Method for transferring light-emitting element for display and display device

Abstract

According to one embodiment, a method for transferring a light-emitting element includes the following steps: preparing a wafer having a substrate, a semiconductor layer arranged on the substrate, and raised pads arranged on the upper part of the semiconductor layer and neatly arranged in a plurality of light-emitting element regions; dividing the wafer into a plurality of light-emitting elements, wherein the light-emitting elements maintain a positional relationship of contact with each other; attaching the light-emitting elements to a transfer tape on a supporting substrate in such a manner that the substrate side faces the transfer tape while maintaining the positional relationship of the light-emitting elements; preparing a circuit substrate with neatly arranged pads; tightly attaching the supporting substrate to the circuit substrate in such a manner that raised pads on a portion of the plurality of light-emitting elements contact pads on the circuit substrate; heating the raised pads and pads to bond the portion of the light-emitting elements to the pads; and separating the light-emitting elements bonded to the pads from the transfer tape.

Description

Technical Field

[0001] The present invention relates to a method for transferring a display light-emitting element and a display device, and in particular to a method for transferring a plurality of display light-emitting elements and a display device having the light-emitting elements transferred to a circuit substrate. Background Art

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

[0003] In addition, conventional light emitting diodes are mainly used as backlight sources in display devices. However, recently, LED displays that directly display images using light emitting diodes are being developed.

[0004] Display devices generally use a mixture of blue, green and red to achieve various hues. In order to achieve various images, the display device includes a plurality of pixels, each of which is equipped with blue, green and red sub-pixels, and the hue of a specific pixel is determined by the hue of these sub-pixels, and an image is presented by a combination of these pixels.

[0005] LEDs can emit light of various hues depending on their materials, so individual LED chips emitting blue, green, and red light can be arranged on a two-dimensional plane to provide a display device. To this end, multiple LED chips should be transferred to a display panel substrate at pixel intervals.

[0006] Typically, multiple LED chips are manufactured on a wafer, and these LED chips are divided into individual LED chips on the wafer through scribing and splitting processes. After the splitting process, the intervals between the LED chips are increased by expanding the tape, and such LED chips are rearranged on the transfer tape, and the rearranged LED chips are transferred to the panel substrate using the transfer tape. Since the number of pixels used in the display device is very large, the LED chips rearranged on the transfer tape are collectively transferred to the panel substrate. However, when rearranging the LED chips on the transfer tape, they cannot be collectively transferred from the wafer, and the LED chips need to be arranged individually, so the rearrangement process consumes a lot of time.

[0007] Furthermore, since the LED chips must be arranged in each sub-pixel, a large number of LED chips need to be mounted, which in turn requires more time for the mounting process.

[0008] In addition, since the sub-pixels are arranged on a two-dimensional plane, the area occupied by a pixel including blue, green and red sub-pixels becomes relatively large. Therefore, in order to arrange the sub-pixels within a 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, thereby reducing the light-emitting area. Summary of the invention

[0009] Technical issues

[0010] The technical problem to be solved by the present disclosure is to provide a light emitting element transfer method and a display device capable of shortening the mounting process time.

[0011] Another technical problem to be solved by the present disclosure is to provide a light emitting element transfer method and a display device that can easily transfer the light emitting elements manufactured on a wafer collectively to a circuit substrate.

[0012] Another technical problem to be solved by the present disclosure is to provide a method for transferring a light-emitting element for display and a display device that can increase the area of ​​each sub-pixel within a limited pixel area.

[0013] Technical Solution

[0014] According to an embodiment of the present disclosure, a method for transferring a light-emitting element includes the following steps: preparing a wafer having a substrate, a semiconductor layer arranged on the substrate, and raised pads arranged on the upper part of the semiconductor layer and neatly arranged in a plurality of light-emitting element regions; dividing the wafer into a plurality of light-emitting elements, wherein the light-emitting elements maintain a positional relationship of contact with each other; attaching the light-emitting elements to a transfer tape on a supporting substrate in such a manner that the substrate side faces the transfer tape while maintaining the positional relationship of the light-emitting elements; preparing a circuit substrate with neatly arranged pads; tightly attaching the supporting substrate to the circuit substrate in such a manner that raised pads on a portion of the plurality of light-emitting elements contact pads on the circuit substrate; heating the raised pads and pads to bond the portion of the light-emitting elements to the pads; and separating the light-emitting elements bonded to the pads from the transfer tape.

[0015] According to an embodiment of the present disclosure, a display device includes: a circuit substrate having a pad on its upper surface; and a plurality of light-emitting elements neatly arranged on the circuit substrate, wherein the plurality of light-emitting elements respectively include: a first LED stack; a second LED stack located on the first LED stack; a third LED stack located on the second LED stack; a substrate located on the third LED stack; a raised pad located between the first LED stack and the circuit substrate, wherein the raised pad is bonded to the pad, and the raised pad is bonded to the pad via In, Pb, AuSn or CuSn. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic perspective view for explaining a display device according to an embodiment of the present disclosure.

[0017] Figure 2 is a schematic plan view for explaining a display panel according to an embodiment of the present disclosure.

[0018] Figure 3a 1 is a schematic plan view for explaining a light emitting element according to an embodiment of the present disclosure.

[0019] Figure 3b , Figure 3c and Figure 3d Along Figure 3a Schematic cross-sectional views taken along the lines AA', BB' and CC'.

[0020] Figure 4a , Figure 4b and Figure 4c Schematic cross-sectional views for illustrating first to third LED stacks mounted on a growth substrate according to an embodiment of the present disclosure.

[0021] Figure 5a , Figure 5b , Figure 5c , Figure 5d , Figure 6a , Figure 6b , Figure 6c , Figure 6d , Figure 7a , Figure 7b , Figure 7c , Figure 7d , Figure 8a , Figure 8b , Figure 8c , Figure 8d , Figure 9a , Figure 9b , Fig.9c , Figure 9d , Fig.10a , Fig.10b , Fig.10c , Fig.10d , Fig.11a , Fig.11b , Fig.11c , Fig.11d , Fig.12a , Figure 12b , Fig.12c , Fig.12d , Fig.13a , Fig.13b , Fig.13c and Fig.13dSchematic plan view and cross-sectional view for explaining a method of manufacturing a light-emitting element for display according to an embodiment of the present disclosure.

[0022] Fig.14 This is a schematic cross-sectional view for explaining a light emitting element mounted on a circuit board.

[0023] Fig.15a , Fig.15b , Fig.15c , Fig.15d , Fig.15e , Fig.15f , Figure 15g , Figure 15h and Fig.15i Schematic cross-sectional view for explaining a method of transferring a light emitting element to a circuit substrate according to an embodiment of the present disclosure.

[0024] Fig.16a and Fig.16b is a schematic cross-sectional view for explaining a method of transferring a light emitting element to a circuit substrate according to still another embodiment of the present disclosure.

[0025] Fig.17a and Fig.17b is a schematic cross-sectional view for explaining a method of transferring a light emitting element to a circuit substrate according to still another embodiment of the present disclosure. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to fully convey the idea of ​​the present invention to those skilled in the art, the embodiments described below are provided as examples. Therefore, the present invention is not limited to the embodiments described below, and it may be embodied in other forms. Moreover, in the accompanying drawings, the width, length, thickness, etc. of the constituent elements may be exaggerated for convenience. Moreover, when it is recorded that a certain constituent element is arranged "on the top" or "on" of other constituent elements, it includes not only the situation that each part is "directly" arranged "on the top" or "on" of other parts, but also the situation that another constituent element is inserted between each constituent element and other constituent elements. Throughout the specification, the same figure symbols represent the same constituent elements.

[0027] According to an embodiment of the present disclosure, a method for transferring a light-emitting element includes the following steps: preparing a wafer having a substrate, a semiconductor layer arranged on the substrate, and raised pads arranged on the upper part of the semiconductor layer and neatly arranged in a plurality of light-emitting element regions; dividing the wafer into a plurality of light-emitting elements, wherein the light-emitting elements maintain a positional relationship of contact with each other; attaching the light-emitting elements to a transfer tape on a supporting substrate in such a manner that the substrate side faces the transfer tape while maintaining the positional relationship of the light-emitting elements; preparing a circuit substrate with neatly arranged pads; tightly attaching the supporting substrate to the circuit substrate in such a manner that raised pads on a portion of the plurality of light-emitting elements contact pads on the circuit substrate; heating the raised pads and pads to bond the portion of the light-emitting elements to the pads; and separating the light-emitting elements bonded to the pads from the transfer tape.

[0028] According to the present embodiment, the step of rearranging a plurality of light emitting elements formed in a wafer can be omitted and transferred to a circuit board, thereby shortening the mounting process time.

[0029] In one embodiment, the step of dividing the wafer into a plurality of light emitting elements may include the following steps: forming a scribe line on the wafer by laser scribing; and dividing the wafer along the scribe line on a splitting tape.

[0030] Furthermore, the step of attaching the light-emitting element to the transfer tape on the supporting substrate may include the following steps: transferring the light-emitting element attached to the split tape to a temporary substrate while maintaining the positional relationship; transferring the light-emitting element transferred to the temporary substrate to the transfer tape.

[0031] In another embodiment, the step of dividing the wafer into a plurality of light emitting elements can be performed by laser without a splitting process, for example, laser scribing can be performed by using an invisible laser, thereby omitting an additional splitting process.

[0032] In addition, the step of separating the light emitting element bonded to the pad from the transfer tape may be performed at a temperature higher than normal temperature.

[0033] In one embodiment, the step of separating the light emitting element bonded to the pad from the transfer tape may be performed at a bonding temperature for bonding the raised pad to the pad. In another embodiment, the step of separating the light emitting element bonded to the pad from the transfer tape may be performed at a temperature higher than room temperature and lower than the bonding temperature.

[0034] When the light emitting element bonded to the pad is separated from the transfer tape, the adhesive force between the transfer tape and the light emitting element is smaller than the adhesive force between the protruding pad and the pad.

[0035] The transfer tape may have a smaller adhesive force at a bonding temperature for bonding the protruding pad and the pad than at a normal temperature.

[0036] In addition, the intervals between the light emitting elements to be transferred onto the circuit substrate may be greater than the width of at least one light emitting element. Also, the intervals between the light emitting elements to be transferred onto the circuit substrate may be constant.

[0037] The semiconductor layer may include a semiconductor layer of a first LED stack, a semiconductor layer of a second LED stack, and a semiconductor layer of a third LED stack, and the first to third LED stacks may overlap with each other.

[0038] Since the first LED stack to the third LED stack overlap, the number of light-emitting elements mounted on the circuit substrate can be reduced, thereby further shortening the light-emitting element mounting time. Furthermore, by stacking the first LED stack to the third LED stack, the light-emitting area of ​​each sub-pixel can be increased without increasing the pixel area.

[0039] In addition, the second LED stack can be arranged between the first LED stack and the third LED stack, the third LED stack is arranged closer to the substrate than the first LED stack, the first LED stack to the third LED stack each include a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer, the raised pad includes first to third raised pads and a common raised pad, the common raised pad is commonly electrically connected to the first LED stack to the third LED stack, and the first to third raised pads are respectively electrically connected to the first LED stack to the third LED stack.

[0040] In one embodiment, the raised pad may be located on the first LED stack.

[0041] In one embodiment, the first LED stack can emit light of a longer wavelength than the second LED stack, and the second LED stack can emit light of a longer wavelength than the third LED stack. For example, the first LED stack, the second LED stack, and the third LED stack can emit red light, green light, and blue light, respectively. In another embodiment, the first LED stack can emit light of a longer wavelength than the third LED stack, and the second LED stack can emit light of a shorter wavelength than the third LED stack. For example, the first LED stack, the second LED stack, and the third LED stack can emit red light, blue light, and green light, respectively.

[0042] In addition, the light-emitting element further includes: a first transparent electrode, disposed between the first LED stack and the second LED stack, and ohmically contacting the lower surface of the first LED stack; a second transparent electrode, disposed between the first LED stack and the second LED stack, and ohmically contacting the upper surface of the second LED stack; a third transparent electrode, disposed between the second LED stack and the third LED stack, and ohmically contacting the upper surface of the third LED stack; an n-electrode pad, disposed on the first conductive semiconductor layer of the third LED stack; and a lower p-electrode pad, disposed on the third transparent electrode, wherein the upper surface of the n-electrode pad may be located at the same height as the upper surface of the lower p-electrode pad.

[0043] In one embodiment, any one of the first to third transparent electrodes may be formed using a material different from the other transparent electrodes. For example, the first transparent electrode may be formed using ITO (indium-tin-oxide), and the second and third transparent electrodes may be formed using ZnO.

[0044] Furthermore, the first to third transparent electrodes may be in contact with the second conductive semiconductor layer, respectively, and at least one of the first to third transparent electrodes may be recessed from an edge portion of the second conductive semiconductor layer of the first to third LED stacks.

[0045] Furthermore, the common raised pad may be commonly electrically connected to the first conductive semiconductor layer of the first to third LED stacks, and the first to third raised pads may be electrically connected to the second conductive semiconductor layer of the first to third LED stacks, respectively.

[0046] In addition, the light emitting element may further include: a first bonding layer disposed between the second LED stack and the third LED stack; and a second bonding layer disposed between the first LED stack and the second LED stack.

[0047] According to an embodiment of the present disclosure, a display device includes: a circuit substrate having a pad on its upper surface; and a plurality of light-emitting elements neatly arranged on the circuit substrate, wherein the plurality of light-emitting elements respectively include: a first LED stack; a second LED stack located on the first LED stack; a third LED stack located on the second LED stack; a substrate located on the third LED stack; a raised pad located between the first LED stack and the circuit substrate, wherein the raised pad is bonded to the pad, and the raised pad is bonded to the pad via In, Pb, AuSn or CuSn.

[0048] By using In, Pb, AuSn, or CuSn, the light emitting element can be bonded to the circuit substrate at a relatively low temperature.

[0049] Furthermore, the substrate may be a growth substrate of the third LED stack. The substrate may be, for example, a sapphire substrate.

[0050] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0051] Figure 1 is a schematic perspective view for explaining a display device according to an embodiment of the present disclosure.

[0052] The light emitting element of the present disclosure is not particularly limited, but in particular, can be used in a smart watch 1000a, a VR display device such as a virtual reality helmet (VR headset) 1000b, or an AR display device such as an augmented reality glasses 1000c.

[0053] A display panel for displaying images is mounted inside the display device. Figure 2 is a schematic plan view for explaining a display panel according to an embodiment of the present disclosure.

[0054] Reference Figure 2 The display panel includes a circuit substrate 101 and a light emitting element 100 .

[0055] The circuit substrate 101 or panel substrate may include circuits for passive matrix driving or active matrix driving. In one embodiment, the circuit substrate 101 may include wiring and resistors inside. In another embodiment, the circuit substrate 101 may include wiring, transistors and capacitors. The circuit substrate 101 may also have pads on the upper surface for allowing electrical connection to the circuits arranged inside.

[0056] A plurality of light emitting elements 100 are arranged on a circuit substrate 101. Each light emitting element 100 constitutes a pixel. The light emitting element 100 has a protruding pad 73, and the protruding pad 73 is electrically connected to the circuit substrate 101. For example, the protruding pad 73 may be bonded to a pad exposed on the circuit substrate 101.

[0057] The interval between the light emitting elements 100 may be at least greater than the width of the light emitting element.

[0058] For the specific structure of the light emitting element 100, refer to Figure 3a , Figure 3b , Figure 3c and Figure 3d Provide explanation. Figure 3a is a schematic plan view for illustrating a light emitting element 100 according to an embodiment of the present disclosure, Figure 3b , Figure 3c and Figure 3d Along Figure 3a For ease of explanation, although in Figure 3a , Figure 3b , Figure 3c and Figure 3d FIG. 1 shows and describes the case where the raised pads 73r, 73b, 73g, and 73c are arranged on the upper side, but the light emitting element 100 is Figure 2 As shown, flip-chip bonding is performed on the circuit substrate 101, in which case the bump pads 73r, 73b, 73g, 73c are arranged on the lower side.

[0059] Reference Figure 3a , Figure 3b , Figure 3c and Figure 3d The light emitting element 100 may include a substrate 41, a first LED stack 23, a second LED stack 33, a third LED stack 43, a first transparent electrode 25, a second transparent electrode 35, a third transparent electrode 45, an n-electrode pad 47a, a lower p-electrode pad 47b, an upper p-electrode pad 53g, a lower p-connector 53b, a lower common connector 53c, an upper common connector 63c, a first upper connector 63r, a second upper connector 63g, a third upper connector 63b, a first bonding layer 49, a second bonding layer 59, a lower insulating layer 51, an intermediate insulating layer 61, an upper insulating layer 71, and protruding pads 73r, 73b, 73g, 73c. ​​Further, the light emitting element 100 may include through holes 23h1, 23h2, 23h3, 23h4 penetrating the first LED stack 23 and through holes 33h1, 33h2 penetrating the second LED stack 33.

[0060] The substrate 41 may be a gallium nitride substrate, a SiC substrate, a sapphire substrate or a patterned sapphire substrate. The substrate 41 may be a growth substrate for growing the third LED stack 43 .

[0061] like Figure 3b As shown, the first LED stack 23, the second LED stack 33, and the third LED stack 43 according to the embodiment of the present disclosure are stacked in a vertical direction. In addition, although the LED stacks 23, 33, and 43 are grown on different growth substrates, in the embodiment of the present disclosure, the growth substrates other than the substrate 41 may not remain in the light emitting element 100 and may be removed in the end. However, the present disclosure is not necessarily limited to this, and other growth substrates may also be included.

[0062] The first LED stack 23, the second LED stack 33 and the third LED stack 43 respectively include first conductive semiconductor layers 23a, 33a, 43a, second conductive semiconductor layers 23b, 33b, 43b and active layers (not shown) disposed therebetween. The active layers may have a multi-quantum well structure.

[0063] The second LED stack 33 is arranged below the first LED stack 23, and the third LED stack 43 is arranged below the second LED stack 33. The substrate 41 is arranged below the third LED stack 43. For ease of description, in this specification, the second LED stack 33 is arranged below the first LED stack 23, and the third LED stack 43 is arranged below the second LED stack 33. However, it should be noted that the light emitting elements can be flip-chip bonded, so the upper and lower positions of these first to third LED stacks can be interchanged.

[0064] The light generated by the first LED stack 23 , the second LED stack 33 , and the third LED stack 43 is finally emitted to the outside through the third LED stack 43 and the substrate 41 .

[0065] In one embodiment, the first LED stack 23 may emit light of a longer wavelength than the second LED stack 33 and the third LED stack 43, and the second LED stack 33 may emit light of a longer wavelength than the third LED stack 43. For example, the first LED stack 23 may be an inorganic light emitting diode that emits red light, the second LED stack 33 may be an inorganic light emitting diode that emits green light, and the third LED stack 43 may be an inorganic light emitting diode that emits blue light. The first LED stack 23 may include a well layer of the AlGaInP series, the second LED stack 33 may include a well layer of the AlGaInP series or the AlGaInN series, and the third LED stack 43 may include a well layer of the AlGaInN series.

[0066] Since the first LED stack 23 emits light of a longer wavelength than the second LED stack 33 and the third LED stack 43, the light generated in the first LED stack 23 can be emitted to the outside through the second LED stack 33 and the third LED stack 43. Furthermore, since the second LED stack 33 emits light of a longer wavelength than the third LED stack 43, the light generated in the second LED stack 33 can be emitted to the outside through the third LED stack 43.

[0067] In another embodiment, the first LED stack 23 may emit light of a longer wavelength than the second LED stack 33 and the third LED stack 43, and the second LED stack 33 may emit light of a shorter wavelength than the third LED stack 43. For example, the first LED stack 23 may be an inorganic light emitting diode that emits red light, the second LED stack 33 may be an inorganic light emitting diode that emits blue light, and the third LED stack 43 may be an inorganic light emitting diode that emits green light. The first LED stack 23 may include a well layer of the AlGaInP series, the second LED stack 33 may include a well layer of the AlGaInN series, and the third LED stack 43 may include a well layer of the AlGaInP series or the AlGaInN series.

[0068] A portion of the light generated in the second LED stack 33 may be absorbed in the third LED stack 43, and therefore the luminosity of the light emitted from the second LED stack 33 may be relatively lower than the luminosity of the light emitted from the first LED stack 23 or the third LED stack 43. Accordingly, the luminosity ratio of the light emitted from the first LED stack 23, the second LED stack 33, and the third LED stack 43 may be controlled.

[0069] In addition, the first conductive semiconductor layers 23a, 33a, 43a of each LED stack 23, 33, 43 are n-type semiconductor layers, and the second conductive semiconductor layers 23b, 33b, 43b are p-type semiconductor layers. In addition, in the present embodiment, the upper surface of the first LED stack 23 is the n-type semiconductor layer 23a, the upper surface of the second LED stack 33 is the p-type semiconductor layer 33b, and the upper surface of the third LED stack 43 is the p-type semiconductor layer 43b. That is, only the order of the semiconductor layers of the first LED stack 23 is reversed. By arranging the semiconductor layers of the second LED stack 33 in the same order as the semiconductor layers of the third LED stack 43, the stability of the process can be ensured, which will be described in detail later when the manufacturing method is described.

[0070] The second LED stack 33 includes a mesa-etched region in which the upper surface of the first conductive semiconductor layer 33a is exposed by removing the second conductive semiconductor layer 33b. The third LED stack 43 also includes a mesa-etched region in which the upper surface of the first conductive semiconductor layer 43a is exposed by removing the second conductive semiconductor layer 43b. In contrast, the first LED stack 23 does not include a mesa-etched region. The through holes 33h1 and 33h2 may be formed in the mesa-etched region, and therefore, the side walls of the through holes 33h1 and 33h2 may have a stepped structure. In contrast, since the first LED stack 23 does not include a mesa-etched region, the through holes 23h1, 23h2, 23h3, and 23h4 may have a side wall with a constant slope without a stepped side wall. Further, in one embodiment, the second LED stack 33 may have a first conductive semiconductor layer 33a with a textured surface.

[0071] In this embodiment, the first LED stack 23, the second LED stack 33, and the third LED stack 43 may overlap each other and have light-emitting areas of approximately the same size. However, due to the through holes 23h1, 23h2, 23h3, 23h4 and the through holes 33h1, 33h2, the light-emitting area of ​​the first LED stack 23 may be smaller than the light-emitting area of ​​the second LED stack 33, and the light-emitting area of ​​the second LED stack 33 may be smaller than the light-emitting area of ​​the third LED stack 43. In addition, the side surface of the light-emitting element 100 may be inclined in a manner that the width increases from the first LED stack 23 to the third LED stack 43, and accordingly, the light-emitting area of ​​the third LED stack 43 may be further larger than the light-emitting area of ​​the first LED stack 23. The inclination angle formed by the side surface of the light-emitting element 100 relative to the upper surface of the third LED stack 43 may be about 75 degrees to 90 degrees. If the inclination angle is less than 75 degrees, the light-emitting area of ​​the first LED stack 23 is too small, so that it is difficult to reduce the size of the light-emitting element 100.

[0072] The first transparent electrode 25 is arranged between the first LED stack 23 and the second LED stack 33. The first transparent electrode 25 is in ohmic contact with the second conductive semiconductor layer 23b of the first LED stack 23, and transmits the light generated in the first LED stack 23. The first transparent electrode 25 can be formed using a transparent oxide layer or a metal layer such as indium tin oxide (ITO). The first transparent electrode 25 can cover the front surface of the second conductive semiconductor layer 23b of the first LED stack 23, and its side surface can be aligned with the side surface of the first LED stack 23. That is, the side surface of the first transparent electrode 25 may not be covered by the second bonding layer 59. Further, the through holes 23h2, 23h3, and 23h4 can penetrate the first transparent electrode 25, so the first transparent electrode 25 can be exposed at the side walls of these through holes. In addition, the through hole 23h1 exposes the upper surface of the first transparent electrode 25. However, the present disclosure is not limited thereto, and the first transparent electrode 25 may be partially removed along the edge of the first LED stack 23, so that the side of the first transparent electrode 25 is covered by the second bonding layer 59. Furthermore, the first transparent electrode 25 may be patterned and removed in advance in the region where the through holes 23h2, 23h3, and 23h4 are formed, so that the first transparent electrode 25 is not exposed on the side walls of the through holes 23h2, 23h3, and 23h4.

[0073] In addition, the second transparent electrode 35 is in ohmic contact with the second conductive semiconductor layer 33b of the second LED stack 33. As shown in the figure, the second transparent electrode 35 is in contact with the upper surface of the second LED stack 33 between the first LED stack 23 and the second LED stack 33. The second transparent electrode 35 can be formed using a metal layer or a conductive oxide layer that is transparent to red light. The conductive oxide layer can be, for example, SnO2, InO2, ITO, ZnO, IZO, etc. In particular, the second transparent electrode 35 can be formed using ZnO, which can be formed as a single crystal on the second LED stack 33, so that the electrical and optical properties are superior to those of the metal layer or other conductive oxide layers. In particular, ZnO has a strong bonding force to the second LED stack 33, so that it will not be damaged and remain even if the growth substrate is separated by laser stripping.

[0074] In addition, the second transparent electrode 35 can be partially removed along the edge of the second LED stack 33, and accordingly, the bottom side of the second transparent electrode 35 is not exposed to the outside and is covered by the lower insulating layer 51. That is, the side of the second transparent electrode 35 is recessed inwardly than the side of the second LED stack 33, and the recessed area of ​​the second transparent electrode 35 is filled with the lower insulating layer 51 and the second bonding layer 59. In addition, the second transparent electrode 35 is also recessed near the mesa etching area of ​​the second LED stack 33, and the recessed area is filled with the lower insulating layer 51 and the second bonding layer 59.

[0075] The third transparent electrode 45 is in ohmic contact with the second conductive semiconductor layer 43b of the third LED stack 43. The third transparent electrode 45 can be located between the second LED stack 33 and the third LED stack 43, and is in contact with the upper surface of the third LED stack 43. The third transparent electrode 45 can be formed using a metal layer or a conductive oxide layer that is transparent to red light and green light. The conductive oxide layer can be, for example, SnO2, InO2, ITO, ZnO, IZO, etc. In particular, the third transparent electrode 45 can be formed using ZnO, which can be formed as a single crystal on the third LED stack 43, and therefore has superior electrical and optical properties compared to metal layers or other conductive oxide layers. In particular, ZnO has a strong bonding force to the third LED stack 43, so that it will not be damaged and remain even if the growth substrate is separated by laser stripping.

[0076] The third transparent electrode 45 may be partially removed along the edge of the third LED stack 43, and accordingly, the bottom side of the third transparent electrode 45 is not exposed to the outside, but is covered by the first bonding layer 49. That is, the side of the third transparent electrode 45 is recessed inwardly than the side of the third LED stack 43, and the recessed area of ​​the third transparent electrode 45 is filled with the first bonding layer 49. In addition, the third transparent electrode 45 is also recessed near the mesa etching area of ​​the third LED stack 43, and the recessed area is filled with the first bonding layer 49.

[0077] By making the second transparent electrode 35 and the third transparent electrode 45 recessed as described above, it is possible to prevent the side surfaces thereof from being exposed to the etching gas, thereby improving the process yield of the light emitting element 100 .

[0078] In addition, in the present embodiment, the second transparent electrode 35 and the third transparent electrode 45 can be formed using the same type of conductive oxide layer, for example, ZnO, and the first transparent electrode 25 can be formed using a conductive oxide layer different from the second transparent electrode 35 and the third transparent electrode 45, for example, ITO. However, the present disclosure is not limited thereto, and the first transparent electrode 25, the second transparent electrode 35, and the third transparent electrode 45 can all be the same type, or at least one of them can be a different type.

[0079] The n-electrode pad 47a is in ohmic contact with the first conductive semiconductor layer 43a of the third LED stack 43. The n-electrode pad 47a can be arranged on the first conductive semiconductor layer 43a exposed by the second conductive semiconductor layer 43b, that is, arranged in the mesa etching area. The n-electrode pad 47a can be formed using Cr / Au / Ti, for example. The upper surface of the n-electrode pad 47a can be higher than the upper surface of the second conductive semiconductor layer 43b, and further can be higher than the upper surface of the third transparent electrode 45. For example, the thickness of the n-electrode pad 47a can be about 2μm or more. The n-electrode pad 47a can be in the shape of a truncated cone, but is not limited thereto, and can have various shapes such as a quadrangular truncated cone, a cylinder, a quadrangular prism, etc.

[0080] The lower p-electrode pad 47b can be formed using the same material as the n-electrode pad 47a. However, the upper surface of the lower p-electrode pad 47b can be located at the same height as the n-electrode pad 47a, so the thickness of the lower p-electrode pad 47b can be smaller than that of the n-electrode pad 47a. That is, the thickness of the lower p-electrode pad 47b can be substantially the same as the thickness of the portion of the n-electrode pad 47a protruding above the third transparent electrode 45. For example, the thickness of the lower p-electrode pad 47b can be approximately 1.2 μm or less. By making the upper surface of the lower p-electrode pad 47b located at the same height as the n-electrode pad 47a, the lower p-electrode pad 47b and the n-electrode pad 47a can be exposed at the same time when the through holes 33h1 and 33h2 are formed. In the case where the heights of the n-electrode pad 47a and the lower p-electrode pad 47b are different, one of the electrode pads may be significantly damaged during the etching process. Therefore, by making the heights of the n-electrode pad 47 a and the lower p-electrode pad 47 b substantially the same, it is possible to prevent one of the electrode pads from being significantly damaged during the etching process.

[0081] The first bonding layer 49 bonds the second LED stack 33 to the third LED stack 43. The first bonding layer 49 may bond the first conductive semiconductor layer 33a to the third transparent electrode 45 between them. The first bonding layer 49 may partially contact the second conductive semiconductor layer 43b and may partially contact the first conductive semiconductor layer 43a exposed in the mesa etched region. Furthermore, the first bonding layer 49 may cover the n-electrode pad 47a and the lower p-electrode pad 47b.

[0082] The first bonding layer 49 can be formed by a transparent organic layer or a transparent inorganic layer. The organic layer can be, for example, SU8, polymethyl methacrylate (PMMA), polyimide, polyparaxylene, benzocyclobutene (BCB), etc., and the inorganic layer can be, for example, Al2O3, SiO2, SiN xEtc. Also, the first bonding layer 49 may be formed using spin-on glass (SOG).

[0083] The through hole 33h1 and the through hole 33h2 penetrate the second LED stack 33 and the first bonding layer 49 to expose the n-electrode pad 47a and the lower p-electrode pad 47b respectively. As described above, the through holes 33h1 and 33h2 can be formed in the mesa etching area, so the through holes 33h1 and 33h2 can have stepped sidewalls.

[0084] The lower insulating layer 51 is formed on the second LED stack 33 and covers the second transparent electrode 35. The lower insulating layer 51 also covers the side walls of the through holes 33h1 and 33h2. The lower insulating layer 51 may have an opening 51a that exposes the n-electrode pad 47a, the lower p-electrode pad 47b, the first conductive semiconductor layer 33a, and the second transparent electrode 35. The lower insulating layer 51 may be formed using a silicon oxide film or a silicon nitride film, and may be formed to a thickness of, for example, about 800 nm.

[0085] The lower common connector 53c may be disposed on the lower insulating layer 51 and connected to the first conductive type semiconductor layer 33a and the n-electrode pad 47a exposed through the opening 51a of the lower insulating layer 51. The lower common connector 53c is connected to the first conductive type semiconductor layer 33a in the mesa-etched region of the second LED stack 33, and is connected to the n-electrode pad 47a through the through hole 33h1.

[0086] The lower p connector 53b may be disposed on the lower insulating layer 51 and connected to the p electrode pad 47b exposed through the opening 51a of the lower insulating layer 51. At least a portion of the lower p connector 53b is located on the lower insulating layer 51.

[0087] In addition, the upper p-electrode pad 53g may be arranged on the second transparent electrode 35 in the opening 51a of the lower insulating layer 51. Figure 3a and Figure 3b As shown, the upper p-electrode pad 53g may have a width narrower than the opening 51a and be arranged in the opening 51a, but the present disclosure is not limited to this. The width of the upper p-electrode pad 53g may be greater than the width of the opening 51a, and a portion of the upper p-electrode pad 53g may also be located on the lower insulating layer 51.

[0088] The lower common connector 53c, the lower p connector 53b and the upper p electrode pad 53g can be formed together in the same process using the same material. The lower common connector 53c, the lower p connector 53b and the upper p electrode pad 53g can be formed using Ni / Au / Ti, for example, and can be formed to a thickness of about 2 μm.

[0089] The second bonding layer 59 bonds the first LED stack 23 to the second LED stack 33. As shown in the figure, the second bonding layer 59 can be arranged between the first transparent electrode 25 and the lower insulating layer 51. In addition, the second bonding layer 59 can cover the lower common connector 53c, the lower p connector 53b, and the upper p electrode pad 53g. In addition, the second bonding layer 59 can partially contact the second transparent electrode 35 exposed through the opening 51a of the lower insulating layer 51. The second bonding layer 59 can be formed using the same material as described above for the first bonding layer 49, and detailed description is omitted to avoid repetition.

[0090] In addition, through holes 23h1, 23h2, 23h3, and 23h4 penetrate the first LED stack 23. The through hole 23h1 is formed to provide a path for allowing electrical connection to the first transparent electrode 25. In the present embodiment, the through hole 23h1 exposes the upper surface of the first transparent electrode 25 and does not penetrate the first transparent electrode 25. However, the present disclosure is not limited to this, and the through hole 23h1 may penetrate the first transparent electrode 25 as long as it provides a path for electrical connection to the first transparent electrode 25.

[0091] The through holes 23h2, 23h3, and 23h4 can penetrate the first LED stack 23 and the second bonding layer 59. The through hole 23h2 exposes the upper p electrode pad 53g, the through hole 23h3 exposes the lower p connector 53b, and the through hole 23h4 exposes the lower common connector 53c.

[0092] The through holes 23h1, 23h2, 23h3, and 23h4 can be formed by etching the first conductive semiconductor layer 23a and the second conductive semiconductor layer 23b in the same process. Therefore, the side walls of the through holes 23h1, 23h2, 23h3, and 23h4 can have smooth inclined surfaces without having a stepped structure.

[0093] The intermediate insulating layer 61 covers the first LED stack 23 and covers the side walls of the through holes 23h1, 23h2, 23h3, and 23h4. The intermediate insulating layer 61 may also cover the side surfaces of the first LED stack 23, the second LED stack 33, and the third LED stack 43. In addition, the intermediate insulating layer 61 may also cover the substrate 41 exposed on the side surfaces of the first LED stack to the third LED stack. The intermediate insulating layer 61 may be patterned to have an opening 61a that exposes the bottom of each through hole 23h1, 23h2, 23h3, and 23h4. The first transparent electrode 25, the upper p electrode pad 53g, the lower p connector 53b, and the lower common connector 53c are exposed in the through holes 23h1, 23h2, 23h3, and 23h4 through the opening 61a. Further, the intermediate insulating layer 61 may have an opening 61b exposing the upper surface (i.e., the first conductive semiconductor layer 23a) of the first LED stack 23. The intermediate insulating layer 61 may be formed of an aluminum oxide film, a silicon oxide film, or a silicon nitride film, and may be formed to a thickness of about 800 nm, for example.

[0094] The first upper connector 63r, the second upper connector 63g, the third upper connector 63b and the upper common connector 63c are arranged on the intermediate insulating layer 61. These upper connectors 63r, 63g, 63b, 63c are respectively connected to the first transparent electrode 25, the upper p-electrode pad 53g, the lower p-connector 53b and the lower common connector 53c exposed through the opening 61a of the intermediate insulating layer 61. Further, the upper common connector 63c can be connected to the first conductive type semiconductor layer 23a exposed in the opening 61b.

[0095] The first upper connector 63r, the second upper connector 63g, the third upper connector 63b and the upper common connector 63c can be formed using the same material in the same process, for example, can be formed using AuGe / Ni / Au / Ti. AuGe can be in ohmic contact with the first conductive semiconductor layer 23a. AuGe can be formed to a thickness of about 100 nm, and Ni / Au / Ti can be formed to a thickness of about 2 μm. AuTe can also be used instead of AuGe.

[0096] The upper insulating layer 71 covers the middle insulating layer 61 and covers the first upper connector 63r, the second upper connector 63g, the third upper connector 63b, and the upper common connector 63c. In addition, the upper insulating layer 71 may cover the middle insulating layer 61 on the side of the first LED stack 23, the second LED stack 33, and the third LED stack 43. The upper insulating layer 71 may have an opening 71a that exposes the first upper connector 63r, the second upper connector 63g, the third upper connector 63b, and the upper common connector 63c. The opening 71a of the upper insulating layer 71 may be arranged roughly on the flat surface of the first upper connector 63r, the second upper connector 63g, the third upper connector 63b, and the upper common connector 63c. The upper insulating layer 71 may be formed using a silicon oxide film or a silicon nitride film, and may be thinner than the middle insulating layer 61, and may be formed to a thickness of, for example, about 400 nm.

[0097] The raised pads 73r, 73b, 73g, and 73c may be disposed on the first upper connector 63r, the second upper connector 63g, the third upper connector 63b, and the upper common connector 63c in the opening 71a of the upper insulating layer 71, respectively, to be electrically connected thereto.

[0098] The first protruding pad 73 r may be electrically connected to the second conductive semiconductor layer 23 b of the first LED stack 23 through the first upper connector 63 r and the first transparent electrode 25 .

[0099] The second protruding pad 73 g may be electrically connected to the second conductive semiconductor layer 33 b of the second LED stack 33 through the second upper connector 63 g , the upper p-electrode pad 53 g , and the second transparent electrode 35 .

[0100] The third protruding pad 73 b may be electrically connected to the second conductive semiconductor layer 43 b of the third LED stack 43 through the third upper connector 63 b , the lower p connector 53 b , the lower p electrode pad 47 b and the third transparent electrode 45 .

[0101] The common raised pad 73c can be electrically connected to the first conductive semiconductor layer 23a of the first LED stack 23 through the upper common connector 63c, and electrically connected to the first conductive semiconductor layer 33a of the second LED stack 33 through the lower common connector 53c, and further electrically connected to the first conductive semiconductor layer 43a of the third LED stack 43 through the n-electrode pad 47a.

[0102] That is, the first raised pad 73r, the second raised pad 73g, and the third raised pad 73b are electrically connected to the second conductive semiconductor layers 23b, 33b, and 43b of the first LED stack 23, the second LED stack 33, and the third LED stack 43, respectively, and the common raised pad 73c is electrically connected to the first conductive semiconductor layers 23a, 33a, and 43a of the first LED stack 23, the second LED stack 33, and the third LED stack 43.

[0103] The raised pads 73r, 73b, 73g, 73c may be arranged in the opening 71a of the upper insulating layer 71, and the upper surface of the raised pads may be a flat surface. The raised pads 73r, 73b, 73g, 73c may be located on the flat surfaces of the first upper connector 63r, the second upper connector 63g, the third upper connector 63b, and the upper common connector 63c. The raised pads 73r, 73b, 73g, 73c may be formed using Au / In, for example, Au may be formed to a thickness of 3 μm, and In may be formed to a thickness of about 1 μm. The light emitting element 100 may be bonded to the pad on the circuit substrate 101 using In. In this embodiment, although the case of bonding the raised pads using In is described, it is not limited to In, and bonding may also be performed using Pb or AuSn.

[0104] In this embodiment, the upper surfaces of the raised pads 73r, 73b, 73g, and 73c are described and illustrated as being flat, but the present disclosure is not limited thereto. For example, the upper surfaces of the raised pads 73r, 73b, 73g, and 73c may be irregular surfaces, and a portion of the raised pads may be located on the upper insulating layer 71.

[0105] According to this embodiment, the first LED stack 23 is electrically connected to the raised pads 73r and 73c, the second LED stack 33 is electrically connected to the raised pads 73g and 73c, and the third LED stack 43 is electrically connected to the raised pads 73b and 73c. ​​Accordingly, the cathodes of the first LED stack 23, the second LED stack 33, and the third LED stack 43 are electrically connected to the common raised pad 73c, and the anodes are electrically connected to the first raised pad 73r, the second raised pad 73g, and the third raised pad 73b, respectively. Therefore, the first LED stack 23, the second LED stack 33, and the third LED stack 43 can be driven independently.

[0106] The structure of the light emitting element 100 will be understood in more detail through the manufacturing method of the light emitting element 100 described below. Figure 4a , Figure 4b and Figure 4c Schematic cross-sectional views for illustrating first to third LED stacks mounted on a growth substrate according to an embodiment of the present disclosure.

[0107] First, refer to Figure 4a A first LED stack 23 including a first conductive semiconductor layer 23a and a second conductive semiconductor layer 23b is grown on a first substrate 21. An active layer (not shown) may exist between the first conductive semiconductor layer 23a and the second conductive semiconductor layer 23b.

[0108] The first substrate 21 is a substrate that can be used to grow the first LED stack 23, and can be, for example, a GaAs substrate. The first conductive semiconductor layer 23a and the second conductive semiconductor layer 23b can be formed using semiconductor layers of the AlGaInAs series or the AlGaInP series, and the active layer can include, for example, a well layer of the AlGaInP series. The composition ratio of AlGaInP can be determined so that the first LED stack 23 emits, for example, red light.

[0109] A first transparent electrode 25 may be formed on the second conductive semiconductor layer 23b. As described above, the first transparent electrode 25 may be formed using a metal layer or a conductive oxide layer that transmits light (e.g., red light) generated in the first LED stack 23. For example, the first transparent electrode 25 may be formed using ITO (indium-tin oxide).

[0110] In addition, a second LED stack 33 including a first conductive semiconductor layer 33a and a second conductive semiconductor layer 33b is grown on the second substrate 31. An active layer (not shown) may exist between the first conductive semiconductor layer 33a and the second conductive semiconductor layer 33b.

[0111] The second substrate 31 is a substrate that can be used to grow the second LED stack 33, and can be, for example, a sapphire substrate, a GaN substrate, or a GaAs substrate. The first conductive semiconductor layer 33a and the second conductive semiconductor layer 33b can be formed using semiconductor layers of the AlGaInAs series or the AlGaInP series, or semiconductor layers of the AlGaInN series, and the active layer can include, for example, a well layer of the AlGaInP series or a well layer of the AlGaInN series. The composition ratio of AlGaInP or AlGaInN can be determined so that the second LED stack 33 emits, for example, green light.

[0112] A second transparent electrode 35 may be formed on the second conductive semiconductor layer 33b. As described above, the second transparent electrode 35 may be formed using a metal layer or a conductive oxide layer that transmits light (eg, red light) generated in the first LED stack 23. In particular, the second transparent electrode 35 may be formed using ZnO.

[0113] In addition, a third LED stack 43 including a first conductive semiconductor layer 43a and a second conductive semiconductor layer 43b is grown on the third substrate 41. An active layer (not shown) may exist between the first conductive semiconductor layer 43a and the second conductive semiconductor layer 43b.

[0114] The third substrate 41 is a substrate that can be used to grow the third LED stack 43, and can be, for example, a sapphire substrate, a SiC substrate, or a GaN substrate. In one embodiment, the third substrate 41 can be a flat sapphire substrate, but can also be a patterned sapphire substrate. The first conductive semiconductor layer 43a and the second conductive semiconductor layer 43b can be formed using AlGaInN series semiconductor layers, and the active layer can include, for example, an AlGaInN series well layer. The composition ratio of AlGaInN can be determined so that the third LED stack 43 emits, for example, blue light.

[0115] A third transparent electrode 45 may be formed on the second conductive semiconductor layer 43b. As described above, the third transparent electrode 45 may be formed using a metal layer or a conductive oxide layer that transmits light (e.g., red light and green light) generated by the first LED stack 23 and the second LED stack 33. In particular, the third transparent electrode 45 may be formed using ZnO.

[0116] The first LED stack 23 , the second LED stack 33 , and the third LED stack 43 are grown on different growth substrates 21 , 31 , and 41 , respectively. Therefore, the order of their manufacturing processes is not limited.

[0117] Hereinafter, a method for manufacturing the light emitting element 100 using the first LED stack 23, the second LED stack 33, and the third LED stack 43 grown on the growth substrate 21, 31, and 41 will be described. Hereinafter, although the illustration and description are mainly for one light emitting element 100 region, it will be understood by those skilled in the art that a plurality of light emitting elements 100 can be manufactured in batches in the same manufacturing process using the first LED stack 23, the second LED stack 33, and the third LED stack 43 grown on the growth substrate 21, 31, and 41.

[0118] Figure 5a , Figure 5b , Figure 5c , Figure 5d , Figure 6a , Figure 6b , Figure 6c , Figure 6d , Figure 7a , Figure 7b , Figure 7c , Figure 7d , Figure 8a , Figure 8b , Figure 8c , Figure 8d , Figure 9a , Figure 9b , Fig.9c , Figure 9d , Fig.10a , Fig.10b , Fig.10c , Fig.10d , Fig.11a , Fig.11b , Fig.11c , Fig.11d , Fig.12a , Figure 12b , Fig.12c , Fig.12d , Fig.13a , Fig.13b , Fig.13c and Fig.13d 1 is a schematic plan view and a cross-sectional view for explaining a method for manufacturing a display light-emitting element 100 according to an embodiment of the present disclosure. Figure 3b , Figure 3c and Figure 3d The illustration is given in the form of a cross-sectional view.

[0119] First, refer to Figure 5a , Figure 5b , Figure 5c and Figure 5d , the third transparent electrode 45 and the second conductive semiconductor layer 43b are patterned by photolithography and etching techniques to expose the first conductive semiconductor layer 43a. This process may correspond to, for example, a mesa etching process. The photoresist pattern may be used as an etching mask to perform. For example, after forming an etching mask, the third transparent electrode 45 may be first etched by a wet etching technique, and then the second conductive semiconductor layer 43b may be etched by a dry etching technique using the same etching mask. Accordingly, the third transparent electrode 45 may be recessed from the mesa etching area. In order to briefly illustrate the drawings, Figure 5a The edge of the table is shown in the figure, but the edge of the third transparent electrode 45 is not shown. However, since the third transparent electrode 45 is wet-etched using the same etching mask, it is easy to understand that the edge of the third transparent electrode 45 is recessed from the edge of the table to the inside of the table. Since the same etching mask is used, the number of photolithography processes will not increase, thereby saving process costs. However, the present disclosure is not limited to this, and an etching mask for the table etching process and an etching mask for etching the third transparent electrode 45 may be used separately.

[0120] Next, the n-electrode pad 47a and the lower p-electrode pad 47b are respectively formed on the first conductive semiconductor layer 43a and the third transparent electrode 45. The n-electrode pad 47a and the lower p-electrode pad 47b can be formed to have different thicknesses. In particular, the upper surfaces of the n-electrode pad 47a and the lower p-electrode pad 47b can be located at the same height.

[0121] Reference Figure 6a , Figure 6b , Figure 6c and Figure 6d , in reference Figure 5a , Figure 5b , Figure 5c and Figure 5d The third LED stack 43 is shown with reference to the bonding Figure 4b The second LED stack 33 described. The second LED stack 33 is bonded to the temporary substrate using a temporary bonding / debonding (TBDB) technique, and the second substrate 31 is first removed from the second LED stack 33. The second substrate 31 can be removed, for example, using a laser lift-off technique. After removing the second substrate 31, a rough surface can be formed on the surface of the first conductive semiconductor layer 33a. Thereafter, the first conductive semiconductor layer 33a of the second LED stack 33 bonded to the temporary substrate can be arranged to face the third LED stack 43 and bonded to the third LED stack 43. The second LED stack 33 and the third LED stack 43 are bonded to each other via a first bonding layer 49. After the second LED stack 33 is bonded, the temporary substrate can also be removed using a laser lift-off technique. Accordingly, the second LED stack 33 can be arranged on the third LED stack 43 in a form in which a second transparent electrode 35 is arranged on the upper surface.

[0122] When the second substrate 31 is separated by laser lift-off technology, ITO may be peeled off from the second LED stack 33. Therefore, in the case of removing the second substrate 31 by laser lift-off technology, it is advantageous to form the second transparent electrode 35 using ZnO having excellent bonding strength.

[0123] Next, the second transparent electrode 35 and the second conductive semiconductor layer 33b are patterned to expose the first conductive semiconductor layer 33a. The second transparent electrode 35 and the second conductive semiconductor layer 33b can be patterned using photolithography and etching techniques. This process can be performed using wet etching and dry etching techniques by a method such as the mesa etching process for etching the third transparent electrode 45 and the second conductive semiconductor layer 43b described above.

[0124] For example, after forming the etching mask, the second transparent electrode 35 may be first etched by wet etching, and then the second conductive semiconductor layer 33b may be etched by dry etching using the same etching mask. Accordingly, the second transparent electrode 35 may be recessed from the mesa etching region. In order to briefly illustrate the drawings, Figure 6a The edge of the table is shown in the figure, but the edge of the second transparent electrode 35 is not shown. However, since the second transparent electrode 35 is wet-etched using the same etching mask, it can be easily understood that the edge of the second transparent electrode 35 is recessed from the edge of the table to the inside of the table. Since the same etching mask is used, the number of photolithography processes will not increase, thereby saving process costs. However, the present disclosure is not limited to this, and an etching mask for the table etching process and an etching mask for etching the second transparent electrode 35 may also be used separately.

[0125] like Figure 6a As shown, the mesa etched region of the second LED stack 33 may overlap a portion of the mesa etched region of the third LED stack 43. For example, a portion of the mesa etched region of the second LED stack 33 may be formed on the upper portion of the n-electrode pad 47a. Furthermore, another portion of the mesa etched region may be located on the upper portion of the lower p-electrode pad 47b. Further, a portion of the mesa etched region of the second LED stack 33 may be located on the mesa etched region of the third LED stack 43.

[0126] Reference Figure 7a , Figure 7b , Figure 7c and Figure 7d , through holes 33h1 and 33h2 are formed to penetrate the second LED stack 33. The through holes 33h1 and 33h2 penetrate the first bonding layer 49 to expose the n-electrode pad 47a and the lower p-electrode pad 47b. The through holes 33h1 and 33h2 can be formed in the mesa etching area, so the side walls of the through holes 33h1 and 33h2 can have a stepped structure.

[0127] Since the upper surfaces of the lower p-electrode pad 47 b and the n-electrode pad 47 a are located at the same height, it is possible to prevent any one of the pads from being exposed first and damaged during the formation of the through holes 33 h 1 and 33 h 2 .

[0128] Reference Figure 8a , Figure 8b , Figure 8c and Figure 8d, a lower insulating layer 51 is formed on the second LED stack 33. The lower insulating layer 51 covers the second transparent electrode 35 and the second conductive semiconductor layer 33b. In addition, the lower insulating layer 51 covers the side walls of the through holes 33h1 and 33h2. In addition, the lower insulating layer 51 has an opening 51a that exposes the second transparent electrode 35, the first conductive semiconductor layer 33a, the n-electrode pad 47a, and the lower p-electrode pad 47b.

[0129] Next, the lower common connector 53c, the lower p connector 53b, and the upper p electrode pad 53g are formed on the lower insulating layer 51. The lower common connector 53c, the lower p connector 53b, and the upper p electrode pad 53g can be formed together using the same material.

[0130] The upper p-electrode pad 53b may be disposed on the second transparent electrode 35 exposed in the opening 51a. The lower p-connector 53b is connected to the lower p-electrode pad 47b exposed through the opening 51a, and a portion thereof is disposed on the lower insulating layer 51. The lower common connector 53c is connected to the first conductive semiconductor layer 33a and the n-electrode pad 47a exposed through the opening 51a, and a portion thereof is disposed on the lower insulating layer 51.

[0131] Reference Figure 9a , Figure 9b , Fig.9c and Figure 9d , Figure 4a The illustrated first LED stack 23 is bonded to the second LED stack 33. The first LED stack 23 and the second LED stack 33 can be bonded by the second bonding layer 59 in such a manner that the first transparent electrode 25 faces the second LED stack 33. Accordingly, the second bonding layer 59 can contact the first transparent electrode 25 while contacting the lower insulating layer 51, the lower p connector 53b, the upper p electrode pad 53g and the lower common connector 53c, and further contacting the second transparent electrode 35 exposed around the lower p connector 53b. The first substrate 21 is removed from the first LED stack 23. The first LED stack 23 can be removed, for example, by etching technology.

[0132] Reference Fig.10a , Fig.10b , Fig.10c and Fig.10d, through holes 23h1, 23h2, 23h3, and 23h4 are formed to penetrate the first LED stack 23. The through hole 23h1 exposes the first transparent electrode 25, and the through holes 23h2, 23h3, and 23h4 penetrate the second bonding layer 59 to expose the upper p electrode pad 53g, the lower p connector 53b, and the lower common connector 53c, respectively. Since the through hole 23h1 and the through holes 23h2, 23h3, and 23h4 have different depths, they can be formed by different processes. In addition, since the depths of the through holes 23h2, 23h3, and 23h4 are substantially the same, they can be formed together in the same process.

[0133] The through holes 23h1, 23h2, 23h3, and 23h4 may be formed to penetrate the entire first LED stack 23, and therefore, unlike the through holes 33h1 and 33h2, the side walls of these through holes may be formed without steps.

[0134] Reference Fig.11a , Fig.11b , Fig.11c and Fig.11d , a separation groove for defining the light emitting element 100 region is formed by an isolation process. The separation groove can expose the third substrate 41 along the periphery of the first LED stack 23, the second LED stack 33, and the third LED stack 43. The separation groove can be formed by sequentially removing the first LED stack 23, the first transparent electrode 25, the second bonding layer 59, the lower insulating layer 51, the second LED stack 33, the first bonding layer 49, and the third LED stack 43 between the light emitting element regions. The second transparent electrode 35 and the third transparent electrode 45 are not exposed during the isolation process, and therefore are not damaged by the etching gas. In the case where the second transparent electrode 35 and the third transparent electrode 45 are formed using ZnO, ZnO may be easily damaged by the etching gas. However, the present disclosure can prevent the second transparent electrode 35 and the third transparent electrode 45 from being exposed to the etching gas by recessing them in advance.

[0135] In this embodiment, the case where the first LED stack 23, the second LED stack 33, and the third LED stack 43 are patterned in sequence through the isolation process is described, but the present disclosure is not necessarily limited to this. The third LED stack 43 may be removed in advance in the area where the separation groove is formed before bonding the second LED stack 33, and the second LED stack 33 may be removed in advance in the area where the separation groove is formed before bonding the first LED stack 23. In this case, the area where the third LED stack 43 is removed can be filled with the first bonding layer 49, and the area where the second LED stack 33 is removed can be filled with the second bonding layer 59. Accordingly, the second LED stack 33 and the third LED stack 43 may not be exposed in the isolation process.

[0136] In yet another embodiment, the isolation process may be omitted. The light emitting elements may be separated from each other in the chip dividing process.

[0137] Reference Fig.12a , Figure 12b , Fig.12c and Fig.12d , an intermediate insulating layer 61 is formed on the first LED stack 23. The intermediate insulating layer 61 may cover the side surfaces of the first LED stack 23, the second LED stack 33, and the third LED stack 43, the side surfaces of the first bonding layer 49 and the second bonding layer 59, the side surfaces of the first transparent electrode 25, and the side surfaces of the lower insulating layer 51 exposed by the separation grooves, and may cover the upper surface of the substrate 41.

[0138] The intermediate insulating layer 61 may also cover the side surfaces of the through holes 23h1, 23h2, 23h3, and 23h4. However, the intermediate insulating layer 61 is patterned to have an opening 61a that exposes the bottom surfaces of the through holes 23h1, 23h2, 23h3, and 23h4, and an opening 61b that exposes the first conductive semiconductor layer 23a of the first LED stack 23. The opening 61a exposes the first transparent electrode 25, the upper p-electrode pad 53g, the lower p-connector 53b, and the lower common connector 53c in the through holes 23h1, 23h2, 23h3, and 23h4.

[0139] A first upper connector 63r, a second upper connector 63g, a third upper connector 63b and an upper common connector 63c are formed on the intermediate insulating layer 61. The first upper connector 63r can be connected to the first transparent electrode 25, the second upper connector 63g can be connected to the upper p-electrode pad 53g, and the third upper connector 63b can be connected to the lower p-connector 53b. In addition, the upper common connector 63c can be connected to the lower common connector 53c.

[0140] Reference Fig.13a , Fig.13b , Fig.13c and Fig.13d , an upper insulating layer 71 covering the middle insulating layer 61 and the connectors 63r, 63g, 63b, 63c is formed. The upper insulating layer 71 may cover the side surfaces of the first LED stack 23, the second LED stack 33, and the third LED stack 43, and also cover the middle insulating layer 61 on the substrate 41. However, the upper insulating layer 71 may be patterned to have an opening 71a exposing the first upper connector 63r, the second upper connector 63g, the third upper connector 63b, and the upper common connector 63c.

[0141] Next, raised pads 73r, 73b, 73g, and 73c are formed in the opening 71a, respectively. The first raised pad 73r is arranged on the first upper connector 63r, the second raised pad 73g is arranged on the second upper connector 63g, and the third raised pad 73b is arranged on the third upper connector 63b. The common raised pad 73c is arranged on the upper common connector 63c.

[0142] Next, the substrate 41 is divided to form individual light emitting elements 100, and such individual light emitting elements 100 are bonded to the circuit substrate 101. A schematic cross-sectional view of the light emitting element 100 bonded to the circuit substrate 101 is shown in FIG. Fig.14 Picture.

[0143] Fig.14 The figure shows a single light emitting element 100 arranged on the circuit substrate 101, but a plurality of light emitting elements 100 are mounted on the circuit substrate 101. Each light emitting element 100 constitutes a pixel capable of emitting blue light, green light, and red light, and a plurality of pixels are neatly arranged on the circuit substrate 101 to provide a display panel.

[0144] In addition, the light emitting element 100 may be covered by a black material film 110. The black material film 110 may be used to prevent light interference between the light emitting elements 100. The thickness of the black material film 110 on the light emitting element 100 may be thinner than the thickness of the black material film 110 on the side of the light emitting element 100, so that light can be emitted toward the upper part of the light emitting element 100, and the light propagating toward the side is absorbed by the black material film 110.

[0145] In addition, a plurality of light emitting elements 100 may be formed on the substrate 41, and these light emitting elements 100 are not transferred one by one to the circuit substrate 101, but can be collectively transferred to the circuit substrate 101. The substrate 41 formed with a plurality of light emitting elements 100 is generally called a wafer. Therefore, the wafer includes the substrate 41, the first LED stack to the third LED stack arranged overlappingly on the substrate 41, and the protruding pads formed in each light emitting element region. Figures 15a to 15i 1 is a schematic cross-sectional view for explaining a method of transferring a plurality of light emitting elements 100 on a wafer to a circuit substrate. Here, a method of collectively transferring the light emitting elements 100 formed on a substrate 41 to a circuit substrate 101 will be explained.

[0146] Reference Fig.15a , as described by the light emitting element manufacturing method, if the Fig.13a , Fig.13b , Fig.13c and Fig.13dA wafer having a plurality of light emitting elements 100 formed on a single substrate 41 is provided by a process. Here, for the sake of convenience, 10 light emitting element regions are shown, but more light emitting element regions may be included on one substrate 41. Further, the substrate 41 may be thinned by a thinning process to become thinner than when the third LED stack 43 is grown.

[0147] Then, laser scribing is used to form scribe lines on the substrate 41. The scribe lines may be formed on the upper surface of the substrate 41 or on the lower surface of the substrate 41. The scribe lines define the region of the light emitting element 100.

[0148] Reference Fig.15b , the light emitting element 100 is divided along the scribing line by the cracking process. The substrate 41 with the scribing groove formed by laser scribing can be cracked by a blade. In a state where the substrate 41 with the scribing groove formed is attached to the cracking tape 121, the blade applies impact or pressure to the substrate 41, thereby breaking along the scribing groove, thereby performing cracking. Accordingly, the single light emitting element 100 is divided into chip units along the scribing line.

[0149] Conventionally, after the cleavage is completed, the cleavage tape is expanded to separate the light emitting elements 100 . However, in this embodiment, the expansion step is omitted.

[0150] Reference Fig.15c , the light emitting element 100 that has been split is transferred to the temporary substrate 131 while maintaining its positional relationship. The temporary substrate 131 may include a transfer tape on its upper surface. The temporary substrate 131 is used to change the up-and-down direction of the substrate 41 and the raised pad. That is, as the light emitting element 100 is transferred to the temporary substrate 131, it is attached to the transfer tape in a manner that the raised pad of the light emitting element 100 faces the temporary substrate 131.

[0151] Reference Fig.15d The light emitting element 100 is transferred to the supporting substrate 141 while maintaining the positional relationship of the light emitting element 100 attached to the temporary substrate 131. The transfer tape 143 is arranged on the supporting substrate 141, so that the substrate 41 is attached to the transfer tape 143, and the raised pad is arranged away from the transfer tape 143.

[0152] In this embodiment, the transfer tape 143 may have a characteristic that the adhesive force varies according to the temperature. For example, the lower the temperature, the greater the adhesive force, and the higher the temperature, the smaller the adhesive force. In particular, the raised pad can be bonded to the circuit substrate by heating, and the adhesive force of the transfer tape 143 at the bonding temperature is relatively smaller than the adhesive force at room temperature.

[0153] The transfer tape 143 may be, for example, a tape including an acrylic or silicone resin adhesive, but is not limited thereto. The transfer tape 143 has heat resistance that allows it to maintain an adhesive force with a constant strength at a bonding temperature.

[0154] Reference Fig.15e A circuit substrate 101 having pads on its upper surface is provided. The pads are arranged on the circuit substrate 101 in a manner corresponding to the aligned positions of pixels for display. Generally, as shown in the figure, the intervals between the light emitting elements 100 aligned on the substrate 41 are closer than the intervals between the pixels in the circuit substrate 101.

[0155] Reference Fig.15f , the raised pad of the light emitting element 100 is bonded to the pad on the circuit substrate 101. The support substrate 141 is in close contact with the circuit substrate 101 so that the raised pad of the light emitting element 100 contacts the pad on the circuit substrate 101. Next, the raised pad and the pad are bonded to each other by pressing the support substrate 141 against 1 of the circuit substrate 10 and heating the raised pad and the pad at the same time. As an example, by heating the head of the fixed support substrate 141 and the loading part of the circuit substrate 101, heat is transferred to the raised pad and the pad, thereby the raised pad and the pad can be heated and bonded. The raised pad and the pad can be bonded, for example, using In, Pb, AuSn or CuSn bonding. In bonding can be bonded approximately in the range of about 150 to 200°C, AuSn bonding can be bonded in the range of about 300°C, and CuSn bonding can be bonded in the range of about 200 to 250°C. In addition, since the light emitting element 100 located between the pixel regions has no pad to be bonded, it maintains a state of being away from the circuit substrate 101 .

[0156] During the heating, metal bonding is formed by the metal between the protruding pads and the pads. After a sufficient bonding time, the metal bonding is completed at the bonding temperature, and the adhesion between the protruding pads and the pads on the circuit substrate 101 increases.

[0157] Reference Figure 15g By separating the light emitting element 100 bonded to the pad from the support substrate 141 and the transfer tape 143, the light emitting element 100 is transferred to the circuit substrate 101. Thus, a display panel in which the light emitting elements 100 are arranged in an orderly manner on the circuit substrate 101 is provided.

[0158] In one embodiment, the light emitting element 100 can be separated from the transfer tape 143 at the bonding temperature. In this case, the adhesive force between the transfer tape 143 and the light emitting element 100 at the bonding temperature is smaller than the adhesive force between the protruding pads and the pads, so the light emitting element 100 bonded to the pads is transferred to the circuit substrate 101.

[0159] In another embodiment, after bonding is completed at the bonding temperature, the bonding material can be cooled and cooled to an intermediate temperature that is higher than room temperature but lower than the bonding temperature. The light emitting element 100 can be separated from the transfer tape 143 at the intermediate temperature and transferred to the circuit substrate 101. The transfer tape 143 has a relatively low bonding force at an intermediate temperature lower than room temperature. In particular, at the intermediate temperature, the bonding force between the transfer tape 143 and the light emitting element 100 can be less than the bonding force between the raised pads and the pads, so that it can be easily transferred from the transfer tape 143 to the circuit substrate 101 at the intermediate temperature.

[0160] Furthermore, when the transfer tape 143 is cooled to room temperature, the adhesive force increases, and thus the light emitting element 100 remaining on the supporting substrate 141 can be stably held.

[0161] According to the present embodiment, the light emitting elements 100 separated into individual chips through the scribing and breaking steps are transferred to the transfer tape while maintaining their positional relationship. Therefore, the conventional rearrangement step is unnecessary, thereby shortening the mounting step time.

[0162] In particular, since the light-emitting elements 100 of the transferred first LED stack 23, the second LED stack 33, and the third LED stack 43 overlap with each other, it is not necessary to mount the light-emitting elements on a sub-pixel basis. Only one light-emitting element 100 can be mounted on each pixel to provide a display device, thereby further shortening the mounting process time.

[0163] Next, refer to Figure 15h The black material film 110 covers the light emitting element 100 on the circuit substrate 101. The black material film 110 can be attached to the light emitting element 100 by a vacuum lamination process, so that the black material film 110 can be closely attached to the light emitting element 100 and the circuit substrate 101.

[0164] Reference Fig.15i After the black material film 110 is closely attached to the light emitting element 100, rolling is used to flatten the black material film 110 on the light emitting element 100. Thus, the thickness of the black material film 110 on the light emitting element 100 can be reduced, and the area between the light emitting elements 100 can be filled with black material.

[0165] According to this, the display panel is completed, and the completed display panel can be mounted on the reference Figure 1 Various display devices are described.

[0166] Fig.16a and Fig.16b is a schematic cross-sectional view for explaining a method of transferring a light emitting element to a circuit substrate according to still another embodiment of the present disclosure.

[0167] Reference Fig.16a , this embodiment and the above reference Figures 15a to 15i The transfer method described is generally similar, but the difference is that the slicing step using a blade is omitted.

[0168] That is, in this embodiment, the splitting can be performed by laser scribing. Fig.15a In the embodiment, laser scribing forms a scribing groove on the upper surface or the lower surface of the substrate 41, but in the present embodiment, the laser scribing is formed through the substrate 41. Such laser scribing can be performed by using a reference Fig.15a The above-described laser division of the substrate 41 may be performed by irradiating the inside of the substrate 41 with laser light using an invisible laser.

[0169] And, since the light emitting element 100 is separated by laser scribing, the scribing process is performed in a state attached to the tape 121. At this time, the bump pads may be arranged toward the tape 121, and the laser scribing is performed in a state where the substrate 41 is arranged on the upper surface.

[0170] Reference Fig.16b The light emitting elements 100 divided into individual chips by laser scribing are transferred to the transfer tape 143 on the support substrate 141 while maintaining their positional relationship. Therefore, in this embodiment, the transfer to the temporary substrate ( Fig.15c 131) process.

[0171] Then, as referenced Figure 15e to Figure 15i As described above, the light emitting element 100 can be transferred to the circuit substrate 101 .

[0172] Fig.17a and Fig.17b is a schematic cross-sectional view for explaining a method of transferring a light emitting element to a circuit substrate according to still another embodiment of the present disclosure.

[0173] Although in the above embodiments, the first LED stack 23, the second LED stack 33, and the third LED stack 43 formed on the substrate 41 are separated into light-emitting element regions in advance by forming separation grooves through an isolation process and then a laser scribing process is performed, the isolation process can be omitted, and the light-emitting element regions can also be formed by scribing and cracking. Fig.17a and Fig.17b This is a cross-sectional view for explaining a method of transferring the light emitting element 200 from a wafer formed without going through an isolation step to the circuit substrate 101 .

[0174] Reference Fig.17a, a wafer having the first LED stack 23, the second LED stack 33, and the third LED stack 43 stacked on the substrate 41 is provided through the steps described in the above-described method for manufacturing the light emitting element 100, except that the isolation step is not performed. A plurality of light emitting elements 200 are formed on the substrate 41, and a protruding pad is arranged corresponding to each light emitting element.

[0175] Next, laser scribing is used to form scribing grooves on the wafer. The scribing grooves may be formed to penetrate at least a portion of the first LED stack 23 , the second LED stack 33 , and the third LED stack 43 , and may also be formed on a portion of the upper surface of the substrate 41 .

[0176] Reference Fig.17b After the scribe line is formed, the substrate 41 is attached to the cleavage tape 121, as shown in FIG. Fig.15b As described above, the splitting is performed using a blade. Figure 15c to Figure 15i The described process transfers the light emitting element 200 onto the circuit board 101 .

[0177] Although the present embodiment is described with respect to an embodiment that undergoes all laser scribing and cracking processes, Fig.16a and Fig.16b As described above, the light emitting element 200 can be separated by laser scribing, and thus the splitting process can be omitted.

[0178] Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Furthermore, matters or components described in one embodiment may be applied to other embodiments without departing from the technical concept of the present invention.

Claims

1. A light emitting element, comprising: substrate; A first LED stack, a second LED stack and a third LED stack are arranged on the substrate; The raised pads and the common raised pads are arranged on one side of the first LED stack, the second LED stack and the third LED stack respectively; as well as A plurality of transparent electrodes are respectively arranged on one side of the first LED stack, the second LED stack and the third LED stack, Each of the first LED stack, the second LED stack and the third LED stack includes a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer. The plurality of transparent electrodes include: A second transparent electrode is arranged on the upper surface of the second LED stack and is in electrical contact with the second conductive semiconductor layer of the second LED stack; and A third transparent electrode is arranged on the upper surface of the third LED stack and is in electrical contact with the second conductive semiconductor layer of the third LED stack. wherein the side surface of the second transparent electrode is recessed inwardly than the side surface of the second conductive semiconductor layer of the second LED stack and / or the side surface of the third transparent electrode is recessed inwardly than the side surface of the second conductive semiconductor layer of the third LED stack, The second LED stack is arranged between the first LED stack and the third LED stack. The common protruding pad is electrically connected to the first conductive semiconductor layer of the first LED stack to the third LED stack. Wherein, the raised pad comprises: a first protruding pad electrically connected to the second conductive semiconductor layer of the first LED stack; a second protruding pad electrically connected to the second conductive semiconductor layer of the second LED stack; and The third protruding pad is electrically connected to the second conductive semiconductor layer of the third LED stack.

2. The light emitting element according to claim 1, further comprising: An n electrode pad is arranged on the first conductive semiconductor layer of the third LED stack; a lower p-electrode pad arranged on a third transparent electrode arranged on the upper surface of the third LED stack, The upper surface of the n-electrode pad is located at the same height as the upper surface of the lower p-electrode pad.

3. The light-emitting element according to claim 2, wherein The third transparent electrode is partially removed along the edge of the third LED stack. A bottom side of the third transparent electrode is not exposed to the outside.

4. The light-emitting element according to claim 3, wherein An upper surface of the n-electrode pad is higher than an upper surface of the third transparent electrode.

5. The light-emitting element according to claim 3, wherein The thickness of the lower p-electrode pad is the same as the thickness of a portion of the n-electrode pad that protrudes above the third transparent electrode.

6. The light emitting element according to claim 2, further comprising: The lower insulating layer is arranged on the second LED stack and covers at least a region of the second transparent electrode.

7. The light-emitting element according to claim 6, wherein The recessed area of ​​the second transparent electrode is filled with the lower insulating layer.

8. The light emitting element according to claim 6, wherein The lower insulating layer includes an opening exposing the first conductive type semiconductor and the second transparent electrode.

9. The light-emitting element according to claim 8, wherein The width of the opening is smaller than the width of the lower p-electrode pad.

10. The light emitting element according to claim 6, wherein The lower insulating layer includes a through hole penetrating through the second LED stack to expose the n-electrode pad and the lower p-electrode pad.

11. The light emitting element according to claim 10, wherein The through hole is formed in the mesa etching region and has a stepped sidewall.

12. The light emitting element according to claim 11, wherein The lower insulating layer covers at least a region of the stepped sidewall of the through hole.

13. The light emitting element according to claim 6, further comprising: The middle insulating layer covers the side surfaces from the first LED stack to the third LED stack.

14. The light emitting element according to claim 13, further comprising: The upper insulating layer covers the upper surface of the middle insulating layer.

15. The light emitting element according to claim 14, wherein The upper insulating layer is formed to be thinner than the intermediate insulating layer.

16. The light emitting element according to claim 14, wherein The raised pad and the common raised pad are electrically connected to the first semiconductor layer and the second semiconductor layer of the first to third LED stacks through the openings of the upper insulating layer.

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