MicroLED structure preparation method and MicroLED structure

Abstract

The invention discloses a MicroLED structure preparation method and a MicroLED structure, and belongs to the technical field of semiconductors. The annular conductive layer surrounding the side wall of the light-emitting unit is formed in the light-emitting epitaxial wafer and is electrically connected with the conductive layer in the driving wafer to form the bonding structure, the annular conductive layer is adopted in the bonding structure, the precision requirement of bonding can be reduced, and the bonding efficiency is improved on the premise that electrical connection is met. Theoretically, the bonding deviation value only needs to be smaller than the outer diameter of the annular conducting layer; meanwhile, the annular conducting layer in the bonding structure can serve as an optical isolation structure between the MicroLED light-emitting units, light crosstalk of a device can be prevented, other steps do not need to be additionally added to form the optical isolation structure, and the preparation process of the MicroLED structure is simplified.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for preparing a MicroLED structure and a MicroLED structure. Background Art

[0002] The key technology for MicroLED (micro-light-emitting diode) production is the hybrid integration of fine-pitch light-emitting units on a silicon IC (Integrated Circuit) using standard semiconductor device manufacturing processes. The core of this process is the transfer of the entire compound semiconductor epitaxial layer to the silicon IC wafer through wafer-level bonding. Wafer hybrid bonding is an advanced integrated circuit packaging technology, mainly used to achieve high-density, high-performance interconnection between different chips. In the hybrid bonding process, a thin and uniform layer of dielectric material is deposited on the surface of the wafer, and micron or even nanometer-scale copper pillars are prepared on it. These copper pillars connect the internal circuits of the chip to the outside. The copper layers of two or more chips are precisely aligned and directly pressed together to form a direct electrical contact.

[0003] At present, the wafer hybrid bonding structure used in the MicroLED preparation process is as follows: Figure 1 As shown, the structure is formed by bonding the light-emitting epitaxial wafer 1 and the driver wafer 2, wherein: Figure 2 and Figure 3 As shown, the light-emitting epitaxial wafer 1 is provided with two light-emitting units 3, the surface of the light-emitting unit 3 is provided with a dielectric layer 4, the dielectric layer 4 is provided with a copper column 5, and the copper column 5 is electrically connected to the top of the light-emitting unit 3; Figure 4 As shown, copper pillars 5 are provided in the driver wafer 2. To achieve electrical connection between the light-emitting epitaxial wafer 1 and the driver wafer 2, the copper pillars of the light-emitting epitaxial wafer 1 and the driver wafer 2 must contact each other. Therefore, the deviation during bonding cannot be greater than the diameter of the copper pillars 5, which requires high alignment accuracy. In addition, since the dielectric layer 4 between the light-emitting units 3 cannot achieve optical isolation, optical crosstalk is easily generated. Moreover, if the optical isolation structure is formed through additional photolithography, etching, and metal filling processes, the process will become more complicated. Summary of the Invention

[0004] The purpose of this application is to provide a MicroLED structure preparation method and a MicroLED structure, so as to solve the problems existing in the traditional MicroLED preparation process such as high alignment accuracy requirements, easy generation of light crosstalk and complex process.

[0005] To achieve the above objectives, the present application provides a method for preparing a MicroLED structure, comprising:

[0006] At least two light-emitting units are formed on the surface of the epitaxial substrate, and a passivation layer and a first conductive layer are formed on the surface of the light-emitting units; the first conductive layer is connected to the light-emitting units, and adjacent first conductive layers are not connected; the passivation layer is located between the first conductive layer and the light-emitting units;

[0007] A first dielectric layer is formed on the surface of the epitaxial substrate after the first conductive layer is formed, and a first annular groove is formed in the first dielectric layer; the first annular groove corresponds to the light-emitting unit one by one; the first annular groove surrounds the sidewall of the light-emitting unit and penetrates the first dielectric layer between adjacent light-emitting units in a circumferential direction; adjacent first annular grooves do not intersect;

[0008] forming a second conductive layer inside the first annular groove to obtain a light-emitting epitaxial wafer; the second conductive layer is made of a light-opaque material; and the second conductive layer is connected to the first conductive layer;

[0009] preparing a driver wafer having a third conductive layer, bonding the driver wafer to the light-emitting epitaxial wafer, and performing annealing to ensure one-to-one connection between the third conductive layer and the second conductive layer;

[0010] After bonding, the epitaxial substrate is removed to obtain the MicroLED structure.

[0011] Optionally, the first annular groove has the center of the light-emitting unit as its center; and the inner diameter of the first annular groove is greater than or equal to the diameter of the light-emitting unit after the first conductive layer is formed.

[0012] Optionally, forming at least two light-emitting units on the surface of the epitaxial substrate includes:

[0013] forming a light-emitting material layer on the surface of the epitaxial substrate;

[0014] The light-emitting material layer is etched along the thickness direction by dry etching to form at least two light-emitting units.

[0015] Optionally, forming a passivation layer and a first conductive layer on the surface of the light-emitting unit includes:

[0016] forming the passivation layer on the surface of the epitaxial substrate after forming the light-emitting unit;

[0017] Etching the passivation layer on the top of the light-emitting unit along the thickness direction to form an opening;

[0018] After the opening is formed, the first conductive layer is formed on the surface of the light emitting unit.

[0019] Optionally, forming the first conductive layer on the surface of the light-emitting unit includes:

[0020] forming the first conductive layer on the surface of the epitaxial substrate after forming the passivation layer;

[0021] The first conductive layer between adjacent light emitting units is etched along the thickness direction to form an isolation region.

[0022] Optionally, forming a first dielectric layer on the surface of the epitaxial substrate after forming the first conductive layer, and forming a first annular groove in the first dielectric layer includes:

[0023] forming the first dielectric layer on the surface of the epitaxial substrate after forming the first conductive layer, so that the first dielectric layer covers the area between adjacent light-emitting units and the first conductive layer on top of the light-emitting unit;

[0024] The first annular groove is formed in the first dielectric layer, exposing the first conductive layer at the bottom of the first annular groove.

[0025] Optionally, forming a second conductive layer inside the first annular groove includes:

[0026] forming the second conductive layer on the surface of the epitaxial substrate after the first annular groove is formed;

[0027] The second conductive layer is processed by a chemical mechanical planarization process until the first dielectric layer is exposed.

[0028] Optionally, after the epitaxial substrate is removed after the bonding, the method further includes:

[0029] A fourth conductive layer is formed on a surface of the light emitting unit that is away from the driving wafer; the fourth conductive layer is made of a transparent material.

[0030] Optionally, the step of preparing a driver wafer having a third conductive layer includes:

[0031] forming a second dielectric layer on the surface of the drive substrate, and forming a second annular groove in the second dielectric layer; the second annular groove corresponds to the first annular groove one by one; adjacent second annular grooves do not intersect;

[0032] The third conductive layer is formed inside the second annular groove to obtain the driving wafer.

[0033] To achieve the above-mentioned object, the present application also provides a MicroLED structure, comprising: a bonded light-emitting epitaxial wafer and a driver wafer;

[0034] The light-emitting epitaxial wafer includes: at least two light-emitting units; a passivation layer and a first conductive layer are provided on the surface of the light-emitting unit; the first conductive layer is connected to the light-emitting unit, and adjacent first conductive layers are not connected; the passivation layer is located between the first conductive layer and the light-emitting unit; a first dielectric layer is provided on the surface of the first conductive layer;

[0035] A first annular groove is provided inside the first dielectric layer; the first annular groove corresponds to the light-emitting unit one by one; the first annular groove surrounds the side wall of the light-emitting unit and penetrates the first dielectric layer between adjacent light-emitting units along the circumferential direction; adjacent first annular grooves do not intersect;

[0036] A second conductive layer is provided inside the first annular groove; the second conductive layer is made of opaque material; and the second conductive layer is connected to the first conductive layer;

[0037] The driving wafer includes a third conductive layer; the third conductive layer is connected to the second conductive layer one by one.

[0038] Optionally, the driving wafer includes a driving substrate; a second dielectric layer is provided on the surface of the driving substrate; a second annular groove is provided inside the second dielectric layer; the second annular groove corresponds to the first annular groove one-to-one; adjacent second annular grooves do not intersect; and a third conductive layer is provided inside the second annular groove.

[0039] Obviously, the present application provides a method for preparing a MicroLED structure, in which an annular conductive layer surrounding the sidewalls of the light-emitting unit is formed in the light-emitting epitaxial wafer, so that it is electrically connected to the conductive layer in the driver wafer to form a bonding structure. The use of an annular conductive layer in the bonding structure can reduce the bonding accuracy requirements. Under the premise of meeting the electrical connection, the theoretical bonding deviation value only needs to be less than the outer diameter of the annular conductive layer. At the same time, the annular conductive layer in the bonding structure can serve as an optical isolation structure between MicroLED light-emitting units, which can prevent light crosstalk in the device, and no additional steps are required to form the optical isolation structure, thereby simplifying the preparation process of the MicroLED structure. The present application also provides a MicroLED structure, which is prepared by the MicroLED structure preparation method provided by the present application and also has the above-mentioned beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0041] Figure 1 A schematic diagram of a traditional MicroLED structure;

[0042] Figure 2 This is a schematic diagram of the structure of a traditional light-emitting epitaxial wafer;

[0043] Figure 3 A top view of a conventional light-emitting epitaxial wafer;

[0044] Figure 4 This is a schematic diagram of the structure of a traditional driver wafer;

[0045] Figure 5 A flowchart of a MicroLED manufacturing method provided in an embodiment of the present application;

[0046] Figure 6 A schematic structural diagram of a MicroLED structure provided in an embodiment of the present application;

[0047] Figure 7 A top view of a light-emitting epitaxial wafer provided in an embodiment of the present application;

[0048] Figures 8 to 14 A schematic diagram of a process for preparing a MicroLED provided in an embodiment of the present application.

[0049] The following are the descriptions of the reference numerals:

[0050] 1-light-emitting epitaxial wafer; 2-driver wafer; 3-light-emitting unit; 4-dielectric layer; 5-copper pillar;

[0051] 6-epitaxial substrate; 31-luminescent material layer; 7-passivation layer; 8-first conductive layer; 9-first dielectric layer; 10-second conductive layer;

[0052] 11 - driving substrate; 12 - second dielectric layer; 13 - third conductive layer; 14 - fourth conductive layer. DETAILED DESCRIPTION

[0053] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0054] Please refer to Figure 5 , Figure 5 A flowchart of a method for preparing a MicroLED structure provided in an embodiment of the present application, the method may include:

[0055] S101: forming at least two light-emitting units on the surface of the epitaxial substrate, and forming a passivation layer and a first conductive layer on the surface of the light-emitting units; the first conductive layer is connected to the light-emitting units, and adjacent first conductive layers are not connected; the passivation layer is located between the first conductive layer and the light-emitting units.

[0056] It should be noted that the light emitting units formed in this embodiment are independent of each other and are arranged in a direction parallel to the surface of the epitaxial substrate. This embodiment does not limit the specific number of light emitting units, which can be determined according to actual conditions.

[0057] This embodiment does not limit the specific shape of the light-emitting unit, which can be determined according to actual conditions. For example, the light-emitting unit can be truncated cone-shaped, with the diameter of the light-emitting unit on the side closer to the epitaxial substrate being larger than the diameter on the side away from the epitaxial substrate; the light-emitting unit can also be cylindrical; the light-emitting unit can also be cube-shaped; and the light-emitting unit can also be of any other shape. It should be noted that the use of the above-mentioned truncated cone-shaped light-emitting unit in this embodiment can improve the lighting effect.

[0058] This embodiment does not limit the specific method of forming the light-emitting unit. It only needs to ensure that multiple independent light-emitting units can be formed on the surface of the epitaxial substrate. For example, the following method can be used:

[0059] forming a light-emitting material layer on a surface of an epitaxial substrate;

[0060] The light-emitting material layer is etched along the thickness direction by dry etching to form at least two light-emitting units.

[0061] It should be noted that this embodiment adopts a dry etching method, and the etching process is easy to control, which facilitates the formation of light-emitting units of different shapes.

[0062] This embodiment does not limit the specific type of the light-emitting material layer, and the light-emitting material layer may be any light-emitting material. For example, the light-emitting material layer may be a gallium nitride layer.

[0063] This embodiment does not limit the specific method of forming the passivation layer, as long as it can ensure that the cathode and anode of the light-emitting unit can be isolated. For example, the following method can be used:

[0064] forming a passivation layer on the surface of the epitaxial substrate after the light-emitting unit is formed;

[0065] Etching the passivation layer on the top of the light-emitting unit along the thickness direction to form an opening;

[0066] After the opening is formed, a first conductive layer is formed on the surface of the light emitting unit.

[0067] It should be noted that, in this embodiment, the top of the light-emitting unit refers to the surface of the side of the light-emitting unit away from the epitaxial substrate. The passivation layer formed in this embodiment covers the side walls of the light-emitting unit, but does not cover the top of the light-emitting unit. In this embodiment, the opening formed at the top of the light-emitting unit can facilitate the subsequent electrical connection between the first conductive layer and the light-emitting unit. In this embodiment, only the passivation layer on the side wall of the light-emitting unit is retained, and since the passivation layer is usually an insulating material, a short circuit between the cathode and the anode of the light-emitting unit can be avoided. In addition, when the light-emitting unit is formed by dry etching in this embodiment, defects may be generated on the surface of the light-emitting unit due to the influence of the process. By forming a passivation layer, the defects can also be repaired to improve the light-emitting efficiency.

[0068] This embodiment does not limit the specific type of the passivation layer, and it can be any insulating material. For example, the passivation layer can be a silicon oxide layer, a silicon nitride layer, or an aluminum oxide layer.

[0069] This embodiment does not limit the specific method of forming the first conductive layer. It only needs to ensure that the first conductive layer can be connected to the light-emitting unit. For example, the following methods can be used:

[0070] forming a first conductive layer on the surface of the epitaxial substrate after forming the passivation layer;

[0071] The first conductive layer between adjacent light emitting units is etched along the thickness direction to form an isolation region.

[0072] It should be noted that the first conductive layer formed in this embodiment covers the passivation layer on the top and sidewalls of the light-emitting unit, as well as the portion between adjacent light-emitting units. The first conductive layer is connected to the light-emitting unit at the openings in the passivation layer, achieving electrical connection between the first conductive layer and the light-emitting unit; the isolation region formed ensures that the first conductive layers on the surfaces of adjacent light-emitting units are not connected.

[0073] This embodiment does not limit the specific type of the first conductive layer, and it can be any conductive material. For example, the conductive layer can be an ITO (indium tin oxide) layer.

[0074] S102: forming a first dielectric layer on the surface of the epitaxial substrate after forming the first conductive layer, and forming a first annular groove in the first dielectric layer; the first annular groove corresponds to the light-emitting unit one by one; the first annular groove surrounds the side wall of the light-emitting unit and penetrates the first dielectric layer between adjacent light-emitting units in a circumferential direction; adjacent first annular grooves do not intersect.

[0075] It should be noted that, in this embodiment, the number of the first annular grooves is the same as the number of the light emitting units. Each light emitting unit is provided with a first annular groove on its periphery.

[0076] This embodiment does not limit the specific method of forming the first dielectric layer. It is sufficient as long as the first dielectric layer can fill the area between adjacent light-emitting units to form a first annular groove in the area. For example, the following method can be used:

[0077] A first dielectric layer is formed on the surface of the epitaxial substrate after the first conductive layer is formed, so that the first dielectric layer covers the area between adjacent light-emitting units and the first conductive layer on the top of the light-emitting unit.

[0078] It should be noted that this embodiment employs the above-described method to form the first dielectric layer, ensuring that the first dielectric layer at least covers the light-emitting units. This is even if the thickness of the first dielectric layer covering the area between adjacent light-emitting units is greater than the sum of the thickness of the light-emitting units and the thickness of the first conductive layer on top of the light-emitting units. Accordingly, the opening of the first annular groove is formed at a position higher than the first conductive layer on top of the light-emitting units.

[0079] This embodiment does not limit the specific type of the first dielectric layer, and it can be any insulating material. For example, the first dielectric layer can be a silicon oxide layer, a silicon nitride layer, or a silicon carbonitride layer.

[0080] This embodiment does not limit the specific method of forming the first annular groove. While ensuring that the first annular groove can surround the side wall of the light-emitting unit and penetrate the first dielectric layer between adjacent light-emitting units in the circumferential direction without intersecting, it is also necessary to ensure that the subsequent second conductive layer can be connected to the first conductive layer. For example, the following method can be used:

[0081] A first annular groove is formed in the first dielectric layer, exposing the first conductive layer at the bottom of the first annular groove.

[0082] It should be noted that the sidewall of the first annular groove formed in this embodiment is the first dielectric layer, and the bottom is the second conductive layer. When the second conductive layer is subsequently formed inside the first annular groove, the second conductive layer can be connected to the first conductive layer at the bottom, thereby realizing electrical connection between the second conductive layer and the first conductive layer.

[0083] This embodiment does not limit the specific shape of the first annular groove, which can be determined according to the specific shape of the light-emitting unit. For example, when the light-emitting unit is in the shape of a truncated cone, and the diameter of the light-emitting unit close to the epitaxial substrate is larger than the diameter of the side away from the epitaxial substrate, or the light-emitting unit is in the shape of a cylinder, the first annular groove can be centered on the center of the light-emitting unit; the inner diameter of the first annular groove can be greater than or equal to the diameter of the light-emitting unit after the first conductive layer is formed (when the light-emitting unit is in the shape of a truncated cone, the diameter here refers to the diameter of the light-emitting unit close to the epitaxial substrate); when the light-emitting unit is in the shape of a cube, the first annular groove can be a square annular groove centered on the center of the light-emitting unit; the width of the first annular groove can be greater than or equal to the width of the light-emitting unit after the first conductive layer is formed.

[0084] It should be noted that in this embodiment, the light-emitting unit after the first conductive layer is formed refers to the structure consisting of the first conductive layer, the passivation layer, and the light-emitting unit as a whole. Taking the structure in which the passivation layer covers the sidewalls of the light-emitting unit, and the first conductive layer covers the top of the light-emitting unit, the passivation layer of the sidewalls of the light-emitting unit, and the partial area between adjacent light-emitting units as an example, the diameter of the light-emitting unit after the first conductive layer is formed refers to the sum of the diameter of the light-emitting unit (when the light-emitting unit is truncated cone-shaped, the diameter here refers to the diameter of the light-emitting unit on the side closest to the epitaxial substrate), the thickness of the passivation layer on the sidewalls of the light-emitting unit, and the thickness of the first conductive layer on the sidewalls of the light-emitting unit.

[0085] S103: forming a second conductive layer inside the first annular groove to obtain a light-emitting epitaxial wafer; the second conductive layer is made of a light-opaque material; and the second conductive layer is connected to the first conductive layer.

[0086] It should be noted that in this embodiment, the second conductive layer formed within the first annular groove also has an annular structure and surrounds the sidewalls of the light-emitting unit. The inner diameter of the second conductive layer is the same as the inner diameter of the first annular groove, and the outer diameter of the second conductive layer is the same as the outer diameter of the first annular groove. In this embodiment, the first dielectric layer and the second conductive layer located within the first dielectric layer constitute a bonding layer.

[0087] This embodiment does not limit the specific method of forming the second conductive layer, as long as the second conductive layer can fill the first annular groove, for example, the following method can be used:

[0088] forming a second conductive layer on the surface of the epitaxial substrate after the first annular groove is formed;

[0089] The second conductive layer is processed by a chemical mechanical planarization process until the first dielectric layer is exposed.

[0090] It should be noted that, in this embodiment, the second conductive layer on the surface of the first dielectric layer is removed by using a chemical mechanical planarization process, and the second conductive layer inside the first annular groove is retained.

[0091] This embodiment does not limit the specific type of the second conductive layer, and it can be any conductive and opaque material. For example, the second conductive layer can be a metal conductor layer. Furthermore, the metal conductor layer can be an Al layer, a Cu layer, or a Zn layer.

[0092] It should be noted that when the second conductive layer is a metal conductor layer, during the process of removing the second conductive layer using a chemical mechanical planarization process, part of the second conductive layer at the top of the first annular groove may be removed due to process influences. Therefore, after this step is completed, the second conductive layer inside the first annular groove will be lower than the surface of the first dielectric layer. However, due to the relatively high subsequent annealing temperature, the metal conductor layer will expand, and the expanded metal conductor layer will not be lower than the surface of the first dielectric layer, so it will not affect the connection between the second conductive layer and the third conductive layer.

[0093] S104: preparing a driving wafer having a third conductive layer, bonding the driving wafer to the light-emitting epitaxial wafer and performing annealing to connect the third conductive layer to the second conductive layer one by one.

[0094] This embodiment does not limit the specific method of preparing the driver wafer, as long as it is possible to form the third conductive layer in the driver wafer. For example, the following method can be used:

[0095] forming a second dielectric layer on the surface of the drive substrate, and forming a second annular groove in the second dielectric layer; the second annular groove corresponds to the first annular groove one by one; and adjacent second annular grooves do not intersect;

[0096] A third conductive layer is formed inside the second annular groove to obtain a driving wafer.

[0097] It should be noted that in this embodiment, the number of second annular grooves is the same as the number of first annular grooves, and the positions of the second annular grooves correspond to those of the first annular grooves. In this embodiment, the third conductive layer formed within the second annular groove also has an annular structure. The inner diameter of the third conductive layer is the same as the inner diameter of the second annular groove, and the outer diameter of the third conductive layer is the same as the outer diameter of the second annular groove. In this embodiment, the third conductive layer is connected one-to-one with the second conductive layer, thereby achieving electrical connection between the third conductive layer and the second conductive layer.

[0098] It should be noted that in this embodiment, the same bonding structure as that of the light-emitting epitaxial wafer is formed in the driver wafer. Both the driver wafer and the light-emitting epitaxial wafer use an annular conductive layer, which can reduce the bonding precision requirement.

[0099] This embodiment does not limit the specific method of forming the third conductive layer, as long as the third conductive layer can fill the second annular groove. For example, the following method can be used:

[0100] forming a third conductive layer on the surface of the driving substrate after the second annular groove is formed;

[0101] The third conductive layer is processed by a chemical mechanical planarization process until the second dielectric layer is exposed.

[0102] This embodiment does not limit the specific type of the second dielectric layer. The type of the second dielectric layer may be the same as that of the first dielectric layer, or may be different from that of the first dielectric layer.

[0103] This embodiment does not limit the specific type of the third conductive layer. The type of the third conductive layer can be the same as that of the second conductive layer, or the type of the third conductive layer can be different from that of the second conductive layer.

[0104] It should be noted that when the third conductive layer is a metal conductor layer, during the process of removing the third conductive layer using a chemical mechanical planarization process, part of the third conductive layer at the top of the second annular groove may be removed due to process influences. Therefore, after this step is completed, the third conductive layer inside the second annular groove will be lower than the surface of the second dielectric layer. However, due to the relatively high subsequent annealing temperature, the metal conductor layer will expand, and the expanded metal conductor layer will not be lower than the surface of the second dielectric layer, so it will not affect the connection between the second conductive layer and the third conductive layer.

[0105] S105: After bonding, the epitaxial substrate is removed to obtain a MicroLED structure.

[0106] It should be noted that the epitaxial substrate only serves as a carrier of the light-emitting unit and needs to be removed after the bonding is completed.

[0107] Furthermore, after step S105, this embodiment may further include:

[0108] A fourth conductive layer is formed on a surface of the light emitting unit that is away from the driver wafer; the fourth conductive layer is made of a transparent material.

[0109] It should be noted that the transparent fourth conductive layer formed in this embodiment can improve the ohmic contact between the subsequent metal electrode and the light-emitting material, thereby achieving better electrical connection.

[0110] This embodiment does not limit the specific type of the fourth conductive layer, and it can be any conductive and transparent material. For example, the fourth conductive layer can be an ITO layer.

[0111] Based on the above embodiments, the present application forms an annular conductive layer surrounding the side wall of the light-emitting unit in the light-emitting epitaxial wafer, so that it is electrically connected to the conductive layer in the driver wafer to form a bonding structure. The use of an annular conductive layer in the bonding structure can reduce the bonding accuracy requirements. On the premise of satisfying the electrical connection, the theoretical bonding deviation value only needs to be less than the outer diameter of the annular conductive layer; at the same time, the annular conductive layer in the bonding structure can serve as an optical isolation structure between MicroLED light-emitting units, which can prevent light interference from occurring in the device, and there is no need to add additional steps to form an optical isolation structure, which simplifies the preparation process of the MicroLED structure.

[0112] Please refer to Figure 6 and Figure 7 , Figure 6 A schematic structural diagram of a MicroLED structure provided in an embodiment of the present application; Figure 7 A top view of a light-emitting epitaxial wafer provided in an embodiment of the present application, the structure may include: a bonded light-emitting epitaxial wafer 1 and a driver wafer 2;

[0113] The light-emitting epitaxial wafer 1 includes: at least two light-emitting units 3; a passivation layer 7 and a first conductive layer 8 are provided on the surface of the light-emitting unit 3; the first conductive layer 8 is connected to the light-emitting unit 3, and adjacent first conductive layers 8 are not connected; the passivation layer 7 is located between the first conductive layer 8 and the light-emitting unit 3; a first dielectric layer 9 is provided on the surface of the first conductive layer 8;

[0114] A first annular groove is provided inside the first dielectric layer 9; the first annular groove corresponds to each light emitting unit 3 one by one; the first annular groove surrounds the side wall of the light emitting unit 3 and penetrates the first dielectric layer 9 between adjacent light emitting units 3 along the circumferential direction; adjacent first annular grooves do not intersect;

[0115] A second conductive layer 10 is provided inside the first annular groove; the second conductive layer 10 is made of opaque material; and the second conductive layer 10 is connected to the first conductive layer 8;

[0116] The driving wafer 2 includes a third conductive layer 13 ; the third conductive layer 13 is connected to the second conductive layer 10 in a one-to-one manner.

[0117] This embodiment does not limit the specific number, shape, type and other parameters of the light-emitting unit 3, the passivation layer 7, the first conductive layer 8, the first dielectric layer 9, the first annular groove, the second conductive layer 10 and the third conductive layer 13. For details, please refer to the embodiment of the above-mentioned MicroLED structure preparation method, which will not be repeated here.

[0118] This embodiment does not limit the specific structure of the driver wafer 2, as long as the driver wafer 2 includes at least the third conductive layer 13. For example, the driver wafer 2 may include a driver substrate 11; a second dielectric layer 12 is provided on the surface of the driver substrate 11; a second annular groove is provided inside the second dielectric layer 12; the second annular groove corresponds to the first annular groove one-to-one; adjacent second annular grooves do not intersect; and the third conductive layer 13 is provided inside the second annular groove.

[0119] It should be noted that in this embodiment, the driver wafer 2 and the light-emitting epitaxial wafer 1 have the same bonding structure. Both the driver wafer 2 and the light-emitting epitaxial wafer 1 use an annular conductive layer, which can reduce the bonding precision requirement.

[0120] This embodiment does not limit the specific number, shape, type and other parameters of the second dielectric layer 12 and the third annular groove. For details, please refer to the embodiment of the above-mentioned MicroLED structure preparation method, which will not be repeated here.

[0121] Furthermore, in this embodiment, a fourth conductive layer 14 may be provided on a surface of the light emitting unit 3 facing away from the driver wafer 2 ; the fourth conductive layer 14 is made of a transparent material.

[0122] It should be noted that the transparent fourth conductive layer 14 in this embodiment can improve the ohmic contact between the subsequent metal electrode and the light-emitting material, thereby achieving better electrical connection.

[0123] This embodiment does not limit the specific type of the fourth conductive layer 14 . For details, please refer to the embodiment of the above-mentioned MicroLED structure preparation method, which will not be repeated here.

[0124] Based on the above embodiments, the present application is prepared by the above MicroLED structure preparation method and also has the above beneficial effects.

[0125] The following is a specific example to illustrate the above MicroLED structure preparation process. Please refer to Figure 6 、 Figures 8 to 14 , the process is as follows:

[0126] 1. If Figure 8 As shown, a light emitting material layer 31 is formed on the surface of the epitaxial substrate 6;

[0127] 2. If Figure 9 As shown, two independent light-emitting units 3 are formed on the surface of the epitaxial substrate 6 by dry etching;

[0128] 3. If Figure 10 As shown, a passivation layer 7 (specifically, a silicon oxide layer, a silicon nitride layer, or an aluminum oxide layer) is formed on the surface of the light emitting unit 3, and the passivation layer 7 on the top of the light emitting unit 3 is etched to form an opening;

[0129] 4. If Figure 11 As shown, a first conductive layer 8 (specifically, an ITO layer) is formed on the surface of the light-emitting unit 3, and isolation regions are etched between the light-emitting units 3;

[0130] 5. If Figure 12 As shown, a first dielectric layer 9 (specifically, a silicon oxide layer, a silicon nitride layer, or a silicon carbonitride layer, and the thickness of the first dielectric layer 9 at least covers the light-emitting unit 3) is formed on the first conductive layer 8, and a first annular groove is formed in the first dielectric layer 9;

[0131] 6. If Figure 13As shown, a second conductive layer 10 (specifically, a metal conductor layer such as an Al layer, a Cu layer, or a Zn layer) is formed above the first dielectric layer 9 and the first annular groove, and the second conductive layer 10 is processed by a chemical mechanical planarization process until the first dielectric layer 9 is exposed. After this step is completed, the remaining first dielectric layer 9 and the second conductive layer 10 located inside the first dielectric layer 9 constitute a bonding layer;

[0132] 7. If Figure 14 As shown, a bonding structure identical to that of the light-emitting epitaxial wafer 1 is formed in the driver wafer 2 , the driver wafer 2 is bonded to the light-emitting epitaxial wafer 1 , and annealing is performed.

[0133] 8. If Figure 6 As shown, the epitaxial substrate 6 of the light-emitting epitaxial wafer 1 is removed, and a transparent fourth conductive layer 14 (specifically, an ITO layer) is formed above the light-emitting unit 3 .

[0134] The principles and implementation methods of the present application are described herein using specific examples, and the various embodiments are in a progressive relationship. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. The description of the above embodiments is only used to help understand the method and core ideas of the present application. For those of ordinary skill in the art, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

[0135] It should also be noted that, in this specification, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

Claims

1. A method for preparing a MicroLED structure, characterized in that: include: Forming at least two light-emitting units on the surface of the epitaxial substrate, and forming a passivation layer and a first conductive layer on the surface of the light-emitting units; The first conductive layer is connected to the light emitting unit, and adjacent first conductive layers are not connected; the passivation layer is located between the first conductive layer and the light emitting unit; A first dielectric layer is formed on the surface of the epitaxial substrate after the first conductive layer is formed, and a first annular groove is formed in the first dielectric layer; the first annular groove corresponds to the light-emitting unit one by one; the first annular groove surrounds the sidewall of the light-emitting unit and penetrates the first dielectric layer between adjacent light-emitting units in a circumferential direction; adjacent first annular grooves do not intersect; forming a second conductive layer inside the first annular groove to obtain a light-emitting epitaxial wafer; the second conductive layer is made of a light-opaque material; and the second conductive layer is connected to the first conductive layer; preparing a driver wafer having a third conductive layer, bonding the driver wafer to the light-emitting epitaxial wafer, and performing annealing to ensure one-to-one connection between the third conductive layer and the second conductive layer; After bonding, the epitaxial substrate is removed to obtain the MicroLED structure.

2. The method for preparing a MicroLED structure according to claim 1, wherein: The first annular groove takes the center of the light-emitting unit as its center; the inner diameter of the first annular groove is greater than or equal to the diameter of the light-emitting unit after the first conductive layer is formed.

3. The method for preparing a MicroLED structure according to claim 1, wherein: The step of forming at least two light-emitting units on the surface of the epitaxial substrate comprises: forming a light-emitting material layer on the surface of the epitaxial substrate; The light-emitting material layer is etched along the thickness direction by dry etching to form at least two light-emitting units.

4. The method for preparing a MicroLED structure according to claim 1, wherein: The forming of a passivation layer and a first conductive layer on the surface of the light-emitting unit includes: forming the passivation layer on the surface of the epitaxial substrate after forming the light-emitting unit; Etching the passivation layer on the top of the light-emitting unit along the thickness direction to form an opening; After the opening is formed, the first conductive layer is formed on the surface of the light emitting unit.

5. The method for preparing a MicroLED structure according to claim 4, wherein: The forming of the first conductive layer on the surface of the light emitting unit includes: forming the first conductive layer on the surface of the epitaxial substrate after forming the passivation layer; The first conductive layer between adjacent light emitting units is etched along the thickness direction to form an isolation region.

6. The method for preparing a MicroLED structure according to claim 5, wherein: The step of forming a first dielectric layer on the surface of the epitaxial substrate after forming the first conductive layer, and forming a first annular groove in the first dielectric layer, comprises: forming the first dielectric layer on the surface of the epitaxial substrate after forming the first conductive layer, so that the first dielectric layer covers the area between adjacent light-emitting units and the first conductive layer on top of the light-emitting unit; The first annular groove is formed in the first dielectric layer, exposing the first conductive layer at the bottom of the first annular groove.

7. The method for preparing a MicroLED structure according to claim 1, wherein: The forming of the second conductive layer inside the first annular groove includes: forming the second conductive layer on the surface of the epitaxial substrate after the first annular groove is formed; The second conductive layer is processed by a chemical mechanical planarization process until the first dielectric layer is exposed.

8. The method for preparing a MicroLED structure according to claim 1, wherein: After the epitaxial substrate is removed after the bonding, the method further comprises: A fourth conductive layer is formed on a surface of the light emitting unit that is away from the driving wafer; the fourth conductive layer is made of a transparent material.

9. The method for preparing a MicroLED structure according to any one of claims 1 to 8, wherein: The method of preparing a driver wafer having a third conductive layer includes: forming a second dielectric layer on the surface of the drive substrate, and forming a second annular groove in the second dielectric layer; the second annular groove corresponds to the first annular groove one by one; adjacent second annular grooves do not intersect; The third conductive layer is formed inside the second annular groove to obtain the driving wafer.

10. A MicroLED structure, characterized in that: include: Bonded light-emitting epitaxial wafer and driver wafer; The light-emitting epitaxial wafer includes: at least two light-emitting units; a passivation layer and a first conductive layer are provided on the surface of the light-emitting unit; the first conductive layer is connected to the light-emitting unit, and adjacent first conductive layers are not connected; the passivation layer is located between the first conductive layer and the light-emitting unit; a first dielectric layer is provided on the surface of the first conductive layer; A first annular groove is provided inside the first dielectric layer; the first annular groove corresponds to the light-emitting unit one by one; the first annular groove surrounds the side wall of the light-emitting unit and penetrates the first dielectric layer between adjacent light-emitting units along the circumferential direction; adjacent first annular grooves do not intersect; A second conductive layer is provided inside the first annular groove; the second conductive layer is made of opaque material; and the second conductive layer is connected to the first conductive layer; The driving wafer includes a third conductive layer; the third conductive layer is connected to the second conductive layer one by one.

11. The MicroLED structure according to claim 10, wherein: The driving wafer includes a driving substrate; a second dielectric layer is provided on the surface of the driving substrate; a second annular groove is provided inside the second dielectric layer; the second annular groove corresponds to the first annular groove one-to-one; adjacent second annular grooves do not intersect; and a third conductive layer is provided inside the second annular groove.

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