KR101383358B1

KR101383358B1 - Method of fabricating for vertical light emitting diode

Info

Publication number: KR101383358B1
Application number: KR1020070105622A
Authority: KR
Inventors: 강정모; 최재완; 최정현; 김두현; 김재욱
Original assignee: 엘지이노텍 주식회사; 엘지전자 주식회사
Priority date: 2007-10-19
Filing date: 2007-10-19
Publication date: 2014-04-10
Also published as: KR20090040052A

Abstract

In the vertical light emitting diode manufacturing method according to the present invention, forming a plurality of semiconductor layers on the substrate, forming a groove from the substrate side or from the plurality of semiconductor layers to the interface between the substrate and the plurality of semiconductor layers and the substrate Irradiating a laser from the side to separate the substrate from the plurality of semiconductor layers, wherein at least one groove is formed in a region corresponding to the effective area of irradiation of the laser.

Vertical Light Emitting Diode, Laser Lift Off, Fine Groove

Description

Vertical light emitting diode manufacturing method {METHOD OF FABRICATING FOR VERTICAL LIGHT EMITTING DIODE}

The present invention relates to a vertical light emitting diode manufacturing method.

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. As a lot of attention. In particular, blue and green light emitting devices using gallium nitride (GaN) have been used in various applications such as large-scale color flat panel displays, traffic lights, indoor lighting, high-density light sources, high resolution output systems and optical communication.

The nitride semiconductor layer of such a group III element, in particular, GaN, is difficult to fabricate a homogeneous substrate capable of growing it, and thus, it is difficult to fabricate a homogeneous substrate capable of growing it, such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy; MBE) and other processes. A sapphire substrate having a hexagonal system structure is mainly used as a heterogeneous substrate.

However, since sapphire is an electrically insulator, it restricts the light emitting diode structure and is very stable mechanically and chemically, making it difficult to process such as cutting and shaping. In recent years, a technology for growing a nitride semiconductor layer on a heterogeneous substrate such as sapphire and then separating the heterogeneous substrate to fabricate a vertical-type LED has been researched.

As a method of removing heterogeneous substrates such as sapphire substrates from nitride semiconductor layers, a laser lift-off (LLO) method is generally used. In the laser lift-off process, a semiconductor layer grown on a substrate is placed on a support and irradiated with an excimer laser from the substrate side. At this time, since the energy of the excimer laser is less than the bandgap energy of sapphire and greater than the bandgap energy of gallium nitride, the substrate passes and the energy of the excimer laser is concentrated at the interface between the gallium nitride semiconductor layer and the substrate. The gallium (GaN) phase transition to the gallium (Ga) and nitrogen (N ₂ ) gas, the nitrogen gas is blown away, leaving only the liquid gallium at the interface, the substrate is separated from the gallium nitride semiconductor layer.

In this process, due to the limitation of the size and uniformity of the excimer laser beam, the entire surface of the sapphire substrate cannot be removed at a time. Thus, the entire substrate is removed by irradiating a small size laser beam uniformly on the substrate. However, the rear surface of the gallium nitride semiconductor layer dropped in this process is not uniform, and there is a problem that cracks occur.

Various methods have been proposed to prevent such a phenomenon, but accordingly, there is a problem in that a light emitting diode manufacturing process is considerably complicated technically or the semiconductor layers cannot be uniformly removed over the entire substrate as intended.

The present invention has been made in view of the above, and provides a vertical light emitting diode manufacturing method for minimizing crack or quality damage of a semiconductor layer generated during a laser lift-off (LLO) process. Its purpose is to.

In order to solve the above technical problem, a vertical light emitting diode manufacturing method includes: forming a plurality of semiconductor layers on a substrate; Forming grooves from the substrate side or from the plurality of semiconductor layers to an interface between the substrate and the plurality of semiconductor layers; And separating the substrate from the plurality of semiconductor layers by irradiating a laser from the substrate side, wherein at least one groove is formed in a region corresponding to an effective area of irradiation of the laser. .

According to this, by forming a groove so that the interface between the substrate and the semiconductor layer is partially exposed to the outside, nitrogen gas is discharged through the groove during laser irradiation to separate the substrate, thereby minimizing the impact when the substrate is separated, so that the entire substrate It is possible to uniformly remove and minimize the occurrence of cracks.

According to one embodiment of the present invention, the groove is preferably formed in the center portion of the effective area of the laser irradiation.

In addition, according to another embodiment of the present invention, the groove is preferably formed in the outer portion of the effective area of irradiation of the laser, the groove formed in the outer portion of the effective area of irradiation of the laser is another adjacent laser It is preferable that it is formed to span the outer portion of the irradiation effective area of.

Further, according to another embodiment of the present invention, the groove is preferably formed in the center portion and the outer portion of the effective area of the laser irradiation.

By forming the grooves according to various embodiments as described above, the process for forming the grooves can be minimized, and the deterioration of quality and cracks can be minimized when the sapphire substrate is separated.

According to the present invention, the interface between the sapphire substrate and the semiconductor layer is partially exposed, thereby minimizing the impact when the substrate is separated by laser irradiation to uniformly remove the entire substrate and suppress cracks to maintain the quality of the semiconductor layer. It has an effect.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, etc. of components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

1 and 2 are cross-sectional views illustrating a method of manufacturing a vertical light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1, in order to manufacture a vertical light emitting diode, first, a plurality of semiconductor layers 60 are grown on a substrate 10. As the substrate 10, a heterogeneous substrate such as a sapphire substrate may be used, but is not limited thereto.

The semiconductor layer 60 includes a first semiconductor layer 30, an active layer 40, and a second semiconductor layer 50. The semiconductor layers may be III-N-based gallium nitride compound semiconductor layers, and may be grown by a process such as metal organic chemical vapor deposition (MOCVD) or molecular beam deposition (MBE).

The first semiconductor layer 30 and the second semiconductor layer 50 may represent N-type and P-type, or P-type and N-type. The active layer 40 may be a GaN series single quantum well structure (SQW) or a multi quantum well structure (MQW), or a quantum structure such as a super lattice (SL). Can be. The quantum structure of the active layer 40 may be formed by combining various GaN-based materials, and for example, AlInGaN, InGaN, or the like may be used.

Meanwhile, a buffer layer 20 may be formed before the first semiconductor layer 30 is formed, that is, between the first semiconductor layer 30 and the substrate 10. The buffer layer 20 is adopted to mitigate lattice mismatch between the substrate 10 and the semiconductor layer 60, and may generally be a gallium nitride-based material layer.

After forming the semiconductor layer 60, as shown in Figs. 2 and 3, by forming a groove to the interface (boundary surface) between the substrate 10 and the semiconductor layer 60, a portion of the interface is exposed to the outside You can do that.

FIG. 2 shows that the fine grooves 70 are formed from the substrate 10 side to the interface between the substrate 10 and the first semiconductor layer 30 (or the buffer layer if there is the buffer layer 20).

The groove 70 may be formed by irradiating a laser. Various kinds of lasers may be used as the laser for forming the grooves 70, for example, a Diode Pumped Solid State (DPSS) laser or an excimer laser may be used. Of course, the wavelength and intensity of the laser for forming the groove 70 is not limited to any one and may have various values. When using DPSS laser, it has many advantages such as high power, high efficiency, long life and high reliability compared to conventional high output energy CO ₂ laser, Nd; YAG laser pumped by flash lamp, excimer laser, etc. .

Meanwhile, unlike FIG. 2, FIG. 3 shows the fine groove 70 ′ from the side of the semiconductor layer 60 to the interface between the substrate 10 and the first semiconductor layer 30 (or the buffer layer when the buffer layer 20 is present). It shows what was formed.

The groove 70 'formed in the semiconductor layer 60 may be formed using an etching process. An etching process for forming the groove 70 'may be performed by a dry etching or a wet etching method, and is not limited to any particular etching process.

On the other hand, according to the vertical light emitting diode forming method according to an embodiment of the present invention, the micro groove 70 as described with reference to FIG. 2 and the micro groove 70 'as described with reference to FIG. To form a fine groove 70 'through an etching process from the semiconductor layer 60 to the interface of the substrate 10, while the microgroove from the substrate 10 to the interface of the substrate 10 and the semiconductor layer 60. 70 can also be formed.

The fine grooves 70 and 70 'formed as described above with reference to FIGS. 2 and 3 are exposed to the outside, and when the laser lift-off process is performed later, the grooves 70 and 70' are formed through the grooves 70 and 70 '. Allow for the release of nitrogen gas or thermal stress from laser irradiation.

On the other hand, at least one groove (70, 70 ') is preferably formed in a region corresponding to the effective area of the excimer laser used in the laser lift-off process. Looking in more detail below.

As described above, the front surface of the substrate cannot be removed at a time due to the limitation of the size and uniformity of the excimer laser beam during the laser lift-off process. Likewise, the entire substrate is removed by irradiating the sapphire substrate 10 partly.

FIG. 5 shows a beam profile of an excimer laser used in a laser lift-off process. As shown in FIG. 5, the excimer laser beam has a central rectangle because the energy density of the excimer laser beam is not uniform depending on the center part and the boundary part. The part A, which is represented by the dotted line (hereinafter referred to as 'irradiation effective area'), actually contributes to the laser lift-off, which is relatively small compared to the wafer, so the laser lift-off process It is made while moving left and right up and down as shown in FIG. The irradiation effective area (A) is not easy to accurately specify the area, but can be represented by rough experimental values and statistics.

Examples of forming at least one fine groove 70 in the region corresponding to the effective area A of the excimer laser may be variously applied, and FIGS. 6 to 8 illustrate representative examples thereof.

FIG. 6 shows a first embodiment in which fine grooves are formed in the substrate according to the present invention, and shows a plan view of the substrate 10 when the fine grooves are formed from the substrate 10 side as shown in FIG.

In the drawing, the area defined by the solid solid line 80 represents the effective area of irradiation of the laser beam, and the arrow represents the irradiation path of the laser during the laser lift-off process.

In the present embodiment, the fine groove 71 may be formed in the center portion of the effective area irradiated by the laser. The central part does not mean a perfect center here, but it should be understood that it is about the center.

FIG. 7 shows a second embodiment of forming fine grooves in the substrate according to the present invention, and shows a plan view of the substrate 10 when the fine grooves are formed from the substrate 10 side as shown in FIG.

As described with reference to FIG. 6, the rectangular solid line 80 region shows the effective area of irradiation of the laser beam, and the arrow shows the irradiation path of the laser during the lift-off process.

In the present exemplary embodiment, the fine groove 72 may be formed at an outer portion of the effective area irradiated by the laser, and may be formed near the vertex of the quadrangle as shown. On the other hand, the fine groove 72 may be formed to cover the outer portion of the effective area irradiated by other adjacent laser beams.

As such, the fine grooves 72 are formed to extend over the outer portion of the laser irradiation effective area adjacent to one laser irradiation effective area, thereby reducing the number of steps for forming the grooves.

FIG. 8 shows a third embodiment of forming the microgrooves in the present invention, and shows a plan view of the substrate when the microgrooves are formed from the substrate 10 side as shown in FIG.

As described with reference to FIGS. 6 and 7, the rectangular solid line 80 region shows the effective area of irradiation of the laser beam, and the arrow shows the irradiation path of the laser during the lift-off process.

In the present embodiment, the fine grooves 71 and 72 may be formed in the center portion and the outer portion of the effective area of irradiation of the laser, respectively.

Theoretically, the more such grooves are formed, the more damage and cracks of the semiconductor layers may be minimized when the substrate 10 is separated by the laser lift-off process. However, since the formation of too many grooves is a burden on the process, it is preferable to form an appropriate number of grooves, as shown in FIGS. 6 to 8, and preferably, as shown in FIG. 8. It is good to form the center and the outer part of the effective area together.

On the other hand, each of the fine grooves may have the same size, but is not limited thereto. In addition, the position, shape and size of the fine grooves may be variously modified, and the present invention is not limited to the specific examples.

6 to 8 illustrate embodiments in which the fine grooves 70 are formed from the substrate 10 side as shown in FIG. 2, but the present invention is not limited thereto and the semiconductor layer 60 as shown in FIG. 3. In the case of forming the fine groove 70 'from the side, it can be applied to the same position, shape and size.

As described above, after the fine grooves are formed in the semiconductor layer 60 or the substrate 10, a conventional laser lift-off process is performed, and FIG. 9 illustrates this.

That is, when the excimer laser is irradiated from the substrate 10 side as shown, the laser passes through the substrate 10 and the substrate 10 and the first semiconductor layer 30 (or the buffer layer 20 are present). Local heat is generated in the substrate 10 and the buffer layer 20.

This heat causes GaN to form gallium (Ga) and nitrogen (N ₂ ) at the interface between the substrate 10 and the first semiconductor layer 30 (or the interface between the substrate 10 and the buffer layer 20 if there is a buffer layer 20). The substrate 10 is separated from the semiconductor layer 60 by heat and pressure generated during decomposition.

At this time, heat, pressure, and nitrogen gas generated during decomposition are released through the grooves 70 and 70 ', resulting in an effect of thermal stress and pressure reduction, and thus the semiconductor layer 60 when the substrate 10 is separated. This will minimize the occurrence of cracks without damaging the system.

Although the preferred embodiments of the present invention have been described, the present invention is not limited to the specific embodiments described above. It will be apparent to those skilled in the art that numerous modifications and variations can be made in the present invention without departing from the spirit or scope of the appended claims. And equivalents should also be considered to be within the scope of the present invention.

3 is a cross-sectional view illustrating a method of manufacturing a vertical light emitting diode according to another embodiment of the present invention.

4 is a view for explaining a laser irradiation method according to the laser lift-off process.

5 is a diagram illustrating a beam profile according to a laser lift off process.

6 to 8 are diagrams showing an example of forming fine grooves according to the vertical light emitting diode manufacturing method according to embodiments of the present invention.

FIG. 9 is a view for explaining an effect of performing a laser lift-off process on a vertical light emitting diode formed according to embodiments of the present invention.

Claims

Forming a plurality of semiconductor layers on the substrate;

Forming a groove from the substrate side to an interface between the substrate and the plurality of semiconductor layers or forming a groove using an etching process from the plurality of semiconductor layers to the interface; And

Irradiating a laser from the substrate side to separate the substrate from the plurality of semiconductor layers;

And at least one groove is formed in an area corresponding to an effective area of irradiation of the laser.

The method according to claim 1,

And the groove is formed at the center of the effective area irradiated by the laser.

The method according to claim 1,

And the groove is formed in an outer portion of the effective area irradiated by the laser.

The method of claim 3,

And the groove formed in the outer portion of the irradiation effective area of the laser is formed so as to span the outer portion of the irradiation effective area of another adjacent laser.

The method according to claim 1,

The groove is a vertical light emitting diode manufacturing method, characterized in that formed in the center and the outer portion of the effective area of the laser irradiation.

6. The method according to any one of claims 1 to 5,

The grooves of the vertical type light emitting diode manufacturing method, characterized in that the same size.

The method according to claim 1,

Forming a groove from the substrate side, the vertical light emitting diode manufacturing method, characterized in that for forming a groove by irradiating a laser.

8. The method of claim 7,

The laser is a manufacturing method of a vertical light emitting diode, characterized in that the DPSS (Diode Pumped Solid State) laser or excimer laser.

delete