silicon carbide (SiC), and further form an undoped gallium nitride (GaN) layer thereon to form a light emitting device epi layer.

4B illustrates a step of forming the light emitting structure 110 including an active layer for generating light on the substrate 100.

The light emitting structure 110 is formed by sequentially stacking an n-GaN layer, an active layer, and a p-GaN layer. In this case, the active layer is preferably made of a gallium nitride (GaN) -based material.

Here, the n-GaN layer is made by adding an n-type impurity to the gallium nitride layer, serves to supply electrons to the active layer, the active layer generates light with the remaining energy through the recombination of electrons and holes The p-GaN layer is formed by adding a p-type impurity to the gallium nitride layer, and serves to supply holes to the active layer.

4C illustrates a step of forming a p-ohmic layer 120 on the light emitting structure 110.

The p-ohmic layer 120 is formed between the semiconductor layer of the light emitting structure 110 and an electrode to be formed later to reduce contact resistance between the semiconductor material and the metal material and to provide a current to the front surface. It spreads evenly.

On the other hand, the p-ohmic layer (Ohmic Layer) is preferably formed of indium tin oxide (ITO) material.

FIG. 4D illustrates a step of forming the high reflective film 130 surrounding the remaining region except the lower portion of the light emitting structure 110 and the p-omic layer 120.

In this case, the high reflection film 130 is formed at a constant height relative to the lowest surface of the light emitting structure, it is preferably formed higher than the p- ohmic layer.

In addition, the high reflection film 130 is preferably an oxide-based material, and is preferably formed of any one of SiO ₂ or TiO ₂ .

As such, when the high reflective film made of an oxide-based material is formed to be thick, the hardness is strong, and thus, the p-omic layer material is diffused into the reflective film during the heat treatment process, thereby preventing the problem of deterioration of the reflectivity. Thereafter, even during laser lift off (LLO) process, problems such as device short-circuit or leakage current due to metal flakes or melting of the conventional reflective film may be eliminated. I can solve it.

On the other hand, a thick oxide-type high reflection film can be expected to have the same reflection effect as that of a reflective metal made of a metal-based material such as aluminum (Al) or silver (Ag). Since the raw p-omic layer material is not diffused, the reflectivity is improved rather than the conventional one.

4E illustrates a step of forming at least one opening in the high reflective film 130 in the upper region of the p-ohmic layer 120 to expose a portion of the upper portion of the p-ohmic layer 120.

As such, the reason for forming the opening in the high reflection film 130 is to electrically connect the p-omic layer 120 and the seed metal formed thereafter.

In this case, the opening is preferably formed by etching the high reflection film through a dry etching method.

Here, the opening formed in the high reflection film 130 is preferably formed in a ring shape, as shown in the drawing (see the plan view of FIG. 6).

4F illustrates filling the at least one opening formed in the high reflection film 130 and forming a seed metal 140 on the high reflection film 130.

The seed metal 140 is a seed layer for forming a first electrode to be formed later.

4G illustrates a step of forming the first electrode 150 on the seed metal 140.

The first electrode 150 may be formed of a metal material having good electrical conductivity such as copper (Cu) by a method such as electroplating.

4H illustrates the step of inverting the first electrode 150 downward and removing the substrate 100 to expose the top surface of the light emitting structure 110.

The substrate 100 may be removed through a laser lift off (LLO) method.

In addition, the upper surface of the light emitting structure 110 refers to the upper surface of the structure upside down, and refers to the n-GaN layer.

4I illustrates a step of forming a vertical light emitting device according to the present invention by forming a second electrode 160 on the exposed upper surface of the light emitting structure 110.

The second electrode 160 is preferably formed of a transparent electrode material in the form of a pad so as to emit light well.

In summary, the vertical light emitting device of the present invention is a light emitting device in which the light emitting structure and the seed metal are separated through a thin reflective film made of a metal-based material such as aluminum (Al) or silver (Ag). Unlike, the light emitting structure portion and the seed metal are separated by a thick oxide-type high reflection film, and then, during the laser lift off process, metal flakes or There is an advantage that there is no need to worry about the generation of electrical defects such as device short-circuit or leakage current due to melting or the like.

On the other hand, in the vertical light emitting device of the present invention, the thickness of the first electrode can be made thinner than before due to the strong oxide-type high reflection film, and thus, a plurality of device manufacturing processes on the wafer In the device separation process, there is an advantage that a laser scribing process, which was conventionally impossible due to the thick metal thickness of the first electrode, may also be applied.

5 is a cross-sectional view schematically illustrating a structure of the light emitting structure formed in FIG. 4B.

The light emitting structure 110 is formed by sequentially stacking an n-GaN layer 110a, an active layer 110b, and a p-GaN layer 110c. In this case, the active layer 110b is also a gallium nitride (GaN) -based material. It is preferable that it consists of.

Here, the n-GaN layer 110a is made by adding n-type impurities to the gallium nitride layer, and serves to supply electrons to the active layer 110b, and the active layer 110b recombines electrons and holes. Through the remaining energy to generate light, the p-GaN layer (110c) is made by adding a p-type impurity to the gallium nitride layer, and serves to supply holes to the active layer (110b).

6 shows the top view of FIG. 4E.

As shown in the figure, as a preferred embodiment of the vertical light emitting device of the present invention, it shows a state in which a ring-shaped opening is formed in the region of the high reflective film 130 on the p- ohmic layer 120 .

The reason for forming such an opening and exposing the upper portion of the p-ohmic layer 120 is that the high reflection film itself made of an oxide-based material does not pass current, so that the p-ohmic layer 120 and the electrode In order to be electrically connected, at least one such opening must be formed.

For reference, in the present embodiment, at least one or more openings formed in the high reflection film have been exemplified in the case of being formed in a ring shape, but the shape of the openings can be variously modified.

While the configuration of the invention according to the embodiment of the present invention has been described in detail, the present invention is not necessarily limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention.

According to the vertical light emitting device of the present invention as described above and a method of manufacturing the same, by forming a high reflection film of an oxide-based material, using a metal such as aluminum (Al) or silver (Ag) In the heat treatment process, the reflective film reacts with the p-omic layer and diffuses into the reflective film, thereby realizing a highly reflective vertical light emitting device having a problem of reducing the reflectivity of the reflective film.

In addition, according to the vertical light emitting device of the present invention and a method of manufacturing the same, by forming a high reflective film thick on the outer surface of the light emitting structure and the p-ohmic layer, during the laser lift off (LLO) process In the conventional reflecting film, it prevents dielectric breakdown due to metal flakes or melting of metal materials and electrical deterioration problems such as short-circuit or leakage current in the device. There is an effect that can implement a reliable vertical light emitting device.

In addition, according to the vertical light emitting device of the present invention and a method of manufacturing the same, by forming a high reflective film thicker using an oxide-based material, it is possible to improve the adhesion (adhesion) than conventional.

On the other hand, according to the vertical light emitting device of the present invention and a method of manufacturing the same, when manufacturing a plurality of light emitting devices on a wafer basis, by filling with a high reflective film using an oxide-based material between the adjacent light emitting structure, copper, (Cu) Even if the thickness of the supporting electrode is made thinner than the conventional, it may have a supporting force capable of wafer handling due to the characteristics of the strong oxide, and a device through a laser scribing process. It can be easily separated into units, and therefore, there is an advantage suitable for mass production.

Claims (10)

A light emitting structure comprising an active layer for generating light; An ohmic layer formed on the light emitting structure; A high reflective (HR) film surrounding the remaining regions other than the lower portion of the light emitting structure and the ohmic layer and having at least one opening exposing a portion of the upper portion of the ohmic layer; A seed metal filling the opening and formed on the high reflection film; A first electrode formed on the seed metal; And a second electrode formed under the light emitting structure. The method of claim 1, The light emitting structure, An n-GAN layer doped with n-type impurity, an active layer made of gallium nitride (GaN) -based material, and a p-GaN layer doped with p-type impurity. The method of claim 1, The ohmic layer is Vertical light emitting device, characterized in that consisting of ITO (Indium Tin Oxide) material. The method of claim 1, The high reflection film, Vertical light emitting device, characterized in that consisting of oxide-based material. The method of claim 1, The high reflection film, Vertical type light emitting device, characterized in that SiO ₂ or TiO ₂ . The method of claim 1, The opening is Vertical light emitting device, characterized in that the ring (Ring) shape. Forming a light emitting structure including an active layer for generating light on the substrate; Forming an ohmic layer on the light emitting structure; Forming a high reflective (HR) film surrounding the remaining area except the lower portion of the light emitting structure and the ohmic layer; Forming at least one opening in the high reflection film of the upper portion of the ohmic layer to expose a portion of the upper portion of the ohmic layer; Filling the opening and forming a seed metal on the high reflective film; Forming a first electrode on the seed metal; Removing the substrate and exposing a lower portion of the light emitting structure; And forming a second electrode under the exposed light emitting structure. The method of claim 7, wherein The light emitting structure The n-GAN layer doped with n-type impurity, an active layer made of a gallium nitride (GaN) -based material, and a p-GaN layer doped with p-type impurity are sequentially stacked to form a light emitting device. . The method of claim 7, wherein The opening is Vertical light emitting device manufacturing method characterized in that formed in a ring (Ring) shape. The method of claim 1, The high reflection film, Vertical light emitting device manufacturing method characterized in that the oxide (Oxide) -based material.

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