Micro light emitting diode, preparation method thereof and light emitting device
By symmetrically arranging mesa and bridging structures on the same side in the micro LED, the breakage problem caused by the asymmetry of the bridging structure is solved, the stability and wet etching uniformity of the micro LED are improved, and its reliability is enhanced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- QUANZHOU SANAN SEMICON TECH CO LTD
- Filing Date
- 2021-12-31
- Publication Date
- 2026-07-24
AI Technical Summary
During the fabrication of micro LEDs, the precision limitations of the exposure equipment can lead to misalignment between the first and second stage surfaces, asymmetrical bridging structures, and uneven stress distribution. This can easily cause bridging structure breakage and epitaxial structure detachment, affecting reliability.
By configuring the first and second mesa on the same side in the micro light-emitting diode, making them have the same width in a preset direction, and symmetrically arranging bridging structures in this direction, the stress is ensured to be evenly distributed, avoiding breakage problems. At the same time, the wet etching process is improved to enhance uniformity.
This improved the stability of the bridging structure, enhanced the reliability of the micro LED and the uniformity of the wet etching process, and avoided the fracture and sacrificial layer residue caused by uneven stress in the bridging structure.
Smart Images
Figure CN116417546B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor-related technologies, and in particular to a micro light-emitting diode and its fabrication method and light-emitting device. Background Technology
[0002] Micro light-emitting diodes (LEDs) have advantages such as low power consumption, high brightness, ultra-high resolution and color saturation, fast response speed and long lifespan, making them a popular next-generation display technology currently under research.
[0003] The traditional fabrication method for micro-LEDs involves firstly fabricating a first mesa and a second mesa surrounding the first mesa on an epitaxial structure, with the first mesa protruding above the second mesa; then, a bridging structure is formed between the first and second mesa. As the size of micro-LEDs decreases, the precision limitations of the exposure equipment make alignment deviations prone to occur during the fabrication of the first and second mesa. This leads to asymmetry between the first mesa and the second mesa on opposite sides, resulting in an asymmetrical bridging structure. Due to these alignment deviations, the stress distribution within the micro-LED is uneven, potentially causing problems such as breakage of the bridging structure. In severe cases, the epitaxial structure may even detach from the bridging structure. Summary of the Invention
[0004] The purpose of this application is to provide a micro light-emitting diode, which arranges the bridging structure symmetrically on the first or second platform in a preset direction, and ensures that the stress of the micro light-emitting diode is uniformly distributed in the preset direction, thereby avoiding the fracture problem of the bridging structure due to uneven stress distribution and improving the stability of the bridging structure.
[0005] Another objective is to provide a method for fabricating a micro light-emitting diode and a light-emitting device.
[0006] In a first aspect, embodiments of this application provide a micro light-emitting diode, which includes:
[0007] The extension structure is provided with a first platform and a second platform, both of which are located on the same side of the extension structure and have a height difference; the first platform and the second platform have the same width in a preset direction, and the center points of the first platform and the second platform in the preset direction are located on the same axis extending in a direction perpendicular to the preset direction.
[0008] The bridging structure includes at least a first bridging layer, which is formed on a first tabletop and a second tabletop, and is symmetrically arranged on the first tabletop and / or the second tabletop in the aforementioned preset direction.
[0009] In one possible implementation, the widths of the first and second platforms in the aforementioned preset direction are both equal to the width of the extension structure in the aforementioned preset direction.
[0010] In one possible implementation, the first bridging layer extends beyond the epitaxial structure in the aforementioned predetermined direction.
[0011] In one possible implementation, the surface of the first bridging layer that contacts the first and second countertops is configured as a plane in the aforementioned preset direction.
[0012] In one possible implementation, the epitaxial structure includes a first semiconductor layer, an active layer, and a second semiconductor layer arranged in sequence; a first mesa is configured as the surface of the first semiconductor layer, a second mesa exposes the second semiconductor layer, and the height of the first mesa is greater than the height of the second mesa.
[0013] In one possible implementation, the micro-light-emitting diode further includes:
[0014] The first electrode is symmetrically arranged on the first platform in the aforementioned preset direction;
[0015] The second electrode is symmetrically arranged on the second platform in the aforementioned preset direction.
[0016] In one possible implementation, the first bridging layer is symmetrical about the first electrode and / or the second electrode in the aforementioned preset direction.
[0017] In one possible implementation, the micro-light-emitting diode further includes:
[0018] The first pad is formed on the side of the first bridging layer away from the epitaxial structure and is electrically connected to the first electrode.
[0019] The second pad is formed on the side of the first bridging layer away from the epitaxial structure and is electrically connected to the second electrode.
[0020] In one possible implementation, the micro-light-emitting diode further includes:
[0021] A sacrificial layer is formed on the side of the first bridging layer away from the epitaxial structure, and covers the lower surface of the first bridging layer, as well as the lower surfaces and sidewalls of the first pad and the second pad; in the aforementioned predetermined direction, the portion of the sacrificial layer that does not correspond to the epitaxial structure in the vertical direction is provided with an opening, and the opening exposes the first bridging layer.
[0022] A bonding layer is formed on the side of the sacrificial layer away from the first bridging layer; the bonding layer fills the opening and contacts the first bridging layer;
[0023] The substrate is located on the side of the bonding layer away from the first bridging layer.
[0024] In one possible implementation, the surface of the sacrificial layer that contacts the first bridging layer is configured as a plane in the aforementioned preset direction.
[0025] In one possible implementation, the bridging structure further includes a second bridging layer that covers the surface of the epitaxial structure away from the first mesa, as well as the sidewalls of the epitaxial structure.
[0026] In one possible implementation, the micro-light-emitting diode includes an epitaxial structure; or, the micro-light-emitting diode includes a plurality of epitaxial structures arranged at intervals.
[0027] In one possible implementation, the emission wavelength of the micro LED is 400 nm to 950 nm.
[0028] In one possible implementation, the first and second platforms are located on opposite sides of the epitaxial structure and are respectively aligned with the opposite side edges of the epitaxial structure.
[0029] Secondly, embodiments of this application provide a method for fabricating a micro light-emitting diode, which includes the following steps:
[0030] An epitaxial structure is formed; the epitaxial structure has a length direction and a width direction.
[0031] The epitaxial structure is etched to form a trench extending into the epitaxial structure. The width of the trench is the same as the width of the epitaxial structure. The bottom surface of the trench is the second mesa, and the surface of the epitaxial structure facing the same direction as the second mesa is the first mesa.
[0032] A first bridging layer is formed on the first and second countertops;
[0033] The epitaxial structure is etched from the side of the epitaxial structure away from the first bridging layer, and the width of the first mesa and the second mesa are the same. The center points of the first mesa and the second mesa in the width direction are located on the same axis extending in the length direction. The first bridging layer is symmetrically arranged on the first mesa and / or the second mesa in the width direction.
[0034] In one possible implementation, the widths of both the first and second platforms are equal to the width of the extension structure.
[0035] In one possible implementation, the first bridging layer extends beyond the epitaxial structure in the width direction.
[0036] In one possible implementation, after forming the first bridging layer on the first mesa and the second mesa, before etching the epitaxial structure on the side of the epitaxial structure away from the first bridging layer, the method further includes:
[0037] A sacrificial layer is deposited on the first bridging layer;
[0038] The sacrificial layer is bonded to the substrate via a bonding layer.
[0039] Thirdly, embodiments of this application provide a light-emitting device that utilizes the micro light-emitting diodes described in the above embodiments.
[0040] Compared with the prior art, this application has at least the following beneficial effects:
[0041] The epitaxial structure is configured with a first mesa and a second mesa located on the same side. The first and second mesa have the same width in a predetermined direction, and the center points of the first and second mesa in the predetermined direction are located on the same axis extending in a direction perpendicular to the predetermined direction. The bridging structure is symmetrically arranged on the first or second mesa in the predetermined direction, which can ensure that the stress of the micro-light-emitting diode is uniformly distributed in the predetermined direction, avoid the fracture problem caused by uneven stress distribution of the bridging structure, improve the stability of the bridging structure, and thus improve the reliability of the micro-light-emitting diode. Attached Figure Description
[0042] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0043] Figure 1 A top view of a micro light-emitting diode in the prior art;
[0044] Figure 2a This is a schematic diagram of the AA cross-section of a micro light-emitting diode in the prior art;
[0045] Figures 2b to 2g This is a schematic diagram of the BB cross-section of a micro light-emitting diode at different fabrication stages in the prior art.
[0046] Figures 3a to 3d This is a top view illustrating a micro light-emitting diode at different fabrication stages according to embodiments of this application;
[0047] Figures 4a to 4g This is a schematic diagram of cross-section AA of a micro light-emitting diode at different fabrication stages according to an embodiment of this application;
[0048] Figures 5a to 5f This is a schematic diagram of the BB cross-section of a micro light-emitting diode at different fabrication stages according to an embodiment of this application.
[0049] Illustration:
[0050] 10 substrates 100 substrates
[0051] 20 Epitaxial Structures 200 Epitaxial Structures
[0052] 20-1 First Semiconductor Layer 210 First Semiconductor Layer
[0053] 20-2 Active Layer 220 Active Layer
[0054] 20-3 Second semiconductor layer 230 Second semiconductor layer
[0055] 21 First countertop 201 First countertop
[0056] 22 Second countertop 202 Second countertop
[0057] 30 First electrode 300 First electrode
[0058] 31 Second electrode 310 Second electrode
[0059] 40 Bridging Structure 400 Bridging Structure
[0060] 41 First bridging layer 410 First bridging layer
[0061] 42 Second bridging layer 420 Second bridging layer
[0062] 50 First pad 500 First pad
[0063] 51 Second pad 510 Second pad
[0064] 60 Sacrifice Layers 600 Sacrifice Layers
[0065] 70 bonding layer 700 bonding layer
[0066] 80 substrate800 substrate Detailed Implementation
[0067] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or operated through other different specific embodiments, and various details in this application can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application.
[0068] In the description of this application, it should be noted that the terms "upper" and "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first" and "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0069] Figure 1 This is a top view of a microlight-emitting diode (LED) in the prior art. The fabrication method of this microlight-emitting diode includes the following steps:
[0070] S1. Provide an epitaxial structure 20, and simultaneously fabricate a first mesa 21 and a second mesa 22 on the epitaxial structure 20.
[0071] like Figure 2a and 2b As shown, an epitaxial structure 20 is formed on a substrate 10. The epitaxial structure 20 includes a first semiconductor layer 20-1, an active layer 20-2, and a second semiconductor layer 20-3 arranged sequentially from top to bottom. The epitaxial structure 20 is etched, and a first mesa 21 and a second mesa 22 are formed on the epitaxial structure 20. The first mesa 21 is the upper surface of the first semiconductor layer 20-1, and the second mesa 22 surrounds the periphery of the first mesa 21 and exposes the second semiconductor layer 20-3.
[0072] As the size of existing micro LEDs becomes smaller and smaller, under the precision limitations of the exposure equipment, alignment deviations are prone to occur when manufacturing the first stage 21 and the second stage 22. That is, the second stage 22 is not symmetrical about the first stage 21 in the BB cross-section direction. In other words, the width of the second stage 22 on both sides of the first stage 21 is inconsistent in the BB cross-section direction, which will affect the reliability of the micro LED.
[0073] S2, such as Figure 2a and 2b As shown, a first electrode 30 is formed on the first mesa 21 and is electrically connected to the first semiconductor layer 20-1; a second electrode 31 is formed on the second mesa 22 and is electrically connected to the second semiconductor layer 20-3.
[0074] S3, such as Figure 2c As shown, a first bridging layer 41 is formed on the first mesa 21 and the second mesa 22, exposing the first electrode 30 and the second electrode 31. In the BB cross-sectional direction, the widths of the first bridging layer 41 on both sides of the first mesa 21 are inconsistent.
[0075] Because the widths of the second mesa 22 on both sides of the first mesa 21 are inconsistent, the stress distribution in the micro-light-emitting diode is uneven, which can easily cause the first bridging layer 41 on both sides of the first mesa 21 to break, or even cause the epitaxial structure 20 to fall off from the first bridging layer 41, seriously affecting the reliability of the micro-light-emitting diode.
[0076] S4, such as Figure 2d As shown, a first pad 50 is formed on the first platform 21 and is electrically connected to the first electrode 30; a second pad 51 is formed on the second platform 22 and is electrically connected to the second electrode 31.
[0077] S5, such as Figure 2e As shown, the first pad 50 and the second pad 51 are bonded to the substrate 80. Specifically, a sacrificial layer 60 is formed on the first bridging layer 41, the first pad 50, and the second pad 51, and the sacrificial layer 60 is bonded to the substrate 80 through a bonding layer 70. The sacrificial layer 60 is preferably a TiW film or other film layers that are easily removed by a wet etching process. The bonding layer 70 can be any bonding agent, which is preferably a benzocyclobutene coating layer.
[0078] In the BB cross-section direction, there are multiple inflection points on the surface where the sacrificial layer 60 contacts the first bridging layer 41. When the sacrificial layer 60 is removed using a wet etching process, the uniformity of the wet etching is poor, and the sacrificial layer 60 is prone to remain.
[0079] S6, such as Figure 2f As shown, the substrate 10 is removed and the epitaxial structure 20 is etched.
[0080] S7, such as Figure 2g As shown, a second bridging layer 42 is formed on the side surface of the epitaxial structure 20 away from the first mesa 21 and on the sidewall of the epitaxial structure 20. The second bridging layer 42 and the first bridging layer 41 together form the bridging structure 40.
[0081] Based on the above, it is evident that when fabricating micro-LEDs using existing processes, due to the limitations of the exposure equipment's precision, the widths of the second mesa 22 on both sides of the first mesa 21 are inconsistent in the BB cross-section direction. Furthermore, the widths of the first bridging layer 41 on both sides of the first mesa 21 are also inconsistent, resulting in uneven stress distribution within the micro-LED. This can easily lead to problems such as breakage of the first bridging layer 41 on both sides of the first mesa 21. In severe cases, this can cause the epitaxial structure 20 to detach from the first bridging layer 41, affecting the reliability of the micro-LED. Additionally, the surface where the sacrificial layer 60 contacts the first bridging layer 41 has multiple inflection points. When removing the sacrificial layer 60 using a wet etching process, the uniformity of the wet etching is poor, easily resulting in sacrificial layer 60 residue.
[0082] To address the aforementioned technical problems, the inventors employed a novel fabrication process to prepare micro-light-emitting diodes (LEDs). In this micro-LED, the first and second mesa have the same width along the bottom-bulb (BB) cross-section, allowing the bridging structure to be symmetrically arranged on either the first or second mesa along the BB cross-section. This ensures a uniform stress distribution within the micro-LED along the BB cross-section, preventing breakage due to uneven stress distribution and improving the stability of the bridging structure. Furthermore, the absence of an inflection point at the contact between the sacrificial layer and the first bridging layer facilitates wet etching, improving etching uniformity and preventing sacrificial layer residue.
[0083] According to one aspect of this application, a micro light-emitting diode is provided. A micro light-emitting diode mainly refers to a micrometer-scale light-emitting diode, whose minimum size, that is, its minimum width and minimum length, ranges from 0.5 to 5 μm, 5 to 10 μm, 10 to 20 μm, 20 to 50 μm, or 50 to 100 μm.
[0084] See Figure 3d , Figure 4g and Figure 5f The micro light-emitting diode includes an epitaxial structure 200 and a bridging structure 400. The number of epitaxial structures 200 is one or more, and when there are multiple epitaxial structures 200, the multiple epitaxial structures are arranged at intervals.
[0085] The epitaxial structure 200 is configured with a first mesa 201 and a second mesa 202. Both the first mesa 201 and the second mesa 202 are located on the same side of the epitaxial structure 200 and have a height difference. The first mesa 201 and the second mesa 202 have the same width in a predetermined direction, and the center points of the first mesa 201 and the second mesa 202 in the predetermined direction are located on the same axis extending perpendicular to the predetermined direction. It should be noted that the predetermined direction mentioned in this document refers to the BB cross-sectional direction of the micro-light-emitting diode, which is also... Figure 3d The direction in which the BB line is located.
[0086] The bridging structure 400 includes at least a first bridging layer 410, which is formed on a first mesa 201 and a second mesa 202. In the aforementioned predetermined direction, i.e., in the BB cross-sectional direction, the first bridging layer 410 is symmetrically arranged on the first mesa 201 and / or the second mesa 202. The stress of the micro-light-emitting diode is uniformly distributed in the aforementioned BB cross-sectional direction to avoid breakage of the first bridging layer 410 and the bridging structure 400 due to uneven stress distribution, thereby improving the stability of the first bridging layer 410 and the bridging structure 400.
[0087] In one implementation, see Figure 3dThe first platform 201 and the second platform 202 have the same width in the aforementioned preset direction, and both are D. The value of D is preferably equal to the width of the extension structure 200 in the aforementioned preset direction.
[0088] like Figure 5f As shown, by configuring the first mesa 201 and the second mesa 202 in the aforementioned structure, the first bridging layer 410 can be horizontally contacted with either the first mesa 201 or the second mesa 202 in the aforementioned preset direction. In other words, the first bridging layer 410 will not have an inflection point when it contacts the first mesa 201 or the second mesa 202 in the aforementioned preset direction, thus improving the stability of the first bridging layer 410 and the bridging structure 400. Simultaneously, it can also improve the uniformity of stress distribution of the micro-light-emitting diode in the aforementioned preset direction.
[0089] Preferably, the upper and lower surfaces of the first bridging layer 410 in the aforementioned preset direction are both configured as planes.
[0090] Preferably, the first bridging layer 410 extends beyond the epitaxial structure 200 in the aforementioned predetermined direction. The width of the first bridging layer 410 extending beyond the epitaxial structure 200 is 1.5 μm to 5 μm, and preferably 2 μm to 3 μm.
[0091] In one implementation, see Figure 4g and Figure 5f The epitaxial structure 200 comprises, from bottom to top, a first semiconductor layer 210, an active layer 220, and a second semiconductor layer 230 arranged sequentially. The first semiconductor layer 210 is an N-type semiconductor layer, the active layer 220 is a multilayer quantum well layer, and the second semiconductor layer 230 is a P-type semiconductor layer. The N-type semiconductor layer, the multilayer quantum well layer, and the P-type semiconductor layer are only the basic building blocks of the epitaxial structure 200. Based on this, the epitaxial structure 200 may also include other functional structural layers that optimize the performance of the micro-light-emitting diode. In this embodiment, the emission wavelength of the micro-light-emitting diode is 400nm to 950nm, and the micro-light-emitting diode is preferably a red light-emitting diode. The material of the epitaxial structure 200 includes, but is not limited to, aluminum gallium arsenide, gallium arsenide phosphide, aluminum gallium indium phosphide, or gallium phosphide.
[0092] Preferably, the first mesa 201 is configured as the lower surface of the first semiconductor layer 210, the second mesa 202 exposes the second semiconductor layer 230, and the height of the first mesa 201 is greater than the height of the second mesa 202.
[0093] Preferably, the surface of the epitaxial structure 200 that is away from the first mesa 201 and the second mesa 202 is the light-emitting surface of the micro-LED. In order to improve the light-emitting efficiency of the micro-LED, the light-emitting surface is preferably a surface formed by roughening treatment.
[0094] Preferably, the first mezzanine 201 and the second mezzanine 202 are located on opposite sides of the extension structure 200 and are aligned with the opposite side edges of the extension structure 200, respectively. For example, in the AA section direction, the first mezzanine 201 and the second mezzanine 202 are located at the two ends of the extension structure 200 and are aligned with the edges of the corresponding ends, respectively.
[0095] In one embodiment, the first bridging layer 410 includes, but is not limited to, a single-layer insulating layer or a distributed Bragg reflector. When the first bridging layer 410 is a single-layer insulating layer, the material of the first bridging layer 410 includes, but is not limited to, silicon oxide, silicon nitride, titanium oxide, aluminum oxide, or magnesium fluoride.
[0096] When the first bridging layer 410 is a distributed Bragg reflector, the material of the first bridging layer 410 is at least two of different materials such as SiO2, TiO2, ZnO2, ZrO2, and Cu2O3. Specifically, the first bridging layer 410 includes a distributed Bragg reflector made by using techniques such as electron beam evaporation or ion beam sputtering to stack two materials in alternating and repeated layers.
[0097] In one implementation, see Figure 3d , Figure 4g and Figure 5f The micro light-emitting diode also includes a first electrode 300 and a second electrode 310. The first electrode 300 is formed on the first mesa 201 and electrically connected to the first semiconductor layer 210; the second electrode 310 is formed on the second mesa 202 and electrically connected to the second semiconductor layer 230.
[0098] Preferably, the first electrode 300 is symmetrically arranged on the first platform 201 in the aforementioned preset direction. The second electrode 310 is symmetrically arranged on the second platform 202 in the aforementioned preset direction.
[0099] Preferably, the first bridging layer 410 exposes the first electrode 300 and the second electrode 310. In the aforementioned predetermined direction, the first bridging layer 410 is symmetrical about the first electrode 300 and / or the second electrode 310.
[0100] In one implementation, see Figure 3d , Figure 4g and Figure 5f The micro LED also includes a first pad 500 and a second pad 510. The first pad 500 is formed on the side of the first bridging layer 410 away from the epitaxial structure 200 and is electrically connected to the first electrode 300; the second pad 510 is formed on the side of the first bridging layer 410 away from the epitaxial structure 200 and is electrically connected to the second electrode 310.
[0101] Preferably, the lower surfaces of the first pad 500 and the second pad 510 are at the same height.
[0102] In one implementation, see Figure 4g and Figure 5f The micro light-emitting diode also includes a sacrificial layer 600, a bonding layer 700, and a substrate 800.
[0103] A sacrificial layer 600 is formed on the side of the first bridging layer 410 away from the epitaxial structure 200, and covers the lower surface of the first bridging layer 410, as well as the lower surfaces and sidewalls of the first pad 500 and the second pad 510. In the aforementioned predetermined direction, an opening is provided in the portion of the sacrificial layer 600 that does not correspond vertically to the epitaxial structure 200, and this opening exposes the first bridging layer 410. The sacrificial layer 600 is preferably a TiW film or other film that is easily removed by a wet etching process. In the aforementioned predetermined direction, the surface of the sacrificial layer 600 in contact with the first bridging layer 410 is configured as a plane, meaning that there is no inflection point when the sacrificial layer 600 contacts the first bridging layer 410, facilitating the wet etching process, improving the uniformity of wet etching, and avoiding the occurrence of sacrificial layer 600 residue.
[0104] A bonding layer 700 is formed on the side of the sacrificial layer 600 away from the first bridging layer 410. The bonding layer 700 fills the openings in the sacrificial layer 600 and contacts the first bridging layer 410. The bonding layer 700 can be any bonding agent, but it is preferably a benzocyclobutene coating layer.
[0105] The substrate 800 is located on the side of the bonding layer 700 away from the first bridging layer 410. The substrate 800 includes, but is not limited to, a sapphire substrate, glass, a silicon substrate or a silicon carbide substrate.
[0106] In one implementation, see Figure 4g and Figure 5f The bridging structure 400 also includes a second bridging layer 420, which covers the surface of the extension structure 200 away from the first mesa 201 and the second mesa 202, as well as the sidewall of the extension structure 200.
[0107] The second bridging layer 420 includes, but is not limited to, a single-layer insulating layer or a distributed Bragg reflector. When the second bridging layer 420 is a single-layer insulating layer, the material of the second bridging layer 420 includes, but is not limited to, silicon oxide, silicon nitride, titanium oxide, aluminum oxide, or magnesium fluoride. When the second bridging layer 420 is a distributed Bragg reflector, the material of the second bridging layer 420 is at least two of different materials such as SiO2, TiO2, ZnO2, ZrO2, and Cu2O3. Specifically, the second bridging layer 420 includes a distributed Bragg reflector fabricated by using techniques such as electron beam evaporation or ion beam sputtering to alternately and repeatedly stack two materials into multiple layers.
[0108] According to one aspect of this application, a method for fabricating a micro light-emitting diode is provided. The method includes the following steps:
[0109] S10, forming an epitaxial structure 200; the epitaxial structure 200 has a length direction and a width direction.
[0110] like Figure 3a , Figure 4a and Figure 5a As shown, a substrate 100 is provided, which includes, but is not limited to, a gallium arsenide substrate. An epitaxial structure 200 is formed on the substrate 100, comprising, from top to bottom, a first semiconductor layer 210, an active layer 220, and a second semiconductor layer 230 arranged sequentially. The first semiconductor layer 210 is an N-type semiconductor layer, the active layer 220 is a multilayer quantum well layer, and the second semiconductor layer 230 is a P-type semiconductor layer. In this embodiment, the micro-light-emitting diode is preferably a red light-emitting diode, and the material of the epitaxial structure 200 includes, but is not limited to, aluminum gallium arsenide, gallium arsenide phosphide, aluminum gallium indium phosphide, or gallium phosphide. The length direction of the epitaxial structure 200 is the AA cross-sectional direction, and the width direction of the epitaxial structure 200 is the BB cross-sectional direction.
[0111] S20. A first electrode 300 is formed on the upper surface of the epitaxial structure 200.
[0112] like Figure 3a , Figure 4a and Figure 5a As shown, the upper surface of the epitaxial structure 200 is the subsequent first mesa 201, and the first electrode 300 is formed on the upper surface of the epitaxial structure 200 and is electrically connected to the first semiconductor layer 210.
[0113] S30. Etch the epitaxial structure 200 and form a trench extending into the interior of the epitaxial structure 200. The width of the trench is the same as the width of the epitaxial structure 200. The bottom surface of the trench is the second mesa 202. The surface of the epitaxial structure 200 that faces the same direction as the second mesa 202 is the first mesa 201.
[0114] like Figure 3b , Figure 4b and Figure 5a As shown, the epitaxial structure 200 is etched downwards from its upper surface, forming a trench in the epitaxial structure 200. This trench extends a predetermined length 'a' in the AA cross-sectional direction and a predetermined width 'b' in the BB cross-sectional direction, with the width 'b' preferably equal to the width of the epitaxial structure 200 in the BB cross-sectional direction. This trench exposes a second semiconductor layer 230, and the bottom surface of the trench is configured as a second mesa 202. The upper surface of the epitaxial structure 200 is configured as a first mesa 201.
[0115] S40, A second electrode 310 is formed on the second mesa 202.
[0116] like Figure 3b , Figure 4b and Figure 5a As shown, the second electrode 310 is electrically connected to the second semiconductor layer 230.
[0117] S50, a first bridging layer 410 is formed on the first platform 201 and the second platform 202; the first bridging layer 410 is in horizontal contact with the first platform 201 or the second platform 202 in the BB cross section direction.
[0118] like Figure 3b , Figure 4c and Figure 5b As shown, a first bridging layer 410 is formed on the upper surface of the epitaxial structure 200 and at the trench, exposing the first electrode 300 and the second electrode 310. The first bridging layer 410 includes, but is not limited to, a single-layer insulating layer or a distributed Bragg reflector. When the first bridging layer 410 is a single-layer insulating layer, the material of the first bridging layer 410 includes, but is not limited to, silicon oxide, silicon nitride, titanium oxide, aluminum oxide, or magnesium fluoride.
[0119] When the first bridging layer 410 is a distributed Bragg reflector, the material of the first bridging layer 410 is at least two of different materials such as SiO2, TiO2, ZnO2, ZrO2, and Cu2O3. Specifically, the first bridging layer 410 includes a distributed Bragg reflector made by using techniques such as electron beam evaporation or ion beam sputtering to stack two materials in alternating and repeated layers.
[0120] S60. A first pad 500 and a second pad 510 are formed on the side of the first bridging layer 410 away from the epitaxial structure 200. The first pad 500 is electrically connected to the first electrode 300, and the second pad 510 is electrically connected to the second electrode 310. The epitaxial structure 200 is bonded to the substrate 800.
[0121] like Figure 3c , Figure 4d and Figure 5c As shown, a first pad 500 is formed on the side of the first bridging layer 410 away from the epitaxial structure 200 and is electrically connected to the first electrode 300; a second pad 510 is formed on the side of the first bridging layer 410 away from the epitaxial structure 200 and is electrically connected to the second electrode 310. The upper surfaces of the first pad 500 and the second pad 510 are at the same height.
[0122] like Figure 4e and Figure 5dAs shown, a sacrificial layer 600 is deposited on the first bridging layer 410, the first pad 500, and the second pad 510, and then the sacrificial layer 600 is bonded to the substrate 800 via a bonding layer 700. The sacrificial layer 600 is preferably a TiW film or other film layers that are easily removed by wet etching processes. The material of the bonding layer 700 can be any bonding agent, which is preferably a benzocyclobutene coating layer. The substrate 800 includes, but is not limited to, a sapphire substrate, glass, a silicon substrate, or a silicon carbide substrate.
[0123] In the BB cross-sectional direction, the sacrificial layer 600 is provided with an opening that exposes the first bridging layer 410, and the bonding layer 700 fills the opening and contacts the first bridging layer 410.
[0124] In the BB cross-section direction, the surface where the sacrificial layer 600 contacts the first bridging layer 410 is configured as a plane, meaning that there will be no inflection point when the sacrificial layer 600 contacts the first bridging layer 410, which facilitates the wet etching process, improves the uniformity of wet etching, and avoids the phenomenon of sacrificial layer 600 residue.
[0125] S70. The epitaxial structure 200 is etched on the side of the epitaxial structure 200 away from the first bridging layer 410, and the widths of the first mesa 201 and the second mesa 202 are the same. The center points of the first mesa 201 and the second mesa 202 in the width direction are located on the same axis extending in the length direction. The first bridging layer 410 is symmetrically arranged on the first mesa 201 and / or the second mesa 202 in the width direction.
[0126] like Figure 3d , Figure 4f and Figure 5e As shown, the substrate 100 is removed and roughened, and the epitaxial structure 200 is etched from the side of the epitaxial structure 200 away from the first bridging layer 410. After etching, the width of the first mesa 201 and the second mesa 202 in the BB section direction is the same, and the center points of the first mesa 201 and the second mesa 202 in the BB section direction are located on the same axis extending in a direction perpendicular to the BB section direction.
[0127] Preferably, the first platform 201 and the second platform 202 have the same width in the BB section direction, and both are D. The value of D is preferably equal to the width of the extension structure 200 in the BB section direction.
[0128] Preferably, the first mezzanine 201 and the second mezzanine 202 are located on opposite sides of the extension structure 200 and are aligned with the opposite side edges of the extension structure 200, respectively. For example, in the AA section direction, the first mezzanine 201 and the second mezzanine 202 are located at the two ends of the extension structure 200 and are aligned with the edges of the corresponding ends, respectively.
[0129] Preferably, the first bridging layer 410 extends beyond the epitaxial structure 200 in the BB cross-section direction. The width of the first bridging layer 410 extending beyond the epitaxial structure 200 is 1.5 μm to 5 μm, and preferably 2 μm to 3 μm.
[0130] Preferably, in the BB cross-section direction, the first bridging layer 410 is symmetrically arranged on the first platform 201 and / or the second platform 202.
[0131] Preferably, the first electrode 300 is symmetrically arranged on the first mesa 201 in the BB cross-sectional direction. The second electrode 310 is symmetrically arranged on the second mesa 202 in the BB cross-sectional direction.
[0132] S70. A second bridging layer 420 is formed on the surface of the epitaxial structure 200 away from the substrate 800 and on the sidewall of the epitaxial structure 200. The second bridging layer 420 and the first bridging layer 410 together form the bridging structure 400.
[0133] like Figure 4g and Figure 5f As shown, the second bridging layer 420 covers the surface of the epitaxial structure 200 away from the first mesa 201 and the second mesa 202, as well as the sidewalls of the epitaxial structure 200. The second bridging layer 420 includes, but is not limited to, a single-layer insulating layer or a distributed Bragg reflector. When the second bridging layer 420 is a single-layer insulating layer, the material of the second bridging layer 420 includes, but is not limited to, silicon oxide, silicon nitride, titanium oxide, aluminum oxide, or magnesium fluoride. When the second bridging layer 420 is a distributed Bragg reflector, the material of the second bridging layer 420 is at least two of different materials such as SiO2, TiO2, ZnO2, ZrO2, and Cu2O3. Specifically, the second bridging layer 420 includes a distributed Bragg reflector fabricated by using techniques such as electron beam evaporation or ion beam sputtering to alternately and repeatedly stack two materials into multiple layers.
[0134] According to one aspect of this application, a light-emitting device using the micro light-emitting diodes described in the above embodiments is provided. This light-emitting device can be a television, a mobile phone, or an RGB display screen.
[0135] As can be seen from the above technical solution, the epitaxial structure 200 is configured with a first mesa 201 and a second mesa 202 located on the same side. The widths of the first mesa 201 and the second mesa 202 are the same in the preset direction, that is, in the BB section direction, and the center points of the first mesa 201 and the second mesa 202 in the preset direction are located on the same axis extending in a direction perpendicular to the preset direction. The first bridging layer 410 in the bridging structure 400 is symmetrically arranged on the first mesa 201 or the second mesa 202 in the preset direction, which can ensure that the stress of the micro-light-emitting diode is uniformly distributed in the preset direction, avoid the fracture problem of the bridging structure 400 due to uneven stress distribution, improve the stability of the bridging structure 400, and thus improve the reliability of the micro-light-emitting diode.
[0136] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application.
Claims
1. A micro light-emitting diode, characterized in that, include: An extensional structure is provided with a first platform and a second platform, both of which are located on the same side of the extensional structure and have a height difference. The width of the first and second tabletops in the preset direction is equal to the width of the extension structure in the preset direction, and the center points of the first and second tabletops in the preset direction are located on the same axis extending in a direction perpendicular to the preset direction. The bridging structure includes at least a first bridging layer, which is formed on the first tabletop and the second tabletop, and is symmetrically arranged on the first tabletop and / or the second tabletop in the predetermined direction. In the preset direction, the surface of the first bridging layer that contacts the first platform and the second platform is configured as a plane; the first bridging layer includes a single insulating layer or a distributed Bragg reflector.
2. The micro light-emitting diode according to claim 1, characterized in that, The first bridging layer extends beyond the epitaxial structure in the preset direction.
3. The micro light-emitting diode according to claim 1, characterized in that, The epitaxial structure includes a first semiconductor layer, an active layer, and a second semiconductor layer arranged in sequence; the first mesa is configured as the surface of the first semiconductor layer, the second mesa exposes the second semiconductor layer, and the height of the first mesa is greater than the height of the second mesa.
4. The micro light-emitting diode according to any one of claims 1 to 3, characterized in that, Also includes: The first electrode is symmetrically arranged on the first platform in the preset direction; The second electrode is symmetrically arranged on the second platform in the preset direction.
5. The micro light-emitting diode according to claim 4, characterized in that, In the predetermined direction, the first bridging layer is symmetrical about the first electrode and / or the second electrode.
6. The micro light-emitting diode according to claim 4, characterized in that, Also includes: The first pad is formed on the side of the first bridging layer away from the epitaxial structure and is electrically connected to the first electrode. The second pad is formed on the side of the first bridging layer away from the epitaxial structure and is electrically connected to the second electrode.
7. The micro light-emitting diode according to claim 6, characterized in that, Also includes: A sacrificial layer is formed on the side of the first bridging layer away from the epitaxial structure, and covers the lower surface of the first bridging layer, as well as the lower surfaces and sidewalls of the first pad and the second pad; in the predetermined direction, the portion of the sacrificial layer that does not correspond to the epitaxial structure in the vertical direction is provided with an opening, and the opening exposes the first bridging layer; A bonding layer is formed on the side of the sacrificial layer away from the first bridging layer; the bonding layer fills the opening and contacts the first bridging layer; The substrate is located on the side of the bonding layer away from the first bridging layer.
8. The micro light-emitting diode according to claim 7, characterized in that, In the preset direction, the surface of the sacrificial layer that contacts the first bridging layer is configured as a plane.
9. The micro light-emitting diode according to claim 1, characterized in that, The bridging structure further includes a second bridging layer that covers the surface of the extensional structure away from the first platform and the sidewalls of the extensional structure.
10. The micro light-emitting diode according to claim 1, characterized in that, The microlight-emitting diode includes one of the epitaxial structures; or, the microlight-emitting diode includes a plurality of epitaxial structures arranged at intervals.
11. The micro light-emitting diode according to claim 1, characterized in that, The emission wavelength of the micro LED is 400nm~950nm.
12. The micro light-emitting diode according to claim 1, characterized in that, The first and second platforms are located on opposite sides of the epitaxial structure and are respectively aligned with the opposite side edges of the epitaxial structure.
13. A method for fabricating a micro light-emitting diode, characterized in that, include: Formation of extensional structures; The extensional structure has a length direction and a width direction; The epitaxial structure is etched to form a trench extending into the interior of the epitaxial structure. The width of the trench is the same as the width of the epitaxial structure. The bottom surface of the trench is a second mesa. The surface of the epitaxial structure facing the same direction as the second mesa is a first mesa. A first bridging layer is formed on the first and second countertops; The epitaxial structure is etched from the side of the epitaxial structure away from the first bridging layer, and the widths of the first mesa and the second mesa are both equal to the width of the epitaxial structure. The center points of the first mesa and the second mesa in the width direction are located on the same axis extending along the length direction. In the width direction, the first bridging layer is symmetrically arranged on the first mesa and / or the second mesa. In the width direction, the surface of the first bridging layer that contacts the first mesa and the second mesa is configured as a plane. The first bridging layer includes a single insulating layer or a distributed Bragg reflector.
14. The method for fabricating a micro light-emitting diode according to claim 13, characterized in that, The first bridging layer extends beyond the extensional structure in the width direction.
15. The method for fabricating a micro light-emitting diode according to claim 13, characterized in that, Before etching the epitaxial structure on the side of the epitaxial structure away from the first bridging layer, after forming the first bridging layer on the first mesa and the second mesa, the method further includes: A sacrificial layer is deposited on the first bridging layer; The sacrificial layer is bonded to the substrate via a bonding layer.
16. A light-emitting device using a micro light-emitting diode as described in any one of claims 1 to 12.