KR101018244B1 - Method of manufacturing nitride-based semiconductor light emitting device - Google Patents

Method of manufacturing nitride-based semiconductor light emitting device Download PDF

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KR101018244B1
KR101018244B1 KR1020080109584A KR20080109584A KR101018244B1 KR 101018244 B1 KR101018244 B1 KR 101018244B1 KR 1020080109584 A KR1020080109584 A KR 1020080109584A KR 20080109584 A KR20080109584 A KR 20080109584A KR 101018244 B1 KR101018244 B1 KR 101018244B1
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light emitting
layer
sacrificial layer
conductive
emitting structure
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KR1020080109584A
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Korean (ko)
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KR20100050348A (en
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김규상
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삼성엘이디 주식회사
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Abstract

The present invention relates to a method for manufacturing a nitride-based semiconductor light emitting device, comprising: forming a sacrificial layer on a growth substrate; Forming a light emitting structure by sequentially growing a first conductive nitride layer, an active layer, and a second conductive nitride layer on the sacrificial layer; Removing the light emitting structure and the sacrificial layer so as to expose the bonding interface between the light emitting structure and the sacrificial layer and separating the light emitting structure and the sacrificial layer into a desired size of a final light emitting device; Oxidizing the sacrificial layer in a process of bonding a conductive substrate on the second conductive nitride layer; Etching the oxidized sacrificial layer to separate the growth substrate from the separated light emitting structure; And forming a first conductive electrode on the surface of the separated light emitting structure from which the growth substrate is removed, thereby reducing crystal damage of the nitride layer and improving yield of the light emitting device.

Laser lift-off, wet etching, vertical nitride semiconductor light emitting device

Description

Method of manufacturing nitride-based semiconductor light emitting device

The present invention relates to a method of manufacturing a nitride-based light emitting device, and more particularly, to reduce the crystal damage of the nitride layer due to the thermal shock applied during the laser lift-off (LLO) process and to improve the yield of the light emitting device. A method of manufacturing a nitride-based light emitting device having a vertical structure that can be improved.

Until now, LED (Light Emitting Diode) light emitting devices have grown a semiconductor material on a sapphire substrate and separated the sapphire substrate from the growth layer. Representative substrate separation methods include laser lift-off (LLO) and chemical lift-off (CLO).

Conventionally, a method of manufacturing a nitride-based semiconductor light emitting device having a vertical structure by using the LLO method will be described first, after manufacturing a nitride-based light emitting structure grown on the sapphire substrate, and then p-type of the growth layer of the nitride-based light emitting structure The nitride semiconductor layer is bonded to a conductive substrate such as metal. Next, the sacrificial layer between the sapphire substrate and the growth layer is irradiated with a laser beam to apply heat, thereby peeling off the n-type nitride semiconductor layer from the sapphire substrate. Then, an n-type electrode was formed on the n-type nitride semiconductor layer to form a light emitting device having a vertical current structure.

However, this LLO method has a problem that it is difficult to avoid the thermal shock applied to the active layer of the growth layer using a high power laser.

That is, the GaN single crystal constituting the sapphire substrate and the light emitting structure has a large lattice mismatch, and even when a GaN / AlN buffer layer / sacrificial layer is formed between the sapphire substrate and the light emitting structure, it is smaller than the lattice mismatch between the sapphire substrate and the GaN single crystal, but it is a few%. Lattice mismatch occurs.

Therefore, even if the nitride light emitting structure is separated into element units, thermal stress is generated as heat generated in the process of irradiating a laser beam to the sapphire substrate laterally along the sapphire substrate causes damage to the nitride crystal.

In order to overcome this problem, the proposed CLO method is still in the development stage, and thus it is difficult to be stably applied to device fabrication.

The present invention has been made to solve the above problems, and an object thereof is to provide a method of manufacturing a nitride-based semiconductor light emitting device having a vertical structure which can improve the reliability of the light emitting device by stably separating the sapphire substrate and the nitride light emitting structure. .

A method of manufacturing a nitride-based semiconductor light emitting device according to an embodiment of the present invention, forming a sacrificial layer on a growth substrate; Forming a light emitting structure by sequentially growing a first conductive nitride layer, an active layer, and a second conductive nitride layer on the sacrificial layer; Removing the light emitting structure and the sacrificial layer so as to expose the bonding interface between the light emitting structure and the sacrificial layer and separating the light emitting structure and the sacrificial layer into a desired size of a final light emitting device; Oxidizing the sacrificial layer in a process of bonding a conductive substrate on the second conductive nitride layer; Etching the oxidized sacrificial layer to separate the growth substrate from the separated light emitting structure; And forming a first conductive electrode on a surface of the separated light emitting structure from which the growth substrate is removed.

In this case, the sacrificial layer is preferably AlN or Al x Ga (1-x) N, the oxidized sacrificial layer is an oxide containing Al.

In addition, the growth substrate is a non-conductive substrate, may be a sapphire substrate or a GaN substrate, the conductive substrate may be made of a material selected from the group consisting of Si, Al, Ge, SiC and GaAs.

In addition, the first conductive nitride layer and the second conductive nitride layer are Al x In y Ga (1-xy) N (0≤x≤1, 0≤y≤1, 0≤x + y≤1). It is preferable.

The forming of the light emitting structure may further include forming a highly reflective ohmic contact layer on the second conductive nitride layer, wherein the light emitting structure and the sacrificial layer are exposed to expose the bonding interface. Separating the structure and the sacrificial layer to the desired size of the final light emitting device may be performed by mesa etching.

In addition, the step of oxidizing the sacrificial layer in the process of bonding the conductive substrate on the second conductive nitride layer, it is preferably carried out by wet heat-compression.

In addition, the step of separating the growth substrate from the separated light emitting structure by etching the oxidized sacrificial layer, selective using any one of HF, H 2 NO 3 , KOH and buffered oxide etchant (buffered oxide etchant) It is preferably carried out by wet etching.

The method may further include forming a second conductive electrode on the other surface of the conductive substrate facing the one surface to which the separated light emitting structure is bonded, and cutting the conductive substrate according to the separated light emitting structure. It may further include.

According to the present invention, it is possible to prevent performance degradation and leakage of the light emitting device due to thermal shock applied when the sapphire substrate is separated by the LLO method.

In addition, according to the present invention, by simultaneously proceeding the oxidation process of the sacrificial layer in the bonding process of the conductive substrate it is possible to simplify the process process can reduce the manufacturing cost of the light emitting device.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art. In addition, it should be considered that elements of the drawings attached to the present specification may be enlarged or reduced for convenience of description.

1A to 1E are side cross-sectional views of respective processes for explaining a method of manufacturing a nitride-based semiconductor light emitting device according to one preferred embodiment of the present invention. In the present invention, a sapphire substrate is applied as a growth substrate to be described.

As shown in FIG. 1A, the sacrificial layer 130 is formed on the sapphire substrate 110. Here, the sacrificial layer 130 serves as a buffer layer to mitigate lattice mismatch between the sapphire substrate 110 and the nitride layer to prevent the growth of defects in the nitride layer, and thereafter, a separation layer for separating the sapphire substrate 110. Plays a role. The sacrificial layer 130 is a low temperature nucleus growth layer made of AlN or Al x Ga (1-x) N having a thickness of several tens of nm, and the thickness of the sacrificial layer 130 has a large surface area to facilitate oxidation. In order to increase the thickness, the thickness is better. In addition, the sacrificial layer 130 is oxidized at a high temperature to form an oxide film, and the oxide film has excellent wet etching properties.

In addition to the sapphire substrate 110, a GaN substrate may be used as a growth substrate that may be employed in the present invention.

Subsequently, as shown in FIG. 1B, the light emitting structure 150 made of nitride single crystal is formed on the sacrificial layer 130. The light emitting structure 150 includes a first conductive nitride layer 151, an active layer 153, and a second conductive nitride layer 155.

The first conductive nitride layer 151 and the second conductive nitride layer 155 have Al x In y Ga (1-xy) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) A nitride semiconductor material having a compositional formula may be formed. Representative nitride semiconductor materials include GaN, AlGaN, GaInN, and the like. The first conductive nitride layer 151 and the second conductive nitride layer 155 may be formed by depositing a nitride semiconductor material with a metal organic chemical vapor deposition (MOCVD) method and a molecular beam epitaxy (MBE) method. Or by growing on a sapphire substrate using a known deposition process such as Hybrid Vapor Phase Epitaxy (HVPE).

The active layer 153 is a layer for emitting light and is composed of a nitride layer such as GaN or InGaN having a single or multiple quantum well structure. The active layer 153 is formed using a well-known deposition process such as organometallic vapor deposition, molecular beam growth, or hybrid vapor deposition such as the first conductive nitride layer 151 and the second conductive nitride layer 155. Can be.

Next, as shown in FIG. 1C, the sacrificial layer 130 and the light emitting structure 150 are separated into a desired final device size. More specifically, after the etching mask is formed on the second conductive nitride layer 155, the light emitting structure 150 corresponding to the region exposed by the etching mask pattern of the second conductive nitride layer 155 is formed. And by removing the sacrificial layer 130 by mesa etching, the light emitting structures 150 are separated into the size of the final light emitting device. Preferably, the light emitting structure 150 and the sacrificial layer 130 may be removed until the bonding interface between the light emitting structure 150 and the sacrificial layer 130 is exposed. The nitride semiconductor material constituting the light emitting structure can be easily processed to have a desired cross sectional shape by mesa etching. Such mesa etching is a known technique well known in the art.

Subsequently, as illustrated in FIG. 1D, the conductive substrate 170 is bonded to the upper surface of the light emitting structure 150 ′ separated first. The bonding process of the conductive substrate 170 is performed by a wet heat-compression method. Here, the conductive substrate 170 may be a substrate made of a material selected from the group containing Si, Al, Ge, SiC and GaAs.

At this time, the wet heat-compression method for bonding the conductive substrate 170 onto the upper surface of the light emitting structure 150 ', that is, the second conductive nitride layer 155', is performed under high temperature and high humidity conditions, and the conductive under these conditions is conductive. While the substrate 170 is bonded to the second conductive nitride layer 155 ′, the sacrificial layer 130 ′ is oxidized to form the oxide film 130 ″. That is, Al of the sacrificial layer 130 made of AlN or Al x Ga (1-x) N reacts with oxygen at high temperature to form an oxide containing Al, for example, an Al 2 O x oxide film 130 ″. Form. The Al 2 O x oxide layer 130 ″ formed as described above is easily etched in the wet etching solution to separate the sapphire substrate 110 and the light emitting structure 150 ′. In addition, the Al 2 O x oxide layer 130 ″ preferably has a thickness of at least 100 GPa or more, and when the Al 2 O x oxide layer 130 ″ is smaller than this, it is difficult to penetrate the wet etching solution from the side due to strain, so that separation by wet etching is not easy. not.

After the bonding of the conductive substrate 170 is completed, the sapphire substrate 110 is separated from the light emitting structure 150 ′. When the separation process is described in detail, the Al 2 O x oxide layer 130 ″ formed by oxidizing the sacrificial layer 130 ′ in the process of bonding the conductive substrate 170 to the upper surface of the light emitting structure 150 ′ is formed. The sapphire substrate 110 may be separated from the light emitting structure 150 ′ by removing through selective wet etching using HF, H 2 NO 3 , KOH, and buffered oxide etchant.

Here, since the Al 2 O x oxide layer 130 ″ is selectively wet etched by a wet viewing solution, the Al 2 O x oxide layer 130 ″ may be etched from the side surface, and the first conductive nitride layer 151 may be easily provided even without mechanical force or high heat supplied from the outside. Separated from '). Therefore, the separated light emitting structure 151 ′ may be separated without being damaged. By the wet etching process, the sapphire substrate 110 can be easily separated and removed from the light emitting structure 150 ′ formed on the sapphire substrate 110. In this process, crystal defects and The light output of the nitride semiconductor light emitting device manufactured without leaving physical damage can be improved, and high yield can be expected.

In this case, the method may include surface treating the surface of the first conductive nitride layer 151 ′ exposed by the removal of the Al 2 O x oxide layer 130 ″. It is also preferable to completely remove the Al 2 O x oxide film 130 ″ present on the nitride layer 151 ′.

Next, as illustrated in FIG. 1E, a contact layer is formed on the light emitting structure in which the top and bottom of the resultant product of FIG. 1D are inverted. The contact layer forming process may be performed on the upper surface of the first conductive nitride layer 151 ′ of the individual light emitting structure 150 ′ and the lower surface of the conductive substrate 170. In this case, the first conductive electrode 190 formed on the upper surface of the first conductive nitride layer 151 ′ is selectively formed only in a partial region using a mask, and the second conductive electrode 191 is formed of a conductive substrate ( 170 may be formed entirely with respect to the bottom surface.

2 is a side cross-sectional view showing another embodiment of a light emitting structure 150 manufactured according to FIG. 1B.

As shown in FIG. 2, a highly reflective ohmic contact layer 210 is formed on the second conductive nitride layer 155 of the light emitting structure 150 manufactured according to FIG. 1B. The highly reflective ohmic contact layer 210 is suitable for lowering the contact resistance with the second conductive nitride layer 155 having a relatively high energy band gap, and at the same time has a light emitting surface of the first conductive nitride layer 151. The layer for improving the effective luminance toward the lower surface may be made of a metal with high reflectance.

The highly reflective ohmic contact layer 210 includes at least one layer of a material selected from the group consisting of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au Hf, and combinations thereof. It is preferred to be formed into a structure.

As described above, the light emitting structure having the highly reflective ohmic contact layer formed thereon may be subjected to the same processes as those of FIGS. 1C to 1E.

3 is a side cross-sectional view of a nitride based semiconductor light emitting device in which a conductive substrate 170 is separated from a light emitting structure 150 ′ manufactured according to FIGS. 1A through 1E.

As shown in FIG. 3, the nitride-based semiconductor light emitting device 300 having a vertical structure finally manufactured according to an embodiment of the present invention may include a second conductive electrode 191 ′ and a second conductive electrode 191. And a first conductive electrode 190 formed on the top surface of the light emitting structure 150 'and a light emitting structure 150' formed on the top surface of the conductive substrate 170 '. . The light emitting structure 150 'includes a second conductive nitride layer 155', an active layer 153 ', and a first conductive nitride layer 151' sequentially stacked on the top surface of the conductive substrate 170 '. Has a structure.

Accordingly, according to the method of manufacturing the nitride semiconductor light emitting device according to FIGS. 1A to 1E, 2 and 3, AlN or Al x Ga (1-x) N is formed between the sapphire substrate and the first conductive nitride layer. After the sacrificial layer is formed, the sacrificial layer may be separated from the light emitting structure by removing the Al 2 O x oxide film through a selective wet etching process by oxidizing the sacrificial layer with an Al 2 O x oxide film. As a result, damage to the nitride semiconductor crystal due to thermal shock applied during separation of the sapphire substrate through the laser lift-off process can be prevented.

The present invention is not limited to the above-described embodiment and the accompanying drawings, but is intended to be limited by the appended claims, and various forms of substitution, modification, and within the scope not departing from the technical spirit of the present invention described in the claims. It will be apparent to those skilled in the art that changes are possible.

1A to 1E are side cross-sectional views of respective processes for explaining a method of manufacturing a nitride-based semiconductor light emitting device according to an embodiment of the present invention;

2 is a side cross-sectional view showing another embodiment of a light emitting structure manufactured according to FIG. 1B;

3 is a side cross-sectional view of a nitride based semiconductor light emitting device in which a conductive substrate is separated by a light emitting structure manufactured according to FIGS. 1A to 1E.

Claims (12)

Forming a sacrificial layer on the growth substrate; Forming a light emitting structure by sequentially growing a first conductive nitride layer, an active layer, and a second conductive nitride layer on the sacrificial layer; Removing the light emitting structure and the sacrificial layer so as to expose the bonding interface between the light emitting structure and the sacrificial layer and separating the light emitting structure and the sacrificial layer into a desired size of a final light emitting device; Oxidizing the sacrificial layer in a process of bonding a conductive substrate on the second conductive nitride layer; Etching the oxidized sacrificial layer to separate the growth substrate from the separated light emitting structure; And And forming a first conductive electrode on the surface of the separated light emitting structure from which the growth substrate is removed. The method of claim 1, The sacrificial layer is AlN or Al x Ga (1-x) N manufacturing method of the nitride-based semiconductor light emitting device, characterized in that. The method of claim 2, The oxidized sacrificial layer is a method of manufacturing a nitride-based semiconductor light emitting device, characterized in that the oxide containing Al. The method of claim 1, The growth substrate is a non-conductive substrate, a method of manufacturing a nitride-based semiconductor light emitting device, characterized in that the sapphire substrate or GaN substrate. The method of claim 1, The conductive substrate is a method of manufacturing a nitride-based semiconductor light emitting device, characterized in that made of a material selected from the group consisting of Si, Al, Ge, SiC and GaAs. The method of claim 1, The first conductive nitride layer and the second conductive nitride layer are Al x In y Ga (1-xy) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). A method of manufacturing a nitride-based semiconductor light emitting device. The method of claim 1, The forming of the light emitting structure may include forming a highly reflective ohmic contact layer on the second conductive nitride layer. The method of claim 1, Removing the light emitting structure and the sacrificial layer so as to expose the bonding interface between the light emitting structure and the sacrificial layer and separating the light emitting structure and the sacrificial layer into the desired size of the final light emitting device is performed by mesa etching. Manufacturing method. The method of claim 1, And oxidizing the sacrificial layer in the process of bonding the conductive substrate on the second conductive nitride layer, by wet heat-compression. The method of claim 1, The etching of the oxidized sacrificial layer to separate the growth substrate from the separated light emitting structure may include selective wet etching using any one of HF, H 2 NO 3 , KOH, and a buffered oxide etchant. Method of manufacturing a nitride-based semiconductor light emitting device, characterized in that carried out by. The method of claim 1, And forming a second conductive electrode on the other surface of the conductive substrate facing the one surface to which the separated light emitting structure is bonded. The method of claim 1, And cutting the conductive substrate according to the separated light emitting structure.
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Citations (4)

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Publication number Priority date Publication date Assignee Title
KR100649763B1 (en) * 2005-12-09 2006-11-27 삼성전기주식회사 A method of producing vertical nitride light emitting devices
KR20060131324A (en) * 2005-06-16 2006-12-20 엘지전자 주식회사 Manufacturing process of light emitting diode using aluminium buffer layer
KR100867518B1 (en) 2006-09-06 2008-11-07 삼성전기주식회사 Method of manufacturing nitride-based semiconductor light emitting device
KR100874653B1 (en) 2007-07-30 2008-12-17 고려대학교 산학협력단 Gallium nitride light emitting diode and method for manufacturing the same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20060131324A (en) * 2005-06-16 2006-12-20 엘지전자 주식회사 Manufacturing process of light emitting diode using aluminium buffer layer
KR100649763B1 (en) * 2005-12-09 2006-11-27 삼성전기주식회사 A method of producing vertical nitride light emitting devices
KR100867518B1 (en) 2006-09-06 2008-11-07 삼성전기주식회사 Method of manufacturing nitride-based semiconductor light emitting device
KR100874653B1 (en) 2007-07-30 2008-12-17 고려대학교 산학협력단 Gallium nitride light emitting diode and method for manufacturing the same

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