阅读说明：本技术 微led芯片、生长基板、显示面板以及微led芯片的转移方法 (Micro LED chip, growth substrate, display panel and micro LED chip transfer method ) 是由 姚志博 夏继业 董小彪 王程功 于 2019-10-28 设计创作，主要内容包括：本申请公开了一种微LED芯片、生长基板、显示面板以及微LED芯片的转移方法,所述微LED芯片包括：第一掺杂外延层,包括第一区域和第二区域；发光层,至少覆盖部分所述第一区域；第二掺杂外延层,覆盖所述发光层远离所述第一掺杂外延层一侧表面；第一电极,设置于所述第二区域,且与所述发光层处于同侧；第二电极,设置于所述第二掺杂外延层远离所述发光层一侧,且所述第一电极和所述第二电极在所述第一掺杂外延层上的正投影不重合；其中,所述第一电极和所述第二电极在所述微LED芯片的厚度方向上具有高度差,所述高度差大于0.5微米且小于3微米。通过上述方式,本申请能够在激光剥离后使微LED芯片不全部陷入键合层中,易于转移。(The application discloses little LED chip, growth substrate, display panel and little LED chip's transfer method, little LED chip includes: a first doped epitaxial layer comprising a first region and a second region; a light emitting layer covering at least a part of the first region; the second doped epitaxial layer covers the surface of one side of the light-emitting layer, which is far away from the first doped epitaxial layer; the first electrode is arranged in the second area and is positioned at the same side with the light-emitting layer; the second electrode is arranged on one side, away from the light emitting layer, of the second doped epitaxial layer, and orthographic projections of the first electrode and the second electrode on the first doped epitaxial layer are not overlapped; wherein the first electrode and the second electrode have a height difference in a thickness direction of the micro LED chip, the height difference being greater than 0.5 micrometers and less than 3 micrometers. Through the mode, the micro LED chip can not be completely sunk into the bonding layer after laser stripping, and the transfer is easy.)

1. A micro LED chip, comprising:

a first doped epitaxial layer comprising a first region and a second region;

a light emitting layer covering at least a part of the first region;

the second doped epitaxial layer covers the surface of one side of the light-emitting layer, which is far away from the first doped epitaxial layer;

the first electrode is arranged in the second area and is positioned at the same side with the light-emitting layer;

the second electrode is arranged on one side, away from the light emitting layer, of the second doped epitaxial layer, and orthographic projections of the first electrode and the second electrode on the first doped epitaxial layer are not overlapped;

wherein the first electrode and the second electrode have a height difference in a thickness direction of the micro LED chip, the height difference being greater than 0.5 micrometers and less than 3 micrometers.

2. The micro LED chip of claim 1,

the first electrode and the second electrode have the same thickness.

3. The micro LED chip of claim 2,

and in the direction from the first doped epitaxial layer to the second electrode, the section of the second electrode is in an inverted trapezoid shape, and/or the section of the first electrode is in an inverted trapezoid shape.

4. The micro LED chip of claim 1,

the first electrode protrudes from the second electrode, and the section of the part of the first electrode protruding from the second electrode is in an inverted trapezoid shape along the direction from the first doped epitaxial layer to the second electrode.

5. A growth substrate, comprising:

a transparent substrate;

the plurality of micro LED chips of any of claims 1-4, and the first doped epitaxial layer of the micro LED chips is disposed proximate to the transparent substrate.

6. A display panel, comprising:

the device comprises a driving substrate, a plurality of solder columns arranged in an array manner, a plurality of welding wire columns arranged in an array manner and a plurality of welding wire columns arranged in a matrix manner, wherein one side of the driving substrate is provided with a plurality of welding wire columns;

a plurality of the micro LED chips of any one of claims 1-4, the first and second electrodes of the micro LED chips being electrically connected with solder columns at corresponding locations, respectively, and the solder columns at corresponding locations of the first and second electrodes having the height difference therebetween.

7. A method for transferring micro LED chips, the method comprising:

providing a growth substrate, wherein the growth substrate comprises a transparent substrate and a plurality of micro LED chips positioned on the transparent substrate; the micro LED chip includes: the first doped epitaxial layer is positioned on the transparent substrate and comprises a first area and a second area; a light emitting layer covering at least a part of the first region; the second doped epitaxial layer covers the surface of one side of the light-emitting layer, which is far away from the first doped epitaxial layer; the first electrode is arranged in the second area and is positioned at the same side with the light-emitting layer; the second electrode is arranged on one side, far away from the light emitting layer, of the second doped epitaxial layer, orthographic projections of the first electrode and the second electrode on the first doped epitaxial layer are not overlapped, a height difference exists between the first electrode and the second electrode in the thickness direction of the micro LED chip, and the height difference is larger than 0.5 micrometer and smaller than 3 micrometers;

embedding one side of the growth substrate, which is provided with a plurality of micro LED chips, into a bonding layer of a temporary substrate, wherein a protruding part of one protruding electrode of a first electrode and a second electrode of the micro LED chips, which are positioned on the same side, is positioned in the bonding layer, and at least part of the other electrode is positioned outside the bonding layer;

laser is irradiated from one side of a transparent substrate of the growth substrate, so that the transparent substrate is separated from the first doped epitaxial layer;

removing the transparent substrate;

and transferring the micro LED chip.

8. The transfer method according to claim 7, wherein embedding the side of the growth substrate where the plurality of micro LED chips are arranged in a bonding layer of a temporary substrate comprises:

and approaching the growth substrate to the bonding layer until the surface of one side, close to the growth substrate, of the bonding layer is flush with the surface of one side, away from the transparent substrate, of the other electrode.

9. The transfer method of claim 7, wherein the providing a growth substrate comprises:

and simultaneously and respectively forming the first electrode and the second electrode on the second area of the first doped epitaxial layer and the side of the second doped epitaxial layer, which is far away from the light-emitting layer, wherein the thicknesses of the first electrode and the second electrode are the same.

10. The transfer method according to claim 9, characterized in that the transfer method further comprises:

etching the first electrode and the second electrode so that the cross section of the first electrode is in an inverted trapezoid shape along the first doped epitaxial layer to the second electrode; and/or the presence of a gas in the gas,

and etching the second electrode so that the cross section of the second electrode is in an inverted trapezoid shape in the direction from the first doped epitaxial layer to the second electrode.

Technical Field

The application relates to the technical field of display, in particular to a micro LED chip, a growth substrate, a display panel and a micro LED chip transfer method.

Background

The micro LED (Light Emitting Diode) chip display technology has the advantages of high brightness, high response speed, low power consumption, long service life, and the like, and becomes a research hotspot for people to pursue a new generation of display technology.

At present, laser stripping and batch transfer are two very important processes in the preparation process of the micro LED display panel. The specific process of batch transfer is as follows: the plurality of micro LED chips are transferred by a transfer head.

The problem that a micro LED chip is not easy to pick up in the transferring process exists in the prior art.

Disclosure of Invention

The technical problem mainly solved by the application is to provide a micro LED chip, a growth substrate, a display panel and a transfer method of the micro LED chip, wherein the micro LED chip can not be completely sunk into a bonding layer after laser stripping, and the transfer is easy.

In order to solve the technical problem, the application adopts a technical scheme that: providing a micro LED chip, the micro LED chip comprising: a first doped epitaxial layer comprising a first region and a second region; a light emitting layer covering at least a part of the first region; the second doped epitaxial layer covers the surface of one side of the light-emitting layer, which is far away from the first doped epitaxial layer; the first electrode is arranged in the second area and is positioned at the same side with the light-emitting layer; the second electrode is arranged on one side, away from the light emitting layer, of the second doped epitaxial layer, and orthographic projections of the first electrode and the second electrode on the first doped epitaxial layer are not overlapped; wherein the first electrode and the second electrode have a height difference in a thickness direction of the micro LED chip, the height difference being greater than 0.5 micrometers and less than 3 micrometers.

Wherein the first electrode and the second electrode have the same thickness. The design mode can enable the first electrode and the second electrode to be formed simultaneously, and the preparation process is simplified.

And the section of the second electrode is in an inverted trapezoid shape in the direction from the first doped epitaxial layer to the second electrode, and/or the section of the first electrode is in an inverted trapezoid shape. The design mode of the inverted trapezoid can reduce the adhesion of the bonding layer to the micro LED chip during pickup and improve the transfer efficiency.

The first electrode protrudes from the second electrode, and the section of the part of the first electrode protruding from the second electrode is in an inverted trapezoid shape along the direction from the first doped epitaxial layer to the second electrode. The design mode of the inverted trapezoid can reduce the adhesion of the bonding layer to the micro LED chip during pickup and improve the transfer efficiency.

In order to solve the above technical problem, another technical solution adopted by the present application is: providing a growth substrate, the growth substrate comprising: a transparent substrate; the plurality of micro LED chips of any of the above embodiments, wherein the first doped epitaxial layer of the micro LED chip is disposed adjacent to the transparent substrate.

In order to solve the above technical problem, the present application adopts another technical solution: provided is a display panel including: the device comprises a driving substrate, a plurality of solder columns arranged in an array manner, a plurality of welding wire columns arranged in an array manner and a plurality of welding wire columns arranged in a matrix manner, wherein one side of the driving substrate is provided with a plurality of welding wire columns; in a plurality of the micro LED chips described in any of the above embodiments, the first electrode and the second electrode of the micro LED chip are electrically connected to the solder columns at the corresponding positions, respectively, and the height difference exists between the solder columns at the corresponding positions of the first electrode and the second electrode.

In order to solve the above technical problem, the present application adopts another technical solution: provided is a transfer method of a micro LED chip, the transfer method including: providing a growth substrate, wherein the growth substrate comprises a transparent substrate and a plurality of micro LED chips positioned on the transparent substrate; the micro LED chip includes: the first doped epitaxial layer is positioned on the transparent substrate and comprises a first area and a second area; a light emitting layer covering at least a part of the first region; the second doped epitaxial layer covers the surface of one side of the light-emitting layer, which is far away from the first doped epitaxial layer; the first electrode is arranged in the second area and is positioned at the same side with the light-emitting layer; the second electrode is arranged on one side, far away from the light emitting layer, of the second doped epitaxial layer, orthographic projections of the first electrode and the second electrode on the first doped epitaxial layer are not overlapped, a height difference exists between the first electrode and the second electrode in the thickness direction of the micro LED chip, and the height difference is larger than 0.5 micrometer and smaller than 3 micrometers; embedding one side of the growth substrate, which is provided with a plurality of micro LED chips, into a bonding layer of a temporary substrate, wherein a protruding part of one protruding electrode of a first electrode and a second electrode of the micro LED chips, which are positioned on the same side, is positioned in the bonding layer, and at least part of the other electrode is positioned outside the bonding layer; laser is irradiated from one side of a transparent substrate of the growth substrate, so that the transparent substrate is separated from the first doped epitaxial layer; removing the transparent substrate; and transferring the micro LED chip.

Wherein, the embedding of one side of the growth substrate, on which a plurality of micro LED chips are disposed, into the bonding layer of the temporary substrate includes: and approaching the growth substrate to the bonding layer until the surface of one side, close to the growth substrate, of the bonding layer is flush with the surface of one side, away from the transparent substrate, of the other electrode. The design mode can reduce the pressure required for pressing the growth substrate and reduce the probability that the growth substrate is crushed on the premise of ensuring that the micro LED chip in the growth substrate is fixed by the bonding layer.

Wherein the providing a growth substrate comprises: and simultaneously and respectively forming the first electrode and the second electrode on the second area of the first doped epitaxial layer and the side of the second doped epitaxial layer, which is far away from the light-emitting layer, wherein the thicknesses of the first electrode and the second electrode are the same. This design may be such that the first and second electrodes are formed simultaneously.

Wherein the transfer method further comprises: etching the first electrode and the second electrode so that the cross section of the first electrode is in an inverted trapezoid shape along the first doped epitaxial layer to the second electrode; and/or etching the second electrode, so that the cross section of the second electrode is in an inverted trapezoid shape along the direction from the first doped epitaxial layer to the second electrode. The design mode of the inverted trapezoid can reduce the adhesion of the bonding layer to the micro LED chip during pickup and improve the transfer efficiency.

The beneficial effect of this application is: different from the prior art, the micro LED chip provided by the present application is a lateral LED chip, and a height difference exists between the first electrode and the second electrode on the same side, where the height difference is greater than 0.5 micrometers and less than 3 micrometers. When the growth substrate with the micro LED chip is pressed into the bonding layer during laser stripping, due to the existence of height difference, the electrode closer to the bonding layer is firstly pressed into the bonding layer, when the electrode farther away from the bonding layer contacts the bonding layer, the growth substrate is subjected to adhesive layer resistance fed back by the first electrode and the second electrode on different planes, and the two adhesive layer resistances can generate a moment for rotating the micro LED chip; because the electrode pressed into the bonding layer is fixed by the adhesive layer, the rotation resistance of the micro LED chip is very large, and the rotation resistance can prevent the micro LED chip from being continuously pressed into the adhesive layer, so that part of the micro LED chip is finally positioned outside the bonding layer; when the pick-up and transfer head is subsequently used for transferring the micro LED chip, the pick-up resistance is small, the transfer is easy, and the transfer efficiency is high. In addition, when the laser is stripped, the height difference in the numerical range can reduce the pressure required for pressing the growth substrate and reduce the probability of crushing the growth substrate on the premise that the micro LED chip in the growth substrate is fixed by the bonding layer.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts. Wherein:

FIG. 1 is a schematic structural diagram of an embodiment of a micro LED chip according to the present application;

FIG. 2 is a schematic structural diagram of another embodiment of a micro LED chip according to the present application;

FIG. 3 is a schematic structural diagram of another embodiment of a micro LED chip according to the present application;

FIG. 4 is a schematic structural diagram of an embodiment of a growth substrate according to the present application;

FIG. 5 is a schematic structural diagram of an embodiment of a display panel according to the present application;

FIG. 6 is a schematic structural diagram of another embodiment of a display panel according to the present application;

FIG. 7 is a schematic flow chart illustrating an embodiment of a micro LED chip transfer method according to the present application;

fig. 8 is a schematic structural diagram of an embodiment corresponding to steps S101 to S105 in fig. 7.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The inventor of the application finds that the specific process of laser lift-off is as follows in the long-term research process: firstly, completely pressing a plurality of micro LED chips with transparent substrates into a bonding layer so as to fix the micro LED chips by the bonding layer; then, laser light is irradiated from the transparent substrate side to separate the plurality of micro LED chips from the transparent substrate. Because the LED chip is completely sunk into the bonding layer during laser stripping, the follow-up transfer head is difficult to pick up the LED chip and is laborious to move and take.

Based on this, the micro LED chip of the embodiment provided in the present application has a portion located outside the bonding layer; when the pick-up and transfer head is subsequently used for transferring the micro LED chip, the pick-up resistance is small, the transfer is easy, and the transfer efficiency is high.

Referring to fig. 1, fig. 1 is a schematic structural diagram of an embodiment of a micro LED chip of the present application, and the micro LED chip 10 is a lateral LED chip capable of emitting red light, green light, blue light, violet light, and the like, and includes a first doped epitaxial layer 100, a light emitting layer 102, a second doped epitaxial layer 104, a first electrode 106, and a second electrode 108.

Specifically, the first doped epitaxial layer 100 includes a first region (not labeled) and a second region (not labeled), the light emitting layer 102 covers at least a portion of the first region, and the second doped epitaxial layer 104 covers a surface of the light emitting layer 102 away from the first doped epitaxial layer 100 and does not cover the second region of the first doped epitaxial layer 100. The first electrode 106 is disposed in the second region and on the same side as the light-emitting layer 102; the second electrode 108 is disposed on a side of the second doped epitaxial layer 104 away from the light emitting layer 102, and orthographic projections of the first electrode 106 and the second electrode 108 on the first doped epitaxial layer 100 are not overlapped; the first electrode 106 and the second electrode 108 have a height difference Δ h in the thickness direction of the micro LED chip 10, where the height difference Δ h is greater than 0.5 micrometers and less than 3 micrometers, for example, 1 micrometer and 2 micrometers, and the probability that the growth substrate is crushed can be further effectively reduced. It should be noted that the height difference range is set as a result of comprehensively considering the bonding process and the pickup process. If the height difference range is greater than 3 μm, the manufacturing process of the first electrode 106 and the second electrode 108 is complicated, and raw materials are wasted; and the pressure required when the electrodes of the micro LED chip 10 are pressed into the bonding layer is large, which may cause the growth substrate or the temporary substrate to be crushed; in addition, when the micro LED chip 10 is picked up from the bonding layer after the transparent substrate of the growth substrate is stripped off by laser, the resistance received by the bonding layer is large, and the pickup efficiency is reduced.

When the growth substrate on which the micro LED chip 10 grows is pressed into the bonding layer during laser lift-off, due to the height difference Δ h, the electrode closer to the bonding layer is pressed into the bonding layer first, and when the electrode farther from the bonding layer contacts the bonding layer, the growth substrate receives adhesive layer resistances fed back from the first electrode 106 and the second electrode 108 on different planes, and the two adhesive layer resistances generate a moment for rotating the micro LED chip 10; since the electrode pressed into the bonding layer is fixed by the adhesive layer, the resistance to rotation of the micro LED chip 10 is large, and the rotation resistance can prevent the micro LED chip 10 from being pressed into the adhesive layer, so that the micro LED chip 10 is partially located outside the bonding layer; when the micro LED chip 10 is transferred by the pick-up transfer head, the pick-up resistance is small, the transfer is easy, and the transfer efficiency is high.

The first doped epitaxial layer 100 in the above embodiments may be an N-type doped epitaxial layer, the corresponding first electrode 106 may be an N electrode, the second doped epitaxial layer 104 may be a P-type doped epitaxial layer, and the second electrode 108 may be a P electrode. Alternatively, the first doped epitaxial layer 100 in the above embodiments may be a P-type doped epitaxial layer, the corresponding first electrode 106 may be a P-electrode, the second doped epitaxial layer 104 may be an N-type doped epitaxial layer, and the second electrode 108 may be an N-electrode. The P electrode and the N electrode may be common metals such as Cr, Pt, and Au, and the first doped epitaxial layer 100 and the second doped epitaxial layer 104 may be made of GaAs, GaN, GaP, and the like.

In one embodiment, as shown in fig. 1, the second electrode 108 protrudes from the first electrode 106, and the thickness of the first electrode 106 is the same as that of the second electrode 108. In this design, the first electrode 106 and the second electrode 108 may be formed simultaneously, and the height difference Δ h between the first electrode 106 and the second electrode 108 may be provided by the second doped epitaxial layer 104 or provided by the second doped epitaxial layer 104 and the light emitting layer 102.

Preferably, as shown in fig. 2, fig. 2 is a schematic structural diagram of another embodiment of the micro LED chip of the present application. In a direction along the first doped epitaxial layer 100a to the second electrode 108a, the second electrode 108a has an inverted trapezoid cross section, and/or the first electrode 106a has an inverted trapezoid cross section. In this case, the first electrode 106a and/or the second electrode 108a may have a truncated cone shape or the like. After laser stripping, when the pick-up transfer head removes the micro LED chip 10a from the bonding layer, the adhesion of the bonding layer to the micro LED chip 10a during pick-up can be reduced by the inverted trapezoidal design mode, and the transfer efficiency is improved.

In yet another embodiment, as shown in fig. 3, fig. 3 is a schematic structural diagram of another embodiment of the micro LED chip of the present application. The first electrode 106b protrudes from the second electrode 108b, and a cross section of a portion of the first electrode 106b protruding from the second electrode 108b is an inverted trapezoid in a direction from the first doped epitaxial layer 100b to the second electrode 108 b. During laser lift-off, when the growth substrate on which the micro LED chip 10b grows is pressed into the bonding layer, only the portion of the first electrode 106b protruding the second electrode 108b may be located in the bonding layer, and the resistance of the bonding layer received by the subsequent pick-up transfer head when picking up the micro LED chip 10b is small; and because the section of the part of the first electrode 106b protruding the second electrode 108b is inverted trapezoid, the resistance of the bonding layer on the micro LED chip 10b during picking up can be further reduced, and the transfer efficiency can be improved. Further, in the present embodiment, the angle between the side wall 1060b of the inverted trapezoid and the horizontal plane is between 30 ° and 50 °, for example, 35 °, 40 °, 45 °, and the like. This range of angles is a result of a combination of considerations for the bonding process and for the pick-up process.

Referring to fig. 4, fig. 4 is a schematic structural diagram of an embodiment of a growth substrate according to the present application. The growth substrate 20 includes a transparent substrate 200 and a plurality of micro LED chips 10. The transparent substrate 200 may be a sapphire alumina substrate, a silicon carbide substrate, and the like, the structures of the plurality of micro LED chips 10 may refer to any of the above embodiments, which are not described herein again, the first doped epitaxial layer 100 of the micro LED chip 10 is disposed near the transparent substrate 200, for example, the first doped epitaxial layer 100 may directly contact the transparent substrate 200.

Referring to fig. 5, fig. 5 is a schematic structural diagram of an embodiment of a display panel of the present application, where the display panel 30 includes a driving substrate 300 and a plurality of micro LED chips 10 in any of the above embodiments. A plurality of solder columns 302 arranged in an array are disposed on one side of the driving substrate 300, the solder columns 302 may be made of indium, tin, or the like, and the driving substrate 300 may be disposed with an LED driving circuit, or the like. The first electrode 106 and the second electrode 108 of the micro LED chip 10 are electrically connected to the solder columns 302 at the corresponding positions, respectively, and there is a height difference Δ h between the solder columns 302 at the corresponding positions of the first electrode 106 and the second electrode 108.

In one embodiment, as shown in fig. 6, fig. 6 is a schematic structural diagram of another embodiment of a display panel according to the present application. When the second electrode 108a protrudes from the first electrode 106a and the cross section of the second electrode 108a is an inverted trapezoid in the direction from the first doped epitaxial layer 100a to the second electrode 108a, and/or the cross section of the first electrode 106a is an inverted trapezoid, as shown in fig. 6, when the cross sections of the first electrode 106a and the second electrode 108a are inverted trapezoids, the solder pillar 302a corresponding to the electrode with the inverted trapezoid cross section is provided with a recess (not shown) matching with the inverted trapezoid, and the solder pillar 302a can cover all or part of the electrode with the inverted trapezoid cross section, thereby reducing the probability of disconnection between the electrode and the corresponding solder pillar 302 a. As shown in fig. 3, when the first electrode 106b protrudes from the second electrode 108b, and the cross section of the portion of the first electrode 106b protruding from the second electrode 108b is an inverted trapezoid, the solder pillar corresponding to the first electrode 106b may also adopt the above design, which is not described herein again.

Referring to fig. 7 to 8, fig. 7 is a schematic flowchart illustrating an embodiment of a method for transferring a micro LED chip according to the present application, and fig. 8 is a schematic structural diagram illustrating an embodiment corresponding to steps S101 to S105 in fig. 7, where the method includes:

s101: a growth substrate 20 is provided.

Specifically, as shown in fig. 8a, the structure of the growth substrate 20 can refer to any of the above embodiments, and is not described herein again.

In an application scenario, when the structure of the micro LED chip 10 is as shown in fig. 8a, the step S101 includes: forming a first doped epitaxial layer 100, a light emitting layer 102 and a second doped epitaxial layer 104 in sequence on one side of a transparent substrate 200, wherein the light emitting layer 102 and the second doped epitaxial layer 104 only cover a first region of the first doped epitaxial layer 100; a first electrode 106 and a second electrode 108 are simultaneously and respectively formed in a second region of the first doped epitaxial layer 100 and a side of the second doped epitaxial layer 104 away from the light emitting layer 102, the thicknesses of the first electrode 106 and the second electrode 108 are the same, and the second electrode 108 protrudes from the first electrode 106 in the formed micro LED chip 10. When the structure of the micro LED chip 10b is as shown in fig. 3, i.e., the first electrode 106b protrudes from the second electrode 108b, the first electrode 106b and the second electrode 108b need to be formed by step processing.

Further, after the first electrode 106 and the second electrode 108 are formed, the transfer method provided by the present application further includes: etching the first electrode 106 and the second electrode 108 so that the cross section of the first electrode 106 is in an inverted trapezoid shape along the first doped epitaxial layer 100 to the second electrode 108; and/or, the second electrode 108 is etched, so that the cross section of the second electrode 108 is in an inverted trapezoid shape along the first doped epitaxial layer 100 to the second electrode 108. The specific etching process can be that firstly, photoresist is used for protecting other parts except the electrode to be etched, then the whole body is gradually put into the solution for etching, and the longer the part which is firstly put into the solution is, the more the part is etched, so that the inverted trapezoid is formed.

S102: the side of the growth substrate 20 provided with the plurality of micro LED chips 10 is embedded in the bonding layer 40 of the temporary substrate 42, a protruding portion of one (e.g., the second electrode 108 in fig. 8 b) of the first and second electrodes 106 and 108 of the micro LED chips 10 located on the same side is located in the bonding layer 40, and at least a portion of the other (e.g., the first electrode 106 in fig. 8 b) is located outside the bonding layer 40.

Specifically, as shown in fig. 8b, the bonding layer 40 may be made of polyacrylate, siloxane, or the like, and the bonding layer 40 may be attached to the temporary substrate 42.

In an application scenario, as shown in fig. 8b, the implementation process of step S102 may include: the growth substrate 20 is brought close to the bonding layer 40 until the surface of the bonding layer 40 close to the side of the growth substrate 20 is flush with the surface of the other electrode (for example, the first electrode 106 in fig. 8 b) facing away from the transparent substrate 200, and at this time, the other electrode (for example, the first electrode 106 in fig. 8 b) is located outside the bonding layer 40 except for the surface of the side in contact with the bonding layer 40. The design mode can reduce the pressure required for pressing the growth substrate 20 and reduce the probability that the growth substrate 20 is crushed on the premise of ensuring that the micro LED chip 10 in the growth substrate 20 is fixed by the bonding layer 40.

S103: the laser light is irradiated from the transparent substrate 200 side of the growth substrate 20 to separate the transparent substrate 200 from the first doped epitaxial layer 100.

Specifically, as shown in fig. 8c, the laser light may be emitted by a laser, for example, a solid-state laser, an excimer laser, or the like. The first doped epitaxial layer 100 is decomposed by the laser light to be separated from the transparent substrate 200.

S104: the transparent substrate 200 is removed.

In particular, as shown in fig. 8 d.

S105: the micro LED chip 10 is transferred.

Specifically, as shown in fig. 8e, the micro LED chip 10 is transferred by a pick-up transfer head 44, and the pick-up transfer head 44 may be an electrostatic transfer head, a vacuum transfer head, a magnetic transfer head, an adhesive transfer head, or the like. Since the upper portion of the micro LED chip 10 is exposed from the bonding layer 40, the above pick-up transfer head 44 easily picks up the micro LED chip 10.

In addition, in the present embodiment, in order to further reduce the resistance of the pick-up transfer head 44 to transfer the micro LED chip 10 from the bonding layer 40, before the step S104, the transfer method provided by the present application further includes: the heating reduces the tack of the bonding layer 40. The temporary substrate 42 in contact with the bonding layer 40 is, for example, an electrical heating plate, and the purpose of heating the bonding layer 40 is achieved by heating the temporary substrate 42.

The above description is only for the purpose of illustrating embodiments of the present application and is not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made by the contents of the specification and the drawings of the present application or are directly or indirectly applied to other related technical fields, are also included in the scope of the present application.