Micro-LED mass transfer and bonding method

Abstract

The invention relates to a micro light-emitting diode (Micro LED), in particular to a Micro-LED mass transfer and bonding method, and discloses a Micro-LED mass transfer method, which comprises the following steps of: S1, preparing a Micro-LED chip array on a substrate; s2, a first temporary substrate is attached to the top of the Micro-LED chip array, the Micro-LED chip array is turned over for the first time, the substrate faces upwards, and the first temporary substrate faces downwards; s3, stripping the substrate; s4, a second temporary substrate with higher viscidity is used to be attached to the bottom of the Micro-LED chip array; s5, the Micro-LED chip array is turned over for the second time, so that the first temporary substrate faces upwards, and the second temporary substrate faces downwards; and S6, stripping the first temporary substrate, completing the secondary transfer process of the Micro-LED chip array, and exposing the top electrode structure of the Micro-LED chip array.

Description

Technical Field

[0001] The present invention relates to a micro light emitting diode Micro LED, and in particular to a Micro-LED mass transfer and bonding method. Background Art

[0002] As the preparation process matures, the size of LEDs is gradually reduced, and the application direction is moving from being used as a backlight source for LCDs to being used as a display application field for light-emitting pixel units. Mass transfer technology plays an important role in the display application of Micro-LEDs. Mass transfer technology refers to the process of releasing the Micro-LED array from the growth substrate and transferring it to the target substrate for placement. At present, high cost and low yield are the main bottlenecks restricting the realization of full-color Micro-LED display screens with mass transfer technology. Although a variety of transfer technologies have been reported, only a few have been successfully applied to Micro-LEDs. First, most of the literature uses simple structures such as small silicon wafers to replace actual LED devices for transfer experiments. In fact, Micro-LEDs have complex surface structures due to processes such as table etching and electrode evaporation, and are not as flat as silicon wafers. Secondly, due to the higher difficulty of transferring small-size and high-density Micro-LED arrays, the size of the transferred LED devices in the currently published literature is mostly greater than 50μm, and the pixel pitch is large, so the scope of application is limited.

[0003] Research results and developments in recent years have shown that transfer printing is a promising technology for realizing full-color Micro-LED displays. In particular, on this basis, large display panels can be produced by using multiple transfer and re-splicing methods. At the same time, full-color Micro-LEDs can be used on both rigid substrates and flexible substrates, which provides a basis for future flexible display applications. From the research progress of transfer printing technology, it is not difficult to find that its essence is to achieve the device transfer process by regulating the different adhesion forces between Micro-LED devices and various interfaces. The micro-transfer printing technology based on elastomeric stamps can support the transfer of single or array-based Micro-LEDs to different types of substrates, and can provide the ability to rearrange the number of pixels, pixel spacing and final display size. The currently proposed elastomeric stamp micro-transfer printing technology is mostly to make a sacrificial layer, use a stamp to press the anchor point to separate the LED from the growth substrate, and transfer the Micro-LED to the target substrate for wiring bonding through a single transfer, such as Figure 1 However, the method of picking up the device by breaking the anchor point can easily cause the LED to shift, and the wiring of the horizontal structure Micro-LED will result in limited resolution.

[0004] Therefore, those skilled in the art are committed to developing a Micro-LED mass transfer and bonding method. Summary of the invention

[0005] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a Micro-LED mass transfer method, comprising the following steps:

[0006] S1. Preparing a Micro-LED chip array on a substrate;

[0007] S2, attaching the first temporary substrate on the top of the Micro-LED chip array, and flipping the Micro-LED chip array for the first time, so that the substrate faces upward and the first temporary substrate faces downward;

[0008] S3, peeling off the substrate;

[0009] S4, using a second temporary substrate with stronger adhesion to adhere to the bottom of the Micro-LED chip array;

[0010] S5, flipping the Micro-LED chip array for the second time, so that the first temporary substrate faces upward and the second temporary substrate faces downward;

[0011] S6. Peeling off the first temporary substrate, completing the secondary transfer process of the Micro-LED chip array, and exposing the top electrode structure of the Micro-LED chip array.

[0012] Furthermore, in S1, the Micro-LED chip is formed by etching definition, and an N-GaN layer, an MQWs layer, a P-GaN layer, a CSL layer and a P-pad layer are sequentially grown on the substrate.

[0013] Further, in S1, the substrate is a sapphire substrate.

[0014] Furthermore, the Micro-LED chip array is designed to be connected in parallel or in series.

[0015] Furthermore, in S3, the substrate is lifted off by laser.

[0016] Further, in S4, the second temporary substrate is a thermal release film.

[0017] A Micro-LED mass transfer and bonding method, comprising any of the above Micro-LED mass transfer methods, further comprising the following steps:

[0018] S7, flipping the Micro-LED chip array for the third time, aligning the top of the Micro-LED chip array on the second temporary substrate with the driving circuit, and completing bonding under heating and pressure conditions;

[0019] S8, peeling off and removing the second temporary substrate.

[0020] The beneficial effects of the present invention are as follows: the present invention combines laser peeling and thin film transfer technology, realizes large-area peeling of the Micro-LED array through laser peeling technology, and then utilizes the difference in viscosity of the film to transfer the Micro-LED array to the flexible film through two flips to complete a high-speed, high-yield mass transfer process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of a transfer process of a specific implementation mode of the present invention.

[0022] Figure 2 It is a schematic diagram of a bonding process of a specific embodiment of the present invention.

[0023] 1. Substrate; 2. Micro-LED chip; 3. First temporary substrate; 4. Second temporary substrate;

[0024] 5. Driving circuit. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that in the description of the present invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific manner, and therefore cannot be understood as limiting the present invention. The terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0026] like Figure 1-2 As shown, a Micro-LED mass transfer method includes the following steps:

[0027] S1, preparing a Micro-LED chip 2 array on a substrate 1;

[0028] S2, peeling off the substrate 1, such as Figure 1 As shown in (a) and (b), the top of the Micro-LED chip 2 grown on the substrate 1 is first attached to the first temporary substrate 3, and then the Micro-LED chip 2 array is flipped for the first time, so that the substrate 1 faces upward and the first temporary substrate 3 faces downward;

[0029] S3, applying laser to one side of the substrate 1 to release the Micro-LED chip 2 from the substrate 1 to the first temporary substrate 3 (blue film);

[0030] S4, film secondary transfer, such as Figure 1As shown in (c) and (d), a second temporary substrate 4 with stronger adhesion is attached to the bottom of the Micro-LED chip 2 array;

[0031] S5, flipping the Micro-LED chip 2 array for the second time, so that the first temporary substrate 3 faces upward and the second temporary substrate 4 faces downward;

[0032] S6. Peeling off the first temporary substrate 3, completing the secondary transfer process of the Micro-LED chip 2 array, exposing the top electrode structure of the Micro-LED chip 2 array, and facilitating subsequent process operations.

[0033] The present invention combines laser peeling and thin film transfer technology, and realizes large-area peeling of the Micro-LED array through laser peeling technology. Then, the Micro-LED array is peeled off and transferred from the substrate 1 by multiple flippings using the viscosity difference of the thin film. The single transfer array area is 6.5×8mm2, the number of transferred devices reaches more than 20,000, and the transfer yield reaches 99.35%, which better meets the needs of mass transfer. At the same time, the process of transferring the Micro-LED array to the film through mass transfer also proves the potential of Micro-LED in flexible display.

[0034] In this embodiment: in S1, the Micro-LED chip 2 is formed by etching definition, and an N-GaN layer, an MQWs layer, a P-GaN layer, a CSL layer and a P-pad layer are sequentially grown on the substrate 1. In S1, the substrate 1 is a sapphire substrate 1, and the Micro-LED chip 2 array is designed to be connected in parallel or in series. In S4, the second temporary substrate 4 is a thermal release film.

[0035] The sapphire substrate 1 has good chemical stability and is not easily decomposed and corroded in the temperature and atmosphere of epitaxial growth. The Micro-LED chip 2 array is designed in parallel or series to facilitate production and installation. In step S3, laser stripping of the substrate 1 can shorten the stripping time and improve efficiency. In step S4, the second temporary substrate 4 is a thermal release mold. The thermal release mold can quickly respond and absorb heat, thereby improving production efficiency.

[0036] A Micro-LED mass transfer and bonding method includes the Micro-LED mass transfer method as described above, and further includes the following steps:

[0037] S7, such as Figure 2 As shown in (e) and (f), the Micro-LED chip 2 array is flipped for the third time, and the top of the Micro-LED chip 2 array on the second temporary substrate 4 is aligned with the driving circuit 5, and bonding is completed under heating and pressure conditions;

[0038] S8, such as Figure 2 As shown in (g), the second temporary substrate 4 is peeled off and removed.

[0039] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A Micro-LED mass transfer method, characterized by: The following steps are involved: S1. Preparing a Micro-LED chip (2) array on a substrate (1); S2, attaching the first temporary substrate (3) on the top of the Micro-LED chip (2) array, and flipping the Micro-LED chip (2) array for the first time, so that the substrate (1) faces upward and the first temporary substrate (3) faces downward; S3, peeling off the substrate (1); S4, using a second temporary substrate (4) with stronger adhesion to adhere to the bottom of the Micro-LED chip (2) array; S5, turning over the Micro-LED chip (2) array for a second time, so that the first temporary substrate (3) faces upward and the second temporary substrate (4) faces downward; S6, peeling off the first temporary substrate (3), completing the process of secondary transfer of the Micro-LED chip (2) array, and exposing the top electrode structure of the Micro-LED chip (2) array.

2. The Micro-LED mass transfer method according to claim 1, wherein: In S1, the Micro-LED chip is formed by etching definition, and the N-GaN layer, MQWs layer, P-GaN layer, CSL layer and P-pad layer are grown on the substrate in sequence.

3. The Micro-LED mass transfer method according to claim 1, wherein: In S1, the substrate is a sapphire substrate.

4. The Micro-LED mass transfer method according to claim 1, wherein: The Micro-LED chip (2) array is designed to be connected in parallel or in series.

5. The Micro-LED mass transfer method according to claim 1, wherein: In S3, the substrate (1) is lifted off by laser.

6. The Micro-LED mass transfer method according to claim 5, wherein: In S4, the second temporary substrate (4) is a thermal release film.

7. A Micro-LED bonding method, characterized in that: Including the Micro-LED mass transfer method as described in any one of claims 1-6.

8. The Micro-LED bonding method according to claim 7, wherein: The following steps are also included: S7, flipping the Micro-LED chip (2) array for the third time, aligning the top of the Micro-LED chip (2) array on the second temporary substrate (4) with the driving circuit (5), and completing bonding under heating and pressure conditions; S8, peeling off and removing the second temporary substrate (4).

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