Device transfer sheet

Abstract

The present invention further increases, when an element transfer sheet provided with an adhesive layer having relief on the surface thereof is extended, the interval between elements held by the sheet.　This element transfer sheet is provided with a base material and an adhesive layer having relief on the surface thereof. When the base material is extended 100%, the tensile stress in a first direction is higher than the tensile stress in a second direction orthogonal to the first direction. The tensile stress in the first direction is not less than 12 MPa. The tensile stress in the second direction is not less than 9 MPa.

Description

[Technical field]

[0001] The present invention relates to a sheet for transferring an element. [Background technology]

[0002] An element transfer sheet used for transferring an element is known. Such a sheet can be used to temporarily hold an object and transfer it to a desired position. It is also known to expand the sheet while the element transfer sheet is holding an object.

[0003] For example, Patent Document 1 describes dicing a semiconductor wafer attached on a dicing film, and then expanding the dicing film after dicing to separate the chips, and picking up and transferring each chip to another substrate. Patent Document 1 discloses that a material having a specific density and specific components is used as the material for the dicing film in order to form uniform gaps between the chips in the expanding process. Non-Patent Documents 2 and 3 describe attaching a wafer to an adhesive tape, irradiating a laser beam to a portion to be cut, and expanding the adhesive tape to cut the wafer along the portion to be cut. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-014557 [Patent Document 1] JP 2023-013022 A [Patent Document 1] JP 2023-013023 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have investigated providing irregularities on the surface of the adhesive layer of the element transfer sheet. According to this configuration, the sheet can be expanded to reduce the holding force of the element by the sheet, making it easier to peel the element from the sheet. However, it has been found that even if the sheet is expanded while the element is held on the element transfer sheet having such irregularities, the spacing between the elements may not be increased much.

[0006] An object of the present invention is to increase the spacing between elements held by a device transfer sheet having an adhesive layer with unevenness on its surface when the sheet is expanded. [Means for solving the problem]

[0007] As a result of extensive research, the inventors discovered that by appropriately adjusting the tensile stress of the substrate of the element transfer sheet, the spacing between the elements held by the sheet can be increased when the sheet is expanded, thereby solving the above-mentioned problem. After further research, the inventors have completed the present invention.

[0008] That is, the present invention relates to the following [1] to [9]. [1] A sheet for element transfer comprising a substrate and an adhesive layer having an uneven surface, A sheet for element transfer, wherein the tensile stress in a first direction when the substrate is 100% elongated is higher than the tensile stress in a second direction perpendicular to the first direction, the tensile stress in the first direction being 12 MPa or more, and the tensile stress in the second direction being 9 MPa or more. [2] The element transfer sheet according to [1], wherein the tensile stress in the first direction is 40 MPa or less, and the tensile stress in the second direction is 30 MPa or less. [3] The sheet for transferring elements according to any one of [1] to [2], wherein the substrate has a tensile modulus of elasticity of 2500 MPa or less. [4] The sheet for transferring elements according to any one of [1] to [3], wherein the substrate has a breaking elongation of 105% or more. [5] The sheet for transferring elements according to any one of [1] to [4], wherein the substrate is a polyolefin film or a vinyl chloride copolymer film. [6] The element transfer sheet described in any one of [1] to [5], wherein the adhesive layer has a plurality of convex portions spaced apart from one another and bounded by concave portions, and the pitch of the plurality of convex portions is 1 μm or more and 100 μm or less. [7] The element transfer sheet described in any one of [1] to [6], wherein the adhesive layer has a plurality of convex portions, and the height of the plurality of convex portions is uniform. [8] An element transfer sheet described in any one of [1] to [7], wherein after a wafer substrate held by the adhesive layer is diced to form a plurality of elements, when the element transfer sheet is expanded by 180% in the first direction and the second direction, the coefficient of variation of the spacing between the plurality of elements is 0.2 or less. [9] An element transfer sheet according to any one of items [1] to [8], wherein after a wafer substrate held by the adhesive layer is diced to form a plurality of elements, when the element transfer sheet is expanded by 80 mm in the first direction and the second direction, the average spacing between the plurality of elements is 1 mm or more. Effect of the Invention

[0009] When the element transfer sheet having an adhesive layer with an uneven surface is expanded, the spacing between the elements held by the sheet can be made larger. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a cross-sectional view of a sheet according to an embodiment. [Figure 2A] FIG. 4 is a cross-sectional view showing an example of projections and recesses on a sheet. [Figure 2B] FIG. 4 is a cross-sectional view showing an example of projections and recesses on a sheet. [Figure 3A] FIG. 4 is a top view showing an example of unevenness of a sheet. [Figure 3B] FIG. 4 is a top view showing an example of unevenness of a sheet. [Figure 3C] FIG. 4 is a top view showing an example of unevenness of a sheet. [Figure 4A] FIG. 4 is a cross-sectional view showing an example of projections and recesses on a sheet. [Figure 4B] FIG. 4 is a cross-sectional view showing an example of projections and recesses on a sheet. [Figure 4C] FIG. 4 is a cross-sectional view showing an example of projections and recesses on a sheet. [Figure 5A] 11A and 11B are diagrams for explaining a sheet expansion method. [Figure 5B] 11A and 11B are diagrams for explaining a sheet expansion method. [Figure 6] 1 is a flowchart of an element transfer method according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more features among the multiple features described in the embodiments may be arbitrarily combined. In addition, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0012] (definition) In this specification, the mass average molecular weight (Mw) and the number average molecular weight (Mn) are values ​​calculated in terms of standard polystyrene measured by size exclusion chromatography, specifically, values ​​measured based on JIS K7252-1: 2016. In addition, in this specification, "(meth)acrylic acid" is a term that refers to both "acrylic acid" and "methacrylic acid", and the same applies to other similar terms.

[0013] In the present specification, when one or more lower limit values ​​and one or more upper limit values ​​of a numerical range (e.g., a range of content, etc.) are described, it can be understood that any combination of the lower limit value and the upper limit value therein is described. For example, the description that it is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and preferably 9 or less, more preferably 8 or less, even more preferably 7 or less clearly means that the numerical range may be any of 1 or more to 9 or less, 1 or more to 8 or less, 1 or more to 7 or less, 2 or more to 9 or less, 2 or more to 8 or less, 2 or more to 7 or less, 3 or more to 9 or less, 3 or more to 8 or less, and 3 or more to 7 or less.

[0014] (Sheet configuration) The element transfer sheet according to one embodiment of the present invention includes a substrate 120 and an adhesive layer 110 having an uneven surface. The element transfer sheet is used to temporarily hold an element and transfer it to a transfer destination. For example, the element transfer sheet can be used to receive an element held on another holding substrate, temporarily hold the element, and transfer the element to a desired position on the transfer destination. The substrate 120 can support the adhesive layer 110. The configuration of such a sheet will be described below with reference to FIG. 1, which is a schematic diagram of a sheet according to one embodiment. In this specification, the element transfer sheet may be simply called a sheet.

[0015] (base material)

[0016] The substrate 120 functions as a support for supporting the adhesive layer 110. The substrate 120 is located on the surface of the adhesive layer 110 opposite to the surface having the projections and recesses.

[0017] As described later, the sheet according to this embodiment can be expanded. From this viewpoint, a flexible substrate can be used as the substrate 120. In addition, by using a flexible substrate as the substrate 120, it is possible to improve the cushioning property when holding the element, to facilitate stacking of the sheets, or to make the sheet into a roll form. For example, a resin film can be used as the substrate 120. The resin film is a film in which a resin-based material is used as the main material, and may be made of a resin material, or may contain an additive in addition to the resin material. The resin film may have laser light transparency.

[0018] In this embodiment, the tensile stress in the first direction when the substrate 120 is 100% elongated is higher than the tensile stress in the second direction perpendicular to the first direction. In addition, in this embodiment, the tensile stress in the first direction and the second direction when the substrate 120 is 100% elongated is sufficiently high. The tensile stress in the first direction when the substrate 120 is 100% elongated is 12 MPa or more, preferably 14 MPa or more, more preferably 18 MPa or more, and even more preferably 22 MPa or more. In addition, the tensile stress in the second direction when the substrate 120 is 100% elongated is 9 MPa or more, preferably 12 MPa or more, and more preferably 15 MPa or more. By using a substrate 120 having such a tensile stress, the spacing between the multiple elements held by the sheet tends to become larger when the sheet is expanded. In addition, by using a substrate 120 having such a tensile stress, the variation in the spacing between the multiple elements held by the sheet tends to become smaller when the sheet is expanded. By using such a sheet according to this embodiment, it becomes easy to selectively transfer elements held on the sheet.

[0019] On the other hand, the tensile stress in the first direction when the substrate 120 is 100% elongated is preferably 40 MPa or less, more preferably 30 MPa or less, and even more preferably 25 MPa or less. Also, the tensile stress in the second direction when the substrate 120 is 100% elongated is preferably 30 MPa or less, more preferably 25 MPa or less, and even more preferably 20 MPa or less. By not making the tensile stress of the substrate 120 too high in this way, uniform expansion of the sheet becomes easier.

[0020] Furthermore, from the viewpoint of increasing the spacing between the multiple elements held by the sheet while reducing the variation in this spacing when the sheet is expanded, the tensile stress in the first direction when the substrate 120 is 100% elongated is preferably 12 MPa or more, more preferably 14 MPa or more, while it is preferably 40 MPa or less, and more preferably 16 MPa or less. From the same viewpoint, the tensile stress in the second direction when the substrate 120 is 100% elongated is preferably 9 MPa or more, more preferably 10 MPa or more, and even more preferably 10.5 MPa or more, while it is preferably 30 MPa or less, more preferably 15 MPa or less, and even more preferably 12 MPa or less.

[0021] The first direction may be the direction in which the tensile stress is the highest. The first direction may be the MD direction. MD in the MD direction is an abbreviation for Machine Direction, and for example, the MD direction of the substrate means the longitudinal direction when the substrate is manufactured. On the other hand, the second direction may be the direction in which the tensile stress is the lowest. The second direction may be the TD direction. TD in the TD direction is an abbreviation for Transverse Direction, and for example, the TD direction of the substrate means the width direction when the substrate is manufactured. In this way, the MD direction and the TD direction are perpendicular to each other. In this specification, the tensile stress is measured as shown in the examples.

[0022] The inventors of the present application consider that by increasing the tensile stress of the substrate 120 as described above, the force that the elements receive when the sheet is expanded increases, and as a result, the spacing between the elements increases and the variation in spacing decreases. The tensile stress of the substrate 120 can be adjusted, for example, by selecting the resin material or combination of resin materials that constitute the substrate 120, or by mixing an additive. In addition, when a copolymer is used as the material of the substrate 120, the tensile stress of the substrate 120 can be adjusted by selecting the combination or ratio of the constituent units.

[0023] In addition, by increasing the tensile stress of the base material 120 as in this embodiment, even if there is a difference between the tensile stress in the first direction and the tensile stress in the second direction of the base material 120, it is possible to reduce the variation in the intervals between the multiple elements held by the sheet. In addition, in this embodiment, the adhesive layer 110 on the base material 120 has unevenness, which is also considered to contribute to reducing the variation in the intervals in such a case. From this perspective, the absolute value of the difference between the tensile stress in the first direction and the tensile stress in the second direction when the base material 120 is 100% elongated may be 2.0 MPa or more, 3.0 MPa or more, or 4.0 MPa or more.

[0024] Specific examples of the resin film include polyethylene films such as low-density polyethylene (LDPE) film, linear low-density polyethylene (LLDPE) film, and high-density polyethylene (HDPE) film, polyolefin films such as polypropylene film, polybutene film, polybutadiene film, poly(4-methyl-1-pentene) film, ethylene-norbornene copolymer film, and norbornene resin film; ethylene copolymer films such as ethylene-vinyl acetate copolymer film, ethylene-(meth)acrylic acid copolymer film, and ethylene-(meth)acrylic acid ester copolymer film; polyvinyl chloride films such as polyvinyl chloride film and vinyl chloride copolymer film; polyester films such as polyethylene terephthalate film and polybutylene terephthalate film; polyurethane film; polyimide film; polystyrene film; polycarbonate film; and fluororesin film. Films containing a mixture of two or more materials, crosslinked films in which the resins forming these films are crosslinked, and modified films such as ionomer films may also be used. The substrate 120 may also be a laminated film in which two or more resin films are laminated.

[0025] From the viewpoint of facilitating the expansion of the sheet, the substrate 120 is preferably a polyolefin-based film or a vinyl chloride copolymer film. Examples of polyolefin-based films include polyethylene films, polypropylene films, and copolymers containing unsubstituted olefins such as ethylene or propylene as a constituent unit, such as ethylene-based copolymers containing ethylene-methacrylic acid copolymer (EMAA). Examples of vinyl chloride copolymer films include vinyl chloride-vinylidene chloride copolymer films, vinyl chloride-vinyl acetate copolymer films, and vinyl chloride-ethylene copolymer films. The form of such copolymers is not particularly limited, and may be any of block copolymers, random copolymers, alternating copolymers, and graft copolymers. These films may contain other resin components or additives.

[0026] The thickness of the substrate 120 is not particularly limited, but from the viewpoint of achieving both supportability and roll winding ability, it is preferably 10 μm or more, more preferably 25 μm or more, and even more preferably 40 μm or more, while it is preferably 500 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, still more preferably 150 μm or less, still more preferably 120 μm or less, and particularly preferably 90 μm or less.

[0027] In order to facilitate uniform expansion of the sheet, the tensile modulus of the substrate 120 is preferably 50 MPa or more, more preferably 80 MPa or more, and even more preferably 120 MPa or more, and is preferably 2500 MPa or less, more preferably 1000 MPa or less, and even more preferably 500 MPa or less. In this specification, the tensile modulus is measured according to JIS K7161-1:2014.

[0028] Similarly, in order to facilitate expansion of the sheet, the breaking elongation of the substrate 120 is preferably 105% or more, more preferably 150% or more, and even more preferably 200% or more. In this specification, the breaking elongation is measured in accordance with JIS K 7127:1999.

[0029] (Adhesive layer) The adhesive layer 110 is a layer having adhesiveness and may contain a resin. As described above, the adhesive layer 110 has an uneven surface. The sheet may have two or more adhesive layers 110. For example, the sheet may have a laminate of one type or two or more types of adhesive layers 110.

[0030] (Composition of adhesive layer) Examples of the resin contained in the adhesive layer 110 include rubber-based resins such as polyisobutylene-based resins, polybutadiene-based resins, and styrene-butadiene-based resins, acrylic resins, urethane-based resins, polyester-based resins, olefin-based resins, silicone-based resins, and polyvinyl ether-based resins. The adhesive layer may have heat resistance, and examples of the material of the adhesive layer 110 having such heat resistance include polyimide-based resins and silicone-based resins. The adhesive layer 110 may contain a copolymer having two or more types of constituent units. The form of such a copolymer is not particularly limited, and may be any of a block copolymer, a random copolymer, an alternating copolymer, and a graft copolymer.

[0031] The resin contained in the adhesive layer 110 is preferably an adhesive resin having adhesiveness by itself. The resin is preferably a polymer having a mass average molecular weight (Mw) of 10,000 or more. From the viewpoint of improving the retention, the mass average molecular weight (Mw) of the resin is preferably 10,000 or more, more preferably 70,000 or more, and even more preferably 140,000 or more. From the viewpoint of suppressing the storage modulus to a predetermined value or less, the mass average molecular weight (Mw) of the resin is preferably 2 million or less, and more preferably 1.2 million or less. From the viewpoint of improving the retention, the number average molecular weight (Mn) of the resin is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more. From the viewpoint of suppressing the storage modulus to a predetermined value or less, the number average molecular weight (Mn) of the resin is preferably 2 million or less, more preferably 1.5 million or less, and even more preferably 1.2 million or less. In addition, when the adhesive layer 110 contains a resin derived from an energy reactive resin as described later, the mass average molecular weight (Mw) and the number average molecular weight (Mn) refer to the mass average molecular weight (Mw) and the number average molecular weight (Mn) before the crosslinking reaction due to the application of energy. The glass transition temperature (Tg) of the resin is preferably −75° C. or higher, more preferably −70° C. or higher, and preferably 5° C. or lower, more preferably −20° C. or lower. When Tg is within this range, the retention and storage modulus of the obtained adhesive layer 110 are easily set within the ranges described below.

[0032] The amount of resin contained in adhesive layer 110 relative to the total amount of components constituting adhesive layer 110 can be set appropriately depending on the desired retention and storage modulus of adhesive layer 110, but is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and is preferably 99.99% by mass or less, more preferably 99.95% by mass or less, even more preferably 99.90% by mass or less, even more preferably 99.80% by mass or less, and even more preferably 99.50% by mass or less.

[0033] The storage modulus of the adhesive layer 110 is preferably 0.001 MPa or more, more preferably 0.01 MPa or more, even more preferably 0.03 MPa or more, and even more preferably 0.07 MPa or more, from the viewpoint of the morphological stability of the uneven shape of the adhesive layer surface. On the other hand, a low storage modulus of the adhesive layer 110 is preferable in that it can suppress positional deviation when holding an element. From this viewpoint, the storage modulus of the adhesive layer 110 is preferably 100 MPa or less, more preferably 50 MPa or less, even more preferably 20 MPa or less, and particularly preferably 5 MPa or less. In this specification, the storage modulus is measured according to JIS K7244-1:1998. Specifically, the storage modulus of the adhesive layer 110 can be measured by preparing a cylindrical sample having a thickness of 3 mm and a diameter of 8 mm, and measuring the storage modulus of the sample by a torsional shear method using a viscoelasticity measuring device under an environment of 1 Hz and 23°C.

[0034] In one embodiment, the resin contained in the adhesive composition forming the adhesive layer 110 may include a thermoplastic resin. That is, the adhesive layer 110 can be formed from a thermoplastic resin. When a thermoplastic resin is used, it becomes easy to form unevenness in the adhesive layer 110 by heating and softening the resin, and it becomes easy to maintain the uneven shape formed by cooling. Examples of the thermoplastic resin include rubber-based resins, acrylic-based resins, urethane-based resins, and olefin-based resins. Examples include polybutadiene-based thermoplastic elastomers using butadiene as a monomer, styrene-based thermoplastic elastomers using styrene as a monomer, and acrylic-based thermoplastic elastomers using (meth)acrylic acid or (meth)acrylic acid esters as a monomer.

[0035] The following describes examples of the composition of the adhesive layer 110. However, the composition of the adhesive layer 110 is not limited to those shown below.

[0036] (Acrylic resin (A)) In one embodiment, the adhesive composition forming the adhesive layer 110 contains an acrylic resin. The acrylic resin is a resin containing (meth)acrylic acid or a (meth)acrylic acid ester as a monomer. From the viewpoint of improving adhesive strength, the mass average molecular weight (Mw) of the acrylic resin is preferably 10,000 or more, more preferably 100,000 or more, and even more preferably 500,000 or more. Moreover, from the viewpoint of suppressing the storage modulus to a predetermined value or less, the mass average molecular weight (Mw) is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,200,000 or less.

[0037] The glass transition temperature (Tg) of the acrylic resin is preferably −75° C. or higher, more preferably −70° C. or higher, and preferably 5° C. or lower, more preferably −20° C. or lower. When Tg is within this range, it becomes easier to obtain the adhesive layer 110 having the above-mentioned storage modulus.

[0038] When an acrylic resin has two or more structural units, the glass transition temperature (Tg) of the acrylic resin can be calculated using the Fox formula. The Tg of the monomer from which the structural unit is derived can be calculated using the value listed in the Polymer Data Handbook or the Adhesive Handbook.

[0039] Examples of (meth)acrylic acid esters constituting acrylic resins include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and butyl (meth)acrylate. The alkyl group constituting the alkyl ester, such as acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, myristyl (meth)acrylate, pentadecyl (meth)acrylate, palmityl (meth)acrylate, heptadecyl (meth)acrylate, and stearyl (meth)acrylate, has a chain structure having 1 to 18 carbon atoms (meth). (meth)acrylic acid alkyl esters; (meth)acrylic acid cycloalkyl esters such as isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate; (meth)acrylic acid aralkyl esters such as benzyl (meth)acrylate; (meth)acrylic acid cycloalkenyl esters such as dicyclopentenyl (meth)acrylate; (meth)acrylic acid cycloalkenyloxyalkyl esters such as dicyclopentenyloxyethyl (meth)acrylate; imide (meth)acrylates; glycidyl (meth)acrylate and other glycidyl (meth)acrylates. Examples of the acrylates include lysidyl group-containing (meth)acrylic acid esters; hydroxyl group-containing (meth)acrylic acid esters such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and substituted amino group-containing (meth)acrylic acid esters such as N-methylaminoethyl (meth)acrylate.Here, the term "substituted amino group" refers to a group having a structure in which one or two hydrogen atoms of an amino group are substituted with a group other than a hydrogen atom.

[0040] The acrylic resin may be, for example, a resin obtained by copolymerizing one or more monomers selected from the group consisting of (meth)acrylic acid esters or (meth)acrylic acid, itaconic acid, vinyl acetate, acrylonitrile, styrene, and N-methylolacrylamide.

[0041] The monomer constituting the acrylic resin may be of only one type, or of two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily.

[0042] In one embodiment, the acrylic resin contains a monomer having a hydroxyl group as a constituent unit. The acrylic resin may have a functional group capable of bonding with other compounds, such as a vinyl group, a (meth)acryloyl group, an amino group, a carboxy group, or an isocyanate group, in addition to the hydroxyl group. These functional groups, including the hydroxyl group of the acrylic resin, may bond with other compounds via a crosslinking agent (C) described later, or may bond directly with other compounds without the crosslinking agent (C).

[0043] The amount of acrylic resin in the total amount of resin in the adhesive composition can be set appropriately depending on the desired adhesive strength and storage modulus of the adhesive layer 110, but is preferably 0 mass% or more, more preferably 10 mass% or more, even more preferably 20 mass% or more, even more preferably 50 mass% or more, and is preferably 100 mass% or less, more preferably 95 mass% or less, even more preferably 80 mass% or less, even more preferably 60 mass% or less.

[0044] (Energy reactive resin (B)) In one embodiment, the adhesive composition forming the adhesive layer 110 contains an energy reactive resin (B). The energy reactive resin (B) refers to a resin whose elastic modulus is improved by the application of energy. The energy reactive resin may be a resin derived from an energy reactive monomer. In this case, the energy reactive resin is a resin obtained by polymerizing the energy reactive monomer by the application of energy.

[0045] Examples of the energy reactive resin include energy ray reactive resin and heat reactive resin. The energy ray reactive resin refers to a resin whose elastic modulus is improved by irradiation with energy rays. For example, the energy reactive resin may be an energy ray curable resin. The heat reactive resin refers to a resin whose elastic modulus is improved by heating. The resin contained in the adhesive layer 110 is more preferably derived from a thermoplastic energy reactive resin, and even more preferably derived from a thermoplastic energy ray reactive resin. The type of energy ray is not particularly limited, and examples thereof include ultraviolet rays, electron beams, and ionizing radiation. The energy ray is preferably ultraviolet rays, that is, the resin is preferably an ultraviolet-reactive resin.

[0046] A thermoplastic energy reactive resin refers to an energy reactive resin that has thermoplasticity at least before energy is applied. Also, a resin derived from an energy reactive resin means that the resin is obtained from an energy reactive resin. For example, a resin derived from an energy reactive resin is a crosslinked energy reactive resin.

[0047] When such an energy reactive resin is used, it becomes easy to maintain the uneven shape formed by providing energy (for example, by irradiating with energy rays) after forming the unevenness in the resin.

[0048] As such an energy reactive resin, a polymer having a polymerizable functional group can be used. The polymerizable functional group is a functional group that is crosslinked by the application of energy (for example, irradiation with energy rays). Examples of the polymerizable functional group include alkenyl groups such as vinyl groups and allyl groups, (meth)acryloyl groups, oxetanyl groups, and epoxy groups.

[0049] For example, diene rubber composed of a polymer having a polymerizable functional group at the main chain end and / or side chain can be used as the energy reactive resin. Diene rubber refers to a rubbery polymer having a double bond in the polymer main chain. Specific examples of diene rubber include polymers using butadiene or isoprene as a monomer (i.e., having butenediyl or pentenediyl groups as a constituent unit). Preferred examples of the energy reactive resin include polybutadiene resin (PB resin), styrene-butadiene-styrene block copolymer (SBS resin), and styrene-isoprene-styrene block copolymer. These resins can be used as ultraviolet reactive resins.

[0050] The average number of polymerizable functional groups per molecule in these energy reactive resins is preferably 1.5 or more, more preferably 2 or more, from the viewpoint of easily maintaining the uneven shape of the adhesive layer 110. On the other hand, from the viewpoint of enhancing the adhesiveness and flexibility of the adhesive layer 110, this average is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less.

[0051] The adhesive layer 110 may contain one type of resin, or may contain two or more types of resin. The adhesive layer 110 according to an embodiment contains a liquid resin, a resin derived from an energy reactive liquid resin, or a resin derived from an energy reactive monomer, in addition to a resin derived from a thermoplastic resin or a thermoplastic energy reactive resin. The liquid resin refers to a resin that is liquid at room temperature (25°C) before mixing. The energy reactive liquid resin refers to an energy reactive resin that is liquid at room temperature (25°C) before mixing and before energy is applied. The resin derived from an energy reactive monomer refers to a resin obtained by polymerizing an energy reactive monomer by applying energy. By adding such a liquid resin or monomer, it becomes easy to control the retention and storage modulus of the adhesive layer 110.

[0052] It is preferable that the adhesive layer 110 according to an embodiment contains a resin derived from an energy reactive liquid resin, since it is easy to maintain the uneven shape of the adhesive layer 110. An example of such a liquid resin is a diene rubber, and a specific example is a polybutadiene resin in which butadiene is used as a monomer.

[0053] The adhesive layer 110 according to another embodiment includes a combination of any resin and a resin derived from an energy reactive liquid resin or an energy reactive monomer. For example, the adhesive layer 110 may include an acrylic resin (A) and a resin derived from an energy reactive liquid resin or an energy reactive monomer. Even with such a combination, it is possible to easily maintain the formed uneven shape by forming unevenness on a film of a mixture of the acrylic resin (A) and the energy reactive liquid resin or the energy reactive monomer, and then imparting energy (for example, irradiating with energy rays) to polymerize the energy reactive liquid resin or the energy reactive monomer.

[0054] Examples of the energy reactive monomer include bifunctional or polyfunctional compounds having polymerizable functional groups such as alkenyl groups, such as vinyl and allyl groups, (meth)acryloyl groups, oxetanyl groups, and epoxy groups. A preferred example of the energy reactive monomer is a polyvalent (meth)acrylate such as a bifunctional (meth)acrylate. Thus, the adhesive layer 110 can include an energy ray curable resin containing a polyvalent (meth)acrylate as a constituent unit. A specific example of the polyvalent (meth)acrylate is a cycloalkyl di(meth)acrylate such as tricyclodecane dimethanol diacrylate.

[0055] The ratio of the energy reactive resin (B) to the total amount of components constituting the adhesive layer 110 can be selected according to the desired retention and storage modulus of the adhesive layer 110. For example, this ratio is preferably 1 mass % or more, more preferably 5 mass % or more, even more preferably 8 mass % or more, even more preferably 10 mass % or more, and is preferably 30 mass % or less, more preferably 25 mass % or less.

[0056] In addition, when the adhesive layer 110 contains an acrylic resin (A) and an energy reactive resin (B), the amount of the energy reactive resin relative to the acrylic resin can be selected according to the required retention and storage modulus of the adhesive layer 110. For example, the amount of the energy reactive resin relative to 100 parts by mass of the acrylic resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, particularly preferably 10 parts by mass or more, and preferably 30 parts by mass or less, more preferably 25 parts by mass or less. In this case, the energy reactive resin is, for example, an energy ray curable resin, for example, a resin derived from an energy ray curable monomer. Here, the parts by mass are based on the mass of the solid content, and hereinafter, unless otherwise specified, are also based on the mass.

[0057] (Other components of the adhesive layer) The adhesive composition forming the adhesive layer 110 may contain components other than the resin. For example, the adhesive composition may contain one or more of a crosslinking agent (C), a photopolymerization initiator (D), and other additives.

[0058] Examples of the crosslinking agent (C) include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, metal chelate-based crosslinking agents, etc. These crosslinking agents may be used alone or in combination of two or more.

[0059] Among these crosslinking agents, isocyanate-based crosslinking agents are preferred from the viewpoint of increasing the cohesive force to improve the adhesive force, ease of availability, etc. Examples of isocyanate-based crosslinking agents include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; alicyclic polyisocyanates such as dicyclohexylmethane-4,4'-diisocyanate, bicycloheptane triisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, methylene bis(cyclohexyl isocyanate), 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, and hydrogenated xylylene diisocyanate; and acyclic aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate; and other polyvalent isocyanate compounds. Further, examples of the isocyanate-based crosslinking agent include a trimethylolpropane adduct type modified product of the polyisocyanate compound, a biuret type modified product obtained by reacting the polyisocyanate compound with water, and an isocyanurate type modified product containing an isocyanurate ring.

[0060] The pressure-sensitive adhesive composition may contain one type of crosslinking agent, or may contain two or more types of crosslinking agents. From the viewpoint of carrying out a crosslinking reaction appropriately, the content of the crosslinking agent in the pressure-sensitive adhesive composition is preferably 0.01 mass% or more, more preferably 0.1 mass% or more, even more preferably 0.5 mass% or more, particularly preferably 0.8 mass% or more, and preferably 5 mass% or less, more preferably 4 mass% or less, even more preferably 2 mass% or less.

[0061] For example, the crosslinking agent may be a crosslinking agent for the acrylic resin (A). For example, an isocyanurate-type modified isocyanate crosslinking agent can be used as a crosslinking agent for an acrylic resin containing a monomer having a hydroxyl group as a constituent unit. In this case, the amount of the crosslinking agent relative to the acrylic resin can be selected so that the crosslinking reaction can be appropriately carried out. For example, the amount of the crosslinking agent relative to 100 parts by mass of the acrylic resin is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.5 parts by mass or more, particularly preferably 1.0 parts by mass or more, and is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 2 parts by mass or less.

[0062] The photopolymerization initiator (D) initiates a crosslinking reaction in response to the application of energy (e.g., irradiation with energy rays). When the pressure-sensitive adhesive composition contains an energy reactive resin (B), the crosslinking reaction proceeds even with the application of relatively low energy by further containing the photopolymerization initiator (D) in the pressure-sensitive adhesive layer 110.

[0063] Examples of the photopolymerization initiator (D) include 1-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0064] The pressure-sensitive adhesive composition may contain one type of polymerization initiator or may contain two or more types of polymerization initiators. The content of the photopolymerization initiator in the pressure-sensitive adhesive composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less.

[0065] Other additives that may be contained in the adhesive layer 110 include, but are not limited to, ultraviolet absorbers such as benzotriazole-based compounds, oxazolic acid amide compounds, or benzophenone-based compounds; light stabilizers such as hindered amine-based, benzophenone-based, or benzotriazole-based compounds; resin stabilizers such as imidazole-based resin stabilizers, dithiocarbamate-based resin stabilizers, phosphorus-based resin stabilizers, or sulfur ester-based resin stabilizers; antioxidants such as phenol-based compounds such as hindered phenol-based compounds, aromatic amine-based compounds, sulfur-based compounds, or phosphorus-based compounds such as phosphate ester-based compounds, fillers, pigments, extenders, and softeners.

[0066] When the adhesive layer 110 contains these additives, the content of the additives in the adhesive layer 110 is preferably 0.0001 mass% or more, more preferably 0.01 mass% or more, particularly preferably 0.1 mass% or more, even more preferably 1 mass% or more, and preferably 20 mass% or less, more preferably 10 mass% or less, even more preferably 5 mass% or less.

[0067] (Shape of adhesive layer) The surface of the adhesive layer 110 according to the present embodiment has projections and recesses. In one embodiment, the adhesive layer 110 has a surface including a plurality of projections spaced apart from one another and bounded by recesses. Each of the projections may be spaced apart by a recess that is continuous throughout the adhesive layer 110.

[0068] 2A-B are side views showing the shape of the adhesive layer 110, and Figs. 3A-C are top views showing the shape of the adhesive layer 110. Figs. 2A and 3A show an example of the adhesive layer 110 before expansion, and Figs. 2B and 3B show an example of the adhesive layer 110 after expansion. In addition, Figs. 2A-B depict the element 140 held by the convex portion 111 of the adhesive layer 110, while Figs. 3A-C omit the element 140 held by the convex portion 111.

[0069] As shown in Fig. 2A and Fig. 3A, the protrusions 111 may be regularly arranged on the surface of the adhesive layer 110. Regular arrangement of the protrusions means that the protrusions are lined up in a straight line at regular intervals. On the other hand, the protrusions 111 may be arranged so that the intervals between the protrusions vary regularly. For example, the intervals between the protrusions may be short in the center of the sheet and long in the peripheral part of the sheet. Furthermore, the protrusions may be irregularly arranged.

[0070] Fig. 3C is a top view showing another shape of the adhesive layer 110. As shown in Fig. 3C, stripe-shaped convex portions 111 may be provided on the surface of the adhesive layer 110. In Fig. 3C, line-shaped convex portions 111 having a certain width are arranged at certain intervals. The width or interval of the line-shaped convex portions 111 may vary regularly, or the line-shaped convex portions 111 may be arranged irregularly.

[0071] In this embodiment, the sheet is expanded, and the adhesive layer 110 shown in Figures 2A and 3A is transformed into the adhesive layer 110' shown in Figures 2B and 3B. Comparing the adhesive layer 110 and the adhesive layer 110', the pitch P of each protrusion 111 is enlarged in the adhesive layer 110' due to the expansion, and the number of protrusions 111 that hold one element 140 is reduced. As a result, in the adhesive layer 110', the force with which the protrusions 111 hold the element 140 is reduced compared to the adhesive layer 110.

[0072] The pitch P of the convex portion 111 before expansion is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and even more preferably 15 μm or more from the viewpoint of adjusting the holding force. On the other hand, the pitch P is preferably 100 μm or less, more preferably 75 μm or less, even more preferably 50 μm or less, even more preferably 35 μm or less, and even more preferably 25 μm or less from the viewpoint of increasing the contact area between the adhesive layer 110 and the element to increase the holding force. Here, the pitch P of the convex portion 111 means the distance between the center point of one arbitrarily selected convex portion 111 and the center point of another convex portion 111 closest to that convex portion 111. For example, in the case of FIG. 2A, the pitch P of the convex portion 111 represents the distance between the center point of the convex portion 111 on the straight line on which the convex portions 111 are arranged at regular intervals and the center point of another convex portion 111 closest to that convex portion 111. When the convex portions 111 are arranged on a plurality of straight lines, the pitch P represents the distance between the center points of the convex portions on the straight line on which the convex portions 111 are arranged at the shortest pitch. In this specification, the spacing between the convex portions 111 means the spacing between the centers of the convex portions.

[0073] The specific shape of the protrusions 111 is not particularly limited. For example, the protrusions 111 may have a pillar shape. As a specific example, the protrusions 111 may have a cylindrical shape or a prismatic shape. As described above, the protrusions 111 may extend in a line shape or may extend in a curved shape such as a wavy shape. Furthermore, these protrusions 111 may be tapered.

[0074] FIG. 4A shows a cross-sectional view of the adhesive layer 110 according to one embodiment, passing through the protruding portion 111 and perpendicular to the surface of the adhesive layer 110. The protruding portion 111 shown in FIG. 4A is tapered, that is, the protruding portion 111 is tapered. Also, as shown in FIG. 4B, the tip of the protruding portion 111 may be curved. With this configuration, the impact when the element is held by the adhesive layer 110 is further mitigated, so that the adhesive layer 110 can easily hold the element without shifting. On the other hand, the tip of the protruding portion may be flat.

[0075] 4A, the surface of the adhesive layer 110 may have flat recesses and protruding portions 111 protruding from the recesses. In this manner, the adhesive layer 110 has a plurality of protruding portions 111 that are spaced apart from one another and may be bounded by the recesses.

[0076] As another example, the convex portion may be hemispherical or a part of a sphere as shown in FIG. 4B. Also, the convex portion 111 may be T-shaped as shown in FIG. 4C. As yet another example, the convex portion 111 may be in the shape of a collection of multiple grains, a mushroom shape, the surface of a lotus leaf, or a needle shape. As yet another example, the surface of the adhesive layer 110 may be rough or fibrous, and such a surface may also be said to have projections and recesses.

[0077] From the viewpoint of maintaining the retention force of the element, the width or diameter of each protrusion 111 is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 5 μm or more, and even more preferably 10 μm or more. On the other hand, from the viewpoint of enhancing the ease of peeling off the element, the width or diameter is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, and even more preferably 20 μm or less. Here, the width and diameter of the protrusion 111 respectively mean the minimum distance and the maximum distance (represented by D in FIG. 4A) between two parallel lines contacting both sides of the protrusion 111 on the surface of the recess.

[0078] From the viewpoint of maintaining the element holding force, the area of ​​each protrusion 111 is preferably 10 μm 2 More preferably, 20 μm 2 More preferably, 30 μm or more 2 On the other hand, from the viewpoint of increasing the ease of peeling off the element, it is preferable that the thickness is 2000 μm. 2 Less than or equal to 1000 μm, more preferably 2 Less than 500 μm, more preferably 2 Here, the area of ​​the convex portion 111 means the area of ​​the portion protruding from the surface of the concave portion (the area of ​​a circle with a diameter D in the case of FIG. 4A).

[0079] In one embodiment, the height of each of the convex portions 111 is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more, from the viewpoint of increasing the ease of peeling of the element. On the other hand, from the viewpoint of increasing the morphological stability, the height of each of the convex portions 111 is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. This allows the element retention force to be changed. Here, the height of the convex portion 111 is represented by H in FIG. 4A. Also, in one embodiment, the height of the multiple convex portions of the adhesive layer 110 is uniform. In another embodiment, the adhesive layer 110 may have a first multiple convex portion having a first uniform height and a second multiple convex portion having a different height. Here, the second multiple convex portion may have a second uniform height. For example, the convex portion 111 may be composed of such a first convex portion and a second convex portion. In a further embodiment, the adhesive layer 110 may have multiple convex portions of random heights.

[0080] Moreover, the total area of ​​the protrusions 111 relative to the area of ​​the adhesive layer 110 is preferably 1% or more, more preferably 5% or more, even more preferably 10% or more, even more preferably 18% or more, and even more preferably 40% or more, from the viewpoint of maintaining the retention force of the element. On the other hand, the total area of ​​the protrusions relative to the area of ​​the adhesive layer 110 is preferably 95% or less, more preferably 75% or less, and even more preferably 60% or less, from the viewpoint of increasing the ease of peeling off the element.

[0081] The unevenness of the adhesive layer 110 may be designed according to the shape of the element held by the sheet. For example, the ratio of the adhesion area between the adhesive layer 110 and one element to the area of ​​one element is preferably 1% or more, more preferably 2% or more, more preferably 3% or more, more preferably 4% or more, more preferably 5% or more, more preferably 7% or more, and more preferably 10% or more, relative to 100% of the area of ​​one element, from the viewpoint of maintaining the holding force of the element. On the other hand, the ratio of the adhesion area between the adhesive layer 110 and one element to the area of ​​one element is preferably 95% or less, more preferably 70% or less, more preferably 50% or less, and more preferably 30% or less, from the viewpoint of increasing the ease of peeling of the element. In the case of FIG. 4A, the adhesion area corresponds to the area of ​​a circle with a diameter T. Note that the adhesion area may change when the holding position of the element on the sheet is shifted. In this case, it is preferable that the adhesion area ratio falls within the above range, regardless of the position of the object to be treated.

[0082] (Release sheet) 1, the element transfer sheet according to this embodiment may include a release sheet 150 that is in contact with the adhesive layer 110 and has an uneven surface complementary to the uneven surface of the adhesive layer 110. For the sake of explanation, FIG. 1 shows a state in which the adhesive layer 110 and the release sheet 150 are separated.

[0083] The release sheet 150 has a release layer 160. The release layer 160 is a layer that is easily peelable from the adhesive layer 110. The release layer 160 may have an uneven surface complementary to the uneven surface of the adhesive layer 110. That is, the release layer 160 has recesses 161, and the recesses 161 have a shape complementary to the protrusions 111. However, it is not essential that the recesses 161 have a shape complementary to the protrusions 111.

[0084] The release sheet 150 may include a substrate 170 on the surface not in contact with the adhesive layer 110. The substrate 170 may be designed similarly to the substrate 120, but does not need to have the same composition or structure as the substrate 120. For example, the material of the substrate 120 may be EMAA, and the material of the substrate 170 may be polyethylene terephthalate. The release sheet 150 may also include an undercoat layer (not shown) between the release layer 160 and the substrate 170.

[0085] (Other layers) The above-mentioned sheet may have a layer other than the substrate and the adhesive layer. For example, an additional adhesive layer may be provided on the surface of the substrate opposite to the adhesive layer. The sheet can be attached to another object via such an adhesive layer. The type of the additional adhesive layer is not particularly limited, and for example, the additional adhesive layer can be formed using a general adhesive.

[0086] (Characteristics of device transfer sheet) The adhesive strength of the element transfer sheet is preferably 1 mN / 50 mm or more, more preferably 5 mN / 50 mm or more, even more preferably 10 mN / 50 mm or more, even more preferably 15 mN / 50 mm or more, even more preferably 20 mN / 50 mm or more from the viewpoint of suppressing positional deviation when holding the element, and is preferably 1000 mN / 50 mm or less, more preferably 500 mN / 50 mm or less, even more preferably 100 mN / 50 mm or less, even more preferably 50 mN / 50 mm or less from the viewpoint of peeling off the held element from the adhesive layer 110 without damaging it. In this specification, the adhesive strength is measured as follows. That is, after cutting the element transfer sheet into a size of 200 mm in length x 50 mm in width, the surface of the adhesive layer is pressed onto the mirror surface of the mirror silicon wafer using a laminator. After pressing, the sheet is left to stand for 1 hour under an environment of 23 ° C. and 50% RH (relative humidity) to prepare an adhesive strength measurement sample. The adhesive strength of the adhesive strength test sample thus prepared is measured using a tensile tester (manufactured by A&D Co., Ltd., product name "Tensilon (registered trademark)") at an environment of 23°C and 50% RH (relative humidity) with a peel angle of 180° and a tensile speed of 300 mm / min, in accordance with JIS Z0237:2000, except for the measurement conditions mentioned above.

[0087] (Expansion of device transfer sheets) The expansion of the element transfer sheet will be described below. As described above, the element transfer sheet can be expanded in the planar direction while holding the element. The method of expanding the sheet is not particularly limited. For example, the sheet may be expanded in one direction, two directions, or multiple other directions.

[0088] The expansion rate of the element transfer sheet is not particularly limited. By increasing the amount of expansion, the spacing between the elements after expansion tends to become larger. For example, the expansion rate of the sheet in one direction may be 50% or more, 100% or more, 150% or more, or 250% or more. In addition, the expansion rate of the sheet in two mutually perpendicular directions may be 50% or more, at least 100% or more, 150% or more, or 250% or more.

[0089] As a specific example, the sheet can be expanded by fixing the sheet to a frame and pressing a base against the sheet in the frame. Such an example will be described with reference to Figs. 5A-B. Fig. 5A shows a state in which the sheet holds the elements 140a-140d. As shown in Fig. 5A, the outer periphery of the sheet can be fixed to a frame 320. The shape of the frame 320 is not particularly limited. For example, the frame 320 may be a circular or rectangular frame-shaped member having an opening. In one embodiment, a circular ring frame is used as the frame. By using the ring frame, the sheet can be expanded in all directions.

[0090] The sheet fixed to the frame 320 is brought into contact with the base 310, and the frame 320 is displaced (pulled down) toward the base 310 as shown in FIG. 5B, thereby expanding the sheet. As the sheet expands, the spacing between the elements 140a to 140d held by the sheet increases. The configuration of the base 310 is not particularly limited, and may have, for example, a cylindrical shape or a rectangular parallelepiped shape. The base 310 may be mesh-shaped or ring-shaped. The frame 320 may be displaced relative to the base 310 at a speed of, for example, 0.1 mm / sec or more, or 1 mm / sec or more. In this case, the displacement amount of the frame 320, i.e., the amount of pulling down, may be, for example, 20 mm or more, or 50 mm or more.

[0091] As described above, according to this embodiment, when the element transfer sheet is expanded while holding a plurality of elements, the interval between the elements is made larger. In one embodiment, a plurality of elements are formed by dicing the wafer substrate held by the adhesive layer 110. After that, when the element transfer sheet is expanded by 80 mm in the first direction and the second direction perpendicular to each other, the average value of the interval between the plurality of elements is preferably 2.5 mm or more, more preferably 3.0 mm or more, even more preferably 3.5 mm or more, even more preferably 4.0 mm or more, and particularly preferably 5.0 mm or more. Here, the interval between the plurality of elements refers to the distance between adjacent elements. In addition, the average value of the interval between the plurality of elements corresponds to the average value for a data group including the interval between all pairs of elements adjacent to each other in the first direction and the interval between all pairs of elements adjacent to each other in the second direction.

[0092] As a specific example, by pulling down the frame 320 by 80 mm with respect to the base 310, the element transfer sheet can be expanded by 80 mm in the first direction and the second direction perpendicular to each other. For such measurements, a ring frame with an inner diameter of 194 mm can be used as the frame 320. Also, a cylindrical member having a diameter slightly smaller than the inner diameter of the frame 320 can be used as the base 310. As described above, the transfer sheet can be expanded by 80 mm in the first direction and the second direction perpendicular to each other by pulling down the frame 320 by 80 mm with respect to the base 310. In this case, the element transfer sheet can be expanded by about 180% ((194+80+80) / 194=about 180%).

[0093] Furthermore, according to this embodiment, when the element transfer sheet is expanded while holding multiple elements, the spacing between the elements becomes more uniform. In one embodiment, multiple elements are formed by dicing the wafer substrate held by the adhesive layer 110. Thereafter, when the element transfer sheet is expanded by 180% in a first direction and a second direction perpendicular to each other, the coefficient of variation of the spacing between the multiple elements is preferably 0.20 or less, and more preferably 0.15 or less. Here, the coefficient of variation is Standard deviation / mean The average value of the spacing between the multiple elements is defined as above. The standard deviation of the spacing between the multiple elements corresponds to the standard deviation for a data set including the spacing between all pairs of adjacent elements in the first direction and the spacing between all pairs of adjacent elements in the second direction. In such measurements, as described above, frame 320 with an inner diameter of 194 mm can be expanded by approximately 180% by pulling it down 80 mm relative to base 310.

[0094] (Method of manufacturing adhesive layer and sheet) There is no particular limitation on the manufacturing method of the adhesive layer and the sheet. For example, a sheet having an adhesive layer 110 provided on a substrate 120 can be manufactured as follows. First, an organic solvent is added to a raw material composition containing each component of the adhesive layer 110 described above to prepare a solution of the raw material composition. Then, this solution is applied onto the substrate 120 to form a coating film, and then the solution is dried to provide an adhesive layer on the substrate 120. Furthermore, a treatment is performed to provide irregularities on the surface of the adhesive layer, thereby forming an adhesive layer 110 having irregularities.

[0095] Examples of organic solvents used to prepare the solution of the raw material composition include toluene, ethyl acetate, and methyl ethyl ketone, etc. Examples of the solution application method include spin coating, spray coating, bar coating, knife coating, roll coating, roll knife coating, blade coating, die coating, gravure coating, and printing methods (e.g., screen printing and inkjet printing).

[0096] There is no particular limitation on the process of providing the unevenness on the surface of the adhesive layer 110. For example, the unevenness can be provided on the surface of the adhesive layer 110 by using an imprinting method. In the imprinting method, a mold having a shape on its surface that is complementary to the unevenness to be provided can be used. Specifically, the unevenness can be provided on the surface of the adhesive layer by heating the adhesive layer while pressing the adhesive layer provided on the substrate with the mold. As a more specific method, the adhesive layer can be pressed with the mold, heated and maintained for a predetermined time, and then cooled and the mold can be removed. When heating the adhesive layer, for example, the adhesive layer can be heated to a temperature higher than the softening point of the adhesive layer. In addition, the time for maintaining the adhesive layer in the heated state is not particularly limited, but may be maintained for 10 seconds or more, or may be maintained for 10 minutes or less. As a specific method for heating the adhesive layer while pressing the adhesive layer with the mold, a method of vacuum laminating the adhesive layer provided on the substrate and the mold can be mentioned. Instead of performing the two-step process of forming the adhesive layer and forming the unevenness, an adhesive layer having an uneven surface may be formed on a substrate in a single step. Also, the release sheet 150 having the release layer 160 having the unevenness as described above may be used as a mold.

[0097] Alternatively, the adhesive layer 110 having a rough surface can be provided by spraying a solution of the raw material composition. Furthermore, the adhesive layer 110 having a rough or fibrous surface can be provided by adding a filler to the solution of the raw material composition and applying such a solution. As yet another method, the adhesive layer 110 having a concave-convex shape can be provided directly on the substrate 120 by applying the solution of the raw material composition according to a desired pattern using a printing method such as an inkjet method.

[0098] (How to use the device transfer sheet) The sheet according to the present embodiment can be used to transfer elements. As a specific example, the sheet according to the present embodiment can be used to transfer semiconductor chips obtained by dicing to desired positions. The method for transferring elements using the sheet according to the present embodiment will be described with reference to the flow chart of FIG. 6.

[0099] (S10: Retaining the element) In S10, the element is held in the adhesive layer of the element transfer sheet according to the present embodiment. The type of element is not particularly limited. The element may be, for example, a semiconductor chip such as an LED chip, a semiconductor chip with a protective film, or a semiconductor chip with a die attach film (DAF). The element may be a micro light-emitting diode, a mini light-emitting diode, a power device, a MEMS (Micro Electro Mechanical Systems), or a controller chip, or may be a component thereof. The element may be an individualized object such as a wafer, a panel, or a substrate. The element may have a circuit surface on which an integrated circuit having circuit elements such as a transistor, a resistor, and a capacitor is formed. The element is not necessarily limited to an individualized object, and may be various wafers or various substrates that are not individualized.

[0100] The size of the element is not particularly limited. The size of the element is preferably 100 μm, for example. 2 More preferably, 500 μm 2 More preferably, 1000 μm or more 2 On the other hand, the size of the element is preferably 100 mm 2 Less than or equal to 25mm, preferably 2 Less than 1 mm, more preferably 2 It may be the following.

[0101] Examples of the wafer include semiconductor wafers such as silicon wafers, silicon carbide (SiC) wafers, and compound semiconductor wafers (e.g., gallium phosphide (GaP) wafers, gallium arsenide (GaAs) wafers, indium phosphide (InP) wafers, and gallium nitride (GaN) wafers). The size of the wafer is not particularly limited, but is preferably 6 inches (diameter about 150 mm) or more, and more preferably 12 inches (diameter about 300 mm) or more. The shape of the wafer is not limited to a circle, and may be an angular shape such as a square or a rectangle.

[0102] The panel may be a fan-out type semiconductor package (e.g., FOWLP or FOPLP). That is, the workpiece may be a semiconductor package before or after singulation in a fan-out type semiconductor package manufacturing technique. The size of the panel is not particularly limited, but may be, for example, a square substrate of about 300 to 700 mm.

[0103] The substrate may be a glass substrate, a sapphire substrate, a compound semiconductor substrate, or the like.

[0104] In one embodiment, the elements are transferred from the holding substrate to the element transfer sheet, and the element transfer sheet holds the transferred elements. For example, a semiconductor wafer can be attached onto a wafer substrate, and the semiconductor wafer can be diced. Then, the elements on the wafer substrate obtained by dicing can be brought into close contact with the adhesive layer 110 of the element transfer sheet. Then, an external stimulus such as a laser beam can be applied to reduce the adhesiveness between the wafer substrate and the elements. Through such a process, the elements can be transferred from the wafer substrate to the semiconductor transfer sheet. As another method, the elements obtained by dicing the semiconductor wafer can be transferred to a holding substrate to obtain a holding substrate to which the elements are attached. Then, the elements attached to the holding substrate can be transferred to the adhesive layer 110 of the element transfer sheet in a similar manner.

[0105] In another embodiment, an external stimulus may be used to separate an element attached to a holding substrate from the holding substrate. Specifically, the element moves away from the holding substrate. Also, the element moves closer to the element transfer sheet. Then, the element comes into contact with the adhesive layer 110 of the sheet, and the element is separated from the holding substrate and captured by the sheet. The type of external stimulus is not particularly limited, but examples include energy application, cooling, expansion of the holding substrate, and physical stimulus (for example, pressing the rear surface of the holding substrate with a pin, etc.). By using one or more of these external stimuli, the bonding force between the holding substrate and the element can be reduced, and the element can be separated from the holding substrate. For example, the element can be separated from the holding substrate by irradiation with laser light (laser lift-off method). In such an embodiment, when the separated element approaches the adhesive layer 110, pressure is generated between the element and the adhesive layer 110. However, since the surface of the adhesive layer 110 has an uneven surface, the pressure generated between the element and the adhesive layer 110 is alleviated, making it easier to capture the element at a desired position on the sheet.

[0106] In a further embodiment, a semiconductor wafer is attached to the adhesive layer 110 of the element transfer sheet. Then, elements are formed by dicing the semiconductor wafer on the adhesive layer 110. This method also allows the element transfer sheet to hold elements.

[0107] (S20: Expansion of element transfer sheet) In S20, the element transfer sheet is expanded in the surface direction. By expanding the sheet, the interval between the elements becomes larger. This makes it easier to handle the elements in the next step. In one embodiment, the element retention force is reduced by expanding the sheet, making it easier to peel off the elements in the next step. The specific method for expanding the sheet is as described above.

[0108] (S30: Peeling off of element) In S30, the element is peeled off from the adhesive layer 110 of the element transfer sheet. In this embodiment, the element is peeled off from the adhesive layer 110 of the element transfer sheet expanded in the surface direction. The method of peeling off the element is not particularly limited. For example, the above-mentioned method can be used as a method of transferring the element attached to the holding substrate to the element transfer sheet. Specifically, the element can be moved to the transfer destination by bringing the transfer destination substrate or sheet close to the surface of the element and pressing the surface of the sheet opposite to the element using a pin or the like. As another method, specifically, the element can be peeled off from the adhesive layer 110 of the sheet using an adsorption member such as a vacuum chuck and moved to a desired position of the transfer destination. When the holding force of the adhesive layer 110 is reduced by expanding the sheet, the element may be peeled off from the adhesive layer 110 of the sheet without applying a physical stimulus from the opposite surface of the adhesive layer 110 of the sheet. Furthermore, the adhesiveness between the element transfer sheet and the element may be reduced by closely contacting the element held on the element transfer sheet and the transfer destination substrate or sheet and further applying an external stimulus such as laser light. This method also allows the elements to be transferred from the element transfer sheet to the transfer destination. In this case, the relative arrangement of the elements before the element transfer sheet is expanded changes from the relative arrangement of the elements at the transfer destination.

[0109] By such a procedure, the element can be transferred to any desired destination by using the element transfer sheet. In addition, by using such a transfer method, electronic components or semiconductor devices having elements can be manufactured. The element held by the element transfer sheet may be treated or processed. EXAMPLES

[0110] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples. In each example, parts and percentages are based on the mass of the solid content unless otherwise specified.

[0111] The following compounds were used in the examples and comparative examples. <Component (A): Acrylic resin> As the acrylic resin, an acrylic copolymer (monomer mass ratio: 2-ethylhexyl acrylate / 2-hydroxyethyl acrylate / acrylic acid=92.8 / 7.0 / 0.2, mass average molecular weight (Mw): 1.1 million) was used.

[0112] <(B) Component: Energy reactive resin> As the energy reactive resin, tricyclodecane dimethanol diacrylate was used.

[0113] <Component (C): Crosslinking agent> As the crosslinking agent, an isocyanurate type polyisocyanate derived from hexamethylene diisocyanate was used.

[0114] <Component (D): Photopolymerization initiator> As the photopolymerization initiator, 2,4,6-trimethylbenzoyldiphenylphosphine oxide was used.

[0115] <Evaluation of tensile stress of substrate> The tensile stress of the substrate used in each example was evaluated as follows. A substrate cut to 150 mm in MD direction × 15 mm in TD direction was used as a test sample. The tensile stress of this test sample was measured in an environment of 23 ° C. and 50% RH (relative humidity) in accordance with JIS K 7161-1: 2014 and JIS K 7127: 1999. A tensile tester (manufactured by Shimadzu Corporation, product name "Autograph (registered trademark) AG-IS 500N") was used for the measurement. Specifically, after setting the chuck distance to 100 mm, a tensile test was performed on the test sample at a speed of 200 mm / min to measure the tensile stress (MPa) in the MD direction at 100% elongation of the support. In addition, a similar test was performed using a substrate cut to 150 mm in TD direction × 15 mm in MD direction as a test sample, and the tensile stress (MPa) in the TD direction at 100% elongation of the support was measured.

[0116] <Extended Test> The expansion test of the sheet obtained in each example was carried out as follows: First, the adhesive layer of the sheet obtained in each example was attached to a ring frame (made of stainless steel, inner diameter 194 mm), and the sheet was cut to fit the outer diameter of the ring frame.

[0117] Next, a wafer substrate (mirror silicon wafer, 6 inches, thickness 150 μm) was fixed to a dicing tape prepared separately. Then, the wafer substrate was diced into 10 mm×10 mm squares to obtain a plurality of elements (silicon chips, element size 10 mm×10 mm×150 μm). The obtained plurality of elements were attached to the adhesive layer of the sheet at the center part inside the ring frame so that the mirror surface was attached to the adhesive layer. The attachment was performed by lamination at room temperature (23° C.). Then, the dicing tape was peeled off to transfer the plurality of elements from the dicing tape to the sheet. In this way, a sheet on which a plurality of elements was placed and supported by a ring frame was obtained as an evaluation sample.

[0118] The obtained evaluation sample was placed in an expanding device shown in FIG. 5A. With the element supported by the base 310 through the sheet, the ring frame 320 was pressed down at a speed of 1 mm / sec and a drop of 80 mm. After pressing down, the intervals (vertical and horizontal) of each chip were measured using a digital microscope. Here, the intervals of each chip refer to the distance between adjacent chips. Based on the intervals of each chip thus measured, the average value and the coefficient of variation of the intervals of each chip were calculated. The average value and the coefficient of variation of the intervals of multiple chips correspond to the average value and the coefficient of variation of a data group including the intervals for all pairs of adjacent chips in the first direction and the intervals for all pairs of adjacent chips in the second direction.

[0119] Example 1 An adhesive composition was prepared by dissolving 100 parts by weight of acrylic resin (A), 25 parts by weight of energy reactive resin (B), 1.25 parts by weight of crosslinking agent (C), and 0.75 parts by weight of photopolymerization initiator (D) in toluene. This adhesive composition was applied onto the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name: SP-PET382150, a polyethylene terephthalate film laminated with a silicone-based release agent, thickness 38 μm), and the resulting coating was dried at 100 ° C for 2 minutes to form an adhesive layer with a thickness of 25 μm. The storage modulus of the resulting adhesive layer was 2.04 MPa.

[0120] Onto this adhesive layer, a PVC film (containing 35 parts by mass of di(2-ethylhexyl)phthalate as a plasticizer per 100 parts by mass of vinyl chloride copolymer, thickness 80 μm) was attached as a substrate. The tensile modulus and breaking elongation (TD and MD) of the substrate are shown in Figure 1.

[0121] After the release sheet was peeled off, the adhesive layer was attached to a replica mold in which a concave shape had been formed in advance, and vacuum laminated at 60° C. for 300 seconds. Next, an ultraviolet irradiator (Heraeus) was used to irradiate the adhesive layer with an illuminance of 200 mW / cm 2 , light intensity 800mJ / cm 2 A sheet having an uneven surface was produced by irradiating ultraviolet light at 1000 nm. The uneven surface of the adhesive layer of the sheet had pillars arranged in a lattice pattern, similar to that of FIG. 2A. The pitch P between the pillars in the sheet was 20 μm. As shown in FIG. 4A, the height (H) of each pillar was 8 μm, the diameter (T) of the tip was 8 μm, and the diameter (D) of the base was 16 μm. The ratio of the area of ​​the adhesive layer and the area of ​​the captured element (i.e., the area of ​​the tip of the convex portion) to the area of ​​the sheet was approximately 12.6%. The replica mold used had a surface shape complementary to the uneven surface.

[0122] The sheet thus obtained was subjected to the expansion test as described above. The obtained average value and coefficient of variation of the tip spacing are shown in Table 1. Table 1 also shows the evaluation results of the expansion test, which were evaluated based on the size of the tip spacing and the variation in the tip spacing. In Table 1, "A" indicates that the evaluation result was good, and "F" indicates that the evaluation result was not good.

[0123] Example 2 A sheet was produced in the same manner as in Example 1, except that an EMAA film (ethylene-methacrylic acid copolymer film, acid content 9% by mass, one surface of which was embossed to give a matte finish, thickness 80 μm) was used as the substrate, and the non-embossed surface of the EMAA film was attached onto the adhesive layer. The adhesive strength of the sheet in Example 2 was 23.5 mN / 50 mm.

[0124] Example 3 A sheet was produced in the same manner as in Example 1, except that a PO film (ethylene-block propylene copolymer, thickness 110 μm) was used as the substrate.

[0125] Comparative Example 1 A sheet was produced in the same manner as in Example 1, except that an LDPE film (amorphous low-density polyethylene, thickness 70 μm) was used as the substrate.

[0126] [Table 1]

[0127] As can be seen from the comparison between Examples 1 to 3 and Comparative Example 1, when the tensile stress in the first direction (e.g., MD direction) at 100% elongation of the substrate is 12 MPa or more and the tensile stress in the second direction (e.g., TD direction) is 9 MPa or more, the chip spacing becomes large and the variation in the chip spacing becomes small, and a good evaluation result was obtained. In particular, when the tensile stress in the first direction is 18 MPa or more and the tensile stress in the second direction is 12 MPa or more as in Example 1, the chip spacing becomes large and the variation in the chip spacing becomes particularly small, and a particularly good evaluation result was obtained. Also, when the tensile stress in the first direction is 12 MPa or more and 16 MPa or less and the tensile stress in the second direction is 9 MPa or more and 12 MPa or less as in Example 3, the chip spacing becomes particularly large and the variation in the chip spacing becomes small, and a particularly good evaluation result was obtained.

[0128] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention.

[0129] This application claims priority based on Japanese Patent Application No. 2022-151756 filed on September 22, 2022, Japanese Patent Application No. 2022-151757 filed on September 22, 2022, Japanese Patent Application No. 2023-058459 filed on March 31, 2023, Japanese Patent Application No. 2023-058460 filed on March 31, 2023, Japanese Patent Application No. 2023-058462 filed on March 31, 2023, and Japanese Patent Application No. 2023-058463 filed on March 31, 2023, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0130] 110: adhesive layer, 120: substrate, 111: protrusion, 140: element, 150: release sheet, 160: release layer, 161: recess, 170: substrate, P: pitch

Claims

1. A sheet for element transfer comprising a substrate and an adhesive layer having an uneven surface, The tensile stress in a first direction at 100% elongation of the base material is higher than the tensile stress in a second direction perpendicular to the first direction, the tensile stress in the first direction being 12 MPa or more, and the tensile stress in the second direction being 9 MPa or more; An element transfer sheet, in which after a wafer substrate held on the adhesive layer is diced to form a plurality of elements, the coefficient of variation of the spacing between the plurality of elements is 0.2 or less when the element transfer sheet is expanded by 180% in the first direction and the second direction.

2. 2. The element transfer sheet according to claim 1, wherein the tensile stress in the first direction is 40 MPa or less, and the tensile stress in the second direction is 30 MPa or less.

3. 2. The element transfer sheet according to claim 1, wherein the substrate has a tensile modulus of elasticity of 2500 MPa or less.

4. 2. The element transfer sheet according to claim 1, wherein the substrate has a breaking elongation of 200% or more.

5. 2. The element transfer sheet according to claim 1, wherein the substrate is a polyolefin film or a vinyl chloride copolymer film.

6. 2. The element transfer sheet according to claim 1, wherein the adhesive layer has a plurality of convex portions spaced apart from one another and bounded by concave portions, the plurality of convex portions having a pitch of 1 μm or more and 100 μm or less.

7. The element transfer sheet according to claim 1 , wherein the adhesive layer has a plurality of convex portions, the heights of the plurality of convex portions being uniform.

8. 2. The element transfer sheet of claim 1, wherein after forming a plurality of elements by dicing a wafer substrate held by the adhesive layer, the average spacing between the plurality of elements is 1 mm or more when the element transfer sheet is expanded 80 mm in the first direction and the second direction.

Images