Micro-LED structure

Abstract

The present invention provides a micro-light-emitting diode structure, comprising an epitaxial structure, a first insulating layer, and a second insulating layer. The epitaxial structure comprises a first-type semiconductor layer, a light-emitting layer, and a second-type semiconductor layer. The first-type semiconductor layer, the light-emitting layer, and the first portion of the second-type semiconductor layer constitute a platform. The platform has a top surface and a first side surface. The second portion of the second-type semiconductor layer is recessed relative to the platform to form a platform surface. The second portion of the second-type semiconductor layer has a second side surface. The first insulating layer covers from the top surface of the platform along the first side surface to the platform surface, exposing the second side surface. The second insulating layer directly covers the second side surface, wherein the thickness ratio of the first insulating layer to the second insulating layer is between 10 and 50.

Description

Technical Field

[0001] The present invention relates to a light-emitting structure, in particular to a micro light-emitting diode structure. Background Art

[0002] In the prior art, the primary manufacturing process for micro-LEDs is performed on an epitaxial substrate. After the process is complete, the epitaxial substrate is removed and transferred to a temporary carrier substrate. During this process, an insulating layer (approximately 0.5 to 1 micron thick) is formed on the surface of the micro-LED for electrical passivation. This insulating layer extends from the top surface of the micro-LED structure along its surrounding surface, covering the surface of the epitaxial substrate. However, due to the thickness of the insulating layer, when a laser lift-off (LLO) process is performed to remove the epitaxial substrate, the epitaxial insulating layer can easily remain on the surrounding surface of the micro-LED after removal, adversely affecting the subsequent manufacturing process. Summary of the Invention

[0003] The present invention is directed to a micro-LED structure that solves the problem in the prior art of residual epitaxial insulating layers on the surrounding surfaces of micro-LEDs after peeling. The structure has better structural reliability and can improve the overall process yield while taking into account luminous efficiency.

[0004] According to an embodiment of the present invention, a micro-light emitting diode structure includes an epitaxial structure, a first insulating layer, and a second insulating layer. The epitaxial structure includes a first-type semiconductor layer, a light-emitting layer, and a second-type semiconductor layer. The light-emitting layer is located between the first-type semiconductor layer and the second-type semiconductor layer. The first-type semiconductor layer, the light-emitting layer, and the first portion of the second-type semiconductor layer constitute a platform. The platform has a top surface and a first side surface. The second portion of the second-type semiconductor layer is recessed relative to the platform to form a platform surface. The second portion of the second-type semiconductor layer has a second side surface. The platform surface is located between the first side surface and the second side surface. The first insulating layer covers from the top surface of the platform along the first side surface to the platform surface, and exposes the second side surface. The second insulating layer directly covers the second side surface, wherein the thickness ratio of the first insulating layer to the second insulating layer is between 10 and 50.

[0005] According to an embodiment of the present invention, a micro-light emitting diode structure includes an epitaxial structure, a first insulating layer, and a second insulating layer. The epitaxial structure includes a first-type semiconductor layer, a light-emitting layer, and a second-type semiconductor layer. The light-emitting layer is located between the first-type semiconductor layer and the second-type semiconductor layer. The first-type semiconductor layer, the light-emitting layer, and the first portion of the second-type semiconductor layer constitute a platform. The platform has a top surface and a first side surface. The second portion of the second-type semiconductor layer is recessed relative to the platform to form a platform surface. The second portion of the second-type semiconductor layer has a second side surface. The platform surface is located between the first side surface and the second side surface. The first insulating layer directly covers from the top surface of the platform along the first side surface to the platform surface, and exposes the second side surface, wherein the first insulating layer covering the first side surface and the second side surface form a continuous surface. The second insulating layer is arranged on the first insulating layer and directly covers the continuous surface, wherein the first insulating layer is in direct contact with the second insulating layer.

[0006] Based on the above, in the design of the micro-LED structure of the present invention, the first insulating layer extends from the top surface of the platform along the first side surface to the platform surface, exposing the second side surface of the second portion of the second-type semiconductor layer. The second insulating layer directly covers this second side surface, with the thickness ratio of the first insulating layer to the second insulating layer ranging from 10 to 50. In other words, the thicker first insulating layer does not extend onto the substrate, solving the problem of residual epitaxial insulating layer on the surrounding surface of the micro-LED after debonding in the prior art. The thinner second insulating layer directly covering the second side surface passivates the second side surface, thereby improving luminous efficiency. Therefore, the micro-LED structure of the present invention achieves improved structural reliability and luminous efficiency, while also improving overall process yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a schematic cross-sectional view of a micro light emitting diode structure according to an embodiment of the present invention;

[0008] Figure 2 is a cross-sectional schematic diagram of a micro light emitting diode structure according to another embodiment of the present invention;

[0009] Figure 3 is a cross-sectional schematic diagram of a micro light emitting diode structure according to another embodiment of the present invention;

[0010] Figure 4 is a cross-sectional schematic diagram of a micro light emitting diode structure according to another embodiment of the present invention;

[0011] Figure 5 is a cross-sectional schematic diagram of a micro light emitting diode structure according to another embodiment of the present invention;

[0012] Figure 6is a cross-sectional schematic diagram of a micro light emitting diode structure according to another embodiment of the present invention;

[0013] Figure 7 is a cross-sectional schematic diagram of a micro light emitting diode structure according to another embodiment of the present invention;

[0014] Figure 8 is a cross-sectional schematic diagram of a micro light emitting diode structure according to another embodiment of the present invention;

[0015] Figure 9 is a cross-sectional schematic diagram of a micro light emitting diode structure according to another embodiment of the present invention;

[0016] Figure 10 FIG. 4 is a cross-sectional schematic diagram of a micro light emitting diode structure according to another embodiment of the present invention.

[0017] Description of Reference Numerals

[0018] 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h, 100i, 100j: micro light emitting diode structures;

[0019] 101:Substrate;

[0020] 110: epitaxial structure;

[0021] 112: first type semiconductor layer;

[0022] 114: light-emitting layer;

[0023] 116: second type semiconductor layer;

[0024] 117: Part I;

[0025] 119: Part II;

[0026] 120a, 120d: first insulating layer;

[0027] 122: First opening;

[0028] 124: Second opening;

[0029] 130a, 130b, 130c, 130d, 130e, 130f, 130g, 130h, 130i, 130j: second insulating layer;

[0030] 131, 133, 135: membrane layer;

[0031] 132e, 132f: third opening;

[0032] 134e, 134f: fourth opening;

[0033] 140a, 140e, 140f, 140h: first electrodes;

[0034] 150a, 150d, 150e, 150f, 150h: second electrodes;

[0035] 160: current distribution layer;

[0036] 170: through hole;

[0037] B: bottom surface;

[0038] CS: continuous surface;

[0039] D: platform surface;

[0040] G: distance;

[0041] H: height;

[0042] M: platform;

[0043] P: plane;

[0044] S1: first side surface;

[0045] S2, S2': second side surface;

[0046] T, T1, T2: thickness;

[0047] U: Top surface. DETAILED DESCRIPTION

[0048] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.

[0049] Figure 1 is a cross-sectional view of a micro-LED structure according to an embodiment of the present invention. Figure 1In this embodiment, the micro-LED structure 100a includes an epitaxial structure 110, a first insulating layer 120a, and a second insulating layer 130a. The epitaxial structure 110 may be disposed on a substrate 101 and includes a first-type semiconductor layer 112, a light-emitting layer 114, and a second-type semiconductor layer 116, wherein the light-emitting layer 114 is located between the first-type semiconductor layer 112 and the second-type semiconductor layer 116. The first-type semiconductor layer 112, the light-emitting layer 114, and the first portion 117 of the second-type semiconductor layer 116 form a mesa M. The mesa M has a top surface U and a first side surface S1, wherein the top surface U extends perpendicularly to the direction of the first side surface S1. The second portion 119 of the second-type semiconductor layer 116 is recessed relative to the mesa M to form a mesa surface D. The second portion 119 of the second-type semiconductor layer 116 has a second side surface S2, wherein the mesa surface D extends perpendicularly to the direction of the second side surface S2. The terrace surface D is located between the first side surface S1 and the second side surface S2, and the terrace surface D may be parallel to the top surface U. The first insulating layer 120a covers the terrace surface D from the top surface U of the terrace M along the first side surface S1, exposing the second side surface S2. The second insulating layer 130a directly covers the second side surface S2, wherein the thickness ratio of the first insulating layer 120a to the second insulating layer 130a is between 10 and 50. In other words, in this embodiment, the first insulating layer 120a does not cover the second side surface S2, and the second side surface S2 is directly covered only by the second insulating layer 130a.

[0050] Furthermore, in this embodiment, the first-type semiconductor layer 112 is, for example, a P-type semiconductor layer, the light-emitting layer 114 is, for example, a multi-quantum well (MWQ) structure, and the second-type semiconductor layer 116 is, for example, an N-type semiconductor layer, but the present invention is not limited thereto. Furthermore, the micro-LED structure 100a of this embodiment further includes a current distribution layer 160 disposed between the first insulating layer 120a and the first-type semiconductor layer 112, wherein the current distribution layer 160 forms an ohmic contact with the first-type semiconductor layer 112. Here, the current distribution layer 160 directly contacts the top surface U of the platform M, and the orthographic projection of the current distribution layer 160 on the top surface U may be equal to the top surface U, but the present invention is not limited thereto. The material of the current distribution layer 160 may be, for example, indium tin oxide, indium oxide, tin oxide, aluminum zinc oxide, cadmium tin oxide, antimony tin oxide, zinc oxide, or a combination of the foregoing materials. Here, the thickness of the platform M plus the thickness of the current distribution layer 160 is a height H, wherein the height H is smaller than the thickness T of the second portion 119 of the second-type semiconductor layer 116. Here, the height H is, for example, 1 μm to 2 μm, and the thickness T is, for example, 3 μm to 5 μm.

[0051] In particular, Figure 1As shown, the first insulating layer 120a directly covers the terrace surface D, i.e., the terrace surface D only contacts the first insulating layer 120a. The first insulating layer 120a covering the first side surface S1 and the second side surface S2 form a continuous surface CS. In a cross-sectional view, this continuous surface CS is a straight line, for example, extending along the normal direction of the substrate 101, but not limited thereto. The second insulating layer 130a directly covers the first insulating layer 120a on the continuous surface CS and extends along the continuous surface CS to cover the terrace surface D and the first insulating layer 120a on the top surface U. The thickness T2 of the second insulating layer 130a is less than the thickness T1 of the first insulating layer 120a. Here, the thickness T1 of the first insulating layer 120a is, for example, between 0.5 microns and 1 micron, while the thickness T2 of the second insulating layer 130a is, for example, between 20 nanometers and 50 nanometers. On the platform M and the platform surface D, the first insulating layer 120a and the second insulating layer 130a are conformally arranged, that is, the total thickness of the insulating layer is the thickness T1 of the first insulating layer 120a plus the thickness T2 of the second insulating layer 130a, while on the second side surface S2, the total thickness of the insulating layer is only the thickness T2 of the second insulating layer 130a.

[0052] Furthermore, in this embodiment, the material of the first insulating layer 120a is substantially different from the material of the second insulating layer 130a. In one embodiment, the first insulating layer 120a may be, for example, a physically deposited film, while the second insulating layer 130a may be, for example, a chemically deposited film. The aforementioned physical deposition refers to the target material being deposited directly on the target by external forces, without undergoing a chemical reaction. Chemical deposition, on the other hand, refers to the target material reacting in a chemical gas or on the target surface to form different compounds that accumulate into a film. In one embodiment, the first insulating layer 120a and the second insulating layer 130a may each be a single layer or multiple layers. In one embodiment, the first insulating layer 120a may be, for example, a distributed Bragg reflector layer of silicon dioxide (SiO2) / titanium dioxide (TiO2) overlapped by sputtering deposition, and the second insulating layer 130a may be, for example, aluminum oxide (Al2O3) or hafnium dioxide (HfO2) deposited by atomic layer deposition (ALD), or silicon dioxide (SiO2) / silicon nitride (SiN) deposited by chemical vapor deposition (CVD). X N XWhen the second insulating layer 130a is formed using atomic layer deposition or chemical vapor deposition, it can have better step coverage on the second side surface S2, wherein the process temperature of the second insulating layer 130a can be slightly higher than the process temperature of the first insulating layer 120a. In one embodiment, due to different process and material selection, the density of the second insulating layer 130a can be higher than the density of the first insulating layer 120a.

[0053] like Figure 1 As shown, the thicker first insulating layer 120a of this embodiment directly covers the surrounding surfaces (i.e., first side surface S1) of the first-type semiconductor layer 112, the light-emitting layer 114, and the second-type semiconductor layer 116, ensuring electrical passivation. Furthermore, the second portion 119 of the second-type semiconductor layer 116 directly covers only the thinner second insulating layer 130a. Therefore, during the laser lift-off (LLO) process, the second insulating layer (not shown) deposited on the substrate will vaporize or break, and no second insulating layer 130a will remain at the bottom of the second portion 119. In addition to providing electrical isolation, the first insulating layer 120a also reflects light from the light-emitting layer 114 perpendicularly toward the light-emitting surface. Furthermore, the thinner second insulating layer 130a directly covers the second side surface S2, thus passivating the second side surface S2 and reducing non-radiative recombination defects, thereby improving the luminous efficiency of the micro-LED structure 100a. In short, the micro-LED structure 100a of this embodiment has both a thicker first insulating layer 120a and a thinner second insulating layer 130a directly contacting the first insulating layer 120a, thereby achieving both structural reliability and transfer yield.

[0054] In addition, please refer to Figure 1The micro-LED structure 100a of this embodiment further includes a first electrode 140a and a second electrode 150a. The first electrode 140a is electrically connected to the first-type semiconductor layer 112. The second electrode 150a is electrically connected to the second-type semiconductor layer 116, wherein the first electrode 140a and a portion of the second electrode 150a are located on the same plane P. More specifically, the first insulating layer 120a and the second insulating layer 130a expose the first-type semiconductor layer 112 on the top surface U to form a first opening 122, and expose the second portion 119 of the second-type semiconductor layer 116 on the terrace surface D to form a second opening 124. The first electrode 140a is disposed within the first opening 122 and extends onto the second insulating layer 130a. The second electrode 150a is disposed on the second insulating layer 130a and extends into the second opening 124. Since the second insulating layer 130 a is conformally disposed with the first insulating layer 120 a on the mesa M and the mesa surface D, the second insulating layer 130 a also exposes the current distribution layer 160 exposed by the first opening 122 and the second portion 119 of the second-type semiconductor layer 116 exposed by the second opening 124 .

[0055] Because the first insulating layer 120a extends from the top surface U of the mesa M along the first side surface S1 to the mesa surface D, exposing the second side surface S2 of the second portion 119 of the second-type semiconductor layer 116, the first insulating layer 120a does not extend onto the substrate 101. This solves the problem of residual epitaxial insulating layer on the surrounding surfaces of the micro-LEDs after lift-off in the prior art, thereby preventing adverse effects on subsequent transfer processes. Furthermore, the thickness ratio of the first insulating layer 120a to the second insulating layer 130a is between 10 and 50, indicating that the thicker first insulating layer 120a primarily covers the sidewalls of the light-emitting layer 114. The second insulating layer 120a, directly covering the second side surface S2, is significantly thinner, passivating the second side surface S2 to improve luminous efficiency without affecting subsequent transfer steps of the micro-LED structure 100a.

[0056] It should be noted that the following embodiments use the same component numbers and some of the contents of the previous embodiments, wherein the same numbers are used to represent the same or similar components, and the description of the same technical contents is omitted. For the description of the omitted parts, please refer to the previous embodiments, and the following embodiments will not repeat them.

[0057] Figure 2 is a cross-sectional schematic diagram of a micro-LED structure according to another embodiment of the present invention. Figure 1 and Figure 2 The micro-LED structure 100b of this embodiment is Figure 1The difference between the two is that the second insulating layer 130 of this embodiment seals the first insulating layer 120a and a portion of the current distribution layer 160 at the location of the first opening 122 or the second opening 124 to protect the first insulating layer 120a. Figure 2 The figure schematically shows that the second insulating layer 130 seals the first insulating layer 120a at the location of the first opening 122. In other embodiments not shown, the second insulating layer 130 may seal the first insulating layer 120a at the location of the second opening 124. In this case, the first electrode 140a only contacts the current distribution layer 160 and the second insulating layer 140a, but does not contact the first insulating layer 120a.

[0058] Figure 3 is a cross-sectional schematic diagram of a micro-LED structure according to another embodiment of the present invention. Figure 1 and Figure 3 The micro-LED structure 100c of this embodiment is Figure 1 The micro-LED structure 100a is similar to the micro-LED structure 100a of FIG. 1 , but the difference between the two is that the second insulating layer 130c of this embodiment is retracted by a distance G relative to the first insulating layer 120a at the position of the first opening 122 or the second opening 124 to expose a portion of the first insulating layer 120a. In other words, a larger contact area of ​​the current distribution layer 160 is exposed for contact with the first electrode 140a, thereby achieving better ohmic contact. Figure 3 The diagram schematically illustrates that the second insulating layer 130c is retracted relative to the first insulating layer 120a at the location of the first opening 122 by a distance G. In other embodiments not shown, the second insulating layer 130c may also be retracted relative to the first insulating layer 120a at the location of the second opening 124 by a distance G. This allows the second portion 119 of the second-type semiconductor layer 116 (or another current distribution layer not shown) to be fully exposed within the second opening 124, thereby achieving a better ohmic contact with the second electrode 150a. Here, the orthographic projection of the second insulating layer 130c on the epitaxial structure 110 does not overlap with the orthographic projection of the connecting surface between the first electrode 140a and the current distribution layer 160 on the epitaxial structure 110.

[0059] Figure 4 is a cross-sectional schematic diagram of a micro-LED structure according to another embodiment of the present invention. Figure 1 and Figure 4 The micro-LED structure 100d of this embodiment is Figure 1The micro-LED structure 100d is similar to the micro-LED structure 100a of FIG. 1 , but differs in that: in this embodiment, the micro-LED structure 100d further includes a through-hole 170 that penetrates the current distribution layer 160, the first-type semiconductor layer 112, the light-emitting layer 114, and a portion of the second-type semiconductor layer 116. The first insulating layer 120d further extends to cover the inner wall of the through-hole 170, and the second electrode 150d extends into the through-hole 170 to electrically connect with the second-type semiconductor layer 116. In this case, because the second insulating layer 130d is in direct contact with and conformal to the first insulating layer 120d, the second insulating layer 130d also extends into the through-hole 170 at the second opening 124.

[0060] Figure 5 is a cross-sectional schematic diagram of a micro-LED structure according to another embodiment of the present invention. Figure 1 and Figure 5 The micro-LED structure 100e of this embodiment is Figure 1 The micro-LED structure 100a is similar to the micro-LED structure 100a of FIG. The difference between the two is that in this embodiment, on the mesa M and the mesa surface D, portions of the second insulating layer 130e do not directly contact the first insulating layer 120a. Specifically, the first electrode 140e and the second electrode 150e are located between the first insulating layer 120a and the second insulating layer 130e. This means that the first electrode 140e and the second electrode 150e separate the first insulating layer 120a and the second insulating layer 130e, thereby reducing / preventing the possibility of subsequent solder bump overflow and causing a short circuit between the first electrode 140e and the second electrode 150e. The second insulating layer 130e is formed after the first electrode 140e and the second electrode 150e are formed. Therefore, the second insulating layer 130e can be patterned and etched to define a third opening 132e exposing the first electrode 140e and a fourth opening 134e exposing the second electrode 150e. This facilitates subsequent electrical connection of solder bumps to the first electrode 140e and the second electrode 150e through the third opening 132e and the fourth opening 134e, respectively. Here, the micro-LED structure 100e can be, for example, a red micro-LED structure.

[0061] Figure 6 is a cross-sectional schematic diagram of a micro-LED structure according to another embodiment of the present invention. Figure 4 and Figure 6 The micro-LED structure 100f of this embodiment is Figure 4The difference between the two is that in this embodiment, on the platform M and the platform surface D, part of the second insulating layer 130f does not directly contact the first insulating layer 120d. In detail, the first electrode 140f and the second electrode 150f are located between the first insulating layer 120d and the second insulating layer 130f, which means that the first electrode 140f and the second electrode 150f separate the first insulating layer 120d and the second insulating layer 130f, which can reduce / avoid the chance of subsequent solder bump overflow causing a short circuit between the first electrode 140f and the second electrode 150f. Figure 6 In the embodiment, since the second insulating layer 130f is formed after the first electrode 140f and the second electrode 150f are formed, the second insulating layer 130f does not extend into the through-hole 170. Instead, the second insulating layer 130f has a third opening 132f exposing the first electrode 140f and a fourth opening 134f exposing the second electrode 150f. This facilitates subsequent electrical connection of solder bumps to the first electrode 140f and the second electrode 150f through the third opening 132f and the fourth opening 134f, respectively. In other words, the second insulating layer 130f exposes the first electrode 140f and the second electrode 150f at the locations of the first opening 122 and the second opening 124, respectively. Here, the micro-LED structure 100f can be, for example, a red micro-LED structure.

[0062] Figure 7 is a cross-sectional schematic diagram of a micro-LED structure according to another embodiment of the present invention. Figure 1 and Figure 7 The micro-LED structure 100g of this embodiment is similar to Figure 1 The micro-light emitting diode structure 100a is similar to the micro-light emitting diode structure 100a, and the difference between the two is that: in this embodiment, at least one of the first insulating layer 120a and the second insulating layer 130g is a distributed Bragg reflector film layer. Here, the second insulating layer 130g is a distributed Bragg reflector film layer, which includes a plurality of film layers 131, 133, and 135 that are alternately stacked and have different refractive indices, which can amplify the critical angle of internal reflection to increase the light extraction of the light-emitting surface. The film layers 131, 133, and 135 can be oxide layers or nitride layers, respectively, but are not limited to this. The thickness of the film layer is designed according to different needs. In detail, according to the thin film interference formula, the film thickness d meets the following requirements under constructive interference: 2n film dcos(θ)=mλ; When the design requirement of the distributed Bragg reflector film layer is destructive interference, it means that the reflected light in the film layer is designed to have a phase difference (the case of phase reversal is not discussed here), then the film thickness d meets the requirements of Here, θ represents the angle of incidence of light in each of the layers 131, 133, and 135, incident on another layer, n represents the refractive index of the layer, m represents any positive integer, and λ represents the wavelength of the light-emitting layer. Based on the above, the film thickness d depends on the refractive index of the selected material and the control requirements for the light emission angle range of the micro-LED. The thickness of the film layers 131, 133, and 135 can be adjusted experimentally using the thin film interference principle described above. Since thin film interference is an existing optical knowledge, it will not be explained in detail here. Preferably, the thickness of each film layer 131, 133, and 135 can be between 1 / 4 and 1 / 2 times the wavelength of the light-emitting layer 114, which can change the path of internal reflection within the micro-LED structure 100g to reduce internal reflection loss of light. It is worth mentioning that in another embodiment not shown, the first insulating layer may be a distributed Bragg reflector layer, or the first insulating layer and the second insulating layer may be distributed Bragg reflector layers, wherein the film thickness of the first insulating layer may be different from the film thickness of the second insulating layer. The above still falls within the scope of protection of the present invention.

[0063] Figure 8 is a cross-sectional schematic diagram of a micro-LED structure according to another embodiment of the present invention. Figure 4 and Figure 8 The micro-LED structure 100h of this embodiment is Figure 4 The epitaxial structure 110 is similar to the micro-LED structure 100d, with the difference being that in this embodiment, the second insulating layer 130h does not directly contact the first insulating layer 120d. Specifically, the second portion 119 of the second-type semiconductor layer 116 further includes a bottom surface B relative to the terrace surface D, wherein the bottom surface B may be parallel to the terrace surface D, and the second side surface S2 may perpendicularly connect the terrace surface D and the bottom surface B. The second insulating layer 130h extends from the second side surface S2 and directly covers the bottom surface B. The second insulating layer 130h does not overlap with or contact the first insulating layer 120d. In this case, the first insulating layer 120d and the second insulating layer 130h surround the peripheral surface of the epitaxial structure 110, with only the first insulating layer 120d on the terrace M and the terrace surface D, while only the second insulating layer 130h is on the bottom surface B and the second side surface S2 of the second portion 119 of the second-type semiconductor layer 116. The first electrode 140 h directly contacts the first insulating layer 120 d and the current distribution layer 160 , while the second electrode 150 h directly contacts the first insulating layer 120 d and the second-type semiconductor layer 116 exposed by the through hole 170 .

[0064] Figure 9 is a cross-sectional schematic diagram of a micro-LED structure according to another embodiment of the present invention. Figure 8 and Figure 9The micro-LED structure 100i of this embodiment is Figure 8 The micro-LED structure 100h is similar to the micro-LED structure 100h, and the difference between the two is that: in this embodiment, the second insulating layer 130i further extends to cover the first insulating layer 120d located on the first side surface S1, and is flush with the first insulating layer 120d on the top surface U of the platform M. Therefore, on the first side surface S1, the first insulating layer 120d is in direct contact with the second insulating layer 130i.

[0065] Figure 10 is a cross-sectional schematic diagram of a micro-LED structure according to another embodiment of the present invention. Figure 1 and Figure 10 The micro-LED structure 100j of this embodiment is Figure 1 The micro-LED structure 100a is similar to the micro-LED structure 100a, and the difference between the two is that: in this embodiment, the second insulating layer 130j does not directly contact the first insulating layer 120a, and the first insulating layer 120a covering the first side surface S1 and the second side surface S2' are discontinuous surfaces. In detail, the second portion 119 of the second-type semiconductor layer 116 further has a bottom surface B relative to the platform surface D, wherein the bottom surface B can be parallel to the platform surface D, and the second side surface S2' can be tilted to connect the platform surface D and the bottom surface B. In other words, the second side surface S2' is tilted relative to the bottom surface B, which can increase light reflection and thereby improve light output. The second insulating layer 130j directly covers the second side surface S2' and the bottom surface B, and the second insulating layer 130j does not overlap and does not contact the first insulating layer 120a. At this point, the first insulating layer 120a and the second insulating layer 130j surround the peripheral surface of the epitaxial structure 110. Only the first insulating layer 120a is present on the mesa M and the mesa surface D, while only the second insulating layer 130j is present on the bottom surface B and the second side surface S2′ of the second portion 119 of the second-type semiconductor layer 116. The first electrode 140j directly contacts the first insulating layer 120a and the current distribution layer 160, while the second electrode 150j directly contacts the first insulating layer 120a and the second-type semiconductor layer 116 exposed by the second opening 124.

[0066] It is worth mentioning that Figures 8 to 10 The second insulating layers 130h, 130i, and 130j in the micro-LED structure extend from the bottom surface B toward the top surface U. In the actual manufacturing process, the second insulating layers 130h, 130i, and 130j and the first insulating layers 120a and 120d can be formed at different stages. Specifically, the first insulating layers 120a and 120d are first formed at the chip on wafer stage; Figures 8 to 10In the embodiment, the second insulating layers 130h, 130i, and 130j are formed after the micro-LED structures 100h, 100i, and 100j are flipped and transferred to a temporary carrier substrate. Therefore, they are arranged in a covering direction opposite to the first insulating layers 120a and 120d. Alternatively, during the epitaxial wafer fabrication process, only the first insulating layers 120a and 120d may be formed, leaving the second side surfaces S2 and S2' exposed.

[0067] After the micro-LED structures 100h, 100i, and 100j are flipped, the second insulating layers 130h, 130i, and 130j can be implemented in various forms according to the design purpose or the film forming method adopted. Figure 8 In FIG. 1 , the second insulating layer 130h only extends to cover the platform surface D; and Figure 9 As shown, the second insulating layer 130i can continue to cover along the continuous surface CS and finally be flush with the first insulating layer 120d located at the top surface U. Figure 10 In some embodiments, the second insulating layer 130j formed after the transfer process can also better cover the inclined second side surface S2', ensuring that all surrounding surfaces of the micro-LED structure 100j are well insulated and protected.

[0068] As a result, when the micro-LED structures 100h, 100i, 100j are transferred, since the second insulating layers 130h, 130i, 130j have not yet been formed, the residue problem caused by incomplete laser lift-off can be completely avoided.

[0069] In summary, in the design of the micro-LED structure of the present invention, the first insulating layer extends from the top surface of the platform along the first side surface to the platform surface, exposing the second side surface of the second portion of the second-type semiconductor layer. The second insulating layer directly covers this second side surface, with the thickness ratio of the first insulating layer to the second insulating layer ranging from 10 to 50. This means that the thicker first insulating layer does not extend onto the substrate, resolving the problem of residual epitaxial insulating layer on the surrounding surface of the micro-LED after debonding in the prior art. The thinner second insulating layer directly covering the second side surface passivates the second side surface, thereby improving luminous efficiency. Consequently, the micro-LED structure of the present invention exhibits improved structural reliability and luminous efficiency.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A micro light emitting diode structure, characterized in that: include: An epitaxial structure comprising a first-type semiconductor layer, a light-emitting layer, and a second-type semiconductor layer, wherein the light-emitting layer is located between the first-type semiconductor layer and the second-type semiconductor layer, wherein the first-type semiconductor layer, the light-emitting layer, and a first portion of the second-type semiconductor layer form a platform, wherein the platform has a top surface and a first side surface, and wherein a second portion of the second-type semiconductor layer is recessed relative to the platform to form a platform surface, and wherein the second portion has a second side surface, and wherein the platform surface is located between the first side surface and the second side surface; a first insulating layer covering from the top surface of the platform along the first side surface to the platform surface and exposing the second side surface, wherein the first insulating layer directly covers the platform surface, and the first insulating layer covering the first side surface and the second side surface form a continuous surface; as well as The second insulating layer directly covers the second side surface, wherein a thickness ratio of the first insulating layer to the second insulating layer is between 10 and 50.

2. The micro-LED structure according to claim 1, wherein: The second insulating layer directly covers the first insulating layer on the continuous surface and extends along the continuous surface to cover the first insulating layer on the platform surface and the top surface.

3. The micro-LED structure according to claim 1, wherein: The density of the second insulating layer is higher than the density of the first insulating layer.

4. The micro-LED structure according to claim 1, wherein: The first insulating layer is a physically deposited film layer, and the second insulating layer is a chemically deposited film layer.

5. The micro-LED structure according to claim 1, wherein: The material of the first insulating layer is different from the material of the second insulating layer.

6. The micro-LED structure according to claim 1, wherein: The thickness of the second insulating layer is between 20 nanometers and 50 nanometers.

7. The micro-LED structure according to claim 1, wherein: At least one of the first insulating layer and the second insulating layer is a distributed Bragg reflector film layer, which includes a plurality of alternately stacked film layers with different refractive indices, and a thickness of each of the plurality of film layers is between 1 / 4 and 1 / 2 times the emission wavelength of the light-emitting layer.

8. The micro-LED structure according to claim 1, wherein: The first insulating layer and the second insulating layer expose the first-type semiconductor layer on the top surface to form a first opening, and expose the second portion of the second-type semiconductor layer on the terrace surface to form a second opening, and the micro-LED structure further includes: a first electrode disposed in the first opening and electrically connected to the first-type semiconductor layer; and The second electrode is disposed in the second opening and electrically connected to the second-type semiconductor layer, wherein the first electrode and the second electrode both extend onto the second insulating layer, and the first electrode and a portion of the second electrode are located on the same plane.

9. The micro-LED structure according to claim 8, wherein: The second insulating layer seals the first insulating layer at a position of the first opening or the second opening.

10. The micro-LED structure according to claim 8, wherein: The second insulating layer is retracted relative to the first insulating layer at a position of the first opening or the second opening.

11. The micro-LED structure according to claim 8, wherein: The first electrode and the second electrode are located between the first insulating layer and the second insulating layer, and the second insulating layer exposes the first electrode and the second electrode at positions of the first opening and the second opening, respectively.

12. The micro-LED structure according to claim 1, wherein: The second portion of the second-type semiconductor layer further has a bottom surface opposite to the platform surface, the second side surface connects the platform surface and the bottom surface, and the second insulating layer extends from the second side surface and directly covers the bottom surface.

13. The micro-LED structure according to claim 12, wherein: The second insulating layer covers the first insulating layer on the first side surface and is flush with the first insulating layer on the top surface of the platform.

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