CN115966583A

CN115966583A - LED chip assembly, preparation method thereof, transfer method and display panel

Info

Publication number: CN115966583A
Application number: CN202111175681.1A
Authority: CN
Inventors: 马非凡; 曹进; 戴广超; 张雪梅
Original assignee: Chongqing Kangjia Photoelectric Technology Research Institute Co Ltd
Current assignee: Chongqing Kangjia Photoelectric Technology Research Institute Co Ltd
Priority date: 2021-10-09
Filing date: 2021-10-09
Publication date: 2023-04-14

Abstract

The invention relates to an LED chip assembly, a preparation method, a transfer method and a display panel thereof. In the process of transferring the LED chip from the bearing substrate to the transfer substrate, a plurality of columnar grooves are formed by arranging and etching the sacrificial layer, then the bonding piece comprising the bonding column is formed by arranging the bonding material in the grooves, the bonding column is connected with the epitaxial layer of the LED chip, and the bonding piece is combined with the transfer substrate, so that the LED chip is reliably connected with the transfer substrate. And after the bearing substrate is peeled off and the LED chip is transferred to the transfer substrate, the sacrificial layer is removed, so that the LED chip is connected to the transfer substrate only through the bonding column, and under the condition, if the LED chip is picked up from the transfer substrate, the LED chip can be easily and rapidly separated from the transfer substrate only by damaging the connection between the LED chip and the transfer substrate realized based on the bonding column, and the transfer efficiency and the transfer yield of the LED chip between the transfer substrate and the transfer head are improved.

Description

LED chip assembly, preparation method thereof, transfer method and display panel

Technical Field

The invention relates to the technical field of display, in particular to an LED chip assembly, a preparation method, a transfer method and a display panel thereof.

Background

After the LED chips are fabricated on the wafer, the LED chips generally need to be bonded to the driving backplane through two or more transfers to implement the fabrication of the display panel, and in the process of transferring the LED chips, the LED chips need to be combined with the receiving carrier of the LED chips, and meanwhile, the LED chips need to be separated from the supplying carrier thereof.

Therefore, how to improve the transfer efficiency and transfer yield of the LED chip is an urgent problem to be solved at present.

Disclosure of Invention

In view of the above-mentioned deficiencies of the related art, the present application aims to provide an LED chip assembly, a manufacturing method thereof, a transferring method thereof and a display panel, and aims to solve the problem that the transferring scheme of the LED chip in the related art is unreliable in bonding the LED chip with the receiving carrier or difficult to separate the LED chip from the supplying carrier.

The invention provides a preparation method of an LED chip assembly, which comprises the following steps:

providing a bearing substrate with a plurality of LED chips;

forming a sacrificial layer on one surface of the bearing substrate, which is provided with the LED chip, wherein the LED chip is not arranged in the sacrificial layer;

etching the sacrificial layer from one surface of the sacrificial layer, which is far away from the bearing substrate, so as to form a plurality of columnar grooves, wherein the grooves take the surface of the epitaxial layer of the LED chip as the bottom surfaces of the grooves;

arranging bonding materials in the groove to form a bonding piece comprising a bonding column, wherein one end of the bonding column is combined with the surface of the epitaxial layer, and the distance between the other end of the bonding column and the bearing substrate is larger than the distance between the free end of the chip electrode in the LED chip and the bearing substrate;

bonding one side of the bonding piece, which is far away from the bearing substrate, with the transfer substrate, and stripping the bearing substrate;

and removing the sacrificial layer.

In the preparation method of the LED chip assembly, in the process of transferring the LED chip from the bearing substrate to the transfer substrate, the plurality of columnar grooves are formed by arranging and etching the sacrificial layer, then the bonding piece comprising the bonding column is formed by arranging the bonding material in the grooves, the bonding column is connected with the epitaxial layer of the LED chip, and the bonding piece is combined with the transfer substrate, so that the LED chip is reliably connected with the transfer substrate. And after the bearing substrate is peeled off and the LED chip is transferred to the transfer substrate, the sacrificial layer is removed, so that the LED chip is connected to the transfer substrate only through the bonding column, and under the condition, if the LED chip is picked up from the transfer substrate, the LED chip can be easily and rapidly separated from the transfer substrate only by damaging the connection between the LED chip and the transfer substrate realized based on the bonding column, and the transfer efficiency and the transfer yield of the LED chip between the transfer substrate and the transfer head are improved.

Optionally, after removing the sacrificial layer, the method further includes:

and arranging a passivation layer coating the epitaxial layer.

According to the LED chip assembly manufacturing method, the passivation layer for coating the LED chip epitaxial layer is arranged after the sacrificial layer is removed, the passivation layer is used for electrically isolating the epitaxial layer of the LED chip from water and oxygen, the reliability of the LED chip is improved, and meanwhile, the LED chip assembly manufacturing method is high in quality.

Optionally, the sacrificial layer comprises at least one of silicon oxide and aluminum oxide, and removing the sacrificial layer comprises:

and etching the sacrificial layer covering one surface of the epitaxial layer facing the transfer substrate, and etching the groove of the region of the sacrificial layer between the adjacent LED chips, wherein the etching depth of the groove etching is equal to the thickness of the sacrificial layer in the region, and the etching width is smaller than the width of the gap between the adjacent LED chips.

In the preparation method of the LED chip assembly, when the sacrificial layer is removed, the sacrificial layer is not completely removed, but a part of the sacrificial layer can still be attached to the surface of the epitaxial layer through etching limitation, so that the epitaxial layer of the LED chip can be passivated by directly utilizing the sacrificial layer, the epitaxial layer can be isolated from external electric isolation and water oxygen to a certain extent, and the cost can be reduced.

Based on the same inventive concept, the application also provides an LED chip transfer method, which comprises:

providing an LED chip assembly, wherein the LED chip assembly is prepared according to any one of the LED chip assembly preparation methods;

anchoring the LED chip on the transfer substrate through the transfer head, and applying force to destroy the connection formed by the bonding columns so as to realize the pickup of the LED chip;

and bonding the chip electrodes of the picked LED chips to the backboard electrodes of the driving backboard.

In the LED chip transfer method, in the process of transferring the LED chip from the bearing substrate to the transfer substrate, a plurality of columnar grooves are formed by arranging and etching the sacrificial layer, then the bonding material is arranged in the grooves to form a bonding piece comprising bonding columns, the bonding columns are connected with the epitaxial layer of the LED chip, and the bonding piece is combined with the transfer substrate, so that the LED chip is reliably connected with the transfer substrate. And after the bearing substrate is stripped to transfer the LED chip to the transfer substrate, the sacrificial layer is removed, so that the LED chip is connected to the transfer substrate only through the bonding column, and under the condition, if the LED chip is picked up from the transfer substrate, the LED chip can be easily and rapidly separated from the transfer substrate only by damaging the connection between the LED chip and the transfer substrate based on the bonding column, and the transfer efficiency and the transfer yield of the LED chip between the transfer substrate and the transfer head are improved.

Based on the same inventive concept, the application also provides an LED chip assembly, and the LED chip assembly is manufactured by adopting the LED chip assembly manufacturing method.

In the LED chip component, the plurality of columnar grooves are formed by arranging and etching the sacrificial layer in the process of preparing the LED chip component, then the bonding piece comprising the bonding column is formed by arranging the bonding material in the grooves, the bonding column is connected with the epitaxial layer of the LED chip, and the bonding piece is combined with the transfer substrate, so that the LED chip is reliably connected with the transfer substrate. Therefore, after the bearing substrate is peeled off to transfer the LED chip to the transfer substrate, the sacrificial layer is removed, so that the LED chip is connected to the transfer substrate only through the bonding column, under the condition, if the LED chip is picked up from the LED chip assembly, the LED chip can be easily and rapidly separated from the transfer substrate only by damaging the connection between the LED chip and the transfer substrate realized based on the bonding column, and the transfer efficiency and the transfer yield of the LED chip between the transfer substrate and the transfer head are improved.

Based on the same inventive concept, the application also provides a display panel, the display panel comprises a driving backboard and a plurality of LED chips, chip electrodes of the LED chips are electrically connected with backboard electrodes of the driving backboard, and the LED chips are transferred onto the driving backboard by adopting any one of the LED chip transfer methods.

In the display panel, in the process of transferring the LED chip from the bearing substrate to the transfer substrate, the plurality of columnar grooves are formed by arranging and etching the sacrificial layer, then the bonding material is arranged in the grooves to form the bonding piece comprising the bonding columns, the bonding columns are connected with the epitaxial layer of the LED chip, and the bonding piece is combined with the transfer substrate, so that the LED chip is reliably connected with the transfer substrate. Therefore, after the bearing substrate is peeled off to transfer the LED chip to the transfer substrate, the sacrificial layer is removed, so that the LED chip is connected to the transfer substrate only through the bonding column, under the condition, if the LED chip is picked up from the LED chip assembly, the LED chip can be easily and rapidly separated from the transfer substrate only by damaging the connection between the LED chip and the transfer substrate realized based on the bonding column, the transfer efficiency and the transfer yield of the LED chip between the transfer substrate and the transfer head are improved, and the production cost of the display panel is reduced.

Drawings

Fig. 1 is a schematic flow chart of a method for manufacturing an LED chip assembly according to an alternative embodiment of the present invention;

FIG. 2 is a schematic view illustrating a process state variation of an LED chip assembly according to an alternative embodiment of the present invention;

FIG. 3 is a schematic view of a bonding element disposed on a sacrificial layer provided in an alternative embodiment of the invention;

FIG. 4 is a schematic flow chart of the process of disposing bonding elements on a sacrificial layer according to an alternative embodiment of the present invention;

fig. 5 is a schematic view of bonding of the bonding member provided in an alternative embodiment of the present invention to the transfer substrate 25;

FIG. 6a is a schematic view of a bond post forming a broken connection in accordance with an alternative embodiment of the invention;

FIG. 6b is another schematic view of the bond post forming a broken connection in an alternative embodiment of the invention;

FIG. 6c is a further schematic view of the bond post formed connection being broken in an alternative embodiment of the invention;

FIG. 7 is a schematic diagram of an LED chip assembly with a passivation layer according to an alternative embodiment of the present invention;

FIG. 8 is a schematic diagram of an etching region for removing a sacrificial layer according to an alternative embodiment of the present invention;

FIG. 9 is a schematic view of a state change of an LED chip transfer in an LED chip assembly according to another alternative embodiment of the present invention;

FIG. 10 is a schematic flow chart illustrating a method for transferring LED chips according to another alternative embodiment of the present invention;

FIG. 11 is a schematic illustration of the removal of the passivation layer on the free ends of the electrodes of the chip in an alternative embodiment of the invention;

fig. 12 is a schematic structural diagram of a display panel according to another alternative embodiment of the present invention;

FIG. 13 is a schematic view of a process for manufacturing a display panel according to yet another alternative embodiment of the present invention;

fig. 14 is a schematic view illustrating a process state change of a display panel according to still another alternative embodiment of the present invention.

Description of the reference numerals:

20-an LED chip assembly; 21-a carrier substrate; 22-LED chips; 23-a sacrificial layer; 230-a groove; 231-a first part; 232-a second portion; 24-bondAssembling the components; 240-bond post; 241-a bonding layer; 25-a transfer substrate; 26-a passivation layer; 90-an LED chip assembly; 91-a transfer head; 92-a drive back plate; 93-hydrofluoric acid solution; 94-a substrate; 12-a display panel; 1401-a growth substrate; 1402-epitaxial layer; 1403-LED chip; 1404-SiO ₂ A layer; 1405-grooves; 1406-a bonding layer; 1407-a binding post; 1408-a transfer substrate; 1409-Al ₂ O ₃ A layer; 1410-PDMS transfer head; 1411-HF solution; 1412 — drive back plate.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present application are given in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

Micro-LED (Micro LED) is a new display technology, and compared with the conventional display technology, the Micro-LED has the characteristics of high response speed, self-luminescence, high contrast, long service life, high photoelectric efficiency and the like. The Micro-LED display technology relates to millions or even tens of millions of LED chips, for example, a 4K display panel needs 2500 tens of millions of LED chips, and faces the transfer problem of a huge number of LED chips, "mass transfer arises, for example, electrostatic adsorption technology, fluid assembly technology, roller imprinting technology, vandertile force transfer technology, laser transfer technology, etc.

The LED dies are generally required to undergo two or more transfers from the completion of the preparation to the placement on the driving substrate, and it can be understood that in the process of transferring the LED dies from one carrier a to another carrier B, the carrier a is the donor carrier of the LED dies with respect to the carrier B, and the carrier B is the acceptor carrier of the LED dies with respect to the carrier a. Of course, during other transfer processes of the LED dies, the roles assumed by the carrier a and the carrier B are also changed, for example, during the process of transferring the LED dies from the carrier B to the carrier C, the role of the carrier B is changed into the donor carrier of the LED dies, and the recipient carrier of the LED dies is the carrier C. It should be understood that the donor carrier may be a substrate, or a transfer device such as a transfer head, and the same recipient carrier may be a substrate or a transfer device including a transfer head.

In an ideal transfer process, when the LED die is transferred from the donor carrier to the recipient carrier, the LED die should be reliably combined with the recipient carrier and simultaneously separated from the donor carrier easily and completely. However, in general, the LED dies are either not securely bonded to the receiving carrier, which results in the LED dies not being transferred to the receiving carrier or being easily detached from the receiving carrier; or too tightly coupled to the donor carrier to be easily separated. Because the transfer efficiency and yield of the LED chips are always low due to the existence of these problems.

Based on this, the present application intends to provide a solution to the above technical problem, the details of which will be explained in the following embodiments.

An alternative embodiment of the present application:

the present embodiment provides an LED chip assembly and a method for manufacturing the LED chip assembly, where the LED chip assembly is an intermediate product after growing LED chips and before transferring the LED chips to a driving back plate, and the LED chip assembly includes a substrate and a plurality of LED chips disposed on the substrate. The following describes the preparation process of the LED chip assembly with reference to fig. 1 and fig. 2:

s102: a bearing substrate with a plurality of LED chips is provided.

In the present embodiment, the "carrier substrate" and the "transfer substrate" in the following are merely used for the purpose of distinguishing the substrates used in different stages from each other in terms of names, and there is no limitation, and it is also possible to exchange the names of the "carrier substrate" and the "transfer substrate".

Referring to fig. 2 (a), the carrier substrate 21 has two opposite surfaces, one of which faces upward to carry a plurality of LED chips 22, and the plurality of LED chips 22 may be any one of Micro-LED (Micro LED) chips, mini-LED (Mini LED) chips, OLED (Organic Light-Emitting Diode) chips, and general LED chips. The LED chips 22 on the carrier substrate 21 may include at least one of a red chip, a green chip and a blue chip, and in some examples, the LED chips 22 may also include at least one of a white chip, a yellow chip and the like.

In the present embodiment, the LED chip 22 on the carrier substrate 21 is transferred to the transfer substrate to form an LED chip assembly, and the LED chip 22 on the LED chip assembly can be transferred to the driving backplane by a transfer device such as a transfer head, so it should be understood by those skilled in the art that the LED chip 22 should be oriented on the transfer substrate in the same direction as the LED chip 22 is oriented on the driving backplane, the LED chip 22 should be oriented on the carrier substrate 21 in the opposite direction to the driving backplane, and in the case that the LED chip 22 is a flip chip, the chip electrode is oriented on the driving backplane, and then the chip electrode should be opposite to the carrier substrate 21 when the LED chip is on the carrier substrate 21, as shown in (a) in fig. 2. Of course, if the LED chips in the LED chip assembly can be bonded to the driving backplane without the aid of a transfer device such as a transfer head, the orientation of the LED chips 22 on the carrier substrate 21 should be changed. In addition, if the LED chip 22 has a different structure, the orientation relationship between the chip electrode and the carrier substrate 21, the transfer substrate, and the driving backplane may be different.

In some examples of the present embodiment, the carrier substrate 21 may be a growth substrate of the LED chip 22, and the epitaxial layer of the LED chip 22 is directly grown on the carrier substrate 21, in some examples of the present embodiment, the LED chip 22 is a GaN (gallium nitride) -based LED chip, and the carrier substrate 21 may be any one of a sapphire substrate, a silicon substrate, and a gallium nitride substrate. In some examples, the carrier substrate 21 may not be a growth substrate for the LED chip 22, for example, when the LED chip 22 is a red chip, the growth substrate for the epitaxial layer of the LED chip 22 may be a GaAs (gallium arsenide) substrate, but the red chip is not suitable for directly manufacturing a chip electrode on the GaAs substrate.

S104: and forming a sacrificial layer on one surface of the bearing substrate, which is provided with the LED chip, wherein the LED chip is not arranged in the sacrificial layer.

Referring to fig. 2 (b), a sacrificial layer 23 may be disposed on a side of the carrier substrate 21 where the LED chip 22 is disposed, and the LED chip 22 is not in the sacrificial layer 23, it is understood that "the LED chip 22 is not in the sacrificial layer 23" means that a minimum distance between a side of the LED chip 22 away from the carrier substrate 21 and the carrier substrate 21 is smaller than a minimum distance between a side of the sacrificial layer 23 away from the carrier substrate 21 and the carrier substrate 21. In the embodiment, the sacrificial layer 23 mainly provides a "molding mold" for disposing the bonding member, so that the sacrificial layer 23 is patterned after being disposed, and the sacrificial layer 23 is removed after the bonding member is disposed, so that the sacrificial layer 23 is usually easy to be patterned and removed, and the quality of the LED chip 22 is not affected by the removal means during removal, which can be considered with reference to the requirements when selecting the material for forming the sacrificial layer 23; the sacrifice layer 23 is generally made of an insulating material. In some examples of the present embodiment, the sacrificial layer 23 includes, but is not limited to, siO ₂ (silicon oxide), al ₂ O ₃ At least one of (alumina), for example, in some examples, the sacrificial layer 23 may be a photoresist material.

S106: and etching the sacrificial layer from one surface of the sacrificial layer far away from the bearing substrate to form a plurality of columnar grooves, wherein the grooves take the surface of the epitaxial layer of the LED chip as the bottom surfaces of the grooves.

After the sacrificial layer 23 is disposed, the sacrificial layer 23 may be subjected to a patterning process, and in this embodiment, a side of the sacrificial layer 23 away from the carrier substrate 21 may be etched to form a plurality of pillar-shaped grooves 230, as shown in (c) of fig. 2. In the present embodiment, the grooves 230 are cylindrical, which means that the grooves 230 are elongated, i.e., the dimension of the grooves 230 in the direction parallel to the carrier substrate 21 is smaller than the dimension of the grooves 230 in the direction perpendicular to the carrier substrate 21. The term "cylindrical" is not limited to the cross-sectional shape of the groove 230, and in some examples of the embodiment, the cross-section of the groove 230 may be circular, oval, triangular, rectangular, other polygonal shapes, or even irregular shapes. In this embodiment, the position of the groove 230 is opposite to the position of the LED chip 22, and the groove 230 takes the epitaxial layer of the LED chip 22 as the groove bottom, in other words, the surface of the epitaxial layer of the LED chip 22, which faces away from the carrier substrate 21, is exposed from the groove bottom of the groove 230, so as to avoid damaging the LED chip 22 in the process of forming the groove 230, in this embodiment, the etching depth of the sacrificial layer 23 is not greater than the thickness of the sacrificial layer 23 at the etching position. In the present embodiment, each LED chip 22 has a corresponding groove 230, and in some examples, the number of the grooves 230 may correspond to the number of the LED chips 22 one by one; in still other examples, one LED chip 22 may correspond to two or even more than two grooves 230. In fig. 2 (c), only one groove 230 is disposed on each LED chip 22, and the groove 230 is located above the P-type semiconductor layer of the LED chip 22 in the flip-chip structure, that is, an orthographic projection area of the groove 230 on the epitaxial layer coincides with the P-type semiconductor layer, or an orthographic projection of the groove 230 on the epitaxial layer is located in a P-electrode disposition area of the LED chip 22. However, in other examples of the present embodiment, the groove 230 may be located in a region other than the P-type semiconductor layer. In the present embodiment, the reason why the groove 230 is selectively provided on the P-type semiconductor layer of the LED chip 22 is that the electrode providing region of the P electrode is generally larger than that of the N electrode in the LED chip 22 of the flip-chip structure.

S108: a bonding material is disposed in the groove to form a bond including a bonding post.

After patterning the sacrificial layer 23 to form the desired recesses 230, a bonding material can be disposed in the recesses 230 to form the bonds 24 including the bond posts 240, typically filling the recesses 230 with bonding material, so that the height of the bond posts 240 is typically equal to the depth of the recesses 230. In some examples of this embodiment, only a plurality of keying posts 240 are included in the keying feature 24, as shown in FIG. 3; in some examples, the bond 24 includes a bonding layer 241 in addition to the plurality of bonding pillars 240, as shown in fig. 2 (d), the bonding layer 241 covers a surface of the sacrificial layer 23 away from the carrier substrate 21 and is bonded to an end of the bonding pillar 240.

It will be appreciated that since the bottom of the groove 230 is an exposed epitaxial layer of the LED chip 22, the bonding material in the groove 230 will adhere to the epitaxial layer of the LED chip 22, and the bonding post 240 will bond with the epitaxial layer of the LED chip 22. It can be understood that, because the upper surface of the sacrificial layer 23 is higher than the side of the LED chip 22 away from the carrier substrate 21, the end of the bonding column 240 away from the carrier substrate 21 is farther away from the carrier substrate 21 than the chip electrode of the LED chip 22 is away from the carrier substrate 21.

In some examples of the embodiment, the bonding material has a certain fluidity and can be deformed to a certain extent, for example, it is a liquid or an incompletely cured adhesive material, and the process of setting the bonding member is described below with reference to the flowchart shown in fig. 4, taking a liquid adhesive material as an example:

s402: and arranging a liquid rubber material on the surface of the sacrificial layer far away from the bearing substrate, wherein one part of the rubber material covers the surface of the sacrificial layer, and the other part of the rubber material flows into the groove.

In some examples of the embodiment, the liquid glue material may be a BCB (benzocyclobutene) glue material. In other examples, the liquid glue material may also be a photoresist (e.g., SU8 or SOG). The liquid glue material may be disposed on the surface of the sacrificial layer 23 away from the carrier substrate 21 by spin coating or coating, and because the glue material has a certain fluidity, a part of the liquid glue material may flow into the groove 230 and be combined with the epitaxial layer of the LED chip 22 at the bottom of the groove to form the bonding post 240. Another portion will remain on the surface of the sacrificial layer 23 for forming a bonding layer 241 integral with the bonding column 240.

S404: and curing the adhesive material to form a bonding piece comprising a bonding layer and a plurality of bonding columns.

Then, the liquid glue material is cured, after the liquid glue material in the groove 230 is cured, a bonding column 240 can be formed, after the liquid glue material on the upper surface of the sacrificial layer 23 is cured, a bonding layer 241 is formed, the bonding layer 241 and the bonding column 240 are integrated, and one end of the bonding column 240, which is far away from the bonding layer 241, is bonded to the epitaxial layer of the LED chip 22. Some glue material can solidify under normal atmospheric temperature condition, only need wait for liquid glue material oneself to accomplish under this condition solidify can, in some examples, liquid glue material need can solidify through modes such as ultraviolet irradiation, heating, this under this condition, need provide corresponding solidification condition for liquid glue material.

It will be appreciated that if the glue used is not fully cured, the fluidity may not be strong, and in this case, after the glue is placed on the sacrificial layer 23, it may be necessary to deform the glue by molding or the like, so that a portion of the glue is embedded in the groove 230 to form the bonding post 240 and another portion of the glue remains on the upper surface of the sacrificial layer 23 to form the bonding layer 241.

In some examples, although the bonding material used has no adhesion, since the bonding material is deposited on the groove 230 and the upper surface of the sacrificial layer 23 by PVD (Physical Vapor Deposition), EV (evaporation), or the like, it is also possible to ensure that the bonding post 240 formed in the groove 230 can be bonded to the epitaxial layer of the LED chip 22.

S110: and bonding one side of the bonding piece, which is far away from the epitaxial layer, with the transfer substrate, and stripping the bearing substrate.

After the key 24 is set, the side of the key 24 away from the carrier substrate 21 may be bonded to the transfer substrate 25, as shown in fig. 2 (e). The transfer substrate 25 may include, but is not limited to, any one of a sapphire substrate, a silicon substrate, a gallium nitride substrate, and the like. When bonding the bonding elements 24 to the transfer substrate 25 on the side of the bonding elements 24 away from the carrier substrate 21, if the bonding elements 24 themselves have adhesiveness, the bonding elements 24 can be directly adhered to one surface of the transfer substrate 25; if the bonding element 24 itself has no tackiness, an adhesive layer may be provided between the bonding element 24 and the transfer substrate 25, and the bonding element 24 and the transfer substrate 25 may be bonded together by the adhesive layer 24, for example, the adhesive layer may be provided on one surface of the transfer substrate 25, and then the one surface of the transfer substrate 25 provided with the adhesive layer may be used to approach the bonding element 24 and be bonded to the bonding element 24. Of course, it will be understood by those skilled in the art that even if the bonding elements 24 themselves are tacky, additional adhesive layers may be provided on the transfer substrate 25.

If the bonding member 24 only includes a plurality of bonding posts 240, the bonding member 24 is directly bonded to the transfer substrate 25 through the bonding posts 240, as shown in fig. 5; if the bonding layer 241 is further included in the bonding element 24, the transfer substrate 25 is bonded on a side of the bonding layer 241 away from the carrier substrate 21, as shown in (e) of fig. 2.

After the LED chip 22 on the carrier substrate 21 is bonded to the transfer substrate 25 by the bonding member 24, the carrier substrate 21 may be peeled off as shown in (f) of fig. 2, so that the LED chip 22 is transferred from the carrier substrate 21 onto the transfer substrate 25. In some examples of the present embodiment, LLO (laser lift off) may be used to separate the LED chip 22 from the carrier substrate 21.

S112: and removing the sacrificial layer.

After the LED chip 22 is transferred from the carrier substrate 21 to the transfer substrate 25, the sacrificial layer 23 may be removed, and a LED chip assembly 20 provided in the present embodiment is obtained, in which the LED chip 22 in the LED chip assembly 20 is supported on the transfer substrate 25 through the bonding member 24 in the air, as shown in (g) in fig. 2, it can be understood that in (g) in fig. 2, the bonding member 24 includes the bonding post 240 and the bonding layer 241, and thus the bonding layer 241 and the bonding post 240 are included between the LED chip 22 and the transfer substrate 25, but if the bonding layer 240 is not included in the bonding member 24, only the bonding post 240 is disposed between the transfer substrate 25 and the LED chip 22, and the LED chip 22 is supported on the transfer substrate 25 through only the bonding post 240.

In some examples of this embodiment, when removing the sacrificial layer 23, a wet etching process may be used, for example, when the sacrificial layer 23 is SiO ₂ The material can be removed by BOE (buffered oxide etchant).

Since the LED chip 22 is supported on the transfer substrate 25 mainly by the bonding member 24, and the bonding posts 240 in the bonding member 24 are elongated, the connection between the LED chip 22 formed by the bonding posts 240 and the transfer substrate 25 is easily broken by an external force: for example, in some examples, the bonding posts 240 are easily dislodged from the epitaxial layers of the LED chip 22, as shown in fig. 6 a; in other examples, the bond post 240 is susceptible to breakage, as shown in FIG. 6 b; in still other examples, the bond posts 240 are easily dislodged from the transfer substrate 25 side, as shown in fig. 6 c. Therefore, the bonding posts 240 are substantially a weakened connection structure between the LED chip 22 and the transfer substrate 25, which can ensure that the LED chip 22 can be easily and rapidly separated from the transfer substrate 25 when the LED chip 22 is picked up from the LED chip assembly 20, and is beneficial to improving the transfer efficiency and the transfer yield of the LED chip 22.

Also provided in this embodiment is an LED chip assembly as shown in fig. 2 (f), in which the sacrificial layer 23 is not removed. It is understood that, in the case where the sacrificial layer 23 is not removed, the bonding pillars 240 in the bonding element 24 are not easily broken or peeled off from the LED chip 22 and the transfer substrate 25 under the protection of the sacrificial layer 23. Therefore, the LED chip assembly is suitable for the application situation that the LED chip can be used for preparing the display panel only after the preparation of the LED chip assembly is finished and a transportation process with long time and poor conditions is required, and because the bonding column 24 in the LED chip assembly cannot be broken or fall off from the LED chip 22 and the transfer substrate 25 due to external force impact in the transportation and carrying processes, the quality of the LED chip assembly is favorably enhanced, and the loss of the LED chip caused by the transportation process is avoided.

In some examples of the present embodiment, after the sacrificial layer 23 is removed, a passivation layer 26 may be further disposed on the LED chip 22 to perform passivation protection on the LED chip 22, where the passivation layer 26 serves to electrically isolate an epitaxial layer of the LED chip 22 from the outside and to perform water and oxygen isolation on the epitaxial layer, and the passivation layer 26 may improve reliability of the LED chip 22 and enhance quality of the LED chip 22. In some examples of the present embodiment, the passivation layer 26 may include, but is not limited to, siO ₂ (silicon oxide) and Al ₂ O ₃ (alumina). In some examples of the present embodiment, the passivation layer may be disposed on the surface of the LED chip 22 through an ALD (atomic layer deposition) process. Of course, it will be understood by those skilled in the art that the passivation layer 26 may be provided in a manner other than ALD, such as evaporation, PVD, CVD (Chemical)Vapor Deposition), and the like are possible.

The description will be made by taking an example of disposing a passivation layer on the basis of (f) of fig. 2 by the ALD process: referring to fig. 7, since the chip electrode of the LED chip 22 is exposed, in this case, the passivation layer 26 is disposed to cover not only the epitaxial layer of the LED chip 22 but also the exposed surfaces of the chip electrode. Meanwhile, the passivation layer 26 also covers the surface of the bonding layer 241.

It can be understood that, because the material of the sacrificial layer 23 is the same as the material of the passivation layer 26 in some cases, when the sacrificial layer 23 is removed in these examples, all the sacrificial layer 23 is not removed indiscriminately, but is selectively removed, for example, when the sacrificial layer 23 is removed in some examples, the sacrificial layer 23 covering the side of the epitaxial layer facing the transfer substrate 25 in the LED chip 22 may be etched to a depth that is at most equal to the thickness of the sacrificial layer 23 in this area, in which case, after the etching is finished, the sacrificial layer 23 will not cover the side of the epitaxial layer facing the transfer substrate 25; in other examples, the etching depth may be smaller than the thickness of the sacrificial layer 23 in this area, but larger than the distance between the side of the sacrificial layer 23 facing the transfer substrate 25 and the free end of the chip electrode, that is, in this case, the sacrificial layer 23 covers the surface of the epitaxial layer facing the transfer substrate 25 after the etching is finished, but does not block the free end of the chip electrode, and this etched portion of the sacrificial layer 23 is referred to as a first portion 231, as shown in fig. 8. On the other hand, the sacrificial layer 23 in the area between the adjacent LED chips 22 may also be etched, the etching depth of the etching is equal to the thickness of the sacrificial layer 23 in the area, and the etching width w is smaller than the width L of the gap between the adjacent LED chips 22, and this part of the etched sacrificial layer 23 is referred to as a second part 232 herein. Since the etching width w of the region between the adjacent LED chips 22 is smaller than the width L of the gap between the adjacent LED chips 22, after the etching is finished, a part of the remaining sacrificial layer 23 covers the side surface of the epitaxial layer of the LED chip 22. Referring to fig. 8, after the first portion 231 and the second portion 232 of the sacrificial layer 23 are etched away, the remaining sacrificial layer 23 covers the side surface of the epitaxial layer of the LED chip 22 and the surface of the epitaxial layer facing the transfer substrate 25, and the remaining sacrificial layer 23 can also play a role of passivating the LED chip 22 to a certain extent. In some examples of the present embodiment, after the sacrificial layer 23 is selectively etched, the passivation layer 26 may be further disposed by EV, PVD, CVD, ALD, or the like to form a more complete coating on the LED chip 22.

In the process of transferring the LED chip from the supporting substrate to the transferring substrate, when the connection relationship between the LED chip and the transferring substrate is established, the slender bonding column is disposed by using the molding of the sacrificial layer, on one hand, the bonding column can suspend the LED chip in the air and support the LED chip on the transferring substrate, and on the other hand, when the LED chip is subjected to an external force, for example, when the LED chip is subjected to a pulling force, the connection formed by the bonding column can be easily broken, which is convenient for picking up the LED chip on the transferring substrate. Therefore, the bonding column is used as a weakened connection structure between the LED chip and the transfer substrate, the transfer yield and the transfer efficiency in the LED chip transfer process are improved, and the transfer difficulty and the transfer cost are reduced.

Another alternative embodiment of the present application:

the present embodiment provides a method for transferring an LED chip, which is mainly applied to a process of transferring an LED chip in an LED chip assembly to a driving backplane, please refer to fig. 9 and 10:

s1002: an LED chip assembly is provided.

The LED chip assembly 90 provided in this embodiment may be an LED chip assembly manufactured by the LED chip assembly manufacturing method illustrated in any of the foregoing embodiments, for example, it may be an LED chip assembly without the sacrificial layer 23 and the passivation layer 26, as shown in (a) of fig. 9, or an LED chip assembly without the sacrificial layer 23 and provided with the passivation layer 26, or an LED chip assembly with a residual sacrificial layer. In some examples of the present embodiment, the LED chip assembly 90 may even be the LED chip assembly mentioned in the foregoing embodiments in which the sacrificial layer 23 is not removed.

S1004: and the LED chip on the transfer substrate is anchored by the transfer head, and the connection formed by the bonding column is broken by applying force so as to realize the pickup of the LED chip.

Subsequently, the LED chip 22 can be picked up from the LED chip assembly 90 by a transfer device such as a transfer head 91, and first, the LED chip to be picked up, i.e., the target LED chip, can be anchored by the transfer head 91, and the transfer head 91 anchors the target LED chip, i.e., the transfer head and the target LED chip establish a connection, as shown in (b) of fig. 9. In this embodiment, since the transfer head 91 needs to apply a force to pull the target LED chip from the transfer substrate 25, the connection between the transfer head 91 and the target LED chip should be relatively firm, so in some examples of this embodiment, the transfer head 91 may be a PDMS (Polydimethylsiloxane) transfer head, and in other examples, the transfer head 91 may also be connected to the target LED chip based on a thermal release adhesive. After the transfer head 91 anchors the target LED chip, a force may be applied by the transfer head 91 so that the connection between the LED chip 22 formed by the bonding posts 240 and the transfer substrate 25 is broken, for example, the bonding posts 240 fall off from the epitaxial layer of the LED chip 22, as shown in fig. 6 a; or the bonding posts 240 are easily detached from the transfer substrate 25, as shown in fig. 6 c; also for example, the bond post 240 is easily broken, as shown in FIG. 6 b. In any case, as long as the fixed connection between the LED chip 22 formed by the bonding post 240 and the transfer substrate 25 is broken, the target LED chip is detached from the transfer substrate 25, as shown in fig. 9 (c).

It is understood that if the sacrificial layer 23 is not etched in the LED chip assembly 90 provided in fig. 9 (a), the sacrificial layer 23 should be removed before the LED chip 22 is picked up from the transfer substrate 25 by the transfer head 91, and the sacrificial layer 23 can be removed completely or selectively.

S1006: and bonding the chip electrodes of the picked LED chips to the back plate electrodes of the driving back plate.

After picking up the LED chip 22 from the transfer substrate 25, the chip electrodes of the LED chip 22 may be bonded with the back plate electrodes of the driving back plate 92, as shown in (d) and (e) in fig. 9. In fig. 9, the LED chip 22 is a flip chip structure, and the chip electrodes and the backplane electrodes can be directly bonded together by solder (e.g. solder, gold-tin alloy) or conductive adhesive (conductive silver adhesive, ACF anisotropic conductive film). In other examples, if the LED chip 22 is in a vertical structure or the LED chip 22 is in a normal structure, it may be necessary to use a conductive material such as gold wire when electrically connecting the chip electrode and the back plate electrode.

It is understood that if the surface of the chip electrode of the LED chip 22 is covered by the passivation layer 26, for example, the passivation layer 26 is disposed by an ALD process, the passivation layer 26 covering the free end of the chip electrode needs to be removed before bonding the chip electrode of the LED chip 22 with the backplane electrode of the driving backplane 92, in some examples of the embodiment, only the passivation layer 26 on the free end of the chip electrode may be removed, and in still other examples, the passivation layer on the surface of the chip electrode may be completely removed. In the present embodiment, when the passivation layer 26 at the free end of the chip electrode of the LED chip 22 is removed, the passivation layer 26 to be removed may be etched with a HF (hydrofluoric acid) solution, for example, in an example of the embodiment, the LED chip 22 may be moved onto the substrate 94 with the HF solution 93 on the surface by the transfer head 91, and the passivation layer 26 covering the free end of the chip electrode of the LED chip 22 is contacted with the HF solution 93, as shown in fig. 11, so that the passivation layer 26 covering the free end of the chip electrode is etched and removed with the HF solution 93. It will be appreciated that in some examples the substrate may be a planar substrate with a small amount of HF solution 93 applied to the surface of the planar substrate, as appropriate for the case where only the chip electrode free end passivation layer 26 is removed. In still other examples, the substrate may be a dish-type or tank-type container, which is convenient for holding more HF solution 93, suitable for the case where it is desired to remove all the passivation layer 26 on the chip electrodes.

In some examples of the embodiment, when the transfer head 91 applies a force to break the connection formed by the bonding post 240, the LED chip 22 falls off from the bonding post 240, so that the bonding material on the substrate of the LED chip 22 does not remain, and the bonding between the LED chip 22 and the driving back plate 92 is not affected. However, if the connection formed by the bonding post 240 is broken, or the bonding post 240 falls off from the transfer substrate 25, a part of the bonding material may remain on the LED chip 22, and even the bonding between the LED chip 22 and the driving backplate 92 may be affected, in these cases, after the transfer head 91 picks up the LED chip 22, before bonding the LED chip 22 to the driving backplate 92, all or part of the remaining bonding material needs to be removed, and in some examples of this embodiment, the remaining bonding material may be removed by laser, wet etching, or the like.

The present embodiment further provides a display panel, as shown in fig. 12, the display panel 12 includes a driving back plate 92 and a plurality of LED chips 22, where the plurality of LED chips 22 include a red chip, a green chip and a blue chip, and in some examples, the plurality of LED chips 22 may further include chips of other colors. The chip electrodes of the LED chips 22 are bonded to the backplane electrodes of the driving backplane 92, and these LED chips can be transferred to the driving backplane 92 by any of the aforementioned LED chip transfer methods.

According to the LED chip transfer method and the display panel manufactured based on the LED chip transfer method, due to the existence of the weakened connection structure, namely the bonding column, in the LED chip assembly, the difficulty of transferring the LED chip from the transfer substrate to the driving backboard can be reduced, the manufacturing efficiency of the display panel is improved, and the cost of the display panel is reduced.

Yet another alternative embodiment of the present application:

in order to make the advantages and details of the LED chip assembly, the manufacturing method thereof, the display panel, and the LED chip transferring method provided in the foregoing examples clearer, the present embodiment will further describe the scheme of the foregoing embodiments with reference to an example, please refer to the schematic diagram of the manufacturing flow of the display panel shown in fig. 13 and the schematic diagram of the process state change of the display panel shown in fig. 14:

s1302: a growth substrate is provided.

In this embodiment, the growth substrate 1401 is provided as shown in fig. 14 (a), and is a growth substrate for growing a blue-green light epitaxial layer, for example, a sapphire substrate, and in other examples, the growth substrate 1401 may also be a silicon substrate or a gallium nitride substrate.

S1304: an epitaxial layer is grown on a growth substrate.

The epitaxial layer 1401 may be placed in a reaction chamber to grow an epitaxial layer 1402 on a growth substrate 1401, the epitaxial layer 1402 including an N-type gallium nitride layer, an active layer, and a P-type gallium nitride layer in the epitaxial layer 1402 in sequence from bottom to top, as shown in fig. 14 (b). Of course, other layer structures, such as buffer layers, stress relief layers, ohmic contact layers, etc., may also be included in epitaxial layer 1402.

S1306: and carrying out mesa etching and groove etching on the epitaxial layer to form a plurality of sub-epitaxial layers.

The grown epitaxial layer 1402 generally has a large area, and in the process of preparing a Mini-LED chip or a Micro-LED chip, one epitaxial layer 1402 can be used for preparing a plurality of LED chips, so that the epitaxial layer 1402 needs to be etched to divide the epitaxial layer 1402 into a plurality of sub-epitaxial layers, and thus the epitaxial layer 1402 is etched from a plurality of independent portions in one overall atmosphere to trench etching. Meanwhile, the LED chip prepared in this embodiment is a flip chip, and therefore, in order to expose the N-type gallium nitride layer covered by the P-type gallium nitride layer and the active layer to form an electrode setting region of the N electrode, mesa etching may be performed on the epitaxial layer in this embodiment. It can be understood that the mesa etching and the trench etching may be performed simultaneously, sequentially, and in any order. After the etching is completed, each sub-epitaxial layer is shown in fig. 14 (c).

S1308: and arranging chip electrodes on the sub-epitaxial layers to form a plurality of LED chips.

After the electrode arrangement region of the N electrode in the sub-epitaxial layer is exposed, a chip electrode may be arranged in the electrode arrangement region to produce an LED chip 1403, as shown in fig. 14 (d). When the chip electrode is arranged, an electrode layer may be formed in the electrode arrangement region by PVD, CVD, EV, or the like, and the electrode layer may be a metal layer (such as a copper layer, a gold layer), or a non-metal layer (such as a CNT carbon nanotube layer) having a good reaching performance. The electrode layer may then be patterned to form chip electrodes.

S1310: full-face deposition of SiO on growth substrate ₂ A layer.

Preparation of LED chip 1403After completion, siO may be provided on the side of the growth substrate 1401 provided with the LED chip 1403 ₂ Layer 1404 acts as a sacrificial layer, as in (e) of fig. 14. Each LED chip 1403 is not covered by SiO ₂ In layer 1404.

S1312: to SiO ₂ And etching the layer to form a plurality of grooves with the surface of the sub-epitaxial layer as the groove bottom.

In this embodiment, for SiO ₂ When the layer 1404 is etched, each LED chip 1403 uniquely corresponds to one etched position, and the etched position is opposite to the position of the P-type gallium nitride layer in the LED chip 1403, so that after the etching is completed, a plurality of grooves 1405 corresponding to the LED chips 1403 one to one are formed, the grooves 1405 are in a long and thin column shape, and the surface of the neutron epitaxial layer in the LED chip 1403 is exposed from the bottom of the groove, as shown in (f) in fig. 14. The cross section of the groove 1405 can be circular or rectangular, and can also be in other irregular shapes.

S1314: in SiO ₂ BCB glue is arranged on the layer to form a bonding piece comprising a bonding column and a bonding layer.

After the grooves 1405 are formed, they may be formed in SiO ₂ Liquid BCB glue is coated on the layer 1404, flows into the groove 1405, and covers SiO with another part ₂ The upper surface of layer 1404. After the BCB glue is cured, a bonding member may be formed by using the BCB glue, and it is obvious that in this embodiment, the bonding member includes a bonding layer 1406 and a bonding column 1407, the bonding column 1407 is integrally formed with the bonding layer 1406, and one end of the bonding column 1407 far from the bonding layer 1406 is attached to the surface of the P-type gallium nitride layer of the LED chip 1403, as shown in (g) in fig. 14. In this embodiment, a heating curing method is adopted when the BCB glue is cured, and the curing temperature is less than 250 ℃.

S1316: and bonding the bonding layer and the transfer substrate together, and stripping the growth substrate.

Referring to fig. 14 (h), a side of the transfer substrate 1408 may be used to adhere the bonding layer 1406 to a side away from the bonding posts 1407, so that the transfer substrate 1408 and the bonding layer 1406 are bonded together. The growth substrate 1401 may then be peeled off, in this embodiment the growth substrate 1401 is removed by means of laser lift-off, as in (i) of fig. 14.

S1318: removal of SiO ₂ And (3) a layer.

After the growth substrate 1401 is peeled off, the SiO may be removed by wet etching or the like ₂ Layer 1404, as shown in FIG. 14 (j), for example, by placing transfer substrate 1408 and the components attached to transfer substrate 1408 together in a BOE solution, e.g., etching away SiO by the BOE solution ₂ Layer 1404. Of course, in other examples of the present embodiment, the selected solution may be a solution other than the BOE solution, but it is only necessary to ensure that the selected solution and the SiO solution are compatible ₂ The reaction speed of the layer 1404 is much greater than that of the transfer substrate 1408 and the LED chips 1403.

S1320: al for coating LED chip by ALD process ₂ O ₃ A layer.

Removal of SiO ₂ After layer 1404, al can be provided over LED chip 1403 using an ALD process ₂ O ₃ Layer 1409, understandably, of Al ₂ O ₃ The layer 1409 also adheres to the upper surface of the transfer substrate 1408 as shown in (k) of fig. 14. It is understood that Al ₂ O ₃ Layer 1409 can realize that LED chip 1403 neutron epitaxial layer is kept apart with outside electrical isolation and water oxygen, promotes LED chip 1403's reliability, simultaneously because LED chip 1403 is flip-chip LED chip, al ₂ O ₃ The layer 1409 covers the light emitting surface of the LED chip 1403 because of Al ₂ O ₃ The refractive index of the layer 1409 can also improve the light extraction effect of the LED chip 1403.

In some scenarios, the manufacturer of the LED chip 14203 is independent from the display panel manufacturer, and the manufacturer of the LED chip 1403 can provide the product obtained in any of steps S1316, S1318, and S1320 as an LED chip assembly to the display panel manufacturer.

S1322: and picking up the LED chip from the transfer substrate by using a PDMS transfer head.

When transferring the LED chips 1403 from the transfer substrate 1408 to the driving backplane, the LED chips 1403 on the transfer substrate 1408 may be bonded using the PDMS transfer head 1410, as shown in (l) in fig. 14, and then a tensile force is applied to the LED chips 1403 through the PDMS transfer head 1410, so that the LED chips 1403 are separated from the bonding posts 1407, as shown in (m) in fig. 14.

S1324: moving the LED chip carried by the PDMS transfer head to a substrate with the surface covered with HF solution, and removing Al covering the free end of the chip electrode ₂ O ₃ A layer.

Because the chip electrodes of the LED chip 1403 are also covered with Al ₂ O ₃ Layer 1409 of Al ₂ O ₃ Layer 1409 is not electrically conductive, and thus, before bonding the chip electrodes of LED chip 1403 to the backplane electrodes of the driving backplane, al at the free ends of the chip electrodes needs to be removed ₂ O ₃ In the embodiment of the layer 1409, a layer of HF solution 1411 may be coated on a flat surface of a substrate, and then the PDMS transfer head 1410 is moved to the substrate with the LED chip 1403, so that the chip electrode of the LED chip 1403 is in contact with the HF solution 1411, and the HF solution 1411 is used to remove Al at the free end of the chip electrode ₂ O ₃ Layer, as in (n) of fig. 14.

S1326: and bonding the chip electrode of the LED chip with the backboard electrode of the driving backboard to obtain the display panel.

Subsequently, the LED chip 1403 is transferred onto the driving back plate 1412, and chip electrodes of the LED chip 1403 and back plate electrodes of the driving back plate 1412 are soldered together. After the LED chips 1403 required for driving the back plate 1412 are all transferred and bonded, the display panel 14 can be manufactured as shown in (o) of fig. 14.

The embodiment provides a preparation scheme of a display panel, in the scheme, the transfer of the LED chip is simplified by preparing the weakened connection structure, the transfer yield and efficiency of the LED chip are improved, and the production cost is reduced.

It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.

Claims

1. A method for preparing an LED chip assembly is characterized by comprising the following steps:

providing a bearing substrate with a plurality of LED chips;

etching the sacrificial layer from one surface of the sacrificial layer, which is far away from the bearing substrate, so as to form a plurality of columnar grooves, wherein the grooves take the surface of the epitaxial layer of the LED chip as the bottom surface of the grooves;

arranging bonding materials in the grooves to form bonding pieces comprising bonding columns, wherein one ends of the bonding columns are combined with the surface of the epitaxial layer, and the distance between the other ends of the bonding columns and the bearing substrate is larger than the distance between the free ends of the chip electrodes in the LED chip and the bearing substrate;

bonding one side of the bonding piece, which is far away from the bearing substrate, with a transfer substrate, and stripping the bearing substrate;

and removing the sacrificial layer.

2. The method of making an LED chip assembly of claim 1, wherein after said removing said sacrificial layer, further comprising:

and arranging a passivation layer coating the epitaxial layer.

3. The method of manufacturing an LED chip assembly according to claim 1, wherein the sacrificial layer comprises at least one of silicon oxide and aluminum oxide, and the removing the sacrificial layer comprises:

etching the sacrificial layer covered on one surface of the epitaxial layer facing the transfer substrate, wherein the etching depth is less than or equal to the thickness of the sacrificial layer in the area and is greater than the distance from one surface of the sacrificial layer facing the transfer substrate to the free end of the chip electrode; and etching the sacrificial layer in the area between the adjacent LED chips, wherein the etching depth is equal to the thickness of the sacrificial layer in the area, and the etching width is smaller than the width of the gap between the adjacent LED chips.

4. The method for preparing an LED chip assembly according to any one of claims 1 to 3, wherein the area of the P-type semiconductor layer in the epitaxial layer is smaller than that of the N-type semiconductor layer, and the orthographic projection of the groove on the epitaxial layer is positioned on the P-type semiconductor layer.

5. The method of preparing an LED chip assembly according to any of claims 1-3, wherein the disposing a bonding material in the recess to form a bond comprising a bond post comprises:

arranging a liquid glue material on the surface of the sacrificial layer far away from the bearing substrate, wherein one part of the glue material covers the surface of the sacrificial layer, and the other part of the glue material flows into the groove;

and curing the glue material to form a bonding piece comprising a bonding layer and a plurality of bonding columns.

6. An LED chip transfer method, comprising:

providing an LED chip assembly prepared according to the LED chip assembly preparation method of any one of claims 1 to 5;

anchoring the LED chip on the transfer substrate through a transfer head, and applying force to break the connection formed by the bonding column so as to realize the pickup of the LED chip;

bonding the picked chip electrodes of the LED chips to the backboard electrodes of the driving backboard.

7. The LED chip transfer method according to claim 6, wherein if the surface of the chip electrodes is coated with a passivation layer, before the bonding the chip electrodes of the picked LED chips to the back plate electrodes of the driving back plate, further comprising:

and removing the passivation layer covering the free end of the chip electrode.

8. The LED chip transfer method of claim 7, wherein the passivation layer is at least one of aluminum oxide and silicon oxide, and the removing the passivation layer covering the free ends of the chip electrodes comprises:

and carrying the LED chip by the transfer head to move to the substrate with the surface covered with hydrofluoric acid solution, and corroding and removing the passivation layer covered at the free end of the chip electrode by the hydrofluoric acid solution.

9. An LED chip assembly, wherein the LED chip assembly is prepared by the method for preparing the LED chip assembly according to any one of claims 1 to 5.

10. A display panel, characterized in that the display panel comprises a driving back plate and a plurality of LED chips, chip electrodes of the LED chips are electrically connected with back plate electrodes of the driving back plate, and the LED chips are transferred onto the driving back plate by using the LED chip transfer method according to any one of claims 6 to 8.