Lee Jae method

Abstract

The present invention is a transfer method for transferring a plurality of microstructures installed on a substrate by laser irradiation, wherein at least the space between adjacent microstructures is filled with a polymer material, and the method comprises a first laser irradiation process in which a laser is irradiated through the substrate toward the microstructures, and a second laser irradiation process in which a laser is irradiated through the substrate toward the polymer material, wherein in the first laser irradiation process, the laser toward the microstructures is irradiated to an area corresponding to the microstructures. By doing so, chipping or cracking of the microstructures can be suppressed when transferring the microstructures from the substrate.

Description

Technology Field

[0001] The present invention relates to a method for disposing of materials. Background Technology

[0002] Recently, along with the miniaturization of semiconductor devices, microstructure transfer technology using adhesive resins is attracting attention as a means of assembling electrical and electronic application products using semiconductor devices. In particular, there has been active development of technology to manufacture LED displays for applications such as signage, TVs, medical devices, automotive devices, and smartphones by transferring a large number of mini LEDs (LED devices with a side length of 100 µm or more to several hundred µm) or micro LEDs (LED devices with a side length of 100 µm or less, and furthermore, 50 µm or less) at once.

[0003] To date, methods for transferring microstructures such as micro LEDs using a silicone adhesive cured material as a donor substrate or transfer stamp material, and methods for mounting them on a circuit board have been developed (e.g., Patent Document 1).

[0004] In addition, a technology has been proposed that can transfer semiconductor chips with high precision by mitigating the shock during transfer (e.g., Patent Document 2). Prior art literature

[0005] Japanese Patent Publication No. 2021-34610 and Japanese Patent Publication No. 2019-67892 The problem to be solved

[0006] However, to improve the yield of this material, it is important to suppress the occurrence of chipping or cracking in the microstructures during peeling from a substrate or other material.

[0007] The present invention is made to solve the above problem and aims to provide a material removal method capable of suppressing chipping or cracking in a microstructure when removing the microstructure from a substrate. means of solving the problem

[0008] To solve the above problem, the present invention provides a method for separating a plurality of microstructures installed on a substrate from the substrate by laser irradiation, wherein

[0009] At least the spaces between adjacent microstructures are filled with a polymer material, and

[0010] A first laser irradiation process of irradiating a laser through the substrate toward the above microstructure, and,

[0011] It has a second laser irradiation process of irradiating a laser toward the polymer material by passing the substrate, and

[0012] In the first laser irradiation process, a laser directed toward the microstructure is irradiated onto an area corresponding to the microstructure, thereby providing a method for disassembling materials.

[0013] With this method of transferring, the microstructures can be transferred from the substrate while suppressing chipping or cracking in the microstructures by performing a two-stage irradiation process, which involves a first laser irradiation process in which a laser is irradiated onto the microstructures and a second laser irradiation process in which a laser is irradiated onto the polymer material, while the spaces between the microstructures are filled with a polymer material.

[0014] For example, it is preferable to perform the second laser irradiation process after the first laser irradiation process.

[0015] By performing a second laser irradiation process after a first laser irradiation process, for example, the polymer material can be peeled off in the second laser irradiation process without peeling off in the first laser irradiation process. By doing so, the microstructure can be removed from the substrate while more reliably suppressing the occurrence of chipping or cracks in the microstructure.

[0016] In the above second laser irradiation process, a laser may be irradiated toward the polymer material and the microstructure.

[0017] In the second laser irradiation process, the laser may be irradiated onto the polymer material, but it does not matter whether the laser is irradiated onto the microstructure. In addition, in the second laser irradiation process, the laser may be irradiated onto the entire surface of the substrate.

[0018] For example, the first laser irradiation process can be performed at an energy density that sufficiently ablates the polymer material.

[0019] For example, laser irradiation in the first laser irradiation process can be performed at a high energy density that sufficiently ablates the polymer material.

[0020] For example, the plurality of microstructures are installed on the substrate with GaN interposed therein, and

[0021] The above first laser irradiation process can be performed at an energy density that thermally decomposes GaN.

[0022] With such a first laser irradiation process, a microstructure installed on a substrate with GaN interposed therein can be reliably peeled off from the substrate.

[0023] In addition, for example, the second laser irradiation process can be performed at an energy density lower than that at which the polymer material is sufficiently ablated.

[0024] The second laser irradiation process may be performed at an energy density below which the polymer material is sufficiently ablated.

[0025] For example, the second laser irradiation process can be performed at an energy density that vaporizes the polymer material.

[0026] By performing the above-mentioned second laser irradiation process, the polymer material can be vaporized.

[0027] It is preferable to perform the above second laser irradiation process at an energy density capable of suppressing the generation of carbon-based debris derived from the polymer material.

[0028] It is desirable to perform the second laser irradiation process while suppressing the generation of carbon-based debris in this way.

[0029] For example, the laser irradiation in the first laser irradiation process and the second laser irradiation process may be irradiated by an excimer laser with a wavelength of 248 nm, and

[0030] The energy density of the laser irradiation in the first laser irradiation process above can be 700 mJ / cm² or more, and

[0031] The energy density of the laser irradiation in the above second laser irradiation process can be 30 to 500 mJ / cm².

[0032] The wavelength and energy density of the laser can be set as, for example, as above.

[0033] The above second laser irradiation process may be performed multiple times.

[0034] The second laser irradiation process may be performed at least once, or multiple times.

[0035] For example, the substrate on which the plurality of microstructures are installed may be coated with a polymer material to cover the plurality of microstructures.

[0036] A film of polymer material may be formed to cover multiple microstructures. Effects of the invention

[0037] As described above, the transfer method of the present invention allows for the transfer of a microstructure from a substrate while suppressing chipping or cracking in the microstructure. Brief explanation of the drawing

[0038] FIG. 1 is a schematic cross-sectional view showing a composite material to be irradiated by a laser in one example of the method of the present invention. FIG. 2 is a schematic plan view of the composite of FIG. 1 seen from the substrate side. FIG. 3 is a schematic cross-sectional view illustrating a first laser irradiation process in an example of the material removal method of the present invention. FIG. 4 is a schematic cross-sectional view illustrating a second laser irradiation process in an example of the material removal method of the present invention. Figure 5 is an optical microscope image of Example 1. Figure 6 is an optical microscope image of a comparative example. Specific details for implementing the invention

[0039] As mentioned above, there was a need to develop a material removal method capable of suppressing chipping or cracking in the microstructure during material removal from the substrate.

[0040] The inventors, after repeatedly examining the above problem, discovered that by performing a two-stage irradiation process in which a laser is irradiated onto a microstructure and a second laser irradiation process is irradiated onto a polymer material while the space between the microstructures is filled with a polymer material, it is possible to remove the microstructure from the substrate while suppressing chipping or cracking in the microstructure, and thus completed the present invention.

[0041] That is, the present invention is a method for separating a plurality of microstructures installed on a substrate from the substrate by laser irradiation, wherein

[0042] At least the spaces between adjacent microstructures are filled with a polymer material, and

[0043] A first laser irradiation process of irradiating a laser through the substrate toward the above microstructure, and,

[0044] It has a second laser irradiation process of irradiating a laser toward the polymer material by passing the substrate, and

[0045] In the first laser irradiation process, the laser directed toward the microstructure is irradiated onto an area corresponding to the microstructure, which is a different method.

[0046] The present invention will be described in detail below, but the invention is not limited to these.

[0047] [Laser Irradiation Target]

[0048] First, the laser irradiation target in an example of the material disassembly method of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic cross-sectional view showing a composite that is the laser irradiation target in an example of the material disassembly method of the present invention. FIG. 2 is a schematic plan view of the composite of FIG. 1 seen from the substrate side. However, the laser irradiation target in the material disassembly method of the present invention is not limited to the composite shown in FIGS. 1 and 2.

[0049] The composite (10) shown in FIGS. 1 and 2 comprises a substrate (1) and a plurality (in this example, four) microstructures (2) installed on the substrate (1). In addition, the composite (10) comprises a polymer material (3). The polymer material (3) includes a portion (31) that fills the space between at least adjacent microstructures (2). That is, the space between at least adjacent microstructures (2) is filled with the polymer material (3).

[0050] Such a composite (10) can be obtained, for example, by a process of forming a plurality of microstructures (2) on a substrate (1) and a process of filling at least the space between adjacent microstructures (2) with a polymer material (3).

[0051] As shown in FIGS. 1 and 2, the polymer material (3) may additionally include a portion (32) covering the microstructure (2) and / or a portion (33) covering the outside of the microstructure (2). That is, a substrate (1) on which a plurality of microstructures (2) are installed may be coated with the polymer material (3) to cover the plurality of microstructures (2). However, in the laser irradiation target of the material disassembly method of the present invention, the polymer material (3) may include at least a portion (31) filling between adjacent microstructures (2), and may not include a portion (32) covering the microstructure (2) and a portion (33) covering the outside of the microstructure (2). From the perspective of mitigating impact on the microstructure (2), it is preferable to install the polymer material (3) not only in the portion (31) filling between adjacent microstructures (2) but also in the portion (33) covering the outside of the microstructure (2). Furthermore, by installing a polymer material (3) on the portion (32) covering the microstructure (2), the impact on the microstructure (2) can be further mitigated. If the polymer material (3) installed on the portion (32) covering the microstructure (2) is unnecessary for the final product, it can be removed by cleaning or polishing, for example, in a subsequent process after the material removal process.

[0052] When the microstructure (2) is rectangular, it is preferable that the polymer material (3) be placed on all of its outer periphery, that is, on the outer sides of all four sides. However, even if the polymer material (3) is placed on only a part of the outer periphery of the microstructure (2), for example, on the outer side of one side of the rectangular microstructure (2), shock mitigation to the microstructure (2) can be expected compared to the case where no polymer material is placed at all. Also, when the polymer material (3) is placed on the outer sides of two opposing sides, shock mitigation to the microstructure (2) can be expected compared to the case where the polymer material (3) is placed on the outer side of only one side.

[0053] The material of the substrate (1) is not particularly limited as long as it can pass through the first laser irradiation process and the second laser irradiation process described below to irradiate the microstructure (2) and / or polymer material (3) with a laser. As the substrate (1), for example, an inorganic transparent substrate such as a sapphire substrate, a GaAs substrate (gallium arsenide substrate), a Si substrate, a SiC substrate, or a quartz substrate can be suitably used. In addition, an organic transparent substrate that is resistant to laser irradiation may be used.

[0054] The thickness of the substrate (1) can be, for example, 0.001 mm or more and 3 mm or less, but is not specifically limited. Also, it may be a rigid substrate or a flexible substrate. The shape of the substrate (1) is, for example, typically a square or a circular shape, but it may be an elliptical shape, a polygonal shape other than a square, a shape in which some of the sides of a polygon are replaced with curves, etc., or a long tape shape. If necessary, an orientation flat or notch is installed on the outer edge of the substrate to make it easy to handle and easy to adjust the position.

[0055] The microstructure (2) is not particularly limited and may be, for example, an LED chip such as a micro LED or mini LED, a semiconductor chip or other electronic component.

[0056] Generally, the planar shape of the microstructure (2) is square, but there are no particular restrictions, and it may be circular, elliptical, polygonal other than square, or a shape in which some of the sides of the polygon are replaced with curves.

[0057] When the shape of the microstructure (2) is square, the upper limit of one side can be, for example, 2.5 mm. According to the material transfer method of the present invention, although the detailed reasons will be explained below, for example, even a microstructure (2) with a square of 1 mm can be transferred without causing chipping or cracks. The lower limit of one side of the microstructure (2) is not particularly limited, but for example, it can be 0.001 mm. It is preferable that one side of the microstructure (2) be 0.005 mm or more and 2 mm or less. Of course, the present invention can also be applied to microstructures having one side greater than 2.5 mm or less than 0.001 mm. The thickness of the microstructure is not particularly limited, but generally it is 200 μm or less, and it may be 100 μm or less or 50 μm or less. In particular, when the thickness is 50㎛ or less, even small chipping occurring in the microstructure is highly likely to lead to fatal failure in subsequent processes, allowing the material transfer method of the present invention to be effectively applied. Furthermore, this is significant when the thickness is 30㎛ or less. Although the lower limit of thickness is decreasing with the advancement of technology, it is about 1㎛.

[0058] The constituent material of the microstructure (2) is not particularly limited, but for example, the surface of the microstructure (2) on the substrate (1) side may include, for example, gallium nitride (GaN), gallium phosphide (GaP), or indium phosphide (InP). Typically, a plurality of microstructures (2) are installed on the substrate (1) by interposing an inorganic material such as GaN (21). More specifically, it may be an LED chip manufactured on an epitaxial substrate such as a sapphire substrate. Of course, it may also be a microstructure installed on the aforementioned various inorganic transparent substrates or organic transparent substrates by interposing an adhesive, etc.

[0059] Depending on the size of the microstructures or the substrate, generally, tens of thousands to hundreds of thousands of microstructures are installed on the substrate in a matrix. Adjacent microstructures are arranged side by side with a space between them. In this space, there are no microstructures, and the substrate is exposed; this is sometimes referred to as a "street." The width of the street is often determined by the size of the LED chip or the type of dicing. In the case of micro LED chips or chemical dicing, the street width is often small, generally around a few micrometers (1 to 10 micrometers). In the case of mini LEDs or mechanical dicing, the street width tends to be slightly larger, generally around tens of micrometers (10 to 100 micrometers).

[0060] The polymer material (3) is not particularly limited, but may be, for example, a resin of a material selected from the group consisting of polyimide, silicone, polystyrene, and acrylic resin, a composition containing such a material, or a cured product thereof. In terms of mitigating impact on the microstructure (2), it is preferable to use a material having a certain degree of elasticity, such as a rubbery material. Examples of silicones include straight silicones such as dimethyl silicone and methylphenyl silicone, modified silicones such as acrylic modified silicone and methacrylate modified silicone, and combinations thereof. These may be of any type among side chain type, single end type, and double end type.

[0061] Polymer materials can be filled by applying a resin, for example, in a liquid form. These application methods can be applied using spin coaters, dispensers, etc. Application is easy if the material possesses sufficient fluidity to fill between adjacent microstructures during application and, if necessary, allows the fluidity to be reduced after application. Therefore, thermoplastic materials, thermosetting materials, photocurable materials, and solvents obtained by dissolving these materials in a solvent are useful. In particular, if the material is a solvent-soluble resin such as a thermoplastic resin or a solvent obtained by dissolving such resin, the polymer compound after dissolution can be easily removed by the solvent. Furthermore, the filling of the polymer material between adjacent microstructures may be performed in a way that prevents the formation of bubbles or voids, or it may be performed in a way that leaves voids on the substrate side. From the perspective of mitigating impact on the microstructures, it is acceptable for more than half of the thickness of the microstructures to be filled. Even when filling to prevent the formation of bubbles, the incorporation of bubbles that are difficult to avoid during the manufacturing process is permitted.

[0062] In addition, when a thermosetting material or a photocurable material is used as the polymer material (3) and the thermosetting material or photocurable material is in a state where it is firmly hardened after removal, it may be difficult to remove the polymer material (3) from the microstructure (2) after removal. In such cases, a curable material that becomes a rubbery material after curing may be used, or the curable material may be cured to a B-stage phase so as to lower the reaction rate, for example, or the flexibility of the cured material may be increased by including a rubber component in the composition of the curable material.

[0063] In addition, photocurable materials whose adhesive strength decreases upon light irradiation may also be used. Photocurable materials whose adhesive strength (tackiness) decreases upon UV irradiation are widely used as dicing tapes, and typically contain a base resin such as a (meth)acrylic copolymer, a photocuring component such as a polyfunctional (meth)acrylate, and a photoinitiator such as a photoradical generator. In this case, it is preferable to use a photoinitiator that has sufficiently low absorption of the wavelength of the laser used in the disassembly method.

[0064] There are no particular restrictions on the receiving substrate, which is the transfer site for the microstructure (2), but for example, inorganic transparent substrates such as sapphire substrate, GaAs substrate (gallium arsenide substrate), Si substrate, SiC substrate, and quartz substrate may be suitably used. In the process following the transfer method of the present invention, if there is no laser irradiation passing through the receiving substrate, it may be an opaque substrate. Likewise, in the process following the receiving substrate, if the receiving substrate is not exposed to excessive heating or excessive chemical treatment, an organic substrate may be used. The shape of the receiving substrate is typically, for example, a square or a circular shape, but it may be an elliptical shape, a polygonal shape other than a square, a shape in which some of the sides of a polygon are replaced with curves, or a long tape shape. If necessary, an orientation flat or notch is installed on the outer edge of the substrate to make it easier to handle and easier to adjust the position.

[0065] Additionally, on the surface of the receiving substrate (the transfer surface) on which the microstructure (2) is transferred, for example, an adhesive layer that temporarily or permanently maintains the transferred microstructure may be partially or on the entire surface. Here, when the microstructure (2) and the polymer material (3) are transferred together, the microstructure (2) can be maintained on the receiving substrate by the polymer material (3).

[0066] In the present invention, for example, a laser can be irradiated using a laminate obtained by applying a polymer material onto a substrate having a plurality of microstructures and contacting a receiving substrate to the side on which the polymer material is installed. If necessary, a solvent drying process may be installed after application. Likewise, if necessary, a curing process may be installed before or after contact with the receiving substrate. Furthermore, the laser may be irradiated in a separated state, i.e., a non-contact state, rather than in a state where the receiving substrate is in contact. When using a laminate in which the receiving substrate is in contact, it is preferable that the substrate and the receiving substrate have the same shape.

[0067] In addition, a polymer material can be applied to a receiving substrate, and the applied polymer material can be tightly pressed into a plurality of microstructures installed on the substrate to fill the spaces between adjacent microstructures. In this case, if necessary, the fluidity of the polymer material can be reduced after filling rather than after application.

[0068] [1st Laser Irradiation Process]

[0069] In the first laser irradiation process of the material disassembly method of the present invention, for example, as shown in FIG. 3, a laser L1 is irradiated by passing through the substrate (1) toward the microstructure (2).

[0070] Also, in the first laser irradiation process of the method for disassembling materials according to the present invention, the laser L1 directed toward the microstructure (2) is irradiated onto the region (12) corresponding to the microstructure (2).

[0071] Here, the region (12) corresponding to the microstructure (2) may include only the microstructure (2), or, as shown in FIG. 3, may include the microstructure (2) and a portion (34) of the polymer material (3) adjacent to the microstructure (2). Additionally, as long as it is within a range where peeling from the substrate (1) is possible by the second laser irradiation process, it may be an area further inside than the outer edge portion of the microstructure (2). Accordingly, the area of ​​the region corresponding to the microstructure (2) is preferably about 90 to 120% of the area of ​​the microstructure (2), more preferably about 95 to 110%, and particularly preferably 98 to 105%.

[0072] In addition, in the first laser irradiation process, irradiation of the region (12) corresponding to the microstructure (2) does not necessarily have to be performed in a single irradiation. For example, the impact on the microstructure (2) can be mitigated by performing multiple irradiations with different irradiation areas. Also, the impact on the microstructure (2) can be mitigated and the occurrence of foreign matter reduced by performing multiple irradiations with overlapping irradiation areas at an energy density that is insufficiently weak to peel the microstructure (2) from the substrate (1). Furthermore, the entire microstructure may be irradiated after irradiating the inner region rather than the outer edge of the microstructure (2).

[0073] In the first laser irradiation process of this example, by irradiating with laser L1, the portion (31) filling between adjacent microstructures (2) among the polymer material (3) can remain on the substrate (1) (without being peeled off), and the microstructures (2) can be peeled off from the substrate (1). Due to the presence of the portion (31) of the polymer material (3), the microstructures (2) can be maintained in a state where they are not separated from the substrate (1).

[0074] The irradiation conditions of laser L1 in the first laser irradiation process will be described later.

[0075] [2nd Laser Irradiation Process]

[0076] In the second laser irradiation process, for example as shown in FIG. 4, a laser L2 is irradiated by passing through the substrate (1) toward the polymer material (3).

[0077] In the second laser irradiation process, the laser L2 may be irradiated toward the polymer material (3), but as shown in FIG. 4, the laser L2 may also be irradiated toward the microstructure (2). Furthermore, the laser L2 may be irradiated toward a plurality of microstructures (2), or the laser L2 may be irradiated toward the entire surface of the composite (10). Also, when the surface area of ​​the composite is large, a high-power laser oscillator is required, so it is desirable to shape the laser in a linear or rectangular shape so that the irradiation area does not become excessively large.

[0078] In the second laser irradiation process of this example, by irradiating with laser L2, the portion (31) filling between adjacent microstructures (2) among the polymer material (3) can be peeled off from the substrate (1).

[0079] Typically, a second laser irradiation process is performed after the first laser irradiation process. As described above, after the first laser irradiation process, the microstructure (2) can be maintained in a state where it is peeled off from the substrate (1) but not separated from the substrate (1).

[0080] In the present invention, the minimum energy density A required to peel off a microstructure (2) from a substrate (1) is greater than the minimum energy density B required to peel off a polymer material (3) from a substrate (1). In this case, if the transfer process is performed uniformly at the minimum energy density A, the impact on the microstructure (2) is likely to increase due to the magnitude of the energy density, and it is likely to cause chipping or cracking in the microstructure (2). In the present invention, even if a laser is irradiated onto the microstructure at the minimum energy density A, which is prone to increasing the impact on the microstructure (2), or at an energy density greater than that, the impact is mitigated by the presence of the polymer material (3), so that chipping or cracking in the microstructure (2) can be suppressed. Therefore, it is possible to increase the energy density and improve the transfer success rate.

[0081] In addition, even if a laser with a minimum energy density of less than A is irradiated onto the microstructure (2) in the first laser irradiation process, there is an advantage in that material can be removed by irradiating the laser to include the microstructure in the second laser irradiation process. Therefore, the impact caused by laser irradiation on the microstructure can be mitigated. In this way, even if the detachment of the microstructure (2) from the substrate (1) in the first laser irradiation process is not complete, or if the detached microstructure (2) is re-attached to the substrate (1) due to a subsequent temperature drop, material can be removed by the second laser irradiation process.

[0082] The second laser irradiation process may be performed multiple times as needed. Additionally, after performing the second laser irradiation process once to separate one microstructure (2) from the substrate (1), the first laser irradiation process may be performed on another microstructure (2).

[0083] Hereinafter, preferred embodiments and specific examples of the irradiation conditions of lasers L1 and L2 in the first laser irradiation process and the second laser irradiation process will be described.

[0084] The wavelengths of lasers L1 and L2 in the first laser irradiation process and the second laser irradiation process can be appropriately set by considering the material and polymer material (3) constituting the microstructure (2). For example, they can be a wavelength 248 nm excimer laser, a wavelength 266 nm excimer laser, a wavelength 193 nm excimer laser, or a wavelength 351 nm excimer laser, but are not particularly limited.

[0085] For example, the first laser irradiation process can be performed at an energy density (e.g., 700 mJ / cm² or more and 2000 mJ / cm² or less) such that the polymer material (3) is sufficiently ablated.

[0086] Here, ablation is generally a phenomenon in which constituent materials of a surface are explosively ejected along with the generation of plasma when laser light is irradiated onto the surface of a solid or liquid. Generally, when a polymer material is ablated, the polymer material undergoes thermal decomposition and photodecomposition. Also, when a polymer material (3) is ablated, some of the polymer material may become carbon-based debris in the form of soot.

[0087] When the polymer material (3) is polyimide, for example, it is preferable to set the energy density in the first laser irradiation process to 40 mJ / cm² or more and 400 mJ / cm² or less at a wavelength of 248 nm and a pulse width of 20 n seconds, and more preferable to set it to 80 mJ / cm² or more and 300 mJ / cm² or less. When the polymer material (3) is silicon, for example, it is preferable to set the energy density in the first laser irradiation process to 100 mJ / cm² or more and 500 mJ / cm² or less at a wavelength of 248 nm and a pulse width of 20 n seconds, and more preferable to set it to 200 mJ / cm² or more and 400 mJ / cm² or less. When the polymer material (3) is an acrylic resin, for example, it is preferable to have an energy density of 40 mJ / cm² or more and 700 mJ / cm² or less in the first laser irradiation process at a wavelength of 248 nm and a pulse width of 20 n seconds, and more preferable to have an energy density of 80 mJ / cm² or more and 400 mJ / cm² or less.

[0088] When a plurality of microstructures (2) are installed on a substrate (1) with GaN (21) interposed therein, for example, the first laser irradiation process can be performed at an energy density that thermally decomposes GaN (for example, 0.8 J / cm² or more and 2 J / cm² or less at a wavelength of 248 nm and a pulse width of 20 n seconds).

[0089] With such a first laser irradiation process, a microstructure (2) installed on a substrate (1) with GaN (21) interposed therein can be reliably peeled off from the substrate (1).

[0090] The second laser irradiation process can be performed, for example, at an energy density less than that which sufficiently ablates the polymer material (3). That is, the energy density of the laser L2 in the second laser irradiation process can be made smaller than the energy density of the laser L1 in the first laser irradiation process. In order to minimize the effect on the area installed in the microstructure (2), it is desirable to make the energy density in the second laser irradiation process sufficiently smaller than the energy density in the first laser irradiation process. It is desirable to have a difference of 100 mJ / cm² or more with a wavelength of 248 nm and a pulse width of 20 n seconds, more desirable to have a difference of 300 mJ / cm² or more, and particularly desirable to have a difference of 500 mJ / cm² or more. The upper limit of the difference in energy density is not particularly limited, but, for example, can be 1200 mJ / cm². In addition, "energy density below which the polymer material is sufficiently ablated" means, in other words, that it is lower than the energy density at which the microstructure can be transferred. By performing irradiation with such sufficiently weak energy density in multiple stages, it is possible to transfer the material while suppressing the generation of carbon-based debris. Although performing irradiation with a weaker energy density and a greater number of times can suppress the generation of carbon-based debris, from the perspective of improving throughput, it is desirable to have the number of irradiations about 2 to 20 times, and it is more desirable to have them about 2 to 10 times.

[0091] Meanwhile, in cases where the generation of carbon-based debris is permitted or where a polymer material is used that is unlikely to generate carbon-based debris, irradiation may be performed at an energy density at which the polymer material is sufficiently ablated, in other words, at an energy density greater than or equal to the minimum energy density B mentioned above.

[0092] For example, the second laser irradiation process can be performed at an energy density that vaporizes the polymer material (3).

[0093] By performing a second laser irradiation process like this, the polymer material (3) can be vaporized.

[0094] It is preferable to perform the second laser irradiation process with an energy density that can suppress the occurrence of carbon-based debris originating from the polymer material (3).

[0095] It is preferable to perform the second laser irradiation process while suppressing the generation of carbon-based debris in this manner. In the second laser irradiation process, it is most preferable to use an energy density such that the generation of debris is zero (e.g., 0.08 J / cm² or less). On the other hand, from the perspective of the material transfer success rate, the energy density may be increased so that the amount of debris generated is 10% or less compared to the amount of debris generated when the polymer material (3) is sufficiently ablated.

[0096] As a specific example, the energy density of the laser irradiation in the second laser irradiation process can be, for example, 30 to 500 mJ / cm².

[0097] Specifically, for example, when the polymer material (3) is polyimide and a laser L2 with a wavelength of 193 nm is used, the energy density is preferably 20 mJ / cm² or more, and more preferably 20 to 200 mJ / cm². Likewise, when a laser L2 with a wavelength of 248 nm is used, the energy density is preferably 30 mJ / cm² or more, and more preferably 30 to 500 mJ / cm². When a laser L2 with a wavelength of 266 nm is used, the energy density is preferably 40 mJ / cm² or more, and more preferably 40 to 400 mJ / cm². When a laser L2 with a wavelength of 351 nm is used, the energy density is preferably 80 mJ / cm² or more.

[0098] In addition, when using a laser L2 with a wavelength of 193 nm and the polymer material (3) is polystyrene, it is preferable that the energy density be at least 10 mJ / cm². When using a laser L2 with a wavelength of 193 nm and the polymer material (3) is acrylic resin, it is preferable that the energy density be at least 60 mJ / cm².

[0099] The material transfer method of the present invention may be, for example, one of a Laser Lift-Off (LLO) or Laser Induced Forward Transfer (LIFT). Specific device configurations and operation methods used in the material transfer method of the present invention can be implemented by referring, for example, to International Publication No. 2019 / 244362.

[0100] By using the material disassembly process of the present invention, the impact on the microstructure (3) during the material disassembly process can be mitigated, making it effective for application to fragile and brittle microstructures (3). Examples of fragile and brittle microstructures (3) include red LED chips or LED chips having an uneven surface such as bumps. In the case of a chip with bumps, the bumps are additionally formed on the electrodes, so the difference in unevenness is large, making it prone to breakage. Also, microstructures having MESA regions generally have electrodes formed at both ends of the MESA region, so they have a shape with small but unevenness, making them prone to breakage.

[0101] In addition, compared to micro LED chips (LED devices with a single side of 100 µm or less, or even 50 µm or less), mini LED chips (LED devices with a single side of 100 µm or more to several hundred µm), which are larger in size, often have a problem where the chips break when transferring the chip. Also, as mentioned above, micro LED chips are also prone to breakage if they have an uneven surface. Red LED chips have the drawback of being relatively fragile and prone to breakage because they differ in the group of elements constituting them from blue or green LED chips. For this reason, there was a phenomenon of breakage during the transfer process.

[0102] Also, the thickness of the main body of the microstructure (3) is not particularly limited, but preferably about 3 to 10 μm. The thickness of the electrode is not particularly limited, but preferably about 2 μm or less, and the thickness of the bump is not particularly limited, but preferably about 1 to 10 μm.

[0103] In addition, the polymer material (3) in the present invention is useful as a protective material installed to protect the microstructures (2) from impact during removal when the plurality of microstructures (2) installed on the substrate (1) are removed from the substrate (1) by laser irradiation. This protective material is desirable because it makes it easier to use the microstructures (2) themselves when it is removed after the microstructures (2) are removed.

[0104] In addition, the concept of the present invention can be effectively applied to a material separation method, but it can also be likewise applied to a peeling method. For example, a peeling method for peeling a plurality of microstructures installed on a substrate by laser irradiation can be provided, wherein at least the space between adjacent microstructures is filled with a polymer material, and the method comprises a first laser irradiation process in which a laser is irradiated through the substrate toward the microstructures, and a second laser irradiation process in which a laser is irradiated through the substrate toward the polymer material, wherein in the first laser irradiation process, the laser toward the microstructures is irradiated to an area corresponding to the microstructures. Regarding each component or condition used in the peeling method, the one described above in the material separation method may be used.

[0105] In addition, the polymer material (3) in the present invention is useful as a protective material installed to protect the microstructures (2) from impact during peeling when the plurality of microstructures (2) installed on the substrate (1) are peeled from the substrate (1) by laser irradiation. It is desirable that this protective material be removed after the microstructures (2) are peeled, as this makes it easier to use the microstructures (2) themselves. On the other hand, the protective material may be used temporarily or permanently as a support for the microstructures without removing it after peeling.

[0106] Examples

[0107] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited thereto.

[0108] (Example 1)

[0109] [Preparation of the complex]

[0110] First, a composite having the same structure as the composite (10) described with reference to FIGS. 1 and 2 was prepared. In the prepared composite (10), the substrate (1) is a sapphire substrate with a thickness of 700 μm and a diameter of 4 inches, and a plurality of microstructures (2) are each LED chips with a square of 0.38 mm and are installed on the substrate (1) with GaN (21) interposed therebetween. Additionally, about 50,000 microstructures are arranged on the substrate in a matrix form with a street of 75 μm width between them. The polymer material (3) is polyimide and, as shown in FIGS. 1 and 2, includes a portion (31) that fills between at least adjacent microstructures (2), a portion (32) that covers the microstructures (2), and a portion (32) that covers the outer side of the microstructures (2). Next, a quartz substrate having the same shape as the substrate was prepared as a receiving substrate, and a laminate was obtained by contacting it to the side where the polymer material (3) of the composite was installed and bonding it. The obtained laminate was fixed by adsorption to the stage of the laser irradiation device.

[0111] [1st Laser Irradiation Process]

[0112] In this state, a laser L1 was irradiated from the substrate (1) side of the composite (10) onto a region (12) corresponding to the microstructure (2), as shown in FIG. 3. The laser L1 was an excimer laser with a wavelength of 248 nm and a pulse width of 20 n seconds, and its energy density (irradiation density) was set to 1100 mJ / cm². Through this first laser irradiation process, the microstructure (2) was peeled off from the substrate, but remained in a state where it was not separated from the substrate (1) due to the presence of the polymer material (3).

[0113] [2nd Laser Irradiation Process]

[0114] As shown in FIG. 4, a laser L2 was irradiated onto a microstructure (2) and a polymer material (3). The laser L2 was an excimer laser with a wavelength of 248 nm, and its energy density (irradiation density) was set to 150 mJ / cm². Through this second laser irradiation process, the microstructure (1) was separated from the substrate (1) and transferred to a receiving substrate.

[0115] Approximately 50,000 microstructures on the receiving substrate after the material was examined, and no noticeable cracks or chipping were found in the microstructures (2) caused by the material. An optical microscope image is shown in Fig. 5.

[0116] (Example 2)

[0117] The transfer of microstructures (2) from the composite (10) was performed in the same manner as in Example 1, except that the polymer material (3) was silicon, the laser L2 in the second laser irradiation process was an excimer laser with a wavelength of 248 nm, and the energy density (irradiation density) was 300 mJ / cm². When approximately 50,000 microstructures on the receiving substrate were examined after the transfer, no noticeable cracks or chipping of the microstructures (2) caused by the transfer were found.

[0118] (Example 3)

[0119] The polymer material (3) was made of acrylic resin, the laser L2 in the second laser irradiation process was made of an excimer laser with a wavelength of 248 nm, and the energy density (irradiation density) was set to 200 mJ / cm², except that the process was carried out in the same manner as in Example 1, and the microstructure (2) from the composite (10) was transferred. When approximately 50,000 microstructures on the receiving substrate were examined after the transfer, no noticeable cracks or chipping of the microstructure (2) caused by the transfer were found.

[0120] (Example 4)

[0121] In the second laser irradiation process, the laser L2 was set to an excimer laser with a wavelength of 193 nm, and the energy density (irradiation density) was set to 100 mJ / cm²; otherwise, the microstructure (2) from the composite (10) was transferred in the same manner as in Example 1. After transferring, about 50,000 microstructures on the receiving substrate were examined, and no noticeable cracks or chipping of the microstructure (2) caused by the transfer were found.

[0122] (Example 5)

[0123] The transfer of the microstructure (2) from the composite (10) was performed in the same manner as in Example 1, except that the laser L2 in the second laser irradiation process was an excimer laser with a wavelength of 308 nm and its energy density (irradiation density) was 200 mJ / cm². Upon checking the receiving substrate after the transfer, no cracks or chipping of the microstructure (2) caused by the transfer were found.

[0124] (Example 6)

[0125] The transfer of microstructures (2) from the composite (10) was performed in the same manner as in Example 1, except that the laser L2 in the second laser irradiation process was an excimer laser with a wavelength of 351 nm and its energy density (irradiation density) was 200 mJ / cm². When approximately 50,000 microstructures on the receiving substrate were examined after the transfer, no noticeable cracks or chipping of the microstructures (2) caused by the transfer were found.

[0126] (Comparative Example)

[0127] In the first laser irradiation process, laser L1 was irradiated onto both the microstructure (2) and the polymer material (3), and the microstructure (2) was removed from the composite (10) in the same manner as in Example 1, except that the second laser irradiation process was not performed. After removal, approximately 50,000 microstructures on the receiving substrate were examined, and it was found that cracks had occurred in most of the microstructures (2) due to the removal. An optical microscope photograph is shown in FIG. 6.

[0128] Based on the above results, it was confirmed that the method of transferring the microstructure (2) of the present invention can transfer the microstructure while suppressing the occurrence of cracks or chipping.

[0129] Also, in the substrate (1) after the removal of the materials in Examples 1 to 6, no debris of polymer material (3) remained.

[0130] The present specification includes the following aspects.

[0131] [1] A method for separating a plurality of microstructures installed on a substrate from the substrate by laser irradiation,

[0132] At least the spaces between adjacent microstructures are filled with a polymer material, and

[0133] A first laser irradiation process of irradiating a laser through the substrate toward the above microstructure, and,

[0134] It has a second laser irradiation process of irradiating a laser toward the polymer material by passing the substrate, and

[0135] A method for disassembling materials, wherein in a first laser irradiation process, the laser directed toward the microstructure is irradiated onto an area corresponding to the microstructure.

[0136] [2] The method described in [1], which performs the second laser irradiation process after the first laser irradiation process.

[0137] [3] A method of irradiating a laser toward the polymer material and the microstructure in the second laser irradiation process described in [1] or [2].

[0138] [4] A method of transferring materials described in any one of [1] to [3], wherein the first laser irradiation process is performed at an energy density such that the polymer material is sufficiently ablated.

[0139] [5] The above plurality of microstructures are installed on the substrate with GaN interposed therein, and

[0140] A method of transferring materials described in any one of [1] to [4], wherein the above first laser irradiation process is performed at an energy density that pyrolyzes GaN.

[0141] [6] A method of transferring materials described in any one of [1] to [5], wherein the second laser irradiation process is performed at an energy density less than that which sufficiently ablates the polymer material.

[0142] [7] The second laser irradiation process described in [6] is performed at an energy density that vaporizes the polymer material.

[0143] [8] The second laser irradiation process described in [7] is performed at an energy density that can suppress the occurrence of carbon-based debris from the polymer material.

[0144] [9] The laser irradiation in the first laser irradiation process and the second laser irradiation process is irradiation by an excimer laser with a wavelength of 248 nm, and

[0145] The energy density of the laser irradiation in the first laser irradiation process above is 700 mJ / cm² or more, and

[0146] The energy density of the laser irradiation in the second laser irradiation process described above is 30 to 500 mJ / cm², as described in any one of [1] to [8].

[0147]

[10] A method of transferring materials described in any one of [1] to [9], in which the above second laser irradiation process is performed multiple times.

[0148]

[11] A substrate having a plurality of microstructures is covered by a polymer material to cover the plurality of microstructures. This is a method of disassembly described in any one of [1] to

[10] .

[0149] Furthermore, the present invention is not limited to the above embodiments. The above embodiments are examples, and any configuration substantially identical to the technical concept described in the claims of the present invention and exhibiting similar functional effects is included within the technical scope of the present invention.

Claims

Claim 1 A transfer method for transferring a plurality of microstructures installed on a substrate by laser irradiation, wherein at least the space between adjacent microstructures is filled with a polymer material, and the method comprises a first laser irradiation process of irradiating a laser through the substrate toward the microstructures, and a second laser irradiation process of irradiating a laser through the substrate toward the polymer material, wherein in the first laser irradiation process, the laser toward the microstructures is irradiated to an area corresponding to the microstructures. Claim 2 A method for transferring materials according to claim 1, wherein the second laser irradiation process is performed after the first laser irradiation process. Claim 3 A method of material transfer in which, in the second laser irradiation process, a laser is irradiated toward the polymer material and the microstructure. Claim 4 A method for transferring materials according to claim 1, wherein the first laser irradiation process is performed at an energy density in which the polymer material is sufficiently ablated. Claim 5 A method for transferring materials according to claim 1, wherein the plurality of microstructures are installed on the substrate with GaN interposed therein, and the first laser irradiation process is performed at an energy density that thermally decomposes GaN. Claim 6 A method for transferring materials according to claim 1, wherein the second laser irradiation process is performed at an energy density less than that at which the polymer material is sufficiently ablated. Claim 7 In claim 6, a method of transferring the material by performing the second laser irradiation process at an energy density that vaporizes the polymer material. Claim 8 A method for transferring materials according to claim 7, wherein the second laser irradiation process is performed at an energy density capable of suppressing the generation of carbon-based debris derived from the polymer material. Claim 9 A method for transferring materials according to claim 1, wherein the laser irradiation in the first laser irradiation process and the second laser irradiation process is irradiation by an excimer laser with a wavelength of 248 nm, the energy density of the laser irradiation in the first laser irradiation process is 700 mJ / cm² or more, and the energy density of the laser irradiation in the second laser irradiation process is 30 to 500 mJ / cm². Claim 10 A method for transferring materials according to claim 1, wherein the second laser irradiation process is performed multiple times. Claim 11 In claim 1, the substrate on which the plurality of microstructures are installed is coated with a polymer material to cover the plurality of microstructures.

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