Transfer method

Abstract

The present invention relates to a transfer method for transferring a plurality of microstructures that are provided on a substrate to another substrate by laser irradiation, the transfer method comprising a transfer step for irradiating a first microstructure with a laser through the substrate and transferring the first microstructure to the other substrate, and an additional irradiation step for irradiating the transferred first microstructure with at least one laser. There is thereby provided a transfer method with which it is possible to remove residue adhering to a microstructure while improving productivity.

Description

Transfer method

[0001] The present invention relates to a transfer method for transferring a plurality of microstructures provided on a substrate to another substrate by laser irradiation.

[0002] In recent years, nitride semiconductor optical devices have come to be used as backlights for liquid crystal displays and signage displays. These applications require a large number of optical devices to be used at once, so high-speed transfer technology is required. High-speed transfer technology generally involves bulk transfer using a stamping method that uses a stamper, and it has become possible to transfer 1,000 to tens of thousands of devices at a time.

[0003] Optical devices are mass-produced on sapphire substrates using semiconductor processes. To produce a 4-inch display substrate using LEDs called micro-LEDs, which are 100 μm square or smaller, several million micro-LEDs are required. Micro-LEDs are tiny devices measuring several tens of μm in size, and are used after being separated from the sapphire substrate, which serves as an epitaxial substrate.

[0004] The separation method is generally to bond a support substrate as a donor precursor substrate to the optical devices arranged on a sapphire substrate, and then separate the optical devices from the sapphire substrate by laser lift-off, thereby obtaining a donor substrate with a large number of optical devices arranged on its surface.

[0005] Such a method is not limited to optical devices, but can also be applied to manufacturing a donor substrate having a plurality of transfer objects, such as minute semiconductor devices, arranged on its surface.

[0006] In addition, the object to be transferred on the donor substrate can be transferred onto a receptor substrate so that it is arranged in a manner corresponding to the circuit board of the product, and then transferred from this receptor substrate to another substrate, such as the circuit board of the product, using a stamping method.

[0007] For example, Patent Document 1 proposes a method for transferring an object to be transferred from a donor substrate to a receptor substrate with high precision using laser irradiation.

[0008] Japanese Patent Application Laid-Open No. 2000-4478

[0009] When multiple microstructures provided on a substrate are transferred to another substrate by laser irradiation, residues may be generated on the transferred microstructures and their surroundings. These residues are thought to originate from polymeric materials (resins such as polyimide, rubber, etc.) such as adhesives that secure the substrate and the microstructures. After transfer, a removal process using wet etching (cleaning) or the like is required, which reduces productivity.

[0010] The present invention has been made to solve the above problems, and an object of the present invention is to provide a transfer method that can remove residues adhering to a minute structure while improving productivity.

[0011] The present invention has been made to achieve the above-mentioned object, and provides a transfer method for transferring multiple microstructures arranged on a substrate to another substrate by laser irradiation, the transfer method including a transfer step of irradiating a laser through the substrate toward a first microstructure and transferring the first microstructure to the other substrate, and an additional irradiation step of irradiating the transferred first microstructure with a laser at least once.

[0012] According to this transfer method, by providing an additional step of irradiating the transferred microstructure with a laser, it becomes possible to remove residues while the microstructure is being transferred, thereby significantly improving productivity.

[0013] At this time, in the additional irradiation step, the second microstructure remaining on the base material can be irradiated with the laser together, and the second microstructure can be transferred to the other base material.

[0014] This makes it possible to further improve productivity.

[0015] In this case, the first microstructure and the second microstructure can be disposed adjacent to each other on the substrate.

[0016] Such a microstructure on a substrate can be transferred more efficiently.

[0017] At this time, a laser can be further irradiated onto the third microstructure remaining on the substrate, the transferred first microstructure, and the transferred second microstructure together, thereby transferring the third microstructure to the other substrate.

[0018] This allows for more stable removal of residues and improves productivity.

[0019] In this case, the second microstructure and the third microstructure can be disposed adjacent to each other on the substrate.

[0020] Such a microstructure on a substrate can be transferred more efficiently.

[0021] At this time, the substrate and the other substrate may be moved relatively in a certain direction, and the laser may be irradiated in a stationary or non-stationary state.

[0022] This means that if the laser is irradiated while the movement is stopped, the accuracy of the laser irradiation position and the transfer position of the microstructure can be improved, and if the laser is irradiated while the movement is not stopped, the throughput can be further improved.

[0023] In this case, the shape of the irradiated laser may be rectangular, and the movement may be in the direction of the long side of the rectangle.

[0024] This allows for greater flexibility in transfer and additional irradiation processing.

[0025] In this case, the length of the long side of the rectangular laser on the irradiation surface can be three times or more the length of the long side of the microstructure, and the length of the long side of the rectangular laser on the irradiation surface can be five times or more the length of the long side of the microstructure.

[0026] This allows for greater flexibility in transfer and additional irradiation processing.

[0027] In this case, there are a plurality of rectangular lasers, which can be arranged at intervals in the direction of the short side of the rectangle.

[0028] This allows for more productive processing.

[0029] At this time, the shape of the irradiated laser can be such that there are a plurality of lasers on the irradiated surface, each having a shape substantially the same as the size of the minute structure, and the plurality of lasers can be arranged spaced apart in the movement direction.

[0030] This allows for more accurate processing.

[0031] In this case, a plurality of lasers may be further provided in a direction perpendicular to the moving direction, spaced apart from the plurality of lasers, and may be arranged in a matrix.

[0032] This allows for more productive processing.

[0033] In this case, the plurality of minute structures can be provided on the substrate via a polymer material.

[0034] In particular, in such a case, the residue can be removed stably.

[0035] At this time, in the transferring step, the minute structure provided on the base material can be transferred to the other base material by a single laser irradiation.

[0036] This allows the minute structure to be transferred to another substrate more efficiently and stably.

[0037] At this time, in the additional irradiation step, the transferred microstructure can be irradiated with laser a plurality of times.

[0038] This allows the residue to be removed effectively.

[0039] At this time, the minute structure can be irradiated multiple times with a laser having an energy density smaller than that of the laser irradiated to the minute structure in the transfer step.

[0040] This makes it possible to more effectively suppress dust generation from the residue.

[0041] At this time, the total energy density of the laser beams irradiated multiple times can be made larger than the energy density of the laser beam irradiated onto the minute structure in the transfer step.

[0042] This allows the residue to be removed more effectively.

[0043] At this time, the energy density of the laser irradiated onto the transferred microstructure in the additional irradiation step can be made smaller than the energy density of the laser irradiated onto the microstructure in the transfer step.

[0044] This makes it possible to more effectively suppress dust generation from the residue.

[0045] At this time, the plurality of microstructures provided on the substrate and the other substrate can be spaced apart.

[0046] This makes it possible to more effectively suppress dust generation from the residue.

[0047] In this case, the laser irradiated onto the microstructure is shaped by passing through an opening in a photomask, and the transmittance of the opening through which the laser irradiated onto the transferred microstructure passes in the additional irradiation process can be smaller than the transmittance of the opening through which the laser irradiated onto the microstructure provided on the substrate passes in the transfer process.

[0048] This makes it possible to easily adjust the energy density of the laser irradiated onto the minute structure.

[0049] In this case, in the transfer step, the laser can be irradiated while the base material and the other base material are in contact with each other, and in the additional irradiation step, the laser can be irradiated while the base material and the other base material are separated from each other, forming a space between the base material and the other base material.

[0050] This allows for greater productivity and more accurate transfer.

[0051] At this time, in the additional irradiation step, oxygen gas can be supplied to the space between the substrate and the other substrate.

[0052] This effectively reduces dust generation (debris generation) during residue removal.

[0053] As described above, according to the transfer method of the present invention, by providing an additional laser irradiation process for the transferred microstructure, it becomes possible to remove residues during the transfer of the microstructure, thereby significantly improving productivity.

[0054] 1 is a schematic diagram illustrating an example of a transfer method of the present invention. FIG. 1 is a schematic diagram illustrating another example of the transfer method of the present invention. FIG. 2 is a schematic diagram illustrating yet another example of the transfer method of the present invention. FIG. 3 is a schematic diagram illustrating a state of a substrate and another substrate before a microstructure is transferred. FIG. 4 is a schematic diagram illustrating a first embodiment. FIG. 5 is a schematic diagram illustrating a process following FIG. 6. FIG. 7 is a schematic diagram illustrating a process following FIG. 8. FIG. 9 is a schematic diagram illustrating a process following FIG. 10. FIG. 11 is a schematic diagram illustrating a process following FIG. 11. FIG. 12 is a schematic diagram illustrating a process following FIG. 12. FIG. 13 is a schematic diagram illustrating a process following FIG. 14. FIG. 15 is a schematic diagram illustrating a process following FIG. 16. FIG. 13 is a schematic diagram illustrating a process following FIG. 16. FIG. 14 is a schematic diagram illustrating a process following FIG. 16. FIG. 15 is a schematic diagram illustrating a process following FIG. 16. FIG. 16 is a schematic diagram illustrating an example of a transfer apparatus. FIG. 16 is a schematic diagram illustrating an example of a photomask. 10 is a schematic diagram illustrating another embodiment of the transfer method of the present invention.

[0055] The present invention will be described in detail below, but the present invention is not limited thereto.

[0056] As described above, there has been a demand for a transfer method that can remove residues adhering to minute structures while improving productivity.

[0057] As a result of extensive research into the above-mentioned problems, the inventors have discovered a transfer method for transferring multiple microstructures arranged on a substrate to another substrate by laser irradiation, which includes a transfer step of irradiating a laser through the substrate toward a first microstructure and transferring the first microstructure to the other substrate, and an additional irradiation step of irradiating the transferred first microstructure with a laser at least once, and by providing an additional laser irradiation step for the transferred microstructure, it is possible to remove residues during the transfer of the microstructures, thereby significantly improving productivity, and have completed the present invention.

[0058] The present invention will now be described with reference to the drawings.

[0059] [Transfer Method] The present invention provides a transfer method for transferring multiple microstructures provided on a substrate to another substrate by laser irradiation. Figure 1 shows an example of the transfer method of the present invention. As shown in Figure 1, a first microstructure 20A, a second microstructure 21A, and a third microstructure 22A are provided on a substrate 1. The transfer method includes a transfer step (Figures 1(A)-(B)) in which a laser beam L is irradiated onto the first microstructure 20A through the substrate 1 to transfer the first microstructure 20A to another substrate 2, and an additional irradiation step (Figure 1(C)) in which the laser beam L is irradiated at least once onto the transferred first microstructure 20B. The microstructures are fixed to the substrate 1 with a polymeric material such as an adhesive 10, and can be transferred by, for example, laser ablation of the polymeric material through laser irradiation. After the transfer step, residue 11 may be generated on or around the transferred first microstructure 20B. This residue is thought to originate from the polymeric material (e.g., resin such as polyimide, rubber, etc.) such as the adhesive that fixes the microstructures to the substrate. After the transfer process, an additional irradiation process is performed in which the transferred first microstructure 20B is irradiated with a laser beam L to remove residue 11 derived from polymeric materials and the like adhering to the microstructure. This residue removal can be achieved, for example, by laser ablation or by irradiating the laser with a laser beam having an energy density weaker than that at which laser ablation occurs. Because these transfer and additional irradiation processes can be performed during the transfer process, the productivity of the transfer process can be significantly improved. In the example shown in FIG. 1 , the transfer position of the first microstructure onto the other substrate 2 is adjusted by relatively translating the substrate 1 and the other substrate 2. Note that while FIG. 1 depicts the residue 11 as having a thickness across the entire laser-irradiated surface of the microstructure, it does not necessarily exist in this shape; it may exist in a linear, spotted, or dotted shape on only a portion of the laser-irradiated surface. Furthermore, in FIG. 1 , the laser beam L merely schematically represents the size and direction of the laser irradiation area and does not necessarily mean that the laser is passing through the microstructure 20A, for example, as shown in FIG. 1(A). The same applies to FIGS. 2 and 3.

[0060] The upper limit of the number of times of irradiation with the laser L in the additional irradiation step is not particularly limited, but can be, for example, 100 times or less, 50 times or less, 30 times or less, 10 times or less, or 5 times or less.

[0061] FIG. 2 shows a mode in which a laser is irradiated simultaneously onto multiple microstructures. In the example shown in FIG. 2, a transfer process in which the second microstructure 21A remaining on the substrate 1 and the first microstructure 20B already transferred are transferred to another substrate 2 by irradiating the second microstructure 21A with a laser together with the first microstructure 20B already transferred is performed in parallel with an additional irradiation process for the first microstructure 20B. In other words, a single laser irradiation is performed on both the second microstructure 21A remaining on the substrate 1 and the first microstructure 20B already transferred. In another aspect, the transfer process for the second microstructure 21A can also be considered an additional irradiation process for the first microstructure 20B. From the perspective of the laser irradiation side, the transfer process and the additional irradiation process can be performed in a simultaneous laser irradiation process. This allows for more efficient transfer of the microstructures. In the example shown in FIG. 2, the transfer position of the first microstructure 20B onto the other substrate 2 is adjusted by relatively translating the substrate 1 and the other substrate 2. For example, by moving the substrate 1 and the other substrate 2 in parallel in the same direction relative to the irradiated laser and making the amount of movement of the other substrate 2 greater than the amount of movement of the substrate 1, it is possible to widen the interval between the microstructures transferred onto the other substrate 2. As mentioned above, in Fig. 2 as well, the laser L merely schematically represents the size and direction of the laser irradiation area, and does not necessarily mean, for example, that the laser stops at the height of the surface of the microstructure 20B in Fig. 2. The same is true in Fig. 3.

[0062] It is preferable that the first microstructure 20A and the second microstructure 21A are disposed adjacent to each other on the substrate 1. Such a microstructure on the substrate allows for more efficient transfer and removal of the residue 11.

[0063] FIG. 3 shows another example of irradiating multiple microstructures with a laser simultaneously. In the example shown in FIG. 3, the third microstructure 22A remaining on the substrate 1 and not yet transferred is irradiated with a laser together with the first microstructure 20B and the second microstructure 21B already transferred to another substrate 2. This allows the transfer process of the third microstructure 22A to the other substrate 2 and the additional irradiation process of the first microstructure 20B and the second microstructure 21B to be performed in parallel. This allows for more stable removal of the residue 11 and more efficient transfer of the microstructures, further improving productivity. In the example of FIG. 3, the transfer positions of the first and second microstructures on the other substrate 2 are adjusted by moving the substrate 1 and the other substrate 2 parallel to each other.

[0064] It is preferable that the second microstructure 21A and the third microstructure 22A are disposed adjacent to each other on the substrate 1. Such a microstructure on the substrate allows for more efficient transfer and removal of residues.

[0065] 1 to 3, it is preferable to move the substrate 1 and the other substrate 2 relatively in a fixed direction. Furthermore, the irradiation of the laser L may be performed in a state where the relative movement of the substrate 1 and the other substrate 2 is stopped, or may be performed while the substrate 1 and the other substrate 2 are moving in a non-stop state. If the irradiation of the laser L is performed in a state where the movement is stopped, the accuracy of the laser irradiation position and the transfer position of the microstructure can be increased, and if the irradiation of the laser L is performed in a non-stop state, the throughput can be further improved.

[0066] (Microstructure) The microstructure to be transferred by the transfer method of the present invention is not particularly limited. Examples include semiconductor elements such as micro LEDs. The multiple microstructures may be mounted on a substrate via an adhesive such as a polymeric material. In such cases, the removal of residues by the additional irradiation step of the transfer method of the present invention is particularly effective. It is preferable to select an adhesive that generates little dust even after laser ablation. Furthermore, to facilitate residue removal, it is preferable to make the thickness of the adhesive as thin as possible, more preferably 1 μm or less, particularly preferably 0.8 μm or less, and most preferably 0.6 μm. From the viewpoints of uniformly disposing the adhesive layer and adhesive strength, the preferred lower limit is approximately 0.2 μm.

[0067] (Substrate) The substrate 1 is not particularly limited as long as it can be provided with a microstructure. When the microstructure is a semiconductor element, for example, the substrate may be a substrate on which the element is formed, a donor substrate, or a receptor substrate when the substrate is transferred from a substrate on which the element is formed to a circuit board of a product via a donor substrate and a receptor substrate. Specifically, it is preferable that the substrate is transparent to the irradiated laser, and a glass substrate such as synthetic quartz is more preferable.

[0068] (Other Substrate) The other substrate 2 is also not particularly limited as long as it can accommodate the transfer of the microstructure. When the microstructure is a semiconductor element, for example, it may be a donor substrate, receptor substrate, or circuit board when the element is transferred from a substrate on which the element is formed to a donor substrate, receptor substrate, or circuit board for the product circuit board. The other substrate preferably includes a shock-absorbing and / or adhesive layer (PDMQ, solder paste, etc.) at the position where the microstructure is to be provided. When the other substrate is a circuit board and the microstructure is electrically connected to the circuit board in a face-down manner, the shock-absorbing and / or adhesive layer preferably includes a layer containing a conductive material. Examples of such conductive materials include isotropic conductive materials such as solder paste and anisotropic conductive materials such as anisotropic conductive adhesives. Furthermore, even in a face-up manner, the above-mentioned conductive materials may be used when electrical connection is required.

[0069] (Laser) The laser L is not particularly limited, but can be, for example, an excimer laser. The shape of the laser L irradiated onto the microstructure (the shape of the irradiation area of ​​the laser L) is not particularly limited as long as the microstructure can be transferred and residues of the microstructure can be removed. The shape of the laser L (the shape of the irradiation area of ​​the laser L) described below can be appropriately formed, for example, by passing the laser through a photomask. Examples of excimer lasers include ArF excimer lasers (wavelength 193 nm), KrF excimer lasers (wavelength 248 nm), XeCl excimer lasers (wavelength 308 nm), and XeF excimer lasers (wavelength 353 nm). From the viewpoints of proven use and ease of availability, a KrF excimer laser is preferred.

[0070] The shape of the irradiated laser L (the shape of the irradiation area of ​​the laser L) is not particularly limited. For example, the shape of the laser L irradiated onto the microstructure (the shape of the irradiation area of ​​the laser L) can be rectangular. In this case, the long side direction of the rectangle preferably corresponds to the relative movement direction of the substrate 1 and the other substrate 2. It is also preferable that there are multiple rectangular lasers, and they are arranged spaced apart in the short side direction of the rectangle (see Figures 5 to 10). Such a laser irradiation area is less subject to restrictions on the arrangement interval (transfer pitch) of the microstructures on the other substrate 2, thereby improving the degree of freedom in transfer and additional irradiation processing. Being able to transfer and additionally irradiate multiple microstructures with a single laser irradiation further improves productivity. Furthermore, by using a rectangular shape, the laser can also be irradiated between microstructures on the other substrate, making it easier to remove residues present in such locations. The case of such a shape of the laser L will be described in detail in the first embodiment described below with reference to Figures 4 to 11.

[0071] Furthermore, the length of the long side of the rectangular shape of the laser L is preferably at least three times the length of the long side of the microstructure, and even more preferably at least five times. This allows for even greater freedom in transfer and additional irradiation processing. The upper limit of the ratio of the long side of the rectangular shape of the laser L to the long side of the microstructure is not particularly limited, but can be, for example, 100 times or less, 50 times or less, 30 times or less, or 10 times or less.

[0072] The shape of the laser L irradiated onto the microstructure (the shape of the irradiation area of ​​the laser L) may be such that there are multiple lasers with a shape approximately the same as the size of the microstructure on the irradiation surface. In this case, the arrangement of the laser irradiation areas is preferably N times (N: integer) the arrangement pitch of the microstructures arranged on the other substrate 2. The multiple lasers are spaced apart in the relative movement direction of the substrate 1 and the other substrate 2. It is also preferable that multiple lasers are arranged in a matrix pattern, spaced apart from the multiple lasers, in a direction perpendicular to the relative movement direction of the substrate 1 and the other substrate 2 (see Figures 12 to 17). Such a laser irradiation area allows multiple microstructures to be transferred and additionally irradiated with a single laser irradiation, further improving productivity. The shape of the laser L will be described in detail in the second embodiment described below with reference to Figures 12 to 17.

[0073] In the transfer process, it is preferable that the microstructure provided on the substrate 1 is transferred to another substrate 2 by a single laser irradiation. Therefore, it is preferable that the energy density of the laser irradiated onto the microstructure in the transfer process is an energy density that sufficiently laser ablates the polymer material that fixes the substrate and the microstructure with a single irradiation. Here, laser ablation is generally understood as a phenomenon in which, when a laser beam is irradiated onto the surface of a solid or liquid, plasma is generated and the constituent materials of the surface are explosively released. Note that, as long as stable transfer can be achieved, the energy density does not necessarily have to be sufficient for laser ablation.

[0074] In the additional irradiation process, it is preferable to irradiate the transferred microstructure with a laser multiple times. Multiple laser irradiations enable reliable removal of residues and more effectively suppress dust generation. In this case, it is preferable to irradiate the microstructure with a laser multiple times with an energy density lower than the energy density of the laser irradiated onto the microstructure in the transfer process. By using a relatively high energy density during transfer, the transfer (transfer) positioning accuracy can be improved, and by using a lower energy density during additional irradiation than the irradiation for transfer, it is expected that dust generation during residue removal can be suppressed. Furthermore, the total energy density of the multiple lasers irradiated in the additional irradiation process may be greater than the energy density of the laser irradiated onto the microstructure in the transfer process. Residues can be removed more effectively.

[0075] Furthermore, the energy density of the laser irradiated onto the transferred microstructure in the additional irradiation step is not particularly limited. The energy density of the laser irradiated in one pass in the additional irradiation step may be the same as that in the transfer step, but is preferably smaller than the energy density of the laser irradiated onto the microstructure in the transfer step. For example, the energy density of the laser irradiated onto the microstructure in the transfer step is set to 700 to 2000 mJ / cm. ２ When the laser energy density in the additional irradiation step is set to about 30 to 300 mJ / cm ２By setting the energy density at about this level, it is possible to more effectively suppress the generation of soot-like particles during residue removal and to suppress excessive laser irradiation of other substrates. Here, the energy density of a single laser irradiation in the additional irradiation step is preferably smaller than the energy density at which the polymer material is sufficiently laser ablated. When a polymer material is laser ablated, part of the polymer material may remain as soot-like carbon-based debris, and in order to suppress this, it is preferable to reduce the energy density of the laser irradiated in one irradiation. Although the energy density of a single laser irradiation in this additional irradiation step can vary depending on the type of polymer material and the wavelength of the irradiated laser, it can be selected based on the change in roughness of the polymer material surface observed with a surface roughness meter when the polymer material is irradiated with a laser at different energy densities.

[0076] It is preferable that the plurality of microstructures provided on the substrate 1 are spaced apart from the other substrate 2. In this state, air is present around the plurality of microstructures provided on the substrate 1, and therefore, compared to the case of removing residues by transfer and additional irradiation performed in a state in which the plurality of microstructures provided on the substrate 1 are in contact with the other substrate 2, when the polymer material and its residues are irradiated with a laser, they are more likely to become carbon dioxide gas rather than soot-like carbon-based debris, and dust generation can be more effectively suppressed.

[0077] The laser irradiated onto the microstructure is preferably shaped by passing through an opening in a photomask. Figure 19 shows an example of a photomask. Figure 19(A) shows a rectangular laser, and Figure 19(B) shows an example of a photomask for shaping a laser to match the shape of the microstructure. Furthermore, in the additional irradiation process, the transmittance of the opening through which the laser irradiated onto the microstructure transferred onto another substrate 2 passes can be made smaller than the transmittance of the opening through which the laser irradiated onto the microstructure provided on the substrate 1 passes in the transfer process, thereby easily adjusting the energy density of the laser L as described above. For example, the transmittance can be changed by using a semi-transparent film as a shielding film in the opening of the photomask. It is preferable to increase the transmittance in the irradiation section used in the transfer process to improve transfer position accuracy, and to decrease the transmittance in the irradiation section used in the additional irradiation process to suppress dust generation during residue removal.

[0078] FIG. 20 shows another embodiment of the transfer method of the present invention. Substrate 1 and substrate 2 are each mounted on a substrate stage. As shown in FIG. 20(A), substrate 1 and substrate 2, each equipped with a first microstructure 20A, a second microstructure 21A, and a third microstructure 22A, are brought into contact with each other. Laser L is then irradiated through substrate 1 toward first microstructure 20A, transferring first microstructure 20A to another substrate 2 (FIG. 20(B)). Substrate 1 and substrate 2 are then separated to form a space between the two substrates. Then, with the two substrates spaced apart, an additional irradiation step (FIG. 20(C)) is performed in which laser L is irradiated at least once toward the transferred first microstructure 20B. These steps (FIGS. 20(A) to 20(C)) are repeated. This significantly improves productivity while enabling more accurate transfer.

[0079] Furthermore, as shown in FIG. 20(C), in the additional irradiation step, by supplying an oxygen-containing gas using an oxygen gas supply means 50 or the like to at least the space between the substrate 1 and the substrate 2, it is possible to create an environment with a higher oxygen concentration than the atmosphere, and as a result, it is possible to effectively reduce dust generation (generation of debris) during residue removal.

[0080] The supply of oxygen-containing gas is sufficient as long as at least the space between substrate 1 and substrate 2 is an environment with a higher oxygen concentration than the atmosphere. The entire space including substrate 1 and substrate 2 may have a high oxygen concentration, or only the space between substrate 1 and substrate 2 may have a high oxygen concentration. Furthermore, oxygen gas alone or diluted oxygen gas may be used as the oxygen-containing gas. Furthermore, although the laser irradiation mode in Figure 20 is the same as that in Figure 1, it goes without saying that the laser irradiation modes described in Figures 2 to 10 and 12 to 17 can also be applied.

[0081] By repeatedly transferring and mounting the microstructures as described above, a large number of microstructures can be transferred at the required pitch onto a large-area microstructure receiving substrate (substrate 2). For example, if the microstructures are semiconductor elements, the element supply substrate (substrate 1) has a diameter of 4 inches (100 mm) and an element pitch of 6 μm, and the element receiving substrate (substrate 2) is 300 mm × 350 mm and a pixel pitch of 90 μm, approximately 15 element receiving substrates can be produced from one element supply substrate.

[0082] The transfer method of the present invention can be applied to the LLO (Laser Lift Off) method and the LIFT (Laser Induced Forward Transfer) method.

[0083] [Transfer Apparatus] The transfer apparatus used to carry out the transfer method of the present invention is not particularly limited as long as it can irradiate a laser onto an object to be transferred from one substrate to another. For example, a transfer apparatus such as that shown in FIG. 18 can be used. The transfer apparatus 100 shown in FIG. 18 includes a laser oscillator 110, a shaping optical system 120, a photomask 130, a folding mirror 140, a reduction projection lens 150, a stage 160, an alignment camera 170, a controller 180, etc.

[0084] The stage 160 is composed of an upper stage 161 having an opening 161a and supporting the substrate 1, and a lower stage 162 supporting the other substrate 2. The stage 160 is configured to support the substrate 1 and the other substrate 2 so that they face each other, and each can move independently.

[0085] The laser oscillator 110 is configured to oscillate, for example, a pulsed laser beam L. In the transfer device 100, the laser beam L oscillated from the laser oscillator 110 is shaped through a shaping optical system 120, further shaped through a photomask 130, has its traveling direction changed by a folding mirror 140, and further passes through a reduction projection lens 150. The laser beam 20 then passes through an opening 161a of an upper stage 161 to form an optical path that reaches the substrate 1. That is, the photomask 130 is disposed between the optical path of the laser oscillator 110 and the stage 160.

[0086] 18, the laser oscillator 110, the photomask 130, and the stage 160 (upper stage 161 and lower stage 162) are configured so that the laser L from the laser oscillator 110 can be irradiated simultaneously onto a plurality of microstructures 3. The controller 180 is configured so as to be able to control the transfer device 100 so as to perform the transfer method of the present invention as described below. Note that detailed configurations and operation methods of other transfer devices can be implemented by referring to, for example, International Publication No. 2019 / 244362.

[0087] Based on the above explanation, the transfer method of the present invention will be described in more detail using Figures 4 to 17. In each of Figures 4 to 17, (A) shows a view from the laser irradiation direction (the back side of the substrate), and (B) shows a view from the side relative to the laser irradiation direction. Figures 4 and 11 are common to the first and second embodiments described below. Figure 4 shows the substrate 1 and another substrate 2 before the first microstructure 3A is transferred, and Figure 11 shows the substrate 1 and another substrate 2 after multiple microstructures (3B to 8B) have been transferred. As shown in Figure 4, multiple microstructures are provided adjacent to each other on the substrate 1 before transfer. The surface of the substrate 1 on which the multiple microstructures are provided is opposed to the surface of the other substrate 2 to which the microstructures are to be transferred, and the microstructures are transferred by irradiating the laser L from the side of the substrate 1 on which the microstructures are not provided. Then, after transfer, the multiple microstructures (3B to 8B) are transferred to the desired positions on the other substrate 2, as shown in Figure 11.

[0088] [First Embodiment] A transfer method according to a first embodiment of the present invention is shown in Figures 5 to 10. In the first embodiment, when transferring a plurality of microstructures provided on a substrate 1 to another substrate 2, the shape of the laser L irradiated onto the microstructures (the shape of the irradiation area of ​​the laser L) is rectangular, and multiple rows of laser irradiation are performed spaced apart in the direction of the short side of the rectangle. Here, the multiple rows of lasers can be spaced apart at a pitch that is, for example, N times (N: integer) the arrangement pitch of the microstructures on the substrate 1. In this embodiment, an example of three times the pitch is shown.

[0089] First, as shown in Figure 5, the laser is irradiated only onto the microstructures in the first row from the right on the substrate 1, and the microstructures 3B (there are multiple microstructures in the depth direction in Figure 5(B)) are transferred onto another substrate 2. At this point, residue (not shown) may be attached to the microstructures 3B. As mentioned above, in Figure 5, the laser L merely schematically represents the size and direction of the laser irradiation area, and does not necessarily mean, for example, that the laser stops at the height of the back surface of the substrate 1 (the surface on which the microstructures are not provided). The same applies to Figures 6 to 10 and Figures 12 to 17.

[0090] Next, as shown in Figure 6, the substrate 1 and the other substrate 2 are moved in parallel, and the laser is irradiated onto the microstructures 4A (see Figure 5) in the second row from the right on the substrate 1, to transfer the microstructures 4B onto the other substrate 2. At this time, the laser is also irradiated onto the microstructures 3B that have already been transferred onto the other substrate 2, and any residue of the microstructures 3B is removed. Note that this irradiation may leave residue of the microstructures 3B, and the remaining residue can be removed by subsequent additional laser irradiation. In this embodiment, the moving speed of the other substrate 2 is doubled compared to the moving speed of the substrate 1, thereby widening the spacing between the microstructures transferred onto the other substrate 2.

[0091] Next, as shown in FIG. 7, the substrate 1 and the other substrate 2 are moved in parallel, and the microstructure 5A (see FIG. 6) in the third row from the right on the substrate 1 is irradiated with a laser, transferring the microstructure 5B onto the other substrate 2. At this time, the microstructures 3B and 4B already transferred onto the other substrate 2 are also irradiated with the laser, removing any residue of the microstructures 3B and 4B. By further repeating this parallel movement of the substrate 1 and the other substrate 2 and laser irradiation (FIGS. 8-10), the microstructures 6A, 7A, and 8A provided on the substrate 1 are transferred onto the other substrate 2, thereby obtaining another substrate 2 onto which the microstructures 3B, 4B, 5B, 6B, 7B, and 8B are transferred. Furthermore, the microstructures 3B, 4B, 5B, 6B, 7B, and 8B transferred onto the other substrate 2 are subjected to at least one additional laser irradiation after transfer, thereby removing or reducing any residue.

[0092] 12 to 17 show a transfer method according to a second embodiment of the present invention. In the second embodiment, when a plurality of microstructures provided on a substrate 1 are transferred to another substrate 2, the shape of the laser L irradiated onto the microstructures (the shape of the irradiation area of ​​the laser L) is set to be substantially the same as the size of the microstructures, and a plurality of laser beams are arranged in a matrix, so that the laser beam is irradiated at a plurality of locations corresponding to the microstructures before and after the transfer.

[0093] First, as shown in Fig. 12, a laser is irradiated only onto the microstructures in the first row from the right on the substrate 1, and the microstructures 3B are transferred onto another substrate 2 (there are multiple microstructures in the depth direction of Fig. 12(B)). At this point, residues (not shown) may be attached to the microstructures 3B.

[0094] Next, as shown in Figure 13, the substrate 1 and the other substrate 2 are moved in parallel, and the laser is irradiated onto the microstructures 4A (see Figure 12) in the second row from the right on the substrate 1, and the microstructures 4B are transferred onto the other substrate 2. At this time, the microstructures 3B already transferred onto the other substrate 2 are also irradiated with a laser having approximately the same shape as the microstructure, and residues of the microstructures 3B are removed. Note that if the microstructures 3B are further subjected to subsequent laser irradiation, residues of the microstructures 3B may remain.

[0095] Next, as shown in FIG. 14, the substrate 1 and the other substrate 2 are moved in parallel, and the microstructure 5A (see FIG. 13) in the third row from the right on the substrate 1 is irradiated with a laser to transfer the microstructure 5B onto the other substrate 2. At this time, the microstructures 3B and 4B already transferred onto the other substrate 2 are also irradiated with the laser, and residues of the microstructures 3B and 4B are removed. By further repeating this parallel movement of the substrate 1 and the other substrate 2 and laser irradiation (FIGS. 15 to 17), the microstructures 5A, 6A, 7A, and 8A provided on the substrate 1 are transferred onto the other substrate 2, and another substrate 2 onto which the microstructures 3B, 4B, 5B, 6B, 7B, and 8B are transferred can be obtained. Furthermore, the microstructures 3B, 4B, 5B, 6B, 7B, and 8B transferred onto the other substrate 2 are subjected to at least one additional laser irradiation after transfer, so residues are removed or reduced.

[0096] The transfer method of the present invention can efficiently remove residues of the minute structure, thereby improving the productivity of transfer.

[0097] This specification includes the following aspects. [1]: A transfer method for transferring a plurality of microstructures provided on a substrate to another substrate by laser irradiation, the transfer method including a transfer step of irradiating a first microstructure with a laser through the substrate and transferring the first microstructure to the other substrate, and an additional irradiation step of irradiating the transferred first microstructure with a laser at least once. [2]: The transfer method of [1] above, in which, in the additional irradiation step, a second microstructure remaining on the substrate is also irradiated with a laser, thereby transferring the second microstructure to the other substrate. [3]: The transfer method of [2] above, in which the first microstructure and the second microstructure are arranged adjacent to each other on the substrate. [4]: ​​The transfer method of [2] or [3] above, in which a third microstructure remaining on the substrate, the transferred first microstructure, and the transferred second microstructure are all irradiated with a laser, thereby transferring the third microstructure to the other substrate. [5]: The transfer method of [4] above, in which the second microstructure and the third microstructure are arranged adjacent to each other on the substrate. [6]: The transfer method of [1], [2], [3], [4], or [5] above, in which the substrate and the other substrate move relatively in a fixed direction, and the laser is irradiated while stopped or not stopped. [7]: The transfer method of [1], [2], [3], [4], [5], or [6] above, in which the shape of the irradiated laser is rectangular, and the movement is in the direction of the long side of the rectangle. [8]: The transfer method of [7] above, in which the length of the long side of the rectangular laser on the irradiated surface is three times or more the length of the long side of the microstructure. [9]: The transfer method of [7] or [8] above, in which the length of the long side of the rectangular laser on the irradiated surface is five times or more the length of the long side of the microstructure.

[10] : The transfer method according to [7], [8] or [9], wherein there are a plurality of rectangular lasers, which are arranged at intervals in the direction of the short side of the rectangle.

[11] : The transfer method of [1], [2], [3], [4], [5] or [6], wherein the shape of the irradiated laser is such that there are a plurality of lasers having substantially the same shape as the size of the microstructure on the irradiated surface, and the plurality of lasers are arranged at a distance in the movement direction.

[12] : The transfer method of

[11] , wherein there are a plurality of lasers arranged at a distance from the plurality of lasers in a direction perpendicular to the movement direction and arranged in a matrix.

[13] : The transfer method of [1], [2], [3], [4], [5], [6], [7], [8], [9],

[10] ,

[11] or

[12] , wherein the plurality of microstructures are provided on the substrate via a polymer material.

[14] : In the transfer step, the microstructure provided on the substrate is transferred to the other substrate by a single laser irradiation.

[15] : In the additional irradiation step, the transferred microstructure is irradiated with a laser multiple times. [1], [2], [3], [4], [5], [6], [7], [8], [9],

[10] ,

[11] ,

[12] ,

[13] , or

[14] .

[16] : The transfer method of

[15] above, in which a laser having an energy density lower than the energy density of the laser irradiated onto the microstructure in the transfer step is irradiated multiple times.

[17] : The transfer method of

[15] above or

[16] above, in which the total energy density of the multiple laser irradiations is higher than the energy density of the laser irradiated onto the microstructure in the transfer step.

[18] : The transfer method of [1], [2], [3], [4], [5], [6], [7], [8], [9],

[10] ,

[11] ,

[12] ,

[13] ,

[14] ,

[15] ,

[16] or

[17] above, in which the energy density of the laser irradiated onto the transferred microstructure in the additional irradiation step is lower than the energy density of the laser irradiated onto the microstructure in the transfer step.

[19] : A transfer method according to [1], [2], [3], [4], [5], [6], [7], [8], [9],

[10] ,

[11] ,

[12] ,

[13] ,

[14] ,

[15] ,

[16] ,

[17] or

[18] , in which a plurality of microstructures provided on the substrate and the other substrate are spaced apart.

[20] : The laser irradiated to the microstructure is shaped by passing through an opening in a photomask, and the transmittance of the opening through which the laser irradiated to the transferred microstructure passes in the additional irradiation process is smaller than the transmittance of the opening through which the laser irradiated to the microstructure provided on the substrate passes in the transfer process. [1], [2], [3], [4], [5], [6], [7], [8], [9],

[10] ,

[11] ,

[12] ,

[13] ,

[14] ,

[15] ,

[16] ,

[17] ,

[18] or

[19] .

[21] : The transfer method according to [1], [2], [3], [4], [5], [6], [7], [8], [9],

[10] ,

[11] ,

[12] ,

[13] ,

[14] ,

[15] ,

[16] ,

[17] ,

[18] ,

[19] or

[20] , wherein in the transfer step, the substrate and the other substrate are irradiated with a laser while they are in contact with each other, and in the additional irradiation step, the substrate and the other substrate are separated to form a space between them and irradiate with a laser.

[22] : The transfer method according to

[21] , wherein in the additional irradiation step, oxygen gas is supplied to the space between the substrate and the other substrate.

[0098] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A method for transferring multiple microstructures provided on a substrate to another substrate by laser irradiation, comprising: a transfer step of irradiating a laser through the substrate toward a first microstructure and transferring the first microstructure to the other substrate; and an additional irradiation step of irradiating the transferred first microstructure with a laser at least once.

2. A transfer method according to claim 1, wherein in said additional irradiation step, a second microstructure remaining on said base material is also irradiated with a laser, and said second microstructure is transferred to said other base material.

3. The transfer method according to claim 2, wherein the first microstructure and the second microstructure are disposed adjacent to each other on the base material.

4. A transfer method as described in claim 2 or 3, further comprising irradiating a laser to a third microstructure remaining on the substrate, the transferred first microstructure, and the transferred second microstructure together, thereby transferring the third microstructure to the other substrate.

5. The transfer method according to claim 4, wherein the second microstructure and the third microstructure are disposed adjacent to each other on the base material.

6. A transfer method according to claim 1, wherein the base material and the other base material are moved relatively in a fixed direction, and the laser is irradiated while the base material and the other base material are stationary or non-stationary.

7. A transfer method according to claim 6, wherein the shape of the irradiated laser is rectangular, and the movement is in the direction of the longer side of the rectangle.

8. A transfer method according to claim 7, wherein the length of the long side of said rectangular laser on the irradiation surface is three times or more the length of the long side of said minute structure.

9. A transfer method according to claim 7, wherein the length of the long side of said rectangular laser on the irradiation surface is 5 times or more the length of the long side of said minute structure.

10. A transfer method according to any one of claims 7 to 9, wherein there are a plurality of said rectangular lasers, which are arranged at intervals in the direction of the short side of the rectangle.

11. A transfer method as described in claim 6, wherein the shape of the irradiated laser is such that there are multiple lasers on the irradiated surface having a shape approximately the same as the size of the microstructure, and the multiple lasers are arranged at a distance in the movement direction.

12. A transfer method according to claim 11, wherein a further plurality of lasers are provided in a direction perpendicular to the direction of movement and spaced apart from the plurality of lasers, and are arranged in a matrix.

13. The transfer method according to claim 1, wherein the plurality of minute structures are provided on the base material via a polymer material.

14. A transfer method according to claim 1, wherein in the transfer step, the minute structure provided on the base material is transferred to the other base material by a single laser irradiation.

15. The transfer method according to claim 1, wherein in said additional irradiation step, the transferred microstructure is irradiated with a laser a plurality of times.

16. A transfer method according to claim 15, wherein the minute structure is irradiated multiple times with a laser having an energy density smaller than the energy density of the laser irradiated in said transfer step.

17. A transfer method according to claim 16, wherein the total energy density of the laser irradiated a plurality of times is greater than the energy density of the laser irradiated onto the microstructure in the transfer step.

18. A transfer method according to claim 1, wherein the energy density of the laser irradiated to the transferred microstructure in said additional irradiation step is smaller than the energy density of the laser irradiated to the microstructure in said transfer step.

19. The transfer method according to claim 1, wherein the plurality of microstructures provided on the base material and the other base material are spaced apart from each other.

20. A transfer method as described in claim 1, wherein the laser irradiated to the microstructure is shaped by passing through an opening in a photomask, and the transmittance of the opening through which the laser irradiated to the transferred microstructure passes in the additional irradiation process is smaller than the transmittance of the opening through which the laser irradiated to the microstructure provided on the substrate passes in the transfer process.

21. A transfer method as described in claim 1, wherein in the transfer step, a laser is irradiated while the base material and the other base material are in contact with each other, and in the additional irradiation step, a laser is irradiated while the base material and the other base material are separated to form a space between the base material and the other base material.

22. The transfer method according to claim 21, wherein in said additional irradiation step, oxygen gas is supplied to the space between said base material and said another base material.

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