WO2020258644A1

WO2020258644A1 - Microled chip transferring method

Info

Publication number: WO2020258644A1
Application number: PCT/CN2019/115953
Authority: WO
Inventors: 樊勇
Original assignee: 深圳市华星光电半导体显示技术有限公司
Priority date: 2019-06-24
Filing date: 2019-11-06
Publication date: 2020-12-30
Also published as: CN110335845B; CN110335845A

Abstract

A microLED chip transferring method, comprising: adhering an ACF adhesive to a wafer of microLEDs in advance, and then transferring a microLED chip to a TFT substrate, such that electrode of the microLED is aligned with the electrode of the TFT; the electrode of the microLED is electrically connected to the electrode of the TFT by heating and pressing a pressure head. The method of the present application can save the usage amount of the ACF adhesive, and also avoid the contamination of the pressure head due to unevenness of the TFT.

Description

A transfer method of MicroLED chips

Technical field

This application relates to the field of display technology, and in particular to a method for transferring MicroLED chips.

Background technique

In the prior art, in order to transfer the MicroLED to the TFT substrate to achieve a reliable electrical connection.

As shown in Figure 1, before transferring the MicroLED 6', the entire surface of the ACF glue 3'is attached to the TFT substrate 4'. After the MicroLED 6'is transferred, the MicroLED 6'is bonded to the TFT by pressure and heating. On the substrate 4', the electrode 2'of the MicroLED and the electrode 5'of the TFT are aligned.

However, the bonding area of the MicroLED 6'and the TFT substrate 4'only occupies a small part of the pixel display area, and this method requires the ACF glue 3'containing conductive particles 31' to be spread on the entire surface of the TFT substrate 4'. Therefore, this method obviously wastes a lot of materials.

At the same time, the unevenness of the TFT substrate 4'may also cause contamination of the indenter.

In order to solve the problem of waste and pollution caused by the large amount of ACF glue in the above-mentioned MicroLED transfer process, a method for mass transfer of electronic components as disclosed in the publication number CN107768487A is further proposed in the art. This method first provides wafers and electronic components arranged in a matrix on the surface of the substrate. Next, the wafer is attached to the temporary fixing layer. Subsequently, the wafer is diced so that the wafer is formed into multiple plates. Each board includes at least some electronic components and sub-substrates. The temporary fixing layer is expanded so that the plates on the temporary fixing layer separate from each other as the temporary fixing layer expands. Then, at least a part of these plates is selected as a predetermined bonding portion, and each of the predetermined bonding portions is transferred to the carrier substrate in stages, so that the electronic components in the predetermined bonding portion are bonded to the carrier substrate. Finally, remove the sub-substrates of these plates.

technical problem

However, this modification method still has problems such as complicated steps and uneven TFT.

Therefore, it is necessary to provide a new method for transferring MicroLED chips to overcome the above-mentioned drawbacks.

Technical solutions

The purpose of this application is to provide a MicroLED transfer method with pre-glued ACF. It can not only save the amount of ACF glue used, but also avoid the pollution of the indenter caused by uneven TFT.

In order to achieve the above objective, according to one aspect of the present application, a method for transferring MicroLED chips is provided, which includes the following steps:

S1: Fabricate a MicroLEDs wafer, the wafer includes a substrate and MicroLED chips arranged on the surface of the substrate, and a metal electrode is formed on the MicroLED chip, and ACF glue is glued on the electrode side of the MicroLED chip; wherein, the wafer The substrate is a sapphire substrate, a gallium nitride substrate, an aluminum nitride substrate, a silicon substrate, a gallium arsenide substrate, or a silicon carbide substrate;

S2: Bond the MicroLEDs wafer to the temporary substrate through the ACF glue side;

S3: peeling off the MicroLEDs wafer substrate and cutting the MicroLEDs wafer into MicroLED chips; wherein, by irradiating the laser on the side of the wafer substrate, the wafer substrate is peeled off; and,

S4: Dissolve the MicroLED chip from the temporary substrate, transfer the MicroLED chip to the TFT substrate, and align the electrodes of the MicroLED with the electrodes of the TFT; and then heat and pressure the pressure head to make the electrodes of the MicroLED and the TFT Sexual connection; wherein, the MicroLED chip and the temporary substrate are debonded by ultraviolet light irradiation.

In one embodiment, in step S3, a 266 nm laser is irradiated on the wafer substrate to peel off the wafer substrate.

In one embodiment, in step S1, the wafer fabrication of MicroLEDs follows the following steps: First, various crystal layers of MicroLED are prepared on the wafer substrate by metal organic chemical vapor deposition equipment, including: GaN buffer layer/n Type GaN, multi-quantum well layer light-emitting layer/P-type GaN; then form an ITO current spreading layer and a metal electrode layer on the wafer, and fabricate electrodes through an inductively coupled plasma etching process to obtain MicroLEDs wafers with electrodes.

According to another aspect of the present application, a method for transferring MicroLED chips is provided. ACF glue containing conductive particles is pre-attached to the MicroLED wafer, and then the MicroLED chip is transferred to the TFT substrate to make the electrodes of the MicroLED and the TFT The electrodes are aligned, and then the electrodes of the MicroLED and the electrodes of the TFT are electrically connected by heating and pressing the indenter.

In the transfer method of the present application, the ACF glue is only located on the lower surface of the MicroLEDs wafer, which can avoid the phenomenon of non-LED bonding due to uneven TFT substrates, thereby contaminating the indenter.

In an embodiment, the transfer method includes the following specific steps:

S1: Fabrication of MicroLEDs wafers. One of the wafers includes a substrate and MicroLED chips arranged on the surface of the substrate. The MicroLED chips form metal electrodes, and ACF glue is glued on the electrode side of the MicroLED chips;

S2: Adhere the MicroLEDs wafer to the temporary substrate through the ACF glue side;

S3: Peel off the MicroLEDs wafer substrate and cut the MicroLEDs wafer into MicroLED chips; and,

S4: Dissolve the MicroLED chip from the temporary substrate, and transfer the MicroLED chip to the TFT substrate.

In one embodiment, the anisotropic conductive film is formed on the wafer (chip) first, and then dicing is performed to obtain the MicroLED chip structure with the ACF film, and the subsequent transfer step is performed.

In one embodiment, in the above step of fabricating the MicroLEDs wafer, the wafer substrate is a sapphire substrate.

In one embodiment, in the above step of fabricating the MicroLEDs wafer, the wafer substrate is a gallium nitride substrate.

In one embodiment, in the above step of fabricating the MicroLEDs wafer, the wafer substrate is an aluminum nitride substrate.

In one embodiment, in the above step of fabricating the MicroLEDs wafer, the wafer substrate is a silicon substrate.

In one embodiment, in the above step of fabricating the MicroLEDs wafer, the wafer substrate is a gallium arsenide substrate.

In this embodiment, in the step of fabricating a wafer of MicroLEDs, the wafer substrate is a silicon carbide substrate.

In one embodiment, the stripping of the wafer substrate of MicroLEDs is achieved by irradiating a laser on the side of the wafer substrate to achieve the stripping of the wafer substrate.

In one embodiment, in the above-mentioned step of debonding the MicroLED chip and the temporary substrate, the temporary substrate is debonded by ultraviolet light irradiation.

In one embodiment, in the above-mentioned step of debonding the MicroLED chip and the temporary substrate, the wafer is 2 inches or 4 inches.

Beneficial effect

In the MicroLED transfer method of the present invention, by gluing the ACF glue on the electrode side of the MicroLED chip before bonding the MicroLEDs wafer and the temporary substrate, the amount of ACF glue used can be greatly saved, and the utilization rate of ACF materials can be improved. Avoid waste of materials. In addition, since the ACF is only located on the lower surface of the MicroLED, it is possible to avoid contamination of the indenter due to uneven terrain of the TFT.

Description of the drawings

FIG. 1 is a schematic diagram of the structure of the MicroLED transferred to the TFT substrate in the prior art;

FIG. 2 is a schematic flowchart of a MicroLED transfer method according to an embodiment of the present invention;

3A to 3E are schematic diagrams of corresponding structures in the step flow of the MicroLED transfer method shown in FIG. 2.

Embodiments of the invention

Hereinafter, the technology of the present application will be described in detail in combination with specific implementations. It should be understood that the following specific implementations are only used to help those skilled in the art understand the application, but not to limit the application.

The description of the following embodiments refers to the attached drawings to illustrate specific embodiments that can be implemented in this application. The directional terms mentioned in this application, such as "up", "down", "front", "rear", "left", "right", "top", "bottom", etc., are only for reference to additional drawings direction. Therefore, the directional terms used are used to illustrate and understand the application, rather than to limit the application.

FIG. 2 is a schematic flow diagram of the MicroLED transfer method described in this application; FIGS. 3A to 3E are structural schematic diagrams corresponding to the step flow of the MicroLED transfer method shown in FIG. 2.

As shown in FIG. 2, in this embodiment, a method for transferring MicroLEDs is provided, including: Step S1: a step of fabricating a MicroLEDs wafer: step S2: a step of bonding the MicroLEDs wafer 1 to a temporary substrate: step S3 : The step of peeling off the wafer substrate of the MicroLEDs; and, step S4: the step of obtaining the MicroLED chip.

In the step S1, as shown in FIG. 3A, a MicroLEDs wafer 1 is first fabricated on a substrate S, and electrodes 2 for forming MicroLED chips are provided on the MicroLEDs wafer 1. Subsequently, the ACF glue 3 is glued on the electrode 2.

In this embodiment, the MicroLEDs wafer 1 is 2 inches or 4 inches, but the invention is not limited to the size of the wafer 1. The substrate S of the MicroLEDs wafer 1 may be, for example, a sapphire substrate (Sapphire Substrate), a gallium nitride substrate (Gallium Nitride Substrate), aluminum nitride substrate (Aluminum Nitride Substrate), silicon substrate (Silicon Substrate), gallium arsenide substrate (Gallium Arsenide Substrate) or silicon carbide substrate (Silicon Carbide Substrate) and so on. In this embodiment, a sapphire substrate is used.

The manufacturing process of the MicroLEDs wafer 1 includes: first, various crystal layers of MicroLEDs, such as GaN, are prepared on a sapphire (Al2O3) substrate by metal organic chemical vapor deposition equipment. Buffer layer/n-type GaN, multi-quantum well layer (MQW) light-emitting layer/P-type GaN; then an ITO current spreading layer and a metal electrode layer are formed on the wafer, and electrodes are made by ICP (inductively coupled plasma etching) process. Finally, as shown in FIG. 3A, a MicroLEDs wafer 1 with electrodes 2 is obtained, and after the fabrication of the MicroLEDs wafer 1 with electrodes is completed, the ACF glue 3 is glued on the electrode 2 side.

In the step S2, as shown in FIG. 2 and FIG. 3B, the MicroLEDs wafer 1 is bonded to the temporary substrate 7 through the ACF glue 3 side.

In the step S3. As shown in Figure 2 and Figure 3C, using laser lift-off technology (Laser Lift-Off), the substrate S is irradiated with a 266nm laser to vaporize the GaN at the interface between the substrate S and GaN, thereby peeling off the substrate S . At this time, as shown in FIG. 3C, only the MicroLEDs wafer 1 with electrodes 2 is adhered to the temporary substrate 7 by the ACF glue 3, and the substrate S is not.

Next, in the step S3, as shown in FIG. 2 and FIG. 3D, the MicroLEDs wafer 1 is cut into a plurality of MicroLED chips 6 by cutting. At this time, all the MicroLED chips 6 are bonded to the temporary substrate 7 through the ACF glue 3. And, as shown in FIG. 3D, the ACF glue 3 is also cut together.

In the step S4, prior to the transfer, the MicroLED chip and the temporary substrate are irradiated by ultraviolet light to de-glue, and then the MicroLED chip 6 can be removed from the temporary substrate 7 by the transfer head of the transfer device. Take and place on a TFT substrate 4. Thus, as shown in FIG. 3E, the electrode 2 of the MicroLED chip 6 is aligned with the electrode 5 of a TFT substrate 4 using the ACF glue 3, and then the electrodes 2 of the MicroLED chip 6 are aligned with the electrode 5 of a TFT substrate 4 by heating and pressing the indenter. The electrodes 5 on the TFT substrate 4 are electrically connected.

Those skilled in the art can understand that the term MicroLED in this article refers to LEDs with a size less than 100um, also known as uLED; the term ACF refers to anisotropic conductive film, which is Anisotropic Abbreviation for Conductive Film.

This application has been described by the above-mentioned related embodiments, but the above-mentioned embodiments are only examples for implementing this application. It must be pointed out that the disclosed embodiments do not limit the scope of the application. On the contrary, modifications and equivalent arrangements included in the spirit and scope of the claims are all included in the scope of the present application.

Industrial applicability

The subject of this application can be manufactured and used in industry and has industrial applicability.

Claims

A method for transferring MicroLED chips includes the following steps:

S1: Fabricate a MicroLEDs wafer, the wafer includes a substrate and MicroLED chips arranged on the surface of the substrate, and a metal electrode is formed on the MicroLED chip, and ACF glue is glued on the electrode side of the MicroLED chip; wherein, the wafer The substrate is a sapphire substrate, a gallium nitride substrate, an aluminum nitride substrate, a silicon substrate, a gallium arsenide substrate, or a silicon carbide substrate;

S2: Bond the MicroLEDs wafer to the temporary substrate through the ACF glue side;

S3: peeling off the MicroLEDs wafer substrate and cutting the MicroLEDs wafer into MicroLED chips; wherein, by irradiating the laser on the side of the wafer substrate, the wafer substrate is peeled off; and,

S4: Dissolve the MicroLED chip from the temporary substrate, transfer the MicroLED chip to the TFT substrate, and align the electrodes of the MicroLED with the electrodes of the TFT; and then heat and pressure the pressure head to make the electrodes of the MicroLED and the TFT Sexual connection; wherein, the MicroLED chip and the temporary substrate are debonded by ultraviolet light irradiation.
The transfer method according to claim 1, wherein in step S3, a 266 nm laser is irradiated on the wafer substrate to peel off the wafer substrate.
The transfer method according to claim 1, wherein, in step S1, MicroLEDs wafer fabrication is as follows: firstly, various crystal layers of MicroLEDs are prepared on the wafer substrate by metal organic chemical vapor deposition equipment, including : GaN buffer layer/n-type GaN, multi-quantum well layer light-emitting layer/P-type GaN; then form an ITO current spreading layer and a metal electrode layer on the wafer, and fabricate electrodes through an inductively coupled plasma etching process to obtain electrodes with electrodes MicroLEDs wafers.
A method for transferring MicroLED chips is to pre-attach the ACF glue to the MicroLEDs wafer, and then transfer the MicroLED chip to the TFT substrate to align the electrodes of the MicroLED and the TFT; and then heat the pressure head And pressure makes the electrode of MicroLED and the electrode of TFT electrical connection.
According to the transfer method of claim 4, the specific steps are as follows:

S1: Fabricating a MicroLEDs wafer, the wafer including a substrate and MicroLED chips arranged on the surface of the substrate, forming a metal electrode on the MicroLED chip, and bonding ACF glue on the electrode side of the MicroLED chip;

S2: Adhere the MicroLEDs wafer to the temporary substrate through the ACF glue side;

S3: Peel off the MicroLEDs wafer substrate and cut the MicroLEDs wafer into MicroLED chips;

S4: Dissolve the MicroLED chip from the temporary substrate, and transfer the MicroLED chip to the TFT substrate.
4. The transfer method according to claim 4, wherein the MicroLED wafer production is as follows: first, various crystal layers of MicroLED are prepared on the wafer substrate by metal organic chemical vapor deposition equipment, including: GaN buffer layer/ n-type GaN, multi-quantum well layer light-emitting layer/P-type GaN; then form an ITO current spreading layer and a metal electrode layer on the wafer, and fabricate electrodes through an inductively coupled plasma etching process to obtain MicroLEDs wafers with electrodes; then , The electrode side of each MicroLED in the MicroLEDs wafer is glued with ACF glue.
The transfer method according to claim 6, wherein the wafer substrate is an Al 2 O 3 substrate.
The transfer method according to claim 6, wherein the wafer substrate is a gallium nitride substrate, an aluminum nitride substrate, or a silicon substrate.
The transfer method according to claim 6, wherein the wafer substrate is a gallium arsenide substrate.
The transfer method according to claim 6, wherein, in the step S1, the wafer substrate is a silicon carbide substrate.
The transfer method according to claim 5, wherein, in the step S3, the stripping of the MicroLEDs wafer substrate is achieved by irradiating a laser on the side of the wafer substrate to achieve the stripping of the wafer substrate.
The transfer method according to claim 5, wherein, in step S4, the temporary substrate is debonded by ultraviolet light irradiation.
The transfer method of claim 4, wherein the wafer is 2 inches or 4 inches.