Manufacturing method of adhesive wafers and semiconductor devices for semiconductor processing

Abstract

Regarding an adhesive sheet for semiconductor processing, which sequentially comprises a surface coating, a buffer layer, a substrate, and an adhesive layer, wherein the aforementioned surface coating is a layer containing a polyolefin resin, and a method for manufacturing a semiconductor device using the adhesive sheet for semiconductor processing.

Description

Technical Field

[0001] This invention relates to a method for manufacturing an adhesive wafer for semiconductor processing and a semiconductor device. Prior Technology

[0002] The thinning, miniaturization, and multifunctionality of information terminal machines are rapidly advancing, and the semiconductor devices installed in these machines are also required to be thinner and denser. As a method for thinning semiconductor devices, there is a method for grinding the back side of a semiconductor wafer used in a semiconductor device. Back grinding of a semiconductor wafer involves attaching a back grinding adhesive sheet (hereinafter also referred to as a "back grinding sheet") to the surface of the semiconductor wafer, thereby protecting the surface of the semiconductor wafer. After back grinding, the back grinding sheet is peeled off from the surface of the semiconductor wafer.

[0003] In recent years, methods such as DBG (Deep Dig Grinding) and SDBG (Stealth Dig Grinding) have been put into practical use as grinding and monolithic methods to suppress damage to semiconductor wafers while simultaneously achieving thinning and wafer monolithicization. DBG involves creating grooves of a specified depth on the surface of a semiconductor wafer using a dicing tool, and then grinding from the back side of the wafer until the grooves are reached, thereby monolithicizing the semiconductor wafer. SDBG involves creating modified regions inside a semiconductor wafer by irradiation with laser light, and then grinding from the back side of the wafer, using these modified regions as the starting point for cutting, thus monolithicizing the semiconductor wafer. In both methods, a back-side grinding sheet is used to protect the surface of the semiconductor wafer.

[0004] With the development of such thinning process technologies, various reviews are being conducted on back-side grinding wafers to improve semiconductor wafer yield and thinning capabilities. Patent Document 1 discloses an adhesive sheet for protecting the surface of a semiconductor wafer, characterized in that it is applicable as an adhesive sheet for protecting the surface of a semiconductor wafer using either a pre-cutting method or a stealth pre-cutting method. The adhesive sheet has: a substrate film; an intermediate layer composed of an adhesive disposed on at least one side of the substrate film; and an outermost adhesive layer disposed on the outermost layer of the intermediate layer opposite to the substrate film, wherein the intermediate layer is formed by a material that has been hardened by a hardening process after the adhesive sheet is formed. [Previous Technical Documents] [Patent Literature]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2015-56446 Summary of the Invention

[0006] [The problem the invention aims to solve]

[0007] By using the semiconductor wafer surface protection adhesive film of Patent Document 1 to monolithize the semiconductor wafer into a chip, it can suppress the kerfshift of the original chip spacing, suppress the contamination of the semiconductor wafer caused by grinding chips, and prevent the residual adhesive phenomenon on the chip when peeling off the surface protection tape.

[0008] However, during back-side grinding, the side of the semiconductor wafer that is opposite to the side attached to the semiconductor wafer (hereinafter also referred to as the "back side") is fixed by a support device such as a chuck table. Then, the semiconductor wafer, which is fixed to the base of the support device through the back-side grinding sheet, is ground on the back side while cooling water is supplied to the grinding surface to remove heat and grinding debris generated during grinding.

[0009] During back-side grinding, if there are grinding chips between the back-side grinding wafer and the support holder, the following situation may occur: starting from the area where the grinding chips are present, cracks may form on the semiconductor wafer or semiconductor chip due to impacts during fixing the semiconductor wafer to the holder, pressure during back-side grinding, and vibration. Since the grinding chips adhere to the back side of the back-side grinding wafer in a state contained in cooling water, it is necessary to reduce the amount of grinding chips adhering to the back side of the back-side grinding wafer in order to suppress the formation of the aforementioned cracks. The adhesive sheet for protecting the surface of a semiconductor wafer in Patent Document 1 still cannot adequately meet the requirement of "reducing the amount of grinding chips on the back side of the back grinding sheet".

[0010] The present invention was made in view of the above-mentioned facts, and its purpose is to provide a semiconductor processing adhesive film with reduced grinding chip adhesion, and a method for manufacturing a semiconductor device using the semiconductor processing adhesive film. [Methods used to solve problems]

[0011] Through in-depth research, the inventors discovered that by using an adhesive sheet for semiconductor processing, which sequentially comprises a surface coating containing a polyolefin resin, a buffer layer, a substrate, and an adhesive layer, the above-mentioned problems can be solved, and thus the following invention is completed.

[0012] That is, the present invention relates to the following [1]~

[11] . [1]. An adhesive sheet for semiconductor processing, comprising, in sequence, a surface coating, a buffer layer, a substrate, and an adhesive layer. The aforementioned surface coating is a layer containing a polyolefin resin. [2]. The semiconductor processing adhesive film as described in [1] above, wherein the aforementioned polyolefin resin contains constituent units derived from chain olefins having 2 to 6 carbon atoms. [3]. The semiconductor processing adhesive film as described in [2] above, wherein the aforementioned polyolefin resin further contains constituent units derived from monomers having oxygen atoms and ethylene unsaturated bonds. [4]. The semiconductor processing adhesive film as described in [3] above, wherein the aforementioned single-system maleic anhydride has oxygen atoms and vinyl unsaturated bonds. [5]. The semiconductor processing adhesive film as described in [2] above, wherein the aforementioned polyolefin resin further contains constituent units derived from cyclic olefins. [6]. The semiconductor processing adhesive film as described in any of [1] to [5] above, wherein the polyolefin resin is dissolved in toluene at a concentration of 1% or more by mass before 23°C. [7]. The semiconductor processing adhesive sheet as described in any of [1] to [6] above, wherein the thickness of the aforementioned surface coating is 0.05 to 10 μm. [8]. The semiconductor processing adhesive sheet as described in any of [1] to [7] above, wherein the aforementioned buffer layer is formed from a buffer layer forming composition containing urethane (meth) acrylate. [9]. The adhesive sheet for semiconductor processing mentioned in any of [1] to [8] above is used for back-side grinding of semiconductor wafers.

[10] . A method for manufacturing a semiconductor device, comprising: The step of attaching the semiconductor processing adhesive sheet of any one of [1] to [9] above to the surface of the semiconductor wafer using the aforementioned adhesive layer as the attachment surface; and, The step of fixing the surface coating side of the aforementioned semiconductor processing adhesive sheet attached to the semiconductor wafer by means of a support device and grinding the back side of the aforementioned semiconductor wafer.

[11] . The semiconductor device manufacturing method as described in

[10] above includes: a step of forming predetermined dividing lines, a step of attaching a wafer, and a step of grinding and wafer modularization. The aforementioned step of forming the predetermined dividing line is step a, which involves forming a trench on the surface of the semiconductor wafer, or step b, which involves forming a modified region inside the semiconductor wafer from the surface or back side of the semiconductor wafer; The aforementioned step of attaching the sheet is performed after step a, or before or after step b, by attaching the semiconductor processing adhesive sheet of any one of [1] to [9] above to the surface of the aforementioned semiconductor wafer using the aforementioned adhesive layer as the attachment surface; The aforementioned grinding and monolithization steps involve fixing the surface coating side of the semiconductor processing adhesive film attached to the semiconductor wafer using a support device, grinding the back side of the semiconductor wafer, and monolithizing it into multiple semiconductor wafers starting from the aforementioned groove or modified region. [Invention Effects]

[0013] The present invention provides a semiconductor processing adhesive film with reduced grinding chip adhesion and a method for manufacturing a semiconductor device using the semiconductor processing adhesive film. Implementation

[0014] In this specification, the lower and upper limits of the preferred numerical range can be combined independently. For example, based on the statement "preferably 10~90, and even more preferably 30~60", the "preferably lower limit (10)" and the "even more preferably upper limit (60)" can be combined to become "10~60".

[0015] In this specification, for example, the term "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid," and other similar terms are used in the same way.

[0016] In this specification, the term "energy line" refers to rays containing energy quanta within electromagnetic waves or charged particle beams. Examples include ultraviolet light, radiation, and electron beams. For instance, ultraviolet light sources can be used, such as electrodeless lamps, high-pressure mercury lamps, metal halide lamps, and UV-LEDs. An electron beam is an electron beam generated using an electron beam accelerator. In this specification, the term "energy line aggregation property" refers to the property of aggregation through irradiation of energy lines. Similarly, the term "energy line hardening property" refers to the property of hardening through irradiation of energy lines, and the term "non-energy line hardening property" refers to the property of not possessing energy line hardening property.

[0017] In this specification, the term "surface" of a semiconductor wafer refers to the side on which circuitry is formed, and the term "back side" refers to the side on which circuitry is not formed.

[0018] The mechanism of action described in this specification is speculative and is not limited to the mechanism by which the semiconductor processing adhesive film of the present invention is effective.

[0019] [Adhesive wafers for semiconductor processing] The semiconductor processing adhesive sheet (hereinafter also referred to as "adhesive sheet") of this embodiment has, in sequence, a surface coating, a buffer layer, a substrate and an adhesive layer, wherein the aforementioned surface coating contains a polyolefin resin. The adhesive sheet of this embodiment is used to attach to the surface of a semiconductor device, which serves as a workpiece, to protect the surface while performing specified processing on the semiconductor device. After performing the specified processing on the workpiece, the adhesive sheet of this embodiment is peeled off from the semiconductor device. In this embodiment, the term "semiconductor device" refers to any device that functions by utilizing the characteristics of semiconductors, such as semiconductor wafers, semiconductor chips, electronic components containing semiconductor chips, and electronic machines incorporating such electronic components. Among these, the adhesive film of this embodiment is suitable for the processing of semiconductor wafers.

[0020] The adhesive sheet of this embodiment may have layers other than a surface coating, a buffer layer, a substrate, and an adhesive layer, or it may not have any of these layers. Examples of layers other than the substrate and adhesive layer include: an intermediate layer disposed between the substrate and the adhesive layer, and a release sheet disposed on the side of the adhesive layer opposite to the substrate. The components constituting the adhesive sheet of this embodiment will be described in sequence below.

[0021] <Surface Coating> The surface coating is a layer disposed on the side of the buffer layer opposite to the substrate. During the processing of semiconductor devices, the surface coating is a layer that is fixed by a support device. The surface coating contains a layer of polyolefin resin, which has the property that water containing grinding chips is difficult to adhere to. Therefore, in this embodiment of the adhesive sheet, the amount of grinding chips adhering to the back side is reduced, and workpiece damage caused by grinding chips adhering to the back side can be suppressed.

[0022] (Polyolefin resins) The polyolefin resin contained in the surface coating is a resin polymerized from monomers containing at least an olefin. In this embodiment, "polyolefin resin" refers to any resin that is homopolymerized with olefins or copolymerized with monomers other than olefins, and contains at least 50% by mass of olefin-derived constituent units. Furthermore, the term "olefin" in this embodiment refers to an unsaturated hydrocarbon with ethylene-like unsaturated bonds, and compounds containing heteroatoms are excluded from the definition of "olefin" in this embodiment. Furthermore, the term "ethylene unsaturated bond" in this embodiment refers to a carbon-carbon double bond that can undergo additional reactions, and is defined as a double bond that does not contain an aromatic ring. Furthermore, in the following explanation, "a group containing an ethylene-like unsaturated bond" may be abbreviated as "unsaturated group". Polyolefin resins can be used alone or in combination of two or more.

[0023] The content of olefin-derived constituent units in polyolefin resins is not particularly limited, but 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 olefin-derived constituent units in polyolefin resins is at or above the above-mentioned lower limit, there is a tendency to further reduce the amount of grinding chips adhering to the resin. Furthermore, the content of olefin-derived constituent units in polyolefin resins can be 100% by mass, preferably 99.5% by mass or less, and even more preferably 99% by mass or less. When the content of olefin-derived constituent units in polyolefin resins is below the above-mentioned upper limit, it can contain constituent units derived from monomers other than olefins for purposes such as improving solvent solubility, and the formation of a surface coating by coating tends to become easier.

[0024] Examples of olefins that constitute polyolefin resins include chain olefins, cyclic olefins, and aromatic vinyl compounds. The olefin system constituting the polyolefin resin can be a single type or a combination of two or more types.

[0025] Examples of chain olefins 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 even more preferred.

[0026] Examples of cyclic olefins include monocyclic olefins such as cyclobutene, cyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, cycloheptene, and cyclooctene; cyclic dienes such as cyclohexadiene, methylcyclohexadiene, cyclooctadiene, methylcyclooctadiene, and phenylcyclooctadiene; and polycyclic olefins such as norcamphene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, and tetracyclo[7.4.0.110,13.02,7]decadecyl-2,4,6,11-tetraene. Among these, tetracyclododecene is preferred from the viewpoint of improving solvent solubility and thus facilitating the formation of a surface coating.

[0027] Examples of aromatic vinyl compounds include styrene, o-methylstyrene, m-methylstyrene, and p-methylstyrene.

[0028] Monomers other than olefins that can copolymerize with olefins include, for example, monomers having oxygen atoms and ethylene unsaturated bonds, monomers having nitrogen atoms and ethylene unsaturated bonds, etc. Monomers other than olefins can use a single type or a combination of two or more types.

[0029] Examples of monomers containing oxygen atoms and vinyl unsaturated bonds include anhydrides such as maleic anhydride, methylmaleic anhydride, dimethylmaleic anhydride, phenylmaleic anhydride, and diphenylmaleic anhydride; maleic acids such as maleic acid, methylmaleic acid, dimethyl maleate, diethyl maleate, dibutyl maleate, and monomethyl maleate; (meth)acrylic acid and (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cycloalkyl (meth)acrylates with 3 to 20 carbon atoms, benzyl (meth)acrylate, and isoborneol (meth)acrylate; and vinyl ester compounds such as vinyl acetate and vinyl propionate. Among these, from the viewpoint of improving solvent solubility and thus facilitating the formation of a surface coating, anhydrides and vinyl ester compounds are preferred, followed by maleic anhydride and vinyl acetate, and even more preferably maleic anhydride.

[0030] Examples of monomers containing nitrogen atoms and ethylene-like unsaturated bonds include maleimine compounds and their derivatives, and nitrile monomers. Examples of maleimide compounds and their derivatives 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.

[0031] Among the above constituent units, from the viewpoint of further reducing the amount of grinding chips, the polyolefin resin preferably contains a constituent unit derived from a chain olefin having 2 to 6 carbon atoms (hereinafter also referred to as "chain olefin constituent unit (A)"), and preferably contains one or more units selected from the group consisting of constituent units derived from ethylene and constituent units derived from propylene.

[0032] From the perspective of improving solvent solubility to facilitate the formation of surface coatings by coating, polyolefin resins preferably contain the aforementioned chain olefin constituent unit (A) and constituent units derived from monomers having oxygen atoms and ethylene unsaturated bonds (hereinafter also referred to as "constituent units containing oxygen atoms (B)"). When a polyolefin resin contains a chain olefin constituent unit (A) and a constituent unit (B) containing an oxygen atom, the content of the chain olefin constituent unit (A) in the polyolefin resin is not particularly limited, but is preferably 80 to 99.5% by mass, more preferably 90 to 99% by mass, and even more preferably 95 to 98.8% by mass. When a polyolefin resin contains a chain olefin constituent unit (A) and a constituent unit containing oxygen atoms (B), the content of the constituent unit containing oxygen atoms (B) in the polyolefin resin is not particularly limited, but is preferably 0.5 to 20% by mass, more preferably 1 to 10% by mass, and even more preferably 1.2 to 5% by mass. When the content of the chain olefinic unit (A) and the oxygen-containing unit (B) is within the above range, good solvent solubility can be obtained, while the amount of grinding chips adhering can be further reduced.

[0033] Furthermore, from the perspective of improving solvent solubility to facilitate the formation of surface coatings by coating, polyolefin resins preferably contain both the aforementioned chain olefin constituent units (A) and constituent units derived from cyclic olefins (hereinafter also referred to as "cyclic olefin constituent units (C)"). When a polyolefin resin contains both chain olefin units (A) and cyclic olefin units (C), the content of chain olefin units (A) in the polyolefin resin is not particularly limited, but is preferably 10-90% by mass, more preferably 20-70% by mass, and even more preferably 25-50% by mass. When a polyolefin resin contains both chain olefin units (A) and cyclic olefin units (C), the content of cyclic olefin units (C) in the polyolefin resin is not particularly limited, but is preferably 10-90% by mass, more preferably 30-80% by mass, and even more preferably 50-75% by mass. When the contents of the chain olefin constituent unit (A) and the cyclic olefin constituent unit (C) are within the above range, good solvent solubility can be obtained, while the amount of grinding chips adhering can be further reduced.

[0034] Examples of polyolefin resins include homopolymers of polyethylene, polypropylene, and polybutadiene; binary copolymers of ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-maleic anhydride copolymers, ethylene-vinyl acetate copolymers, ethylene-(meth)acrylate copolymers, ethylene-tetracyclododecene copolymers, propylene-butene copolymers, propylene-maleic anhydride copolymers, propylene-vinyl acetate copolymers, propylene-(meth)acrylate copolymers, and propylene-tetracyclododecene copolymers; and copolymers of ethylene-maleic anhydride-vinyl acetate, ethylene-maleic anhydride-(meth)acrylate, and ethylene-vinyl acetate-(meth)acrylate. Acrylic ester copolymers, propylene-maleic anhydride-vinyl acetate copolymers, propylene-maleic anhydride-(meth)acrylate copolymers, propylene-vinyl acetate-(meth)acrylate copolymers, ethylene-propylene-maleic anhydride copolymers, ethylene-propylene-vinyl acetate copolymers, ethylene-propylene-(meth)acrylate copolymers, ethylene-butene-maleic anhydride copolymers, ethylene-butene-vinyl acetate copolymers, ethylene-butene-(meth)acrylate copolymers, propylene-butene-maleic anhydride copolymers, propylene-butene-vinyl acetate copolymers, propylene-butene-(meth)acrylate copolymers, and other multi-component polymers. Among these, from the perspective of further reducing the amount of grinding chips adhering and from the perspective of improving solvent solubility to facilitate the formation of the surface coating by coating, ethylene-vinyl acetate copolymer, ethylene-tetracyclododecene copolymer, ethylene-butene-maleic anhydride copolymer, and even more preferably ethylene-butene-maleic anhydride copolymer are preferred.

[0035] From the perspective of facilitating the formation of surface coatings by application, polyolefin resins are preferably soluble in organic solvents. Specifically, at 23°C, polyolefin resins are preferably soluble in at least 1% by mass of toluene, more preferably at least 5% by mass, and even more preferably at least 8% by mass.

[0036] The content of heteroatoms in polyolefin resins is not particularly limited, but it is preferably below 7% by mass, more preferably 0.2 to 4% by mass, and even more preferably 0.5 to 1% by mass. When the heteroatom content in the polyolefin resin is below the aforementioned upper limit, it tends to further reduce the amount of grinding chips adhering. Furthermore, when the heteroatom content in the polyolefin resin is above the aforementioned lower limit, solvent solubility increases, and the formation of a surface coating tends to become easier. In this specification, "heteroatoms" refers to all atoms other than carbon and hydrogen atoms.

[0037] Without compromising the effects of the present invention, the surface coating may also contain other components. Examples of such other components include: resins other than polyolefin resins; additives such as antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, and dyes. The content of polyolefin resin relative to the total amount of surface coating is not particularly limited, but from the point of view of further reducing the amount of grinding chips, it is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, and even more preferably 98 to 100% by mass.

[0038] (Contact Angle) The static contact angle (hereinafter also referred to as "water contact angle") of the surface coating of the adhesive sheet of this embodiment is preferably 85° or more in water at 23°C. When the water contact angle of the surface coating is greater than 85°, water containing grinding chips is difficult to adhere to the surface coating, thus tending to further reduce the amount of grinding chips adhering. From the perspective of further reducing the amount of grinding chips adhering to the surface coating, the water contact angle of the surface coating is preferably 90° or higher, more preferably 93° or higher, and even more preferably 96° or higher. There is no particular upper limit to the water contact angle of the surface coating; from the perspective of ease of manufacturing, for example, it can be 150° or lower, or even 100° or lower. The water contact angle of the surface coating is a value obtained by measurement according to JIS R 3257:1999, and can be measured by the method described in the embodiments.

[0039] The thickness of the surface coating is not particularly limited, but it is preferably 0.05~10μm, even more preferably 0.2~7μm, and even more preferably 1~4μm. When the thickness of the surface coating is above the aforementioned lower limit, a uniform layer can be formed, and it tends to sufficiently reduce the amount of grinding chips adhering to it. Furthermore, when the thickness of the surface coating is below the aforementioned upper limit, it tends to easily obtain a buffer layer that absorbs the unevenness of foreign objects such as those on the chuck.

[0040] <Buffer Layer> The buffer layer is a layer disposed between the substrate and the surface coating. The buffer layer serves the following functions: absorbing vibrations and impacts generated during back-side grinding to prevent the workpiece from cracking. Furthermore, by providing the buffer layer, unevenness or irregularities such as foreign objects present on the support device seat can also be absorbed, thereby improving the retention of the adhesive sheet by the support device.

[0041] (Components for forming a buffer layer) The buffer layer can be formed by the composition of the buffer layer. From the perspective of obtaining suitable physical properties for a buffer layer, a preferred buffer layer is one obtained by hardening a buffer layer composition containing an energy-line polymerizable compound with energy lines. The composition for forming the buffer layer, as an energy-line polymerizable compound, is preferably a composition containing urethane (meth)acrylate (a1). The composition for forming the buffer layer, by containing urethane (meth)acrylate (a1), tends to adjust the storage modulus and other properties of the buffer layer to a favorable range. Furthermore, from the same viewpoint, the composition for forming the buffer layer is preferably: in addition to urethane (meth)acrylate (a1), it also contains one or more polymeric compounds selected from the group consisting of alicyclic or heterocyclic groups having 6 to 20 ring-forming atoms (a2) and polymeric compounds having functional groups (a3); the composition for forming the buffer layer is more preferably: in addition to urethane (meth)acrylate (a1), it also contains polymeric compounds (a2) having alicyclic or heterocyclic groups having 6 to 20 ring-forming atoms and polymeric compounds having functional groups (a3).

[0042] [Aminocarbamate (meth)acrylate (a1)] Aminocarbamate (meth)acrylate (a1) is a compound having (meth)acrylic acid and aminocarbamate bonds, and is a compound that can be polymerized by energy beam irradiation. The amino carbamate (meth) acrylate (a1) system can be used alone or in combination with two or more types.

[0043] 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 this embodiment, the mass average molecular weight (Mw) refers to the value converted from standard polystyrene obtained by gel permeation chromatography (GPC), specifically the value obtained by the method described in the examples.

[0044] The number of (meth)acrylic acid esters (a1) 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.

[0045] For example, urethane (meth)acrylates can be obtained by the following reaction: reacting a polyol compound with a polyisocyanate compound to obtain a terminal isocyanate urethane prepolymer, and then reacting a hydroxyl-containing (meth)acrylate with the prepolymer.

[0046] As a polyol compound, it is not particularly limited to any compound having two or more hydroxyl groups. Specific examples of polyol compounds include alkyl glycols, polyether polyols, polyester polyols, and polycarbonate polyols. Among these, polyester polyols are preferred. As a polyol compound, it can be any of a diol with two functions, a triol with three functions, or a polyol with four or more functions, preferably a diol with two functions, and even more preferably a polyester-type diol. A single polyol compound can be used, or two or more can be used in combination.

[0047] Examples of polyisocyanate compounds include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, norcamphene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and ω,ω'-diisocyanate dimethylcyclohexane; and aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, xylylene diisocyanate, benzylamine diisocyanate, tetramethylene xylylene diisocyanate, and naphthalene-1,5-diisocyanate. Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferred. A single polyisocyanate compound can be used, or two or more compounds can be used in combination.

[0048] As a hydroxyl-containing (meth)acrylate that reacts with terminal isocyanate carbamate prepolymers, it is not particularly limited as long as it is a compound having at least a hydroxyl group and a (meth)acrylic group in one molecule. Examples of hydroxyl-containing (meth)acrylates include, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 5-hydroxycyclooctyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, neopentyl tetramethylol(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, etc.; hydroxyl-containing (meth)acrylamides such as N-hydroxymethyl(meth)acrylamide; and reactants obtained by reacting (meth)acrylate with vinyl alcohol, vinylphenol, or diglycidyl bisphenol A. Among these, hydroxyalkyl (meth)acrylates are preferred, and 2-hydroxyethyl (meth)acrylate is even more preferred. (Meth)acrylates containing hydroxyl groups can be used alone or in combination with two or more.

[0049] The conditions for reacting the terminal isocyanate urethane prepolymer with the hydroxyl-containing (meth)acrylate are not particularly limited, and can be set to, for example, the following conditions: in the presence of solvents, catalysts, etc., added as needed, the reaction is carried out at 60 to 100°C for 1 to 4 hours.

[0050] The content of urethane (meth) acrylate (a1) in the composition for forming the buffer layer is not particularly limited, but it is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and even more preferably 30 to 50% by mass, relative to the total amount (100% by mass) of the active ingredient in the composition for forming the buffer layer. In this embodiment, the effective component of the buffer layer forming composition refers to the component remaining after removing organic solvents and other components that are removed during the formation of the buffer layer from the components contained in the buffer layer forming composition.

[0051] [Polymerizable compounds having alicyclic or heterocyclic groups with 6 to 20 ring-forming atoms (a2)] The composition for forming a buffer layer is a polymeric compound (a2) containing alicyclic or heterocyclic groups having 6 to 20 ring-forming atoms (hereinafter also referred to as "polymeric compound (a2) containing alicyclic or heterocyclic groups"), which tends to improve the film-forming properties of the composition for forming a buffer layer. The so-called ring-forming atom number refers to the number of atoms constituting the ring itself in a compound whose structure is formed by atoms bonded in a ring. Atoms that do not form a ring (such as hydrogen atoms bonded to the atoms constituting the ring) and atoms contained in substituents when the ring is substituted are not included in the ring-forming atom number. Examples of atoms that form a ring structure for heterocyclic groups include carbon atoms, nitrogen atoms, oxygen atoms, and sulfur atoms. Polymerizable compounds (a2) with alicyclic or heterocyclic groups can be used alone or in combination with two or more.

[0052] Polymerizable compounds having alicyclic or heterocyclic groups (a2) are preferably compounds having (meth)acrylic groups. The polymeric compound (a2) having an alicyclic or heterocyclic group, wherein the number of (meth)acrylic acid groups in one molecule is not particularly limited, but preferably one or more, more preferably one or two, and even more preferably one.

[0053] The polymeric compound (a2) having an alicyclic or heterocyclic group has 6 to 20 ring-forming atoms in its alicyclic or heterocyclic group, preferably 6 to 18, even more preferably 6 to 16, and even more preferably 7 to 12.

[0054] Examples of polymeric compounds (a2) containing alicyclic or heterocyclic groups include isocamphene methacrylate, dicyclopentenyl methacrylate, dicyclopentyl methacrylate, dicyclopentenyl methacrylate, cyclohexyl methacrylate, adamantane methacrylate, and other alicyclic (meth)acrylates; and heterocyclic (meth)acrylates such as tetrahydrofurfuryl methacrylate and morphofolin methacrylate. Among these, alicyclic (meth)acrylates are preferred, and isocamphene methacrylate is even more preferred.

[0055] The content of polymeric compounds (a2) having alicyclic or heterocyclic groups in the composition for forming a buffer layer is not particularly limited, but is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and even more preferably 30 to 50% by mass, relative to the total amount (100% by mass) of the active ingredient in the composition for forming a buffer layer.

[0056] [Polymerizable compounds with functional groups (a3)] The composition for forming a buffer layer has the tendency to adjust the viscosity of the composition for forming a buffer layer to an appropriate range by containing a polymeric compound (a3) ​​with functional groups. Polymers with functional groups (a3) ​​can be used alone or in combination of two or more.

[0057] The functional groups possessed by polymeric compounds (a3) ​​can be hydroxyl, epoxy, amide, and amino groups, for example. The polymeric compound (a3) ​​having functional groups has one or more functional groups in one molecule, preferably one to three, more preferably one or two, and even more preferably one.

[0058] The polymeric compound having a functional group (a3) ​​is preferably a compound having a functional group together with a (meth)acrylic acid group. The number of (meth)acrylic acid groups in one molecule of the polymeric compound (a3) ​​having a functional group is not particularly limited, but it is preferably one or more, more preferably one or two, and even more preferably one.

[0059] Examples of polymeric compounds with functional groups (a3) ​​include polymeric compounds containing hydroxyl groups, polymeric compounds containing epoxy groups, polymeric compounds containing amide groups, and polymeric compounds containing amine groups.

[0060] Examples of hydroxyl-containing polymeric compounds include hydroxyl-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.

[0061] Examples of epoxy-containing polymeric compounds include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

[0062] Examples of polymeric compounds containing amide groups include (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-hydroxymethylpropane (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and N-vinylmethylamine.

[0063] Examples of amino-containing polymeric compounds include (meth)acrylates containing primary amino groups, (meth)acrylates containing secondary amino groups, (meth)acrylates containing tertiary amino groups, and other amino-containing (meth)acrylates.

[0064] Among these, hydroxyl-containing (meth)acrylates are preferred, and hydroxyl-containing (meth)acrylates with aromatic rings, such as 2-hydroxy-3-phenoxypropyl (meth)acrylate, are even more preferred.

[0065] The content of the functional polymeric compound (a3) ​​in the composition for forming the buffer layer is not particularly limited, but it is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and even more preferably 15 to 25% by mass, relative to the total amount (100% by mass) of the effective component of the composition for forming the buffer layer.

[0066] [Other polymeric compounds] Without compromising the effectiveness of the present invention, the composition for forming the buffer layer may also contain other polymeric compounds besides components (a1) to (a3). Other examples of polymerizable compounds include alkyl (meth)acrylates having alkyl groups having 1 to 20 carbon atoms; vinyl compounds such as styrene, N-vinylpyrrolidone, and N-vinylcaprolactam. Other polymeric compounds can be used alone or in combination of two or more. The content of other polymeric compounds in the composition for forming the buffer layer is not particularly limited, but is preferably 0 to 20% by mass relative to the total amount (100% by mass) of the effective components of the composition for forming the buffer layer, more preferably 0 to 10% by mass, and even more preferably 0 to 2% by mass.

[0067] [Photopolymerization initiator] The composition for forming a buffer layer containing a polymerizable compound is preferably further containing a photopolymerization initiator, from the viewpoint of reducing the polymerization time and the amount of energy irradiation during energy irradiation. A single photopolymerization initiator can be used, or two or more can be used in combination.

[0068] Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, phosphine oxide compounds, titanoceramsite compounds, thioxanthone compounds, peroxide compounds, and further, photosensitizers such as amines and benzoquinones. More specifically, examples include 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-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-hydroxycyclohexylphenyl ketone is preferred.

[0069] The content of the photopolymerization initiator in the composition for forming the buffer layer is not particularly limited. From the viewpoint that the energy line hardening reaction can be carried out homogeneously and sufficiently, it is preferably 0.05 to 15 parts by mass relative to 100 parts by mass of the energy line polymerizable compound, more preferably 0.1 to 10 parts by mass, and even more preferably 0.3 to 5 parts by mass.

[0070] (Other ingredients) Without impairing the effects of the present invention, the composition for forming the buffer layer may also contain other components. Examples of other components include: resin components other than the resins mentioned above; additives such as antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, and dyes. The content of other resin components in the composition for forming the buffer layer is not particularly limited, but it is preferably 0 to 20% by mass relative to the total amount (100% by mass) of the effective components in the composition for forming the buffer layer, more preferably 0 to 10% by mass, and even more preferably 0 to 2% by mass. The content of other additives in the composition for forming the buffer layer is not particularly limited, but is preferably 0 to 6% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.1 to 3% by mass, relative to the total amount (100% by mass) of the effective components in the composition for forming the buffer layer.

[0071] (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, it is preferably less than 1,200 MPa, and more preferably less than 900 MPa. Furthermore, the Young's modulus of the buffer layer at 23°C is preferably 50 MPa or more, and more preferably 100 MPa or more. When the Young's modulus of the buffer layer at 23°C is below the upper limit mentioned above, the absorption of vibrations and impacts generated during back-side grinding and the retention of the adhesive sheet tend to improve. Furthermore, when the Young's modulus of the buffer layer at 23°C is above the lower limit mentioned above, it tends to suppress excessive deformation of the buffer layer during workpiece processing. The Young's modulus of the buffer layer at 23°C can be measured according to JIS K 7127:1999 at a test speed of 200 mm / min.

[0072] (Stress mitigation rate of the buffer layer) The stress relief rate of the buffer layer is not particularly limited, but it is preferably 70~100%, even more preferably 75~100%, and even more preferably 78~98%. When the stress relief rate of the buffer layer is within the above range, the effect of absorbing vibrations and impacts generated during back-side grinding and the retention of the adhesive sheet will tend to be improved. The stress relief rate of the buffer layer is determined by cutting a 15mm×140mm piece from a 200μm thick buffer layer as a test piece, clamping the two ends of the test piece by 20mm, and using the stress A (N / m 2) when stretched by 10% at 200mm / min and the stress B (N / m 2) 1 minute after the stretching stops, using the following formula. Stress mitigation rate (%) = 100 × (AB) / A (%)

[0073] (Thickness of the buffer layer) The thickness of the buffer layer is not particularly limited, but it is preferably 10~70μm, even more preferably 15~50μm, and even more preferably 20~40μm. When the thickness of the buffer layer is above the lower limit mentioned above, the absorption of vibrations and impacts generated during back-side grinding and the retention of the adhesive sheet tend to improve. Furthermore, when the thickness of the buffer layer is below the upper limit mentioned above, it tends to suppress excessive deformation of the buffer layer during workpiece processing.

[0074] <Adhesive layer> The adhesive layer is disposed on the side of the substrate opposite to the buffer layer, and the adhesive layer is attached to the workpiece. The adhesive layer is preferably formed of a line-curing adhesive. Because the adhesive layer is formed of a line-curing adhesive, it can effectively protect the surface of the workpiece by having sufficient adhesion before line curing. After line curing, the peeling force is reduced, and it can be easily peeled off from the workpiece.

[0075] Examples of energy-line hardening adhesives include X-type adhesive compositions, Y-type adhesive compositions, and XY-type adhesive compositions, as described below. Type X adhesive composition: an energy-line curing adhesive composition containing a non-energy-line curing adhesive resin (hereinafter also referred to as "Adhesive Resin I") and an energy-line curing compound other than the adhesive resin. Y-type adhesive composition: an energy-line curing adhesive composition containing an energy-line curing adhesive resin (hereinafter also referred to as "Adhesive Resin II") with unsaturated groups introduced into the side chains of a non-energy-line curing adhesive resin, but not containing energy-line curing compounds other than adhesive resin. XY type adhesive composition: an energy-line curing adhesive composition containing the above-mentioned energy-line curing adhesive resin II and energy-line curing compounds other than adhesive resin. Of these, energy-line curing adhesives are preferably XY-type adhesive compositions. By using XY-type adhesive compositions, it is possible to achieve sufficient adhesion before curing, but with a tendency to sufficiently reduce the peel force on the workpiece after curing.

[0076] The adhesive that forms the adhesive layer can also be a layer formed by a non-energy-line hardening adhesive that does not harden even when exposed to energy lines. Examples of non-energy-line curing adhesives include adhesives containing adhesive resin I but not adhesive resin II or energy-line curing compounds.

[0077] Next, we will provide a more detailed explanation of the components that make up the adhesive layer. In the following description, "adhesive resin" is used to represent one or both of adhesive resin I and adhesive resin II. Furthermore, in the following description, when referred to solely as "adhesive composition," it is assumed to also include type X adhesive composition, type Y adhesive composition, type XY adhesive composition, and other adhesive compositions.

[0078] Examples of adhesive resins include acrylic resins, carbamate resins, rubber resins, and polysiloxane resins. Among these, acrylic resins are preferred.

[0079] (Acrylic resin) Acrylic resins are preferably those containing constituent units derived from alkyl (meth)acrylates. Examples of alkyl (meth)acrylates include alkyl (meth)acrylates in which the alkyl group has 1 to 20 carbon atoms. The alkyl groups in (meth)acrylates can be either straight-chain or branched.

[0080] From the perspective of further enhancing the adhesion of the adhesive layer, acrylic resins preferably contain (meth)acrylate alkyl esters derived from alkyl groups with 4 or more carbon atoms. The constituent units of (meth)acrylate alkyl esters with 4 or more carbon atoms derived from alkyl groups contained in acrylic resins may be one or two or more. The number of carbon atoms in the alkyl group of (meth)acrylate is preferably 4 to 12, more preferably 4 to 8, and even more preferably 4 to 6. Examples of alkyl (meth)acrylates having 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, and dodecyl (meth)acrylate. Among these, butyl (meth)acrylate is preferred, and butyl acrylate is even more preferred. When an acrylic resin contains a (meth)acrylate alkyl ester with 4 or more carbon atoms derived from an alkyl group, the content of this alkyl group, from the viewpoint of further enhancing the adhesion of the adhesive layer, is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 45 to 60% by mass.

[0081] From the perspective of making the storage modulus G' of the adhesive layer good and the adhesive properties good, acrylic resins preferably contain both (meth)acrylate alkyl esters with 4 or more carbon atoms derived from alkyl groups and (meth)acrylate alkyl esters with 1 to 3 carbon atoms derived from alkyl groups. The constituent units of acrylic resins, which are alkyl (meth)acrylates with 1 to 3 carbon atoms derived from alkyl groups, can be one or more. Alkyl methacrylates having 1 to 3 carbon atoms as alkyl groups include, for example, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, and n-propyl methacrylate. Among these, methyl methacrylate and ethyl methacrylate are preferred, methyl methacrylate is even more preferred, and methyl methacrylate is the most preferred. When an acrylic resin contains a (meth)acrylate alkyl ester derived from an alkyl group having 1 to 3 carbon atoms, the content of this alkyl ester is preferably 1 to 35% by mass, more preferably 5 to 30% by mass, and even more preferably 15 to 25% by mass in the acrylic resin.

[0082] Acrylic resins are preferred because they contain constituent units derived from monomers containing functional groups. Acrylic resins can incorporate the following functional groups by using building blocks derived from monomers containing functional groups: functional groups that serve as crosslinking initiation points for reactions with crosslinking agents, or functional groups that can react with compounds containing unsaturated groups to introduce unsaturated groups into the side chains of acrylic resins. The constituent units of acrylic resins, which are derived from monomers containing functional groups, can be one or more types.

[0083] Examples of monomers containing functional groups include monomers containing hydroxyl groups, monomers containing carboxyl groups, monomers containing amino groups, and monomers containing epoxy groups. Among these, monomers containing hydroxyl groups and monomers containing carboxyl groups are preferred, and monomers containing hydroxyl groups are even more preferred. Examples of monomers containing hydroxyl groups include hydroxyalkyl esters of (meth)acrylates such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate; and unsaturated alcohols such as vinyl alcohol and allyl alcohol. Examples of monomers containing carboxyl groups include vinyl unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; vinyl unsaturated dicarboxylic acids and their anhydrides such as formanoic acid, iconic acid, maleic acid, and citralic acid; and 2-carboxyethyl methacrylate.

[0084] When acrylic resins contain constituent units derived from monomers containing functional groups, the content is not particularly limited, but preferably 5 to 45% by mass, more preferably 15 to 40% by mass, and even more preferably 25 to 35% by mass in acrylic resins.

[0085] In addition to the constituent units mentioned above, acrylic resins may also contain constituent units derived from other monomers that can copolymerize with acrylic monomers. The constituent units of acrylic resins, which are derived from other monomers, can be one or more individual monomers. Other monomers include styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, and acrylamide.

[0086] To impart energy line hardening properties, acrylic resins can also be further incorporating unsaturated groups with energy line polymerization properties. Unsaturated groups can be introduced by, for example, reacting the functional group of an acrylic resin containing a monomer derived from a functional group with a reactive substituent of a compound having both a reactive substituent and an unsaturated group (hereinafter also referred to as a "compound containing an unsaturated group"), wherein the reactive substituent is reactive with the functional group. A single compound containing an unsaturated group may be used, or two or more may be used in combination. Examples of unsaturated groups in compounds containing unsaturated groups include (meth)acrylyl, vinyl, and allyl groups. Among these, (meth)acrylyl is preferred. Examples of reactive substituents in compounds containing unsaturated groups include isocyanate groups and glycidyl groups. Examples of compounds containing unsaturated groups include (meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, and (meth)acrylate epoxy propylene ester.

[0087] When an acrylic resin containing a monomer derived from a functional group reacts with a compound containing an unsaturated group, the ratio of the total number of functional groups in the acrylic resin to the functional groups reacting with the compound containing an unsaturated group 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 reacting with compounds containing unsaturated groups is within the above range, sufficient energy-based curing properties can be imparted to the acrylic resin, while the functional groups that have not reacted with compounds containing unsaturated groups can react with the crosslinking agent, thereby crosslinking the acrylic resin.

[0088] The mass average molecular weight (Mw) of acrylic resins is not particularly limited, but is preferably 300,000 to 1,500,000, even 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 layer tends to have better adhesion and cohesion.

[0089] (Energy line hardening compound) The energy-curing compound contained in the composition of X-type or XY-type adhesives is preferably a monomer or oligomer with an intramolecular unsaturated group that can be cured by energy-line irradiation. Examples of energy-line hardening compounds include poly(meth)acrylate monomers such as trimethylolpropane tri(meth)acrylate, neopentyl tert-methacrylate, neopentyl tert-methacrylate, dinepentyl tert-hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,6-hexanediol (meth)acrylate; and oligomers such as urethane (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, and epoxy (meth)acrylates. Among these, urethane (meth)acrylate oligomers are preferred from the viewpoint that they have a higher molecular weight and are less likely to reduce the modulus of the adhesive layer.

[0090] The molecular weight of the energy line hardening compound is not particularly limited, but is preferably 100-12,000, more preferably 200-10,000, even more preferably 400-8,000, and even more preferably 600-6,000. Furthermore, when the energy line hardening compound is an oligomer, the above molecular weights refer to the mass average molecular weight (Mw).

[0091] The content of the energy-line hardening compound in the X-type adhesive composition is not particularly limited, but is preferably 40 to 200 parts by weight relative to 100 parts by weight of adhesive resin, more preferably 50 to 150 parts by weight, and even more preferably 60 to 90 parts by weight. When the content of the energy-curing compound in the X-type adhesive composition is within the above range, the balance between the adhesion before energy-line irradiation and the peelability after energy-line irradiation tends to become better.

[0092] The content of the energy line hardening compound in the XY type adhesive composition is not particularly limited, but is preferably 1 to 30 parts by weight relative to 100 parts by weight of adhesive resin, more preferably 2 to 20 parts by weight, and even more preferably 3 to 15 parts by weight. When the content of the energy-curing compound in the XY type adhesive composition is within the above range, the balance between the adhesive force before energy-line irradiation and the peel strength after energy-line irradiation tends to become better. Furthermore, the XY type adhesive composition has the following tendency: because the adhesive resin is energy-curing, even if the content of the energy-curing compound is low, the peel strength can be sufficiently reduced after energy-line irradiation.

[0093] (Cross-linking agent) The adhesive composition preferably contains a crosslinking agent. Crosslinking agents are, for example, those that crosslink adhesive resins by reacting with functional groups derived from monomers containing functional groups in the adhesive resin. A single crosslinking agent can be used, or two or more can be used in combination.

[0094] Examples of crosslinking agents include isocyanate-based crosslinking agents such as toluene diisocyanate, hexamethylene diisocyanate, and their additives; epoxy-based crosslinking agents such as ethylene glycol glycidyl ether; aziridine-based crosslinking agents such as hexa[1-(2-methyl)-aziridinyl]triphosphine triazine; and chelate-based crosslinking agents such as aluminum chelates. Among these, isocyanate-based crosslinking agents are preferred from the perspectives of further enhancing cohesive strength and ease of availability.

[0095] When the adhesive composition contains a crosslinking agent, the content is not particularly limited. From the viewpoint of allowing the crosslinking reaction to proceed adequately, it is preferably 0.01 to 10 parts by weight, more preferably 0.03 to 7 parts by weight, and even more preferably 0.05 to 4 parts by weight, relative to 100 parts by weight of the adhesive resin.

[0096] (Photopolymerization initiator) When the adhesive is an energy-line curing adhesive, the adhesive composition preferably contains a photopolymerization initiator. By including a photopolymerization initiator in the energy-line curing adhesive, it has the following tendency: even with relatively low-energy energy lines such as ultraviolet light, the energy-line curing adhesive can undergo a sufficient curing reaction. A single photopolymerization initiator can be used, or two or more can be used in combination.

[0097] Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, phosphine oxide compounds, titanoceramsite compounds, thioxanone compounds, peroxide compounds, and further, photosensitizers such as amines and benzoquinone. More specifically, examples include 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, bibenzyl, biacetyl, 8-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0098] When the energy line curing adhesive contains a photopolymerization initiator, the content is not particularly limited. From the viewpoint that the energy line curing reaction can be carried out homogeneously and sufficiently, it is preferably 0.01 to 10 parts by weight, more preferably 0.03 to 7 parts by weight, and even more preferably 0.05 to 5 parts by weight relative to 100 parts by weight of the adhesive resin.

[0099] (Other additives) Without impairing the effects of the present invention, the adhesive composition may also contain other additives. Examples of other additives include antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, and dyes. The content of other additives in the adhesive composition is not particularly limited, but is preferably 0 to 6% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.1 to 3% by mass, relative to the total amount (100% by mass) of the active ingredient in the adhesive composition. In this embodiment, the effective component of the adhesive composition refers to the component remaining after removing organic solvents and other components that are removed during the formation of the adhesive layer from the components contained in the adhesive composition.

[0100] (Organic solvents) From the perspective of further improving the coating properties of substrates, release films, etc., the adhesive composition can also be diluted with organic solvents to make it into a solution. Examples of organic solvents include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dimethyl ether, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol. Organic solvents can be used alone or in combination of two or more. Organic solvents can be used directly in the synthesis of adhesive resins, or one or more organic solvents other than those used in the synthesis can be added.

[0101] The storage modulus G' of the adhesive layer at 23°C is not particularly limited, but is preferably 0.05~0.5MPa, more preferably 0.1~0.4MPa, and even more preferably 0.12~0.3MPa. When the storage modulus G' of the adhesive layer at 23°C is within the above range, even if the surface of the workpiece is uneven, the resulting adhesive layer has excellent conformability to the uneven shape and tends to better protect the surface of the workpiece during processing. When the adhesive layer is formed by an energy-curing adhesive, the storage modulus G' of the adhesive layer means the storage modulus G' before curing by energy irradiation. The storage modulus G' of the adhesive layer at 23°C can be measured as follows: a 3mm thick adhesive layer is cut into a circle with a diameter of 8mm and used as a test piece. The measurement is performed using a viscoelastic measuring device, the torsional shear method, a frequency of 1Hz, and a measurement temperature of 23°C.

[0102] The thickness of the adhesive layer is not particularly limited, but it is preferably 5~100μm, more preferably 10~80μm, and even more preferably 15~60μm. When the thickness of the adhesive layer is above the lower limit mentioned above, excellent adhesion can be obtained, and it tends to better protect the surface of the workpiece during processing. Furthermore, when the thickness of the adhesive layer is below the upper limit mentioned above, the generation of tape debris during the cutting of the adhesive sheet can be suppressed, and it tends to better prevent workpiece breakage.

[0103] <Substrate> Examples of resin films can be used as substrates. Examples of resins constituting resin films include: polyethylene 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 copolymer, and norbornene resin; ethylene-based copolymers such as ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, and ethylene-(meth)acrylic acid copolymer; polyvinyl chloride such as polyvinyl chloride and vinyl chloride copolymer; polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and fully aromatic polyesters; and polyurethane, polyimide, polyamide, polycarbonate, fluoropolymers, polyacetal, modified polyphenylene ether, polyphenylene sulfide, polyurethane, polyetherketone, and acrylic polymers. The substrate can be a single-layer resin film composed of one or more resins selected from the above-mentioned resins, or it can be a laminated film formed by stacking two or more of the above-mentioned resin films. Alternatively, it can be a modified film such as a cross-linked film or an ionomer film of the aforementioned resins. Among the resin films, the substrate is preferably selected from one or more of polyester film, polyamide film, polyimide film and biaxially stretched polypropylene film, and is more preferably polyester film, and even more preferably polyethylene terephthalate film.

[0104] The Young's modulus of the substrate is not particularly limited, but it is preferably above 1,000 MPa, 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 above the lower limit mentioned above, the effect of suppressing vibration during workpiece processing tends to be further improved. Furthermore, when the Young's modulus of the substrate is below the upper limit mentioned above, the workability when attaching to the workpiece and the workability when peeling off the workpiece tends to become better. The Young's modulus of the substrate can be measured according to JIS K 7127:1999, at a test speed of 200 mm / min.

[0105] The thickness of the substrate is not particularly limited, but it is preferably 10~200μm, more preferably 25~100μm, and even more preferably 30~70μm. When the thickness of the substrate is above the lower limit mentioned above, it tends to have sufficient strength and can function as a support for adhesive sheets. Furthermore, when the thickness of the substrate is below the upper limit mentioned above, moderate flexibility can be obtained, and operability tends to be improved. The so-called "thickness of the substrate" refers to the total thickness of the substrate. When the substrate is composed of multiple layers, it means the total thickness of all the layers that make up the substrate.

[0106] Without compromising the effects of the present invention, the substrate may also contain plasticizers, lubricants, infrared absorbers, ultraviolet absorbers, fillers, colorants, antistatic agents, antioxidants, catalysts, etc. The substrate can be transparent or opaque, and can be colored or vapor-deposited as needed. From the perspective of improving adhesion to other layers, surface treatments such as halo treatment can be applied to at least one side of the substrate, and the substrate can also be coated with a coating for the purpose of improving adhesion.

[0107] <Peeling off the thin sheet> In this embodiment, an adhesive sheet can be attached to at least one of the surfaces of the adhesive layer and the surface coating. The release sheet protects the surface of the adhesive sheet by being peeled off and removed when the adhesive sheet is used, in a peelable manner. The peel sheet can be a peel sheet that has undergone single-sided peeling or a peel sheet that has undergone double-sided peeling. As a release sheet, a preferred example is a release sheet made by coating a release agent onto a release sheet substrate. As the substrate for the release sheet, a resin film is preferred. Examples of such resin films include polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film; and polyolefin films such as polypropylene film and polyethylene film. Examples of release agents include rubber-based elastomers such as polysiloxane resins, olefin resins, isoprene resins, and butadiene resins; long-chain alkyl resins, alkyd resins, and fluorinated resins. The thickness of the stripping sheet is not particularly limited, but it is preferably 5~200μm, more preferably 10~100μm, and even more preferably 20~50μm.

[0108] The total thickness of the adhesive sheet in this embodiment is not particularly limited, but is preferably 30~300μm, more preferably 40~220μm, and even more preferably 45~160μm. When the total thickness of the adhesive sheet is above the lower limit mentioned above, the adhesive properties of the adhesive layer and the impact absorption properties of the buffer layer can be maintained at an appropriate level, and there is a tendency to fully utilize its function as an adhesive sheet for semiconductor processing. However, when the total thickness of the adhesive sheet is below the upper limit mentioned above, the peeling force when peeling the workpiece from the adhesive sheet tends to decrease. In this embodiment, the so-called "total thickness of the adhesive sheet" refers to the thickness from the surface of the surface coating of the adhesive sheet to the surface of the adhesive layer. When a release sheet is provided, the thickness of the release sheet is not included in the total thickness.

[0109] <Manufacturing Method of Adhesive Sheets> The method for manufacturing the adhesive sheet in this embodiment is not particularly limited and can be manufactured by conventional methods. For example, the adhesive sheet of this embodiment can be manufactured by a method having the following steps: forming an adhesive layer on one side of the substrate (hereinafter also referred to as the "adhesive layer forming step"), forming a buffer layer on the other side of the substrate (hereinafter also referred to as the "buffer layer forming step"), and forming a surface coating on the side of the buffer layer opposite to the substrate (hereinafter also referred to as the "surface coating forming step"). Furthermore, the order of these steps is not particularly limited, and they can be performed simultaneously if possible.

[0110] The adhesive layer forming step can be, for example, the following methods: a method of bonding an adhesive layer formed on a release sheet to the surface of a substrate; or a method of forming an adhesive layer by directly applying an adhesive composition to the surface of a substrate. The buffer layer forming step can be, for example, the following methods: a method of attaching a buffer layer formed on a release sheet to the surface of a substrate; or a method of forming a buffer layer by directly applying a buffer layer forming composition to the surface of a substrate. The surface coating forming step can be, for example, the following methods: a method of attaching a surface coating formed on a release sheet to the surface of a buffer layer on a substrate; or a method of forming a surface coating by directly applying a surface coating to the surface of a buffer layer on a substrate using a coating liquid. Alternatively, the buffer layer forming step and the surface coating forming step can also be performed by the following method: after sequentially applying the surface coating and the buffer layer on the release sheet, the buffer layer is then bonded to the surface of the substrate.

[0111] As a method for forming an adhesive layer, buffer layer or surface coating on a release sheet, one example is the following method: after applying an adhesive composition, buffer layer forming composition or surface coating coating liquid to the release sheet by conventional methods, the release sheet is subjected to energy beam irradiation, heating and drying as required.

[0112] Methods for applying adhesive components, buffer layer forming components, or surface coating liquids include, for example, spin coating, spray coating, bar coating, doctor blade coating, roller coating, blade coating, die coating, and gravure coating.

[0113] When the composition for forming the buffer layer contains an energy-line polymerizable compound, the irradiation can be performed in one session or in multiple sessions through a hardening process involving energy line irradiation. When performing a one-time curing process, the buffer layer forming composition can be coated onto the substrate and then completely cured by energy beam irradiation. Alternatively, the buffer layer forming composition can be completely cured on a release film before being bonded to the substrate. When the curing process is performed in multiple stages, after the coating film of the buffer layer forming composition is formed on the release film, the buffer layer forming composition is not fully cured on the release film, but is cured to a semi-cured state and then bonded to the substrate. Afterwards, the buffer layer forming composition can be fully cured again by irradiation with energy lines. The energy rays irradiated during the hardening treatment of the components used to form the buffer layer are preferably ultraviolet rays. When the composition for forming the buffer layer is hardened, the coating film of the composition for forming the buffer layer can be exposed to the outside while being irradiated with energy lines. However, it is preferable to cover the coating film with a peel-off sheet or substrate so that the coating film is not exposed to the outside while being irradiated with energy lines.

[0114] <Uses of Adhesive Sheets> Examples of workpiece processing that can be performed with the adhesive sheet of this embodiment attached include: back-side grinding, where one side of a semiconductor device has the adhesive sheet attached and the other side is ground; dicing of a semiconductor device with one side of the semiconductor device having the adhesive sheet attached; transporting semiconductor devices; and picking up semiconductor wafers. Among these, the adhesive sheet of this embodiment is suitable for back-side grinding, and even more suitable for: back-side grinding where the adhesive sheet of this embodiment is attached to the circuit forming surface of a semiconductor wafer and the back side of the semiconductor wafer is ground. In particular, since the adhesive sheet of this embodiment has the effect of suppressing crack formation during the thinning of semiconductor wafers, it is suitable for processes such as pre-dicing and stealth pre-dicing.

[0115] [Manufacturing Method of Semiconductor Devices] The method for manufacturing a semiconductor device according to this embodiment includes: The step of attaching the semiconductor processing adhesive sheet of this embodiment to the surface of a semiconductor wafer using the aforementioned adhesive layer as the attachment surface; and, The step of fixing the surface coating side of the aforementioned semiconductor processing adhesive sheet attached to the semiconductor wafer by means of a support device and grinding the back side of the aforementioned semiconductor wafer.

[0116] Furthermore, the manufacturing method of the semiconductor device in this embodiment preferably includes: a step of forming predetermined dividing lines, a step of attaching a thin film, and a step of grinding and monolithization. The aforementioned step of forming the predetermined dividing line is step a, which involves forming a trench on the surface of the semiconductor wafer, or step b, which involves forming a modified region inside the semiconductor wafer from the surface or back side of the semiconductor wafer; The aforementioned step of attaching the film is performed after step a, or before or after step b, by attaching the semiconductor processing adhesive film of this embodiment to the surface of the semiconductor wafer using the aforementioned adhesive layer as the attachment surface; The aforementioned grinding and monolithization steps involve fixing the surface coating side of the semiconductor processing adhesive film attached to the semiconductor wafer using a support device, grinding the back side of the semiconductor wafer, and monolithizing it into multiple semiconductor wafers starting from the aforementioned groove or modified region. Furthermore, the semiconductor device manufacturing method of this embodiment may also include a stripping step after the grinding and monolithization steps, wherein the aforementioned stripping step is to peel the semiconductor processing adhesive sheet of this embodiment from a plurality of semiconductor wafers. The manufacturing method of the semiconductor device having step a above is equivalent to the pre-cutting process; the manufacturing method of the semiconductor device having step b above is equivalent to the stealth pre-cutting process.

[0117] 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, and sapphire wafers. Among these, silicon wafers are preferred. Typically, circuits such as wiring, capacitors, diodes, and transistors are formed on the surface of a semiconductor wafer. These circuits can be formed using conventional methods such as etching and peeling. The thickness of semiconductor wafers before grinding is not particularly limited, but is usually 500~1,000 μm. The following describes in detail each step of the manufacturing method of the semiconductor device of this embodiment.

[0118] <Steps for forming the predetermined dividing line> The step of forming the predetermined dividing line is either step a, which forms a trench on the surface of the semiconductor wafer, or step b, which forms a modified region inside the semiconductor wafer from the surface or back side of the semiconductor wafer.

[0119] Step a is the step of forming a trench on the surface of the semiconductor wafer, which is performed before the adhesive film is attached to the surface of the semiconductor wafer. The depth of the trench formed on the surface of the semiconductor wafer in step a is shallower than the thickness of the semiconductor wafer. After step a, the semiconductor wafer is back-ground down to the trench formed in step a, and is then divided into a plurality of semiconductor wafers. Therefore, the trench in step a is formed along the dividing line where the semiconductor wafer is divided and monolithically assembled into semiconductor wafers. The groove can be formed by cutting using conventional wafer dicing equipment.

[0120] Step b is the step of forming a modified region inside the semiconductor wafer from the surface or back side of the semiconductor wafer. It can be performed before or after the adhesive sheet is attached to the surface of the semiconductor wafer. The modified region in step b is formed inside the semiconductor wafer by using a laser with a focused illumination point inside the wafer. This modified region is a brittle portion within the semiconductor wafer, formed by thinning the wafer through back-side grinding or by the force applied during grinding. This modified region becomes the starting point for the semiconductor wafer to be monolithically assembled into semiconductor wafers. Therefore, the modified region is formed along the dividing line where the semiconductor wafer is diced and monolithically assembled into semiconductor wafers. Laser irradiation can be performed from either the surface or the back side of the semiconductor wafer. When step b is performed after the film attachment step, the semiconductor wafer can also be irradiated with laser through the film.

[0121] <Steps for attaching the thin film> The step of attaching the film is a step that involves attaching the film to the surface of a semiconductor wafer using an adhesive layer as the attachment surface, either after step a or before or after step b. There are no particular limitations on the method of attaching the adhesive sheet; conventional methods, such as using a laminating machine, can be applied.

[0122] <Grinding and Single-piece Assembly Steps> The grinding and monolithization process involves fixing the surface coating side of the adhesive film attached to the semiconductor wafer using a support device, grinding the back side of the semiconductor wafer, and monolithizing multiple semiconductor wafers starting from the aforementioned grooves or modified regions. A semiconductor wafer with an adhesive film attached and grooves or modified regions formed thereon is fixed to the surface coating side of the adhesive film by a support device. The support device is not particularly limited, but a device such as a chuck or holder that adsorbs and holds the object in place is preferred.

[0123] Next, the back side of the fixed semiconductor wafer is ground to monolithize the semiconductor wafer into multiple semiconductor chips. When a trench is formed on a semiconductor wafer by step a, back-side grinding grinds the semiconductor wafer until the grinding surface reaches at least the bottom of the trench. By this back-side grinding, the trench becomes a cut through the wafer, and the semiconductor wafer is divided by the cut and monolithically processed into individual semiconductor wafers. On the other hand, when a modified region is formed on the semiconductor wafer through step b, the grinding surface may or may not reach the modified region completely. That is, the semiconductor wafer is destroyed and monolithically formed into a semiconductor chip by starting from the modified region, and grinding is performed until it is close to the modified region. For example, instead of monolithizing the semiconductor wafer, grinding is performed until it is close to the modified region, and then pick-up tape is attached to the semiconductor wafer. By stretching the pick-up tape, it is monolithically formed into a semiconductor chip.

[0124] The shape of a monolithic semiconductor wafer can be square or rectangular and other elongated shapes. The thickness of the monolithic semiconductor wafer is not particularly limited, but is preferably 5~100μm, more preferably 7~70μm, and even more preferably 10~45μm. The size of the monolithic semiconductor chip is not particularly limited, but it is preferably less than 50 mm², more preferably less than 30 mm², and even more preferably less than 10 mm².

[0125] <Peeling Steps> The peeling step is a step that follows the grinding and monolithization steps, in which the adhesive sheet is peeled off from multiple semiconductor wafers. When the adhesive layer of the adhesive sheet is formed by an energy-curing adhesive, the adhesive is cured by irradiating with energy lines, which reduces the peeling force of the adhesive layer and allows the adhesive sheet to be peeled off. Pick-up tape can also be used when peeling off the adhesive sheet. Pick-up tape can be made by, for example, an adhesive sheet having a substrate and an adhesive layer disposed on one side of the substrate. When using pick-up tape, first, attach the pick-up tape to the back side of the monolithized semiconductor wafer, aligning its position and orientation in a pick-up-able manner. At this time, also attach the ring frame positioned on the outer periphery of the semiconductor wafer to the pick-up tape, preferably securing the outer periphery of the pick-up tape to the ring frame. Next, peel the adhesive sheet from the plurality of semiconductor wafers fixed to the pick-up tape. Then, multiple semiconductor wafers located on the pick-up tape are picked up and fixed onto a substrate or the like to manufacture a semiconductor device. [Example]

[0126] The present invention will now be described in more detail with reference to embodiments, but the invention is not limited to these embodiments. The methods for measuring and evaluating various physical properties are as described below.

[0127] [Mass average molecular weight (Mw)] The mass-average molecular weight (Mw) was determined by converting to standard polystyrene using a gel permeation chromatography apparatus (manufactured by Tosoh Corporation, product name "HLC-8220") and under the conditions described below. (Measurement conditions) • Tubes: "TSK guard column HXL-H", "TSK gel GMHXL (×2)", "TSK gel G2000HXL" (all manufactured by Tosoh Corporation) • Column temperature: 40℃ • Developing solvent: Tetrahydrofuran • Flow rate: 1.0 mL / min

[0128] [Thickness measurement of adhesive sheets, etc.] The total thickness of the adhesive sheet, the thickness of each layer, and the thickness of the test piece made from them are measured using a constant pressure thickness gauge (manufactured by Teclock Corporation, trade name "PG-02"). At this time, 10 arbitrary points are measured and the average value is calculated. The total thickness of the adhesive sheet refers to the value obtained by measuring the thickness of the adhesive sheet with the release sheet attached, and then subtracting the thickness of the release sheet from that thickness. Furthermore, the thickness of the buffer layer refers to the value obtained by subtracting the thickness of the substrate from the thickness of the substrate to which the buffer layer is attached. Furthermore, the thickness of the surface coating refers to the value obtained by subtracting the thickness of the release liner from the thickness of the surface coating with the release liner attached. Furthermore, the thickness of the adhesive layer refers to the value obtained by subtracting the thickness of the surface coating, buffer layer, and substrate from the total thickness of the adhesive sheet.

[0129] [Measurement of water contact angle of surface coating] The water contact angle of the surface coating was measured according to JIS R 3257:1999. Specifically, the peeling sheet on the surface coating side of the adhesive sheet manufactured in the examples and comparative examples was peeled off, and the static contact angle when pure water was dropped onto the exposed surface coating was measured using a fully automatic contact angle measuring instrument (manufactured by Kyowa Interface Science Co., Ltd., product name "DM-701") under the following conditions. • Measurement temperature: 23℃ • Droplet volume of pure water: 2 μl • Measurement time: 1 second after the drop falls • Image analysis method: θ / 2 method

[0130] [Evaluation of the amount of grinding chips adhering to the surface coating] The adhesive sheets manufactured in the examples and comparative examples were cut into 5cm squares. The peeling sheet on the surface coating side was peeled off to prepare a test piece with the surface coating exposed. One corner of the test piece was fixed and suspended, and immersed in grinding water containing 2% by mass silicon wafer grinding chips for 1 minute. The test piece was removed from the grinding water and allowed to dry at 23°C for 24 hours while suspended. The surface coating of the test piece was then visually observed, and the amount of grinding chip adhesion was evaluated according to the following criteria. Note that in the following evaluation criteria, "grinding chip adhesion area" refers to the island-shaped grinding chip adhesion area formed by the drying of grinding water droplets adhering to the surface coating. A: A grinding chip attachment area with one location on the surface coating, or grinding chips that are not attached to the extent that can be identified as a grinding chip attachment area. B: Grinding chip adhesion areas with 2 to 5 locations on the surface coating. C: There are more than 6 grinding chip attachment points on the surface coating, but the grinding chips do not adhere to the entire surface of the surface coating. D: Grinding chips adhere to the entire surface of the coating.

[0131] [Preparation of urethane acrylate oligomers for use in buffer layers] Manufacturing Example 1 Polyester diol is reacted with isophorone diisocyanate, and the resulting terminal isocyanate urethane prepolymer is then reacted with 2-hydroxyethyl acrylate to obtain a difunctional urethane acrylate oligomer with a mass average molecular weight (Mw) of 5,000.

[0132] [Formulation of energy-line curing acrylic resin for use in adhesive layers] 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. Next, the acrylic polymer was reacted with 2-methacryloxyethyl isocyanate in such a manner that 90 moles of the hydroxyl groups in the total hydroxyl groups of the acrylic polymer were added, to obtain an energy-curable acrylic resin with a mass average molecular weight (Mw) of 500,000.

[0133] [Manufacturing of adhesive sheets] Examples 1-3, Comparative Examples 1-3 Next, the adhesive sheet will be manufactured using the method shown below. Note that the amounts of each component mentioned below refer to the total amount of the active ingredients.

[0134] (1) Preparation of substrate As a substrate, a polyethylene terephthalate film with a thickness of 50 μm (Young's modulus: 2500 MPa) was prepared.

[0135] (2) Preparation of coating liquid for surface coating Examples 1-3 and Comparative Examples 1-2 involved dissolving the resin shown in Table 1 in toluene at an effective ingredient concentration of 10% by mass, and using it as a coating liquid for surface coating. Comparative Example 3 involves dissolving and dispersing 100 parts by weight of the resin shown in Table 1 and 30 parts by weight of the silica filler (manufactured by Nissan Chemical Industries, Ltd., trade name "Snowtex (registered trademark) UP") in toluene at an effective ingredient concentration of 5% by weight, and using it as a coating liquid for surface coating.

[0136] (3) Modulation of components for forming the buffer layer The composition for forming a buffer layer was prepared by mixing 40 parts by mass of the urethane acrylate oligomer obtained in Manufacturing Example 1, 40 parts by mass of isoborneol acrylate, 20 parts by mass of 2-hydroxy-3-phenoxypropyl acrylate, 2.0 parts by mass of 1-hydroxycyclohexylphenyl ketone as a photopolymerization initiator, and 0.2 parts by mass of phthalocyanine pigment.

[0137] (4) Preparation of adhesive composition The adhesive composition was prepared by mixing 100 parts by mass of the energy-line curable acrylic resin obtained in Example 2, 6 parts by mass of the polyfunctional amino carbamate acrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "SHIKOH UT-4332", mass average molecular weight (Mw) 4,700) as the energy-line curable compound, 0.375 parts by mass of the isocyanate crosslinking agent (manufactured by Tosoh Co., Ltd., trade name "Coronate L"), and 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as the photopolymerization initiator, and by diluting with a solvent.

[0138] (5) Production of adhesive sheet After coating the aforementioned buffer layer forming composition onto one side of the substrate, the buffer layer forming composition is hardened by irradiating it with ultraviolet light under conditions of 160 mW / cm² illuminance and 500 mJ / cm² irradiation, thereby producing a buffer layer substrate with a buffer layer having a thickness of 13 μm on one side of the substrate. Furthermore, the adhesive composition obtained above was applied to the release surface of a release sheet (manufactured by Lintec Corporation, trade name "SP-PET381031") to a thickness of 20 μm after drying, and then heated and dried to produce a release sheet with an adhesive layer. By attaching the adhesive layer of the release sheet with the adhesive layer to the surface of a substrate with a buffer layer that is not provided with a buffer layer, a laminate having a buffer layer, a substrate, and an adhesive layer in sequence was produced. Furthermore, with a dried thickness of 2 μm, the aforementioned surface coating was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, trade name "SP-PET381031") using a mayer bar and then heated and dried to create a surface coating with the release sheet attached. This surface coating with the release sheet attached was then attached to the surface of the buffer layer of the aforementioned laminate, resulting in an adhesive sheet having a surface coating, a buffer layer, a substrate, and an adhesive layer in sequence.

[0139] The adhesive sheets obtained from each embodiment and comparative example were evaluated, and the evaluation results are shown in Table 1.

[0140]

[0141] Maleic anhydride-modified polyolefin resin: propylene-butene-maleic anhydride copolymer, maleic anhydride modification rate: 1.5% by mass, average molecular weight (Mw): 75,000, heteroatom content: 0.735% by mass, manufactured by Toyobo Co., Ltd., trade name "TOYO-TAC (registered trademark) PMA-L". • Ethylene-cyclic olefin copolymer: Ethylene-tetracyclododecene copolymer, derived from tetracyclododecene constituent units: 20~32 moles%, heteroatom content: 5.2% by mass, manufactured by Mitsui Chemicals Co., Ltd., 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: Manufactured by Toyobo Co., Ltd., trade name "VYLON (registered trademark) GK-680" • Polyester polyurethane resin: Manufactured by Toyobo Co., Ltd., trade name "VYLON (registered trademark) UR-4410" • Epoxy acrylate resin: Manufactured by Arkema, trade name "CN104 NS"

[0142] As shown in Table 1, the adhesive sheets of Examples 1-3, which use polyolefin resins as surface coatings, can sufficiently reduce the amount of grinding debris adhering. On the other hand, the adhesive sheets of Comparative Examples 1-3, which use resins other than polyolefin resins as surface coatings, do not achieve sufficient reduction in the amount of grinding debris adhering.

Claims

1. An adhesive sheet for semiconductor processing, comprising, in sequence, a surface coating, a buffer layer, a substrate and an adhesive layer, wherein the surface coating is a layer containing a polyolefin resin, the Young's modulus of the substrate is 1,800 to 6,000 MPa, and the thickness of the substrate is 10 to 200 μm.

2. As in claim 1, the adhesive wafer for semiconductor processing, wherein, The aforementioned polyolefin resins contain constituent units derived from chain olefins with 2 to 6 carbon atoms.

3. As in claim 2, the adhesive wafer for semiconductor processing, wherein, The aforementioned polyolefin resins further contain constituent units derived from monomers having oxygen atoms and ethylene-like unsaturated bonds.

4. As in claim 3, the adhesive wafer for semiconductor processing, wherein, The aforementioned single-system maleic anhydride with oxygen atoms and ethylene-like unsaturated bonds.

5. As in claim 2, the adhesive wafer for semiconductor processing, wherein, The aforementioned polyolefin resin further contains constituent units derived from cyclic olefins.

6. The semiconductor processing adhesive film as described in any of claims 1 to 5, wherein, Before 23°C, the polyolefin resins described above have a solubility of more than 1% by mass in toluene.

7. The semiconductor processing adhesive film as described in any of claims 1 to 5, wherein, The thickness of the aforementioned surface coating is 0.05~7μm.

8. The semiconductor processing adhesive film as described in any of claims 1 to 5, wherein, The aforementioned buffer layer is formed from a buffer layer forming composition containing urethane (meth)acrylate.

9. The adhesive sheet for semiconductor processing, as described in any of claims 1 to 5, is used for back-side grinding of semiconductor wafers.

10. A method for manufacturing a semiconductor device, comprising: attaching a semiconductor processing adhesive sheet of any one of claims 1 to 9 to the surface of a semiconductor wafer with the aforementioned adhesive layer as the attachment surface; and grinding the back side of the semiconductor wafer by fixing the aforementioned surface coating side of the aforementioned semiconductor processing adhesive sheet attached to the semiconductor wafer with a support device.

11. A method for manufacturing a semiconductor device as described in claim 10, wherein, The method includes: a step of forming a predetermined dividing line, a step of attaching a thin film, and a step of grinding and monolithization. The aforementioned step of forming the predetermined dividing line is step a of forming a trench on the surface of the semiconductor wafer, or step b of forming a modified region inside the semiconductor wafer from the surface or back side of the semiconductor wafer. The aforementioned step of attaching a thin film is, after step a, or before or after step b, attaching the semiconductor processing adhesive film of any one of claims 1 to 9 to the surface of the semiconductor wafer with the aforementioned adhesive layer as the attachment surface. The aforementioned grinding and monolithization step is, fixing the aforementioned surface coating side of the semiconductor processing adhesive film attached to the semiconductor wafer in a fixed state by means of a support device, grinding the back side of the aforementioned semiconductor wafer, and monolithizing a plurality of semiconductor wafers starting from the aforementioned trench or modified region.