Adhesive sheet for semiconductor processing and method for manufacturing semiconductor device

Abstract

A semiconductor processing adhesive sheet having a surface coating layer, a buffer layer, a base material and an adhesive layer, in this order, wherein the static contact angle of a water at 23°c relative to the surface coating layer is 85° or more; and a method for manufacturing a semiconductor device using said semiconductor processing adhesive sheet.

Description

[Technical Field]

[0001] The present invention relates to an adhesive sheet for semiconductor processing and a method for manufacturing a semiconductor device. [Background technology]

[0002] 2. Description of the Related Art As information terminal devices are rapidly becoming thinner, smaller, and more multifunctional, semiconductor devices mounted on these devices are also being required to be thinner and more dense. A method for thinning semiconductor devices has been to grind the backside of the semiconductor wafer used in the semiconductor device. The backside grinding of the semiconductor wafer is performed by attaching an adhesive sheet for backside grinding (hereinafter also referred to as a "backgrinding sheet") to the front side of the semiconductor wafer, protecting the front side of the semiconductor wafer with the sheet. After backside grinding, the backgrinding sheet is peeled off and removed from the front side of the semiconductor wafer.

[0003] In recent years, grinding and singulation methods such as the front-end dicing method and the stealth front-end dicing method have been put into practical use as grinding and singulation methods for thinning semiconductor chips while suppressing damage to them. The front-end dicing method involves forming grooves of a predetermined depth on the surface of a semiconductor wafer using a dicing blade or the like, and then grinding the semiconductor wafer from the back side down to the grooves to singulate the semiconductor chips. The stealth front-end dicing method involves forming modified regions within the semiconductor wafer by irradiating it with laser light, then grinding the semiconductor wafer from the back side and cleaving the modified regions as starting points to singulate the semiconductor chips. These methods also use a backgrinding sheet to protect the surface of the semiconductor wafer.

[0004] Along with the development of these thinning process technologies, back grinding sheets are also being required to have the functionality to thin semiconductor chips with good yield, and various studies are being conducted. Patent Document 1 discloses an adhesive sheet for protecting the surface of a semiconductor wafer that can be used in a dicing-first method or a stealth dicing-first method, the adhesive sheet having a base film, an intermediate layer made of an adhesive and provided on at least one side of the base film, and an outermost adhesive layer provided on the opposite side of the intermediate layer from the base film as the outermost layer, wherein the intermediate layer is formed from a material that hardens when subjected to a curing treatment after the adhesive sheet is formed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-56446 Summary of the Invention [Problem to be solved by the invention]

[0006] The adhesive sheet for protecting the surface of semiconductor wafers in Patent Document 1 is said to be able to suppress kerf shift, which is a disruption of the original chip spacing after the semiconductor wafer is diced into chips, as well as to suppress contamination by grinding debris from the semiconductor wafer, and to prevent adhesive residue on the chips when the surface protection tape is peeled off.

[0007] When grinding the backside, the backgrind sheet attached to the semiconductor wafer is fixed by a support device such as a chuck table on the side opposite to the side attached to the semiconductor wafer (hereinafter also referred to as the "backside").The semiconductor wafer fixed on the table of the support device via the backgrind sheet is ground on the backside while cooling water is supplied to the grinding surface to remove heat and grinding debris caused by grinding.

[0008] If grinding debris exists between the backgrinding sheet and the table of the support device during backgrinding, cracks may occur in the semiconductor wafer or semiconductor chip, starting from the area where the grinding debris exists, due to the impact when the semiconductor wafer is fixed to the table, the pressure and vibration during backgrinding, etc. Since the grinding debris adheres to the back surface of the backgrinding sheet while being contained in the cooling water, in order to prevent the occurrence of such cracks, it is necessary to reduce the amount of grinding debris adhering to the back surface of the backgrinding sheet. The adhesive sheet for protecting the surface of a semiconductor wafer disclosed in Patent Document 1 does not adequately meet the demand for reducing the amount of grinding debris that adheres to the back surface of a back-grinding sheet.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an adhesive sheet for semiconductor processing that reduces the amount of grinding debris that adheres to the sheet, and a method for manufacturing a semiconductor device using the adhesive sheet for semiconductor processing. [Means for solving the problem]

[0010] After extensive research, the inventors discovered that the above-mentioned problems can be solved by an adhesive sheet for semiconductor processing having, in this order, a surface coating layer, a buffer layer, a substrate, and an adhesive layer, each of which has a static contact angle of water at 23°C within a specific range, and thus completed the present invention as described below.

[0011] That is, the present invention relates to the following [1] to

[11] . [1] A surface coating layer, a buffer layer, a substrate, and a pressure-sensitive adhesive layer, in this order; The adhesive sheet for semiconductor processing, wherein the static contact angle of water at 23°C with the surface coating layer is 85° or more. [2] The adhesive sheet for semiconductor processing according to [1] above, wherein the surface coating layer is an organic layer containing a resin component. [3] The adhesive sheet for semiconductor processing according to [2] above, wherein the resin component is a thermoplastic resin. [4] The adhesive sheet for semiconductor processing according to the above [2] or [3], wherein the resin component has a heteroatom content of 7 mass % or less. [5] The adhesive sheet for semiconductor processing according to any one of the above [2] to [4], wherein the resin component is soluble in toluene at 23°C in an amount of 1 mass % or more. [6] The pressure-sensitive adhesive sheet for semiconductor processing according to any one of the above [1] to [5], wherein the static contact angle of water at 23° C. with the surface coating layer is 90° or more. [7] The adhesive sheet for semiconductor processing according to any one of the above [1] to [6], wherein the surface coating layer has a thickness of 0.05 to 10 μm. [8] The adhesive sheet for semiconductor processing according to any one of the above [1] to [7], wherein the buffer layer is formed from a buffer layer-forming composition containing urethane (meth)acrylate. [9] The adhesive sheet for semiconductor processing according to any one of the above [1] to [8], which is used for back grinding of semiconductor wafers.

[10] A step of attaching the semiconductor processing adhesive sheet according to any one of the above [1] to [9] to the surface of a semiconductor wafer with the adhesive layer as an attachment surface; grinding the back surface of the semiconductor wafer while the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer is fixed by a supporting device; A method for manufacturing a semiconductor device, comprising:

[11] A dividing line forming step, which is a step a of forming grooves on the surface of a semiconductor wafer, or a step b of forming modified regions inside the semiconductor wafer from the surface or back surface of the semiconductor wafer; a sheet sticking step of sticking the semiconductor processing adhesive sheet according to any one of [1] to [9] above to the surface of the semiconductor wafer with the adhesive layer as an attachment surface after the step a, or before or after the step b; a grinding and singulating step of grinding the back surface of the semiconductor wafer while the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer is fixed by a supporting device, and singulating the semiconductor wafer into a plurality of semiconductor chips starting from the grooves or modified regions; The method for manufacturing the semiconductor device according to

[10] above, comprising: [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an adhesive sheet for semiconductor processing with reduced adhesion of grinding dust, and a method for manufacturing a semiconductor device using the adhesive sheet for semiconductor processing. DETAILED DESCRIPTION OF THE INVENTION

[0013] In this specification, the lower and upper limits of preferred numerical ranges described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60."

[0014] In this specification, for example, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid," and the same applies to other similar terms.

[0015] In this specification, the term "energy rays" refers to electromagnetic waves or charged particle beams that have an energy quantum, and examples thereof include ultraviolet rays, radioactive rays, and electron beams. Ultraviolet rays can be irradiated using, for example, an electrodeless lamp, a high-pressure mercury lamp, a metal halide lamp, a UV-LED, or the like as an ultraviolet light source. Electron beams can be irradiated using those generated by an electron beam accelerator, or the like. In this specification, "energy ray polymerizable" means a property of polymerizing by irradiation with energy rays, "energy ray curable" means a property of curing by irradiation with energy rays, and "non-energy ray curable" means a property of not having energy ray curability.

[0016] In this specification, the "front surface" of a semiconductor wafer refers to the surface on which circuits are formed, and the "back surface" refers to the surface on which circuits are not formed.

[0017] The mechanism of action described in this specification is speculation and does not limit the mechanism by which the adhesive sheet for semiconductor processing of the present invention exerts its effects.

[0018] [Adhesive sheets for semiconductor processing] The adhesive sheet for semiconductor processing of this embodiment (hereinafter also referred to as "adhesive sheet") has a surface coating layer, a buffer layer, a base material, and an adhesive layer in this order, and the static contact angle of water with the surface coating layer at 23°C is 85° or more. The adhesive sheet of this embodiment is attached to the surface of a semiconductor device, which is a workpiece, and is used to perform a predetermined processing on the semiconductor device while protecting the surface. After the predetermined processing is performed on the workpiece, the adhesive sheet of this embodiment is peeled off and removed from the semiconductor device. In this embodiment, the term "semiconductor device" refers to any device that can function by utilizing semiconductor properties, such as a semiconductor wafer, a semiconductor chip, an electronic component including the semiconductor chip, or an electronic device including the electronic component. Of these, the pressure-sensitive adhesive sheet of this embodiment is suitable for processing semiconductor wafers.

[0019] The pressure-sensitive adhesive sheet of the present embodiment may or may not have layers other than the surface coating layer, buffer layer, substrate, and pressure-sensitive adhesive layer. Examples of layers other than the substrate and pressure-sensitive adhesive layer include an intermediate layer provided between the substrate and the pressure-sensitive adhesive layer, and a release sheet provided on the surface of the pressure-sensitive adhesive layer opposite the substrate. Hereinafter, each of the components constituting the pressure-sensitive adhesive sheet of this embodiment will be described in order.

[0020] <Surface coating layer> The surface coating layer is a layer provided on the surface of the buffer layer opposite to the substrate, and is a layer that is fixed by a support device when processing the semiconductor device.

[0021] (contact angle) The surface coating layer has a static contact angle with water at 23°C (hereinafter simply referred to as "water contact angle") of 85° or more, making it difficult for water containing grinding dust to adhere to it. Therefore, the pressure-sensitive adhesive sheet of this embodiment has a reduced amount of grinding dust adhering to its back surface, making it possible to suppress damage to the workpiece caused by grinding dust adhering to the back surface. The water contact angle of the surface coating layer is preferably 90° or more, more preferably 93° or more, and even more preferably 96° or more, from the viewpoint of further reducing the amount of adhesion of grinding dust. The upper limit of the water contact angle of the surface coating layer is not particularly limited, but from the viewpoint of ease of production, etc., it may be, for example, 150° or less, or 100° or less. The water contact angle of the surface coating layer is a value measured in accordance with JIS R 3257:1999, and specifically, can be measured by the method described in the examples.

[0022] The surface coating layer is not particularly limited as long as it has a water contact angle of 85° or more, and may be either an inorganic layer or an organic layer, but from the viewpoint of productivity and handleability of the pressure-sensitive adhesive sheet, an organic layer is preferred.

[0023] The organic layer is preferably a layer containing a resin component, and the resin component contained in the organic layer is preferably a thermoplastic resin, more preferably a polyolefin resin, from the viewpoint of ease of adjusting the water contact angle to 85° or more.

[0024] (Heteroatom content of resin component) The content of heteroatoms in the resin component contained in the organic layer is not particularly limited, but is preferably 7% by mass or less, more preferably 0.2 to 4% by mass, and even more preferably 0.5 to 1% by mass. When the content of heteroatoms in the resin component is equal to or less than the upper limit, the amount of grinding debris tends to be reduced. When the content of heteroatoms in the resin component is equal to or greater than the lower limit, the solvent solubility of the resin component is improved, which tends to facilitate the formation of a surface coating layer by applying the resin component. In this specification, the term "heteroatom" refers to all atoms other than carbon atoms and hydrogen atoms.

[0025] (Solubility of resin components in solvents) The resin component contained in the organic layer is preferably soluble in an organic solvent, from the viewpoint of facilitating the formation of a surface coating layer by coating. Specifically, the resin component is preferably soluble in toluene at 23° C. in an amount of 1% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more.

[0026] A preferred embodiment of the surface coating layer containing a polyolefin resin as the resin component will be described in detail below.

[0027] (Polyolefin resin) The polyolefin resin contained in the surface coating layer is a resin obtained by polymerizing a monomer containing at least an olefin. Here, the term "polyolefin resin" in this embodiment means either a resin obtained by homopolymerizing an olefin or a resin obtained by copolymerizing an olefin with a monomer other than an olefin, and containing 50% by mass or more of structural units derived from an olefin. Furthermore, the term "olefin" in this embodiment refers to an unsaturated hydrocarbon having an ethylenically unsaturated bond, and compounds containing heteroatoms are not included in the term "olefin" in this embodiment. In addition, the term "ethylenically unsaturated bond" in this embodiment means a carbon-carbon double bond capable of undergoing an addition reaction, and does not include a double bond in an aromatic ring. In the following description, a group containing an ethylenically unsaturated bond may be simply referred to as an "unsaturated group." The polyolefin resin may be used alone or in combination of two or more kinds.

[0028] The content of the olefin-derived structural unit in the polyolefin-based resin is not particularly limited, but is preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. When the content of the olefin-derived structural unit in the polyolefin-based resin is equal to or greater than the above lower limit, the amount of grinding dust adhesion tends to be further reduced. The content of olefin-derived structural units in the polyolefin-based resin may be 100% by mass, but is preferably 99.5% by mass or less, more preferably 99% by mass or less. When the content of olefin-derived structural units in the polyolefin-based resin is the above-mentioned upper limit or less, structural units derived from monomers other than olefins can be contained for the purpose of improving solvent solubility, etc., and the formation of a surface coating layer by coating tends to be easier.

[0029] Examples of olefins constituting polyolefin-based resins include chain olefins, cyclic olefins, and aromatic vinyl compounds. The olefins constituting the polyolefin-based resin may be used alone or in combination of two or more.

[0030] Examples of the chain olefin include chain monoolefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, and 5-methyl-1-hexene; chain non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, and 5-methyl-1,4-hexadiene; and chain conjugated dienes such as 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene. Among these, chain olefins having 2 to 6 carbon atoms are preferred, and ethylene and propylene are more preferred.

[0031] Examples of cyclic olefins include cyclic monoolefins such as cyclobutene, cyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, cycloheptene, and cyclooctene; cyclic diolefins such as cyclohexadiene, methylcyclohexadiene, cyclooctadiene, methylcyclooctadiene, and phenylcyclooctadiene; and polycyclic olefins such as norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, and tetracyclo[7.4.0.110,13.02,7]trideca-2,4,6,11-tetraene. Among these, tetracyclododecene is preferred from the viewpoint of improving solvent solubility and facilitating the formation of a surface coating layer by coating.

[0032] Examples of aromatic vinyl compounds include styrene, o-methylstyrene, m-methylstyrene, and p-methylstyrene.

[0033] Examples of the non-olefin monomer that may be copolymerized with the olefin include a monomer having an oxygen atom and an ethylenically unsaturated bond, and a monomer having a nitrogen atom and an ethylenically unsaturated bond. The monomers other than olefins may be used alone or in combination of two or more.

[0034] Examples of monomers having an oxygen atom and an ethylenically unsaturated bond include acid anhydrides such as maleic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, phenyl maleic anhydride, and diphenyl maleic anhydride; maleic acids such as maleic acid, methyl maleic acid, dimethyl maleate, diethyl maleate, dibutyl maleate, and monomethyl maleate; (meth)acrylic acids and (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cycloalkyl (meth)acrylates having a cycloalkyl group of 3 to 20 carbon atoms, benzyl (meth)acrylate, and isobornyl (meth)acrylate; and vinyl ester compounds such as vinyl acetate and vinyl propionate. Among these, acid anhydrides and vinyl ester compounds are preferred, with maleic anhydride and vinyl acetate being more preferred, and maleic anhydride being even more preferred, from the viewpoint of improving solvent solubility and facilitating the formation of a surface coating layer by application.

[0035] Examples of the monomer having a nitrogen atom and an ethylenically unsaturated bond include maleimide compounds and derivatives thereof, and nitrile-based monomers. Examples of maleimide compounds and derivatives thereof include maleimide, N-alkyl-substituted maleimides such as N-methylmaleimide and N-ethylmaleimide, and N-aryl-substituted maleimides such as N-phenylmaleimide. Examples of nitrile monomers include acrylonitrile and methacrylonitrile.

[0036] Among the above structural units, from the viewpoint of further reducing the amount of grinding debris adhesion, the polyolefin resin preferably contains a structural unit derived from a chain olefin having 2 to 6 carbon atoms (hereinafter also referred to as "chain olefin structural unit (A)"), and more preferably contains one or more types selected from the group consisting of structural units derived from ethylene and structural units derived from propylene.

[0037] From the viewpoint of improving solvent solubility and facilitating the formation of a surface coating layer by application, the polyolefin resin preferably contains, in addition to the chain olefin structural unit (A), a structural unit derived from a monomer having an oxygen atom and an ethylenically unsaturated bond (hereinafter also referred to as "structural unit (B) containing an oxygen atom"). When the polyolefin resin contains a chain olefin structural unit (A) and a structural unit (B) containing an oxygen atom, the content of the chain olefin structural unit (A) in the polyolefin resin is not particularly limited, but is preferably 80 to 99.5 mass%, more preferably 90 to 99 mass%, and even more preferably 95 to 98.8 mass%. When the polyolefin resin contains a chain olefin structural unit (A) and a structural unit (B) containing an oxygen atom, the content of the structural unit (B) containing an oxygen atom in the polyolefin resin is not particularly limited, but is preferably 0.5 to 20 mass%, more preferably 1 to 10 mass%, and even more preferably 1.2 to 5 mass%. When the content of the chain olefin structural unit (A) and the structural unit (B) containing an oxygen atom is within the above range, good solvent solubility is obtained, and the amount of grinding debris adhesion tends to be further reduced.

[0038] Furthermore, from the viewpoint of improving solvent solubility and facilitating the formation of a surface coating layer by application, the polyolefin resin preferably contains a structural unit derived from a cyclic olefin (hereinafter also referred to as a "cyclic olefin structural unit (C)") in addition to the chain olefin structural unit (A). When the polyolefin resin contains a chain olefin structural unit (A) and a cyclic olefin structural unit (C), the content of the chain olefin structural unit (A) in the polyolefin resin is not particularly limited, but is preferably 10 to 90 mass%, more preferably 20 to 70 mass%, and even more preferably 25 to 50 mass%. When the polyolefin resin contains a chain olefin structural unit (A) and a cyclic olefin structural unit (C), the content of the cyclic olefin structural unit (C) in the polyolefin resin is not particularly limited, but is preferably 10 to 90 mass%, more preferably 30 to 80 mass%, and even more preferably 50 to 75 mass%. When the contents of the chain olefin structural unit (A) and the cyclic olefin structural unit (C) are within the above ranges, good solvent solubility is obtained, and the amount of grinding debris adhesion tends to be further reduced.

[0039] Examples of polyolefin resins include homopolymers such as polyethylene, polypropylene, and polybutadiene; binary copolymers such as ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-maleic anhydride copolymer, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylate copolymer, ethylene-tetracyclododecene copolymer, propylene-butene copolymer, propylene-maleic anhydride copolymer, propylene-vinyl acetate copolymer, propylene-(meth)acrylate copolymer, and propylene-tetracyclododecene copolymer; and copolymers such as ethylene-maleic anhydride-vinyl acetate copolymer, ethylene-maleic anhydride-(meth)acrylate copolymer, and ethylene-vinyl acetate-( and multipolymers such as propylene-maleic anhydride-vinyl acetate copolymer, propylene-maleic anhydride-(meth)acrylate copolymer, propylene-vinyl acetate-(meth)acrylate copolymer, ethylene-propylene-maleic anhydride copolymer, ethylene-propylene-vinyl acetate copolymer, ethylene-propylene-(meth)acrylate copolymer, ethylene-butene-maleic anhydride copolymer, ethylene-butene-vinyl acetate copolymer, ethylene-butene-(meth)acrylate copolymer, propylene-butene-maleic anhydride copolymer, propylene-butene-vinyl acetate copolymer, and propylene-butene-(meth)acrylate copolymer. Among these, from the viewpoint of further reducing the amount of grinding debris adhesion and improving solvent solubility to facilitate the formation of a surface coating layer by application, ethylene-vinyl acetate copolymer, ethylene-tetracyclododecene copolymer, and ethylene-butene-maleic anhydride copolymer are preferred, and ethylene-butene-maleic anhydride copolymer is more preferred.

[0040] When the organic layer contains a polyolefin-based resin as a resin component, the organic layer may contain a resin other than the polyolefin-based resin. The content of the polyolefin resin in the resin component is not particularly limited, but from the viewpoint of further reducing the amount of grinding debris attached, it is preferably 90 to 100 mass%, more preferably 95 to 100 mass%, and even more preferably 98 to 100 mass%.

[0041] (Other ingredients) The organic layer may contain components other than the resin component, as long as the effects of the present invention are not impaired. Examples of other components include additives such as antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, and dyes. The content of the resin component relative to the total amount of the organic layer is not particularly limited, but from the viewpoint of further reducing the amount of grinding debris attached, it is preferably 90 to 100 mass%, more preferably 95 to 100 mass%, and even more preferably 98 to 100 mass%.

[0042] The thickness of the surface coating layer is not particularly limited, but is preferably 0.05 to 10 μm, more preferably 0.2 to 7 μm, and even more preferably 1 to 4 μm. When the thickness of the surface coating layer is equal to or greater than the lower limit, a uniform layer can be formed, and the amount of grinding debris tends to be sufficiently reduced. When the thickness of the surface coating layer is equal to or less than the upper limit, the effect of the buffer layer, which absorbs irregularities such as foreign matter on the chuck table, tends to be easily obtained.

[0043] <Buffer layer> The buffer layer is a layer provided between the substrate and the surface coating layer, and serves to absorb vibrations, shocks, etc. that occur during back grinding and prevent cracks from occurring in the workpiece. Furthermore, by providing a buffer layer, it is possible to absorb unevenness such as foreign matter present on the table of the support device, thereby improving the holding ability of the pressure-sensitive adhesive sheet by the support device.

[0044] (Buffer layer forming composition) The buffer layer can be formed from a buffer layer-forming composition. From the viewpoint of obtaining physical properties suitable for a buffer layer, the buffer layer is preferably a layer obtained by curing, with energy rays, a buffer layer-forming composition containing an energy ray-polymerizable compound. The buffer layer-forming composition preferably contains a urethane (meth)acrylate (a1) as an energy ray-polymerizable compound. By containing the urethane (meth)acrylate (a1) in the buffer layer-forming composition, the storage modulus and the like of the buffer layer tend to be adjusted within a favorable range. From the same viewpoint, the buffer layer-forming composition more preferably contains, in addition to the urethane (meth)acrylate (a1), one or more compounds selected from the group consisting of polymerizable compounds (a2) having an alicyclic group or a heterocyclic group having 6 to 20 ring atoms and polymerizable compounds (a3) ​​having a functional group, and even more preferably contains, in addition to the urethane (meth)acrylate (a1), a polymerizable compound (a2) having an alicyclic group or a heterocyclic group having 6 to 20 ring atoms and a polymerizable compound (a3) ​​having a functional group.

[0045] [Urethane (meth)acrylate (a1)] The urethane (meth)acrylate (a1) is a compound having a (meth)acryloyl group and a urethane bond, and has the property of being polymerized by irradiation with energy rays. The urethane (meth)acrylate (a1) may be used alone or in combination of two or more kinds.

[0046] The mass average molecular weight (Mw) of the urethane (meth)acrylate (a1) is not particularly limited, but is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, and even more preferably 3,000 to 20,000. In the present embodiment, the mass average molecular weight (Mw) refers to a value calculated in terms of standard polystyrene measured by gel permeation chromatography (GPC), and specifically, is a value measured by the method described in the examples.

[0047] The number of (meth)acryloyl groups that the urethane (meth)acrylate (a1) has in one molecule is not particularly limited, but is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2.

[0048] The urethane (meth)acrylate (a1) can be obtained, for example, by reacting a polyol compound with a polyvalent isocyanate compound to obtain a terminal isocyanate urethane prepolymer, and then reacting the resulting prepolymer with a (meth)acrylate having a hydroxy group.

[0049] The polyol compound is not particularly limited as long as it is a compound having two or more hydroxy groups. Specific examples of polyol compounds include alkylene diols, polyether polyols, polyester polyols, polycarbonate polyols, etc. Among these, polyester polyols are preferred. The polyol compound may be any of a difunctional diol, a trifunctional triol, and a polyol having four or more functional groups, but a difunctional diol is preferred, and a polyester type diol is more preferred. The polyol compounds may be used alone or in combination of two or more.

[0050] Examples of polyisocyanate compounds include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, norbornane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and ω,ω'-diisocyanatodimethylcyclohexane; and aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, tetramethylene xylylene diisocyanate, and naphthalene-1,5-diisocyanate. Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferred. The polyvalent isocyanate compounds may be used alone or in combination of two or more.

[0051] The (meth)acrylate having a hydroxy group to be reacted with the isocyanate-terminated urethane prepolymer is not particularly limited as long as it is a compound having a hydroxy group and a (meth)acryloyl group in at least one molecule. Examples of (meth)acrylates having a hydroxy group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 5-hydroxycyclooctyl (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate; hydroxy group-containing (meth)acrylamides such as N-methylol (meth)acrylamide; and reaction products obtained by reacting diglycidyl esters of vinyl alcohol, vinylphenol, and bisphenol A with (meth)acrylic acid. Among these, hydroxyalkyl (meth)acrylates are preferred, and 2-hydroxyethyl (meth)acrylate is more preferred. The (meth)acrylate having a hydroxy group may be used alone or in combination of two or more kinds.

[0052] The conditions for reacting the isocyanate-terminated urethane prepolymer with the (meth)acrylate having a hydroxy group are not particularly limited, but can be, for example, conditions in which the reaction is carried out at 60 to 100°C for 1 to 4 hours in the presence of a solvent, a catalyst, etc., which are added as needed.

[0053] The content of the urethane (meth)acrylate (a1) in the buffer layer-forming composition is not particularly limited, but is preferably 10 to 70 mass %, more preferably 20 to 60 mass %, and even more preferably 30 to 50 mass %, relative to the total amount (100 mass %) of the active ingredients of the buffer layer-forming composition. In this embodiment, the active ingredients of the buffer layer-forming composition refer to the components contained in the buffer layer-forming composition excluding components such as organic solvents that are removed during the process of forming the buffer layer.

[0054] [Polymerizable compound (a2) having an alicyclic group or heterocyclic group having 6 to 20 ring atoms] When the buffer layer-forming composition contains a polymerizable compound (a2) having an alicyclic group or a heterocyclic group with 6 to 20 ring atoms (hereinafter also referred to as "polymerizable compound (a2) having an alicyclic group or a heterocyclic group"), the film-forming properties of the buffer layer-forming composition tend to be improved. The number of ring atoms refers to the number of atoms constituting the ring itself of a compound having a structure in which atoms are bonded in a ring, and does not include atoms that do not constitute the ring (e.g., hydrogen atoms bonded to atoms constituting the ring) and atoms contained in the substituent when the ring is substituted with a substituent. Examples of atoms that form the ring structure of a heterocyclic group include carbon atoms, nitrogen atoms, oxygen atoms, and sulfur atoms. The polymerizable compound (a2) having an alicyclic group or a heterocyclic group may be used alone or in combination of two or more kinds.

[0055] The polymerizable compound (a2) having an alicyclic group or a heterocyclic group is preferably a compound having a (meth)acryloyl group. The number of (meth)acryloyl groups contained in one molecule of the polymerizable compound (a2) having an alicyclic group or a heterocyclic group is not particularly limited, but is preferably one or more, more preferably one or two, and even more preferably one.

[0056] The alicyclic or heterocyclic group of the polymerizable compound (a2) having an alicyclic or heterocyclic group has 6 to 20 ring atoms, preferably 6 to 18, more preferably 6 to 16, and even more preferably 7 to 12 ring atoms.

[0057] Examples of the polymerizable compound (a2) having an alicyclic group or a heterocyclic group include alicyclic group-containing (meth)acrylates such as isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, cyclohexyl (meth)acrylate, and adamantane (meth)acrylate; heterocyclic group-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate and morpholine (meth)acrylate; etc. Among these, alicyclic group-containing (meth)acrylates are preferred, and isobornyl (meth)acrylate is more preferred.

[0058] The content of the polymerizable compound (a2) having an alicyclic group or a heterocyclic group in the buffer layer-forming composition is not particularly limited, but is preferably 10 to 70 mass %, more preferably 20 to 60 mass %, and even more preferably 30 to 50 mass %, relative to the total amount (100 mass %) of the active ingredients of the buffer layer-forming composition.

[0059] [Polymerizable compound (a3) ​​having a functional group] By including the polymerizable compound (a3) ​​having a functional group in the buffer layer-forming composition, the viscosity of the buffer layer-forming composition tends to be adjusted to an appropriate range. The polymerizable compound (a3) ​​having a functional group may be used alone or in combination of two or more kinds.

[0060] Examples of the functional group contained in the polymerizable compound (a3) ​​having a functional group include a hydroxyl group, an epoxy group, an amide group, and an amino group. The number of functional groups contained in one molecule of the polymerizable compound (a3) ​​having a functional group is one or more, preferably one to three, more preferably one or two, and even more preferably one.

[0061] The polymerizable compound (a3) ​​having a functional group is preferably a compound having a (meth)acryloyl group in addition to the functional group. The number of (meth)acryloyl groups that the polymerizable compound (a3) ​​having a functional group has in one molecule is not particularly limited, but is preferably one or more, more preferably one or two, and even more preferably one.

[0062] Examples of the polymerizable compound (a3) ​​having a functional group include a hydroxyl group-containing polymerizable compound, an epoxy group-containing polymerizable compound, an amide group-containing polymerizable compound, and an amino group-containing polymerizable compound.

[0063] Examples of hydroxyl group-containing polymerizable compounds include hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate; and vinyl ether compounds such as hydroxyethyl vinyl ether and hydroxybutyl vinyl ether.

[0064] Examples of epoxy group-containing polymerizable compounds include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

[0065] Examples of amide group-containing polymerizable compounds include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, and N-vinylformamide.

[0066] Examples of the amino group-containing polymerizable compound include amino group-containing (meth)acrylates such as primary amino group-containing (meth)acrylates, secondary amino group-containing (meth)acrylates, and tertiary amino group-containing (meth)acrylates.

[0067] Among these, hydroxyl group-containing (meth)acrylates are preferred, and hydroxyl group-containing (meth)acrylates having an aromatic ring such as 2-hydroxy-3-phenoxypropyl (meth)acrylate are more preferred.

[0068] The content of the polymerizable compound (a3) ​​having a functional group in the buffer layer-forming composition is not particularly limited, but is preferably 5 to 40 mass %, more preferably 10 to 30 mass %, and even more preferably 15 to 25 mass %, relative to the total amount (100 mass %) of the active ingredients of the buffer layer-forming composition.

[0069] [Other polymerizable compounds] The buffer layer-forming composition may contain other polymerizable compounds in addition to the components (a1) to (a3) ​​as long as the effects of the present invention are not impaired. Examples of other polymerizable compounds include alkyl (meth)acrylates having an alkyl group having 1 to 20 carbon atoms; vinyl compounds such as styrene, N-vinylpyrrolidone, and N-vinylcaprolactam; and the like. The other polymerizable compounds may be used alone or in combination of two or more. The content of other polymerizable compounds in the buffer layer-forming composition is not particularly limited, but is preferably 0 to 20 mass %, more preferably 0 to 10 mass %, and even more preferably 0 to 2 mass %, relative to the total amount (100 mass %) of the active ingredients in the buffer layer-forming composition.

[0070] [Photopolymerization initiator] The buffer layer-forming composition containing the energy ray-polymerizable compound preferably further contains a photopolymerization initiator from the viewpoint of reducing the polymerization time and the energy ray irradiation dose due to energy ray irradiation. The photopolymerization initiator may be used alone or in combination of two or more kinds.

[0071] Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones. More specific examples include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. Among these, 1-hydroxycyclohexyl phenyl ketone is preferred.

[0072] The content of the photopolymerization initiator in the buffer layer-forming composition is not particularly limited, but from the viewpoint of allowing the energy ray curing reaction to proceed uniformly and sufficiently, it is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.3 to 5 parts by mass relative to 100 parts by mass of the total amount of the energy ray-polymerizable compounds.

[0073] (Other ingredients) The buffer layer-forming composition may contain other components within the range that does not impair the effects of the present invention, such as resin components other than the above-mentioned resins, and additives such as antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, and dyes. The content of other resin components in the buffer layer-forming composition is not particularly limited, but is preferably 0 to 20 mass %, more preferably 0 to 10 mass %, and even more preferably 0 to 2 mass %, relative to the total amount (100 mass %) of the active ingredients in the buffer layer-forming composition. The content of other additives in the buffer layer-forming composition is not particularly limited, but each additive is preferably 0 to 6 mass %, more preferably 0.01 to 5 mass %, and even more preferably 0.1 to 3 mass %, relative to the total amount (100 mass %) of the active ingredients in the buffer layer-forming composition.

[0074] (Young's modulus of the buffer layer) The Young's modulus of the buffer layer at 23°C is smaller than that of the substrate at 23°C, specifically, preferably less than 1,200 MPa, more preferably 900 MPa or less. Also, the Young's modulus of the buffer layer at 23°C is preferably 50 MPa or more, more preferably 100 MPa or more. When the Young's modulus of the buffer layer at 23°C is the above upper limit or less, the effect of absorbing vibrations, shocks, etc. that occur during backside grinding and the retention of the adhesive sheet tend to be improved. Also, when the Young's modulus of the buffer layer at 23°C is the above lower limit or more, excessive deformation of the buffer layer when processing the workpiece tends to be suppressed. The Young's modulus of the buffer layer at 23° C. can be measured in accordance with JIS K 7127:1999 at a test speed of 200 mm / min.

[0075] (stress relaxation rate of buffer layer) The stress relaxation rate of the buffer layer is not particularly limited, but is preferably 70 to 100%, more preferably 75 to 100%, and even more preferably 78 to 98%. When the stress relaxation rate of the buffer layer is within the above range, the effect of absorbing vibrations, shocks, etc. that occur during back grinding and the retention of the adhesive sheet tend to be improved. The stress relaxation rate of the buffer layer was measured by cutting a 200 μm thick buffer layer into a 15 mm × 140 mm test piece, gripping both ends of the test piece by 20 mm, and stretching it by 10% at 200 mm / min, measuring the stress A (N / m 2 ), and stress B (N / m 2 ) can be calculated using the following formula: Stress relaxation rate (%) = 100 × (AB) / A (%)

[0076] (Buffer layer thickness) The thickness of the buffer layer is not particularly limited, but is preferably 10 to 70 μm, more preferably 15 to 50 μm, and even more preferably 20 to 40 μm. When the thickness of the buffer layer is equal to or greater than the lower limit, the effect of absorbing vibrations, shocks, etc. that occur during backside grinding and the retention of the adhesive sheet tend to be enhanced. Also, when the thickness of the buffer layer is equal to or less than the upper limit, excessive deformation of the buffer layer when processing the workpiece tends to be suppressed.

[0077] <Adhesive layer> The adhesive layer is a layer provided on the surface of the substrate opposite to the buffer layer, and is a layer that is attached to the workpiece. The adhesive layer is preferably a layer formed from an energy ray-curable adhesive, which provides sufficient adhesion to protect the workpiece surface before energy ray curing, and reduces the peel force after energy ray curing, making it easy to peel from the workpiece.

[0078] Examples of the energy ray-curable adhesive include the following X-type adhesive composition, Y-type adhesive composition, and XY-type adhesive composition. X-type adhesive composition: an energy ray-curable adhesive composition containing a non-energy ray-curable adhesive resin (hereinafter also referred to as "adhesive resin I") and an energy ray-curable compound other than the adhesive resin. Y-type adhesive composition: An energy ray-curable adhesive composition containing an energy ray-curable adhesive resin (hereinafter also referred to as "adhesive resin II") in which an unsaturated group has been introduced into the side chain of a non-energy ray-curable adhesive resin, and not containing any energy ray-curable compound other than the adhesive resin. XY-type adhesive composition: an energy ray-curable adhesive composition containing the above energy ray-curable adhesive resin II and an energy ray-curable compound other than the adhesive resin. Among these, the energy ray-curable adhesive is preferably an XY-type adhesive composition, which tends to have sufficient adhesiveness before curing while being able to sufficiently reduce the peel force from the workpiece after curing.

[0079] The adhesive forming the adhesive layer may be a layer formed from a non-energy ray curable adhesive that does not cure even when irradiated with energy rays. Examples of non-energy ray-curable adhesives include those that contain adhesive resin I but do not contain adhesive resin II or an energy ray-curable compound.

[0080] Next, each component constituting the pressure-sensitive adhesive layer will be described in more detail. In the following description, the term "adhesive resin" is used to refer to either or both of adhesive resin I and adhesive resin II. Furthermore, in the following description, when simply referring to an "adhesive composition," this concept includes an X-type adhesive composition, a Y-type adhesive composition, an XY-type adhesive composition, and adhesive compositions other than these.

[0081] Examples of adhesive resins include acrylic resins, urethane resins, rubber resins, silicone resins, etc. Among these, acrylic resins are preferred.

[0082] (acrylic resin) The acrylic resin preferably contains a structural unit derived from an alkyl(meth)acrylate. Examples of alkyl(meth)acrylates include alkyl(meth)acrylates in which the alkyl group has 1 to 20 carbon atoms. The alkyl group contained in the alkyl(meth)acrylate may be linear or branched.

[0083] From the viewpoint of further improving the adhesive strength of the adhesive layer, the acrylic resin preferably contains a structural unit derived from an alkyl (meth)acrylate in which the alkyl group has 4 or more carbon atoms. The structural unit derived from alkyl (meth)acrylate in which the alkyl group contains 4 or more carbon atoms contained in the acrylic resin may be of one type alone or of two or more types. The alkyl group of the alkyl (meth)acrylate having 4 or more carbon atoms preferably has 4 to 12 carbon atoms, more preferably 4 to 8 carbon atoms, and even more preferably 4 to 6 carbon atoms. Examples of alkyl(meth)acrylates in which the alkyl group has 4 or more carbon atoms include butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate, undecyl(meth)acrylate, dodecyl(meth)acrylate, etc. Among these, butyl(meth)acrylate is preferred, and butyl acrylate is more preferred. When the acrylic resin contains a structural unit derived from an alkyl (meth)acrylate in which the alkyl group has 4 or more carbon atoms, the content thereof in the acrylic resin is preferably 30 to 90 mass %, more preferably 40 to 80 mass %, and even more preferably 45 to 60 mass %, from the viewpoint of further improving the adhesive strength of the adhesive layer.

[0084] From the viewpoint of improving the storage modulus G' and adhesive properties of the adhesive layer, it is preferable that the acrylic resin contains a structural unit derived from an alkyl(meth)acrylate in which the alkyl group has 4 or more carbon atoms, as well as a structural unit derived from an alkyl(meth)acrylate in which the alkyl group has 1 to 3 carbon atoms. The structural unit derived from alkyl (meth)acrylate in which the alkyl group contains 1 to 3 carbon atoms contained in the acrylic resin may be of one type alone or of two or more types. Examples of alkyl(meth)acrylates in which the alkyl group has 1 to 3 carbon atoms include methyl(meth)acrylate, ethyl(meth)acrylate, isopropyl(meth)acrylate, n-propyl(meth)acrylate, etc. Among these, methyl(meth)acrylate and ethyl(meth)acrylate are preferred, methyl(meth)acrylate is more preferred, and methyl methacrylate is even more preferred. When the acrylic resin contains a structural unit derived from an alkyl (meth)acrylate in which the alkyl group has 1 to 3 carbon atoms, the content thereof in the acrylic resin is preferably 1 to 35 mass%, more preferably 5 to 30 mass%, and even more preferably 15 to 25 mass%.

[0085] The acrylic resin preferably further contains a structural unit derived from a functional group-containing monomer. When the acrylic resin contains a constituent unit derived from a functional group-containing monomer, it is possible to introduce a functional group that acts as a crosslinking origin that reacts with a crosslinking agent, or a functional group that reacts with an unsaturated group-containing compound to introduce an unsaturated group into the side chain of the acrylic resin. The structural unit derived from the functional group-containing monomer contained in the acrylic resin may be of one type alone or two or more types.

[0086] Examples of functional group-containing monomers include hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, epoxy group-containing monomers, etc. Among these, hydroxyl group-containing monomers and carboxyl group-containing monomers are preferred, and hydroxyl group-containing monomers are more preferred. Examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as 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; unsaturated alcohols such as vinyl alcohol and allyl alcohol; and the like. Examples of carboxy group-containing monomers include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids and anhydrides thereof such as fumaric acid, itaconic acid, maleic acid and citraconic acid; and 2-carboxyethyl methacrylate.

[0087] When the acrylic resin contains a structural unit derived from a functional group-containing monomer, the content thereof is not particularly limited, but is preferably 5 to 45 mass %, more preferably 15 to 40 mass %, and even more preferably 25 to 35 mass % in the acrylic resin.

[0088] In addition to the above-mentioned structural units, the acrylic resin may contain structural units derived from other monomers copolymerizable with the acrylic monomer. The structural units derived from other monomers contained in the acrylic resin may be of one type alone or two or more types. Examples of other monomers include styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, and acrylamide.

[0089] The acrylic resin may further contain an energy ray-polymerizable unsaturated group introduced therein in order to impart energy ray-curability. The unsaturated group can be introduced, for example, by reacting a functional group of an acrylic resin containing a constituent unit derived from a functional group-containing monomer with a reactive substituent reactive with the functional group and a reactive substituent of a compound having an unsaturated group (hereinafter also referred to as an "unsaturated group-containing compound"). One type of unsaturated group-containing compound may be used alone, or two or more types may be used in combination. Examples of the unsaturated group contained in the unsaturated group-containing compound include a (meth)acryloyl group, a vinyl group, an allyl group, etc. Among these, a (meth)acryloyl group is preferred. Examples of reactive substituents that the unsaturated group-containing compound has include an isocyanate group and a glycidyl group. Examples of the unsaturated group-containing compound include (meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, and glycidyl (meth)acrylate.

[0090] When an acrylic resin containing a structural unit derived from a functional group-containing monomer is reacted with an unsaturated group-containing compound, the ratio of functional groups that react with the unsaturated group-containing compound to the total number of functional groups in the acrylic resin is not particularly limited, but is preferably 60 to 98 mol %, more preferably 70 to 95 mol %, and even more preferably 80 to 93 mol %. When the ratio of functional groups that react with the unsaturated group-containing compound is within the above range, sufficient energy ray curability can be imparted to the acrylic resin, and the functional groups that have not reacted with the unsaturated group-containing compound can be reacted with a crosslinking agent to crosslink the acrylic resin.

[0091] The mass average molecular weight (Mw) of the acrylic resin is not particularly limited, but is preferably 300,000 to 1,500,000, more preferably 350,000 to 1,000,000, and even more preferably 400,000 to 600,000. When the mass average molecular weight (Mw) of the acrylic resin is within the above range, the adhesive strength and cohesive strength of the pressure-sensitive adhesive layer tend to be better.

[0092] (energy ray curable compound) The energy ray-curable compound contained in the X-type or XY-type pressure-sensitive adhesive composition is preferably a monomer or oligomer having an unsaturated group in the molecule and curable by energy ray irradiation. Examples of the energy ray-curable compound include polyvalent (meth)acrylate monomers such as trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, and 1,6-hexanediol (meth)acrylate; and oligomers such as urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and epoxy (meth)acrylate. Among these, urethane (meth)acrylate oligomers are preferred from the viewpoints that they have a relatively high molecular weight and are less likely to reduce the elastic modulus of the pressure-sensitive adhesive layer.

[0093] The molecular weight of the energy ray-curable compound is not particularly limited, but is preferably 100 to 12,000, more preferably 200 to 10,000, even more preferably 400 to 8,000, and still more preferably 600 to 6,000. When the energy ray-curable compound is an oligomer, the above molecular weight means the mass average molecular weight (Mw).

[0094] The content of the energy ray-curable compound in the X-type pressure-sensitive adhesive composition is not particularly limited, but is preferably 40 to 200 parts by mass, more preferably 50 to 150 parts by mass, and even more preferably 60 to 90 parts by mass relative to 100 parts by mass of the pressure-sensitive adhesive resin. When the content of the energy ray-curable compound in the X-type pressure-sensitive adhesive composition is within the above range, the balance between the adhesive strength before energy ray irradiation and the releasability after energy ray irradiation tends to be good.

[0095] The content of the energy ray-curable compound in the XY-type pressure-sensitive adhesive composition is not particularly limited, but is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, and even more preferably 3 to 15 parts by mass relative to 100 parts by mass of the pressure-sensitive adhesive resin. When the content of the energy ray-curable compound in the XY-type pressure-sensitive adhesive composition is within the above range, the balance between the adhesive strength before energy ray irradiation and the peelability after energy ray irradiation tends to be good. Note that, since the adhesive resin in the XY-type pressure-sensitive adhesive composition is energy ray-curable, even if the content of the energy ray-curable compound is small, the peel strength after energy ray irradiation tends to be sufficiently reduced.

[0096] (Crosslinking agent) The pressure-sensitive adhesive composition preferably further contains a crosslinking agent. The crosslinking agent crosslinks the adhesive resins together by reacting with the functional group derived from the functional group-containing monomer contained in the adhesive resin, for example. The crosslinking agent may be used alone or in combination of two or more kinds.

[0097] Examples of crosslinking agents include isocyanate-based crosslinking agents such as tolylene diisocyanate, hexamethylene diisocyanate, and adducts thereof; epoxy-based crosslinking agents such as ethylene glycol glycidyl ether; aziridine-based crosslinking agents such as hexa[1-(2-methyl)-aziridinyl]triphosphatriazine; chelate-based crosslinking agents such as aluminum chelate; etc. Among these, isocyanate-based crosslinking agents are preferred from the viewpoints of increasing cohesive strength and further improving adhesive strength, and from the viewpoints of ease of availability.

[0098] When the pressure-sensitive adhesive composition contains a crosslinking agent, the content thereof is not particularly limited, but from the viewpoint of allowing the crosslinking reaction to proceed appropriately, it is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 4 parts by mass relative to 100 parts by mass of the pressure-sensitive adhesive resin.

[0099] (Photopolymerization initiator) When the pressure-sensitive adhesive is an energy ray-curable pressure-sensitive adhesive, the pressure-sensitive adhesive composition preferably further contains a photopolymerization initiator. By containing a photopolymerization initiator in the energy ray-curable pressure-sensitive adhesive, the curing reaction of the energy ray-curable pressure-sensitive adhesive tends to proceed sufficiently even with relatively low-energy energy rays such as ultraviolet rays. The photopolymerization initiator may be used alone or in combination of two or more kinds.

[0100] Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and further photosensitizers such as amines and quinones. More specific examples include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0101] When the energy ray-curable adhesive contains a photopolymerization initiator, the content thereof is not particularly limited, but from the viewpoint of allowing the energy ray curing reaction to proceed uniformly and sufficiently, it is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 5 parts by mass relative to 100 parts by mass of the adhesive resin.

[0102] (Other additives) The PSA composition may contain other additives within the range that does not impair the effects of the present invention, such as antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, dyes, etc. The content of other additives in the pressure-sensitive adhesive composition is not particularly limited, but is preferably 0 to 6 mass%, more preferably 0.01 to 5 mass%, and even more preferably 0.1 to 3 mass%, relative to the total amount (100 mass%) of the active ingredients in the pressure-sensitive adhesive composition. In this embodiment, the active ingredient of the pressure-sensitive adhesive composition means the components contained in the pressure-sensitive adhesive composition excluding components such as organic solvents that are removed during the process of forming the pressure-sensitive adhesive layer.

[0103] (organic solvent) The pressure-sensitive adhesive composition may be diluted with an organic solvent to form a solution, from the viewpoint of further improving the applicability to substrates, release sheets, and the like. Examples of the organic solvent include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol. The organic solvent may be used alone or in combination of two or more kinds. The organic solvent may be the same as that used in the synthesis of the adhesive resin, or one or more organic solvents other than those used in the synthesis may be added.

[0104] The storage modulus G' of the pressure-sensitive adhesive layer at 23°C is not particularly limited, but is preferably 0.05 to 0.5 MPa, more preferably 0.1 to 0.4 MPa, and even more preferably 0.12 to 0.3 MPa. When the storage modulus G' at 23°C of the adhesive layer is within the above range, even if the surface of the workpiece is uneven, an adhesive layer with excellent conformability to the uneven shape is obtained, and the surface of the workpiece tends to be better protected during processing. When the pressure-sensitive adhesive layer is formed from an energy ray-curable pressure-sensitive adhesive, the storage modulus G' of the pressure-sensitive adhesive layer means the storage modulus G' before curing by irradiation with energy rays. The storage modulus G' of the adhesive layer at 23°C can be measured by the torsional shear method using a viscoelasticity measuring device, using a 3 mm thick adhesive layer cut into a circular shape with a diameter of 8 mm as a test piece, at a frequency of 1 Hz and a measurement temperature of 23°C.

[0105] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 5 to 100 μm, more preferably 10 to 80 μm, and even more preferably 15 to 60 μm. When the thickness of the adhesive layer is equal to or greater than the lower limit, excellent adhesiveness is obtained, and the surface of the workpiece tends to be better protected during processing. On the other hand, when the thickness of the adhesive layer is equal to or less than the upper limit, the generation of tape scraps when the adhesive sheet is cut is suppressed, and damage to the workpiece tends to be better prevented.

[0106] <Base material> Examples of the substrate include various resin films. Examples of resins constituting the resin film include polyethylenes such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE); polyolefins such as polypropylene, polybutene, polybutadiene, polymethylpentene, ethylene-norbornene copolymers, and norbornene resins; ethylene copolymers such as ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid copolymers, and ethylene-(meth)acrylic acid ester copolymers; polyvinyl chlorides such as polyvinyl chloride and vinyl chloride copolymers; polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and wholly aromatic polyesters; polyurethanes, polyimides, polyamides, polycarbonates, fluororesins, polyacetals, modified polyphenylene oxides, polyphenylene sulfides, polysulfones, polyether ketones, and acrylic polymers. The substrate may be a single-layer film made of one or more resins selected from these resins, or a laminate film made of two or more of these resin films, or a modified film such as a crosslinked film or ionomer film of the above resin. Among these resin films, the substrate is preferably one or more selected from polyester film, polyamide film, polyimide film and biaxially oriented polypropylene film, more preferably polyester film, and even more preferably polyethylene terephthalate film.

[0107] The Young's modulus of the substrate is not particularly limited, but is preferably 1,000 MPa or more, more preferably 1,800 to 30,000 MPa, and even more preferably 2,500 to 6,000 MPa. When the Young's modulus of the substrate is equal to or greater than the lower limit, the vibration suppression effect during workpiece processing tends to be improved, and when the Young's modulus of the substrate is equal to or less than the upper limit, the workability when attaching the film to a workpiece and when peeling it off from the workpiece tends to be improved. The Young's modulus of the substrate can be measured in accordance with JIS K 7127:1999 at a test speed of 200 mm / min.

[0108] The thickness of the substrate is not particularly limited, but is preferably 10 to 200 μm, more preferably 25 to 100 μm, and even more preferably 30 to 70 μm. When the thickness of the substrate is equal to or greater than the lower limit, the substrate tends to have sufficient strength to function as a support for the PSA sheet, whereas when the thickness of the substrate is equal to or less than the upper limit, the substrate tends to have appropriate flexibility and improve handleability. The "thickness of the substrate" means the thickness of the entire substrate, and when the substrate is made up of multiple layers, it means the total thickness of all layers constituting the substrate.

[0109] The substrate may contain a plasticizer, a lubricant, an infrared absorber, an ultraviolet absorber, a filler, a colorant, an antistatic agent, an antioxidant, a catalyst, and the like, as long as the effects of the present invention are not impaired. The substrate may be transparent or opaque and may be colored or vapor-deposited as desired. From the viewpoint of improving adhesion to other layers, the substrate may be subjected to a surface treatment such as corona treatment on at least one side, or may be provided with a coating layer for the purpose of improving adhesion.

[0110] <Release sheet> The pressure-sensitive adhesive sheet of the present embodiment may have a release sheet attached to at least one of the surface of the pressure-sensitive adhesive layer and the surface of the surface coating layer. The release sheet is removably attached to the surface of the pressure-sensitive adhesive sheet before use to protect the surface, and is peeled off and removed when the pressure-sensitive adhesive sheet is to be used. The release sheet may be a release sheet which has been treated for release on one side or on both sides. A preferred example of the release sheet is a release sheet in which a release agent is applied to a base material for the release sheet. The substrate for the release sheet is preferably a resin film, and examples of the resin film include polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film; polyolefin films such as polypropylene film and polyethylene film; and the like. Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins; long-chain alkyl resins, alkyd resins, and fluorine-based resins. The thickness of the release sheet is not particularly limited, but is preferably 5 to 200 μm, more preferably 10 to 100 μm, and even more preferably 20 to 50 μm.

[0111] The total thickness of the pressure-sensitive adhesive sheet of the present embodiment is not particularly limited, but is preferably 30 to 300 μm, more preferably 40 to 220 μm, and even more preferably 45 to 160 μm. When the total thickness of the adhesive sheet is equal to or greater than the above lower limit, the adhesive performance of the adhesive layer and the impact absorption performance of the buffer layer are appropriately maintained, and the adhesive sheet tends to be able to fully function as an adhesive sheet for semiconductor processing. Also, when the total thickness of the adhesive sheet is equal to or less than the above upper limit, the peel force when peeling the workpiece from the adhesive sheet tends to be small. In this embodiment, the "total thickness of the adhesive sheet" means the thickness from the surface of the surface coating layer of the adhesive sheet to the surface of the adhesive layer, and if a release sheet is provided, the thickness of the release sheet is not included in the total thickness.

[0112] <Method of manufacturing adhesive sheets> The method for producing the pressure-sensitive adhesive sheet of this embodiment is not particularly limited, and the sheet can be produced by a known method. The pressure-sensitive adhesive sheet of this embodiment can be produced, for example, by a method including a step of forming a pressure-sensitive adhesive layer on one side of a substrate (hereinafter also referred to as a "pressure-sensitive adhesive layer forming step"), a step of forming a buffer layer on the other side of the substrate (hereinafter also referred to as a "buffer layer forming step"), and a step of forming a surface coating layer on the side of the buffer layer opposite the substrate (hereinafter also referred to as a "surface coating layer forming step"). The order of these steps is not particularly limited, and if they can be performed simultaneously, they may be performed simultaneously.

[0113] The pressure-sensitive adhesive layer forming step may be, for example, a method of laminating a pressure-sensitive adhesive layer formed on a release sheet to the surface of a substrate, or a method of forming a pressure-sensitive adhesive layer by directly applying a pressure-sensitive adhesive composition to the surface of a substrate. The buffer layer forming step may be, for example, a method of bonding a buffer layer formed on a release sheet to the surface of the substrate, or a method of forming a buffer layer by directly applying a buffer layer forming composition to the surface of the substrate. The surface coating layer forming process may be, for example, a method in which a surface coating layer formed on a release sheet is bonded to the surface of a buffer layer on a substrate, or a method in which a surface coating layer is formed by directly applying a coating liquid for the surface coating layer to the surface of a buffer layer on a substrate. The buffer layer forming step and the surface coating layer forming step may be a method in which the surface coating layer and the buffer layer are provided in this order on a release sheet, and then the buffer layer is attached to the surface of the substrate.

[0114] Examples of methods for forming a pressure-sensitive adhesive layer, a buffer layer, or a surface coating layer on a release sheet include a method in which a pressure-sensitive adhesive composition, a buffer layer-forming composition, or a surface coating layer coating liquid is applied to a release sheet by a known method, and then, if necessary, energy ray irradiation, heat drying, or the like is performed.

[0115] Examples of methods for applying the pressure-sensitive adhesive composition, the buffer layer-forming composition, or the surface coating layer coating liquid include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0116] When the buffer layer-forming composition contains an energy ray-polymerizable compound, the curing treatment by energy ray irradiation may be carried out in one step or in multiple steps. When the curing treatment is performed in one step, after forming a coating film of the buffer layer-forming composition on the substrate, the buffer layer-forming composition may be completely cured by irradiating it with energy rays, or the buffer layer-forming composition may be completely cured on a release sheet and then attached to the substrate. When the curing treatment is performed in multiple steps, after forming a coating film of the buffer layer-forming composition on the release sheet, the buffer layer-forming composition may not be completely cured on the release sheet, but may be cured to a semi-cured state before being attached to the substrate, and then the buffer layer-forming composition may be completely cured by irradiating it with energy rays again. The energy rays irradiated in the curing treatment of the buffer layer-forming composition are preferably ultraviolet rays. When curing the buffer layer-forming composition, the coating film of the buffer layer-forming composition may be exposed to the outside, but it is preferable to irradiate the energy rays while the coating film is covered with a release sheet or a substrate and is not exposed to the outside.

[0117] <Applications of adhesive sheets> Examples of workpiece processing performed with the adhesive sheet of this embodiment attached include backgrinding, in which one surface of a semiconductor device is ground with the adhesive sheet attached to the other surface, dicing, in which a semiconductor device is divided into individual pieces with the adhesive sheet attached to one surface of the semiconductor device, transporting semiconductor devices, and picking up semiconductor chips. Among these, the adhesive sheet of this embodiment is suitable for backgrinding, and is even more suitable for backgrinding, in which the back surface of a semiconductor wafer is ground with the adhesive sheet of this embodiment attached to the circuit-forming surface of the semiconductor wafer. In particular, the adhesive sheet of this embodiment has the effect of suppressing the occurrence of cracks when thinning a semiconductor wafer, and is therefore suitable for processes such as first-edge dicing and stealth first-edge dicing.

[0118] [Method of manufacturing a semiconductor device] The method for manufacturing a semiconductor device according to this embodiment includes the steps of: A step of attaching the semiconductor processing adhesive sheet of this embodiment to the surface of a semiconductor wafer with the adhesive layer as an attachment surface; grinding the back surface of the semiconductor wafer while the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer is fixed by a supporting device; The present invention relates to a method for manufacturing a semiconductor device, comprising the steps of:

[0119] Further, the method for manufacturing a semiconductor device according to the present embodiment includes the steps of: a dividing line forming step, which is a step a of forming grooves on the surface of the semiconductor wafer, or a step b of forming modified regions inside the semiconductor wafer from the surface or back surface of the semiconductor wafer; a sheet attaching step of attaching the semiconductor processing adhesive sheet of the present embodiment to the surface of the semiconductor wafer with the adhesive layer as an attachment surface after the step a, or before or after the step b; a grinding and singulating step of grinding the back surface of the semiconductor wafer while the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer is fixed by a supporting device, and singulating the semiconductor wafer into a plurality of semiconductor chips starting from the grooves or modified regions; Preferably, the method for manufacturing a semiconductor device includes: Furthermore, the method for manufacturing a semiconductor device of this embodiment may include a peeling step of peeling the adhesive sheet for semiconductor processing of this embodiment from the plurality of semiconductor chips after the grinding and singulation step. The method for manufacturing a semiconductor device including the above step a is a process equivalent to a dicing-first method, and the method for manufacturing a semiconductor device including the above step b is a process equivalent to a stealth dicing-first method.

[0120] Examples of semiconductor wafers used in the manufacturing method of this embodiment include silicon wafers, gallium arsenide wafers, gallium nitride wafers, silicon carbide wafers, glass wafers, sapphire wafers, etc. Among these, silicon wafers are preferred. The surface of a semiconductor wafer usually has circuits formed thereon, such as wiring, capacitors, diodes, transistors, etc. These circuits can be formed by conventionally known methods, such as etching and lift-off. The thickness of the semiconductor wafer before grinding is not particularly limited, but is usually 500 to 1,000 μm. Each step of the method for manufacturing the semiconductor device according to this embodiment will now be described in detail.

[0121] <Division line formation process> The dividing line forming step is a step a of forming grooves on the surface of a semiconductor wafer, or a step b of forming modified regions inside the semiconductor wafer from the surface or back surface of the semiconductor wafer.

[0122] Step a is a step of forming grooves on the surface of a semiconductor wafer, and is carried out before the adhesive sheet is attached to the surface of the semiconductor wafer. The grooves formed in the surface of the semiconductor wafer in step a are shallower than the thickness of the semiconductor wafer. After step a, the backside of the semiconductor wafer is ground down to the grooves formed in step a, and the semiconductor wafer is divided into multiple semiconductor chips. Therefore, in step a, the grooves are formed along the dividing lines along which the semiconductor wafer is divided into individual semiconductor chips. The grooves can be formed by dicing using a conventionally known wafer dicing device or the like.

[0123] Step b is a step of forming a modified region inside the semiconductor wafer from the front or back surface of the semiconductor wafer, and may be performed before or after the adhesive sheet is attached to the front surface of the semiconductor wafer. In step b, a modified region is formed inside the semiconductor wafer by irradiating a laser focused on the inside of the semiconductor wafer. The modified region is an embrittled portion of the semiconductor wafer, which is destroyed when the semiconductor wafer is thinned by backside grinding or when grinding force is applied, and serves as a starting point for dividing the semiconductor wafer into semiconductor chips. Therefore, the modified region is formed along the dividing line when the semiconductor wafer is divided into semiconductor chips. The laser irradiation may be performed from the front side or the back side of the semiconductor wafer. When step b is performed after the sheet attaching step, the laser may be irradiated onto the semiconductor wafer through the pressure-sensitive adhesive sheet.

[0124] <Sheet pasting process> The sheet adhering step is a step of adhering an adhesive sheet to the surface of a semiconductor wafer with the adhesive layer serving as the adhering surface after step a or before or after step b. The method for attaching the pressure-sensitive adhesive sheet is not particularly limited, and any conventionally known method using, for example, a laminator or the like can be applied.

[0125] <Grinding and Slicing Process> The grinding and singulation process is a process in which the back surface of the semiconductor wafer is ground while the surface coating layer side of the adhesive sheet attached to the semiconductor wafer is fixed by a support device, and the semiconductor wafer is singulated into multiple semiconductor chips starting from the grooves or modified regions. The semiconductor wafer to which the pressure-sensitive adhesive sheet is attached and to which the grooves or modified regions are formed is fixed on the surface coating layer side of the pressure-sensitive adhesive sheet by a supporting device, which is not particularly limited, but is preferably a device that suctions and holds a fixed object such as a chuck table.

[0126] Next, the back surface of the fixed semiconductor wafer is ground to separate the semiconductor wafer into a plurality of semiconductor chips. In the backside grinding, when grooves are formed in the semiconductor wafer in step a, the semiconductor wafer is ground at least to a position where the grinding surface reaches the bottom of the grooves. This backside grinding turns the grooves into notches that penetrate the wafer, and the semiconductor wafer is divided by the notches into individual semiconductor chips. On the other hand, if a modified region is formed on the semiconductor wafer by step b, the grinding surface may reach the modified region, but does not necessarily reach the modified region. That is, the grinding may be performed to a position close to the modified region so that the semiconductor wafer is broken starting from the modified region and singulated into semiconductor chips. For example, the semiconductor wafer may be ground to a position close to the modified region without singulation, and then a pick-up tape may be attached to the semiconductor wafer and stretched to singulate the semiconductor chips.

[0127] The shape of the individual semiconductor chips may be square or may be an elongated shape such as a rectangle. The thickness of the individual semiconductor chips is not particularly limited, but is preferably 5 to 100 μm, more preferably 7 to 70 μm, and even more preferably 10 to 45 μm. The size of the individual semiconductor chips is not particularly limited, but is preferably 50 mm 2 Less than 30 mm, preferably 2 Less than 10 mm, more preferably 2 is less than.

[0128] <Peeling process> The peeling step is a step of peeling the adhesive sheet from the semiconductor chips after the grinding and singulation step. When the adhesive layer of the adhesive sheet is formed from an energy ray-curable adhesive, the adhesive is cured by irradiating it with energy rays, reducing the peel strength of the adhesive layer, and then the adhesive sheet is peeled off. When peeling off the PSA sheet, a pick-up tape may be used. The pick-up tape is, for example, composed of a substrate and a PSA sheet having a PSA layer provided on one side of the substrate. When using a pick-up tape, first, the pick-up tape is attached to the backside of the individual semiconductor wafer, and the position and orientation are adjusted so that the chips can be picked up. At this time, it is preferable that a ring frame arranged on the outer periphery of the semiconductor wafer is also attached to the pick-up tape, and the outer edge of the pick-up tape is fixed to the ring frame. Next, the adhesive sheet is peeled off from the multiple semiconductor chips fixed on the pick-up tape. Thereafter, a plurality of semiconductor chips on the pickup tape may be picked up and fixed onto a substrate or the like to manufacture a semiconductor device. [Example]

[0129] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring and evaluating various physical properties are as follows.

[0130] [Mass average molecular weight (Mw)] The mass average molecular weight (Mw) was measured under the following conditions using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8220") and calculated in terms of standard polystyrene. (Measurement conditions) Columns: "TSK guard column HXL-H", "TSK gel GMHXL (x2)", "TSK gel G2000HXL" (all manufactured by Tosoh Corporation) Column temperature: 40℃ Developing solvent: tetrahydrofuran ·Flow rate: 1.0mL / min

[0131] [Measuring the thickness of adhesive sheets, etc.] The total thickness of the pressure-sensitive adhesive sheet, the thickness of each layer, and the thickness of the test piece made from these were measured using a constant pressure thickness measuring device (manufactured by Teclock Corporation, product name "PG-02"), and measurements were taken at 10 random points, and the average value was calculated. The total thickness of the adhesive sheet is determined by measuring the thickness of the adhesive sheet with a release sheet and subtracting the thickness of the release sheet from the measured thickness. The thickness of the buffer layer is the thickness of the substrate with the buffer layer minus the thickness of the substrate. The thickness of the surface coating layer is the thickness of the surface coating layer with the release sheet minus the thickness of the release sheet. The thickness of the adhesive layer is the total thickness of the adhesive sheet minus the thicknesses of the surface coating layer, buffer layer, and substrate.

[0132] [Measurement of water contact angle of surface coating layer] The water contact angle of the surface coating layer was measured in accordance with JIS R 3257: 1999. Specifically, the release sheet on the surface coating layer side of the PSA sheets produced in the Examples and Comparative Examples was peeled off, and purified water was dropped onto the exposed surface of the surface coating layer, and the static contact angle when this was measured under the following conditions using a fully automatic contact angle measuring meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DM-701"). ·Measurement temperature: 23℃ Purified water droplet volume: 2 μl ·Measurement time: 1 second after dropping Image analysis method: θ / 2 method

[0133] [Evaluation of the amount of grinding debris attached to the surface coating layer] The pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples were cut into 5 cm squares, and the release sheet on the surface coating layer side was peeled off to expose the surface coating layer to prepare test specimens. One of the four corners of the test specimen was fixed and suspended, and the specimen was immersed for 1 minute in grinding water containing 2% by mass of silicon wafer grinding dust. The test specimen was removed from the grinding water and left to dry at 23°C for 24 hours while still suspended. The surface coating layer of the test specimen was then visually observed, and the amount of grinding dust adhesion was evaluated according to the following criteria. In the following evaluation criteria, "grinding dust adhesion area" refers to an island-like grinding dust adhesion area formed by drying droplets of grinding water adhering to the surface coating layer. A: There is one area on the surface coating layer where grinding chips have adhered, or there is no grinding chips attached to the surface to the extent that they can be distinguished from the area where grinding chips have adhered. B: There are 2 to 5 areas where grinding dust has adhered on the surface coating layer. C: There are six or more areas where grinding dust has adhered on the surface coating layer, but no grinding dust has adhered to the entire surface of the surface coating layer. D: Grinding dust adheres to the entire surface of the surface coating layer.

[0134] [Preparation of urethane acrylate oligomer for use in buffer layer] Manufacturing Example 1 A bifunctional urethane acrylate oligomer having a mass average molecular weight (Mw) of 5,000 was obtained by reacting a terminal isocyanate urethane prepolymer obtained by reacting a polyester diol with isophorone diisocyanate with 2-hydroxyethyl acrylate.

[0135] [Preparation of energy ray-curable acrylic resin for use in adhesive layer] Manufacturing Example 2 An acrylic polymer was obtained by copolymerizing 52 parts by mass of n-butyl acrylate, 20 parts by mass of methyl methacrylate, and 28 parts by mass of 2-hydroxyethyl acrylate. 2-Methacryloyloxyethyl isocyanate was then added to the acrylic polymer so as to add to 90 mol% of the total hydroxyl groups of the acrylic polymer, thereby obtaining an energy beam-curable acrylic resin with a mass average molecular weight (Mw) of 500,000.

[0136] [Adhesive sheet manufacturing] Examples 1 to 3, Comparative Examples 1 to 3 Next, a pressure-sensitive adhesive sheet was produced by the following method: In the following explanation, the amount of each component refers to the amount of the active ingredient.

[0137] (1) Preparation of the substrate As a substrate, a polyethylene terephthalate film (Young's modulus: 2500 MPa) having a thickness of 50 μm was prepared.

[0138] (2) Preparation of coating solution for surface coating layer In Examples 1 to 3 and Comparative Examples 1 and 2, the resins shown in Table 1 were dissolved in toluene so that the concentration of the active ingredient was 10% by mass, and the solution was used as a coating liquid for the surface coating layer. In Comparative Example 3, 100 parts by mass of the resin shown in Table 1 and 30 parts by mass of silica filler (manufactured by Nissan Chemical Industries, Ltd., product name "Snowtex (registered trademark) UP") were dissolved and dispersed in toluene so that the active ingredient concentration was 5% by mass, to prepare a coating liquid for the surface coating layer.

[0139] (3) Preparation of buffer layer-forming composition A composition for forming a buffer layer was prepared by blending 40 parts by mass of the urethane acrylate oligomer obtained in Production Example 1, 40 parts by mass of isobornyl acrylate, 20 parts by mass of 2-hydroxy-3-phenoxypropyl acrylate, 2.0 parts by mass of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator, and 0.2 parts by mass of a phthalocyanine pigment.

[0140] (4) Preparation of adhesive composition A pressure-sensitive adhesive composition was prepared by blending 100 parts by mass of the energy ray-curable acrylic resin obtained in Production Example 2, 6 parts by mass of a polyfunctional urethane acrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name "Shikou UT-4332", mass average molecular weight (Mw) 4,700) as an energy ray-curable compound, 0.375 parts by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L"), and 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as a photopolymerization initiator, and diluting the mixture with a solvent.

[0141] (5) Preparation of adhesive sheet The buffer layer-forming composition obtained above was applied to one surface of the substrate, and then the substrate was exposed to light at an illuminance of 160 mW / cm 2 , irradiation amount 500mJ / cm 2 The buffer layer-forming composition was cured by irradiating it with ultraviolet light under the conditions above, thereby producing a substrate with a buffer layer having a thickness of 13 μm on one surface of the substrate. The adhesive composition obtained above was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") so that the thickness after drying was 20 μm, and then heated and dried to prepare a release sheet with an adhesive layer. The adhesive layer of this release sheet with an adhesive layer was attached to the side of the buffer layer-attached substrate where the buffer layer was not provided, to prepare a laminate having the buffer layer, substrate, and adhesive layer in this order. The surface coating layer coating solution obtained above was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") using a Mayer bar so that the thickness after drying would be 2 μm, and then heated and dried to prepare a surface coating layer with a release sheet. The surface coating layer of this surface coating layer with a release sheet was attached to the surface of the buffer layer of the laminate to obtain a pressure-sensitive adhesive sheet having the surface coating layer, buffer layer, substrate, and pressure-sensitive adhesive layer in this order.

[0142] Table 1 shows the evaluation results of the pressure-sensitive adhesive sheets obtained in the examples and comparative examples.

[0143] [Table 1]

[0144] Maleic anhydride-modified polyolefin resin: propylene-butene-maleic anhydride copolymer, maleic anhydride modification rate: 1.5% by mass, mass average molecular weight (Mw): 75,000, heteroatom content: 0.735% by mass, manufactured by Toyobo Co., Ltd., product name "TOYOTAC (registered trademark) PMA-L" Ethylene-cyclic olefin copolymer: ethylene-tetracyclododecene copolymer, content of structural units derived from tetracyclododecene: 20 to 32 mol%, heteroatom content: 5.2 mass%, manufactured by Mitsui Chemicals, Inc., trade name "APEL (registered trademark) APL6509T" Ethylene-vinyl acetate copolymer: vinyl acetate content: 14% by mass, heteroatom content: 0% by mass, manufactured by Toyobo Co., Ltd., trade name "Ultrathene (registered trademark) 685" Polyester resin: Toyobo Co., Ltd., product name "Vylon (registered trademark) GK-680" Polyester urethane resin: Toyobo Co., Ltd., product name "Vylon (registered trademark) UR-4410" Epoxy acrylate resin: Arkema, product name "CN104 NS"

[0145] It can be seen from Table 1 that the amount of grinding dust adhesion was sufficiently reduced in the pressure-sensitive adhesive sheets of Examples 1 to 3, in which the surface coating layer had a water contact angle of 85° or more. On the other hand, the amount of grinding dust adhesion was not sufficiently reduced in the pressure-sensitive adhesive sheets of Comparative Examples 1 to 3, in which the surface coating layer had a water contact angle of less than 85°.

Claims

1. The film has a surface coating layer, a buffer layer, a substrate, and a pressure-sensitive adhesive layer in this order, the static contact angle of water with the surface coating layer at 23°C is 85° or more; The adhesive sheet for semiconductor processing, wherein the surface coating layer is an organic layer containing a resin component.

2. The adhesive sheet for semiconductor processing according to claim 1 , wherein the resin component is a thermoplastic resin.

3. The adhesive sheet for semiconductor processing according to claim 1 or 2, wherein the resin component has a heteroatom content of 7 mass % or less.

4. The adhesive sheet for semiconductor processing according to any one of claims 1 to 3, wherein the resin component dissolves in toluene at 23°C in an amount of 1 mass% or more.

5. A film having a surface coating layer, a buffer layer, a substrate, and an adhesive layer in this order, The adhesive sheet for semiconductor processing, wherein the static contact angle of water at 23°C with the surface coating layer is 85° or more, is used for back grinding of semiconductor wafers.

6. The adhesive sheet for semiconductor processing according to any one of claims 1 to 5, wherein the static contact angle of water at 23°C with the surface coating layer is 90° or more.

7. The adhesive sheet for semiconductor processing according to any one of claims 1 to 6, wherein the thickness of the surface coating layer is 0.05 to 10 µm.

8. The semiconductor processing adhesive sheet according to any one of claims 1 to 7, wherein the buffer layer is formed from a buffer layer-forming composition containing urethane (meth)acrylate.

9. A film having a surface coating layer, a buffer layer, a substrate, and an adhesive layer in this order, a step of attaching an adhesive sheet for semiconductor processing, in which the static contact angle of water at 23°C with the surface coating layer is 85° or more, to the surface of a semiconductor wafer with the adhesive layer as an attachment surface; grinding the back surface of the semiconductor wafer while the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer is fixed by a supporting device; A method for manufacturing a semiconductor device, comprising:

10. a dividing line forming step, which is a step a of forming grooves on the surface of the semiconductor wafer, or a step b of forming modified regions inside the semiconductor wafer from the surface or back surface of the semiconductor wafer; a sheet attaching step of attaching the semiconductor processing adhesive sheet according to any one of claims 1 to 8 to the surface of the semiconductor wafer with the adhesive layer as an attachment surface after the step a, or before or after the step b; a grinding and singulating step of grinding the back surface of the semiconductor wafer while the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer is fixed by a supporting device, and singulating the semiconductor wafer into a plurality of semiconductor chips starting from the grooves or modified regions; The method for manufacturing a semiconductor device according to claim 9 , comprising:

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