KR100638823B1 - Vertical nitride light emitting diode and a method of producing the same - Google Patents

Abstract

A nitride LED of a vertical structure is provided to improve light extraction efficiency by leaving a suitable thickness of a sapphire substrate so that the substrate is used as an intermediate refraction layer. An n-type nitride layer(52), an active layer(54) and a p-type nitride layer(56) are sequentially stacked in a nitride light emitting structure. A sapphire substrate(51) is formed on the n-type nitride layer, having a contact hole for opening a predetermined region of the n-type nitride layer. A reflective ohmic contact layer(57) is formed on the p-type nitride layer. A p-side bonding metal(59) is formed on the reflective ohmic contact layer. An n-side electrode(58) is formed on the sapphire substrate to be connected to a predetermined region of the n-type nitride layer through the contact hole. The sapphire substrate has a thickness corresponding to (2m+1)lambda/4n wherein m is an integer, lambda is a light emitting wavelength of the active layer, and n is an index of refraction of the sapphire substrate. The sapphire substrate can have a thickness of 0.1~50 micrometers.

Description

Vertical structure nitride light emitting device and manufacturing method {VERTICAL NITRIDE LIGHT EMITTING DIODE AND A METHOD OF PRODUCING THE SAME}

1 is a cross-sectional view showing a conventional vertical structure nitride light emitting device.

2 is a cross-sectional view showing a vertical nitride light emitting device according to the present invention.

3A through 3G are cross-sectional views of steps for explaining a method of manufacturing a vertical nitride light emitting device according to the present invention, respectively.

<Code Description of Main Parts of Drawing>

31, 51: sapphire substrate 32, 52: n-type nitride semiconductor layer

34,54: active layer 36,56: p-type nitride semiconductor layer

37, 57: reflective ohmic contact layer 38, 58: n-side electrode

39,59: p-side bonding metal

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical nitride light emitting device and a method of manufacturing the same. In particular, a vertical nitride light emitting device and a manufacturing method thereof, which prevent damage due to thermal shocks and the like that can be caused in a laser lift-off process and improve light extraction efficiency. It is about a method.

In general, a nitride semiconductor light emitting device is made of a nitride semiconductor material having Al _x In _y Ga _(1-xy) N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1). do. Such nitride semiconductor crystals are grown on a limited nitride single crystal growth substrate such as a sapphire substrate in consideration of lattice constant.

Since the sapphire substrate is an electrically insulating substrate, a nitride semiconductor light emitting device generally has a structure in which a p-side bonding metal and an n-side electrode are formed on the same surface. However, this structure is disadvantageous in that the current dissipation efficiency is lower and the overall effective light emitting area is smaller than that of the vertical structure light emitting device in which the electrodes are disposed on opposite surfaces of the device.

Therefore, in recent years, interest in vertical structure light emitting devices has been increasing. For example, Republic of Korea Patent No. 0483049 (Patent Holder: Samsung Electro-Mechanics Co., Ltd., published on April 15, 2005), after bonding a conductive wafer such as silicon on the opposite surface of the sapphire substrate, laser lift-off We propose a method of manufacturing a vertical nitride light emitting device that separates a sapphire substrate. One embodiment of the vertical structure nitride light emitting device obtained by such a manufacturing method is illustrated in FIG.

Referring to FIG. 1, a conventional nitride semiconductor light emitting device 20 includes a light emitting structure including a p-type nitride layer 12, an active layer 14, and an n-type nitride layer 16. It includes a reflective layer 22, such as Au, Ni, Ag, Al, or an alloy thereof formed on the lower surface of the p-type nitride layer 12, the reflective layer 22 is Au-Sn, Sn, In, Au-Ag, Ag- It is bonded with the silicon substrate 21 using a conductive adhesive layer 24 such as In, Ag-Ge, Ag-Cu or Pb-Sn. Such wafer bonding is performed under thermal conditions and high pressure conditions of at least 200 to 300 ° C., and then cooled to room temperature again after the process is completed. Therefore, stress is generated due to the coefficient of thermal expansion between the nitride layer and the sapphire substrate (not shown), and cracks may occur in some cases.

In the conventional vertical structure light emitting device manufacturing method, a laser lift-off process of separating the sapphire substrate is performed. Since the laser lift-off process inevitably generates a thermal shock, it may damage the nitride layer interface to be separated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a new vertical structure nitride light emitting device which further improves light extraction efficiency by using a sapphire substrate at an appropriate thickness and using it as an intermediate refractive index layer.

Another object of the present invention is to provide a method for manufacturing a novel vertical structured nitride light emitting device that can not only improve the light extraction efficiency while omitting the laser lift-off process but also significantly alleviate the thermal shock problem caused by the conventional wafer bonding process. have.

In order to achieve the above technical problem, the present invention,

A sapphire substrate having a nitride light emitting structure consisting of an n-type nitride layer, an active layer and a p-type nitride layer sequentially stacked, a contact hole formed on the n-type nitride layer and having one region of the n-type nitride layer open; A reflective ohmic contact layer formed on the p-type nitride layer, a p-side bonding metal formed on the reflective ohmic contact layer, and formed on the sapphire substrate to be connected to one region of the n-type nitride layer through the contact hole. A vertical nitride light emitting device including an n-side electrode is provided.

Preferably, the sapphire substrate has a thickness corresponding to (2m + 1) λ / 4n, where m is an integer such as 0,1,2, λ is the emission wavelength of the active layer, n is the refractive index of the sapphire substrate Can be. In this case, the sapphire substrate can act as a layer (hereinafter referred to as "intermediate refractive index layer") that corresponds to the middle refractive index of the outer and the nitride layer to further improve the light extraction efficiency. Preferred sapphire substrate thickness range may be 0.1 ~ 50㎛.

In a particular embodiment of the present invention, the reflective ohmic contact layer includes Ag, and the p-side bonding metal is formed on and surrounding the side of the reflective ohmic contact layer, thereby providing a barrier function to prevent movement of Ag. can do.

In contrast, the reflective ohmic contact layer may include an ohmic contact layer including In ₂ O ₃ including at least one selected from the group consisting of copper (Cu), zinc (Zn), and magnesium (Mg), and the ohmic contact layer. It is formed on, and may include a highly reflective metal layer made of aluminum (Al), silver (Ag), rhodium (Rh), ruthenium (Ru), platinum (Pt), palladium (Pd) and alloys thereof.

The present invention provides a method for manufacturing a nitride semiconductor light emitting device. The method includes forming a light emitting structure in which an n-type nitride layer, an active layer and a p-type nitride layer are sequentially stacked on a sapphire substrate, and forming a reflective ohmic contact layer in a pattern separated from each other on the p-type nitride layer. Forming a p-side bonding metal in a pattern corresponding to the pattern on the reflective ohmic contact layer, forming a contact hole in the sapphire substrate so that one region of the n-type nitride layer is exposed; And forming an n-side electrode on the sapphire substrate to be connected to one region of the n-type nitride layer through the contact hole, and cutting the resultant to be separated into individual light emitting devices.

As such, by forming contact holes in the sapphire substrate, the sapphire substrate can be held without a laser lift process. Furthermore, since the sapphire substrate has a refractive index of 1.7, which is intermediate between the refractive index (GaN: 2.4) of the nitride layer and the external refractive index (atmosphere: 1), the light extraction efficiency can be improved by remaining at the proper thickness of the sapphire substrate. .

The reflective ohmic contact layer and the p-side bonding metal may be formed in a pattern separated at regular intervals to mitigate thermal shock generated in the bonding process. Each pattern of the reflective ohmic contact layer and the p-side bonding metal is preferably formed separately from each individual light emitting device unit.

The method may further include attaching a supporting wafer on the p-side bonding metal between the forming of the p-side bonding metal and the forming of the contact hole in order to handle the wafer more easily. desirable.

In this case, the method may further include polishing the sapphire substrate so that the thickness of the sapphire substrate is reduced between attaching the support wafer and forming the contact hole. This is to facilitate the process of forming a contact hole for a solid sapphire substrate.

Here, the polishing of the sapphire substrate may be the polishing of the sapphire substrate to have a thickness corresponding to (2m + 1) λ / 4n (where m is an integer such as 0,1,2, and λ Is the emission wavelength of the active layer, and n is the refractive index of the sapphire substrate.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

2 is a cross-sectional view showing a vertical nitride light emitting device according to the present invention.

Referring to FIG. 2, the nitride semiconductor light emitting device 30 includes a light emitting structure including a p-type nitride layer 36, an active layer 34, and an n-type nitride layer 32. The reflective ohmic contact layer 37 is formed on the p-type nitride layer 36, and the p-side bonding metal 39 is formed thereon. The reflective ohmic contact layer 37 may include Ag. In this case, as illustrated, the p-side bonding metal 39 is formed to surround the side of the ohmic contact layer 37 to move Ag. To prevent.

Alternatively, the reflective ohmic contact layer 37 may adopt various known structures. For example, an ohmic contact layer made of In ₂ O ₃ including at least one selected from the group consisting of copper (Cu), zinc (Zn), and magnesium (Mg), and formed on the ohmic contact layer, the aluminum It may also include a highly reflective metal layer made of (Al), silver (Ag), rhodium (Rh), ruthenium (Ru), platinum (Pt), palladium (Pd) and alloys thereof.

The vertical nitride light emitting device 30 employed in the present invention has a form in which the sapphire substrate 31 remains on one main surface of the n-type nitride layer 32. The sapphire substrate 31 has a contact hole h formed to expose one region of the n-type nitride layer 32. The n-side electrode 38 formed on the sapphire substrate 31 may be connected to the n-type nitride layer 32 through the contact hole h. Therefore, the vertical nitride light emitting device 30 according to the present invention can omit the laser lift-off process. However, since the sapphire substrate 31 is a hard material, the thickness of the sapphire substrate 31 is preferably 50 μm or less in order to perform the contact hole (h) process more easily.

In addition, since the sapphire substrate 31 has an intermediate refractive index between the refractive index of the nitride and the refractive index of the atmosphere, the light extraction efficiency can be further improved. For this purpose, the sapphire substrate 31 preferably has a thickness corresponding to (2m + 1) λ / 4n. Where m is an integer such as 0, 1, 2, λ is the emission wavelength of the active layer 34, n may be the refractive index of the sapphire substrate 31. In order to fully acquire such light extraction effect, it is preferable to have thickness of at least 0.1 micrometer.

In this manner, instead of removing the sapphire substrate 31, the contact hole h is formed in the sapphire substrate 31, so that the substrate separation process that causes thermal shock can be omitted. Further, as a result, the sapphire substrate 31 having the intermediate refractive index can be left on the main light exit surface, so that the light extraction efficiency can be more effectively improved.

Hereinafter, the manufacturing method according to the present invention will be described in more detail with reference to FIGS. 3A to 3G.

3A through 3G are cross-sectional views of steps for explaining a method of manufacturing a vertical nitride light emitting device according to the present invention, respectively.

As shown in Fig. 3A, the manufacturing method according to the present invention starts with forming an n-type nitride layer 52, an active layer 54 and a p-type nitride layer 56 on the sapphire substrate 51. Although not shown, a buffer layer (not shown) may be formed on the sapphire substrate 51 before the nitride single crystal growth process. In addition, the sapphire substrate 51 used in this step has a constant thickness t1 to facilitate handling like a normal wafer.

3B, the reflective ohmic contact layer 57 is formed on the p-type nitride layer 56 in a pattern separated from each other at a predetermined interval D, and the reflective ohmic contact layer 57 is formed on the p-type nitride layer 56. The p-side bonding metal 59 is formed in a pattern corresponding to the pattern. As described above, since the ohmic contact layer 57 and the bonding metal 59 exist in a pattern separated by a predetermined interval D, the impact due to thermal shock in a subsequent process such as wafer bonding may be alleviated. In consideration of the subsequent cutting process, the separated patterns of the reflective ohmic contact layer 57 and the bonding metal 59 may be formed to correspond to individual device regions.

Next, a process of forming a contact hole in the sapphire substrate 51 so as to expose one region of the n-type nitride layer 52 is performed. Prior to this process, a process of reducing the thickness of the sapphire substrate 51 to an appropriate range may be performed as necessary. The process of reducing the thickness of the sapphire substrate 51 enables an easier contact hole forming process. This process may be carried out by a mechanical polishing process. In order to facilitate the handling of the substrate in the polishing process for reducing the thickness, a supporting substrate 60 may be further employed as shown in FIG. 3C.

Referring to FIG. 3C, a supporting substrate 60 is attached on the p-side bonding metal 59 pattern. Unlike the wafer bonding process, the supporting substrate 60 may be attached using the resin-based adhesive layer 61 so as not to damage the p-side bonding metal 59.

Subsequently, as shown in FIG. 3D, the exposed main surface of the sapphire substrate 51 is polished to reduce to a desired thickness t2. As described above, the sapphire substrate 51 is subjected to a polishing process to have a thickness of 50 μm or less so as to facilitate the contact hole process. However, the sapphire substrate 51 corresponds to (2m + 1) λ / 4n in consideration of light extraction efficiency. Polishing to have a thickness is preferred, where m is an integer such as 0, 1, 2, λ is the emission wavelength of the active layer, and n is the refractive index of the sapphire substrate.

Next, as shown in FIG. 3E, a contact hole h is formed on the polished sapphire substrate 51 so that a part of the n-type nitride layer 52 is exposed. The contact hole h is appropriately formed to be disposed at a position corresponding to each element. The contact hole (h) forming process may be appropriately performed through a process such as inductively coupled plasma (ICP) etching.

3F, an n-side electrode 58 is formed on the sapphire substrate 51 so as to be connected to the n-type nitride layer 52 through the contact hole h. In this way, by providing the contact hole h in the sapphire substrate 51 to form the n-side electrode 58, the desired contact structure can be completed without removing the sapphire substrate 51. As described above, since the remaining sapphire substrate 51 has an intermediate refractive index between the atmosphere and the nitride layer, the light extraction efficiency can be further improved.

Finally, as shown in FIG. 3E, the resultant may be cut into individual light emitting device units, and the supporting substrate 60 may be separated to obtain a desired nitride light emitting device. Each individual light emitting element has the same vertical structure as that shown in FIG.

According to the manufacturing method according to the present invention, by forming a contact hole in the sapphire substrate it is possible to form a suitable contact structure without separating the sapphire substrate, it is possible to improve the light extraction efficiency through the remaining sapphire substrate. In addition, as shown in FIG. 3B, the reflective ohmic contact layer and the p-side bonding metal are formed in a separated pattern at regular intervals, thereby reducing thermal shocks generated in the bonding process.

As such, the present invention is not limited by the above-described embodiments and the accompanying drawings, and is intended to be limited by the appended claims, and various forms of substitution may be made without departing from the technical spirit of the present invention described in the claims. It will be apparent to one of ordinary skill in the art that modifications, variations and variations are possible.

As described above, according to the present invention, it is possible to provide a vertical nitride light emitting device which further improves the light extraction efficiency by remaining the sapphire substrate in an appropriate thickness and using it as an intermediate refractive index layer. Since the laser lift-off process is omitted, the manufacturing process according to the present invention not only simplifies the process but also prevents damage due to thermal shock.

Claims (13)

A nitride light emitting structure consisting of an n-type nitride layer, an active layer and a p-type nitride layer sequentially stacked; A sapphire substrate formed on the n-type nitride layer and having a contact hole opening one region of the n-type nitride layer; A reflective ohmic contact layer formed on the p-type nitride layer; A p-side bonding metal formed on the reflective ohmic contact layer; And An n-side electrode formed on the sapphire substrate to be connected to one region of the n-type nitride layer through the contact hole; The sapphire substrate has a thickness corresponding to (2m + 1) λ / 4n, where m is an integer, λ is an emission wavelength of the active layer, and n is a refractive index of the sapphire substrate. . delete The method of claim 1, The sapphire substrate is a vertical nitride light emitting device, characterized in that having a thickness of 0.1 ~ 50㎛. The method of claim 1, The reflective ohmic contact layer includes Ag, and the p-side bonding metal is formed on top of the surrounding portion of the reflective ohmic contact layer. The method of claim 1, The reflective ohmic contact layer is formed on the ohmic contact layer and an ohmic contact layer made of In ₂ O ₃ including at least one selected from the group consisting of copper (Cu), zinc (Zn), and magnesium (Mg). And a highly reflective metal layer composed of aluminum (Al), silver (Ag), rhodium (Rh), ruthenium (Ru), platinum (Pt), palladium (Pd) and alloys thereof. device. Forming a light emitting structure in which an n-type nitride layer, an active layer, and a p-type nitride layer are sequentially stacked on a sapphire substrate; Forming a reflective ohmic contact layer on the p-type nitride layer in a pattern separated from each other; Forming a p-side bonding metal in a pattern corresponding to the pattern on the reflective ohmic contact layer; Forming a contact hole in the sapphire substrate to expose one region of the n-type nitride layer; Forming an n-side electrode on the sapphire substrate so as to be connected to one region of the n-type nitride layer through the contact hole; And A method of manufacturing a vertical nitride light emitting device comprising the step of cutting the resultant to be separated into individual light emitting devices. The method of claim 6, And attaching a supporting wafer on the p-side bonding metal between the step of forming the p-side bonding metal and the forming of the contact hole. The method of claim 7, wherein And polishing the sapphire substrate such that the thickness of the sapphire substrate is reduced between attaching the supporting wafer and forming the contact hole. The method of claim 6, Grinding the sapphire substrate is a step of polishing the sapphire substrate to have a thickness corresponding to (2m + 1) λ / 4n, where m is an integer, λ is the light emission wavelength of the active layer, n is sapphire A method for manufacturing a vertical structure nitride light emitting device, characterized in that the refractive index of the substrate. The method of claim 9, The polishing of the sapphire substrate is a method of manufacturing a vertical nitride light emitting device, characterized in that for polishing to have a thickness of 0.1 ~ 50㎛. The method of claim 6, And each pattern of the reflective ohmic contact layer and the p-side bonding metal is formed separately from each individual light emitting device unit. The method of claim 6, The reflective ohmic contact layer includes Ag, and the p-side bonding metal is formed on an upper portion of the reflective ohmic contact layer while surrounding the side. The method of claim 6, The reflective ohmic contact layer may include an ohmic contact layer made of In ₂ O ₃ including at least one selected from the group consisting of copper (Cu), zinc (Zn), and magnesium (Mg), and on the ohmic contact layer. And a highly reflective metal layer formed of aluminum (Al), silver (Ag), rhodium (Rh), ruthenium (Ru), platinum (Pt), palladium (Pd) and alloys thereof. Light emitting device manufacturing method.

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