KR101055779B1 - Method of fabricating high efficiency light emitting diode - Google Patents

Abstract

PURPOSE: A method for manufacturing a light emitting diode with high efficiency is provided to successively process the separation and the patterning of a first substrate in a laser lift-off apparatus by forming a pattern by arranging a laser mask in a laser lift-off apparatus. CONSTITUTION: Epi layers(26), including a n-type gallium nitride semiconductor layer on a first substrate(10), an active layer(23), and a p-type gallium nitride semiconductor layer, are grown in a first substrate. The surface of the n-type gallium nitride semiconductor layer is exposed by eliminating the first substrate. A laser mask, which has the masking pattern of a laser transmissive unit and a laser blocking unit at the upper surface of the n-type gallium nitride semiconductor layer, is arranged. The pattern corresponding to the masking pattern is formed on the surface of the n-type gallium nitride semiconductor layer by irradiating laser through the laser mask and then a rough surface is formed on the surface of the N-type gallium nitride semiconductor layer.

Description

High efficiency LED manufacturing method {METHOD OF FABRICATING HIGH EFFICIENCY LIGHT EMITTING DIODE}

The present invention relates to a method for manufacturing a light emitting diode, and more particularly, to a method for manufacturing a high efficiency light emitting diode using a laser lift off technique.

In general, nitrides of group III elements, such as gallium nitride (GaN) and aluminum nitride (AlN), have excellent thermal stability and have a direct transition energy band structure. It is attracting much attention as a substance. In particular, blue and green light emitting devices using indium gallium nitride (InGaN) have been used in various applications such as large-scale color flat panel display devices, traffic lights, indoor lighting, high density light sources, high resolution output systems, and optical communications.

Such a nitride semiconductor layer of Group III elements is difficult to fabricate homogeneous substrates capable of growing them, and therefore, such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE), etc., on heterogeneous substrates having a similar crystal structure. Is grown through the process. As a hetero substrate, a sapphire substrate having a hexagonal structure is mainly used. However, sapphire is an electrically insulator, thus limiting the light emitting diode structure. Accordingly, recently, a technique for manufacturing a light emitting diode having a vertical structure by growing an epitaxial layer such as a nitride semiconductor layer on a hetero substrate such as sapphire and separating the hetero substrate is studied.

A laser lift-off method is mainly used as a method of separating the hetero substrate. The laser lift-off method grows epitaxial layers on a heterogeneous substrate, such as a sapphire substrate, bonds a second substrate on the epitaxial layers, and then irradiates a laser beam through the sapphire substrate to separate the heterogeneous substrate from the epitaxial layer. It is a technique to do.

On the other hand, U.S. Patent No. 7,704,763 (Patent Document 1) discloses light emission in which a sapphire substrate is separated and exposed to form an rough surface on an N-type semiconductor layer surface having an exposed epi layer, for example, an N-face surface. A diode is disclosed. According to US Patent No. 7,704,763, the surface of the N-type semiconductor layer from which the sapphire substrate has been removed has an N-plane surface, and the surface may be etched by using photochemical etching techniques to form a roughened surface.

In addition, US Patent Publication No. US2008 / 0142814A1 (Patent Document 2) discloses a technique of forming a rough surface on the N-type semiconductor surface to improve the light extraction efficiency. In particular, US Patent Publication US2008 / 0142814A1 forms an etching mask, such as a mask of SiO 2 or photoresist, on an N-type semiconductor layer, and uses the same to etch the surface of the N-type semiconductor layer, and then the surface of the N-type semiconductor layer. The technique of forming the roughened surface is disclosed (refer FIG. 10 of patent document 2). By forming an etching pattern corresponding to the mask pattern on the surface of the N-type semiconductor layer and forming a rough surface on the etching pattern, the light emission area may be increased, thereby improving light extraction efficiency.

However, according to US 2008 / 0142814A1, in order to etch the N-type semiconductor layer, a mask pattern is formed on the surface of the N-type semiconductor layer. The mask pattern is generally formed using photo and etching processes and must also be formed on every wafer. Therefore, the process of forming an etching pattern on the surface of the N-type semiconductor layer is complicated.

Patent Document 1: US Patent No. 7,704,763 Patent Document 2: US Patent Publication No. US2008 / 0142814A1

An object of the present invention is to provide a light emitting diode manufacturing method of a new technology that can improve the light extraction efficiency by increasing the light emission area.

Another object of the present invention is to provide a method for manufacturing a diode that can simplify the manufacturing process for increasing the light emitting area.

Another object of the present invention is to provide a light emitting diode manufacturing method capable of patterning an N-type semiconductor layer using a laser lift-off device.

The present invention provides a surface roughened on the surface of the patterned N-type gallium nitride-based semiconductor layer using a laser patterning the surface of the N-type gallium nitride-based semiconductor layer, in particular, the surface of the N-type gallium nitride-based semiconductor layer having an N-plane surface It characterized in that to form. The laser is irradiated onto the surface of the N-type gallium nitride-based semiconductor layer through a laser mask disposed on the surface of the N-type gallium nitride-based semiconductor layer, so that the pattern corresponding to the masking pattern of the laser mask is N-type gallium nitride-based It is formed on the surface of the semiconductor layer.

Because of the use of a laser mask, there is no need to form a new mask for every wafer, and there is no need to form a mask pattern on the wafer using photo and etching techniques, thus increasing the light emitting area with a simple manufacturing process. have.

Specifically, the light emitting diode manufacturing method according to an aspect of the present invention, growing an epitaxial layer including an n-type gallium nitride-based semiconductor layer, an active layer and a p-type gallium nitride-based semiconductor layer on the first substrate, The substrate is removed to expose the surface of the n-type gallium nitride-based semiconductor layer, a laser mask having a masking pattern of a laser transmitting part and a laser blocking part is disposed on the n-type gallium nitride-based semiconductor layer, and the laser mask is disposed. Irradiating a laser beam to form a pattern corresponding to the masking pattern on the surface of the n-type gallium nitride based semiconductor layer, and forming a roughened surface on the surface of the n-type gallium nitride based semiconductor layer having the pattern. .

Removing the first substrate may be performed using a laser lift off technique, and irradiating the laser may be performed using a laser apparatus used in the laser lift off technique.

The masking pattern is not particularly limited, but may be, for example, a mesh pattern. Accordingly, a regularly arranged pattern may be formed on the surface of the N-type gallium nitride based semiconductor layer. Further, the laser mask is not particularly limited as long as the laser mask can form a laser blocking portion capable of blocking the laser and a laser transmitting portion transmitting the laser. Preferably, the laser blocking portion may be formed of a metal material. For example, by forming the metal material into a mesh shape, the light blocking portion is formed by the metal material, and the light transmitting portion can be formed between the metal materials.

On the other hand, forming the roughened surface may be performed using a photoelectric chemical (PEC) etching technique.

Also, before removing the first substrate, a second substrate may be attached to the epi layers. The second substrate may be a conductive, insulating or semiconductor substrate.

According to another aspect of the present invention, there is provided a light emitting diode manufacturing method comprising: preparing a gallium nitride-based semiconductor layer having an N-plane surface, and disposing a laser mask having a masking pattern of a light transmitting portion and a light blocking portion on the N-plane surface; Irradiating a laser through the laser mask to form a pattern corresponding to the masking pattern on the N-plane surface, and to form a rough surface on the surface of the gallium nitride based semiconductor layer on which the pattern is formed by using photochemical etching. It involves doing.

In addition, the masking pattern may be a mesh-shaped pattern, and the laser is an ultraviolet laser absorbed by the gallium nitride semiconductor layer.

According to the present invention, since the pattern is formed on the surface of the gallium nitride based semiconductor layer using a laser mask, the light emitting diode manufacturing process can be simplified. Furthermore, since the laser mask may be disposed on the laser lift-off device to form the pattern, the separation and patterning process of the first substrate may be continuously performed in the laser lift-off device.

1 to 7 are schematic cross-sectional views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.
8 is a schematic view for explaining a laser irradiation apparatus for use in the light emitting diode manufacturing method according to an embodiment of the present invention.
9 is a plan view illustrating a laser mask according to an embodiment of the present invention.
10 is a cross-sectional view for describing a light emitting diode manufacturing method according to still another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples to ensure that the spirit of the present invention to those skilled in the art will fully convey. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 to 7 are schematic cross-sectional views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1, epitaxial layers 26 including a first conductive compound semiconductor layer 21, an active layer 23, and a second conductive compound semiconductor layer 25 may be formed on a first substrate 10. Is formed. The first substrate 10 may be a growth substrate on which the epi layers 26 are grown, such as a sapphire substrate or a SiC substrate. The first substrate 10 is not particularly limited and may have a C-plane growth surface.

The epi layers 26 may be gallium nitride-based compound semiconductor layers, and may be grown on the first substrate 10 using organic chemical vapor deposition or molecular beam deposition. Although not shown, the epi layers 26 may include a buffer layer to mitigate lattice mismatch between the first substrate 10 and the epi layer 26 grown thereon. In addition, the active layer 23 may be a single quantum well structure or a multi quantum well structure. Here, the first conductivity type and the second conductivity type are n type and p type, respectively.

When the first substrate 10 has a C-plane growth surface, the epi layers 26 have an N-side on the first substrate 10 side and a Ga-plane on the top. The epi layers 26 are grown in a vacuum chamber, and after the growth is completed, the first substrate 10 on which the epi layers 26 are grown is removed from the chamber for the next process.

Referring to FIG. 2, a second substrate 30 may be bonded on the uppermost layer of the epitaxial layers 26, for example, the second conductive compound semiconductor layer 25. The second substrate 30 may be variously selected according to its use, such as thermal conduction, electrical conduction, and the like. For example, the second substrate 30 may be an insulating substrate such as sapphire, a semiconductor substrate such as silicon, or a metal substrate.

The second substrate 30 may be bonded to the epi layers 26 using eutectic bonding of the bonding metal 31. The bonding metal 31 may be AuSn, and AuSn may have a melting point of about 330 ° C. Bonding metals of higher melting point than AuSn may also be used. These bonding metals 31 are formed on the epilayers 26 side and the second substrate 30 side, respectively, and are then eutectic bonded by heating to a first temperature higher than room temperature, such as a temperature of about 300 ° C. The second substrate 30 is attached to the epi layers 26.

Meanwhile, before forming the bonding metal 31, the reflective layer 27 and the diffusion barrier layer 29 may be formed on the epi layers 26. The reflective layer 27 reflects the light generated in the active layer 23 toward the second substrate 30 to improve the light output. The reflective layer 27 may also be in ohmic contact with the second conductivity-type semiconductor layer 25 and may be formed of Al, Ag, Ni, Ph, Pd, Pt, Ru, or an alloy thereof. On the other hand, the diffusion barrier layer 29 prevents the bonding metal 31 from diffusing into the reflective layer 27 to lower the reflectance of the reflective layer 27.

Referring to FIG. 3, after bonding of the second substrate 30, the first substrate 10 is disposed in the laser lift-off apparatus to separate the first substrate 10. Subsequently, the first substrate 10 is removed from the epi layers 26 by irradiating the laser L1 through the first substrate 10. This removal of the first substrate 10 is well known as a laser lift off technique.

Referring to FIG. 4, after the first substrate 10 is separated, the laser mask 40 is disposed on the exposed first conductive semiconductor layer 21. The laser mask 40 has a masking pattern composed of a laser cutoff portion 40a and a laser transmitting portion 40b. The laser is blocked by the laser cutoff portion 40a, and the laser L2 is irradiated onto the surface of the first conductivity type semiconductor layer 21 through the laser transmitting portion 40b. Metal components of the first conductive semiconductor layer 21, for example, Al, Ga and / or In, and nitrogen (N) are decomposed by laser irradiation to correspond to the masking pattern on the surface of the first conductive semiconductor layer 21. Patterns 50a and 50b are formed.

The laser can be irradiated using a laser device used in a laser lift-off technique, and absorbed in a gallium nitride based semiconductor layer. The laser may also be an ultraviolet laser of the same wavelength as the laser used in the laser lift off technique.

Referring to FIG. 5, patterns 50a and 50b corresponding to masking patterns 40a and 40b are formed on the surface of the first conductivity-type semiconductor layer 21. After the patterns 50a and 50b corresponding to the masking patterns are formed by laser irradiation, the surface of the first conductivity-type semiconductor layer 21 is cleaned with HCl to remove, for example, Ga residue remaining on the surface. Can be.

Referring to FIG. 6, after the patterns 50a and 50b are formed, a roughened surface R is formed on the surface of the first conductive semiconductor layer 21. Roughened surface R may be formed using, for example, photochemical chemistry (PEC) etching techniques. When the surface of the first conductive semiconductor layer 21 has an N-plane, pyramidal protrusions are formed on the surface of the first conductive semiconductor layer 21 by photochemical etching. The photochemical etching technique may be performed by dipping epilayers in a KOH solution and irradiating the N-plane surface of the gallium nitride based semiconductor layer using an Xe / Hg lamp. A photoelectric chemical technique is disclosed in US Patent No. 7,704,763 or US Patent Publication No. US2008 / 0142814A1, and a detailed description thereof will be omitted.

Referring to FIG. 7, an electrode pad 33 may be formed on the first conductive semiconductor layer 21, and an electrode pad 35 may be formed on the second substrate 30. Subsequently, the epitaxial layers 26 including the second substrate 30 are separated into individual light emitting diodes, thereby completing a vertical light emitting diode.

In the present embodiment, the second substrate 30 is described as being bonded to the epi layers 26 using the bonding metal 31, but the second substrate 30 is epitaxially using other various techniques. May be attached to layers 26. For example, the second substrate 30 may be attached to the epi layers using a plating technique.

In addition, in the present exemplary embodiment, the electrode pads 33 and 35 are formed on the upper surface of the first conductive semiconductor layer 21 and the lower surface of the second substrate 30, respectively, but are not limited thereto. For example, when the second substrate 30 is an insulating substrate, the electrode pad 35 may be formed on the upper surface of the second substrate 30. In addition, when the second substrate 30 is a metal substrate, the electrode pad 35 may be omitted. In addition, the electrode pad 33 may be formed on the second substrate 30 away from the epi layers. In this case, the electrode pad 33 may be connected to the top surface of the first conductivity type semiconductor layer 21 through wiring.

8 is a schematic diagram illustrating a laser device that may be used in a method of manufacturing a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 8, the laser device includes a laser oscillator 100 for oscillating a laser beam, a mirror 110 for changing a direction of the laser beam, an optical lens 120 for focusing a laser beam, and a laser beam. It has the stage 200 for supporting the workpiece | work object to be investigated, ie, the wafer 300. On the other hand, the apparatus may have a housing 400 including the path of the laser beam therein to maintain the path of the laser beam in a vacuum state. Furthermore, the laser device comprises a laser mask 40 disposed on the path of the laser beam.

The laser oscillator 100 may be a KrF or ArF excimer laser. The beam emitted from the laser oscillator 100 is reflected by the mirror 110 to change its direction. A number of such mirrors 110 may be installed to change the direction of the laser beam. The optical lens 120 is positioned above the stage 200 and focuses a laser beam incident on the wafer 300.

The stage 200 may move in the x direction and / or y direction by a moving means (not shown), and thus the wafer 300 placed thereon may move.

Meanwhile, a laser mask 40 is disposed between the wafer 300 and the optical lens 120. As shown in FIG. 9, the laser mask 40 has a masking pattern in which the laser blocking part 40a and the laser transmitting part 40b are regularly arranged, and the masking pattern may be, for example, a mesh-shaped pattern. For example, the laser blocking part 40a may be formed of a metal material, and the laser transmitting part 40b may be an empty space between the metal materials. Alternatively, the laser cutout 40a of the metal material may be formed on the quartz substrate.

The wafer 300 includes a second substrate 30 and epitaxial layers 26 positioned on the second substrate 30, and the laser L2 passes through the laser mask 40 to form the first conductive semiconductor. The layer 21 is irradiated. The first conductive semiconductor layer 21 is etched by the laser L2 irradiation, and thus a pattern corresponding to the masking pattern of the laser mask 40 is formed on the surface of the first conductive semiconductor layer 21.

In the present exemplary embodiment, the laser mask 40 may be disposed on the wafer 300 after the laser lift-off process is performed using the laser device. That is, the laser device may be a laser lift-off device for removing the first substrate 20 from the epitaxial layers 26. After the first substrate 20 is removed, the laser mask 40 may be removed from the wafer ( 300) may include an actuator (not shown) for positioning upwards. Therefore, laser lift off and pattern formation can be performed continuously using the same laser apparatus.

10 is a cross-sectional view for describing a light emitting diode manufacturing method according to still another embodiment of the present invention.

Referring to FIG. 10, the light emitting diode manufacturing method according to the present embodiment is generally similar to the light emitting diode manufacturing method described with reference to FIGS. 1 to 7, but the electrode pad 33 is formed of the first conductive semiconductor layer 21. There is a difference between what is formed on a relatively flat surface.

That is, when the patterns 50a and 50b are formed by the irradiation of the laser L2, the region where the electrode pads 33 are to be formed is blocked by the laser L2 to maintain a flat surface. After that, an electrode pad 33 is first formed on the first conductive semiconductor layer 21, and then a roughened surface R is formed by using a photochemical etching technique.

Although some embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various changes and modifications may be made by those skilled in the art without departing from the technical spirit of the present invention. Such modifications and variations are included in the scope of the present invention as defined in the following claims.

Claims (10)

Growing epitaxial layers including an n-type gallium nitride-based semiconductor layer, an active layer and a p-type gallium nitride-based semiconductor layer on the first substrate,
Removing the first substrate to expose a surface of the n-type gallium nitride based semiconductor layer,
A laser mask having a masking pattern of a laser transmitting part and a laser blocking part is disposed on an upper surface of the n-type gallium nitride based semiconductor layer.
Irradiating a laser through the laser mask to form a pattern corresponding to the masking pattern on a surface of the n-type gallium nitride based semiconductor layer,
A light emitting diode manufacturing method comprising forming a roughened surface on the surface of the n-type gallium nitride based semiconductor layer having the pattern. The method according to claim 1,
Removing the first substrate is performed using a laser lift off technique. The method according to claim 2,
Irradiating the laser is performed using a laser device used in the laser lift-off technique. The method according to claim 1,
The masking pattern is a light emitting diode manufacturing method, characterized in that the pattern of the mesh shape. The method according to claim 1,
The laser mask is a light emitting diode manufacturing method formed of a metal material. The method according to claim 1,
Forming the rough surface is a light emitting diode manufacturing method using a photochemical etching technique. The method according to claim 1,
Attaching a second substrate to the epi layers before removing the first substrate. Preparing a gallium nitride based semiconductor layer having an N-plane surface,
Placing a laser mask having a masking pattern of the light transmitting portion and the light blocking portion on the surface of the N-plane,
Irradiating a laser through the laser mask to form a pattern corresponding to the masking pattern on the N-plane surface;
A method of manufacturing a light emitting diode comprising forming a rough surface on the surface of the gallium nitride based semiconductor layer on which the pattern is formed by using photochemical etching. The method according to claim 8,
The masking pattern is a light emitting diode manufacturing method, characterized in that the pattern of the mesh shape. The method according to claim 8,
The laser is a light emitting diode manufacturing method of the ultraviolet laser absorbed by the gallium nitride-based semiconductor layer.

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