Chip transfer method

Abstract

This application discloses a chip transfer method, which includes: preprocessing multiple chips to be transferred by performing hydrophilic modification on the functional surfaces and hydrophobic modification on the non-functional surfaces; conveying the preprocessed chips to a transport channel to obtain multiple water-in-oil droplets encapsulating the chips, wherein the chips encapsulated in the water-in-oil droplets are in a horizontal orientation with their functional surfaces facing the water and their non-functional surfaces facing the oil; conveying the water-in-oil droplets encapsulating the chips to a curved flow channel to filter out water-in-oil droplets encapsulating individual chips; transferring the filtered water-in-oil droplets to a target acceptor aperture on a target substrate, and causing the chips falling into the target acceptor aperture to detach from the water-in-oil droplets. This application improves the accuracy and efficiency of transfer by achieving orientation correction of the chips to be transferred during transport and by filtering out water-in-oil droplets encapsulating individual chips through a curved flow channel.

Description

Technical Field

[0001] This application relates to the field of chip transfer technology, and in particular to a chip transfer method. Background Technology

[0002] In existing technologies, fluid self-assembly (FSA) is commonly used to transfer massive numbers of chips. FSA is a micro / nano manufacturing technology that uses fluid as a medium and, through a pre-set physical or chemical driving force, guides the chips to spontaneously and orderly align and fix them to designated positions on a target substrate. However, FSA often suffers from problems such as low transfer efficiency, low yield, and chip damage. Especially when processing high-density arranged microchips, it is difficult to effectively ensure the stable posture of the chips in the transfer medium. This can lead to chips tilting, sticking, or misalignment when falling into the acceptor holes of the substrate, thus affecting the pixel integrity and electrical performance of the final display panel. Summary of the Invention

[0003] The main technical problem addressed by this application is to provide a chip transfer method that solves the problems of low transfer efficiency, difficulty in chip orientation control, and insufficient transfer accuracy in existing chip transfer technologies, thereby improving the yield and efficiency of chip transfer.

[0004] To solve the above-mentioned technical problems, this application adopts a technical solution: providing a chip transfer method, the method comprising: preprocessing multiple chips to be transferred, wherein, during the preprocessing process, the functional surfaces of the chips to be transferred are hydrophilic and the non-functional surfaces of the chips to be transferred are hydrophobic; conveying the preprocessed multiple chips to be transferred to a transport channel to obtain multiple water-in-oil droplets encapsulating the chips to be transferred, wherein the chips to be transferred encapsulated in the water-in-oil droplets are in a horizontal orientation with the functional surfaces facing water and the non-functional surfaces facing oil; conveying the water-in-oil droplets encapsulating the chips to be transferred to a curved flow channel to screen out the water-in-oil droplets encapsulating a single chip to be transferred; transferring the screened water-in-oil droplets to a target acceptor aperture on a target substrate, and causing the chip to be transferred falling into the target acceptor aperture to detach from the water-in-oil droplets.

[0005] The transport channel includes a transport section and a mixing section. The width of the mixing section is smaller than the internal width of the transport section. The transport section contains an aqueous phase channel and an oil phase channel nested around the aqueous phase channel. The mixing section contains a mixing channel that communicates with the aqueous phase channel and the oil phase channel. The step of transporting the pre-treated chips to be transferred into the transport channel to obtain multiple water-in-oil droplets encapsulating the chips to be transferred includes: transporting the pre-treated chips to be transferred into the aqueous phase channel; receiving the multiple water-in-oil droplets encapsulating the chips to be transferred from the end of the mixing channel away from the transport section; wherein, in the mixing channel, the multiple water-in-oil droplets encapsulating the chips to be transferred spontaneously adjust to a horizontal orientation with the functional surface facing the water and the non-functional surface facing the oil due to the minimization of interfacial free energy.

[0006] The oil phase channel on the back of the transport section is doped with a stabilizer, which includes silica nanoparticles and perfluoropolyether ammonium carboxylate. The water-in-oil droplet includes an aqueous inner phase, the stabilizer, and an oil outer phase arranged sequentially on the chip to be transferred.

[0007] The flow rate in the aqueous phase channel ranges from 60 μL / min to 100 μL / min, and the flow rate in the oil phase channel ranges from 150 μL / min to 400 μL / min.

[0008] The curved flow channel includes a curved section and a screening section. The width of the screening section is wider than that of the curved section, and the screening section is provided with at least two spaced-apart flow dividers. The step of conveying the water-in-oil droplets encapsulating the chips to be transferred to the curved flow channel to screen out the water-in-oil droplets encapsulating a single chip to be transferred includes: feeding multiple chips to be transferred into the curved section from one end of the curved section; receiving the water-in-oil droplets encapsulating a single chip to be transferred from the end of the screening section away from the curved section; wherein the multiple water-in-oil droplets entering the curved section are layered, and the multiple water-in-oil droplets entering the screening section are separated by the multiple flow dividers to distinguish the multiple water-in-oil droplets into empty water-in-oil droplets, water-in-oil droplets encapsulating a single chip to be transferred, and water-in-oil droplets encapsulating multiple chips to be transferred.

[0009] The target substrate includes a substrate and a first pixel electrode layer and a second pixel electrode layer sequentially disposed on the substrate. The step of transferring the selected water-in-oil droplets to the target receiver aperture of the target substrate and causing the chip to be transferred falling into the target receiver aperture to detach from the water-in-oil droplets includes: applying a voltage to the second pixel electrode layer to bring the selected water-in-oil droplets encapsulating a single chip to be transferred closer to the target substrate; stopping the application of voltage to the second pixel electrode layer and applying a voltage to the first pixel electrode layer to move the selected water-in-oil droplets encapsulating a single chip to be transferred to the target receiver aperture of the target substrate.

[0010] The first pixel electrode layer includes several first electrode groups, each first electrode group including two first electrodes and a second electrode with opposite polarities. The several first electrodes are arranged in an array to form multiple electrode rows and multiple electrode columns. The first electrodes in the same electrode row are electrically connected, and the second electrodes in the same electrode column are electrically connected.

[0011] The target substrate has a target acceptor hole wall covered with a hydrophobic layer, which allows the water-in-oil droplet enveloping the chip to be transferred to detach from the chip as it falls into the target acceptor hole.

[0012] The method further includes stopping the application of voltage to the first pixel electrode layer before the water-in-oil droplet encapsulating the chip to be transferred detaches from the chip.

[0013] The step of transferring the selected water-in-oil droplets to the target acceptor aperture of the target substrate and detaching the chip to be transferred from the water-in-oil droplets after falling into the target acceptor aperture further includes cleaning the target substrate with supercritical carbon dioxide.

[0014] Beneficial effects: This application effectively solves the problem of chip inversion or side-standing caused by random tumbling during transfer by performing differentiated wettability modification on the functional and non-functional surfaces of the chip to be transferred, and correcting the orientation of the chip to be transferred during transportation, thereby improving the transfer yield; at the same time, by screening out the water-in-oil droplets that encapsulate individual chips to be transferred through the curved flow channel, the accuracy and efficiency of transfer are improved. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 A flowchart of a chip transfer method provided in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of the chip to be transferred according to an embodiment of this application; Figure 3 This is a schematic diagram of the structure of a transportation channel provided in one embodiment of this application; Figure 4 This is a schematic diagram of the structure of a curved flow channel provided in an embodiment of this application; Figure 5 for Figure 4 Enlarged diagram of section V; Figure 6 for Figure 4 Enlarged schematic diagram of section VI; Figure 7 This is a schematic diagram illustrating the chip to be transferred falling onto the target substrate according to an embodiment of this application; Figure 8 This is a schematic diagram illustrating the movement of a chip to be transferred in an oil-in-water droplet in a transport channel, according to an embodiment of this application. Figure 9 A schematic diagram of a package containing a chip to be transferred, provided in an embodiment of this application; Figure 10 A schematic diagram of the chip to be transferred in an inverted state according to an embodiment of this application; Figure 11 A schematic diagram of a chip to be transferred in a side-standing state according to an embodiment of this application; Figure 12 A schematic diagram of a horizontally positioned chip to be transferred according to an embodiment of this application; Figure 13 This is a schematic diagram of the film layers of a target substrate provided in an embodiment of this application; Figure 14 This is a schematic diagram of a second pixel electrode layer provided in an embodiment of this application; Figure 15 for Figure 14 Enlarged schematic diagram of the XV section; Figure 16 This is a schematic diagram of a first pixel electrode layer provided in an embodiment of this application. Detailed Implementation

[0016] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0017] The terms "first," "second," and "third" in this application are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movements between components in a specific orientation (as shown in the figures). If the specific orientation changes, the directional indications also change accordingly. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0018] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0019] Please refer to the following: Figure 1 - Figure 7 ,in, Figure 5 for Figure 4 An enlarged diagram of section V. Figure 6 for Figure 4 An enlarged schematic diagram of part VI shows that this application provides a chip transfer method, the method including: S100: Preprocessing multiple chips 10 to be transferred, wherein, during the preprocessing process, the functional surface 11 of the chip 10 to be transferred is hydrophilic and the non-functional surface 12 of the chip 10 to be transferred is hydrophobic.

[0020] Specifically, the chip to be transferred 10 (see reference) can be modified by chemical modification. Figure 2 To improve the wettability of the surface, the functional surface 11 (i.e., the side containing key structures such as electrodes) of the chip to be transferred is hydrophilically modified to reduce the interfacial tension with the aqueous phase, and the non-functional surface 12 (i.e., the substrate surface) of the chip to be transferred is hydrophobically modified to reduce the interfacial tension with the oil phase.

[0021] Specifically, the functional surface 11 can be modified by oxygen plasma etching combined with hydrophilic groups, so that the surface contact angle of the functional surface 11 is less than 30°, thereby giving the functional surface 11 strong hydrophilicity; the non-functional surface 12 can be modified by octadecyltrichlorosilane (OTS) self-assembled monolayer, so that the surface contact angle of the non-functional surface 12 is greater than 110°, thereby giving the non-functional surface 12 strong hydrophobicity.

[0022] S110: The pre-processed chips 10 to be transferred are transported to the transport channel 20 to obtain multiple water-in-oil droplets encapsulating the chips 10 to be transferred. Among them, the chips 10 to be transferred encapsulated in the water-in-oil droplets are in a horizontal posture with the functional surface 11 facing the water and the non-functional surface 12 facing the oil.

[0023] Specifically, in transport corridor 20 (see reference) Figure 3 In the process, an aqueous solution encapsulates the chip 10 to be transferred, while an oil solution acts as a continuous phase encapsulating the aqueous droplet. Due to the difference between the hydrophilic functional surface 11 and the hydrophobic non-functional surface 12 of the chip 10 to be transferred, according to the principle of minimizing interfacial free energy, the hydrophilic functional surface 11 tends to contact the aqueous core, while the hydrophobic non-functional surface 12 tends to contact the oil phase. This forces the chip 10 to be transferred to spontaneously adjust to a horizontal orientation within the water-in-oil droplet, i.e., a horizontal orientation with the functional surface 11 facing the water and the non-functional surface 12 facing the oil. This effectively reduces the risk of the chip 10 to be transferred randomly tumbling and inverting in the fluid.

[0024] S120: The water-in-oil droplets encapsulating the chip 10 to be transferred are conveyed to the curved flow channel 30 to screen out the water-in-oil droplets encapsulating a single chip 10 to be transferred.

[0025] Specifically, the oil-in-water droplets enter the curved flow channel 30 (refer to...). Figures 4-6 The sorting is achieved by balancing the inertial lift generated by the fluid at the bend with the secondary flow drag force of Dean. Different numbers of chips 10 to be transferred result in different volumes of their corresponding water-in-oil droplets, which in turn affect their force balance position in the fluid. This allows the water-in-oil droplets encasing a single chip to be stably located in the central region of the bend channel 30, thereby achieving the screening of water-in-oil droplets from a single chip 10 to be transferred.

[0026] S130: Transfer the selected water-in-oil droplets to the target acceptor hole 41 of the target substrate 40, and detach the chip 10 to be transferred from the water-in-oil droplets that has fallen into the target acceptor hole 41.

[0027] Specifically, the selected single-chip droplets are transferred to the target substrate 40 (see reference). Figure 7At the target acceptor hole 41, the chip to be transferred 10 can be detached from the water-in-oil droplet and fall into the target acceptor hole 41 for fixation through a specific electric field or interface action. The water-in-oil droplet's encapsulation of the chip to be transferred 10 achieves isolation and protection of the chip to be transferred 10, thereby reducing the risk of mechanical stress damage that is easily caused in traditional mechanical transfer.

[0028] In the aforementioned chip transfer method, by differentiating the wettability of the functional surfaces 11 and non-functional surfaces 12 of the chip 10 to be transferred, the chip 10 to be transferred can spontaneously form a horizontal orientation in the water-in-oil droplet, with the functional surfaces 11 facing the water and the non-functional surfaces 12 facing the oil. This achieves self-alignment of the chip 10 during fluid transport, effectively reducing the risk of inverted or lateral defects caused by random tumbling of the chip 10. Simultaneously, the balancing mechanism of the curved flow channel 30 allows for precise screening of the water-in-oil droplet encapsulating a single chip 10, which is beneficial for improving the yield of subsequent transfers.

[0029] Please see Figure 3 In one embodiment, the transport channel 20 is provided with a transport section 21 and a mixing section 22. The width of the mixing section 22 is smaller than the internal width of the transport section 21. The transport section 21 is provided with a water phase channel 211 and an oil phase channel 212 nested around the water phase channel 211. The mixing section 22 is provided with a mixing channel 221, which is connected to the water phase channel 211 and the oil phase channel 212.

[0030] Specifically, an aqueous fluid containing the chip 10 to be transferred flows in the aqueous phase channel 211, and a continuous oil phase fluid flows in the oil phase channel 212. The mixing section 22 is located downstream of the transport section 21, and its channel width is narrower than that of the transport section 21, meaning the internal width of the mixing section 22 is smaller than that of the transport section 21. A mixing channel 221 is formed inside the mixing section 22, which is connected to both the upstream aqueous phase channel 211 and the oil phase channel 212, allowing the two phase fluids to come into full contact and undergo hydrodynamic interactions.

[0031] By setting a mixing section 22 with a narrower width, the aqueous phase is subjected to more uniform viscous shear stress when passing through, which is conducive to the formation of water-in-oil droplets with uniform size and stable structure, reducing the risk of water-in-oil droplet breakage or fusion, thereby reducing the damage defects of the chip 10 to be transferred during the transmission process.

[0032] Please refer to the following: Figure 1 , Figure 2 , Figure 3 and Figure 8 In one embodiment, step S110 includes: S111: The pre-processed chips 10 to be transferred are transported into the aqueous phase channel 211.

[0033] An aqueous fluid containing the chip to be transferred 10 flows within the aqueous channel 211, and the chip to be transferred 10 is completely enveloped by the aqueous fluid within the aqueous channel 211.

[0034] S112: Receive multiple oil-in-water droplets of the packaged chip 10 from the end of the mixing channel 221 away from the transport section 21.

[0035] The interconnected structure between the mixing section 22 and the transport section 21 allows the two-phase fluids to mix thoroughly in the contraction region. When the aqueous fluid carrying the chip 10 to be transferred enters the contracted mixing section 22, the flow rate increases due to the reduced cross-sectional area of ​​the flow channel. The high-speed flowing oil phase fluid on both sides generates strong viscous shear stress on the aqueous fluid in the center. The aqueous phase is cut into droplets containing the chip 10 to be transferred and is completely enveloped by the oil phase, thus forming a stable water-in-oil liquid.

[0036] In the hybrid channel 221, the multiple oil-in-water droplets encapsulating the chip 10 to be transferred spontaneously adjust to a horizontal orientation with the functional surface 11 facing the water and the non-functional surface 12 facing the oil due to the minimization of interfacial free energy.

[0037] Specifically, within the mixing channel 221, since the water-in-oil droplet is in a relaxed or stable flow state, and the functional surface 11 and non-functional surface 12 of the chip to be transferred 10 undergo bilateral differential wetting modification, the hydrophilic functional surface 11 of the chip to be transferred 10 can reduce the system interface energy when in contact with the aqueous phase, and the hydrophobic non-functional surface 12 can reduce the system interface energy when in contact with the oil phase. Therefore, driven by minimizing the interface free energy, the chip to be transferred 10 can spontaneously rotate and adjust its attitude inside the water-in-oil droplet, eventually stabilizing in a horizontal attitude where the functional surface 11 faces the water and the non-functional surface 12 faces the oil.

[0038] In actual transportation, the chip 10 to be transferred, after wettability modification, is dispersed in an aqueous fluid. The agglomerates are dispersed by low-speed ultrasonication, allowing the aqueous fluid to be prepared to a concentration of 1×10⁻⁶. 6 A suspension of particles / mL. The liquid flow channel is as follows: Figure 3 As shown, the middle section is the water phase channel 211, and the two sides are the oil phase channels 212. A converging circular nozzle is installed at the end of the water phase channel 211 (i.e., it connects to the mixing section 22 at the rear end of the transport section 21).

[0039] When the chip to be transferred 10 enters the circular nozzle at the end along with the aqueous phase fluid, the fluid velocity increases sharply, and the aqueous phase column begins to contract laterally, forming a liquid neck with a gradually decreasing diameter. The individual chip to be transferred 10 enters the liquid neck region along with the aqueous phase fluid, is completely enveloped by the contracting aqueous phase fluid, and contracts radially along with the liquid neck. Simultaneously, the high-speed oil phase fluid on both sides of the aqueous phase fluid applies extremely high viscous shear stress to the aqueous phase at the circular nozzle. The front aqueous phase column closes rapidly under the action of surface tension, thus forming an independent ellipsoidal aqueous phase droplet; the rear aqueous phase column retracts, awaiting the next necking fracture. At the moment the droplet closes, the chip to be transferred 10 is completely enclosed inside the aqueous phase droplet, completely isolated from the external oil phase (i.e., forming an oil-in-water droplet encapsulating the chip to be transferred 10).

[0040] In one embodiment, the diameter of the circular nozzle can be designed to be 80 μm to accommodate a 45 μm chip 10 to be transferred, thereby reducing the occurrence of multiple chips 10 to be transferred within a single water-in-oil droplet. It is understood that the diameter of the circular nozzle can be designed to be other sizes to accommodate chips 10 to be transferred of different sizes, and the specific size is set according to the requirements, and is not limited here.

[0041] In one embodiment, the flow rate in the aqueous phase channel 211 is in the range of 60 μL / min to 100 μL / min. For example, the flow rate of the aqueous phase fluid in the aqueous phase channel 211 is 60 μL / min, 80 μL / min or 100 μL / min, which can be set according to the requirements and is not limited here.

[0042] In one embodiment, the main component of the aqueous fluid in the aqueous channel 211 is a mixture of ethylene glycol and ultrapure water, wherein the volume ratio of ethylene glycol to ultrapure water is preferably 6:4.

[0043] In one embodiment, a conductivity modifier, such as polyethyleneimine, with a molecular weight of 10 kDa and a concentration of 0.005 wt% to 0.1 wt%, may also be added to the aqueous phase channel 211.

[0044] In one embodiment, the flow rate in the oil phase channel 212 is in the range of 150 μL / min to 400 μL / min. For example, the flow rate of the oil phase fluid in the oil phase channel 212 is 150 μL / min, 300 μL / min or 400 μL / min, which can be set according to the requirements and is not limited here.

[0045] In one embodiment, the oil phase fluid in the oil phase channel 212 is a continuous fluorinated oil phase, and the composition of the oil phase fluid is a mixed oil phase of perfluorotributylamine (e.g., FC-40) and perfluoronaphthalene, with the volume ratio of perfluorotributylamine to perfluoronaphthalene preferably being 7:3.

[0046] In one embodiment, the oil phase channel 212 on the back of the transport section 21 is doped with a stabilizer, which includes silica nanoparticles and perfluoropolyether ammonium carboxylate. The water-in-oil droplet includes an aqueous inner phase, a stabilizer, and an oil outer phase sequentially disposed on the chip to be transferred 10.

[0047] Specifically, hydrophobic silica nanoparticles and perfluoropolyether ammonium carboxylate (PFPE-NH4 surfactant) are added to the oil phase channel 212. These nanoparticles and PFPE-NH4 surfactant can be uniformly dispersed in the continuous fluorinated oil phase through ultrasonic vibration, thus forming a stable oil phase fluid. PFPE-NH4 surfactant has an oleophilic end of the fluorinated chain and a hydrophilic end of the ammonium carboxylate. When the aqueous phase is sheared and broken into nascent aqueous droplets, the initial interfacial tension is as high as 50 mN / m. At this time, the hydrophilic end of the PFPE-NH4 surfactant in the oil phase fluid inserts into the water side, while the hydrophobic fluorine chain remains on the oil side, quickly reducing the interfacial tension to below 10 mN / m. This ensures the smooth formation and spheroidization of the water-in-oil droplets, reducing the risk of initial droplet collisions and re-aggregation.

[0048] Furthermore, during the process of the water-in-oil droplets entering the mixing channel 221, the silica nanoparticles gradually approach the oil-water interface through Brownian motion. Since the outer layer is hydrophobically modified at this point, they are spontaneously captured by interfacial energy upon entering the interfacial region and irreversibly adsorbed onto the interface, ultimately forming a dense particle monolayer. The gaps between the particles are filled with small molecules of perfluoropolyether ammonium carboxylate. The stabilizer provides extremely strong resistance to breakage and fusion. When two water-in-oil droplets approach each other within the mixing channel 221, the outermost hard particles of the two droplets collide with each other, thus forming a physical barrier and reducing the risk of fusion caused by direct contact between the internal aqueous phases of the two droplets.

[0049] In one embodiment, the silica nanoparticles have a particle size of 30 nm, and the surface of the silica nanoparticles can be hydrophobically treated with hexamethyldisilazane (HMDS). The concentration of the silica nanoparticles is 2wt%-5wt%, for example, 2wt%, 3.5wt%, or 5wt%, depending on the requirements and is not limited here.

[0050] In one embodiment, the concentration of perfluoropolyether ammonium carboxylate is 0.01wt%-0.05wt%. For example, the concentration of perfluoropolyether ammonium carboxylate is 0.01wt%, 0.03wt%, or 0.05wt%, depending on the requirements, and is not limited here.

[0051] It is understandable that the state of the water-in-oil droplets output from transport channel 20 and entering mixing channel 221 is as follows: Figure 9As shown, the chip 10 to be transferred within the water-in-oil droplet may not be in a regular position with functional surface 11 facing upwards and non-functional surface 12 facing downwards, as depicted in the figure; instead, it may exist in various orientations. According to the principle of minimizing interface free energy, the total interface free energy G of the entire droplet-chip system consists of three parts:

[0052] in, For the tension at the oil-water interface, The area of ​​the oil-water interface; For the water-chip hydrophilic side interfacial tension, This represents the contact area between the water and the chip. The interfacial tension between the oil and the hydrophobic side of the chip. This represents the contact area between the oil and the chip. Table 1 compares the interface free energy G for three typical orientations: Table 1

[0053] As shown in Table 1, the transfer system evolves towards the state of lowest energy. The micron-sized chip to be transferred 10 has sufficient degrees of freedom, and therefore will always maintain a horizontal orientation with the functional surface 11 facing the water and the non-functional surface 12 facing the oil (e.g., Figure 9 As shown). When the chip to be transferred 10 tilts due to fluid disturbance (such as... Figure 10 or Figure 11 As shown), the interface on the tilted side is stretched, and the restoring torque of the interface tension will quickly pull the chip 10 to be transferred back to the horizontal state; the energy of conventional fluid collision and droplet swaying is far from enough to make the chip 10 to be transferred overcome the interface energy barrier and flip over, so the attitude of the chip 10 to be transferred can remain stable throughout the transportation process.

[0054] In this embodiment, a mixing channel 221 is provided, wherein the length of the mixing channel 221 can be set to be long enough to ensure that the water-in-oil droplets have enough time to complete attitude adjustment, such as a residence time of more than 5 seconds or an equivalent flow path length.

[0055] It is understandable that, such as Figure 12 As shown, after the attitude of the chip 10 to be transferred is adjusted, the hydrophobic side of the chip 10 to be transferred is continuously subjected to a thermodynamic driving force away from the aqueous phase, which causes the chip 10 to be transferred as a whole to migrate toward the oil-water interface at the top of the water-in-oil droplet, and finally pass through the interface and be anchored on the interface with the sidewall circumference, reaching the horizontal steady state with the lowest energy.

[0056] Please refer to the following: Figure 1 , Figure 4 , Figure 5 and Figure 6In one embodiment, the curved flow channel 30 includes a curved section 31 and a screening section 32. The width of the screening section 32 is wider than that of the curved section 31, and the screening section 32 is provided with at least two spaced-apart flow dividers 33.

[0057] Specifically, during the formation of water-in-oil droplets, it is inevitable that some droplets will contain no chips or multiple chips. This embodiment includes a curved section 31, with a screening section 32 at its end. At least two flow-dividing blades 33 are used in the screening section 32 to form three branch channels at its outlet. The curved flow channel 30 can accurately separate water-in-oil droplets containing a single chip 10, based on the number of chips 10 to be transferred within the droplet.

[0058] Step S120 includes: S121: Multiple chips 10 to be transferred are fed into the bending section 31 from one end of the bending section 31.

[0059] Specifically, when the water-in-oil droplets flow through the curved section 31, the fluid generates a secondary flow, namely a Dean vortex, due to the centrifugal force. The inertial lift and Dean drag forces experienced by water-in-oil droplets of different volumes are different. That is, the larger water-in-oil droplets that encapsulate multiple chips 10 to be transferred experience greater inertial lift and tend to migrate to the outside of the flow channel; the smaller empty droplets or water-in-oil droplets that encapsulate a single chip 10 to be transferred are more affected by the Dean drag force and tend to migrate to the inside or middle region of the flow channel.

[0060] S122: Receive an oil-in-water droplet containing a single chip 10 to be transferred from the end of the screening section 32 away from the bending section 31.

[0061] Specifically, the widened structure of the screening section 32 allows for spatial separation of water-in-oil droplets at different locations within the screening section 32. The flow divider 33 is positioned at a critical stratification location, guiding the liquid flow at different locations to different outlets. For example, the inner outlet collects empty water-in-oil droplets, the middle outlet collects water-in-oil droplets encapsulating a single chip 10 to be transferred, and the outer outlet collects water-in-oil droplets encapsulating multiple chips 10 to be transferred, significantly improving the transfer yield.

[0062] In this process, multiple water-in-oil droplets entering the bending section 31 are stratified, and multiple water-in-oil droplets entering the screening section 32 are separated by multiple flow dividers 33, so as to distinguish the multiple water-in-oil droplets into empty water-in-oil droplets, water-in-oil droplets that encapsulate a single chip 10 to be transferred, and water-in-oil droplets that encapsulate multiple chips 10 to be transferred.

[0063] When water-in-oil droplets carrying different numbers of chips 10 to be transferred flow through the curved section 31, the empty water-in-oil droplets, being the smallest in size, have the weakest inertial lift and are dragged by the Dean secondary flow to the vicinity of the inner wall of the flow channel; the water-in-oil droplets encasing multiple chips 10, being the largest in size, have the strongest inertial lift and are pushed to the vicinity of the outer wall of the flow channel; while the water-in-oil droplets encasing a single chip 10, being of moderate size, achieve a dynamic balance between inertial lift and Dean drag, stabilizing in the central region of the flow channel. The function of the flow divider 33 in the subsequent screening section 32 is based on the spatial stratification formed by the curved section 31. It guides the three types of water-in-oil droplets to different outlets or receiving areas through physical or hydrodynamic means. For example, when there are two flow dividers 33, the outlet of the screening section 32 is divided into three channels: left, middle, and right, corresponding to the inner, middle, and outer sides, respectively. This allows water-in-oil droplets encapsulating a single chip 10 to be transferred to be collected separately, reducing the mixing of water-in-oil droplets encapsulating multiple chips 10 to be transferred or empty water-in-oil droplets into the subsequent transfer process, which is beneficial to improving the transfer yield.

[0064] In one embodiment, the flow divider 33 can be a solid baffle perpendicular to the fluid flow direction, or a velocity gradient isolation zone in the sense of fluid dynamics. The specific configuration depends on the requirements and is not limited here.

[0065] In one embodiment, the length of the screening section 32 is 2mm-3mm, and the width of the flow channel of the screening section 32 gradually increases to 1.5 to 2 times the width of the curved section 31, thereby reducing the flow velocity of the water-in-oil droplets.

[0066] In one embodiment, the cross-section of the curved flow channel 30 may be rectangular, the size of the curved flow channel 30 may be designed to be 300µm×250µm, and the diameter of the curved flow channel 30 may be set to 1.2mm.

[0067] Please refer to the following: Figure 1 , Figure 7 and Figure 13 In one embodiment, the target substrate 40 includes a substrate 42 and a first pixel electrode layer 43 and a second pixel electrode layer 44 sequentially disposed on the substrate 42. Step S130 includes: S131: Apply voltage to the second pixel electrode layer 44 to bring the selected water-in-oil droplets encapsulating a single chip to be transferred 10 close to the target substrate 40.

[0068] Specifically, the second pixel electrode layer 44 corresponds to the independent pixel unit at the target receptor hole 41 position of the target substrate 40, and is used to perform the initial capture and proximity action of the water-in-oil droplet that encapsulates the single chip to be transferred 10.

[0069] S132: Stop applying voltage to the second pixel electrode layer 44 and apply voltage to the first pixel electrode layer 43 to move the selected water-in-oil droplet encapsulating the single chip to be transferred 10 to the target acceptor hole 41 of the target substrate 40.

[0070] Specifically, the first pixel electrode layer 43 also corresponds to the target acceptor hole 41 position of the target substrate 40, and is used to perform the final precise positioning of the water-in-oil droplet that encapsulates the single chip to be transferred 10.

[0071] By setting a dual-layer structure of a first pixel electrode layer 43 and a second pixel electrode layer 44, and controlling the movement of the water-in-oil droplet using a step-by-step voltage application method, the second pixel electrode layer 44 provides initial attraction to the water-in-oil droplet when it approaches the target substrate 40, reducing the risk of collision between the water-in-oil droplet and the target substrate 40. This helps protect the structural integrity of the water-in-oil droplet encapsulating the individual chip 10 to be transferred. By switching to the first pixel electrode layer 43 for precise positioning, the water-in-oil droplet can be accurately guided to the target receiver hole 41, thereby improving positioning accuracy and facilitating high-precision alignment between the chip 10 to be transferred and the target receiver hole 41. The step-by-step driving mechanism of the dual-layer electrodes makes the movement of the water-in-oil droplet more controllable and stable, thereby reducing the risk of droplet deviation or splashing due to sudden changes in the electric field or the limitations of single-electrode driving, and thus improving the yield of the transfer process.

[0072] Please refer to the following: Figure 7 , Figure 13 , Figure 14 and Figure 15 , Figure 15 for Figure 14 In the enlarged schematic diagram of the XV section, in one embodiment, the second pixel electrode layer 44 divides the entire target substrate 40 into several square driving regions, each driving region corresponding to an independent secondary electrode 441. When the coarse fluid transport stage ends and the flow rate gradient decreases, the second pixel electrode layer 44 is activated. The large-sized secondary electrode 441 forms a large-scale electric field gradient, which strengthens the wettability of the hydrophobic layer 48 in the target region on the target substrate 40. The water-in-oil droplets surrounding the individual chips 10 to be transferred will spontaneously slide and converge towards the energized target region, thus completing the coarse positioning.

[0073] Specifically, when the water-in-oil droplet encapsulating a single chip to be transferred 10 approaches the target substrate 40, a voltage is first applied to the second pixel electrode layer 44. The electric field force generated by the dielectric wetting effect (Electrowetting on Dielectrics, EWOD) attracts the droplet to approach the surface of the target substrate 40, thereby achieving large-scale alignment and realizing the initial contact or proximity between the water-in-oil droplet and the surface of the target substrate 40.

[0074] Please refer to the following: Figure 7 , Figure 13 and Figure 16 In one embodiment, the first pixel electrode layer 43 includes a plurality of first electrode groups 431. Each first electrode group 431 includes two first electrodes 4311 and a second electrode 4312 with opposite polarities. The plurality of first electrode groups 431 are arranged in an array to form multiple electrode rows and multiple electrode columns. The first electrodes 4311 in the same electrode row are electrically connected, and the second electrodes 4312 in the same electrode column are electrically connected.

[0075] Specifically, the first pixel electrode layer 43 adopts a passive matrix row-column addressing architecture, and the first electrode group 431 is the basic structure constituting the pixel driving unit. Each first electrode group 431 corresponds to the position of a target receptor hole 41. Each first electrode group 431 contains two electrodes with opposite polarities, namely the first electrode 4311 and the second electrode 4312. The first electrode 4311 and the second electrode 4312 are spatially separated (e.g., using a dual-pad structure).

[0076] Several first electrodes 4311 are arranged horizontally to form multiple electrode rows (e.g., S1, S2, S3, ..., Sn), and several second electrodes 4312 are arranged vertically to form multiple electrode columns (e.g., D1, D2, D3, ..., Dn). All first electrodes 4311 in the same electrode row are electrically connected to the same row scan line via a common wire, and all second electrodes 4312 in the same electrode column are electrically connected to the same column data line via a common wire. Subsequently, by controlling the voltage combination of the row scan line and the column data line, any one of the first electrode groups 431 can be independently addressed and driven. During driving operation, for example, if a voltage is applied to a certain row (e.g., a voltage is applied to row S2), and a voltage is simultaneously applied to the corresponding column of a certain row (e.g., a voltage is applied to column D2), an electric field is formed between the first electrode 4311 and the second electrode 4312 located at the intersection of the row and the column, thereby generating a dielectric wetting effect on the water-in-oil droplet at that location, driving the water-in-oil droplet to move or be positioned.

[0077] By configuring the first electrode group 431 to include a first electrode 4311 and a second electrode 4312 with opposite polarities, and employing a row and column array arrangement and common connection, the first pixel electrode layer 43 can achieve precise addressing and driving of independent pixels. By applying voltage to specific rows and columns, a local electric field can be generated at the target acceptor aperture 41, thereby precisely controlling the movement and positioning of individual water-in-oil droplets and reducing the risk of interference to neighboring water-in-oil droplets. This is beneficial for improving integration and manufacturing yield, while ensuring that the driving voltage of each pixel site can be independently controllable, thus improving the accuracy of chip placement during mass transfer.

[0078] Please refer to the following: Figure 7 and Figure 13In one embodiment, the target substrate 40 further includes a buffer layer 45, an insulating layer 46, and a dielectric layer 47. The buffer layer 45 is located between the substrate 42 and the first pixel electrode layer 43, the insulating layer 46 is located between the first pixel electrode layer 43 and the second pixel electrode layer 44, and the dielectric layer 47 is located on the side of the second pixel electrode layer 44 away from the insulating layer 46.

[0079] Specifically, the substrate 42 is made of alkali-free borosilicate glass, and a buffer layer 45 (which can be made of silicon dioxide) is deposited on the substrate 42 by chemical vapor deposition. This buffer layer 45 can block the migration channels of residual alkali metals in the glass material of the substrate 42, and can also provide a high-adhesion interface for the subsequently sputtered metal electrodes, thereby reducing the risk of film peeling. The dielectric layer 47 can be prepared by atomic layer deposition (the dielectric layer 47 can be made of aluminum oxide).

[0080] In one embodiment, the thickness of the substrate 42 is 0.5mm-1.1mm, for example, the thickness of the substrate 42 is 0.5mm, 0.8mm or 1.1mm, depending on the requirements, and is not limited here.

[0081] In one embodiment, the thickness of the buffer layer 45 is 100nm-200nm, for example, the thickness of the buffer layer 45 is 100nm, 150nm or 200nm, depending on the requirements, and is not limited here.

[0082] In one embodiment, the thickness of the dielectric layer 47 is 200nm-500nm, for example, the thickness of the dielectric layer 47 is 200nm, 350nm or 500nm, depending on the requirements, and is not limited here.

[0083] Please continue reading. Figure 7 and Figure 13 In one embodiment, the target recipient hole 41 of the target substrate 40 is covered with a hydrophobic layer 48, so that when the chip to be transferred 10 falls into the target recipient hole 41, the water-in-oil droplets enveloping the chip to be transferred detach from the chip to be transferred 10.

[0084] Specifically, the pore wall of the target acceptor pore 41 is covered with a hydrophobic layer 48, which can cover the inner wall surface of the target acceptor pore 41. The hydrophobic layer 48 can be formed by atomic layer deposition or other methods. During the transfer process, when the water-in-oil droplet encapsulating a single chip 10 to be transferred is driven above the target acceptor pore 41, the chip 10 to be transferred begins to enter the target acceptor pore 41 under the assistance of gravity and electric field. Since the non-functional surface 12 of the chip 10 to be transferred is hydrophobically modified, it is similar in material to the hydrophobic layer 48 of the pore wall of the target acceptor pore 41, both being low surface energy materials. When the two come into contact, a strong van der Waals adsorption force will be generated. At the same time, there is a large interfacial tension between the aqueous phase droplet in the water-in-oil droplet and the hydrophobic pore wall of the target acceptor pore 41. The aqueous phase is difficult to wet the hydrophobic pore wall of the target acceptor pore 41, thus generating an upward contraction force on the water-in-oil droplet. At this time, the downward adsorption force at the bottom of the target acceptor pore 41 and the upward interfacial tension at the pore wall work together to separate the chip 10 to be transferred from the water-in-oil droplet.

[0085] It is understandable that the target substrate 40 is also covered with a hydrophobic layer 48 except for the target acceptor hole 41. The material of the hydrophobic layer 48 includes an amorphous fluoropolymer, and the thickness of the hydrophobic layer 48 is 20nm-50nm. For example, the thickness of the hydrophobic layer 48 is 20nm, 35nm or 50nm, which is set according to the requirements and is not limited here.

[0086] Please refer to it again. Figure 1 , Figure 7 and Figure 13 In one embodiment, before the water-in-oil droplet encapsulating the chip 10 to be transferred detaches from the chip 10, the method further includes: stopping the application of voltage to the first pixel electrode layer 43.

[0087] Specifically, when a voltage is applied to the first pixel electrode layer 43, the water-in-oil droplet encapsulating a single chip 10 to be transferred can be driven to move toward the target acceptor aperture 41, and assist the chip 10 to be transferred in initially falling into the aperture of the target acceptor aperture 41. When the bottom of the chip 10 to be transferred contacts the hydrophobic layer 48 at the bottom of the target acceptor aperture 41 and generates sufficient van der Waals adsorption force, the voltage applied to the first pixel electrode layer 43 is stopped. Since the sidewall and the hydrophobic layer 48 at the bottom of the target acceptor aperture 41 have a repulsive effect on the aqueous droplet, the water-in-oil droplet can separate from the surface of the chip 10 to be transferred during the shrinkage process. The chip 10 to be transferred can be fixed in the target acceptor aperture 41 by the van der Waals adsorption force between the bottom of the chip 10 to be transferred and the bottom of the target acceptor aperture 41, thereby achieving complete detachment of the chip 10 to be transferred from the water-in-oil droplet, further improving the accuracy and yield of the transfer.

[0088] Please refer to the following: Figure 1 , Figure 2 and Figure 7In one embodiment, after step S130, the method further includes: S140: Supercritical carbon dioxide is used to clean the target substrate 40.

[0089] Specifically, after the chip to be transferred 10 falls into the target acceptor hole 41 on the target substrate 40, the target substrate 40 has residual oil phase medium, stabilizer and possibly trace amount of aqueous phase residue used to encapsulate the chip to be transferred 10. At this time, the target substrate 40 is cleaned by supercritical carbon dioxide. Taking advantage of its high solubility and low viscosity, the residual perfluorinated oil phase, stabilizer and nanoparticles can be efficiently dissolved and completely removed from the cavity, thereby achieving thorough cleaning of the target substrate 40 and the chip surface, which is beneficial to improving the yield of subsequent packaging or bonding processes.

[0090] In summary, the above-described transfer method, by differentially modifying the wettability of the chip 10 to be transferred and utilizing the principle of minimizing interfacial free energy, enables the chip 10 to spontaneously form a horizontal orientation within the water-in-oil droplet, with the functional surface 11 facing the water and the non-functional surface 12 facing the oil. This achieves self-alignment of the chip 10 during fluid transport, effectively reducing the risk of inverted or lateral defects caused by random tumbling of the chip 10. Simultaneously, the balance mechanism of inertial lift and Dean drag in the curved flow channel 30 allows for precise screening of the water-in-oil droplet encapsulating a single chip 10, improving the yield of subsequent transfers and reducing the risk of abnormal filling of the target substrate 40 due to multiple chips or empty droplets. The hydrophobic design at the bottom of the target acceptor aperture 41, combined with capillary adsorption, ensures that the chip 10 is firmly anchored within the target acceptor aperture 41. Furthermore, the rebound of the water-in-oil droplet under interfacial tension facilitates effective separation of the target chip and the water-in-oil droplet, reducing damage during the transfer process.

[0091] The above are merely embodiments of this application and do not limit the scope of this patent application. Any equivalent structural or procedural changes made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this application.

Claims

1. A chip transfer method, characterized in that, The method includes: Multiple chips to be transferred are preprocessed, wherein, during the preprocessing, the functional surfaces of the chips to be transferred are hydrophilic and the non-functional surfaces of the chips to be transferred are hydrophobic. The pre-processed chips to be transferred are transported to the transport channel to obtain multiple water-in-oil droplets that encapsulate the chips to be transferred. The chips to be transferred, which are encapsulated in the water-in-oil droplets, are in a horizontal position with their functional side facing the water and their non-functional side facing the oil. The water-in-oil droplets encapsulating the chip to be transferred are conveyed to a curved flow channel to filter out the water-in-oil droplets encapsulating a single chip to be transferred. The selected water-in-oil droplets are transferred to the target acceptor aperture of the target substrate, and the chip to be transferred that has fallen into the target acceptor aperture is detached from the water-in-oil droplets.

2. The method according to claim 1, characterized in that, The transport channel includes a transport section and a mixing section. The width of the mixing section is smaller than the internal width of the transport section. The transport section contains an aqueous phase channel and an oil phase channel nested around the aqueous phase channel. The mixing section contains a mixing channel that communicates with both the aqueous phase channel and the oil phase channel. The step of transporting the pre-treated chips to the transport channel to obtain multiple water-in-oil droplets encapsulating the chips includes: The pre-processed chips to be transferred are transported into the aqueous phase channel; Receive a plurality of water-in-oil droplets encapsulating the chip to be transferred from one end of the mixing channel away from the transport section; In the mixing channel, the multiple water-in-oil droplets encapsulating the chip to be transferred spontaneously adjust to a horizontal orientation with the functional side facing the water and the non-functional side facing the oil due to the minimization of interfacial free energy.

3. The method according to claim 2, characterized in that, The oil phase channel on the back of the transport section is doped with a stabilizer, which includes silica nanoparticles and perfluoropolyether ammonium carboxylate. The water-in-oil droplet includes an aqueous inner phase, the stabilizer, and an oil outer phase arranged sequentially on the chip to be transferred.

4. The method according to claim 2, characterized in that, The flow rate in the aqueous phase channel ranges from 60 μL / min to 100 μL / min, and the flow rate in the oil phase channel ranges from 150 μL / min to 400 μL / min.

5. The method according to claim 1, characterized in that, The curved flow channel includes a curved section and a screening section. The width of the screening section is wider than that of the curved section, and the screening section is provided with at least two spaced-apart flow dividers. The step of conveying the water-in-oil droplets encapsulating the chip to be transferred to a curved flow channel to filter out the water-in-oil droplets encapsulating individual chips to be transferred includes: Multiple chips to be transferred are fed into the curved section from one end of the curved section; Receive the water-in-oil droplet containing a single chip to be transferred from the end of the screening section away from the curved section; In this process, the multiple water-in-oil droplets entering the curved section are stratified, and the multiple water-in-oil droplets entering the screening section are separated by multiple flow-dividing blades, so as to distinguish the multiple water-in-oil droplets into empty water-in-oil droplets, water-in-oil droplets encapsulating a single chip to be transferred, and water-in-oil droplets encapsulating multiple chips to be transferred.

6. The method according to claim 1, characterized in that, The target substrate includes a substrate and a first pixel electrode layer and a second pixel electrode layer sequentially disposed on the substrate; the step of transferring the selected water-in-oil droplets to the target acceptor aperture of the target substrate, and causing the chip to be transferred that falls into the target acceptor aperture to detach from the water-in-oil droplets, includes: A voltage is applied to the second pixel electrode layer to bring the selected water-in-oil droplets encapsulating a single chip to be transferred closer to the target substrate; Stop applying voltage to the second pixel electrode layer and apply voltage to the first pixel electrode layer to move the selected water-in-oil droplet encapsulating a single chip to be transferred to the target acceptor aperture of the target substrate.

7. The method according to claim 6, characterized in that, The first pixel electrode layer includes several first electrode groups, each first electrode group including two first electrodes and a second electrode with opposite polarities. The several first electrodes are arranged in an array in multiple electrode rows and multiple electrode columns. The first electrodes in the same electrode row are electrically connected, and the second electrodes in the same electrode column are electrically connected.

8. The method according to claim 6, characterized in that, The target substrate has a hydrophobic layer covering the wall of the target acceptor hole, so that when the chip to be transferred falls into the target acceptor hole, the water-in-oil droplet enveloping the chip to be transferred detaches from the chip to be transferred.

9. The method according to claim 8, characterized in that, Before the water-in-oil droplet encapsulating the chip to be transferred detaches from the chip, the method further includes: Stop applying voltage to the first pixel electrode layer.

10. The method according to claim 1, characterized in that, After the step of transferring the selected water-in-oil droplets to the target acceptor aperture of the target substrate and causing the chip to be transferred, which has fallen into the target acceptor aperture, to detach from the water-in-oil droplets, the method further includes: The target substrate was cleaned using supercritical carbon dioxide.

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