KR102474301B1 - Light emitting device - Google Patents

Abstract

Embodiments relate to a light emitting device in which a submount and a light emitting structure are thermally and stably bonded, and at the same time, light extraction efficiency is maximized, including a substrate; a light emitting structure disposed on one surface of the substrate and including a first semiconductor layer, an active layer, and a second semiconductor layer; A sub-mount including first and second electrodes and eutecticly bonded to the light emitting structure through a bonding layer; and a first barrier layer, a reflective layer, and a second barrier layer sequentially disposed between the light emitting structure and the first and second electrodes, wherein the second barrier layer is different from each other between the first electrode and the reflective layer. It has a structure in which a first metal layer and a second metal layer are alternately laminated one or more times.

Description

Light emitting device {LIGHT EMITTING DEVICE}

An embodiment of the present invention relates to a light emitting device with improved light extraction efficiency.

A light emitting diode (LED) is one of light emitting devices that emits light when a current is applied thereto. A light emitting diode can emit light with high efficiency at a low voltage, and thus has an excellent energy saving effect. Recently, the luminance problem of light emitting diodes has been greatly improved, and they are applied to various devices such as backlight units of liquid crystal display devices, electronic signboards, displays, and home appliances.

The light emitting diode may have a structure in which a first electrode and a second electrode are disposed on one side of a light emitting structure composed of a first semiconductor layer, an active layer, and a second semiconductor layer.

1 is a cross-sectional view of a general light emitting device.

As shown in FIG. 1, a general flip chip structure light emitting device includes a substrate 1, a first semiconductor layer 5, an active layer 6, and a second semiconductor layer 7 sequentially stacked on the substrate 1. It includes a light emitting structure, and the light emitting device may be mounted on a separate submount (2). At this time, the first electrode 3 and the second electrode 4 are disposed on the submount 2, respectively, and the first semiconductor layer 5 and the first electrode 3 are connected through the first bump 8. The second semiconductor layer 7 may be electrically connected to the second electrode 4 through the second bump 9 .

A technical problem to be achieved by the present invention is to provide a light emitting device in which a submount and a light emitting structure are thermally and stably bonded, and at the same time, light extraction efficiency is maximized.

The light emitting device of the embodiment of the present invention includes a substrate; a light emitting structure disposed on one surface of the substrate and including a first semiconductor layer, an active layer, and a second semiconductor layer; A sub-mount including first and second electrodes and eutecticly bonded to the light emitting structure through a bonding layer; and a first barrier layer, a reflective layer, and a second barrier layer sequentially disposed between the light emitting structure and the first and second electrodes, wherein the second barrier layer is different from each other between the first electrode and the reflective layer. It has a structure in which a first metal layer and a second metal layer are alternately laminated one or more times.

The light emitting device of the present invention has the following effects.

First, by eutectic bonding the light emitting structure and the submount, it is possible to bond the light emitting structure and the submount to be thermally stable.

Second, by disposing the first and second barriers on the top and bottom of the reflective layer, respectively, it is possible to prevent the reflectance of the reflective layer from being lowered due to eutectic bonding.

Third, by further disposing a second insulating layer on the first barrier, it is possible to prevent damage to the barrier layer, the reflective layer, and the like due to electrostatic discharge or external foreign matter.

1 is a cross-sectional view of a general light emitting device.
2 is a cross-sectional view of a light emitting device according to an embodiment of the present invention.
FIG. 3 is an enlarged view of region a of FIG. 2 .
4 is a graph showing the reflectance of a general light emitting device and a light emitting device according to an embodiment of the present invention.
5a and 5b are photographs showing the reflection of a general light emitting device and the reflectance of the light emitting device of an embodiment of the present invention.
6A to 6E are cross-sectional views of a light emitting device according to another embodiment of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated and described in the drawings. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms including ordinal numbers, such as first and second, may be used to describe various components, but the components are not limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a second element may be termed a first element, and similarly, a first element may be termed a second element, without departing from the scope of the present invention. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

Hereinafter, the embodiment will be described in detail with reference to the accompanying drawings, but the same or corresponding components regardless of reference numerals are given the same reference numerals, and overlapping descriptions thereof will be omitted.

Hereinafter, a light emitting device of an embodiment will be described in detail with reference to the accompanying drawings.

FIG. 2 is a cross-sectional view of a light emitting device according to an exemplary embodiment of the present invention, and FIG. 3 is an enlarged view of region a in FIG. 2 .

As shown in FIGS. 2 and 3, the light emitting device of the embodiment of the present invention includes a substrate 10, a light emitting structure 10a disposed on one surface of the substrate 10, a submount 30 and a light emitting structure 10a and a submount ( 30) includes bonding layers 20a and 20b for bonding. The light emitting structure 10a may be disposed on the substrate 10, and although not shown, the light emitting structure 10a may include a first semiconductor layer, an active layer, and a second semiconductor layer.

The substrate 10 includes a conductive substrate or an insulating substrate. Substrate 10 may be a carrier wafer or a material suitable for growing semiconductor materials. The substrate 10 may be formed of a material selected from sapphire (Al ₂ O ₃ ), SiC, GaAs, GaN, ZnO, Si, GaP, InP, and Ge, but is not limited thereto. The substrate 10 may be removed.

At this time, the thickness of the substrate 10 is 150㎛ to 270㎛, the thickness of the light emitting structure (10a) disposed on one surface of the substrate 10 may be 5㎛ to 10㎛, but is not limited thereto.

Although not shown, a buffer layer (not shown) may be further disposed between the light emitting structure 10a and the substrate 10 . The buffer layer may alleviate lattice mismatch between the light emitting structure 10a and the substrate 10 . The buffer layer may include a combination of Group III and V elements, or may include any one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, and AlInN. A dopant may be doped in the buffer layer, but is not limited thereto. The buffer layer may be grown as a single crystal on the substrate 10, and the buffer layer grown as a single crystal may improve the crystallinity of the light emitting structure 10a.

In particular, when the light generated from the light emitting structure 10a is emitted to the outside through the substrate 10, irregularities may be formed at the interface between the light emitting structure 10a and the substrate 10 to diffuse and disperse the light. The irregularities may have regular or irregular shapes, and the shape may be easily changed.

The first semiconductor layer may be implemented with a compound semiconductor such as group III-V or group II-VI, and the first semiconductor layer may be doped with a first dopant. The first semiconductor layer is a semiconductor material having a composition formula of In _x1 Al _y1 Ga _{1 -x1-y1} N (0≤x1≤1, 0≤y1≤1, 0≤x1+y1≤1), for example GaN, AlGaN , InGaN, InAlGaN, and the like. Also, the first dopant may be an n-type dopant such as Si, Ge, Sn, Se, or Te. When the first dopant is an n-type dopant, the first semiconductor layer doped with the first dopant may be an n-type semiconductor layer.

The active layer is a layer in which electrons (or holes) injected through the first semiconductor layer and holes (or electrons) injected through the second semiconductor layer meet. The active layer transitions to a lower energy level as electrons and holes recombine, and can generate light having a wavelength corresponding thereto.

The active layer may have a structure of any one of a single well structure, a multi well structure, a single quantum well structure, a multi quantum well (MQW) structure, a quantum dot structure, or a quantum wire structure, and the structure of the active layer is not limited thereto. don't

The second semiconductor layer is formed on the active layer and may be implemented with a compound semiconductor such as group III-V or group II-VI, and the second semiconductor layer may be doped with a second dopant. The second semiconductor layer is a semiconductor material having a composition formula of In _x2 Al _y2 Ga _{1 -x2- y2} N (0≤x2≤1, 0≤y2≤1, 0≤x2+y2≤1) or AlInN, AlGaAs, GaP, It may be formed of a material selected from GaAs, GaAsP, and AlGaInP. When the second dopant is a p-type dopant such as Mg, Zn, Ca, Sr, or Ba, the second semiconductor layer doped with the second dopant may be a p-type semiconductor layer.

The light emitting structure 10a as described above may be electrically connected to the first and second electrodes 32a and 32b of the submount 30 through the first and second bonding layers 20a and 20b.

The light emitting structure 10a and the submount 30 may be eutectic bonded through the first and second bonding layers 20a and 20b. Therefore, the light emitting device of the embodiment of the present invention is thermally stabilized than a general light emitting device in which the light emitting structure 10a and the submount 30 are bonded through reflow by reflowing paste or transparent epoxy, and thus the leakage current Reliability can be improved by reducing

If the thickness of the submount 30 is too thick, it is difficult to reduce the size and thickness of the light emitting device, and if the thickness is too thin, it does not have sufficient bearing capacity. Accordingly, the thickness of the sub-mount 30 may be 250 μm to 350 μm, but is not limited thereto.

The first and second bonding layers 20a and 20b may include a reflective material to prevent the reflection of the submount 30 from affecting characteristics of the light emitting device. For example, the first and second bonding layers 20a and 20b may include an alloy made of one or more materials selected from among Sn, Ag, Au, Cu, and Ni.

The light emitting structure 10a may be directly connected to the first and second electrodes 32a and 32b of the submount 30 through the first and second bonding layers 20a and 20b, and in the drawing, the light emitting structure 10a ) is connected to the first and second electrodes 32a and 32b through the second barrier layer 33.

The submount 30 may be formed of various materials having electrical conductivity and thermal conductivity. For example, the submount 30 may include SiC, Si, Ge, SiGe, AlN, metal, etc., but is not limited thereto. The thickness of the sub-mount 30 may be 200 nm to 400 nm, but is not limited thereto.

When the submount 30 is made of metal, the first insulating layer 31 is disposed between the submount 30 and the first and second electrodes 32a and 32b, so that the submount 30 and the first, The second electrodes 32a and 32b may be electrically insulated. For example, the first insulating layer 31 may be made of an insulating material such as SiO2, MgO, or SiN. In addition, the first insulating layer 31 may also have a multi-layer structure, but a single-layer structure is shown in the drawings. The thickness of the first insulating layer 31 may be 300 nm to 700 nm, but is not limited thereto.

In addition, when the sub-mount 30 is made of a non-conductive material, a metal layer for attaching the sub-mount to the lead frame may be further disposed on the rear surface of the sub-mount 30 . The metal layer may be selected from Ti, Ni, and Au or made of an alloy thereof. In addition, the metal layer may also be formed in a structure in which Ti/Ni/Au are sequentially stacked. In this case, the thickness of Ti may be 45 nm to 55 nm, the thickness of Ni may be 90 nm to 110 nm, and the thickness of Au may be 600 nm to 800 nm, but is not limited thereto. And, when the sub-mount 30 is made of the above-mentioned metal, the metal layer may be removed.

The first and second electrodes 32a and 32b include indium tin oxide (ITO), indium zinc oxide (IZO), indium zinc tin oxide (IZTO), indium aluminum zinc oxide (IAZO), indium gallium zinc oxide (IGZO), Indium gallium tin oxide (IGTO), aluminum zinc oxide (AZO), antimony tin oxide (ATO), gallium zinc oxide (GZO), IrOx, RuOx, RuOx/ITO, Ni/IrOx/Au, and Ni/IrOx/Au/ It may include at least one of ITO, but is not limited to these materials. In addition, the first and second electrodes 32a and 32b are In, Co, Si, Ge, Au, Pd, Pt, Ru, Re, Mg, Zn, Hf, Ta, Rh, Ir, W, Ti, Ag, A metal layer selected from Cr, Mo, Nb, Al, Ni, Cu, and WTi may be further included.

For example, the first and second electrodes 32a and 32b may have a structure in which Ti/Ni/Ti/Ni/Au are sequentially stacked. In this case, the thickness of Ti may be 45 nm to 55 nm, the thickness of Ni may be 90 nm to 110 nm, and the thickness of Au may be 1100 nm to 1500 nm, but is not limited thereto.

Although not shown, a barrier layer may be further disposed between the first and second electrodes 32a and 32b and the first insulating layer 31 . In this case, the barrier layer may include an oxide semiconductor such as Ti, Cr, or SnO 2 that is a thermally stable metal.

In addition, a reflective layer 34 may be further included in the submount 30 to propagate the light emitted from the light emitting structure 10a upward. The reflective layer 34 may include Al, Ag or an alloy of Al and Ag, but is not limited thereto. The thickness of the reflective layer 34 may be 100 nm to 250 nm, but is not limited thereto.

However, when eutectic bonding of the light emitting structure 10a and the submount 30 is performed through the first and second bonding layers 20a and 20b as described above, the reflective layer 34 is formed at about 300° C. to 350° C. Since it is exposed for a long time, Al, Ag, or alloy particles of Al and Ag of the reflective layer 34 may out-diffuse from the reflective layer 34 . That is, during eutectic bonding, the reflective layer 34 is damaged by heat, and thus the reflectance of the reflective layer 34 is reduced, and thus the luminous flux of the light emitting device may be reduced.

Therefore, in the embodiment of the present invention, in order to improve the thermal reliability of the reflective layer 34 and prevent the diffusion of particles of the reflective layer 34, the first barrier layer 35 and the second barrier are provided on the upper and lower portions of the reflective layer 34, respectively. Layer 33 is placed.

The first barrier layer 35 may include an oxide semiconductor such as Ti, Cr, Ni, or SnO 2 that is a thermally stable metal. The first barrier layer 35 blocks heat transferred to the reflective layer 34 during eutectic bonding, thereby minimizing a decrease in reflectance of the reflective layer 34 .

In particular, when the thickness of the first barrier layer 35 is too thick, the transmittance of light reflected from the reflective layer 34 may decrease, and when the thickness of the first barrier layer 35 is too thin, the first barrier layer 35 It cannot perform the function of blocking this column. Accordingly, the first barrier layer 35 may have a thickness of 1 nm to 2 nm, but is not limited thereto.

For example, when the first barrier layer 35 has a structure in which Ti/Ni/Ti/Ni are sequentially stacked, the thickness of Ti may be 45 nm to 55 nm, the thickness of Ni may be 90 nm to 110 nm, , but not limited to

4 is a graph showing the reflectance of a general light emitting device and a light emitting device according to an embodiment of the present invention.

And, Table 1 below is a table comparing the reflectance of the conventional light emitting device and the light emitting device of the embodiment of the present invention.

As shown in FIG. 4 and Table 1, in a general light emitting device including a reflective layer made of Ag, during eutectic bonding, Ag particles of the reflective layer are emitted to the outside, and the reflectance of the reflective layer may decrease. In particular, when the light emitting structure emits blue light in a wavelength range of 420 nm, the reflectance is 80% or less.

On the other hand, in the embodiment of the present invention, the first barrier layer 35 including Ti is disposed on the reflective layer 34, so that the degree of decrease in the reflectance of the reflective layer 34 can be reduced.

conventional Example of the present invention reflective layer Ag Ag Presence of 1st barrier No first barrier A first barrier made of Ti heat treatment method Alloy Hot Plate Alloy Hot Plate reflectivity(%) 80.2 63.7 92.4 93.3

Referring again to FIGS. 2 and 3 , the second barrier layer 33 is disposed under the reflective layer 34 to prevent particles included in the reflective layer 34 from being diffused by heat. To this end, the second barrier layer 33 may have a structure in which the first metal layer 33a and the second metal layer 33b are alternately stacked one or more times, and in the drawing, the first metal layer 33a and the second metal layer It is shown that (33b) is a structure in which two layers are alternately laminated.

The first and second metal layers 33a and 33b may be selected from the group consisting of Ni, Pt, Cr, Ti, and W. For example, the first metal layer 33a may include Ti, and the second metal layer 33b may include Ni. In this case, the thickness of the first metal layer 33a may be 20 nm to 50 nm, and the thickness of the second metal layer 33b may be 40 nm to 100 nm, but the thickness is not limited thereto.

Therefore, in the light emitting device according to the embodiment of the present invention, the first and second barrier layers 35 and 33 are respectively disposed above and below the reflective layer 34, and the second barrier layer 33 diffuses particles of the reflective layer 34. In order to easily prevent this, the first and second metal layers 33a and 33b may be arranged to alternate at least once.

On the other hand, as described above, in the embodiment of the present invention, since the light emitting structure 10a is connected to the first and second electrodes 32a and 32b through the second barrier layer 33, the first and second bonding layers ( 20a and 20b) may be electrically connected to the second barrier layer 33 exposed by selectively removing the first barrier layer 35 and the reflective layer 34 .

5a and 5b are photographs showing the reflection of a general light emitting device and the reflectance of the light emitting device of an embodiment of the present invention.

As shown in FIG. 5A, when the first barrier layer 35 is not disposed on the reflective layer 34 including Ag, when the heat treatment is performed, the Ag particles of the reflective layer 34 are diffused to form particles in the reflective layer 34. present on the surface, the reflectance of the reflective layer 34 is reduced. Accordingly, the luminous flux of the light emitting element is lowered.

On the other hand, as shown in FIG. 5B, when the first barrier layer 35 including Ti is disposed on the reflective layer 34 including Ag, the first barrier layer 35 is thermally damaged even when heat treatment is performed. By minimizing , Ag particles do not exist on the surface of the reflective layer 34 .

Hereinafter, a light emitting device of another embodiment of the present invention will be described in detail.

6A to 6E are cross-sectional views of a light emitting device according to another embodiment of the present invention.

As shown in FIG. 6A , the first and second bonding layers 20a and 20b are directly eutectic bonded to the first barrier layer 35 so that the submount 30 and the light emitting structure 10a may be electrically connected. In this case, the first barrier layer 35 may be made of a metal such as Ti or Cr.

And, as shown in FIG. 6B, when the first barrier layer 35 is made of an oxide semiconductor such as SnO2, the first and second bonding layers 20a and 20b are exposed by selectively removing the first barrier layer 35. may be electrically connected to the reflective layer 34.

Also, as shown in FIGS. 6C to 6E , a second insulating layer 36 may be further disposed on the first barrier layer 35 . Like the first insulating layer 31, the second insulating layer 36 may be made of an insulating material such as SiO2, MgO, or SiN. The second insulating layer 36 is formed by the barrier layers 33, 35, the reflective layer 34, etc., when an electrostatic discharge (ESD) of thousands of volts or higher is generated when a light emitting element contacts an object or by an external foreign substance. It can function as a protective layer to prevent damage. The thickness of the second insulating layer 36 may be 300 nm to 700 nm, but is not limited thereto.

Accordingly, as shown in FIG. 6C , the first and second bonding layers 20a and 20b may be electrically connected to the first barrier layer 35 exposed by selectively removing the second insulating layer 36 . In addition, although the drawing shows that the second insulating layer 36 is disposed only on the first barrier layer 35, the second insulating layer 36 is formed on the side surfaces of the barrier layers 33 and 35, the reflective layer 34, and the like. It may be further extended to enclose the .

In addition, as shown in FIG. 6D, the first and second bonding layers 20a and 20b are formed by selectively removing the second insulating layer 36 and the first barrier layer 35 to expose the upper surface of the reflective layer 34 and Direct contact or, as shown in FIG. 6E, the first and second bonding layers 20a and 20b are exposed by selectively removing the second insulating layer 36, the first barrier layer 35, and the reflective layer 34. 2 may be in direct contact with the top surface of the barrier layer 33 .

In the light emitting device of the embodiment of the present invention as described above, the light emitting structure 10a and the submount 30 may be eutectic bonded to thermally stable the light emitting structure 10a and the submount 30 . In particular, first and second barriers 35 and 33 are disposed above and below the reflective layer 34 to prevent the reflectance of the reflective layer 34 from being lowered due to eutectic bonding, and the first barrier 35 ), the barrier layers 33 and 35, the reflective layer 34, etc. may be prevented from being damaged by electrostatic discharge or external foreign matter by further disposing the second insulating layer 36 on the .

The light emitting device of the embodiment of the present invention as described above may further include an optical member such as a light guide plate, a prism sheet, or a diffusion sheet to function as a backlight unit. In addition, the light emitting device of the embodiment may be further applied to a display device, a lighting device, and a pointing device.

In this case, the display device may include a bottom cover, a reflector, a light emitting module, a light guide plate, an optical sheet, a display panel, an image signal output circuit, and a color filter. The bottom cover, the reflector, the light emitting module, the light guide plate, and the optical sheet may form a backlight unit.

A reflector is disposed on the bottom cover, and the light emitting module emits light. The light guide plate is disposed in front of the reflector to guide light emitted from the light emitting device forward, and the optical sheet includes a prism sheet and is disposed in front of the light guide plate. A display panel is disposed in front of the optical sheet, an image signal output circuit supplies image signals to the display panel, and a color filter is disposed in front of the display panel.

In addition, the lighting device may include a light source module including a substrate and a light emitting device according to an embodiment, a heat dissipation unit dissipating heat from the light source module, and a power supply unit processing or converting an electrical signal received from the outside and providing the electrical signal to the light source module. . Furthermore, the lighting device may include a lamp, a head lamp, or a street lamp.

The present invention described above is not limited to the above-described embodiments and accompanying drawings, and various substitutions, modifications, and changes are possible within a range that does not depart from the technical spirit of the embodiments. It will be clear to those who have knowledge.

10: substrate 10a: light emitting structure
20a: first bonding layer 20b: second bonding layer
30: submount 31: first insulating layer
32a: first electrode 32b: second electrode
33: second barrier layer 33a: first metal layer
33b: second metal layer 34: reflective layer
35: first barrier layer 36: second insulating layer

Claims (12)

Board;
a light emitting structure disposed on one surface of the substrate and including a first semiconductor layer, an active layer, and a second semiconductor layer;
A submount including first and second electrodes and eutecticly bonded to the light emitting structure through first and second bonding layers; and
A first barrier layer, a reflective layer, and a second barrier layer sequentially disposed between the light emitting structure and the first and second electrodes,
The second barrier layer has a structure in which first metal layers and second metal layers that are different from each other are alternately stacked one or more times between the first electrode and the reflective layer. According to claim 1,
The thickness of the first barrier layer is smaller than the thickness of the reflective layer,
The thickness of the first barrier layer is 1 nm to 2 nm,
The first barrier layer is made of a metal selected from among Ti and Ni or an oxide semiconductor,
A thickness of the reflective layer is 100 nm to 250 nm light emitting device. According to claim 1,
The reflective layer includes Al, Ag or an alloy of Al and Ag,
The first metal layer of the second barrier layer is Ti, the second metal layer of the second barrier layer is Ni or W,
The first and second bonding layers are in direct contact with the top surface of the first barrier layer.
light emitting element. According to claim 1,
The first and second bonding layers are in direct contact with the reflective layer exposed by selectively removing the first barrier layer, or
A light emitting device directly in contact with the second barrier layer exposed by selectively removing the first barrier layer and the reflective layer. According to claim 1,
Further comprising an insulating layer disposed on the first barrier layer,
The first and second bonding layers may be in direct contact with the upper surface of the first barrier layer exposed by selectively removing the insulating layer, or the first and second bonding layers may be in direct contact with the insulating layer and the first barrier layer. A light emitting device that is in direct contact with the top surface of the reflective layer exposed by selectively removing the light emitting device, or in direct contact with the second barrier layer exposed by selectively removing the insulating layer, the first barrier layer, and the reflective layer. delete delete delete delete delete delete delete

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