Light-emitting element for display, and LED display apparatus including the same

Abstract

To provide a display apparatus capable of increasing an area of each sub-pixel in a restricted pixel area.SOLUTION: A light-emitting element includes: first, second and third light-emitting stacks each including a first conductive type semiconductor layer, an active layer, and a second conductive type semiconductor layer, which are stacked in the order; a first lower contact electrode that is in ohmic contact with the first light-emitting stack; a second lower contact electrode that is in ohmic contact with the second conductive type semiconductor layer of the second light-emitting stack; and a third lower contact electrode that is in ohmic contact with the second conductive type semiconductor layer of the third light-emitting stack. The second light-emitting stack is arranged between the first light-emitting stack and the third light-emitting stack, the first lower contact electrode is arranged between the first light-emitting stack and the second light-emitting stack, and the second and third lower contact electrodes are arranged between the second light-emitting stack and the third light-emitting stack. The first, second and third lower contact electrodes include a transparent conductive oxide layer, and the thickness of the second lower contact electrode or the third lower contact electrode is greater than the thickness of the first lower contact electrode.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a light-emitting element for a display and an LED display device having the same. [Background technology]

[0002] Light emitting diodes are inorganic light sources and are used in a variety of fields such as display devices, vehicle lamps, general lighting, etc. Light emitting diodes have advantages such as a long life, low power consumption, and fast response speed, and are quickly replacing existing light sources.

[0003] Meanwhile, conventional light emitting diodes have been mainly used as backlight sources in display devices, but in recent years, LED displays that directly display images using light emitting diodes have been developed.

[0004] A display device generally realizes various colors using a mixture of blue, green, and red colors. The display device includes a plurality of pixels to realize various images, and each pixel includes blue, green, and red sub-pixels. The hue of a particular pixel is determined by the hue of these sub-pixels, and an image is realized by combining these pixels.

[0005] Since LEDs can emit light of various hues depending on the material, a display device can be provided by arranging individual LED chips emitting blue, green, and red on a two-dimensional plane. However, if one LED chip is arranged for each subpixel, the number of LED chips increases, and the mounting process takes a long time.

[0006] Since the subpixels are arranged on a two-dimensional plane, the area occupied by one pixel including the blue, green, and red subpixels is relatively large. Therefore, in order to arrange the subpixels within the limited area, the area of ​​each LED chip must be reduced. However, reducing the size of the LED chip may make it difficult to mount the LED chip, and may also result in a reduction in the light-emitting area.

[0007] Meanwhile, display devices that realize various hues need to consistently provide high-quality white light. Conventional TVs use an RGB mixing ratio of 3:6:1 to realize the standard white light of D65. That is, the luminance of red is relatively higher than the luminance of blue, and the luminance of green is relatively the highest. However, currently used LED chips generally have a relatively high luminance of blue LEDs compared to other LEDs, which makes it difficult to match the RGB mixing ratio in display devices using each LED chip. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present disclosure is to provide a display device capable of increasing the area of ​​each sub-pixel within a limited pixel area.

[0009] Another problem to be solved by the present disclosure is to provide a display device capable of reducing the time required for a mounting process of a light emitting device.

[0010] Still another problem to be solved by the present disclosure is to provide a display device in which the RGB mixing ratio can be easily controlled. [Means for solving the problem]

[0011] A light-emitting element according to one embodiment of the present disclosure includes a first light-emitting stack, a second light-emitting stack, and a third light-emitting stack, each including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer; a first lower contact electrode in ohmic contact with the first light-emitting stack; a second lower contact electrode in ohmic contact with the second conductive type semiconductor layer of the second light-emitting stack; and a third lower contact electrode in ohmic contact with the second conductive type semiconductor layer of the third light-emitting stack; wherein the second light-emitting stack is disposed between the first light-emitting stack and the third light-emitting stack, the first lower contact electrode is disposed between the first light-emitting stack and the second light-emitting stack, and the second lower contact electrode and the third lower contact electrode are disposed between the second light-emitting stack and the third light-emitting stack, the first lower contact electrode, the second lower contact electrode, and the third lower contact electrode include a transparent conductive oxide layer, and a thickness of the second lower contact electrode or the third lower contact electrode is thicker than a thickness of the first lower contact electrode.

[0012] A display device according to an embodiment of the present disclosure includes a display substrate and a plurality of light emitting elements disposed on the display substrate, the light emitting elements being the light emitting elements described above. [Brief description of the drawings]

[0013] [Figure 1A] 1 is a schematic perspective view illustrating a light emitting device according to an embodiment of the present disclosure.

[0014] [Figure 1B] FIG. 1B is a schematic plan view of the light-emitting element of FIG. 1A.

[0015] [Figure 1C] FIG. 2 is a schematic cross-sectional view taken along line AA' in FIG. 1B. [Figure 1D] FIG. 2 is a schematic cross-sectional view taken along line BB' in FIG. 1B.

[0016] [Diagram 2] 1 is a schematic cross-sectional view of a light emitting stack structure according to one embodiment of the present disclosure.

[0017] [Figure 3A] 1B is a plan view illustrating a process for manufacturing the light emitting device of FIG. 1A according to an exemplary embodiment. [Figure 4A] 1B is a plan view illustrating a process for manufacturing the light emitting device of FIG. 1A according to an exemplary embodiment. [Figure 5A] 1B is a plan view illustrating a process for manufacturing the light emitting device of FIG. 1A according to an exemplary embodiment. [Figure 6A] 1B is a plan view illustrating a process for manufacturing the light emitting device of FIG. 1A according to an exemplary embodiment. [Figure 7A] 1B is a plan view illustrating a process for manufacturing the light emitting device of FIG. 1A according to an exemplary embodiment. [Figure 8A] 1B is a plan view illustrating a process for manufacturing the light emitting device of FIG. 1A according to an exemplary embodiment.

[0018] [Figure 3B] FIG. 3B is a cross-sectional view taken along line AA' of the corresponding plan view shown in FIG. 3A in accordance with an exemplary embodiment. [Figure 4B] FIG. 4B is a cross-sectional view taken along line AA' of the corresponding plan view shown in FIG. 4A in accordance with an exemplary embodiment. [Figure 5B] FIG. 5B is a cross-sectional view taken along line AA' of the corresponding plan view shown in FIG. 5A according to an exemplary embodiment. [Figure 6B] FIG. 6B is a cross-sectional view taken along line AA' of the corresponding plan view shown in FIG. 6A in accordance with an exemplary embodiment. [Figure 7B] 7B is a cross-sectional view taken along line AA' of the corresponding plan view shown in FIG. 7A in accordance with an exemplary embodiment. [Figure 8B] 8B is a cross-sectional view taken along line AA' of the corresponding plan view shown in FIG. 8A in accordance with an exemplary embodiment.

[0019] [Figure 3C] FIG. 3B is a cross-sectional view taken along line BB' of the corresponding plan view shown in FIG. 3A in accordance with an exemplary embodiment. [Figure 4C] FIG. 4B is a cross-sectional view taken along line BB' of the corresponding plan view shown in FIG. 4A in accordance with an exemplary embodiment. [Figure 5C] FIG. 5B is a cross-sectional view taken along line BB' of the corresponding plan view shown in FIG. 5A according to an exemplary embodiment. [Figure 6C] FIG. 6B is a cross-sectional view taken along line BB' of the corresponding plan view shown in FIG. 6A in accordance with an exemplary embodiment. [Figure 7C] FIG. 7B is a cross-sectional view taken along line BB' of the corresponding plan view shown in FIG. 7A in accordance with an exemplary embodiment. [Figure 8C] FIG. 8B is a cross-sectional view taken along line BB' of the corresponding plan view shown in FIG. 8A in accordance with an exemplary embodiment.

[0020] [Figure 9] 1B is a cross-sectional view showing a schematic manufacturing process of the light-emitting device of FIG. 1A according to an exemplary embodiment. [Figure 10] 1B is a cross-sectional view showing a schematic manufacturing process of the light-emitting device of FIG. 1A according to an exemplary embodiment. [Figure 11] 1B is a cross-sectional view showing a schematic manufacturing process of the light-emitting device of FIG. 1A according to an exemplary embodiment. [Figure 12] 1B is a cross-sectional view showing a schematic manufacturing process of the light-emitting device of FIG. 1A according to an exemplary embodiment. [Figure 13] 1B is a cross-sectional view showing a schematic manufacturing process of the light-emitting device of FIG. 1A according to an exemplary embodiment.

[0021] [Figure 14] 1A to 1C are cross-sectional views illustrating a manufacturing process of a light emitting package according to an embodiment of the present disclosure. [Figure 15] 1A to 1C are cross-sectional views illustrating a manufacturing process of a light emitting package according to an embodiment of the present disclosure. [Figure 16A] 1A to 1C are cross-sectional views illustrating a manufacturing process of a light emitting package according to an embodiment of the present disclosure. [Figure 16B] 1A to 1C are diagrams illustrating a manufacturing process of a light emitting package according to an embodiment of the present disclosure.

[0022] [Figure 17] 1 is a schematic cross-sectional view illustrating a display device according to an embodiment of the present disclosure.

[0023] [Figure 18] 11 is a schematic cross-sectional view illustrating a light emitting package according to another embodiment of the present disclosure.

[0024] [Figure 19] 4 is a schematic cross-sectional view of a light-emitting stack structure according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Each embodiment introduced below is provided as an example to fully convey the idea of ​​the present disclosure to those skilled in the art to which the present disclosure belongs. Therefore, the present disclosure is not limited to each embodiment described below, and may be embodied in other forms. In addition, in each drawing, the width, length, thickness, etc. of a component may be exaggerated for convenience. In addition, when one component is described as being "on" or "above" another component, it includes not only the case where each part is "directly above" or "directly above" the other part, but also the case where another component is interposed between each component and the other component. The same reference numerals throughout the specification refer to the same components.

[0026] A light-emitting element according to one embodiment of the present disclosure includes a first light-emitting stack, a second light-emitting stack, and a third light-emitting stack, each including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer; a first lower contact electrode in ohmic contact with the first light-emitting stack; a second lower contact electrode in ohmic contact with the second conductive type semiconductor layer of the second light-emitting stack; and a third lower contact electrode in ohmic contact with the second conductive type semiconductor layer of the third light-emitting stack; wherein the second light-emitting stack is disposed between the first light-emitting stack and the third light-emitting stack, the first lower contact electrode is disposed between the first light-emitting stack and the second light-emitting stack, and the second lower contact electrode and the third lower contact electrode are disposed between the second light-emitting stack and the third light-emitting stack, the first lower contact electrode, the second lower contact electrode, and the third lower contact electrode include a transparent conductive oxide layer, and a thickness of the second lower contact electrode or the third lower contact electrode is thicker than a thickness of the first lower contact electrode.

[0027] Since the first to third light emitting stacks overlap each other, the area of ​​each subpixel can be increased within a limited pixel area without increasing the pixel area. Furthermore, since the light emitting device includes the first to third light emitting stacks, the total number of light emitting devices used in a display can be reduced compared to conventional light emitting devices, thereby shortening the process time for mounting the light emitting devices.

[0028] Furthermore, by arranging the second lower contact electrode and the third lower contact electrode on the path of the light emitted from the second light-emitting stack, it is possible to prevent the light emitted from the third light-emitting stack from being lost by the lower contact electrodes. Furthermore, by forming the second lower contact electrode or the third lower contact electrode to be relatively thicker than the first lower contact electrode, it is possible to selectively reduce the luminous intensity of the light emitted from the second light-emitting stack.

[0029] Meanwhile, the first, second and third light-emitting stacks may be configured to emit red light, blue light and green light, respectively. The second light-emitting stack may emit blue light and the third light-emitting stack may emit green light, thereby increasing the luminance of the green light and, as a result, easily providing an RGB mixing ratio suitable for a display device.

[0030] In an embodiment, a thickness of the second bottom contact electrode may be greater than a thickness of the third bottom contact electrode.

[0031] In one embodiment, the second bottom contact electrode or the third bottom contact electrode may include a lower layer that is heat-treated to make ohmic contact with the second conductive type semiconductor layer, and an upper layer that is not heat-treated and disposed on the heat-treated lower layer. Further, the thickness of the upper layer that is not heat-treated may be thicker than the thickness of the heat-treated lower layer.

[0032] By achieving good ohmic contact using a heat-treated bottom layer and employing a top layer formed without heat treatment, the luminous intensity of the light emitted from the second light-emitting stack can be effectively reduced.

[0033] The first to third lower contact electrodes may include an ITO-based transparent conductive oxide layer, for example, ITO or ITZO.

[0034] Meanwhile, the first bottom contact electrode may be in ohmic contact with the second conductive type semiconductor layer of the first light emitting stack.

[0035] The light emitting element may further include a first connecting electrode electrically connected to the first light emitting stack; a second connecting electrode electrically connected to the second light emitting stack; a third connecting electrode electrically connected to the third light emitting stack; and a fourth connecting electrode commonly and electrically connected to the first, second, and third light emitting stacks.

[0036] Furthermore, the fourth connection electrode may be commonly electrically connected to the first conductive type semiconductor layers of the first to third light emitting stacks, and the first conductive type semiconductor layers may include an n-type semiconductor layer, thereby providing a light emitting device with a common n-structure.

[0037] The light emitting device may further include a protective layer surrounding at least a portion of the first to fourth connecting electrodes, the protective layer may include an epoxy molding compound or a polyimide film, and an upper surface of the protective layer may be substantially aligned with an upper surface of the first to fourth connecting electrodes.

[0038] The light emitting device may further include a substrate disposed adjacent to the third light emitting stack.

[0039] The light-emitting element may further include a first adhesive layer bonding the first light-emitting stack and the second light-emitting stack, and a second adhesive layer bonding the second light-emitting stack and the third light-emitting stack.

[0040] A display device according to an embodiment of the present disclosure includes a display substrate; and a plurality of light-emitting elements disposed on the display substrate; the light-emitting elements include a first light-emitting stack, a second light-emitting stack, and a third light-emitting stack, each including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer; a first lower contact electrode in ohmic contact with the first light-emitting stack; a second lower contact electrode in ohmic contact with the second conductive type semiconductor layer of the second light-emitting stack; and a third lower contact electrode in ohmic contact with the second conductive type semiconductor layer of the third light-emitting stack; the second light-emitting stack is disposed between the first light-emitting stack and the third light-emitting stack, the first lower contact electrode is disposed between the first light-emitting stack and the second light-emitting stack, the second lower contact electrode and the third lower contact electrode are disposed between the second light-emitting stack and the third light-emitting stack, the first lower contact electrode, and the third lower contact electrode include a transparent conductive oxide layer, and at least one of the second lower contact electrode and the third lower contact electrode is thicker than the first lower contact electrode.

[0041] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. In the following, a light emitting stack structure, a light emitting device, or a light emitting package may include a micro-LED, which has a light emitting area of ​​10000 μm or less as known in the art. 2 In another embodiment, the micro-LED is 4000 μm or less. 2 Below that, another 2500μm 2 It may have the following light emitting area:

[0042] FIG. 1A is a schematic oblique view illustrating a light-emitting element according to one embodiment of the present disclosure, FIG. 1B is a schematic plan view of the light-emitting element of FIG. 1A, and FIGS. 1C and 1D are schematic cross-sectional views taken along lines A-A' and B-B' of FIG. 1B, respectively.

[0043] 1A and 1B, the light emitting device 100 may include a light emitting stack structure, a first connecting electrode 20ce, a second connecting electrode 30ce, a third connecting electrode 40ce, and a fourth connecting electrode 50ce formed on the light emitting stack structure, and a protective layer 90 surrounding the connecting electrodes 20ce, 30ce, 40ce, and 50ce. An array of the light emitting devices 100 may be formed on the substrate 11, and the light emitting device 100 illustrated in FIG. 1A exemplarily shows a singulation from the array, and thus may be called a light emitting device. The formation and singulation of the light emitting devices 100 will be described in detail later. In some embodiments, the light emitting device 100 including the light emitting stack structure may be further processed to be formed into a light emitting package, which will also be described in detail later.

[0044] 1A to 1D, the light emitting device 100 according to the illustrated embodiment includes a light emitting stack structure, and may include a first LED subunit, a second LED subunit, and a third LED subunit disposed on a substrate. The first LED subunit may include a first light emitting stack 20, the second LED subunit may include a second light emitting stack 30, and the third LED subunit may include a third light emitting stack 40. Although the light emitting stack structure shows three light emitting stacks 20, 30, and 40, the present disclosure is not limited to a specific number of light emitting stacks. For example, in some embodiments, the light emitting stack structure may include two or more light emitting stacks. Here, a light emitting device 100 according to one embodiment will be described with respect to a light emitting stack structure including three light emitting stacks 20, 30, and 40.

[0045] The substrate 11 may include a light-transmitting insulating material to transmit light. However, in some embodiments, the substrate 11 may be formed to be semi-transparent or partially transparent so as to transmit only light of a specific wavelength or transmit only a part of light of a specific wavelength. The substrate 11 may be a growth substrate on which the third light-emitting stack 40 can be epitaxially grown, for example, a sapphire substrate. However, the substrate 11 is not limited to a sapphire substrate, and may include various other transparent insulating materials. For example, the substrate 11 may include glass, quartz, silicon, an organic polymer, or an organic-inorganic composite material, such as silicon carbide (SiC), gallium nitride (GaN), indium gallium nitride (InGaN), aluminum gallium nitride (AlGaN), aluminum nitride (AlN), gallium oxide (Ga2O3), or a silicon substrate. The substrate 11 may also include irregularities on the upper surface, for example, a patterned sapphire substrate. The inclusion of unevenness on the top surface can increase the extraction efficiency of light generated in the third light-emitting stack 40 in contact with the substrate 11. The unevenness of the substrate 11 can be employed to selectively increase the luminosity of the third light-emitting stack 40 compared to the first light-emitting stack 20 and the second light-emitting stack 30. Meanwhile, in other embodiments, the substrate 11 can be removed. By removing the substrate 11, the directional angle of the light emitted from the first to third light-emitting stacks 20, 30, and 40 can be narrowed, as described later.

[0046] The first, second and third light emitting stacks 20, 30, 40 are configured to emit light toward the substrate 11. Thus, light emitted from the first light emitting stack 20 can pass through the second and third light emitting stacks 30, 40. According to one embodiment, the first, second and third light emitting stacks 20, 30, 40 can emit light with different peak wavelengths. In one embodiment, the light emitting stacks farther from the substrate 11 can emit light with longer wavelengths than the light emitting stacks closer to the substrate 11, thereby reducing light loss. In another embodiment, the second light emitting stack 30 can emit light with shorter wavelengths than the third light emitting stack 40 to adjust the color mixing ratio of the first, second and third light emitting stacks 20, 30, 40. This can reduce the luminosity of the second light emitting stack 30 and increase the luminosity of the third light emitting stack 40, thereby dramatically changing the luminosity ratio of the light emitted from the first, second and third light emitting stacks. For example, the first light-emitting stack 20 may be configured to emit red light, the second light-emitting stack 30 may be configured to emit blue light, and the third light-emitting stack 40 may be configured to emit green light. This allows the luminous intensity of the blue light to be relatively decreased and the luminous intensity of the green light to be relatively increased, so that the luminous intensity ratio of the red, green, and blue colors can be easily adjusted to approach 3:6:1. Furthermore, the light-emitting areas of the first, second, and third light-emitting stacks 20, 30, and 40 are each approximately 10,000 μm 2 It may be less than 4000 μm, 2 , and even 2500 μm 2 Also, the light emitting area becomes larger closer to the substrate 11, and the luminous intensity of the green light can be further increased by disposing the third light emitting stack 40 that emits green light closest to the substrate 11.

[0047] The first light emitting stack 20 includes a first conductive type semiconductor layer 21, an active layer 23, and a second conductive type semiconductor layer 25. According to an embodiment, the first light emitting stack 20 may include a semiconductor material that emits red light, such as, but not limited to, AlGaAs, GaAsP, AlGaInP, and GaP.

[0048] The first upper contact electrode 21n may be disposed on the first conductive type semiconductor layer 21 and may form an ohmic contact with the first conductive type semiconductor layer 21. The first lower contact electrode 25p may be disposed under the second conductive type semiconductor layer 25. According to an embodiment, a portion of the first conductive type semiconductor layer 21 may be patterned and recessed, and the first upper contact electrode 21n may be disposed in the recessed region of the first conductive type semiconductor layer 21 to increase the ohmic contact level. The first upper contact electrode 21n may have a single layer structure or a multi-layer structure and may include, but is not limited to, Al, Ti, Cr, Ni, Au, Ag, Sn, W, Cu, or an alloy thereof, for example, an Au-Te alloy or an Au-Ge alloy. In an embodiment, the first upper contact electrode 21n may have a thickness of about 100 nm and may include a metal having high reflectivity to increase light emission efficiency in a downward direction toward the substrate 11.

[0049] The second light-emitting stack 30 includes a first conductive type semiconductor layer 31, an active layer 33, and a second conductive type semiconductor layer 35. According to an embodiment, the second light-emitting stack 30 may include a semiconductor material that emits blue light, such as, but not limited to, GaN, InGaN, or ZnSe. The second bottom contact electrode 35p is disposed below the second conductive type semiconductor layer 35 of the second light-emitting stack 30.

[0050] The third light emitting stack 40 includes a first conductive type semiconductor layer 41, an active layer 43, and a second conductive type semiconductor layer 45. According to an embodiment, the third light emitting stack 40 may include a semiconductor material that emits green light, such as GaN, InGaN, GaP, AlGaInP, AlGaP, etc. The third bottom contact electrode 45p is disposed on the second conductive type semiconductor layer 45 of the third light emitting stack 40.

[0051] According to one embodiment, each of the first conductivity type semiconductor layers 21, 31, 41 and the second conductivity type semiconductor layers 25, 35, 45 of the first, second and third light emitting stacks 20, 30, 40 may have a single layer structure or a multi-layer structure, and in some embodiments may include a superlattice layer. Furthermore, each of the active layers 23, 33, 43 of the first, second and third light emitting stacks 20, 30, 40 may have a single quantum well structure or a multi-quantum well structure.

[0052] Each of the first, second and third lower contact electrodes 25p, 35p and 45p may include a transparent conductive material that transmits light. For example, each of the lower contact electrodes 25p, 35p and 45p may include a transparent conductive oxide (TCO), such as, but not limited to, SnO, InO2, ZnO, ITO, ITZO, etc.

[0053] The position, material, thickness, etc. of each of the lower contact electrodes 25p, 35p, 45p may be selected so as to further reduce the luminance of blue light compared to red light and green light. For example, as shown in the figure, the second and third lower contact electrodes 35p, 45p may be disposed on the light emission path of blue light. Meanwhile, the lower contact electrodes 25p, 35p, 45p are not disposed on the light emission path of green light. That is, the third lower contact electrode 45p in ohmic contact with the third light-emitting stack 40 is disposed between the second light-emitting stack 30 and the third light-emitting stack 40.

[0054] In addition, the second lower contact electrode 35p or the third lower contact electrode 45p may be formed of a material that absorbs light and causes loss, for example, an ITO-based conductive oxide layer such as ITO or ITZO. In general, the shorter the wavelength of ITO, the greater the amount of light loss due to an increase in thickness. Therefore, by increasing the thickness of the second lower contact electrode 35p or the third lower contact electrode 45p arranged on the emission path of blue light, the transmittance of blue light can be reduced without significantly affecting the transmittance of red light. For example, when the first lower contact electrode 25p is also an ITO-based transparent conductive oxide layer, the thickness of the second lower contact electrode 35p or the third lower contact electrode 45p may be thicker than the thickness of the first lower contact electrode 25p. Furthermore, the thickness of the second lower contact electrode 35p may be thicker than the thickness of the third lower contact electrode 45p.

[0055] Meanwhile, the heat treatment temperature of the transparent electrodes affects the light transmittance, so that the heat treatment temperature of the first lower contact electrode 25p can be relatively higher than the heat treatment temperature of the second lower contact electrode 35p or the third lower contact electrode 45p in order to increase the transmittance of red light. For example, the first lower contact electrode 25p may be heat treated at a temperature of 500° C. or higher, and the second and third lower contact electrodes 35p, 45p may be heat treated at a temperature of 400° C. or lower.

[0056] Table 1 below shows an example of the transmittance depending on the ITO thickness and the heat treatment temperature.

[0057] [Table 1]

[0058] Referring to Table 1, it can be seen that under the same heat treatment conditions, the change in transmittance of red light with a wavelength of 625 nm is relatively smaller than the change in transmittance of blue light with a wavelength of 450 nm due to a thickness change of 2400 Å and 3600 Å. It can also be seen that at a heat treatment temperature of 500°C or higher, the transmittance is generally high for all wavelengths, and at a heat treatment temperature of 400°C or lower, the transmittance is generally low. On the other hand, in the case of ITO that has not been heat treated, it can be seen that the transmittance of blue light with a wavelength of 450 nm is relatively low when the thickness is large.

[0059] Therefore, in order to reduce the luminance of blue light, the thickness of the bottom contact electrodes 35p and / or 45p disposed on the light emission path of blue light can be increased and the heat treatment temperature can be reduced. Meanwhile, in order to prevent the luminance of red light from decreasing, the bottom contact electrode 25p can be heat treated at a relatively high temperature, particularly at a temperature of 400° C. or higher.

[0060] A first adhesive layer 61 is disposed between the first light emitting stack 20 and the second light emitting stack 30, and a second adhesive layer 63 is disposed between the second light emitting stack 30 and the third light emitting stack 40. The first and second adhesive layers 61, 63 may comprise a non-conductive material that transmits light. For example, the first and second adhesive layers 61, 63 may comprise an optically clear adhesive (OCA), which may include, but is not limited to, epoxy, polyimide, SU8, spin-on-glass (SOG), and benzocyclobutene (BCB).

[0061] According to the illustrated embodiment, the first insulating layer 81 and the second insulating layer 83 are disposed on at least a portion of each side of the first, second and third light emitting stacks 20, 30, 40. At least one of the first and second insulating layers 81, 83 may include various organic or inorganic insulating materials, such as polyimide, SiO2, SiNx, Al2O3, etc. For example, at least one of the first and second insulating layers 81, 83 may include a distributed Bragg reflector (DBR). As another example, at least one of the first and second insulating layers 81, 83 may include a black organic polymer. In some embodiments, an electrically floating metal reflective layer is disposed on the first and second insulating layers 81, 83 to reflect light emitted from each light emitting stack 20, 30, 40 toward the substrate 11. In some embodiments, at least one of the first and second insulating layers 81, 83 may have a single layer structure or a multi-layer structure formed of two or more insulating layers having different refractive indices.

[0062] According to an embodiment, each of the first, second and third light emitting stacks 20, 30 and 40 may be driven independently. More specifically, a common voltage may be applied to one of the first and second conductive type semiconductor layers of each light emitting stack, and an individual light emitting signal may be applied to the other one of the first and second conductive type semiconductor layers of each light emitting stack. For example, according to an embodiment of the present disclosure, the first conductive type semiconductor layers 21, 31 and 41 of each light emitting stack may be n-type, and the second conductive type semiconductor layers 25, 35 and 45 may be p-type. In this case, the third light emitting stack 40 may have a stacked sequence opposite to that of the first light emitting stack 20 and the second light emitting stack 30, so that the p-type semiconductor layer 45 is disposed on the upper part of the active layer 43, and the manufacturing process may be simplified. Hereinafter, the first conductive type and the second conductive type semiconductor layers may be expressed as n-type and p-type, respectively, according to the illustrated embodiment. Furthermore, the n-type and the p-type may be interchangeable with each other.

[0063] The first, second and third lower contact electrodes 25p, 35p, 45p connected to the p-type semiconductor layers 25, 35, 45 of each light emitting stack are electrically connected to the first to third connecting electrodes 20ce, 30ce, 40ce, respectively, and can receive corresponding light emitting signals. Meanwhile, the n-type semiconductor layers 21, 31, 41 of each light emitting stack may be commonly electrically connected to the fourth connecting electrode 50ce. Thus, the light emitting device 100 may have a common n-type light emitting stack structure in which the n-type semiconductor layers 21, 31, 41 of the first, second and third light emitting stacks 20, 30, 40 are commonly connected, and may be driven independently of each other. Since the light emitting device 100 has a common n-type light emitting stack structure, the sources of the voltages applied to the first, second and third light emitting stacks 20, 30, 40 can be different from each other.

[0064] Although the light emitting device 100 according to the illustrated embodiment has a common n-type structure, the present disclosure is not limited thereto. For example, in some exemplary embodiments, the first conductive type semiconductor layers 21, 31, 41 of each light emitting stack may be p-type, and the second conductive type semiconductor layers 25, 35, 45 of each light emitting stack may be n-type, thereby forming a common p-type light emitting stack structure. In addition, in some embodiments, the stacking sequence of each light emitting stack is not limited to that shown in the drawings, and may be variously modified. Hereinafter, the light emitting device 100 according to an embodiment of the present disclosure will be described with reference to a common n-type light emitting stack structure.

[0065] According to the illustrated embodiment, the light emitting device 100 includes a first pad 20pd, a second pad 30pd, a third pad 40pd, and a fourth pad 50pd. The first pad 20pd is electrically connected to the first lower contact electrode 25p through a first contact hole 20CH defined through the first insulating layer 81. The first connecting electrode 20ce is electrically connected to the first pad 20pd through a first through hole 20ct defined through the second insulating layer 83. The second pad 30pd is electrically connected to the second lower contact electrode 35p through a second contact hole 30CH defined through the first insulating layer 81. The second connecting electrode 30ce is electrically connected to the second pad 30pd through a second through hole 30ct defined through the second insulating layer 83.

[0066] The third pad 40pd is electrically connected to the third lower contact electrode 45p via a third contact hole 40CH defined through the first insulating layer 81. The third connecting electrode 40ce is electrically connected to the third pad 40pd via a third through hole 40ct defined through the second insulating layer 83. The fourth pad 50pd is connected to the first conductive type semiconductor layers 21, 31, 41 of the first, second, and third light-emitting stacks 20, 30, 40 via a first sub-contact hole 50CHa, a second sub-contact hole 50CHb, and a third sub-contact hole 50CHc defined on the first conductive type semiconductor layers 21, 31, 41 of the first, second, and third light-emitting stacks 20, 30, 40. In particular, the first sub-contact hole 50CHa may expose the first upper contact electrode 21n, and the fourth pad 50pd may be connected to the first upper contact electrode 21n through the first sub-contact hole 50CHa. In this manner, the fourth pad 50pd may be electrically connected to the first conductive type semiconductor layers 21, 31, and 41 through the sub-contact holes 50CHa, 50CHb, and 50CHc, thereby simplifying the manufacturing process of the light emitting device 100. The fourth connecting electrode 50ce is electrically connected to the fourth pad 50pd through a fourth through hole 50ct defined through the second insulating layer 83.

[0067] In this embodiment, each connecting electrode 20ce, 30ce, 40ce, 50ce is illustrated and described as being in direct contact with each pad 20pd, 30pd, 40pd, 50pd, respectively, but each connecting electrode 20ce, 30ce, 40ce, 50ce may not be directly connected to each pad 20pd, 30pd, 40pd, 50pd, and other connectors may be interposed between them.

[0068] The first, second, third and fourth pads 20pd, 30pd, 40pd and 50pd are separated and insulated from each other. According to an embodiment, the first, second, third and fourth pads 20pd, 30pd, 40pd and 50pd may cover at least a portion of the side of the first, second and third light emitting stacks 20, 30 and 40, respectively. This allows heat generated from the first, second and third light emitting stacks 20, 30 and 40 to be easily dissipated.

[0069] According to the illustrated embodiment, each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may have a substantially elongated shape protruding upward from the substrate 11. The connecting electrodes 20ce, 30ce, 40ce, and 50ce may include a metal such as, but not limited to, Cu, Ni, Ti, Sb, Zn, Mo, Co, Sn, Ag, or an alloy thereof. For example, each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may include two or more metals or multiple different metal layers to reduce stress from the elongated shape of each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce. In other embodiments, when the connecting electrodes 20ce, 30ce, 40ce, and 50ce include Cu, an additional metal may be evaporated or plated to inhibit oxidation of Cu. In some embodiments, when the connecting electrodes 20ce, 30ce, 40ce, and 50ce include Cu / Ni / Sn, Cu may prevent Sn from penetrating into the light-emitting stack structure. In some embodiments, the connecting electrodes 20ce, 30ce, 40ce, and 50ce may include a seed layer for forming a metal layer in a plating process, which will be described later.

[0070] As shown in the drawings, each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may have a substantially flat upper surface to facilitate electrical connection between external lines or electrodes and the light emitting stack structure, as described below. According to one embodiment of the present disclosure, the surface area of ​​the light emitting device 100, as known in the art, is about 10,000 μm 2 or less than about 4,000 μm in other embodiments. 2 Or 2,500μm 2 In the case where the light emitting device 100 includes a micro LED having a width of less than 100 mm, the connecting electrodes 20ce, 30ce, 40ce, and 50ce may overlap at least one of the first, second, and third light emitting stacks 20, 30, and 40 as shown in the drawings. More specifically, each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may overlap at least one step formed on a side of the light emitting stack structure. In this manner, since the area of ​​the lower surface of the connecting electrode is larger than the area of ​​the upper surface, a larger contact area may be formed between the connecting electrodes 20ce, 30ce, 40ce, and 50ce and the light emitting stack structure. This allows the connecting electrodes 20ce, 30ce, 40ce, and 50ce to be more stably formed on the light emitting stack structure. For example, the lengths L1, L2, L3, and L4 of one side disposed adjacent to the outer side of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may be different from the lengths L1', L2', L3', and L4' of one side disposed adjacent to the center of the light emitting device 100. More specifically, the length of one side of the connecting electrode disposed adjacent to the outside may be longer than the length of the other side disposed adjacent to the center of the light emitting device 100. For example, the difference between the length L and the length L' of the two opposing surfaces may be greater than the thickness (or height) of one of the light emitting stacks 20, 30, and 40. In this manner, the structure of the light emitting device 100 may be strengthened with a larger contact area between the connecting electrodes 20ce, 30ce, 40ce, and 50ce and the light emitting stack structure. In addition, the connecting electrodes 20ce, 30ce, 40ce, and 50ce may overlap at least one step formed on the side of the light emitting stack structure, so that heat generated in the light emitting stack structure may be more efficiently dissipated to the outside.

[0071] According to an exemplary embodiment, the difference between the length L1, L2, L3, or L4 of one side of the connecting electrode disposed adjacent to the outside and the length L1', L2', L3', or L4' of the other side disposed adjacent to the center of the light emitting device 100 may be about 3 μm. In this case, the light emitting stack structure may be formed to be thin. In particular, the first light emitting stack 20 may have a thickness of about 1 μm, the second light emitting stack 30 may have a thickness of about 0.7 μm, and the third light emitting stack 40 may have a thickness of about 0.7 μm, and the first and second adhesive layers may each have a thickness of about 0.2 μm to about 0.3 μm, but are not limited thereto. According to another embodiment, the difference between the length L1, L2, L3, or L4 of one side of the connecting electrode disposed adjacent to the outside and the length L1', L2', L3', or L4' of the other side disposed adjacent to the center of the light emitting device 100 may be about 10 μm to 16 μm. In this case, the light emitting stack structure may be formed to have a relatively thicker and more stable structure. In particular, the first light-emitting stack 20 may have a thickness of about 4 μm to about 5 μm, the second light-emitting stack 30 may have a thickness of about 3 μm, and the third light-emitting stack 40 may have a thickness of about 3 μm, and the thickness of the first and second adhesive layers may each be about 3 μm, but is not limited thereto. According to yet another exemplary embodiment, the difference between the length L1, L2, L3, or L4 of one side disposed adjacent to the outer side of the connecting electrode and the length L1', L2', L3', and L4' of the other side disposed adjacent to the center of the light-emitting device 100 may be about 25% of the length of the longest side. However, the concept of the present disclosure is not limited to a specific difference in length between the opposing surfaces of the connecting electrodes, and the difference in length between the opposing surfaces of the connecting electrodes may be varied.

[0072] In some example embodiments, at least one of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may overlap with a side surface of each of the light emitting stacks 20, 30, and 40, so that the light emitting stacks 20, 30, and 40 efficiently dissipate heat generated inside to the outside. In addition, when the connecting electrodes 20ce, 30ce, 40ce, and 50ce include a reflective material such as a metal, the connecting electrodes 20ce, 30ce, 40ce, and 50ce may reflect light emitted from at least one or more of the light emitting stacks 20, 30, and 40, so that light efficiency may be improved.

[0073] Typically, during manufacturing, an array of multiple light emitting devices is formed on a substrate. The substrate is cut along scribe lines to separate each light emitting device, and the light emitting devices can be transferred to another substrate or tape using various transfer techniques for further processing of the light emitting devices, such as packaging. In this case, if the light emitting device includes connecting electrodes, such as metal bumps or pillars, protruding outward from the light emitting structure, various problems can occur during subsequent processes, for example, during a transfer step, due to the structure of the light emitting device that exposes the connecting electrodes to the outside. In addition, it is possible for the light emitting device to be larger than about 10,000 μm depending on the application field. 2 Less than 4,000μm 2 Less than or about 2,500 μm 2 In some cases, including micro-LEDs, which have a surface area of ​​less than 100 nm, handling of the light-emitting elements can be made even more difficult by the small form factor.

[0074] For example, when the connecting electrode has a substantially long shape such as a rod, it is difficult to transfer the light emitting device using a conventional vacuum method because the light emitting device may not have a sufficient suction area due to the protruding structure of the connecting electrode. In addition, the exposed connecting electrode may be directly affected by various stresses during subsequent processes, such as when the connecting electrode comes into contact with a manufacturing device, which may damage the structure of the light emitting device. As another example, when the light emitting device is transferred by attaching an adhesive tape onto the upper surface (e.g., the surface opposite to the substrate) of the light emitting device, the contact area between the light emitting device and the adhesive tape may be limited to the upper surface of the connecting electrode. In this case, as opposed to when the adhesive tape is attached to the lower surface of the light emitting device (e.g., the substrate), the adhesion of the light emitting device to the adhesive tape may be weakened, and the light emitting device may be undesirably separated from the adhesive tape during transfer. As another example, when the light emitting device is transferred using a conventional pick-and-place method, an ejector pin may directly contact a portion of the light emitting device located between the connecting pins, damaging the upper structure of the light emitting structure. In particular, the ejection pin may strike the center of the light emitting element, causing physical damage to the upper light emitting stack of the light emitting element.

[0075] According to an embodiment of the present disclosure, the protective layer 90 may be formed on the light emitting stack structure. More specifically, as shown in FIG. 1A, the protective layer 90 may be formed between the connecting electrodes 20ce, 30ce, 40ce, and 50ce and cover at least a side surface of the light emitting stack structure. According to the illustrated embodiment, the protective layer 90 may expose the side surfaces of the substrate 11, the first and second insulating layers 81 and 83, and the third light emitting stack 40. The protective layer 90 may be formed substantially flush with the upper surfaces of the connecting electrodes 20ce, 30ce, 40ce, and 50ce and may include an epoxy molding compound (EMC). This may be formed in various colors such as black, white, or transparent, but the present disclosure is not limited thereto. For example, in some embodiments, the protective layer 90 may include polyimide (PID), in which case the PID may be provided as a non-liquid type dry film to increase flatness when applied to the light emitting stack structure. In some embodiments, the protective layer 90 may include a material having photosensitivity. In this manner, the protective layer 90 can provide a sufficient contact area for the light emitting device 100 to facilitate easy handling during a subsequent transfer step as well as protect the light emitting structure from external shocks that may be applied during subsequent processes. The protective layer 90 can also prevent light leakage to the sides of the light emitting device 100 and prevent or at least suppress interference of light emitted from adjacent light emitting devices 100.

[0076] 2 is a schematic cross-sectional view of a light emitting stack structure according to an embodiment of the present disclosure. The light emitting stack structure according to the illustrated embodiment is substantially the same as that included in the light emitting device 100 described above, and therefore, to avoid redundancy, a description of a configuration for forming the substantially same light emitting stack structure will be omitted.

[0077] Referring to FIG. 2, the first, second and third lower contact electrodes 25p, 35p and 45p according to an embodiment of the present disclosure are connected to the light-emitting signal line S R , S G , S BThe first conductive type semiconductor layers 21, 31, 41 of the first, second, and third light emitting stacks 20, 30, 40 may be connected to a common line Sc. The common line Sc may be connected to the first conductive type semiconductor layer 21 of the first light emitting stack 20 via a first upper contact electrode 21n.

[0078] The first to third lower contact electrodes 25p, 35p, 45p may be formed of an ITO-based transparent conductive oxide layer such as ITO or ITZO. In addition, in order to reduce the luminosity of blue light, the second lower contact electrode 35p or the third lower contact electrode 45p may be thicker than the first lower contact electrode 25p. In particular, the second lower contact electrode 35p may be thicker than the first and third lower contact electrodes 25p, 45p.

[0079] Meanwhile, in one embodiment of the present disclosure, by adopting an n-common structure, different voltages can be applied to the first to third light-emitting stacks 20, 30, 40. For example, a relatively lower voltage can be applied to the first light-emitting stack 20 emitting red light compared to the second and third light-emitting stacks 30, 40 emitting blue and green light. Therefore, a voltage source suitable for each light-emitting stack can be used individually, thereby reducing power loss. In the illustrated exemplary embodiment, the light-emitting signal line S R , S G , S B By using the common line Sc, the first, second and third light emitting stacks 20, 30, 40 can be individually controlled to selectively emit light.

[0080] 2 illustrates a light-emitting stack structure having an n-common structure, but the present disclosure is not limited thereto. For example, in some exemplary embodiments, the common line Sc is electrically connected to the lower contact electrodes 25p, 35p, and 45p of the first, second, and third light-emitting stacks 20, 30, and 40, respectively, and the light-emitting signal line S R , S G , S B may be coupled to the first conductive type semiconductor layers 21, 31, and 41 of the first to third light emitting stacks 20, 30, and 40, respectively.

[0081] The light emitting stack structure according to an embodiment of the present disclosure can display light of various hues according to the operating state of each of the light emitting stacks 20, 30, and 40, whereas the conventional light emitting device can display various hues by combining a number of light emitting cells that emit light of a single hue. More specifically, the conventional light emitting device generally includes light emitting cells that emit different colors of light, for example, red, green, and blue, spaced apart from each other along a two-dimensional plane to realize a full-color display. As such, a relatively large area may be occupied by the conventional light emitting cells. However, the light emitting stack structure according to an embodiment of the present disclosure can emit light of different hues by stacking a plurality of light emitting stacks 20, 30, and 40, and can realize full color by providing a high level of integration through a smaller area than the conventional light emitting device.

[0082] Furthermore, when each light emitting device 100 is mounted on another substrate to manufacture a display device, for example, the number of mounted elements may be significantly reduced compared to conventional light emitting devices. In this manner, the manufacture of a display device using the light emitting device 100 may be substantially simplified, particularly when hundreds of thousands or millions of pixels are formed in a single display device.

[0083] According to exemplary embodiments, the light emitting stack structure may further include various additional components to improve the purity and efficiency of light emitted therefrom. For example, in some exemplary embodiments, a wavelength pass filter may be disposed between each light emitting stack. In some embodiments, a concave-convex portion may be formed on the light emitting surface of at least one light emitting stack to balance the brightness of the light between each light emitting stack. For example, the luminance of green light needs to be increased to bring the luminance mixing ratio of RGB closer to 3:6:1, and therefore, the surface of the substrate 11 may be formed with concave-convex portions.

[0084] A method for forming a light emitting device 100 according to an embodiment of the present disclosure will now be described with reference to the drawings.

[0085] 3A, 4A, 5A, 6A, 7A, and 8A are plan views showing a process of manufacturing the light emitting device of FIG. 1A according to an exemplary embodiment. 3B, 4B, 5B, 6B, 7B, and 8B are cross-sectional views taken along line A-A' in the corresponding plan views shown in FIG. 3A, 4A, 5A, 6A, 7A, and 8A according to an exemplary embodiment. 3C, 4C, 5C, 6C, 7C, and 8C are cross-sectional views taken along line B-B' in the corresponding plan views shown in FIG. 3A, 4A, 5A, 6A, 7A, and 8A according to an exemplary embodiment. 9, 10, 11, 12, and 13 are cross-sectional views showing a schematic process of manufacturing the light emitting device of FIG. 1A according to an exemplary embodiment.

[0086] Referring again to FIG. 2, the first conductive type semiconductor layer 41, the third active layer 43, and the second conductive type semiconductor layer 45 of the third light emitting stack 40 may be sequentially grown on the substrate 11 by, for example, a metal organic chemical vapor deposition (MOCVD) method or a molecular beam epitaxy (MBE) method. The third lower contact electrode 45p may be formed on the third p-type semiconductor layer 45 by, for example, a physical vapor deposition method or a chemical vapor deposition method, and may include a transparent conductive oxide (TCO) such as SnO, InO2, ZnO, ITO, or ITZO. When the third light emitting stack 40 according to an embodiment of the present disclosure emits green light, the substrate 11 may include Al2O3 (e.g., a sapphire substrate), and the third lower contact electrode 45p may include a transparent conductive oxide (TCO) such as tin oxide. The first and second light emitting stacks 20 and 30 may be similarly formed by sequentially growing the first conductive type semiconductor layer, the active layer, and the second conductive type semiconductor layer, respectively, on a temporary substrate. A lower contact electrode including a transparent conductive oxide (TCO) may be formed on the second conductive type semiconductor layer by, for example, a physical vapor deposition method or a chemical vapor deposition method. The first and second light emitting stacks 20 and 30 may be bonded to each other with a first adhesive layer 61 interposed therebetween, and at least one of the temporary substrates of the first and second light emitting stacks 20 and 30 may be removed by a laser lift-off process, a chemical process, a mechanical process, or the like. The first and second light emitting stacks 20 and 30 may be bonded to the third light emitting stack 40 with a second adhesive layer 63 interposed therebetween, and the remaining temporary substrates of the first and second light emitting stacks 20 and 30 may be removed by a laser lift-off process, a chemical process, a mechanical process, or the like.

[0087] 3A, 3B and 3C, various portions of the first, second and third light emitting stacks 20, 30 and 40 may be patterned, for example, through an etching process, to expose the first conductive type semiconductor layer 21, the first lower contact electrode 25p, the first conductive type semiconductor layer 31, the second lower contact electrode 35p, the third lower contact electrode 45p and the first conductive type semiconductor layer 41. According to the illustrated embodiment, the first light emitting stack 20 has the smallest area among the light emitting stacks 20, 30 and 40. Meanwhile, the third light emitting stack 40 may have the largest area among the light emitting stacks 20, 30 and 40, thereby relatively increasing the luminosity of the third light emitting stack 40. However, the concept of the present disclosure is not particularly limited to the relative sizes of the light emitting stacks 20, 30 and 40.

[0088] 4A, 4B and 4C, a portion of an upper surface of the first conductive type semiconductor layer 21 of the first light emitting stack 20 may be patterned through wet etching to form a first upper contact electrode 21n. As described above, the first upper contact electrode 21n may be formed in the recessed region of the first conductive type semiconductor layer 21 to a thickness of about 100 nm, for example, to improve ohmic contact therebetween.

[0089] 5A, 5B and 5C, a first insulating layer 81 may be formed to cover the light emitting stacks 20, 30, 40, and a portion of the first insulating layer 81 may be removed to form the first, second, third and fourth contact holes 20CH, 30CH, 40CH and 50CH. The first contact hole 20CH may be defined on the first lower contact electrode 25p to expose a portion of the first lower contact electrode 25p. The second contact hole 30CH may be defined on the second lower contact electrode 35p to expose a portion of the second lower contact electrode 35p. The third contact hole 40CH may be defined on the third lower contact electrode 45p to expose a portion of the third lower contact electrode 45p.

[0090] The fourth contact hole 50CH provides a path for allowing electrical connection to the first conductive type semiconductor layers 21, 31, 41 of the first to third light emitting stacks 20, 30, 40. The fourth contact hole 50CH may include a first sub-contact hole 50CHa, a second sub-contact hole 50CHb, and a third sub-contact hole 50CHc. The first sub-contact hole 50CHa is defined on the first conductive type semiconductor layer 21 and can expose a part of the first upper contact electrode 21n, the second sub-contact hole 50CHb is defined on the first conductive type semiconductor layer 31 and can expose a part of the first conductive type semiconductor layer 31, and the third sub-contact hole 50CHc is defined on the first conductive type semiconductor layer 41 and can expose a part of the first conductive type semiconductor layer 41.

[0091] 6A, 6B, and 6C, the first, second, third, and fourth pads 20pd, 30pd, 40pd, and 50pd are formed on a first insulating layer 81 formed to have first, second, third, and fourth contact holes 20CH, 30CH, 40CH, and 50CH. The first, second, third, and fourth pads 20pd, 30pd, 40pd, and 50pd can be formed, for example, by forming a conductive layer substantially on the entire surface of the substrate 11 and patterning the conductive layer using a photolithography process.

[0092] The first pad 20pd may be formed to overlap the region where the first contact hole 20CH is formed, and may be connected to the first lower contact electrode 25p through the first contact hole 20CH. The second pad 30pd may be formed to overlap the region where the second contact hole 30CH is formed, and may be connected to the second lower contact electrode 35p through the second contact hole 30CH. The third pad 40pd may be formed to overlap the region where the third contact hole 40CH is formed, and may be connected to the third lower contact electrode 45p through the third contact hole 40CH. The fourth pad 50pd may be formed to overlap the region where the fourth contact hole 50CH is formed, particularly the region where the first, second and third sub-contact holes 50CHa, 50CHb and 50CHc are formed, and may be electrically connected to the first conductive type semiconductor layers 21, 31 and 41 of the first to third light-emitting stacks 20, 30 and 40.

[0093] 7A, 7B, and 7C, a second insulating layer 83 may be formed on the first insulating layer 81. The second insulating layer 83 may include silicon oxide and / or silicon nitride. However, the present disclosure is not limited thereto, and in some embodiments, the first and second insulating layers 81 and 83 may include an inorganic material. The second insulating layer 83 may then be patterned to form first, second, third, and fourth through holes 20ct, 30ct, 40ct, and 50ct exposing the first to fourth pads 20pd, 30pd, 40pd, and 50pd.

[0094] The first through hole 20ct formed on the first pad 20pd exposes a part of the first pad 20pd. The second through hole 30ct formed on the second pad 30pd exposes a part of the second pad 30pd. The third through hole 40ct formed on the third pad 40pd exposes a part of the third pad 40pd. The fourth through hole 50ct formed on the fourth pad 50pd exposes a part of the fourth pad 50pd. In the illustrated exemplary embodiment, the first, second, third and fourth through holes 20ct, 30ct, 40ct and 50ct may be defined within the regions in which the first, second, third and fourth pads 20pd, 30pd, 40pd and 50pd are formed, respectively.

[0095] 8A, 8B and 8C, the first, second, third and fourth connecting electrodes 20ce, 30ce, 40ce, 50ce are formed on the second insulating layer 83 in which the first, second, third and fourth through holes 20ct, 30ct, 40ct, 50ct are formed. The first connecting electrode 20ce may be formed to overlap the region in which the first through hole 20ct is formed, and may be connected to the first pad 20pd through the first through hole 20ct. The second connecting electrode 30ce may be formed to overlap the region in which the second through hole 30ct is formed, and may be connected to the second pad 30pd through the second through hole 30ct. The third connecting electrode 40ce may be formed to overlap the region in which the third through hole 40ct is formed, and may be connected to the third pad 40pd through the third through hole 40ct. The fourth connecting electrode 50ce may be formed to overlap a region in which the fourth through hole 50ct is formed, and may be connected to the fourth pad 50pd via the fourth through hole 50ct.

[0096] The first, second, third and fourth connecting electrodes 20ce, 30ce, 40ce, 50ce may be formed on the light emitting stack structure at a distance from each other. The first, second, third and fourth connecting electrodes 20ce, 30ce, 40ce, 50ce are electrically connected to the first, second, third and fourth pads 20pd, 30pd, 40pd, 50pd, respectively, and may transmit external signals to the light emitting stacks 20, 30, 40.

[0097] The method of forming the first, second, third and fourth connecting electrodes 20ce, 30ce, 40ce and 50ce is not particularly limited. For example, according to an embodiment of the present disclosure, a seed layer may be deposited on the light emitting stack structure as a conductive surface, and a photoresist pattern may be formed to expose the seed layer at the position where the connecting electrodes are to be formed. According to an embodiment, the seed layer may be deposited to a thickness of about 1000 Å, but is not limited thereto. The seed layer may then be plated with a metal such as Cu, Ni, Ti, Sb, Zn, Mo, Co, Sn, Ag, or an alloy thereof, and the photoresist pattern and seed layer remaining between each connecting electrode may be removed. In some exemplary embodiments, an additional metal may be deposited or plated on the plating metal (e.g., each connecting electrode) by electroless nickel immersion gold (ENIG), for example, to prevent or at least suppress oxidation of the plating metal. In some embodiments, the seed layer may remain on each connecting electrode.

[0098] According to the illustrated exemplary embodiment, each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may have a substantially elongated shape away from the substrate 11. In other exemplary embodiments, the connecting electrodes 20ce, 30ce, and 40ce may include two or more metals or multiple different metal layers to reduce stress from the elongated shape of the connecting electrodes 20ce, 30ce, 40ce, and 50ce. However, the present disclosure is not limited to a specific shape of the connecting electrodes 20ce, 30ce, 40ce, and 50ce, and in some embodiments, the connecting electrodes may have various shapes.

[0099] As shown in the drawings, each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may have a substantially flat upper surface to facilitate electrical connection between the light emitting stack structure and an external line or electrode. Each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may overlap at least one step formed on a side of the light emitting stack structure. In this manner, the lower surface of the connecting electrode may have a width larger than that of the upper surface, providing a larger contact area between the connecting electrodes 20ce, 30ce, 40ce, and 50ce and the light emitting stack structure, and the light emitting device 100 has a more stable structure that can withstand various subsequent processes together with the protective layer 90. In this case, the length L of one side of the connecting electrodes 20ce, 30ce, 40ce, and 50ce disposed adjacent to the outside and the length L' of the other surface disposed adjacent to the center of the light emitting device 100 may be different from each other. For example, the difference in length between two opposing surfaces of the connecting electrodes may be 3 μm to 16 μm, but is not limited thereto.

[0100] A protective layer 90 is disposed between the connecting electrodes 20ce, 30ce, 40ce, and 50ce. The protective layer 90 may be formed substantially flush with the upper surfaces of the connecting electrodes 20ce, 30ce, 40ce, and 50ce by a polishing process or the like. According to an embodiment, the protective layer 90 may include, but is not limited to, a black epoxy molding compound (EMC). For example, in some embodiments, the protective layer 90 may include a photosensitive polyimide dry film (PID). In this manner, the protective layer 90 may not only protect the light emitting structure from external impacts that may be applied during a subsequent process, but may also provide a sufficient contact area for the light emitting device 100 to facilitate handling during a subsequent transfer step. In addition, the protective layer 90 may prevent light leakage to the side of the light emitting device 100 and prevent or at least suppress interference of light emitted from adjacent light emitting devices 100.

[0101] FIG. 9 exemplarily illustrates a plurality of light emitting devices 100 disposed on a substrate 11, which undergo a singulation process to separate each light emitting device 100. Referring to FIG. 10, according to an embodiment of the present disclosure, laser beams may be irradiated between the light emitting stack structures to form separation paths that partially separate each light emitting stack structure. Referring to FIG. 11, a separation path may be added in the substrate 11 using a stealth laser. The stealth laser may be irradiated from a direction opposite to the laser irradiation surface in FIG. 10.

[0102] 12, in order to singulate each light emitting device 100 while the substrate 11 is attached to the first bonding layer 95, the substrate 11 may be cut or broken using various methods known in the art. For example, the substrate 11 may be cut by dicing the substrate 11 through scribing lines formed thereon, or the substrate 11 may be broken by applying mechanical force along a separation path formed during a laser irradiation process, for example. The first bonding layer 95 may be a tape, but the present disclosure is not limited thereto as long as the first bonding layer 95 can stably attach the light emitting device 100 while separating the light emitting device 100 in a subsequent process. Although it has been described that the first bonding layer 95 is attached to the substrate 11 after the laser irradiation step, in some exemplary embodiments, the first bonding layer 95 may be attached to the substrate 11 before the laser irradiation step.

[0103] Referring to FIG. 13, after the substrate 11 is separated into individual light emitting elements 100, the first bonding layer 95 may be expanded so that each light emitting element 100 may be spatially separated from one another.

[0104] 14, 15, and 16 are cross-sectional views that are schematic diagrams illustrating a process for manufacturing a light emitting package according to an embodiment of the present disclosure. The light emitting device 100 according to an embodiment of the present disclosure may be transferred and packaged by various methods known in the art. Hereinafter, a method of attaching a second adhesive layer 13 onto a substrate 11 using a carrier substrate 11c and transferring the light emitting device 100 will be described as an example, but the present disclosure is not limited to a specific transfer method.

[0105] 14, according to an embodiment of the present disclosure, the singulated light emitting device 100 may be transferred and disposed on a carrier substrate 11c with a second adhesive layer 13 interposed therebetween. In this case, if the light emitting device includes a connection electrode protruding outward from the light emitting stack structure, various problems may occur in subsequent processes, particularly in the transfer process, due to the non-uniform structure as described above. In addition, the light emitting device may be formed to have a thickness of about 10,000 μm depending on the application field. 2 Less than 4,000μm 2 Less than or about 2,500 μm 2 When the light emitting device includes a micro-LED having a surface area of ​​less than 100 mm, the small form factor may make the light emitting device more difficult to handle. However, providing the light emitting device 100 according to the exemplary embodiment in which the protective layer 90 is disposed between each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce not only facilitates the handling of the light emitting device 100 during subsequent processes such as transfer and packaging, but also protects the light emitting structure from external impacts and prevents optical interference between adjacent light emitting devices 100.

[0106] The carrier substrate 11c is not particularly limited as long as the carrier substrate 11c stably attaches the light emitting device 100 to the second adhesive layer 13. The second adhesive layer 13 may be a tape, but the present disclosure is not limited thereto as long as the second adhesive layer 13 stably attaches the light emitting device 100 to the carrier substrate 11c and allows the light emitting device 100 to be separated during a subsequent process. In some embodiments, the light emitting device 100 of FIG. 13 may be directly transferred to the circuit board 11p without being transferred to a separate carrier substrate 11c.

[0107] The light emitting device 100 may be mounted on a circuit board 11p. According to an embodiment, the circuit board 11p may include an upper circuit electrode 11pa, a lower circuit electrode 11pc, and a middle circuit electrode 11pb that are electrically connected to each other. Each upper circuit electrode 11pa may correspond to each of the first, second, third, and fourth connecting electrodes 20ce, 30ce, 40ce, and 50ce, respectively. In an exemplary embodiment, each upper circuit electrode 11pa is surface-treated with ENIG and partially melted at a high temperature, thereby facilitating electrical connection to each connecting electrode of the light emitting device 100.

[0108] According to the illustrated embodiment, the light-emitting elements 100 may be spaced apart from each other on the carrier substrate 11c at a desired pitch, preferably taking into account the pitch P (see FIG. 16B) of the upper circuit electrodes of the circuit substrate 11p to be mounted in a final target device such as a display device.

[0109] According to an embodiment of the present disclosure, the first, second, third and fourth connecting electrodes 20ce, 30ce, 40ce, 50ce of the light emitting device 100 may be bonded to the upper circuit electrode 11pa of the circuit board 11p, for example, by anisotropic conductive film (ACF) bonding. When the light emitting device 100 is bonded to the circuit board through ACF bonding, which may be performed at a lower temperature than other bonding methods, the light emitting device 100 can be prevented from being exposed to high temperatures during bonding. However, the present disclosure is not limited to a specific bonding method. For example, in some exemplary embodiments, each light emitting device 100 may be bonded to the circuit board 11p using anisotropic conductive paste (ACP), solder, ball grid array (BGA), or microbumps including at least one of Cu and Sn. In this case, the upper surfaces of the connecting electrodes 20ce, 30ce, 40ce, and 50ce and the protective layer 90 are substantially aligned with each other by a polishing process or the like, thereby increasing the adhesion of the light-emitting element 100 to the anisotropic conductive film and forming a more stable structure when bonded to the circuit board 11p.

[0110] Referring to FIG. 15 , a molding layer 91 is formed between each of the light emitting elements 100. According to an embodiment, the molding layer 91 can block light by reflecting or absorbing light emitted from the light emitting element 100. In an embodiment, the molding layer 91 can be aligned with the upper surface, i.e., the light emitting surface, of the light emitting element 100, thereby narrowing the directional angle of light emitted from the first to third light emitting stacks 20, 30, and 40. For example, the molding layer 91 can cover the side surface of the substrate 11 and be aligned with the upper surface of the substrate 11. Thus, the molding layer 91 can prevent light from being emitted to the side surface of the substrate 11 and narrow the directional angle. Furthermore, since the light emitting surface is limited to the upper surface of the substrate 11, the directional angles of light of the first to third light emitting stacks 20, 30, and 40 are approximately the same. In another embodiment, the molding layer 91 can cover the upper surface of the light emitting element 100. The molding layer 91 is disposed on the upper surface of the light emitting device 100 with a relatively thin thickness, and transmits light emitted from the light emitting device 100 and prevents light incident from the outside from being reflected by the light emitting device 100. The molding layer 91, together with the protective layer 90 formed on the light emitting device 100, strengthens the structure, thereby providing additional protection to the light emitting package.

[0111] In an exemplary embodiment, the molding layer 91 may include an organic or inorganic polymer. In some embodiments, the molding layer 91 may further include a filler, such as silica or alumina. In an exemplary embodiment, the molding layer 91 may include the same material as the protective layer 90. The molding layer 91 may be formed through various methods known in the art, such as lamination, plating, and / or printing methods. For example, the molding layer 91 may be formed through a vacuum lamination process in which an organic polymer sheet is placed on the light emitting device 100 and high temperature and pressure are applied in a vacuum, and the molding layer 91 may improve light uniformity by providing a substantially flat upper surface of the light emitting package. The molding layer 91 may be partially removed to expose the upper surface of the light emitting device 100 through a grinding process or a blanket etching process.

[0112] In some embodiments, the substrate 11 may be removed from the light emitting device 100 before the molding layer 91 is formed. In this case, the molding layer 91 may cover the side surface of the first conductive type semiconductor layer 41 and expose the top surface of the first conductive type semiconductor layer 41.

[0113] 16A and 16B, the light emitting devices 100 arranged on the circuit board 11p may be cut into a desired configuration to form a light emitting package 110. FIG. 16B includes four light emitting devices 100 (2x2) arranged on the circuit board 11p. However, the present disclosure is not limited to a specific number of light emitting devices formed in the light emitting package 110. For example, in some embodiments, the light emitting package 110 may include one or more light emitting devices 100 formed on the circuit board 11p. In addition, the present disclosure is not limited to a specific arrangement of the one or more light emitting devices 100 in the light emitting package 110, and for example, the one or more light emitting devices 100 in the light emitting package 110 may be arranged in an n×m array, where n and m are natural numbers. According to an embodiment, the circuit board 11p may include scan lines and data lines for independently driving each light emitting device 100 included in the light emitting package 110.

[0114] FIG. 17 is a schematic cross-sectional view illustrating a display device according to an embodiment of the present invention.

[0115] Referring to FIG. 17, the display device may include a display substrate 11b and a light-emitting package 110. The light-emitting package 110 may be mounted on a display substrate 11b of a final device such as a display device. The display substrate 11b may include target electrodes 11s corresponding to the lower circuit electrodes 11pc of the light-emitting package 110. The display device according to an embodiment of the present disclosure may include a plurality of pixels, and each light-emitting element 100 may be disposed corresponding to each pixel. More specifically, each light-emitting stack of the light-emitting element 100 according to an embodiment of the present disclosure may correspond to each sub-pixel of one pixel. Since the light-emitting element 100 includes the light-emitting stacks 20, 30, and 40 stacked vertically, the number of elements transferred to each sub-pixel may be substantially reduced compared to the number of conventional light-emitting elements. In addition, since the lengths of the opposing surfaces of the connecting electrodes are different from each other, the connecting electrodes can be stably formed in the light-emitting stack structure, and the internal structure can be strengthened. In addition, since the light-emitting element 100 according to some embodiments includes a protective layer 90 between each connecting electrode, the light-emitting element 100 can be protected from external impact.

[0116] In this embodiment, it is described that the light emitting package 110 is mounted on the display substrate 11b, but the process of manufacturing the light emitting package 110 can also be omitted and the molding layer 91 can be formed by directly mounting the light emitting element 100 on the display substrate 11b.

[0117] FIG. 18 is a schematic cross-sectional view illustrating a light emitting package according to another embodiment of the present disclosure.

[0118] 18, the light emitting package according to this embodiment is substantially similar to the light emitting package already described with reference to FIGS. 15, 16A, and 16B, but differs in that the light emitting device 200 does not include the substrate 11. The substrate 11 is removed from the light emitting device 100, thereby exposing the first conductive type semiconductor layer 41. The light emitting device 200 emits light through the upper surface of the first conductive type semiconductor layer 41, and as a result, the upper surface of the first conductive type semiconductor layer 41 becomes the light emitting surface. The molding layer 91 covers the side surface of the first conductive type semiconductor layer 41 and exposes its upper surface.

[0119] FIG. 19 is a schematic cross-sectional view of a light-emitting stack structure according to another embodiment of the present disclosure.

[0120] Referring to FIG. 19, the light-emitting stack structure according to this embodiment is different from the light-emitting stack structure described with reference to FIG. 2 in that the second lower contact electrode 135p includes a lower layer 135a and an upper layer 135b. The lower layer 135a and the upper layer 135b may be formed of an ITO-based transparent conductive oxide layer. However, the lower layer 135a may be heat-treated at a temperature of 300° C. or more to be in ohmic contact with the second conductive type semiconductor layer 35, and the upper layer 135b may be formed without heat treatment. In one embodiment, the lower layer 135a may be heat-treated at a temperature of 400° C. or less to reduce the transmittance of blue light. As can be seen with reference to Table 1, the transmittance of ITO for short wavelengths decreases as the thickness increases, and the transmittance when the ITO is not subjected to heat treatment is relatively low as the thickness increases. As a result, if the second lower contact electrode 135p is formed thick without heat treatment, the transmittance of blue light can be significantly reduced. However, since the second lower contact electrode 135p must be in ohmic contact with the second conductive type semiconductor layer 35, the heat treatment cannot be eliminated. For this reason, the present disclosure provides a second lower contact electrode 135p that is formed by separately forming a lower layer 135a that is in ohmic contact with the second conductive type semiconductor layer 35 and an upper layer 135b for increasing the thickness, and can further reduce the overall transmittance while being in ohmic contact with the second conductive type semiconductor layer 35. In particular, the lower layer 135a is formed for ohmic contact, and the upper layer 135b is formed for increasing the overall thickness, and the upper layer 135b may be thicker than the lower layer 135a.

[0121] In this embodiment, the second lower contact electrode 135p is described as including a heat-treated lower layer 135a and an upper layer 135b formed without heat treatment, but instead of or together with the second lower contact electrode 135p, the third lower contact electrode 45p may also be formed to include a lower layer that is heat-treated for ohmic contact and an upper layer that is formed without heat treatment.

[0122] Although certain exemplary embodiments and implementations have been described herein, other embodiments and modifications will become apparent from this description, and the present disclosure is therefore not limited to such embodiments, but rather encompasses the broader scope of the appended claims and various modifications and equivalent arrangements that will be apparent to those skilled in the art. [Explanation of symbols]

[0123] 11 Substrate 11b Display board 11c Carrier Board 11p circuit board 11pa Upper circuit electrode 11pb intermediate circuit electrode 11pc lower circuit electrode 13 Second adhesive layer 20 First luminous stack 20ce 1st connection electrode 20CH 1st Contact Hole 20ct 1st through hole 20pd 1st pad 21 First conductive type semiconductor layer 21n First upper contact electrode 23 Active layer 25 Second conductive type semiconductor layer 25-inch semiconductor layer 25p First bottom contact electrode 30 Second Luminous Stack 30ce 2nd connection electrode 30CH 2nd Contact Hole 30ct 2nd through hole 30pd 2nd pad 31 First conductive type semiconductor layer 33 Active layer 35 Second conductive type semiconductor layer 35p Second bottom contact electrode 40 3rd luminous stack 40ce 3rd connection electrode 40CH 3rd Contact Hole 40ct 3rd through hole 40pd 3rd pad 41 First conductive type semiconductor layer 43 Active layer 45 Second conductive type semiconductor layer 45p Third bottom contact electrode 50ce 4th connection electrode 50CH 4th Contact Hole 50CHa 1st sub-contact hole 50CHb Second sub-contact hole 50CHc 3rd sub-contact hole 50ct 4th through hole 50pd 4th pad 61 1st adhesive layer 63 Second adhesive layer 81 First insulating layer 83 Second insulating layer 90 protective layer 91 Molding Layer 95 1st bonding layer 100 Light emitting element 110 Light Emitting Package 135a Lower Layer 135b Upper layer 135p Second bottom contact electrode 200 Light emitting element

Claims

1. Circuit board; a first light emitting stack, a second light emitting stack, and a third light emitting stack disposed on the circuit substrate, each of the first light emitting stack and the third light emitting stack including a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and an active layer disposed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer; a first bottom contact electrode electrically connected to the first light emitting stack; a second bottom contact electrode electrically connected to the second conductivity type semiconductor layer of the second light emitting stack; and a third bottom contact electrode electrically connected to the second conductivity type semiconductor layer of the third light emitting stack; an insulating layer disposed between the first light emitting stack and the circuit board, the insulating layer including a first insulating layer having a first refractive index and a second insulating layer having a second refractive index; the second light-emitting stack is disposed between the first light-emitting stack and a third light-emitting stack; the first bottom contact electrode is disposed on the first light emitting stack; the second bottom contact electrode is disposed on the second light emitting stack; the third bottom contact electrode is disposed on the third light-emitting stack; the first lower contact electrode, the second lower contact electrode, and the third lower contact electrode each include a transparent conductive oxide layer; A light emitting element in which the second lower contact electrode or the third lower contact electrode has a thickness different from that of the first lower contact electrode.

2. The light-emitting element according to claim 1 , wherein the first lower contact electrode has a thickness smaller than a thickness of the second lower contact electrode or a thickness of the third lower contact electrode.

3. The light emitting device according to claim 1 , wherein the second lower contact electrode is thicker than the third lower contact electrode.

4. The light emitting device of claim 1 , wherein the first lower contact electrode, the second lower contact electrode, and the third lower contact electrode comprise an ITO-based transparent conductive oxide layer.

5. The light emitting device of claim 1 , wherein the first bottom contact electrode is in ohmic contact with the second conductivity type semiconductor layer of the first light emitting stack.

6. a first connecting electrode electrically connected to the first light emitting stack; a second connecting electrode electrically connected to the second light emitting stack; a third connecting electrode electrically connected to the third light emitting stack; and The light emitting device of claim 1 , further comprising: a fourth connection electrode commonly and electrically connected to the first light emitting stack, the second light emitting stack, and the third light emitting stack.

7. The fourth connection electrode is commonly electrically connected to the first conductive type semiconductor layers of the first to third light emitting stacks, The light emitting element according to claim 6 , wherein the first conductive type semiconductor layer includes an n-type semiconductor layer.

8. The light-emitting device of claim 6 , further comprising a molding layer surrounding at least a portion of the first light-emitting stack, the second light-emitting stack, and the third light-emitting stack.

9. 10. The light-emitting device of claim 8, wherein the molding layer comprises one of a polymer, an epoxy molding compound, or a polyimide film and has a white color.

10. The light-emitting device of claim 1 , further comprising a substrate disposed adjacent to the third light-emitting stack.

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