Light emitting device and LED display device having the same

Abstract

A light-emitting element is provided, which includes: a first light-emitting stack; a second light-emitting stack disposed below the first light-emitting stack; a third light-emitting stack disposed below the second light-emitting stack; first to fourth connecting electrodes disposed above the first light-emitting stack and electrically connected to the first to third light-emitting stacks; and a bonding metal layer disposed on upper surfaces of the first to fourth connecting electrodes, wherein the first to fourth connecting electrodes each include a groove on their upper surface, and the bonding metal layer covers the groove of the first to fourth connecting electrodes, respectively.

Description

[Technical field]

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

[0002] Light emitting diodes, as inorganic light sources, 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 rapidly replacing existing light sources.

[0003] Conventionally, 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, and the color of a particular pixel is determined by the colors of these sub-pixels, and an image is realized by a combination of these pixels.

[0005] LEDs can emit light of various colors depending on the material, and a display device can be provided by arranging individual light emitting elements emitting blue, green, and red on a two-dimensional plane. However, when arranging one light emitting element for each subpixel, the number of light emitting elements increases, which takes a lot of time for the mounting process.

[0006] Meanwhile, light-emitting elements have generally been mounted on circuit boards and the like using surface mounting technology. Surface mounting technology is a technique for bonding light-emitting elements onto circuit boards using solder paste. However, extremely small light-emitting elements called micro LEDs are not suitable for mounting using conventional surface mounting technology because the spacing between bump pads is extremely small. Therefore, a new technology suitable for mounting extremely small light-emitting elements is required. Summary of the Invention [Problem to be solved by the invention]

[0007] Exemplary embodiments provide a light emitting device and a display device that can reduce the mounting process time.

[0008] Exemplary embodiments provide light emitting devices and display devices having the same that are suitable for probing and mounting for electrical measurements. [Means for solving the problem]

[0009] In an illustrative embodiment, a light-emitting element is provided, the light-emitting element including: a first light-emitting stack; a second light-emitting stack disposed below the first light-emitting stack; a third light-emitting stack disposed below the second light-emitting stack; first to fourth connecting electrodes disposed on top of the first light-emitting stack and electrically connected to the first to third light-emitting stacks; and a bonding metal layer disposed on upper surfaces of the first to fourth connecting electrodes, each of the first to fourth connecting electrodes including a groove on its upper surface, and the bonding metal layer covering the groove of each of the first to fourth connecting electrodes.

[0010] In an exemplary embodiment, a display device is provided, the display device including a display substrate having bonding pads, and a light-emitting element disposed on the display substrate, the light-emitting element including a first light-emitting stack; a second light-emitting stack disposed below the first light-emitting stack; a third light-emitting stack disposed below the second light-emitting stack; first to fourth connecting electrodes disposed above the first light-emitting stack and electrically connected to the first to third light-emitting stacks; and a bonding metal layer disposed on upper surfaces of the first to fourth connecting electrodes, the first to fourth connecting electrodes each including a groove on an upper surface, the bonding metal layer covering the grooves of the first to fourth connecting electrodes, respectively, and the bonding metal layer being eutectic bonded to the bonding pad. [Brief description of the drawings]

[0011] [Figure 1A] FIG. 1A is a schematic plan view of a light emitting device according to an embodiment. [Figure 1B] 1B and 1C are schematic cross-sectional views taken along cut lines AA' and BB', respectively, of FIG. 1A. [Figure 1C] 1B and 1C are schematic cross-sectional views taken along cut lines AA' and BB', respectively, of FIG. 1A. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a light-emitting stack structure according to one embodiment of the present disclosure. [Figure 3A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 3B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 3C] Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 4A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 4B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 4C] Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 5A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 5B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 5C]Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 6A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 6B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 6C] Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 7A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 7B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 7C]Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 8A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 8B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 8C] Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 9A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 9B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 9C]Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 10A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 10B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 10C] Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 11A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 11B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 11C]Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 12A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 12B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 12C] Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 13A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 13B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 13C]Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 14A] Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A are plan views for explaining a method of manufacturing a light-emitting element according to an exemplary embodiment. [Figure 14B] Figures 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B and 14B are schematic cross-sectional views taken along the cut line A-A' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A, respectively. [Figure 14C] Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C and 14C are schematic cross-sectional views taken along the cut line B-B' in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A and 14A. [Figure 15] 15A, 15B, 15C and 15D are schematic cross-sectional views for explaining a method for forming a bonding metal layer according to an embodiment. [Figure 16] 16A and 16B are cross-sectional views illustrating various embodiments of the bonding metal layer. [Figure 17A] FIG. 17A is a schematic plan view illustrating a display device according to an embodiment. [Figure 17B] FIG. 17B is a schematic cross-sectional view taken along the cut line CC' of FIG. 17A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples to fully convey the concept of the present disclosure to those skilled in the art to which the present disclosure pertains. Therefore, the present disclosure is not limited to the embodiments described below, and may be embodied in other forms. In addition, in the drawings, the width, length, thickness, and the like of components may be exaggerated for convenience. In addition, when a component is described as being "on" or "above" another component, this includes not only the case where each part is "directly above" or "directly on" the other part, but also the case where another component is interposed between each component and the other component. The same reference numerals refer to the same components throughout the specification.

[0013] In an illustrative embodiment, a light-emitting element is provided, the light-emitting element including: a first light-emitting stack; a second light-emitting stack disposed below the first light-emitting stack; a third light-emitting stack disposed below the second light-emitting stack; first to fourth connecting electrodes disposed on top of the first light-emitting stack and electrically connected to the first to third light-emitting stacks; and a bonding metal layer disposed on upper surfaces of the first to fourth connecting electrodes, each of the first to fourth connecting electrodes including a groove on its upper surface, and the bonding metal layer covering the groove of each of the first to fourth connecting electrodes.

[0014] By providing a light emitting device having a structure in which the first to third light emitting stacks are laminated, the mounting process time can be shortened. Furthermore, by adopting a bonding metal layer together with a connecting electrode, a light emitting device suitable for probing and mounting for electrical measurement can be provided.

[0015] The light emitting device may further include a barrier layer disposed between the bonding metal layer and the connecting electrode.

[0016] In one embodiment, the bonding metal layer may at least partially cover the groove on the upper surface of the connecting electrode as well as the surrounding area of ​​the groove.

[0017] The connecting electrode may include Cu, and the bonding metal layer may include Au.

[0018] The first light-emitting stack may be electrically connected to the first connecting electrode and the fourth connecting electrode, the second light-emitting stack may be electrically connected to the second connecting electrode and the fourth connecting electrode, and the third light-emitting stack may be electrically connected to the third connecting electrode and the fourth connecting electrode.

[0019] This allows the first to third light-emitting stacks to be driven independently of each other.

[0020] In one embodiment, the first to third connecting electrodes can be electrically connected to the second conductive type semiconductor layers of the first to third light-emitting stacks, respectively, and the fourth connecting electrode can be electrically connected to the first conductive type semiconductor layers of the first to third light-emitting stacks.

[0021] In an embodiment, the first to fourth connecting electrodes may be disposed in an upper region of the first conductive type semiconductor layer of the third light emitting stack.

[0022] The light emitting element may further include a first pad electrically connecting the first connecting electrode to the first light emitting stack, a second pad electrically connecting the second connecting electrode to the second light emitting stack, a third pad electrically connecting the third connecting electrode to the third light emitting stack, and a fourth pad electrically connecting the fourth connecting electrode to the first to third light emitting stacks. By adopting the first to fourth pads, electrical connections between the first to third light emitting stacks and the first to fourth connecting electrodes can be easily implemented.

[0023] The light-emitting element may further include a first lower contact electrode in contact with the second conductive type semiconductor layer of the first light-emitting stack; a second lower contact electrode in contact with the second conductive type semiconductor layer of the second light-emitting stack; and a third lower contact electrode in contact with the second conductive type semiconductor layer of the third light-emitting stack, and the first to third pads may be connected to the first to third lower contact electrodes, respectively.

[0024] By adopting the first to third lower contact electrodes, the current can be uniformly distributed to the first to third light-emitting stacks.

[0025] The light emitting device may further include a first upper contact electrode in ohmic contact with the first conductive type semiconductor layer of the first light emitting stack. The first conductive type semiconductor layer of the first light emitting stack may have a recessed region, and the first upper contact electrode may cover the recessed region.

[0026] In one embodiment, the fourth pad may be connected to the first upper contact electrode.

[0027] In an exemplary embodiment, a display device is provided, the display device including a display substrate having bonding pads, and a light-emitting element disposed on the display substrate, the light-emitting element including a first light-emitting stack; a second light-emitting stack disposed below the first light-emitting stack; a third light-emitting stack disposed below the second light-emitting stack; first to fourth connecting electrodes disposed above the first light-emitting stack and electrically connected to the first to third light-emitting stacks; and a bonding metal layer disposed on upper surfaces of the first to fourth connecting electrodes, the first to fourth connecting electrodes each including a groove on an upper surface, the bonding metal layer covering the grooves of the first to fourth connecting electrodes, respectively, and the bonding metal layer being eutectic bonded to the bonding pad.

[0028] In one embodiment, the eutectic bond can be a Au and In or Au and Sn eutectic bond.

[0029] In one embodiment, the connecting electrode may include Cu, and the bonding metal layer may include Au.

[0030] The light emitting device may further include a barrier layer disposed between the bonding metal layer and the connecting electrode.

[0031] In one embodiment, the bonding metal layer may at least partially cover the groove on the upper surface of the connecting electrode as well as the surrounding area of ​​the groove.

[0032] In one embodiment, the first light-emitting stack may be electrically connected to the first connecting electrode and the fourth connecting electrode, the second light-emitting stack may be electrically connected to the second connecting electrode and the fourth connecting electrode, and the third light-emitting stack may be electrically connected to the third connecting electrode and the fourth connecting electrode.

[0033] The first to third connecting electrodes may be electrically connected to the second conductive type semiconductor layers of the first to third light-emitting stacks, respectively, and the fourth connecting electrode may be electrically connected to the first conductive type semiconductor layers of the first to third light-emitting stacks.

[0034] In one embodiment, the first to fourth connecting electrodes may be disposed in an upper region of the first conductive type semiconductor layer of the third light-emitting stack.

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

[0036] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Hereinafter, the light emitting device may include a micro-LED, which, as known in the art, has a light emitting area of ​​10,000 μm 2 In another embodiment, the micro-LED is 4000 μm 2 Below that, another 2500μm 2 It can have the following light emitting area:

[0037] FIG. 1A is a schematic plan view of a light-emitting device according to one embodiment, and FIGS. 1B and 1C are schematic cross-sectional views taken along lines AA' and BB' in FIG. 1A, respectively.

[0038] Referring to Figures 1A, 1B and 1C, the light-emitting element 100 includes an emission 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 emission stack structure, and bonding metal layers 20cp, 30cp, 40cp, and 50cp are disposed on each connecting electrode.

[0039] The light-emitting device 100 may include a first LED subunit, a second LED subunit, and a third LED subunit disposed on a substrate 11. 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 is illustrated with 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, the light-emitting device 100 is described by taking as an example that it includes three light-emitting stacks 20, 30, and 40 according to one embodiment.

[0040] The substrate 11 may include a light-transmitting insulating material to transmit light. However, in some embodiments, the substrate 11 may be semi-transparent or partially transparent to transmit only light of a specific wavelength or transmit only a portion 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, such as 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 an uneven surface on the top surface, such as a patterned sapphire substrate. The inclusion of texture on the top surface can increase the extraction efficiency of light generated by the third light-emitting stack 40 adjacent to the substrate 11. The texture on the substrate 11 can be employed to selectively increase the luminosity of the third light-emitting stack 40 relative to the first light-emitting stack 20 and the second light-emitting stack 30. However, in alternative embodiments, the substrate 11 can be omitted.

[0041] The first, second and third light emitting stacks 20, 30, 40 are configured to emit light towards 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 further away from the substrate 11 can emit light with longer wavelengths than the light emitting stacks closer to the substrate 11, thereby reducing light loss. For example, the first light emitting stack 20 can emit red light, the second light emitting stack 30 can emit green light, and the third light emitting stack 40 can emit blue light.

[0042] In another embodiment, the second light-emitting stack 30 can emit light with a shorter wavelength 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 luminance of the second light-emitting stack 30 and increase the luminance of the third light-emitting stack 40, thereby dramatically changing the luminance ratio of the light emitted from the first, second and third light-emitting stacks. For example, the first light-emitting stack 20 can be configured to emit red light, the second light-emitting stack 30 can emit blue light, and the third light-emitting stack 40 can emit green light. This can relatively reduce the luminance of the blue light and relatively increase the luminance of the green light, thereby easily adjusting the luminance ratio of the red, green and blue colors to be close to 3:6:1. Furthermore, the light-emitting areas of the first, second and third light-emitting stacks 20, 30, 40 can be approximately 10,000 μm 2 It can be less than 4000μm 2 , and even 2500 μm 2 Also, the light-emitting area can be made larger so as to be 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.

[0043] In the following, an example will be described in which the second light-emitting stack 30 emits light with a shorter wavelength than the third light-emitting stack 40, e.g., blue light, but it should be noted that the second light-emitting stack 30 can also emit light with a longer wavelength than the third light-emitting stack 40, e.g., green light.

[0044] First light emitting stack 20 includes a first conductivity type semiconductor layer 21, an active layer 23, and a second conductivity type semiconductor layer 25. According to one embodiment, first light emitting stack 20 may include red light emitting semiconductor materials such as, but not limited to, AlGaAs, GaAsP, AlGaInP, and GaP.

[0045] 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 alloys thereof, such as Au-Te alloy or 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 downward toward the substrate 11.

[0046] 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 is not limited to, GaN, InGaN, ZnSe, etc. A second bottom contact electrode 35p is disposed under the second conductive type semiconductor layer 35 of the second light-emitting stack 30.

[0047] The third light-emitting stack 40 includes a first conductivity type semiconductor layer 41, an active layer 43, and a second conductivity 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. A third bottom contact electrode 45p is disposed on the second conductivity type semiconductor layer 45 of the third light-emitting stack 40.

[0048] 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, 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.

[0049] Each of the first, second and third bottom contact electrodes 25p, 35p and 45p may include a transparent conductive material that transmits light. For example, the bottom contact electrodes 25p, 35p and 45 may include a transparent conductive oxide (TCO), such as, but not limited to, SnO, InO2, ZnO, ITO, ITZO, etc.

[0050] 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 include a non-conductive material that transmits light. For example, the first and second adhesive layers 61, 63 may include an optically clear adhesive (OCA), which may include, but is not limited to, epoxy, polyimide, SU8, spin-on-glass (SOG), and benzocyclobutene (BCB).

[0051] According to the illustrated embodiment, the first insulating layer 81, the second insulating layer 83, and the third insulating layer 85 are disposed on at least a portion of the side surfaces of the first, second, and third light emitting stacks 20, 30, 40. At least one of the first to third insulating layers 81, 83, 85 can include various organic or inorganic insulating materials, such as polyimide, SiO2, SiNx, Al2O3, and the like. For example, at least one of the first to third insulating layers 81, 83, 85 can include a distributed Bragg reflector (DBR). As another example, at least one of the first to third insulating layers 81, 83, 85 can include a black organic polymer. In some embodiments, an electrically floating metal reflective layer can be disposed on the first to third insulating layers 81, 83, 85 to reflect light emitted from the light emitting stacks 20, 30, 40 toward the substrate 11. In some embodiments, at least one of the first to third insulating layers 81, 83, and 85 may have a single layer structure or a multi-layer structure formed of two or more insulating layers having different refractive indices.

[0052] According to an embodiment, each of the first, second and third light-emitting stacks 20, 30 and 40 can be driven independently. More specifically, a common voltage can be applied to one of the first and second conductive type semiconductor layers of each light-emitting stack, and an individual light-emitting signal can be applied to another 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 can be n-type, and the second conductive type semiconductor layers 25, 35 and 45 can be p-type. In this case, the third light-emitting stack 40 can have a reverse stacking sequence compared to the first light-emitting stack 20 and the second light-emitting stack 30, whereby the p-type semiconductor layer 45 can be disposed on the top of the active layer 43 to simplify the manufacturing process. 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 can be reversed.

[0053] The first, second and third lower contact electrodes 25p, 35p, 45p connected to the p-type semiconductor layers 25, 35, 45 of the light emitting stacks, respectively, 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 the light emitting stacks can be commonly and electrically connected to the fourth connecting electrode 50ce. As a result, the light emitting device 100 can 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 can be driven independently of each other. Since the light emitting device 100 has a common n-type light emitting stack structure, the voltage sources applied to the first, second and third light emitting stacks 20, 30, 40 can be changed from one another.

[0054] 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. Also, 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 one embodiment of the present disclosure will be described with reference to a common n-type light emitting stack structure.

[0055] According to the illustrated embodiment, the light emitting element 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 and second insulating layers 81 and 83. The first connecting electrode 20ce is electrically connected to the first pad 20pd through a first through hole 20ct defined through the third insulating layer 85. The second pad 30pd is electrically connected to the second lower contact electrode 35p through a second contact hole 30CH defined through the first and second insulating layers 81 and 83. 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.

[0056] The third pad 40pd is electrically connected to the third lower contact electrode 45p through a third contact hole 40CH defined through the first and second insulating layers 81 and 83. The third connecting electrode 40ce is electrically connected to the third pad 40pd through 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, and 41 of the first, second, and third light-emitting stacks 20, 30, and 40 through 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, and 41 of the first, second, and third light-emitting stacks 20, 30, and 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.

[0057] In this embodiment, the connecting electrodes 20ce, 30ce, 40ce, and 50ce are illustrated and described as being in direct contact with the pads 20pd, 30pd, 40pd, and 50pd, respectively, but the connecting electrodes 20ce, 30ce, 40ce, and 50ce may not be directly connected to the pads 20pd, 30pd, 40pd, and 50pd, and another connector may be interposed between them.

[0058] The first, second, third and fourth pads 20pd, 30pd, 40pd, 50pd are separated and insulated from each other. According to an embodiment, the first, second, third and fourth pads 20pd, 30pd, 40pd, 50pd may cover at least a portion of the side surface of the first, second and third light emitting stacks 20, 30, 40, respectively. This facilitates dissipation of heat generated from the first, second and third light emitting stacks 20, 30 and 40.

[0059] 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, but are not limited to, metals such as Cu, Ni, Ti, Sb, Zn, Mo, Co, Sn, Ag, or alloys thereof. For example, each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may include two or more metals or a plurality of different metal layers to reduce stress from the elongated shapes of the connecting electrodes 20ce, 30ce, 40ce, and 50ce. The connecting electrodes 20ce, 30ce, 40ce, and 50ce may be formed of Cu, which is advantageous in terms of deposition using plating and cost. Cu forms a natural oxide film, but the natural oxide film can be removed by the flux in the solder paste in a surface mounting technology using a solder paste. However, the surface mounting technique using solder paste is not suitable for mounting the light emitting element 100 because electrical shorts may occur between the solder pastes when the spacing between the connecting electrodes 20ce, 30ce, 40ce, and 50ce is approximately 50 μm or less.

[0060] Eutectic bonding technology can be used to bond extremely small light-emitting elements such as micro LEDs. However, the native oxide film on Cu can interfere with eutectic bonding and lead to bonding failure.

[0061] Thus, in an exemplary embodiment, bonding metal layers 20cp, 30cp, 40cp, and 50cp are disposed on the connecting electrodes 20ce, 30ce, 40ce, and 50ce, respectively. The connecting electrodes 20ce, 30ce, 40ce, and 50ce may have recessed regions on their upper surfaces, and the bonding metal layers 20cp, 30cp, 40cp, and 50cp may be disposed within the recessed regions of the connecting electrodes 20ce, 30ce, 40ce, and 50ce, respectively, and may protrude outward.

[0062] The bonding metal layers 20cp, 30cp, 40cp, and 50cp are electrically connected to the connecting electrodes 20ce, 30ce, 40ce, and 50ce, respectively, and may be formed of a metal layer, for example, Au, which may be bonded to a circuit board through eutectic bonding. In this case, the pads arranged on the circuit board may include, for example, In or Sn. It may be considered to form the bonding metal layers 20cp, 30cp, 40cp, and 50cp with In or Sn, but there is a problem that In is difficult to deposit thickly through plating technology, and Sn is difficult to probe for measuring the electrical characteristics of the light emitting element 100. Therefore, by forming the bonding metal layers 20cp, 30cp, 40cp, and 50cp with Au, a bonding metal layer of sufficient thickness can be formed, and the electrical characteristics of the light emitting element 100 can be easily measured.

[0063] Meanwhile, although not shown, a barrier layer may be interposed between the connecting electrodes 20ce, 30ce, 40ce, 50ce and the bonding metal layers 20cp, 30cp, 40cp, 50cp. The barrier layer prevents the bonding metal layers 20cp, 30cp, 40cp, 50cp from mixing with the connecting electrodes 20ce, 30ce, 40ce, 50ce. This will be described later.

[0064] According to one embodiment, light emitting device 100, as known in the art, has a surface area of ​​approximately 10,000 μm 2 or less than about 4,000 μm in another embodiment. 2 Or 2,500μm 2In the case of a micro LED having a diameter of less than 100 mm, the connecting electrodes 20ce, 30ce, 40ce, 50ce may overlap at least one part of the first, second, and third light emitting stacks 20, 30, 40 as shown in the figure. More specifically, the connecting electrodes 20ce, 30ce, 40ce, and 50ce may overlap at least one step formed on the side of the light emitting stack structure. In this manner, since the area of ​​the lower surface of the connecting electrode is larger than that of the upper surface, a larger contact area may be formed between the connecting electrodes 20ce, 30ce, 40ce, 50ce and the light emitting stack structure. As a result, the connecting electrodes 20ce, 30ce, 40ce, 50ce may be more stably formed on the light emitting stack structure, and heat generated in the light emitting stack structure may be more efficiently dissipated to the outside.

[0065] In some exemplary embodiments, at least one of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may overlap a side surface of each of the light emitting stacks 20, 30, and 40, so that the light emitting stacks 20, 30, and 40 can efficiently dissipate heat generated inside to the outside. Also, if the connecting electrodes 20ce, 30ce, 40ce, and 50ce include a reflective material such as a metal, the connecting electrodes 20ce, 30ce, 40ce, and 50ce can reflect light emitted from at least one or more of the light emitting stacks 20, 30, and 40, so that light efficiency can be improved.

[0066] 2 is a schematic cross-sectional view of a light-emitting stack structure according to an embodiment of the present disclosure. The light-emitting device 100 described above is formed by processing the light-emitting stack structure.

[0067] 2, the light emitting stack structure includes a substrate 11, a first light emitting stack 20, a second light emitting stack 30 and a third light emitting stack 40. Also, bottom contact electrodes 25p, 35p, 45p may be disposed on the second conductive type semiconductor layers 25, 35, 45 of the light emitting stacks 20, 30, 40, respectively.

[0068] 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 bottom contact electrode 45p may be formed on the second conductive 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, ITZO, etc. 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 bottom 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 bottom contact electrode comprising a transparent conductive oxide (TCO) may be formed on the second conductive type semiconductor layer by, for example, physical vapor deposition or chemical vapor deposition, respectively.

[0069] In one embodiment, the first light-emitting stack 20 can be attached to the second light-emitting stack 30 through a first adhesive layer 61, and the second light-emitting stack 30 can be attached to the third light-emitting stack 40 through a second adhesive layer 63. For example, after the third light-emitting stack 40 is grown on the substrate 11, the second light-emitting stack 30 grown on a temporary substrate can be attached to the third light-emitting stack 40 through the second adhesive layer 63. The temporary substrate on the second light-emitting stack 30 is then removed. The first light-emitting stack 20, also grown on another temporary substrate, can then be attached onto the second light-emitting stack 30 through the first adhesive layer 61. The temporary substrate on the first light-emitting stack 20 can be removed from the first light-emitting stack 20.

[0070] In another embodiment, the first and second light emitting stacks 20,30 can be bonded to each other via a first adhesive layer 61, and at least one of the temporary substrates of the first and second light emitting stacks 20,30 can be removed by a laser lift-off process, a chemical process, a mechanical process, etc. Then, the first and second light emitting stacks 20,30 can be bonded to a third light emitting stack 40 via a second adhesive layer 63, and the remaining temporary substrates of the first and second light emitting stacks 20,30 can be removed by a laser lift-off process, a chemical process, a mechanical process, etc.

[0071] The first to third light-emitting stacks 20, 30, 40, the first to third bottom contact electrodes 25p, 35p, 45p and the adhesive layers 61, 63 are the same as those described above, and therefore will not be described in detail to avoid duplication.

[0072] A method for manufacturing the light emitting device 100 using the light emitting stack structure of FIG. 2 will be described in detail below.

[0073] 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A, and 14A are schematic plan views for explaining a method for manufacturing a light-emitting device according to an exemplary embodiment. 3B, 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B, and 14B are schematic cross-sectional views taken along the cut line A-A' of the corresponding plan views shown in 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A, and 14A according to an exemplary embodiment. Figures 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C, and 14C are schematic cross-sectional views taken along the cut line B-B' of the corresponding plan views shown in Figures 3A, 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, 13A, and 14A according to exemplary embodiments.

[0074] 3A, 3B and 3C, the first conductive type semiconductor layer 21, the active layer 23 and the second conductive type semiconductor layer 25 are patterned to expose the first lower contact electrode 25p. The first conductive type semiconductor layer 21, the active layer 23 and the second conductive type semiconductor layer 25 can be patterned using a photo and etching process. A photo process can be performed using a first mask, and the first conductive type semiconductor layer 21, the active layer 23 and the second conductive type semiconductor layer 25 can be etched using, for example, a dry etching technique. After patterning, the first light-emitting stack 20 surrounded by the exposed lower contact electrode 25p remains. Here, one first light-emitting stack 20 is illustrated, but the first light-emitting stack 20 can be patterned in each of the light-emitting element regions on the substrate 11.

[0075] The first light-emitting stack 20 may be disposed in the center of the light-emitting element region, but is not limited thereto. The planar shape of the first light-emitting stack 20 may have a shape elongated along one diagonal direction, but is not limited thereto.

[0076] The first bottom contact electrode 25p may be a transparent electrode, and the second conductive type semiconductor layer 25 may be a p-type semiconductor layer. Meanwhile, the first conductive type semiconductor layer 21 is disposed on the top surface of the first light-emitting stack 20, and the first conductive type semiconductor layer 21 may be an n-type semiconductor layer.

[0077] 4A, 4B, and 4C, the first lower contact electrode 25p is patterned so that a part of the first lower contact electrode 25p remains around the first light-emitting stack 20. The first lower contact electrode 25p may be patterned using a second mask. At this time, the first adhesive layer 61 may also be patterned together. This may expose the first conductive type semiconductor layer 31 around the first lower contact electrode 25p.

[0078] 5A, 5B, and 5C, the first conductive type semiconductor layer 31, the active layer 33, and the second conductive type semiconductor layer 35 are patterned to expose the second bottom contact electrode 35p. The first conductive type semiconductor layer 31, the active layer 33, and the second conductive type semiconductor layer 35 can be patterned using a photo and etching process. A photo process can be performed using a third mask, and the first conductive type semiconductor layer 31, the active layer 33, and the second conductive type semiconductor layer 35 can be etched using, for example, a dry etching technique. After patterning, the second light-emitting stack 20 surrounded by the exposed second bottom contact electrode 35p remains.

[0079] 6A, 6B, and 6C, the second lower contact electrode 35p is patterned so that a part of the second lower contact electrode 35p remains around the second light-emitting stack 30. The second lower contact electrode 35p may be patterned using a fourth mask. At this time, the second adhesive layer 63 may also be patterned together. This may expose the third lower contact electrode 45p around the second lower contact electrode 35p.

[0080] 7A, 7B, and 7C, the third lower contact electrode 45p is patterned so that the third lower contact electrode 45p remains around the second lower contact electrode 35p. The third lower contact electrode 45p can be patterned using a fifth mask. Furthermore, the second conductive type semiconductor layer 45 and the active layer 43 can be patterned to expose the first conductive type semiconductor layer 41. For example, the third lower contact electrode 45p can be etched using a wet etching technique, and the second conductive type semiconductor layer 45 and the active layer 43 can be etched using a dry etching technique. This exposes the first conductive type semiconductor layer 41 around the third lower contact electrode 45p.

[0081] According to the illustrated embodiment, the first light-emitting stack 20 has the smallest area among the light-emitting stacks 20, 30, 40. Meanwhile, the third light-emitting stack 40 may have the largest area among the light-emitting stacks 20, 30, 40, thereby relatively increasing the luminous intensity 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.

[0082] 8A, 8B, and 8C, 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. The first conductive type semiconductor layer 21 may be, for example, an n++ GaAs layer, and a portion of an upper surface of the n++ GaAs layer may be recessed through wet etching.

[0083] The first upper contact electrode 21n is formed in a recessed region of the first conductive type semiconductor layer 21. The first upper contact electrode 21n can be formed of, for example, AuGe / Ni / Au / Ti and can be formed to a thickness of, for example, 100 nm / 25 nm / 100 nm / 10 nm. By partially removing the surface of the n++ GaAs layer and making the first upper contact electrode 21n contact the first conductive type semiconductor layer 21 in the recessed region, the ohmic contact characteristics can be improved.

[0084] 9A, 9B and 9C, a first insulating layer 81 is formed covering the light emitting stacks 20, 30, 40. The first insulating layer 81 covers the first upper contact electrode 21n. The first insulating layer 81 can be formed of, for example, SiN, SiO2, Al2O3, etc., to a thickness of about 4000 Å.

[0085] Next, the first insulating layer 81 and the first conductive type semiconductor layer 41 can be patterned to form an isolation region for isolating the light emitting element region. As a result, the upper surface of the substrate 11 can be exposed around the first conductive type semiconductor layer 41.

[0086] Meanwhile, a second insulating layer 83 can be formed on the first insulating layer 81. The second insulating layer 83 can cover the side surfaces of the first conductive type semiconductor layer 41 to protect the first conductive type semiconductor layer 41. The second insulating layer 83 can be formed of SiN, SiO2, Al2O3, or the like.

[0087] 10A, 10B, and 10C, portions of the first and second insulating layers 81, 83 can be removed to form first, second, third, and fourth contact holes 20CH, 30CH, 40CH, and 50CH. The first contact hole 20CH can be defined on the first bottom contact electrode 25p to expose a portion of the first bottom contact electrode 25p. The second contact hole 30CH can be defined on the second bottom contact electrode 35p to expose the second bottom contact electrode 35p. The third contact hole 40CH can be defined on the third bottom contact electrode 45p to expose the third bottom contact electrode 45p.

[0088] The fourth contact hole 50CH provides a passage 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 to 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 to 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 to expose a part of the first conductive type semiconductor layer 41.

[0089] 11A, 11B, and 11C, the first, second, third, and fourth pads 20pd, 30pd, 40pd, and 50pd are formed on the first and second insulating layers 81, 83. 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 front surface of the substrate 11 and patterning the conductive layer using a photo and etching process.

[0090] 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 layer 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 is formed to overlap the region in which the fourth contact hole 50CH is formed, particularly the region in which the first, second and third sub-contact holes 50CHa, 50CHb, 50CHc are formed, and can be electrically connected to the first conductive type semiconductor layers 21, 31, 41 of the first to third light-emitting stacks 20, 30, 40.

[0091] The first to fourth pads 20pd, 30pd, 40pd, 50pd may contain Au and may be formed, for example, in a layered structure of Ti / Ni / Ti / Ni / Ti / Ni / Au / Ti, and may be formed to have thicknesses of, for example, approximately 100 nm / 50 nm / 100 nm / 50 nm / 100 nm / 50 nm / 3000 nm / 10 nm.

[0092] 12A, 12B, and 12C, a third insulating layer 85 may be formed on the second insulating layer 83. The third insulating layer 85 may be formed of SiNx, SiO2, Al2O3, or the like.

[0093] Next, the third insulating layer 85 may be patterned to form the first, second, third and fourth through holes 20ct, 30ct, 40ct and 50ct that expose the first to fourth pads 20pd, 30pd, 40pd, 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] 13A, 13B, and 13C, the first, second, third, and fourth connecting electrodes 20ce, 30ce, 40ce, and 50ce are formed on the third insulating layer 85 in which the first, second, third, and fourth through holes 20ct, 30ct, 40ct, and 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 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 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 connected to the third pad 40pd through the third through hole 40ct. The fourth connection 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 through 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, spaced apart from one another. The first, second, third and fourth connecting electrodes 20ce, 30ce, 40ce, 50ce may be electrically connected to the first, second, third and fourth pads 20pd, 30pd, 40pd, 50pd, respectively, to 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 one embodiment of the present disclosure, a seed layer may be deposited on a conductive surface of the light emitting stack structure, and a photoresist pattern may be formed to expose the seed layer at a position where the connecting electrodes are to be formed. According to one embodiment, the seed layer may be deposited to a thickness of about 1000 Å, but is not limited thereto. The seed layer may be formed of, for example, Ti / Cu. Then, the seed layer may be plated with a metal such as Cu, Ni, Ti, Sb, Zn, Mo, Co, Sn, Ag or an alloy thereof. Cu is particularly easy to plate and economical.

[0098] Meanwhile, after plating is completed, a polishing process may be performed to planarize the upper surface of the connection electrode, and then the photoresist pattern and the seed layer remaining between the connection electrodes may be removed.

[0099] According to the illustrated exemplary embodiment, each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may have a substantially elongated shape as it gets farther from the substrate 11. In another exemplary embodiment, 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.

[0100] 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 electrodes may have a larger width than the upper surface, providing a larger contact area between the connecting electrodes 20ce, 30ce, 40ce, and 50ce and the light emitting stack structure, and thus the light emitting device 100 may have a more stable structure capable of withstanding subsequent processes.

[0101] 14A, 14B, and 14C, the bonding metal layers 20cp, 30cp, 40cp, and 50cp are formed on the connecting electrodes 20ce, 30ce, 40ce, and 50ce. The upper surfaces of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may be partially etched away, and the bonding metal layers 20cp, 30cp, 40cp, and 50cp may be formed in the recessed regions.

[0102] The connecting electrodes 20ce, 30ce, 40ce, and 50ce may not be suitable for bonding because they are made of a metal that is suitable for plating. Furthermore, a natural oxide layer may be formed on the upper surface of the connecting electrodes 20ce, 30ce, 40ce, and 50ce, causing poor contact. Therefore, by partially removing the upper surface of the connecting electrodes 20ce, 30ce, 40ce, and 50ce, the natural oxide film can be removed, and by adopting the bonding metal layers 20cp, 30cp, 40cp, and 50cp, the light emitting element 100 can be easily mounted on the circuit board using eutectic bonding technology. The process of forming the bonding metal layers 20cp, 30cp, 40cp, and 50cp will be described in detail with reference to FIGS. 15A to 15D.

[0103] Meanwhile, the substrate 11 is separated into light emitting element regions to complete the light emitting element 100. The substrate 11 can be separated using a laser scribing technique. In another embodiment, the substrate 11 may be removed from the third light emitting stack 40.

[0104] 15A, 15B, 15C, and 15D are schematic cross-sectional views for explaining a method for forming a bonding metal layer according to an embodiment. Here, a method for forming a bonding metal layer 30cp on a connecting electrode 30ce will be explained as an example.

[0105] 15A, a connecting electrode 30ce is formed by plating using a photoresist pattern. The connecting electrode 30ce formed by plating may have a rough surface as shown in the figure. While forming the connecting electrode 30ce by plating, other connecting electrodes 20ce, 40ce, and 50ce may also be formed at the same time.

[0106] 15B, the surface of the connecting electrode 30ce may be polished to flatten its upper surface. While polishing the surface of the connecting electrode 30ce, the surfaces of the connecting electrodes 20ce, 40ce, and 50ce may also be polished together.

[0107] Referring to FIG. 15C, the surface of the connecting electrode 30ce is etched to form a groove 30g. A natural oxide film may be formed on the surface of the connecting electrode 30ce, and an etching process may be performed to remove the natural oxide film and contaminants. For example, a photoresist pattern is formed to cover the edge of the connecting electrode 30ce, and the upper surface of the connecting electrode 30ce is etched. When the connecting electrode 30ce is made of Cu, the connecting electrode 30ce may be wet-etched using a mixed solution of sulfuric acid, phosphoric acid and hydrogen peroxide, hydrochloric acid, ammonium persulfate, potassium chloride, phosphoric acid and hydrogen peroxide, or the like. This can remove the natural oxide film on the surface of the connecting electrode 30ce, and improve the surface roughness. The groove 30g may be formed to a depth of, for example, 100 nm.

[0108] 15D, the photoresist pattern can be used to form the barrier layer 30cb and the bonding metal layer 30cp, and then the photoresist pattern can be removed, that is, the barrier layer 30cb and the bonding metal layer 30cp can be formed using a lift-off technique.

[0109] The barrier layer 30cb may include a single layer or multiple layers of, for example, Ti, Ni, W, Cr, Co, etc. For example, the barrier layer 30cb may be formed of Ni, Ti, or Ti / Ni.

[0110] The bonding metal layer 30cp can be formed of Au or Au / In. Au is suitable for probing, and is suitable for eutectic bonding with In or Sn.

[0111] Here, a method of forming a bonding metal layer 30cp on a connecting electrode 30ce will be described as an example, but the bonding metal layers 20cp, 40cp, and 50cp can be formed on other connecting electrodes 20ce, 40ce, and 50ce in the same manner, and the bonding metal layers 20cp, 30cp, 40cp, and 50cp can also be formed together in the same process.

[0112] 16A and 16B are cross-sectional views illustrating various embodiments of the bonding metal layer.

[0113] 16A, in one embodiment, the bonding metal layer 130cp may cover the entire upper surface of the connecting electrode 30ce. The barrier layer 130cb may cover the entire upper surface of the connecting electrode 30ce, and the bonding metal layer 30cp may be disposed on the barrier layer 130cb. That is, the barrier layer 130cb may cover the upper surface of the connecting electrode 30ce outside the groove 30g as well as inside the groove 30g.

[0114] For example, a first photoresist pattern is used to expose a portion of the upper surface of the connecting electrode 30ce, and then a wet etching technique is used to form the groove 30g. The first photoresist pattern is then removed, and the entire upper surface of the connecting electrode 30ce is exposed using a second photoresist pattern. Then, the barrier layer 130cb and the bonding metal layer 130cp can be formed using the second photoresist pattern.

[0115] 16B, in one embodiment, the barrier layer 230cb and the bonding metal layer 230cp may cover the groove 30g of the connecting electrode 30ce and may further partially cover the upper surface of the connecting electrode 30ce around the groove 30g, so that the edge of the upper surface of the connecting electrode 30ce may be exposed to the outside.

[0116] For example, a first photoresist pattern is used to expose a portion of the upper surface of the connecting electrode 30ce, and then a wet etching technique is used to form the groove 30g. The first photoresist pattern is then removed, and a second photoresist pattern is used to expose a portion of the upper surface of the connecting electrode 30ce, including the groove 30g. Thereafter, the barrier layer 230cb and the bonding metal layer 230cp can be formed using the second photoresist pattern.

[0117] Although various embodiments of the bonding metal layer 30cp are described, the method of forming the bonding metal layer 30cp may vary and is not limited to the embodiments described above.

[0118] FIG. 17A is a schematic plan view illustrating a display device 1000 according to an embodiment, and FIG. 17B is a schematic cross-sectional view taken along the line CC' in FIG. 17A.

[0119] 17A and 17B, a display device 1000 may include a display substrate 200 and a light emitting element 100. The light emitting element 100 may be mounted on the display substrate 200 in an end device such as a display device. The light emitting elements 100 may be mounted on the display substrate 200 individually or in groups. The light emitting elements 100 may then be packaged in groups such that multiple packages are mounted on the display substrate 200.

[0120] The display substrate 200 may include bonding pads 210 for mounting the light emitting elements 100. The bonding pads 210 may be formed of a metal layer containing, for example, In or Sn.

[0121] The metal bonding layers 20cp, 30cp, 40cp, and 50cp are bonded onto the bonding pads 210, thereby mounting the light emitting device 100 on the display substrate 200. The bonding pads 210 and the metal bonding layers 20cp, 30cp, 40cp, and 50cp can be attached to each other through eutectic bonding.

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

Claims

1. a first luminescent stack; a second light emitting stack disposed below the first light emitting stack; a third light emitting stack disposed below the second light emitting stack; first to fourth connection electrodes disposed on the first light emitting stack and electrically connected to the first to third light emitting stacks; and a bonding metal layer disposed on an upper surface of the first to fourth connecting electrodes; each of the first to fourth connection electrodes includes a groove on an upper surface thereof; the bonding metal layer covers the grooves of the first to fourth connection electrodes, respectively; Each of the connecting electrodes overlaps at least one step formed on a side of a light emitting stack structure including a first light emitting stack, a second light emitting stack, and a third light emitting stack.

2. The light emitting device of claim 1 , further comprising a barrier layer disposed between the bonding metal layer and the connecting electrode.

3. The light emitting device according to claim 1 , wherein the bonding metal layer at least partially covers the upper surface of the connecting electrode around the groove together with the groove on the upper surface of the connecting electrode.

4. The light emitting device of claim 1 , wherein the connecting electrode comprises Cu and the bonding metal layer comprises Au.

5. the first light-emitting stack is electrically coupled to the first connecting electrode and a fourth connecting electrode; the second light-emitting stack is electrically coupled to the second connecting electrode and a fourth connecting electrode; The light emitting device of claim 1 , wherein the third light emitting stack is electrically coupled to the third connecting electrode and the fourth connecting electrode.

6. the first to third connection electrodes are electrically connected to second conductive type semiconductor layers of the first to third light emitting stacks, respectively; The light emitting device of claim 5, wherein the fourth connection electrode is electrically connected to the first conductive type semiconductor layers of the first to third light emitting stacks.

7. The light emitting device according to claim 6, wherein the first to fourth connecting electrodes are disposed in an upper region of the first conductive type semiconductor layer of the third light emitting stack.

8. a first pad electrically connecting the first connecting electrode to the first light emitting stack; a second pad electrically connecting the second connecting electrode to the second light emitting stack; a third pad electrically connecting the third connecting electrode to the third light emitting stack; and The light emitting device of claim 6, further comprising a fourth pad electrically connecting the fourth connecting electrode to the first to third light emitting stacks.

9. a first bottom contact electrode contacting the second conductivity type semiconductor layer of the first light emitting stack; a second bottom contact electrode contacting the second conductivity type semiconductor layer of the second light emitting stack; and a third bottom contact electrode contacting the second conductivity type semiconductor layer of the third light emitting stack; 9. The light-emitting element according to claim 8, wherein the first to third pads are connected to the first to third lower contact electrodes, respectively.

10. a first upper contact electrode in ohmic contact with the first conductivity type semiconductor layer of the first light emitting stack; the first conductivity type semiconductor layer of the first light emitting stack has a recessed region; The light emitting device of claim 9 , wherein the first top contact electrode covers the recessed region.

11. The light-emitting element according to claim 10 , wherein the fourth pad is connected to the first upper contact electrode.

12. The light-emitting element of claim 2, wherein the barrier layer is formed of one or more of Ni, W, Cr, Co and a Ti / Ni alloy.

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