Transfer method, transfer unit, method for manufacturing display device, and method for manufacturing mounting board

Abstract

The present invention provides a transfer method for transferring a structure to a transfer destination, the transfer method comprising: preparing a release plate including a base material, a resin layer provided on the base material and having a transfer laser transmittance of 90% or more, and a structure held on the surface of the resin layer on the opposite side from the base material; causing the transfer laser to be incident on the base material from the surface of the base material on the opposite side from the resin layer; and causing the incident transfer laser to be transmitted through the base material and the resin layer and thermally decompose at least a portion of the resin layer at the interface where the structure and the resin layer are in contact, thereby transferring the structure from the release plate to the transfer destination. This makes it possible to provide a transfer method whereby a structure can be transferred to a transfer destination at high precision.

Description

Transfer method, transfer unit, display device manufacturing method, and mounting substrate manufacturing method

[0001] The present invention relates to a transfer method, a transfer unit, a method for manufacturing a display device, and a method for manufacturing a mounting substrate.

[0002] In recent years, with the miniaturization of semiconductor elements, microstructure transfer (mounting) technology using adhesive resins has attracted attention as a means of assembling electrical and electronic products using semiconductor elements. In particular, there has been active development of technology for manufacturing LED displays for applications such as signage, TVs, medical devices, in-vehicle displays, and smartphones by transferring (mounting) tens of thousands of mini-LEDs (LED elements with short sides of 100 μm or more to several hundred μm) or micro-LEDs (LED elements with short sides of 100 μm or less, or even 50 μm or less) at once.

[0003] To date, methods have been developed for transferring microstructures such as microLEDs onto circuit boards using silicone adhesive cured materials as donor substrates or transfer stamp materials (see, for example, Patent Document 1).

[0004] Furthermore, a technique has been proposed that can transfer semiconductor chips with high precision by mitigating the impact during transfer (for example, Patent Document 2).

[0005] JP 2021-34610 A JP 2019-67892 A

[0006] Kristin M. Charipar et al., "Use of an Elastomeric Donor for LIFT of Metal Foils," Journal of Laser Micro / Nanoengineering, Vol. 13, No. 2, 2018.

[0007] One technique for transferring a structure using a laser is to transfer an object to be transferred by using a laser-induced phenomenon such as laser ablation. Among these techniques, a technique for moving an object to be transferred in the direction of laser irradiation is called LIFT (Laser-Induced Forward Transfer) (see, for example, Non-Patent Document 1). Conversely, a method for returning an object to be transferred in the direction of laser irradiation is called LIBT (Laser-Induced Back Transfer).

[0008] In conventional LIFT, a release plate is used that includes a substrate and a support layer formed on the substrate and holding the structure, and the structure is peeled off (transferred) from the interface between the substrate and the support layer of the release plate by laser ablation. This method allows the structure to be transferred to the transfer destination with a certain degree of accuracy.

[0009] However, with conventional LIFT, subtle variations in the laser irradiation energy density distribution for each pulse and variations in the energy density for each laser shot change the amount of gas generated for each transfer and within the laser-irradiated surface, affecting the direction and speed of the structures popping out. This has limited the improvement of transfer position accuracy.

[0010] The present invention has been made to solve the above problems, and aims to provide a transfer method capable of transferring a structure to a transfer destination with high precision, a transfer unit capable of transferring a structure to a transfer destination with high precision, a manufacturing method for a display device capable of manufacturing a display device in which structures are arranged on a wiring substrate with high precision, and a manufacturing method for a mounting substrate capable of manufacturing a mounting substrate in which structures are arranged on a wiring substrate with high precision.

[0011] In order to solve the above problems, the present invention provides a transfer method for transferring a structure to a transfer destination, the transfer method including: preparing a release plate including a substrate, a resin layer provided on the substrate and having a transfer laser transmittance of 90% or more, and a structure held on the surface of the resin layer opposite the substrate; making the transfer laser incident on the substrate from the surface of the substrate opposite the resin layer; and the incident transfer laser passing through the substrate and the resin layer and thermally decomposing at least a portion of the resin layer at the interface where the structure and the resin layer are in contact, and transferring the structure from the release plate to the transfer destination.

[0012] The transfer method of the present invention can suppress variations in the amount of gas generated from each transfer and within the laser irradiation surface, and can make the direction and speed of the structures projecting uniform, thereby enabling the structures to be transferred to the transfer destination with high accuracy.

[0013] For example, the thermal decomposition of the resin layer at the interface occurs when the transfer laser passes through the substrate and the resin layer, causing the surface of the structure in contact with the resin layer to heat up to a temperature above the thermal decomposition temperature of the resin layer.

[0014] In the transfer method of the present invention, for example, a transfer laser that has passed through the substrate and the resin layer can heat the surface of the structure that comes into contact with the resin layer to a temperature above the thermal decomposition temperature of the resin layer, thereby causing thermal decomposition of the resin layer and allowing the structure to be peeled off from the release plate.

[0015] The thermal decomposition temperature of the constituent material of the surface of the structure in contact with the resin layer is preferably higher than the thermal decomposition temperature of the resin layer.

[0016] If the thermal decomposition temperature of the constituent material of the surface of the structure that is in contact with the resin layer is higher than the thermal decomposition temperature of the resin layer, the structure can be transferred while preventing deterioration.

[0017] It is more preferable that the thermal decomposition temperature of the constituent material of the surface of the structure in contact with the resin layer is higher by 200° C. or more than the thermal decomposition temperature of the resin layer.

[0018] In such a case, deterioration of the structure can be prevented more reliably.

[0019] For example, the resin layer may include dimethylpolysiloxane.

[0020] In the present invention, the constituent material of the resin layer is not particularly limited, but the resin layer may contain, for example, dimethylpolysiloxane.

[0021] For example, the surface of the structure that is in contact with the resin layer may contain gallium nitride.

[0022] In the present invention, the constituent material of the structure is not particularly limited, but for example, the surface of the structure in contact with the resin layer may contain gallium nitride (GaN).

[0023] For example, the resin layer may contain dimethylpolysiloxane, and the surface of the structure that is in contact with the resin layer may contain gallium nitride.

[0024] For example, the resin layer may contain dimethylpolysiloxane, and the surface of the structure in contact with the resin layer may contain gallium nitride.

[0025] Alternatively, the resin layer may contain polyimide, and the surface of the structure that is in contact with the resin layer may contain gallium phosphide.

[0026] The resin layer may contain polyimide, and the surface of the structure in contact with the resin layer may contain gallium phosphide (GaP).

[0027] For example, the transfer laser can be an excimer laser with a wavelength of 248 nm.

[0028] As the transfer laser, for example, an excimer laser having a wavelength of 248 nm can be used.

[0029] The present invention also provides a transfer unit for transferring a structure to a transfer destination, comprising: a light source that oscillates a transfer laser; a release plate including a substrate, a resin layer provided on the substrate and having a transmittance of the transfer laser of 90% or more, and a structure held on the surface of the resin layer opposite the substrate; a holding mechanism configured to hold the transfer destination; an alignment mechanism configured to position the light source and the holding mechanism opposite each other with the release plate sandwiched therebetween; and a controller configured to control the oscillation of the transfer laser by the light source so that the transfer laser is incident on the substrate from the surface of the substrate opposite the resin layer, and thermally decomposes at least a portion of the resin layer at the interface where the structure and the resin layer contact.

[0030] The transfer unit of the present invention can suppress variations in the amount of gas generated for each transfer and within the laser irradiation surface, and can make the direction and speed of the structures projecting uniform, thereby enabling the transfer unit of the present invention to transfer the structures to the transfer destination with high accuracy.

[0031] The transfer unit may, for example, thermally decompose at least a portion of the resin layer at the interface where the structure and the resin layer are in contact, and transfer the structure from the release plate to a transfer destination.

[0032] In the transfer unit of the present invention, for example, at least a part of the resin layer can be thermally decomposed at the interface where the structure and the resin layer are in contact, thereby transferring the structure from the release plate to the transfer destination.

[0033] In the transfer unit, for example, the thermal decomposition of the resin layer at the interface may occur when the transfer laser passes through the substrate and the resin layer, causing the surface of the structure in contact with the resin layer to heat up to a temperature above the thermal decomposition temperature of the resin layer.

[0034] In the transfer unit of the present invention, for example, a transfer laser that passes through the substrate and the resin layer can cause the surface of the structure that contacts the resin layer to generate heat above the thermal decomposition temperature of the resin layer, thereby causing thermal decomposition of the resin layer at the interface and allowing the structure to be peeled off from the release plate.

[0035] The thermal decomposition temperature of the constituent material of the surface of the structure in contact with the resin layer is preferably higher than the thermal decomposition temperature of the resin layer.

[0036] If the thermal decomposition temperature of the constituent material of the surface of the structure that is in contact with the resin layer is higher than the thermal decomposition temperature of the resin layer, the structure can be transferred while preventing deterioration.

[0037] It is more preferable that the thermal decomposition temperature of the constituent material of the surface of the structure in contact with the resin layer is higher by 200° C. or more than the thermal decomposition temperature of the resin layer.

[0038] Such a transfer unit can more reliably prevent deterioration of the structure.

[0039] For example, the resin layer may contain dimethylpolysiloxane.

[0040] In the present invention, the constituent material of the resin layer is not particularly limited, but the resin layer may contain, for example, dimethylpolysiloxane.

[0041] For example, the surface of the structure that is in contact with the resin layer may contain gallium nitride.

[0042] In the present invention, the constituent material of the structure is not particularly limited, but for example, the surface of the structure in contact with the resin layer may contain gallium nitride (GaN).

[0043] For example, the resin layer may contain dimethylpolysiloxane, and the surface of the structure that is in contact with the resin layer may contain gallium nitride.

[0044] For example, the resin layer may contain dimethylpolysiloxane, and the surface of the structure in contact with the resin layer may contain gallium nitride.

[0045] Alternatively, the resin layer may contain polyimide, and the surface of the structure that is in contact with the resin layer may contain gallium phosphide.

[0046] The resin layer may contain polyimide, and the surface of the structure in contact with the resin layer may contain gallium phosphide (GaP).

[0047] For example, the transfer laser can be an excimer laser with a wavelength of 248 nm.

[0048] As the transfer laser, for example, an excimer laser having a wavelength of 248 nm can be used.

[0049] The present invention also provides a method for manufacturing a display device that transfers a structure to a wiring board, the method including: preparing a wiring board; preparing a release plate that includes a substrate, a resin layer that is provided on the substrate and has a transfer laser transmittance of 90% or more, and a structure that is held on the surface of the resin layer opposite the substrate; making the transfer laser incident on the substrate from the surface of the substrate opposite the resin layer; the incident transfer laser passes through the substrate and the resin layer, and thermally decomposes at least a portion of the resin layer at the interface where the structure and the resin layer contact, and transferring the structure from the release plate to the wiring board.

[0050] According to the manufacturing method of the display device of the present invention, it is possible to suppress fluctuations in the amount of gas generated with each transfer and within the laser irradiation surface, and to make the direction and speed of the structures projecting uniform, thereby making it possible to manufacture a display device in which structures are arranged with high precision on the wiring substrate.

[0051] The present invention also provides a method for manufacturing a mounting substrate, in which a structure is transferred to a wiring board, the method comprising: preparing a wiring board; preparing a release plate including a substrate, a resin layer provided on the substrate and having a transfer laser transmittance of 90% or more, and a structure held on a surface of the resin layer opposite the substrate; making the transfer laser incident on the substrate from the surface of the substrate opposite the resin layer; and the incident transfer laser passes through the substrate and the resin layer, thermally decomposing at least a portion of the resin layer at the interface where the structure and the resin layer are in contact, and transferring the structure from the release plate to the wiring board.

[0052] According to the method for manufacturing a mounting substrate of the present invention, it is possible to suppress fluctuations in the amount of gas generated for each transfer and within the laser irradiation surface, and to make the direction and speed of the structures projecting uniform, making it possible to manufacture a mounting substrate in which structures are arranged with high precision on a wiring board.

[0053] As described above, the transfer method of the present invention makes it possible to transfer a structure to a transfer destination with high accuracy.

[0054] Furthermore, the transfer unit of the present invention can transfer the structure to the transfer destination with high precision.

[0055] Furthermore, the manufacturing method of the display device of the present invention makes it possible to manufacture a display device in which structures are arranged on a wiring substrate with high precision.

[0056] Furthermore, the method for manufacturing a mounting board of the present invention makes it possible to manufacture a mounting board in which structures are arranged with high precision on a wiring board.

[0057] 1 is a schematic diagram showing an example of a transfer unit of the present invention; FIG. 2 is a schematic enlarged cross-sectional view of a part of the release plate shown in FIG. 1; FIG. 3 is a schematic enlarged cross-sectional view of a part of an example of a transfer method of the present invention; and FIG. 4 is a schematic cross-sectional view of a part of another example of a transfer method of the present invention.

[0058] As described above, there has been a demand for the development of a transfer method that can transfer a structure to a transfer destination with high accuracy.

[0059] As a result of extensive research into the above-mentioned problems, the inventors have discovered that a release plate including a substrate, a resin layer provided on the substrate and having a transfer laser transmittance of 90% or more, and a structure held on the surface of the resin layer opposite the substrate can be used, and the transfer laser can be incident on the substrate from the surface of the substrate opposite the resin layer, causing the incident transfer laser to thermally decompose at least a portion of the resin layer at the interface where the structure and the resin layer are in contact, thereby transferring the structure from the release plate to the transfer destination, thereby making it possible to transfer the structure to the transfer destination with high accuracy, and have completed the present invention.

[0060] That is, the present invention is a transfer method for transferring a structure to a transfer destination, comprising: preparing a release plate including a substrate, a resin layer provided on the substrate and having a transfer laser transmittance of 90% or more, and a structure held on the surface of the resin layer opposite the substrate; making the transfer laser incident on the substrate from the surface of the substrate opposite the resin layer; and the incident transfer laser passes through the substrate and the resin layer, thermally decomposing at least a portion of the resin layer at the interface where the structure and the resin layer are in contact, and transferring the structure from the release plate to the transfer destination.

[0061] The present invention also provides a transfer unit for transferring a structure to a transfer destination, the transfer unit comprising: a light source that oscillates a transfer laser; a release plate including a substrate, a resin layer provided on the substrate and having a transmittance of the transfer laser of 90% or more, and a structure held on the surface of the resin layer opposite the substrate; a holding mechanism configured to hold the transfer destination; an alignment mechanism configured to position the light source and the holding mechanism opposite each other with the release plate sandwiched therebetween; and a controller configured to control the oscillation of the transfer laser by the light source so that the transfer laser is incident on the substrate from the surface of the substrate opposite the resin layer, and thermally decomposes at least a portion of the resin layer at the interface where the structure and the resin layer contact.

[0062] The present invention also provides a method for manufacturing a display device that transfers a structure to a wiring board, the method comprising: preparing a wiring board; preparing a release plate that includes a substrate, a resin layer that is provided on the substrate and has a transfer laser transmittance of 90% or more, and a structure that is held on the surface of the resin layer opposite the substrate; making the transfer laser incident on the substrate from the surface of the substrate opposite the resin layer; and the incident transfer laser passing through the substrate and the resin layer and thermally decomposing at least a portion of the resin layer at the interface where the structure and the resin layer are in contact, and transferring the structure from the release plate to the wiring board.

[0063] The present invention also provides a method for manufacturing a mounting substrate, which transfers a structure to a wiring board, the method including: preparing a wiring board; preparing a release plate including a base material, a resin layer provided on the base material and having a transfer laser transmittance of 90% or more, and a structure held on a surface of the resin layer opposite the base material; making the transfer laser incident on the base material from a surface of the base material opposite the resin layer; and the incident transfer laser passes through the base material and the resin layer, thermally decomposing at least a portion of the resin layer at an interface where the structure and the resin layer are in contact, and transferring the structure from the release plate to the wiring board.

[0064] The present invention will be described in detail below, but the present invention is not limited thereto.

[0065] [Transfer unit] The transfer unit of the present invention is a transfer unit that transfers a structure to a transfer destination, and includes: a light source that oscillates a transfer laser; a release plate that includes a substrate, a resin layer that is provided on the substrate and has a transmittance of 90% or more for the transfer laser, and a structure that is held on the surface of the resin layer opposite the substrate; a holding mechanism that is configured to hold the transfer destination; an alignment mechanism that is configured to make the light source and the holding mechanism face each other with the release plate sandwiched therebetween; and a controller that is configured to control the oscillation of the transfer laser by the light source so that the transfer laser is incident on the substrate from the surface of the substrate opposite the resin layer, and thermally decomposes at least a portion of the resin layer at the interface where the structure and the resin layer contact.

[0066] Examples of the transfer unit according to the present invention will be described below with reference to Figures 1 to 3. However, the transfer unit according to the present invention is not limited to the examples shown in Figures 1 to 3.

[0067] The transfer unit 10 shown in FIG. 1 is a transfer unit that transfers a structure 20 onto a transfer destination 30 .

[0068] The transfer unit 10 shown in FIG. 1 includes a light source 2 , a release plate 1 , a holding mechanism 3 , an alignment mechanism 4 , and a controller 5 .

[0069] The light source 2 is configured to oscillate a transfer laser L. In the example of Fig. 1, the light source 2 includes a laser oscillator 21 that oscillates the transfer laser L and a mirror 22 that changes the orientation of the laser oscillator 21, but is not limited to this configuration. For example, the light source 2 may also include a galvano scanner that includes the mirror 22, a scanner that drives the mirror 22, and a controller that controls the mirror 22 and the scanner.

[0070] The laser oscillator 21 may be one that pulses the transfer laser L or one that continuously oscillates the transfer laser L. The laser oscillator 21 that pulses the transfer laser L is preferable because it can irradiate only appropriate locations with the transfer laser at an appropriate energy density.

[0071] The light source 2 may include, between the laser oscillator 21 and the release plate 1, a shaping optical system that shapes the energy distribution of the transfer laser L and / or a photomask that adjusts the irradiation shape.

[0072] The wavelength of the transfer laser L is not particularly limited as long as it is a wavelength that can thermally decompose at least a portion of the resin layer at the interface between the structure and the resin layer, as will be described in detail below. The transfer laser L can be, for example, an excimer laser (KrF excimer laser) having a wavelength of 248 nm. Other examples include an ArF excimer laser (wavelength 193 nm), a XeCl excimer laser (wavelength 308 nm), and a XeF excimer laser (wavelength 353 nm). From the viewpoints of proven use and ease of availability, a KrF excimer laser is preferred.

[0073] FIG. 2 is a schematic enlarged cross-sectional view of a part of the release plate 1 included in the transfer unit 10 shown in FIG.

[0074] The release plate 1 includes a substrate 11, a resin layer 12 provided on the substrate 11, and structures 20 held on the surface of the resin layer 12 opposite to the substrate 11. In the example of FIG. 1 , the release plate 1 includes a plurality of structures 20.

[0075] The substrate 11 is not particularly limited, but may be made of quartz, for example. The substrate 11 preferably has a transmittance of 90% or more for the transfer laser L. However, as will be described in detail below, the transfer unit 10 of the present invention is not particularly limited as long as it is configured to thermally decompose at least a portion 12A of the resin layer 12 at the interface 13 where the structure 20 and the resin layer 12 are in contact, and the transmittance of the transfer laser L through the substrate 11 is not particularly limited. If the transmittance of the transfer laser L through the substrate 11 is 90% or more, attenuation of the energy of the transfer laser L from the light source 2 in the substrate layer 11 can be suppressed, thereby enabling highly energy-efficient transfer.

[0076] The thickness of the substrate 11 can be, for example, 0.1 mm or more and 1 mm or less, but is not particularly limited.

[0077] The resin layer 12 has a transmittance of 90% or more for the transfer laser L. Here, the transmittance refers to the transmittance when the transfer laser L is incident perpendicularly to the surface of the resin layer 12, in other words, the transmittance in the thickness direction of the resin layer 12. This means that the absorption rate of the transfer laser L in the resin layer 12 is less than 10%, which can effectively suppress ablation of the resin layer 12. The transmittance of the transfer laser L in the resin layer 12 can depend, for example, on the wavelength of the transfer laser L and the material and thickness of the resin layer 12. The upper limit of the transmittance is 100%, but it may be approximately 98% or less from the perspective of easy availability of materials.

[0078] The material of the resin layer 12 is not particularly limited, but the resin layer 12 can include, for example, dimethylpolysiloxane, polyimide, benzocyclobutene resin, or silicone-based resin.

[0079] The thickness of the resin layer 12 is not particularly limited, but can be, for example, 0.005 mm or more and 1 mm or less.

[0080] Although not intended to be limited, the resin layer 12 containing dimethylpolysiloxane and having a thickness of 100 μm or less has a transmittance of 90% or more for a transfer laser L having a wavelength of 248 nm. When a transfer laser having a wavelength other than 248 nm is used, the material contained in the resin layer and the thickness of the resin layer can be selected so that the transmittance for the wavelength of the transfer laser is 90% or more.

[0081] The structure 20 is a transfer target to be transferred to the transfer destination 30. The structure 20 is not particularly limited. For example, the structure 20 may be an LED chip such as a micro LED or a mini LED, or may be a semiconductor chip.

[0082] The constituent material of the structure 20 is not particularly limited, but for example, the surface 20A of the structure 20 in contact with the resin layer 12 can contain gallium nitride (GaN) or gallium phosphide (GaP).

[0083] In the transfer unit 10 shown in FIG. 1, the release plate 1 is held by a holder 41 .

[0084] The holding mechanism 3 is configured to hold the transfer destination 30 .

[0085] The transfer destination 30 is not particularly limited as long as it can receive the structure 20. If the structure 20 is an LED chip, the transfer destination 30 may be a wiring board of a display device. Alternatively, if the structure 20 is a semiconductor chip, the transfer destination 30 may be a wiring board of a mounting board.

[0086] The details of the holding mechanism 3 can be changed as appropriate according to the shape of the transfer destination 30. In the example of Fig. 1, the holding mechanism 3 is a stage on which the transfer destination 30 is placed and held.

[0087] The alignment mechanism 4 is configured to position the light source 2 and the holding mechanism 3 opposite each other with the release plate 1 therebetween. Although not limited thereto, in the example of the transfer unit 10 shown in FIG. 1 , the alignment mechanism 4 includes a holder 41 that holds the release plate 1, a mechanism (not shown) that positions each component of the light source 2, and a mechanism (not shown) that positions the holding mechanism 3.

[0088] The controller 5 is configured to control the oscillation of the transfer laser L by the light source 2. More specifically, the controller 5 is configured to control the oscillation of the transfer laser L by the light source 2 so that the transfer laser L is incident on the surface of the substrate 11 opposite to the resin layer 12 of the substrate 11 and thermally decomposes at least a part 12A of the resin layer 12 at an interface 13 where the structure 20 and the resin layer 12 are in contact, for example, as shown in FIG.

[0089] Other details of the transfer unit 10 will be described later.

[0090] By using such a transfer unit 10 of the present invention, it is possible to carry out the transfer method of the present invention, which will be described in detail below. The detailed reasons for this will be explained in the transfer method below, but by using the transfer unit of the present invention, even if there are subtle variations in the laser irradiation energy density distribution or variations in the energy density between laser shots, it is possible to suppress variations in the amount of gas generated between transfers and within the laser-irradiated surface, and to make the direction and speed of the structures projecting uniform. As a result, the transfer method of the present invention allows the structures to be transferred to the transfer destination with high precision.

[0091] [Transfer Method] A transfer method for transferring a structure to a transfer destination, comprising: preparing a release plate including a substrate, a resin layer provided on the substrate and having a transfer laser transmittance of 90% or more, and a structure held on the surface of the resin layer opposite the substrate; making the transfer laser incident on the substrate from the surface of the substrate opposite the resin layer; and the incident transfer laser passes through the substrate and the resin layer, thermally decomposing at least a portion of the resin layer at the interface where the structure and the resin layer contact, and transferring the structure from the release plate to the transfer destination.

[0092] As an example of the transfer method of the present invention, a transfer method using the transfer unit 10 shown in Figures 1 to 3 will be described below. However, the transfer method of the present invention is not limited to the example described below, and can also be performed using a unit or device other than the transfer unit 10 shown in Figures 1 to 3.

[0093] First, the release plate 1 described above is prepared.

[0094] Next, the transfer laser L is made incident on the surface of the base material 11 of the release plate 1 opposite to the resin layer 12 .

[0095] The transfer laser L can be emitted from the light source 2. For example, the transfer laser L may be emitted from a laser oscillator 21 and passed through a shaping optical system that shapes the energy distribution of the transfer laser L and / or a photomask that adjusts the irradiation shape, and then incident on the substrate 11.

[0096] Next, the incident transfer laser L passes through the substrate 11 and the resin layer 12. As described above, the resin layer 12 has a transfer laser transmittance of 90% or more, and therefore an absorption rate of the transfer laser of less than 10%, making it possible to suppress temperature rise and ablation due to the passage of the laser light.

[0097] The transfer laser L transmitted through the substrate 11 and the resin layer 12 thermally decomposes at least a portion 12A of the resin layer 12 at the interface 13 where the structure 20 and the resin layer 12 are in contact, as shown in FIG.

[0098] Without wishing to be bound by theory, the transfer laser L that has passed through the substrate 11 and the resin layer 12 is incident on the surface 20A that constitutes the interface 13 of the structure 20. The surface 20A of the structure 20 can generate heat due to the incidence of the transfer laser L. The surface 20A of the structure 20 can generate heat at a temperature equal to or higher than the thermal decomposition temperature of the resin layer 12. The heat thus generated is transferred to the resin layer 12. The resin layer 12 has a temperature gradient in which the temperature decreases with increasing distance from the interface 13. The portion 12A that constitutes the interface 13 of the resin layer 12 is then heated to a thermal decomposition temperature. This causes this portion 12A to thermally decompose. For this reason, it is preferable that the vicinity of the interface of the structure 20 that contacts the resin layer 12 contains a material that has a high absorption rate of the transfer laser L.

[0099] The thermal decomposition (ablation) of part 12A of resin layer 12 allows structure 20 to be peeled off from release plate 1. The peeled structure 20 can reach destination 30, as indicated by the dotted line in FIG. 3 . Thus, structure 20 is transferred to destination 30.

[0100] In conventional LIFT, laser irradiation ablated the resin layer 12 except for the portion 12A that constitutes the interface 30. The inventors discovered that the position of ablation varied depending on subtle variations in the laser irradiation energy density distribution for each pulse and variations in the energy density for each laser shot, resulting in variations in the amount of gas generated for each transfer and within the laser-irradiated surface. They also discovered that such variations in the amount of gas generated for each transfer and within the laser-irradiated surface affected the direction and speed of the structures 20 popping out, creating a bottleneck in improving transfer accuracy.

[0101] According to the transfer method of the present invention, the portion 12A of the resin layer 12 that constitutes the interface 30 is thermally decomposed (ablated). Therefore, even if there is a subtle variation in the laser irradiation energy density distribution for each laser shot or a variation in the energy density for each laser shot, it is possible to suppress variation in the amount of gas generated for each transfer and within the laser irradiated surface, and ultimately to make the direction and speed of the structures 20 projecting uniform, thereby improving the transfer accuracy.

[0102] That is, according to the transfer method of the present invention, the structure 20 can be transferred to the transfer destination 30 with high precision.

[0103] Furthermore, unlike conventional techniques, the transfer method of the present invention utilizes thermal decomposition at the interface 30 rather than actively ablating the resin layer 12, making it possible to employ highly transparent materials that have high transmittance to the transfer laser and have previously been difficult to use in LIFT that utilizes ablation. In other words, LIFT can be effectively performed using a resin layer that uses a material such as dimethylpolysiloxane and has a transfer laser transmittance of 90% or more.

[0104] Furthermore, unlike LIFT, which utilizes only the difference in thermal expansion between the structures 12 and the resin layer 12, this method involves thermal decomposition of the resin layer 12, thereby improving transfer accuracy.

[0105] Optional matters regarding the transfer method and transfer unit of the present invention will be described below.

[0106] For example, in the present invention, thermal decomposition of the resin layer 12 at the interface 13 can be caused by a transfer laser L that has passed through the substrate 11 and the resin layer 12, causing the surface 20A of the structure 20 that contacts the resin layer 12 to heat up to a temperature above the thermal decomposition temperature of the resin layer 12.

[0107] If the thermal decomposition temperature of the material of the surface 20A of the structure 20 that is in contact with the resin layer 12 is higher than the thermal decomposition temperature of the resin layer 12, the structure 20 can be transferred while preventing deterioration.

[0108] In particular, deterioration of the structure 20 can be more reliably prevented if the thermal decomposition temperature of the constituent material of the surface 20A of the structure 20 that is in contact with the resin layer 12 is higher by 200°C or more than the thermal decomposition temperature of the resin layer 12. The upper limit of the difference in thermal decomposition temperature is not particularly limited, but can be, for example, about 500°C.

[0109] In addition, if the surface 20A of the structure 20 in contact with the resin layer 12 becomes a thin film that is easily removed by thermal decomposition, the surface 20A of the structure 20 in contact with the resin layer 12 may be heated to a temperature above the thermal decomposition temperature. For example, if gallium nitride is used as the material for the structure 20, significant thermal decomposition occurs at temperatures above 900°C, producing a gallium metal film, which can be removed using an acidic aqueous solution such as hydrochloric acid. Depending on the solubility of the thin film produced, removal using not only the above-mentioned acidic aqueous solution but also an alkaline aqueous solution can be used. This reduces the restrictions on the materials used for the structure 20 and the resin layer 12, allowing for a wider range of combinations to be employed.

[0110] For example, the resin layer 12 may contain dimethylpolysiloxane, and the surface 20A of the structure 20 in contact with the resin layer 12 may contain gallium nitride or gallium phosphide.

[0111] Such a combination of materials is suitable when the wavelength of the transfer laser L is 248 nm.

[0112] In another embodiment, for example, the resin layer 12 may contain polyimide or benzocyclobutene resin, and the surface 20A of the structure 20 in contact with the resin layer 12 may contain gallium nitride or gallium phosphide.

[0113] The output of the transfer laser L can be selected appropriately.

[0114] 1 to 3 show an example in which the release plate 1 and the transfer destination 30 are separated by a gap, i.e., gap LIFT. In conventional gap LIFT, the positional accuracy of transfer is significantly degraded due to the aforementioned variation in the amount of gas generated within the laser irradiation surface. In contrast, the transfer method and transfer unit of the present invention can also suppress variation in the amount of gas generated within the laser irradiation surface, so that even if the gap is, for example, 300 μm, the structure 20 can be transferred with high accuracy.

[0115] Alternatively, in the transfer method and transfer unit 1 of the present invention, the release plate 1 and the transfer destination 30 can be arranged in a state in which the structure 20 is in contact with the transfer destination 30, as shown in Fig. 4, for example. LIFT performed in this state can be called, for example, contact LIFT. If the transfer method of the present invention is contact LIFT, the structure 20 can be transferred with even higher accuracy.

[0116] The transfer method of the present invention can minimize ablation of the resin layer 12 compared to conventional techniques. In other words, the thermal decomposition of the resin layer 12 can be concentrated near the interface with the structure 20. This makes it easier to reduce residue and carbon-based debris derived from the resin layer 12 at the transfer destination 30. Therefore, even when high-precision transfer is not required or when high precision is achieved by other means, the present invention can be adopted for the purpose of suppressing the generation of residue and carbon-based debris derived from the resin layer 12. Furthermore, when the structure 20 is an LED chip and the surface in contact with the resin layer 12 is the light-emitting surface, it is important to suppress the generation of the residue and carbon-based debris.

[0117] Furthermore, as long as the thermal decomposition of the resin layer 12 can be concentrated near the interface with the structure 20, the transmittance of the transfer laser of the resin layer does not need to be 90% or more, and may be less than 90%. In this case, ablation can be suppressed by reducing the thickness of the resin layer or adjusting the irradiation amount of the transfer laser in order to suppress ablation due to absorption of the transfer laser by the resin layer.

[0118] [Method for manufacturing display device and method for manufacturing mounting substrate] The method for manufacturing a display device of the present invention is a method for manufacturing a display device that transfers a structure to a wiring board, and includes: preparing a wiring board; preparing a release plate that includes a substrate, a resin layer that is provided on the substrate and has a transmittance of 90% or more for a transfer laser, and a structure that is held on the surface of the resin layer opposite the substrate; making the transfer laser incident on the substrate from the surface of the substrate opposite the resin layer; and the incident transfer laser passes through the substrate and the resin layer, and thermally decomposes at least a portion of the resin layer at the interface where the structure and the resin layer contact, and transferring the structure from the release plate to the wiring board.

[0119] In other words, the manufacturing method of the display device of the present invention can also be said to be a manufacturing method including a method of transferring a structure to a wiring substrate as a transfer destination in the transfer method of the present invention.

[0120] According to the manufacturing method of the display device of the present invention, for the reasons explained above, it is possible to suppress fluctuations in the amount of gas generated with each transfer and within the laser irradiation surface, and it is possible to make the direction and speed of the structures popping out uniform, so it is possible to manufacture a display device in which structures are arranged with high precision on the wiring substrate.

[0121] Furthermore, a method for manufacturing a mounting substrate of the present invention is a method for transferring a structure to a wiring board, comprising: preparing a wiring board; preparing a release plate including a substrate, a resin layer provided on the substrate and having a transmittance of 90% or more for a transfer laser, and a structure held on a surface of the resin layer opposite the substrate; making the transfer laser incident on the substrate from the surface of the substrate opposite the resin layer; and the incident transfer laser passes through the substrate and the resin layer, thermally decomposing at least a portion of the resin layer at the interface where the structure and the resin layer are in contact, and transferring the structure from the release plate to the wiring board.

[0122] In other words, the method for manufacturing a mounting substrate of the present invention can also be said to be a manufacturing method that includes transferring a structure to a wiring board as the transfer destination in the transfer method of the present invention.

[0123] According to the method for manufacturing a mounting substrate according to the present invention, for the reasons explained above, it is possible to suppress fluctuations in the amount of gas generated for each transfer and within the laser irradiation surface, and it is possible to make the direction and speed of the structures projecting uniform, so that a mounting substrate can be manufactured in which structures are arranged with high precision on a wiring board.

[0124] EXAMPLES The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these.

[0125] Example In the example, the transfer unit 10 shown in FIGS. 1 to 3 was used to transfer the structure 20 by gap LIFT.

[0126] A release plate 1 was prepared which included a quartz substrate 11, a resin layer 12 made of dimethylpolysiloxane, and 20 micro LED chips 20 held on the surface of the substrate 11 opposite to the resin layer 12. A surface 20A of the micro LED chips 20 in contact with the resin layer 12 contained gallium nitride.

[0127] The light source 2 was provided with a laser oscillator 21 capable of oscillating a pulse excimer laser having a wavelength of 248 nm as a transfer laser L.

[0128] As the transfer destination 30, a donor plate was prepared, which was made of a quartz substrate and had a silicone resin layer formed on the surface thereof.

[0129] The transmittance of the resin layer 12 to the transfer laser L was 90% or more.

[0130] In the transfer unit prepared as described above, the alignment mechanism 4 and the controller 5 were used to irradiate the transfer laser L onto the substrate 11 from the surface of the substrate 11 opposite to the resin layer 12. As a result, the output of the transfer laser L was controlled so that the transfer laser L was transmitted through the substrate 11 and the resin layer 12 and a part 12 of the resin layer 12 was thermally decomposed at the interface 13 where the micro LED chip 20 and the resin layer 12 were in contact. In this way, the micro LED chip 20 was transferred from the release plate 1 to the transfer destination 30.

[0131] In this example, the transfer to the target position was performed with high accuracy. Furthermore, when the release plate 1 after the transfer in this example was observed, the resin layer 12 had decomposed only in the vicinity of the surface that held the micro LED chip 20.

[0132] From these results, it is believed that in the example, since only the vicinity of the surface of the resin layer 12 that held the micro LED chip 20 was able to be decomposed during each transfer, it was possible to suppress fluctuations in the amount of gas generated for each transfer and within the laser irradiation surface, and it was possible to make the protrusion direction and speed of the micro LED chip 20 uniform, thereby enabling the micro LED chip 20 to be transferred to the transfer destination 30 with high precision.

[0133] (Comparative Example) Transfer was performed in the same manner as in the example, except that the output of the transfer laser L was controlled so that the transfer laser L passed through the substrate 11 and the resin layer 12 and did not thermally decompose a portion 12 of the resin layer 12 at the interface 13 where the micro LED chip 20 and the resin layer 12 contact.

[0134] In this comparative example, compared to the working example, some of the micro LED chips 20 were not transferred to the desired positions. Furthermore, when observing the release plate after transfer in the comparative example, no thermal decomposition of the resin layer 12 was confirmed near the surface that held the micro LED chips 20. The reason why the transfer accuracy in the comparative example was inferior to that in the working example is thought to be that because peeling was achieved using only the difference in thermal expansion between the structure and the resin layer, positional deviation in the surface direction was likely to occur.

[0135] This specification includes the following aspects. [1] A transfer method for transferring a structure to a transfer destination, comprising: preparing a release plate including a substrate, a resin layer provided on the substrate and having a transfer laser transmittance of 90% or more, and a structure held on the surface of the resin layer opposite the substrate; illuminating the substrate with the transfer laser from the surface of the substrate opposite the resin layer; and the incident transfer laser passing through the substrate and the resin layer to thermally decompose at least a portion of the resin layer at the interface between the structure and the resin layer, and transferring the structure from the release plate to the transfer destination. [2] The transfer method described in [1], wherein the thermal decomposition of the resin layer at the interface occurs when the transfer laser passing through the substrate and the resin layer heats the surface of the structure in contact with the resin layer to a temperature equal to or higher than the thermal decomposition temperature of the resin layer. [3] The transfer method described in [1] or [2], wherein the thermal decomposition temperature of a constituent material of the surface of the structure in contact with the resin layer is higher than the thermal decomposition temperature of the resin layer. [4] The transfer method according to [3], wherein the thermal decomposition temperature of the constituent material of the surface of the structure in contact with the resin layer is at least 200°C higher than the thermal decomposition temperature of the resin layer. [5] The transfer method according to any one of [1] to [4], wherein the resin layer contains dimethylpolysiloxane. [6] The transfer method according to any one of [1] to [5], wherein the surface of the structure in contact with the resin layer contains gallium nitride. [7] The transfer method according to any one of [1] to [6], wherein the resin layer contains dimethylpolysiloxane and the surface of the structure in contact with the resin layer contains gallium nitride. [8] The transfer method according to any one of [1] to [6], wherein the resin layer contains polyimide and the surface of the structure in contact with the resin layer contains gallium phosphide. [9] The transfer method according to any one of [1] to [8], wherein the transfer laser is an excimer laser having a wavelength of 248 nm.

[10] A transfer unit for transferring a structure to a transfer destination, comprising: a light source that oscillates a transfer laser; a release plate including a substrate, a resin layer provided on the substrate and having a transmittance of the transfer laser of 90% or more, and a structure held on a surface of the resin layer opposite the substrate; a holding mechanism configured to hold the transfer destination; an alignment mechanism configured to position the light source and the holding mechanism opposite each other with the release plate therebetween; and a controller configured to control oscillation of the transfer laser by the light source so that the transfer laser is incident on the substrate from the surface opposite the resin layer, and thermally decomposes at least a portion of the resin layer at an interface where the structure and the resin layer contact.

[11] The transfer unit according to

[10] , which thermally decomposes at least a portion of the resin layer at the interface where the structure and the resin layer contact, and transfers the structure from the release plate to the transfer destination.

[12] The transfer unit according to

[11] , wherein the thermal decomposition of the resin layer at the interface occurs when the transfer laser transmitted through the substrate and the resin layer heats the surface of the structure in contact with the resin layer to a temperature equal to or higher than the thermal decomposition temperature of the resin layer.

[13] The transfer unit according to

[10] or

[11] , wherein the thermal decomposition temperature of the constituent material of the surface of the structure in contact with the resin layer is higher than the thermal decomposition temperature of the resin layer.

[14] The transfer unit according to

[13] , wherein the thermal decomposition temperature of the constituent material of the surface of the structure in contact with the resin layer is 200°C or more higher than the thermal decomposition temperature of the resin layer.

[15] The transfer unit according to any one of

[10] to

[14] , wherein the resin layer contains dimethylpolysiloxane.

[16] The transfer unit according to any one of

[10] to

[15] , wherein the surface of the structure in contact with the resin layer contains gallium nitride.

[17] The transfer unit according to any one of

[10] to

[16] , wherein the resin layer contains dimethylpolysiloxane, and the surface of the structure in contact with the resin layer contains gallium nitride.

[18] The transfer unit according to any one of

[10] to

[16] , wherein the resin layer contains polyimide, and the surface of the structure in contact with the resin layer contains gallium phosphide.

[19] The transfer unit according to any one of

[10] to

[18] , wherein the light source oscillates an excimer laser having a wavelength of 248 nm.

[20] A method for manufacturing a display device by transferring a structure onto a wiring substrate, the method comprising: preparing a wiring substrate; preparing a release plate including a base material, a resin layer provided on the base material and having a transmittance of 90% or more for a transfer laser, and a structure held on a surface of the resin layer opposite to the base material; making the transfer laser incident on the base material from the surface of the base material opposite to the resin layer; the incident transfer laser transmits through the base material and the resin layer, and thermally decomposes at least a portion of the resin layer at an interface between the structure and the resin layer, and transferring the structure from the release plate to the wiring substrate.

[21] A method for manufacturing a mounting substrate in which a structure is transferred to a wiring board, the method comprising: preparing a wiring board; preparing a release plate including a base material, a resin layer provided on the base material and having a transfer laser transmittance of 90% or more, and a structure held on a surface of the resin layer opposite the base material; making the transfer laser incident on the base material from the surface of the base material opposite the resin layer; the incident transfer laser passes through the base material and the resin layer, and thermally decomposes at least a portion of the resin layer at an interface where the structure and the resin layer are in contact, and transferring the structure from the release plate to the wiring board.

[0136] 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 transfer method for transferring a structure to a transfer destination, comprising: preparing a release plate including a substrate, a resin layer provided on the substrate and having a transmittance of a transfer laser of 90% or more, and a structure held on a surface of the resin layer opposite to the substrate; causing the transfer laser to enter the substrate from a surface of the substrate opposite to the resin layer; and the incident transfer laser passing through the substrate and the resin layer, thermally decomposing at least a part of the resin layer at an interface where the structure is in contact with the resin layer, and transferring the structure from the release plate to the transfer destination.

2. The transfer method according to claim 1, wherein the thermal decomposition of the resin layer at the interface is caused by the transfer laser passing through the substrate and the resin layer, and the surface of the structure in contact with the resin layer generating heat to a temperature equal to or higher than the thermal decomposition temperature of the resin layer.

3. The transfer method according to claim 1 or 2, wherein the thermal decomposition temperature of the constituent material of the surface of the structure in contact with the resin layer is higher than the thermal decomposition temperature of the resin layer.

4. The transfer method according to claim 3, wherein the thermal decomposition temperature of the constituent material of the surface of the structure in contact with the resin layer is 200°C or more higher than the thermal decomposition temperature of the resin layer.

5. The transfer method according to claim 1 or 2, wherein the resin layer contains dimethylpolysiloxane.

6. The transfer method according to claim 1 or 2, wherein the surface of the structure in contact with the resin layer contains gallium nitride.

7. The transfer method according to claim 3, wherein the resin layer contains dimethylpolysiloxane and the surface of the structure in contact with the resin layer contains gallium nitride.

8. The transfer method according to claim 3, wherein the resin layer contains polyimide and the surface of the structure in contact with the resin layer contains gallium phosphide.

9. The transfer method according to claim 1 or 2, wherein the transfer laser is an excimer laser having a wavelength of 248 nm.

10. A transfer unit for transferring a structure to a transfer destination, comprising: a light source that oscillates a transfer laser; a substrate; a resin layer provided on the substrate and having a transmittance of the transfer laser of 90% or more; a release plate including a structure held on a surface of the resin layer opposite to the substrate; a holding mechanism configured to hold the transfer destination; an alignment mechanism configured to oppose the light source and the holding mechanism with the release plate interposed therebetween; and a controller configured to control oscillation of the transfer laser by the light source such that the transfer laser enters the substrate from a surface of the substrate opposite to the resin layer and thermally decomposes at least a part of the resin layer at an interface where the structure and the resin layer are in contact.

11. The transfer unit according to claim 10, wherein at least a part of the resin layer is thermally decomposed at the interface where the structure and the resin layer are in contact, and the structure is transferred from the release plate to the transfer destination.

12. The transfer unit according to claim 11, wherein the thermal decomposition of the resin layer at the interface occurs because the surface of the structure in contact with the resin layer generates heat to a temperature equal to or higher than the thermal decomposition temperature of the resin layer by the transfer laser that has passed through the substrate and the resin layer.

13. The transfer unit according to claim 10 or 11, wherein the thermal decomposition temperature of the constituent material of the surface of the structure in contact with the resin layer is higher than the thermal decomposition temperature of the resin layer.

14. The transfer unit according to claim 13, wherein the thermal decomposition temperature of the constituent material of the surface of the structure in contact with the resin layer is 200°C or higher higher than the thermal decomposition temperature of the resin layer.

15. The transfer unit according to claim 10 or 11, wherein the resin layer contains dimethylpolysiloxane.

16. The transfer unit according to claim 10 or 11, wherein the surface of the structure in contact with the resin layer contains gallium nitride.

17. The transfer unit according to claim 13, wherein the resin layer contains dimethylpolysiloxane and the surface of the structure in contact with the resin layer contains gallium nitride.

18. The transfer unit according to claim 13, wherein the resin layer contains polyimide and the surface of the structure in contact with the resin layer contains gallium phosphide.

19. The transfer unit according to claim 10 or 11, wherein the light source oscillates an excimer laser having a wavelength of 248 nm.

20. A method for manufacturing a display device that transfers a structure onto a wiring substrate, the method including: preparing a wiring substrate; preparing a release plate including a base material, a resin layer provided on the base material and having a transmittance of a transfer laser of 90% or more, and a structure held on a surface of the resin layer opposite to the base material; causing the transfer laser to enter the base material from a surface of the base material opposite to the resin layer; and causing the incident transfer laser to pass through the base material and the resin layer, thermally decomposing at least a part of the resin layer at an interface where the structure and the resin layer are in contact with each other, and transferring the structure from the release plate onto the wiring substrate.

21. A method for manufacturing a mounting substrate that transfers a structure onto a wiring substrate, the method including: preparing a wiring substrate; preparing a release plate including a base material, a resin layer provided on the base material and having a transmittance of a transfer laser of 90% or more, and a structure held on a surface of the resin layer opposite to the base material; causing the transfer laser to enter the base material from a surface of the base material opposite to the resin layer; and causing the incident transfer laser to pass through the base material and the resin layer, thermally decomposing at least a part of the resin layer at an interface where the structure and the resin layer are in contact with each other, and transferring the structure from the release plate onto the wiring substrate.

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