Magnetic drive dry adhesion seal for Micro-LED chip mass transfer and manufacturing method

Abstract

The invention relates to a micro-LED chip mass transfer-oriented magnetic drive dry adhesion seal and a manufacturing method thereof, the magnetic drive dry adhesion seal comprises a two-layer structure, the surface layer is a dry adhesion structure layer, the bottom layer is a magnetic drive structure layer, the surface of the dry adhesion structure layer is provided with mushroom-shaped tail end structures in array distribution, the magnetic drive structure layer is provided with a plurality of uniformly distributed cavities, and the cavities are communicated with the dry adhesion structure layer. And the cavity is filled with a flow-state magnetic composite material. The manufacturing method comprises the following steps: firstly preparing a flow-state magnetic composite material, then preparing the pre-cured magnetic driving structure layer by using dry etching, mold overturning and molding spin-coating processes, then preparing and processing the bionic dry adhesion mold by using photoetching, mold reversing and hot pressing, and finally assembling the dry adhesion structure layer and the pre-cured magnetic driving structure layer. According to the magnetic drive dry adhesion seal, the gecko bionic dry adhesion effect and the magnetostriction effect are integrated, organic unification of high-strength reliable pickup and zero-adhesion accurate release of Micro-LED chips can be achieved, and the barrier that a conventional standard Dewaals force huge transfer technology needs a complex front / later-stage preparation process is broken through.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano engineering bionic manufacturing technology, and specifically relates to a magnetically driven dry adhesion stamp and a manufacturing method for mass transfer of Micro-LED chips. Background Art

[0002] Mass transfer is the most difficult technical pain point in the mass production of Micro-LED chips and is the frontier of current research. The difficulty lies in how to simultaneously achieve reliable pickup and precise release of millions of Micro-LED chips (less than 100 μm in size). Currently in the industry and academia, van der Waals mass transfer technology has been developed into a relatively mature technology due to its high transfer yield (99.9%) and high compatibility with the current semiconductor industry chain. It generally regulates the interfacial van der Waals force by adjusting the interface separation speed of the transfer stamp (usually polydimethylsiloxane (PDMS)), thereby controlling the pickup and release of Micro-LED chips. It should be pointed out that before using the above-mentioned PDMS stamp to achieve mass transfer, the Micro-LED chip needs to be structurally weakened: Micro-LED chips are usually manufactured on donors or epitaxial substrates, and the two are tightly connected. The low-surface-energy PDMS stamp is difficult to pick up directly by relying on the interfacial van der Waals force. Therefore, it is necessary to introduce a sacrificial layer or buffer layer on the donor or epitaxial substrate in advance, and then use photolithography, etching and other processes to weaken the sacrificial layer or buffer layer, so that the Micro-LED chip is only connected to the donor or epitaxial substrate through a pre-designed anchor point or tether, which greatly increases the complexity of the process. In addition, since the Micro-LED chip is light in weight, it is usually necessary to coat a sticky layer on the driving backplane when releasing it so that the adhesion strength between it and the Micro-LED chip is higher than the adhesion strength between the PDMS stamp and the Micro-LED chip. However, the sticky layer will hinder heat dissipation, resulting in a decrease in the electrical performance of the Micro-LED chip. Therefore, the development of a simple, efficient and low-cost new van der Waals force mass transfer technology is still a major problem. Summary of the invention

[0003] In order to solve the above-mentioned technical problems of the prior art, the purpose of the present invention is to provide a magnetically driven dry adhesion stamp and a manufacturing method for mass transfer of Micro-LED chips, so as to achieve the organic unity of high-strength and reliable pickup of Micro-LED chips and zero-adhesion precise release, and solve the problem that conventional standard Dehuali mass transfer technology requires complex pre / post preparation processes.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is: A magnetically driven dry adhesion stamp for mass transfer of Micro-LED chips comprises a two-layer structure, a top layer being a dry adhesion structure layer and a bottom layer being a magnetically driven structure layer; the surface of the dry adhesion structure layer has an array of mushroom-shaped end structures, and the magnetically driven structure layer has a plurality of evenly distributed cavities filled with a fluid magnetic composite material.

[0005] A method for manufacturing a magnetically driven dry adhesion stamp for mass transfer of Micro-LED chips, comprising the following steps: The first step is the preparation of the fluid magnetic composite: the PDMS body and the nano-magnetic particles are mixed in a mass ratio and stirred evenly by a small mechanical stirrer to obtain the fluid magnetic composite; The second step is the preparation of the pre-cured magnetic drive structure layer: the array holes are processed on the surface of the silicon wafer by dry etching process, and the PDMS prepolymer is molded and filled on it. After complete curing and demolding, an inverse PDMS mold is obtained, and the surface of the inverse PDMS mold is passivated; a layer of polymer material is molded and filled on the inverse PDMS mold, followed by pre-curing treatment, and a pre-cured support microstructure is obtained after demolding; finally, the fluidized magnetic composite is molded and filled into the cavity of the pre-cured support microstructure, and the excess fluidized magnetic composite on the surface of the pre-cured support microstructure is removed by spin coating process to obtain a pre-cured magnetic drive structure layer; The third step is the preparation and treatment of the bionic dry adhesion mold: first, a mushroom-shaped terminal structure hole array is made on the photoresist, and the PDMS prepolymer is molded and filled thereon, and after complete curing, the mold is demolded to obtain a PDMS imprint mold with an array mushroom-shaped terminal structure; then the PDMS imprint mold is hot-pressed onto the thermoplastic plastic and kept for 10 minutes, and after cooling to room temperature, the mold is demolded to obtain a bionic dry adhesion mold; The fourth step is the assembly of the dry adhesion structure layer and the pre-cured magnetic drive structure layer: spin-coat a layer of polymer material on the surface of the bionic dry adhesion mold; then attach the pre-cured magnetic drive structure layer to the spin-coated polymer material and heat it at 50°C for 4 hours to achieve complete curing and self-connection of the two. After demolding, a magnetically driven dry adhesion stamp is obtained.

[0006] In the first step, the mixing mass ratio of the PDMS body and the nano-magnetic particles is 1:5-6; the nano-magnetic particles are carbonyl iron particles or neodymium iron boron particles.

[0007] In the second step, the diameter of the array holes matches the size of the Micro-LED chip, that is, the scale of hundreds of microns.

[0008] In the second step, the pre-curing process parameters of the pre-curing supporting microstructure are heating at 50° C. for 20 to 30 minutes.

[0009] In the third step, the diameter of a single mushroom-shaped terminal structure of the PDMS imprinting mold is ten microns in size.

[0010] In the third step, the thermoplastic plastic is selected from polycarbonate plastic, polystyrene plastic or polypropylene plastic.

[0011] The polymers involved in the second step and the fourth step are made of the same material, namely silicone rubber or polyurethane.

[0012] In the fourth step, the thickness of the polymer material filled by spin coating is several microns.

[0013] The beneficial effects of the present invention are: The present invention proposes a magnetically driven dry adhesion stamp and a manufacturing method for Micro-LED chip mass transfer. The magnetically driven dry adhesion stamp integrates the gecko bionic dry adhesion effect and the magnetostrictive effect, and can achieve the organic unity of high-strength adhesion pickup and zero-adhesion precise release of Micro-LED chips, breaking the barrier of conventional standard dehuali mass transfer technology requiring complex pre / post preparation processes; the low-cost, high-efficiency multi-material, multi-structure heterogeneous integration manufacturing process can realize the integrated, controllable and reliable manufacturing of the magnetically driven dry adhesion stamp, significantly improving the fatigue service life, and providing a reference idea for further optimization and updating of Micro-LED chip mass transfer technology in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic structural diagram of the magnetically driven dry adhesion stamp of the present invention.

[0015] Figure 2 Schematic diagram of the magnetically driven dry adhesion stamp of the present invention picking up a Micro-LED chip from a donor or epitaxial substrate with high strength adhesion.

[0016] Figure 3 Schematic diagram of the magnetically driven dry adhesion stamp of the present invention accurately releasing the Micro-LED chip on the driving backplane with zero adhesion.

[0017] Figure 4 It is a schematic diagram of the fluid magnetic composite material obtained after the PDMS body and the nano-magnetic particles are fully mixed in the present invention.

[0018] Figure 5 It is a schematic structural diagram of the inverse PDMS mold of the present invention.

[0019] Figure 6 It is a schematic diagram of the structure of the pre-cured support microstructure of the present invention.

[0020] Figure 7 It is a schematic structural diagram of the pre-cured magnetic drive structure layer of the present invention.

[0021] Figure 8 It is a schematic structural diagram of the PDMS imprinting mold of the present invention.

[0022] Fig. 9 Schematic diagram of the hot pressing process of the present invention.

[0023] Fig.10 It is a schematic structural diagram of the bionic dry adhesion mold of the present invention.

[0024] Fig.11 It is a schematic diagram of spin coating and filling polymer material on the surface of a bionic dry adhesion mold according to the present invention.

[0025] Fig.12 It is a schematic diagram of the assembly of the uncured dry adhesion structure layer and the pre-cured magnetic drive structure layer of the present invention.

[0026] In the figure: 1. Dry adhesion structure layer; 2. Magnetic drive structure layer; 3. Micro-LED chip; 4. Donor or epitaxial substrate; 5. Fluidized magnetic composite; 5-1. PDMS body; 5-2. Nanomagnetic particles; 6. Driving backplane; 7. Inverse PDMS mold; 8. Pre-cured supporting microstructure; 9. PDMS imprinting mold; 10. Thermoplastic plastic; 11. Bionic dry adhesion mold; 12. Uncured dry adhesion structure layer; 13. Mushroom-shaped end structure. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0028] Reference Figure 1 A magnetically driven dry adhesion stamp for mass transfer of Micro-LED chips comprises a two-layer structure, the surface layer is a dry adhesion structure layer 1, and the bottom layer is a magnetically driven structure layer 2; the surface of the dry adhesion structure layer 1 has an array of mushroom-shaped end structures 13, and the magnetically driven structure layer 2 has a plurality of uniformly distributed cavities, and the cavities are filled with a fluid magnetic composite material 5.

[0029] In the specific implementation process, refer to Figure 2 , the dry adhesion structure layer 1 adopts a mushroom-shaped end structure design, which can effectively weaken the stress singularity of the contact edge, and achieve adhesion enhancement by suppressing the initiation of edge cracks, thereby overcoming the close connection between the Micro-LED chip 3 and the donor or epitaxial substrate 4; the fluid magnetic composite material 5 in the cavity of the magnetic drive structure layer 2 will produce a magnetostrictive effect (manifested as the formation and growth of magnetic chains) under the action of the magnetic field, causing the adhesion interface of the dry adhesion structure layer 1 to deform greatly, greatly weakening the contact area and adhesion force between the magnetic drive dry adhesion stamp and the Micro-LED chip 3, and realizing the zero-adhesion precise release of the Micro-LED chip 3 on the driving backplane 6, such as Figure 3 shown.

[0030] A method for manufacturing a magnetically driven dry adhesion stamp for mass transfer of Micro-LED chips, comprising the following steps: The first step is the preparation of fluid magnetic composites: refer to Figure 4 , the PDMS body 5-1 and the nano-magnetic particles 5-2 are mixed in a mass ratio of 1:5-6, and stirred for 10 hours by a small mechanical stirrer to obtain a fluid magnetic composite material 5; Preferably, the nano magnetic particles 5-2 are carbonyl iron particles or neodymium iron boron particles; The second step is to prepare the pre-cured magnetic drive structure layer: use the dry etching process to process the array holes with a diameter of 100 microns on the surface of the silicon wafer, and mold and fill a layer of PDMS prepolymer (PDMS body and curing agent are mixed in a mass ratio of 10:1) with a thickness of millimeters on it. After curing at 80°C for 2 hours, demold and obtain the inverse PDMS mold 7 and perform surface passivation treatment, as shown in FIG. Figure 5 Then, a layer of polymer material with a thickness of millimeters is molded and filled on the inverse PDMS mold 7, and the pre-curing is achieved by heating at 50°C for 20 to 30 minutes. After demolding, a pre-cured support microstructure 8 with a certain viscosity is obtained, as shown. Figure 6 As shown; then the fluid magnetic composite material 5 is molded and filled into the cavity of the pre-cured support microstructure 8, and the excess fluid magnetic composite material 5 on the surface of the pre-cured support microstructure 8 is removed by spin coating process to obtain a pre-cured magnetic drive structure layer, as shown Figure 7 As shown; the parameters of the spin coating process are low speed 1000 rpm rotation for 10 seconds, and high speed 5000 rpm rotation for 50 seconds; Step 3: Preparation and treatment of the bionic dry adhesion mold: The bionic dry adhesion mold 11 is prepared by photolithography and hot pressing. First, a mushroom-shaped terminal structure hole array is made on the photoresist, and a layer of PDMS prepolymer (PDMS body and curing agent are mixed in a mass ratio of 10:1) with a thickness of millimeters is molded and filled thereon. After heating and curing at 80°C for 2 hours, the mold is removed to obtain a PDMS imprint mold 9 with an array of mushroom-shaped terminal structures. Figure 8 shown; reference Fig. 9 Then, the PDMS imprinting mold 9 is hot pressed onto the thermoplastic 10 and kept for 10 minutes, and then demoulded after cooling to room temperature to obtain the bionic dry adhesion mold 11, as shown in FIG. Fig.10 As shown; Preferably, the diameter of a single mushroom-shaped terminal structure of the PDMS imprinting mold 9 is ten micrometers; Preferably, the hot pressing process parameters are a high temperature environment of 240° C. and a pressure environment of 20 MPa; the thermoplastic plastic 10 is selected from polycarbonate plastic, polystyrene plastic or polypropylene plastic; Step 4: Assembling the dry adhesion structure layer and the pre-cured magnetic drive structure layer: Spin coating a layer of polymer material (i.e., the uncured dry adhesion structure layer 12) on the surface of the bionic dry adhesion mold 11, such as Fig.11 As shown; then the pre-cured magnetic drive structure layer is attached to the spin-coated filled polymer material ( Fig.12 ), and placed in a 50°C environment and heated for 4 hours to achieve complete curing and self-connection of the two, and after demoulding, a magnetically driven dry adhesion stamp was obtained; Preferably, the thickness of the polymer material filled by spin coating is several micrometers, so as to ensure that the magnetostrictive effect of the fluid magnetic composite material 5 can cause the adhesion interface of the dry adhesion structure layer 1 to produce a large deformation when the Micro-LED chip 3 is released; Preferably, the polymers involved in the second step and the third step are made of the same material, silicone rubber or polyurethane.

[0031] The magnetically driven dry adhesion stamp of the present invention integrates the gecko bionic dry adhesion effect and the magnetostrictive effect, which can realize the organic unity of high-strength and reliable pickup and zero-adhesion precise release of Micro-LED chips, solving the problem that the conventional standard dehuali mass transfer technology requires complex pre / post preparation processes; the low-cost and high-efficiency multi-material and multi-structure heterogeneous integration manufacturing process can realize the integrated, controllable and reliable manufacturing of the magnetically driven dry adhesion stamp, significantly improving the fatigue service life, and providing a reference idea for the further optimization and updating of the future Micro-LED chip mass transfer technology.

Claims

1. A magnetically driven dry adhesion stamp for mass transfer of Micro-LED chips, characterized by: The invention comprises a two-layer structure, wherein the surface layer is a dry adhesion structure layer (1), and the bottom layer is a magnetic drive structure layer (2); the surface of the dry adhesion structure layer (1) has an array of mushroom-shaped terminal structures (13), and the magnetic drive structure layer (2) has a plurality of uniformly distributed cavities, and the cavities are filled with a fluid magnetic composite material (5).

2. A method for manufacturing a magnetically driven dry adhesive stamp for mass transfer of Micro-LED chips, characterized in that: The following steps are involved: The first step is to prepare a fluid magnetic composite material: the PDMS body (5-1) and the nano magnetic particles (5-2) are mixed according to a mass ratio, and stirred evenly by a small mechanical stirrer to obtain a fluid magnetic composite material (5); The second step is to prepare a pre-cured magnetic drive structure layer: a dry etching process is used to process an array of holes on the surface of a silicon wafer, a PDMS prepolymer is molded and filled thereon, and after complete curing and demolding, an inverse PDMS mold (7) is obtained, and a passivation treatment is performed on the surface of the inverse PDMS mold (7); a layer of polymer material is molded and filled on the inverse PDMS mold (7), and then a pre-curing treatment is performed, and after demolding, a pre-cured support microstructure (8) is obtained; finally, a fluid magnetic composite material (5) is molded and filled into the cavity of the pre-cured support microstructure (8), and a spin coating process is used to remove excess fluid magnetic composite material (5) on the surface of the pre-cured support microstructure (8), thereby obtaining a pre-cured magnetic drive structure layer; The third step is the preparation and treatment of the bionic dry adhesion mold: first, a mushroom-shaped terminal structure hole array is made on the photoresist, and the PDMS prepolymer is molded and filled thereon, and after complete curing, the mold is demolded to obtain a PDMS imprint mold (9) having an array of mushroom-shaped terminal structures; then, the PDMS imprint mold is hot-pressed onto the thermoplastic plastic (10) and maintained for 10 minutes, and after cooling to room temperature, the mold is demolded to obtain a bionic dry adhesion mold (11); The fourth step is to assemble the dry adhesion structure layer and the pre-cured magnetic drive structure layer: a layer of polymer material is spin-coated on the surface of the bionic dry adhesion mold (11); then the pre-cured magnetic drive structure layer is attached to the spin-coated polymer material, and heated at 50°C for 4 hours to achieve complete curing and self-connection of the two, and the magnetic drive dry adhesion stamp is obtained after demoulding.

3. The method for manufacturing a magnetically driven dry adhesive stamp for mass transfer of Micro-LED chips according to claim 2, characterized in that: In the first step, the mixing mass ratio of the PDMS body (5-1) and the nano-magnetic particles (5-2) is 1:5-6, and the nano-magnetic particles (5-2) are carbonyl iron particles or neodymium iron boron particles.

4. The method for manufacturing a magnetically driven dry adhesive stamp for mass transfer of Micro-LED chips according to claim 2, characterized in that: In the second step, the diameter of the array holes matches the size of the Micro-LED chip (3), that is, a scale of hundreds of micrometers.

5. The method for manufacturing a magnetically driven dry adhesive stamp for mass transfer of Micro-LED chips according to claim 2, characterized in that: In the second step, the pre-curing process parameters for pre-curing the supporting microstructure (8) are heating at 50° C. for 20 to 30 minutes.

6. The method for manufacturing a magnetically driven dry adhesion stamp for mass transfer of Micro-LED chips according to claim 2, characterized in that: In the third step, the diameter of a single mushroom-shaped terminal structure of the PDMS imprinting mold (9) is ten micrometers.

7. The method for manufacturing a magnetically driven dry adhesion stamp for mass transfer of Micro-LED chips according to claim 2, characterized in that: In the third step, the thermoplastic plastic (10) is selected from polycarbonate plastic, polystyrene plastic or polypropylene plastic.

8. The method for manufacturing a magnetically driven dry adhesive stamp for mass transfer of Micro-LED chips according to claim 2, characterized in that: The polymers involved in the second step and the fourth step are made of the same material, namely silicone rubber or polyurethane.

9. The method for manufacturing a magnetically driven dry adhesion stamp for mass transfer of Micro-LED chips according to claim 2, characterized in that: In the fourth step, the thickness of the polymer material filled by spin coating is several microns.

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