Adhesive sheets for semiconductor wafer processing

Abstract

To provide an adhesive sheet for semiconductor wafer processing that has excellent adhesion to a semiconductor wafer, is easily releasable, and suppresses adhesive residue.SOLUTION: The adhesive sheet for semiconductor wafer processing according to an embodiment of the present invention includes a substrate, an intermediate layer, and an ultraviolet-curable adhesive layer in this order, and in which the storage elastic modulus G'1RT of the intermediate layer at room temperature is 300 kPa to 2000 kPa and the storage elastic modulus G'180 at 80°C is 10 kPa to 500 kPa, and the storage elastic modulus G'2RT of the ultraviolet-curable adhesive layer at room temperature is 100 kPa to 1000 kPa and the storage elastic modulus G'280 at 80°C is 10 kPa to 1000 kPa, and G'1RT / G'2RT is 1 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to an adhesive sheet for semiconductor wafer processing. [Background technology]

[0002] Semiconductor wafers are used in a variety of applications, including personal computers, smartphones, and automobiles. In the semiconductor wafer processing process, adhesive sheets are used to protect the surface during processing. In recent years, the miniaturization and increased functionality of large-scale integrated circuits (LSIs) have led to more complex wafer surface structures. For processing semiconductor wafers with bumps and other uneven structures, adhesive sheets with an intermediate layer between the substrate and the adhesive layer are sometimes used to improve adhesion (embedding of bumps) to the semiconductor wafer. However, adhesive sheets with an intermediate layer can be difficult to cut, and their adhesion to the semiconductor wafer may decrease over time. Furthermore, the intermediate layer may protrude from the adhesive sheet during storage, reducing handling ease.

[0003] In recent years, with the miniaturization and thinning of various products, semiconductor wafers have also been thinned. In the case of thin wafers, if the adhesive strength of the adhesive sheet is too high, the wafer itself may be damaged when the adhesive sheet is peeled off. To prevent adhesive residue on semiconductor wafers and wafer damage during peeling, adhesive sheets using UV-curable adhesives have been proposed (Patent Documents 1 and 2). However, even with adhesive sheets that exhibit excellent adhesion to semiconductor wafers, adhesive residue may still occur even when using UV-curable adhesives. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-49420 [Patent Document 2] Japanese Patent Application Publication No. 153376 / 1983 [Overview of the project]

Problems to be Solved by the Invention

[0005] The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide an adhesive sheet for semiconductor wafer processing that has excellent adhesion to a semiconductor wafer, has easy peelability, and suppresses adhesive residue.

Means for Solving the Problems

[0006] The adhesive sheet for semiconductor wafer processing according to an embodiment of the present invention includes a base material, an intermediate layer, and an ultraviolet curable adhesive layer in this order. The storage elastic modulus G'1 of the intermediate layer at room temperature RT is 300 kPa to 2000 kPa, and the storage elastic modulus G'1 of the intermediate layer at 80°C 80 is 10 kPa to 500 kPa. The storage elastic modulus G'2 of the ultraviolet curable adhesive layer at room temperature RT is 100 kPa to 1000 kPa, and the storage elastic modulus G'2 of the ultraviolet curable adhesive layer at 80°C 80 is 10 kPa to 1000 kPa, and G'1 RT / G'2 RT is 1 or more. In one embodiment, the intermediate layer and the ultraviolet curable adhesive layer contain an acrylic resin. In one embodiment, the ultraviolet curable adhesive layer contains a polymer having a polymerizable carbon-carbon double bond introduced into a side chain. In one embodiment, the intermediate layer contains a photoinitiator and does not contain an ultraviolet curable component. In one embodiment, the acrylic resin contained in the intermediate layer is a polymer obtained by emulsion polymerization or solution polymerization. In one embodiment, the adhesive sheet for semiconductor wafer processing according to an embodiment of the present invention is used as a back grind tape. In one embodiment, the adhesive sheet for semiconductor wafer processing according to an embodiment of the present invention is used by being attached to a semiconductor wafer having irregularities.

Effects of the Invention

[0007] According to an embodiment of the present invention, there is provided an adhesive sheet for semiconductor wafer processing that has excellent adhesion to a semiconductor wafer, is easily peelable, and has suppressed adhesive residue. The adhesive sheet for semiconductor wafer processing according to an embodiment of the present invention has excellent concavo-convex embedding property and can maintain a sufficiently adhered state even when the semiconductor wafer has concavities and convexities on its surface. The adhesive sheet for semiconductor wafer processing according to an embodiment of the present invention has excellent cutting property, so that adhesive residue on the cutter can be suppressed and contamination of the processing apparatus can also be prevented. Further, it is possible to prevent a decrease in handling property due to the intermediate layer protruding from the adhesive sheet during storage.

Brief Description of the Drawings

[0008] [Figure 1] It is a schematic cross-sectional view of an adhesive sheet for semiconductor wafer processing according to one embodiment of the present invention. [Figure 2] It is a schematic cross-sectional view showing a state where an adhesive sheet for semiconductor wafer processing is attached to an adherend having a step.

Embodiments for Carrying Out the Invention

[0009] A. Outline of Adhesive Sheet for Semiconductor Wafer Processing FIG. 1 is a schematic cross-sectional view of an adhesive sheet for semiconductor wafer processing according to one embodiment of the present invention. The adhesive sheet 100 for semiconductor wafer processing in the illustrated example includes a base material 30, an intermediate layer 20, and an ultraviolet curable adhesive layer 10 in this order. The storage elastic modulus G'1 of the intermediate layer 20 at room temperature RT is 300 kPa to 2000 kPa, and the storage elastic modulus G'1 of the intermediate layer 20 at 80°C 80 is 10 kPa to 500 kPa. The initial storage elastic modulus G'2 of the ultraviolet curable adhesive layer 10 RT is 100 kPa to 1000 kPa, and the storage elastic modulus G'2 of the ultraviolet curable adhesive layer 10 at 80°C 80 is 10 kPa to 1000 kPa. The adhesive sheet for semiconductor wafer processing according to an embodiment of the present invention has G'1 RT / G'2 RTThe ratio is 1 or greater. Therefore, it exhibits excellent adhesion to semiconductor wafers and is easily peelable, which can suppress adhesive residue on the semiconductor wafer. Furthermore, the adhesive sheet for semiconductor wafer processing according to the embodiment of the present invention suppresses adhesive residue on the cutter, which can prevent contamination of the processing equipment. In addition, the cutting performance of the adhesive sheet for semiconductor wafer processing can be improved. Furthermore, it can prevent the intermediate layer from protruding during storage, which can reduce handling performance. The adhesive sheet for semiconductor wafer processing according to the embodiment of the present invention exhibits excellent conformability to irregularities even when the semiconductor wafer has irregularities on its surface, and can maintain adhesion to the semiconductor wafer. When peeling off the adhesive sheet according to the embodiment of the present invention, the adhesive layer hardens by irradiation with ultraviolet light, exhibiting easily peelable properties and preventing adhesive residue on the semiconductor wafer. In one embodiment, the adhesive sheet for semiconductor wafer processing according to the embodiment of the present invention is attached to the semiconductor wafer while being heated. Therefore, adhesion to the semiconductor wafer is further improved during attachment, and if the semiconductor wafer has irregularities on its surface, the ability to fill in irregularities can be further improved. Furthermore, under typical conditions in the backgrind tape application process (e.g., table temperature 80°C, cutter temperature 180°C), the intermediate layer has appropriate elasticity, which can suppress adhesive residue on the cutter when cutting the adhesive sheet. In addition, during processing such as the backgrind process and polishing processes that involve high temperature and pressure (e.g., polishing processes using Gettering DP (Disco Corporation) to impart high flexural strength and gettering effect), the tape adheres closely to the semiconductor wafer, is properly held, and stable processing can be performed. In this specification, the storage modulus at room temperature refers to the storage modulus at 23°C.

[0010] Storage modulus G'1 of the intermediate layer 20 at room temperature RT The pressure is between 300kPa and 2000kPa, and the storage modulus of elasticity at 80°C is G'1 80 The pressure range is 10kPa to 500kPa. G'1 RT The pressure is preferably 400kPa to 1500kPa, more preferably 500kPa to 1000kPa, and even more preferably 600kPa to 950kPa. G'1 80The pressure is preferably 20kPa to 300kPa, more preferably 40kPa to 200kPa, and even more preferably 50kPa to 100kPa. G'1 RT and G'1 80 If the above range is maintained, adhesion to the semiconductor wafer may be improved.

[0011] Storage modulus G'2 of UV-curable adhesive layer at room temperature RT The pressure is between 100kPa and 1000kPa, and the storage modulus of elasticity at 80°C is G'2 80 The pressure range is 10kPa to 1000kPa. G'2 RT The pressure is preferably 120kPa to 800kPa, more preferably 130kPa to 600kPa, and even more preferably 150kPa to 400kPa. G'2 80 The pressure is preferably 30kPa to 800kPa, more preferably 50kPa to 500kPa, and even more preferably 70kPa to 300kPa.

[0012] In embodiments of the present invention, G'1 RT / G'2 RT It is 1 or greater. G'1 RT / G'2 RT By having a value of 1 or greater, it is possible to provide an adhesive sheet for semiconductor wafer processing that exhibits excellent adhesion to semiconductor wafers, is easily peelable, and has suppressed adhesive residue. Furthermore, adhesive residue on the cutter when cutting the adhesive sheet can also be suppressed. In addition, during processing such as backgrinding and polishing processes that involve high temperature and pressure, the sheet adheres closely to the semiconductor wafer, is properly held, and stable processing can be performed. G'1 RT / G'2 RT It is preferably 1.2 or higher, more preferably 1.3 or higher, and even more preferably 1.4 or higher. G'1 RT / G'2 RT For example, it is 5.0 or less.

[0013] In one embodiment, the intermediate layer 20 contains a photopolymerization initiator but does not contain an ultraviolet-curable component. Therefore, the intermediate layer does not harden even when irradiated with ultraviolet light and can maintain its flexibility. Furthermore, the photopolymerization initiator contained in the ultraviolet-curable adhesive layer migrates to the intermediate layer, which prevents the amount of photopolymerization initiator in the ultraviolet-curable adhesive layer from decreasing over time. As a result, the ultraviolet-curable adhesive layer hardens appropriately upon ultraviolet irradiation and exhibits easy peelability. Consequently, adhesive residue on semiconductor wafers and damage to thinned wafers can be prevented.

[0014] In one embodiment, the UV-curable adhesive layer and the intermediate layer contain equal amounts of photopolymerization initiator. By having the UV-curable adhesive layer and the intermediate layer contain equal amounts of photopolymerization initiator, the amount of photopolymerization initiator contained in the UV-curable adhesive layer is stably maintained over time, and easy peelability can be achieved. In this specification, "equal amounts" means that the amount (concentration) of photopolymerization initiator in the UV-curable adhesive layer is equal to the amount (concentration) of photopolymerization initiator in the intermediate layer. Specifically, it means that the amount of photopolymerization initiator in the composition forming the adhesive layer is the same as the amount of photopolymerization initiator in the composition forming the intermediate layer.

[0015] The thickness of the adhesive sheet can be set to any suitable range. Preferably, it is 10 μm to 1000 μm, more preferably 50 μm to 300 μm, and even more preferably 100 μm to 300 μm.

[0016] B. Base material The substrate can be composed of any suitable resin. Specific examples of resins constituting the substrate include polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polybutylene naphthalate (PBN); polyolefin resins such as ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, polyethylene, polypropylene, and ethylene-propylene copolymer; polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyamide, polyimide, celluloses, fluororesins, polyethers, polystyrene resins such as polystyrene, polycarbonate, and polyethersulfone. Preferably, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate are used. By using these resins, the occurrence of warping in semiconductor wafers can be further prevented.

[0017] The base material may further contain other components, as long as they do not impair the effects of the present invention. Examples of other components include antioxidants, ultraviolet absorbers, light stabilizers, and heat stabilizers. The type and amount of other components used can be any appropriate amount depending on the purpose.

[0018] In one embodiment, the substrate preferably has an antistatic function. By having an antistatic function in the substrate, the generation of static electricity when the tape is peeled off can be suppressed, preventing circuit damage due to static electricity and the adhesion of foreign matter. The substrate may have an antistatic function by being formed from a resin containing an antistatic agent, or it may have an antistatic function by forming an antistatic layer on any suitable film by coating it with a composition containing an antistatic component such as a conductive polymer, an organic or inorganic conductive substance, and an antistatic agent. When the substrate has an antistatic layer, it is preferable that an intermediate layer is laminated on the surface on which the antistatic layer is formed.

[0019] If the substrate has an antistatic function, the surface resistance value of the substrate is, for example, 1.0 × 10⁻⁶2 Ω / □~1.0×10 13 The ratio is Ω / □, preferably 1.0 × 10⁻⁶. 6 Ω / □~1.0×10 12 Ω / □, and more preferably 1.0 × 10 7 Ω / □~1.0×10 11 The surface resistance is Ω / □. By having a surface resistance within the above range, the generation of static electricity when peeling off the adhesive sheet can be suppressed, preventing circuit damage due to static electricity and the adhesion of foreign matter. When a substrate with antistatic properties is used as the base material, the surface resistance of the resulting adhesive sheet is, for example, 1.0 × 10⁻⁶. 6 Ω / □~1.0×10 12 It could be Ω / □.

[0020] The thickness of the substrate can be set to any appropriate value. The thickness of the substrate is preferably 10 μm to 200 μm, and more preferably 20 μm to 150 μm.

[0021] The tensile modulus of the substrate can be set to any appropriate value. Preferably, the tensile modulus of the substrate is 50 MPa to 6000 MPa, and more preferably 70 MPa to 5000 MPa. By having the tensile modulus within the above range, an adhesive sheet can be obtained that can adequately conform to the unevenness of the semiconductor wafer surface, even if the wafer surface has irregularities.

[0022] C. UV-curing adhesive layer The UV-curing adhesive layer is the above G'2 RT and G'2 80 The adhesive layer can be formed using any suitable composition (adhesive layer forming composition) that satisfies the requirements. The adhesive layer forming composition (the resulting UV-curable adhesive layer) typically contains a UV-curable adhesive and a photopolymerization initiator. By including a UV-curable adhesive, it is possible to provide an adhesive sheet that has excellent adhesion to semiconductor wafers before UV irradiation and excellent peelability after UV irradiation.

[0023] C-1. UV-curing adhesive Any suitable adhesive can be used as the UV-curable adhesive. For example, it may be an adhesive to which UV-curable monomers and / or oligomers have been added to any suitable adhesive such as an acrylic adhesive, rubber adhesive, silicone adhesive, or polyvinyl ether adhesive, or it may be an adhesive using a polymer in which polymerizable carbon-carbon double bonds have been introduced into the side chains and / or terminals as the base polymer. Preferably, an adhesive using a polymer in which polymerizable carbon-carbon double bonds have been introduced into the side chains and / or terminals as the base polymer is used, and more preferably, an adhesive using a polymer in which polymerizable carbon-carbon double bonds have been introduced into the side chains is used.

[0024] When using an adhesive that utilizes a polymer in which polymerizable carbon-carbon double bonds are introduced into the side chains and / or terminals, the base polymer used is a polymer in which polymerizable carbon-carbon double bonds are introduced into the side chains and / or terminals and which is also adhesive. Examples of such polymers include polymers in which polymerizable carbon-carbon double bonds are introduced into resins such as acrylic resins, vinyl alkyl ether resins, silicone resins, polyester resins, polyamide resins, urethane resins, and styrene-diene block copolymers. Preferably, an acrylic resin in which polymerizable carbon-carbon double bonds are introduced into an acrylic resin is used. By using an acrylic resin, it is easy to adjust the storage modulus and tensile modulus of the UV-curable adhesive layer, and an adhesive sheet with an excellent balance between adhesive strength and release properties can be obtained. Furthermore, contamination of semiconductor wafers by components derived from the adhesive can be reduced.

[0025] Any suitable acrylic resin can be used as the acrylic resin. Examples of acrylic resins include polymers obtained by polymerizing a monomer composition containing one or more esters of acrylic acid or methacrylic acid having linear or branched alkyl groups.

[0026] The linear or branched alkyl groups are preferably alkyl groups having 30 or fewer carbon atoms, more preferably alkyl groups having 1 to 20 carbon atoms, and even more preferably alkyl groups having 4 to 18 carbon atoms. Specific examples of alkyl groups include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, t-butyl group, isobutyl group, amyl group, isoamyl group, hexyl group, heptyl group, cyclohexyl group, 2-ethylhexyl group, octyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, lauryl group, tridecyl group, tetradecyl group, stearyl group, octadecyl group, dodecyl group, and the like.

[0027] The monomer composition may contain any other suitable monomers. Other monomers include, for example, carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; (meth)acrylate 2-hydroxyethyl, (meth)acrylate 2-hydroxypropyl, (meth)acrylate 4-hydroxybutyl, (meth)acrylate 6-hydroxyhexyl, (meth)acrylate 8-hydroxyoctyl, (meth)acrylate 10-hydroxydecyl, (meth)acrylate 12-hydroxylauryl, (4-hydroxy Examples of functional group-containing monomers include hydroxyl group-containing monomers such as hydroxymethylcyclohexyl)-methyl acrylate, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether; sulfonic acid group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; and phosphate group-containing monomers such as 2-hydroxyethyl acryloyl phosphate. By including functional group-containing monomers, it is possible to obtain acrylic resins in which polymerizable carbon-carbon double bonds are easily introduced. The content ratio of the functional group-containing monomer is preferably 4 to 30 parts by weight, more preferably 6 to 20 parts by weight, per 100 parts by weight of the total monomer components of the monomer composition. Note that "(meth)acrylic" refers to acrylic and / or methacrylic.

[0028] Other monomers may be used, such as polyfunctional monomers. By using polyfunctional monomers, the cohesive force, heat resistance, and adhesiveness of the adhesive can be improved. In addition, since the amount of low molecular weight components in the UV-curable adhesive layer is reduced, an adhesive sheet that is less likely to contaminate semiconductor wafers can be obtained. Examples of polyfunctional monomers include hexanediol (meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, and urethane (meth)acrylate. The content ratio of the polyfunctional monomer is preferably 1 to 100 parts by weight, more preferably 5 to 50 parts by weight, per 100 parts by weight of the total monomer components of the monomer composition.

[0029] The weight-average molecular weight of the acrylic resin is preferably 300,000 or more, more preferably 500,000 or more, and even more preferably 800,000 to 3,000,000. Within this range, bleeding of low molecular weight components can be prevented, and a low-contamination adhesive sheet for semiconductor wafer processing can be obtained. The molecular weight distribution (weight-average molecular weight / number-average molecular weight) of the (meth)acrylic resin is preferably 1 to 20, and more preferably 3 to 10. By using a (meth)acrylic resin with a narrow molecular weight distribution, bleeding of low molecular weight components can be prevented, and a low-contamination adhesive sheet can be obtained. The weight-average molecular weight and number-average molecular weight can be determined by gel permeation chromatography (solvent: tetrahydrofuran, polystyrene equivalent).

[0030] Polymers in which polymerizable carbon-carbon double bonds are introduced in the side chains and / or terminals can be obtained by any suitable method. For example, they can be obtained by reacting (e.g., condensation reaction, addition reaction) a resin obtained by any suitable polymerization method with a compound having polymerizable carbon-carbon double bonds. Specifically, when using an acrylic resin, an acrylic resin (polymer) having constituent units derived from monomers having any suitable functional groups can be polymerized in any suitable solvent, and then the functional groups of the acrylic resin can be reacted with a compound having polymerizable carbon-carbon double bonds that can react with the functional groups to obtain an acrylic resin into which polymerizable carbon-carbon double bonds have been introduced. The amount of the compound having polymerizable carbon-carbon double bonds to be reacted is preferably 4 to 30 parts by weight, more preferably 4 to 20 parts by weight, per 100 parts by weight of the resin. Any suitable solvent can be used as the solvent, for example, various organic solvents such as ethyl acetate, methyl tyl ketone, and toluene.

[0031] When a resin and a compound having a polymerizable carbon-carbon double bond are reacted as described above, it is preferable that both the resin and the compound having a polymerizable carbon-carbon double bond have functional groups that can react with each other. Examples of functional group combinations include carboxyl group / epoxy group, carboxyl group / aziridine group, and hydroxyl group / isocyanate group. Among these functional group combinations, the combination of a hydroxyl group and an isocyanate group is preferred due to the ease of reaction tracking.

[0032] Examples of compounds having polymerizable carbon-carbon double bonds include 2-isocyanate ethyl methacrylate, methacryloisocyanate, 2-methacryloyloxyethyl isocyanate (2-isocyanate ethyl methacrylate), and m-isopropenyl-α,α-dimethylbenzyl isocyanate.

[0033] When using an adhesive containing UV-curable monomers and / or oligomers, any suitable monomer or oligomer can be used as the UV-curable monomer and / or oligomer. Examples of UV-curable monomers include urethane (meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and 1,4-butanediol di(meth)acrylate. Examples of UV-curable oligomers include urethane-based oligomers, polyether-based oligomers, polyester-based oligomers, polycarbonate-based oligomers, and polybutadiene-based oligomers. Preferably, oligomers with a molecular weight of about 100 to 30000 are used. Monomers and oligomers may be used individually or in combination of two or more.

[0034] Monomers and / or oligomers may be used in any appropriate amount depending on the type of adhesive used. For example, 5 to 500 parts by weight, more preferably 40 to 150 parts by weight, are used per 100 parts by weight of the base polymer constituting the adhesive.

[0035] C-2. Photopolymerization Initiator Any suitable initiator can be used as the photopolymerization initiator. Examples of photopolymerization initiators include acylphosphine oxide photoinitiators such as ethyl 2,4,6-trimethylbenzylphenylphosphine and (2,4,6-trimethylbenzoyl)-phenylphosphine oxide; α-ketol compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and 1-hydroxycyclohexylphenylketone; and methoxyacetophenone. Acetophenone compounds such as 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether; ketal compounds such as benzyldimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; 1-phenone-1,1-propanedione-2-( Photoactive oxime compounds such as o-ethoxycarbonyl oxime; benzophenone compounds such as benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone; camphorquinone; halogenated ketones Examples include acylphosphonates and α-hydroxyacetophenones such as 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl-2-methylpropane-1. Preferably, 2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl-2-methylpropane-1 can be used. One photopolymerization initiator may be used alone, or two or more may be used in combination.

[0036] Commercially available photopolymerization initiators may be used. Examples include Omnirad 127 and Omnirad 651 from IGM Resins.

[0037] The photopolymerization initiator is used in any appropriate amount. The amount of photopolymerization initiator is preferably 0.5 to 20 parts by weight, and more preferably 0.5 to 10 parts by weight, per 100 parts by weight of the UV-curable adhesive. If the amount of photopolymerization initiator is less than 0.5 parts by weight, the adhesive may not cure sufficiently when irradiated with UV light. If the amount of photopolymerization initiator exceeds 10 parts by weight, the storage stability of the adhesive may decrease.

[0038] C-3. Additives The above adhesive layer-forming composition may optionally contain any suitable additives. Examples of such additives include crosslinking agents, catalysts (e.g., platinum catalysts), tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, conductive materials, ultraviolet absorbers, light stabilizers, release modifiers, softeners, surfactants, flame retardants, and solvents.

[0039] In one embodiment, the adhesive layer-forming composition further comprises a crosslinking agent. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and chelate-based crosslinking agents. The content ratio of the crosslinking agent is preferably 0.01 to 10 parts by weight, more preferably 0.02 to 5 parts by weight, and even more preferably 0.025 to 0.5 parts by weight, per 100 parts by weight of the base polymer contained in the UV-curable adhesive. The flexibility of the adhesive layer can be controlled by the content ratio of the crosslinking agent. If the crosslinking agent content is less than 0.01 parts by weight, the adhesive may become sol-like and may not be able to form an adhesive layer. If the crosslinking agent content exceeds 10 parts by weight, the adhesion to the semiconductor wafer may decrease and the semiconductor wafer may not be adequately protected.

[0040] In one embodiment, an isocyanate-based crosslinking agent is preferably used. Isocyanate-based crosslinking agents are preferred because they can react with a variety of functional groups. Particularly preferred is a crosslinking agent having three or more isocyanate groups. By using an isocyanate-based crosslinking agent and setting the content of the crosslinking agent within the above range, it is possible to form an adhesive layer that exhibits excellent peelability and significantly reduces adhesive residue even after heating.

[0041] The thickness of the UV-curable adhesive layer can be set to any appropriate value. Preferably, the thickness of the adhesive layer is 1 μm to 15 μm, more preferably 1 μm to 10 μm, and even more preferably 1 μm to 6 μm. By having the adhesive layer thickness within this range, sufficient adhesion to the semiconductor wafer can be achieved.

[0042] The elastic modulus (Young's modulus) of the adhesive layer before UV irradiation is preferably 0.05 MPa to 2.0 MPa, more preferably 0.075 MPa to 1.5 MPa, even more preferably 0.3 MPa to 1.5 MPa, and particularly preferably 0.4 MPa or more and less than 1.5 MPa. Within this range, an adhesive sheet with sufficient adhesive strength to hold a semiconductor wafer can be obtained. In this specification, the elastic modulus of the adhesive layer refers to the elastic modulus (Young's modulus) measured by the following method. The adhesive layer-forming composition is applied to a separator to a thickness of 5 μm and dried at 130°C for 2 minutes. Next, only the adhesive layer after drying is rolled up from one end to create a rod-shaped sample, and its thickness (cross-sectional area) is measured. The obtained sample is then pulled using a tensile testing machine (manufactured by SHIMADZU, product name "AG-IS") under the conditions of a chuck distance of 10 mm, a tensile speed of 50 mm / min, and room temperature. The initial slope (Young's modulus) is defined as the modulus of elasticity.

[0043] The elastic modulus of the adhesive layer after UV irradiation is preferably 1 MPa or more, more preferably 5 MPa or more, and even more preferably 10 MPa or more. Within this range, an adhesive sheet with excellent peelability after a predetermined process (e.g., a backgrinding process) can be obtained. The elastic modulus of the adhesive layer after UV irradiation is, for example, 1000 MPa or less, preferably 500 MPa or less, and more preferably 400 MPa or less.

[0044] The adhesive layer may be one layer or two or more layers. If there are two or more adhesive layers, at least one adhesive layer formed using the adhesive layer forming composition containing the photopolymerization initiator is sufficient. If there are two or more adhesive layers, preferably an adhesive layer formed using the adhesive layer forming composition containing the photopolymerization initiator is formed on the surface of the adhesive sheet that contacts the semiconductor wafer. The adhesive layer not formed by the adhesive layer forming composition can be formed with any suitable adhesive composition. This adhesive composition may be an ultraviolet-curable adhesive or a pressure-sensitive adhesive.

[0045] D. middle class The middle layer is G'1 RT and G'1 80It is sufficient that the requirements are met, and it can be formed from any suitable material. The intermediate layer can be formed from a resin such as an acrylic resin, polyethylene resin, ethylene-vinyl alcohol copolymer, ethylene vinyl acetate resin, and ethylene methyl methacrylate resin, or from an adhesive. Preferably, the intermediate layer contains an acrylic resin. In one embodiment, the UV-curable adhesive layer and the intermediate layer contain an acrylic resin. By including an acrylic resin in the UV-curable adhesive layer and the intermediate layer, an adhesive sheet for semiconductor wafer processing can be obtained that has excellent adhesion to semiconductor wafers, is easily peelable, and has suppressed adhesive residue. Furthermore, since acrylic resins also have excellent transparency and heat resistance, the adhesive layer can be irradiated with sufficient ultraviolet light in the subsequent UV irradiation process, and processing can be performed stably even in processes that require heat resistance, such as polishing. In addition, if the semiconductor wafer has irregularities on its surface, an adhesive sheet for semiconductor wafer processing with excellent conformability to irregularities can be obtained.

[0046] The acrylic resin used in the intermediate layer is obtained by polymerizing a monomer composition containing any suitable acrylic monomer. Examples of acrylic monomers (main monomers) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate C1-C (meth)acrylic acids such as acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. 20 Alkyl esters are examples. Only one acrylic monomer may be used, or two or more may be used in combination.

[0047] The content of the main monomer is preferably 40% to 99% by weight of the total monomer components, more preferably 45% to 95% by weight, and even more preferably 50% to 90% by weight.

[0048] In embodiments of the present invention, the monomer composition preferably comprises an acrylic monomer with a high glass transition temperature (Tg) (high-Tg acrylic monomer). By including an acrylic monomer with a high glass transition temperature in the intermediate layer, it is possible to provide an adhesive sheet for semiconductor wafer processing that has excellent adhesion to semiconductor wafers, is easily peelable, and has suppressed adhesive residue. Furthermore, the adhesive sheet for semiconductor wafer processing also has excellent cutability, adhesive residue on the cutter is suppressed, and contamination of processing equipment can be prevented. In addition, it is possible to prevent a decrease in handling performance due to the intermediate layer protruding from the adhesive sheet during storage. In this specification, a high-Tg acrylic monomer refers to a monomer in which the homopolymer has a high glass transition temperature. The glass transition temperature of the homopolymer of the high-Tg acrylic monomer is, for example, 40°C or higher, preferably 50°C or higher, and more preferably 60°C or higher.

[0049] Any suitable acrylic monomer can be used as the high Tg acrylic monomer. For example, (meth)acrylic acid esters such as dicyclopentanyl methacrylate (Tg: 175°C), dicyclopentanyl acrylate (Tg: 120°C), isobornyl methacrylate (Tg: 173°C), isobornyl acrylate (Tg: 97°C), methyl methacrylate (Tg: 105°C), 1-adamantyl methacrylate (Tg: 250°C), 1-adamantyl acrylate (Tg: 153°C); acryloylmorpholine (Tg: 145°C), dimethylacrylamide (Tg: 119°C), di Examples include amide group-containing vinyl monomers such as ethyl acrylamide (Tg: 81°C), dimethylaminopropyl acrylamide (Tg: 134°C), isopropyl acrylamide (Tg: 134°C), and hydroxyethyl acrylamide (Tg: 98°C); acid monomers such as methacrylic acid (Tg: 228°C) and acrylic acid (Tg: 106°C); methacrylic acid esters such as methyl methacrylate (Tg: 105°C) and t-butyl methacrylate (Tg: 107°C); and N-vinylpyrrolidone (Tg: 54°C). High-Tg acrylic monomers may be used individually or in combination of two or more.

[0050] The content of high-Tg acrylic monomers can be set, for example, so that the glass transition temperature of the acrylic resin, determined by Fox's formula based on the monomer composition, is -30°C or higher. Fox's formula is a relationship between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below. 1 / Tg = Σ(Wi / Tgi) In the Fox equation above, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (weight-based copolymerization ratio), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K).

[0051] The glass transition temperature of the homopolymer used to calculate Tg can be a known value. Specifically, the glass transition temperature is described in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). In this specification, for monomers for which multiple values ​​are listed in the Polymer Handbook, the highest value will be used as the glass transition temperature of the monomer. For homopolymers of monomers not listed in the Polymer Handbook, the value obtained by the measurement method described in Japanese Patent Application Publication No. 2007-51271 can be used.

[0052] The content of high-Tg acrylic monomers is preferably 1% to 50% by weight of the total monomer components, and more preferably 3% to 40% by weight. By having a high-Tg acrylic monomer content within the above range, an adhesive sheet for semiconductor wafer processing is provided that has excellent adhesion to semiconductor wafers, is easily peelable, and has suppressed adhesive residue. The adhesive sheet for semiconductor wafer processing according to the embodiment of the present invention also has excellent cutability, so adhesive residue on the cutter is suppressed and contamination of processing equipment can be prevented. Furthermore, it can prevent a decrease in handling performance due to the intermediate layer protruding from the adhesive sheet during storage.

[0053] The monomer composition may contain, in addition to the main monomer and the high-Tg acrylic monomer, any suitable monomer (copolymer monomer) that can copolymerize with the main monomer. Examples of copolymer monomers used are those exemplified as other monomers in section C-1 above. Preferably, monomers having polar groups such as hydroxyl groups and carboxyl groups can be used as copolymer monomers, and more preferably monomers having hydroxyl groups. Using monomers with polar groups can improve cohesiveness, heat resistance, crosslinkability, etc. Only one copolymer monomer may be used, or two or more may be used in combination.

[0054] The copolymer monomer content is preferably 0.01% to 30% by weight of the total monomer components, more preferably 0.1% to 20% by weight, and even more preferably 1% to 10% by weight. By having the copolymer monomer content within the above range, cohesive strength, heat resistance, crosslinkability, etc., can be improved.

[0055] The acrylic resin used in the intermediate layer is obtained by polymerizing a monomer composition containing the above-mentioned monomer components. Any suitable polymerization method can be used. Examples include emulsion polymerization, solution polymerization, bulk polymerization, and suspension polymerization. Preferably, the acrylic resin is a polymer obtained by emulsion polymerization or solution polymerization. By using these polymerization methods, various additives can be used, and various types of acrylic resins can be prepared.

[0056] Any suitable emulsifier can be used in emulsion polymerization. Examples include anionic emulsifiers such as alkyl sulfates, alkylbenzene sulfons, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, and polyoxyethylene alkyl phosphates, and nonionic emulsifiers such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene-polyoxypropylene block polymers, sorbitan fatty acid esters, and polyoxyethylene fatty acid esters. The water content can be adjusted to any suitable amount; for example, the solid content concentration of the acrylic polymer after emulsion polymerization can be adjusted to 30% to 75% by weight, preferably 35% to 70% by weight. Any suitable initiator can be used as the polymerization initiator; for example, azo initiators and peroxide initiators are used. A chain transfer agent may be used to adjust the molecular weight.

[0057] Ethyl acetate, toluene, etc., are used as solvents for solution polymerization. The solution concentration is, for example, about 20% to 80% by weight. Any suitable initiator can be used as the polymerization initiator; for example, azo initiators and peroxide initiators are used. Chain transfer agents may be used to adjust the molecular weight. The reaction temperature is usually 50°C to 80°C, and the reaction time is usually 1 to 8 hours.

[0058] The weight-average molecular weight of the acrylic resin is preferably 200,000 to 15,000,000, and more preferably 300,000 to 10,000,000. The weight-average molecular weight can be measured by GPC (solvent: THF).

[0059] The glass transition temperature of the acrylic resin is preferably -50°C to 30°C, and more preferably -40°C to 20°C. Within this range, an adhesive sheet with excellent heat resistance that can be suitably used in heating processes can be obtained.

[0060] In embodiments of the present invention, the intermediate layer preferably contains a photopolymerization initiator but does not contain an ultraviolet-curable component. That is, although the intermediate layer contains a photopolymerization initiator, the intermediate layer itself does not harden upon ultraviolet irradiation. Therefore, the intermediate layer can maintain its flexibility before and after ultraviolet irradiation. Furthermore, by containing a photopolymerization initiator in the intermediate layer, the photopolymerization initiator contained in the ultraviolet-curable adhesive layer migrates to the intermediate layer, and as a result, the decrease in the content of the photopolymerization initiator contained in the adhesive layer over time can be suppressed. Therefore, the adhesive sheet can exhibit excellent easy peelability after ultraviolet irradiation. In this specification, an ultraviolet-curable component refers to a component that can crosslink and harden and shrink upon ultraviolet irradiation. Specifically, examples include ultraviolet-curable monomers and oligomers exemplified in Section C above, and polymers in which polymerizable carbon-carbon double bonds are introduced in the side chains and / or terminals.

[0061] The photopolymerization initiator may be the same as or different from the photopolymerization initiator contained in the UV-curable adhesive layer. Preferably, the intermediate layer contains the same photopolymerization initiator as the adhesive layer. By having the intermediate layer and the adhesive layer contain the same photopolymerization initiator, the migration of the photopolymerization initiator from the adhesive layer to the intermediate layer can be further suppressed. As the photopolymerization initiator, the photopolymerization initiators exemplified in section C above can be used. Only one type of photopolymerization initiator may be used, or two or more types may be used in combination.

[0062] The amount of photopolymerization initiator in the intermediate layer is preferably 0.1 to 10 parts by weight, and more preferably 0.5 to 8 parts by weight, per 100 parts by weight of acrylic resin in the composition forming the intermediate layer (hereinafter also referred to as the intermediate layer forming composition). By having the photopolymerization initiator content in the intermediate layer within the above range, an adhesive sheet with excellent easy peelability after ultraviolet irradiation can be obtained. In one embodiment, the amount of photopolymerization initiator used is equal to the amount of photopolymerization initiator contained in the composition forming the ultraviolet curable adhesive layer.

[0063] In one embodiment, the intermediate layer forming composition further comprises a crosslinking agent. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, amine-based crosslinking agents, and the like.

[0064] If the intermediate layer forming composition contains a crosslinking agent, the content ratio of the crosslinking agent is preferably 0.5 to 10 parts by weight, and more preferably 1 to 8 parts by weight, per 100 parts by weight of the acrylic resin in the intermediate layer forming composition.

[0065] The intermediate layer forming composition may further contain any suitable additives as needed. Examples of additives include active energy ray polymerization accelerators, radical scavengers, tackifiers, plasticizers (e.g., trimellitic acid ester plasticizers, pyromellitic acid ester plasticizers, etc.), pigments, dyes, fillers, antioxidants, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, release modifiers, softeners, surfactants, flame retardants, antioxidants, and the like.

[0066] The thickness of the intermediate layer can be set to any appropriate thickness. For example, if the semiconductor wafer has irregularities on its surface, it is preferable to make the thickness of the intermediate layer greater than the height of the protrusions. The thickness of the intermediate layer is preferably 10 μm to 300 μm, more preferably 20 μm to 200 μm, even more preferably 30 μm to 150 μm, and particularly preferably 50 μm to 150 μm. By having the intermediate layer thickness within the above range, when the semiconductor wafer has irregularities on its surface, an adhesive sheet with excellent irregularity-filling properties can be obtained.

[0067] The elastic modulus (Young's modulus) of the intermediate layer before UV irradiation is preferably 0.01 MPa to 10.0 MPa, more preferably 0.01 MPa to 5.0 MPa, and even more preferably 0.01 MPa to 3.0 MPa. Within this range, if the semiconductor wafer has surface irregularities, an adhesive sheet with excellent ability to fill in irregularities can be obtained. Furthermore, the semiconductor wafer retention force of the adhesive sheet can be improved. The elastic modulus of the intermediate layer can be measured by the following method. The intermediate layer-forming composition was applied to a separator to a thickness of 5 μm and dried at 130°C for 2 minutes. Next, only the adhesive layer after coating and drying was rolled from one end to create a rod-shaped sample, and its thickness (cross-sectional area) was measured. The obtained sample was then pulled using a tensile testing machine (manufactured by SHIMADZU, product name "AG-IS") under the conditions of a chuck distance of 10 mm, a tensile speed of 50 mm / min, and room temperature. The initial slope (Young's modulus) was defined as the modulus of elasticity.

[0068] E. Method for manufacturing adhesive sheets for semiconductor wafer processing The adhesive sheet for semiconductor wafer processing according to embodiments of the present invention can be manufactured by any suitable method. The adhesive sheet can be manufactured, for example, by forming an intermediate layer on a substrate and then forming an adhesive layer on the intermediate layer. The adhesive layer and the intermediate layer may be formed by coating the substrate or intermediate layer with the composition for forming the adhesive layer and the composition for forming the intermediate layer, respectively, or by forming each layer on any suitable separator and then transferring it. Various coating methods can be employed, such as bar coater coating, air knife coating, gravure coating, gravure reverse coating, reverse roll coating, lip coating, die coating, dip coating, offset printing, flexographic printing, and screen printing. Alternatively, a method may be employed in which an adhesive layer is formed on a separator and then bonded to the laminate of the substrate and intermediate layer.

[0069] F. Applications of adhesive sheets for semiconductor wafer processing The adhesive sheet for semiconductor wafer processing according to the embodiment of the present invention is suitably used in semiconductor wafer processing processes. The adhesive sheet for semiconductor wafer processing has excellent adhesive strength to semiconductor wafers before ultraviolet irradiation and excellent peelability after ultraviolet irradiation. Therefore, even when processing thin wafers, peeling can be done with less force without damaging the wafer. Furthermore, because the adhesive sheet has an intermediate layer, it can follow the surface irregularities well even if the semiconductor wafer has irregularities. Therefore, it can hold the semiconductor wafer during processing and peel off from the semiconductor wafer after processing without any problems such as adhesive residue. Moreover, the adhesive sheet for semiconductor wafer processing according to the embodiment of the present invention also has excellent cutability, so adhesive residue on the cutter is suppressed and contamination of processing equipment can also be prevented.

[0070] The semiconductor wafer processing adhesive sheet according to the embodiment of the present invention is attached to a semiconductor wafer at any suitable attachment temperature. For example, it is attached to a semiconductor wafer at a temperature of room temperature (e.g., 23°C) to 100°C. The semiconductor wafer processing adhesive sheet according to the embodiment of the present invention is G'1 RT The pressure ranges from 300 kPa to 2000 kPa, and G'1 80 The range is 10kPa to 500kPa, G'2 RT The pressure is between 100kPa and 1000kPa, and G'2 80 The pressure ranges from 10 kPa to 1000 kPa, and G'1 RT / G'2 RT The value is 1 or greater. Therefore, it can adhere sufficiently to the semiconductor wafer during application, and can exhibit excellent retention force to the semiconductor wafer after application.

[0071] In one embodiment, the adhesive sheet for semiconductor wafer processing according to the embodiment of the present invention is attached to a semiconductor wafer while being heated. Therefore, when attached, the intermediate layer becomes low elasticity, and if the semiconductor wafer has irregularities on its surface, the ability to follow the irregularities is further improved, and the ability to fill the irregularities can be further improved. On the other hand, at room temperature (for example, 23°C), the intermediate layer becomes high elasticity, so it can maintain a state of close contact with the irregularities. Furthermore, adhesive residue on the cutter when cutting the adhesive sheet can be suppressed. In addition, during processing such as the backgrinding process, the semiconductor wafer can be properly held and wafer warping can be prevented.

[0072] In one embodiment, the adhesive sheet for semiconductor wafer processing according to the embodiment of the present invention is used by being attached to a semiconductor wafer having an uneven surface. As described above, the adhesive sheet for semiconductor wafer processing according to the embodiment of the present invention can be sufficiently adhered to the semiconductor wafer when attached, and exhibits excellent embedding properties into the unevenness even when the semiconductor wafer surface has an uneven surface. Furthermore, after attachment, the adhesive sheet can maintain an adherent state without lifting from the unevenness. Therefore, the semiconductor wafer can be sufficiently supported in each process.

[0073] In one embodiment, the adhesive sheet for semiconductor wafer processing according to an embodiment of the present invention can be suitably used as a backgrind tape. The adhesive sheet adheres well to the semiconductor wafer before ultraviolet irradiation and exhibits excellent easy peeling after ultraviolet irradiation. Therefore, even when the structure of the semiconductor wafer surface is complex, adhesive residue on the semiconductor wafer surface can be prevented. As a result, the semiconductor wafer can be properly held during the backgrinding process, and after the backgrinding process is completed, it can be easily peeled off from the semiconductor wafer, and adhesive residue on the semiconductor wafer can also be prevented. [Examples]

[0074] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The test and evaluation methods in the examples are as follows. Unless otherwise specified, "parts" and "%" are based on weight.

[0075] [Example 1] An intermediate layer-forming composition (solids content: 23% by weight) was prepared, comprising 100 parts by weight of acrylic resin 1 (a polymer with a mass of 330,000 obtained by emulsion polymerization of 58.4 mol of butyl acrylate (BA), 38.6 mol of methyl methacrylate (MMA), and 3 mol of 2-hydroxyethyl acrylate (HEA)), 0.1 parts by weight of a crosslinking agent (polyisocyanate compound, trade name "Coronate L", manufactured by Tosoh Corporation), 1 part by weight of a photopolymerization initiator (manufactured by IGM Resins, trade name: Omnirad 127D), 0.1 parts by weight of a polymerization inhibitor (manufactured by BASF, trade name: Irganox 1010), and ethyl acetate. Next, the obtained intermediate layer-forming composition was applied to the silicone-treated surface of a 38 μm thick polyester separator (manufactured by Mitsubishi Plastics, Inc., trade name: MRF), and then heated at 120°C for 120 seconds to remove the solvent and form an intermediate layer with a thickness of 150 μm. Next, an intermediate layer formed on a separator was laminated to the antistatic treated (ESAS) surface of a 50 μm thick antistatic PET film. A composition for forming an adhesive layer (solid content: 15% by weight) was prepared, comprising 100 parts by weight of acrylic resin 2 (an acrylic resin obtained by solution polymerization of 75 mol of BA, 25 mol of MMA, and 20 mol of HEA, to which 18 mol of 2-isocyanate ethyl methacrylate (manufactured by Showa Denko, trade name "Karens MOI") was added), 1 part by weight of a crosslinking agent (polyisocyanate compound, trade name "Coronate L", manufactured by Tosoh Corporation), 1 part by weight of a photopolymerization initiator (manufactured by IGM Resins, trade name: Omnirad 127D), 0.1 parts by weight of a polymerization inhibitor (manufactured by BASF, trade name: Irganox 1010), and ethyl acetate. Next, the obtained adhesive layer forming composition was applied to the silicone-treated surface of a 75 μm thick polyester separator, and then heated at 120°C for 120 seconds to remove the solvent and form an adhesive layer with a thickness of 6 μm. Next, the separator was peeled off the laminate of the antistatic PET film and the intermediate layer, and the adhesive layer was transferred to the surface of the intermediate layer from which the separator had been peeled off. The sheet was then stored at 50°C for 72 hours to obtain an adhesive sheet (substrate (50 μm) / intermediate layer (150 μm) / UV-curable adhesive layer (6 μm)). The compositions of the intermediate layer forming composition and the adhesive layer forming composition are shown in Table 1.

[0076] [Table 1]

[0077] [Example 2] An adhesive sheet was obtained in the same manner as in Example 1, except that the thickness of the intermediate layer was changed to 100 μm.

[0078] [Example 3] An adhesive sheet was obtained in the same manner as in Example 1, except that 4 parts by weight of a crosslinking agent was used in the adhesive layer forming composition, and the thickness of the UV-curable adhesive layer was 10 μm.

[0079] [Example 4] An adhesive sheet was obtained in the same manner as in Example 3, except that the thickness of the intermediate layer was changed to 100 μm.

[0080] [Example 5] An adhesive sheet was obtained in the same manner as in Example 1, except that 100 parts by weight of acrylic resin 3 (an acrylic resin obtained by solution polymerization of 75 mol of ethyl acrylate (EA), 25 mol of acryloyl morpholine (ACMO), and 22 mol of HEA, to which 18 mol of 2-isocyanate ethyl methacrylate (manufactured by Showa Denko, trade name "Karens MOI") was added) was used instead of acrylic resin 2 in the adhesive layer forming composition, and 5 parts by weight of a crosslinking agent was used.

[0081] [Example 6] An adhesive sheet was obtained in the same manner as in Example 5, except that acrylic resin 4 (a polymer obtained by solution polymerization of 58.4 mol of BA, 38.6 mol of MMA, and 3 mol of HEA in ethyl acetate) was used instead of acrylic resin 1 in the intermediate layer forming composition.

[0082] (Comparative Example 1) An adhesive sheet was obtained in the same manner as in Example 6, except that 100 parts by weight of acrylic resin 5 (a polymer obtained by solution polymerization of 75 mol of BA, 25 mol of MMA, and 5 mol of HEA in ethyl acetate) was used instead of acrylic resin 1 in the intermediate layer forming composition.

[0083] (Comparative Example 2) An adhesive sheet was obtained in the same manner as in Comparative Example 1, except that 100 parts by weight of acrylic resin 6 (a resin obtained by polymerizing 100 mol of 2-ethylhexyl acrylate (2HEA), 20 mol of HEA, and 16 mol of 2-isocyanate ethyl methacrylate (manufactured by Showa Denko, trade name "Karens MOI")) was used instead of acrylic resin 2 in the adhesive layer forming composition, and 1 part by weight of a crosslinking agent was used.

[0084] (Comparative Example 3) An adhesive sheet was obtained in the same manner as in Comparative Example 1, except that in the intermediate layer forming composition, 100 parts by weight of acrylic resin 7 (a polymer obtained by solution polymerization of 50 mol of BA, 50 mol of EA, and 3 mol of acrylic acid (AA) in toluene) was used instead of acrylic resin 1, the content of the crosslinking agent was changed to 1 part by weight and the content of the photopolymerization initiator to 3 parts by weight, and in the adhesive layer forming composition, the content of the crosslinking agent was changed to 1.5 parts by weight.

[0085] (Comparative Example 4) An adhesive sheet was obtained in the same manner as in Comparative Example 1, except that acrylic resin 7 was used instead of acrylic resin 5 in the intermediate layer forming composition, and 100 parts by weight of acrylic resin 8 (an acrylic resin obtained by adding 11 mol of 2-isocyanate ethyl methacrylate (manufactured by Showa Denko, trade name "Karens MOI") to a polymer obtained by solution polymerization of 75 mol of ethyl acrylate (EA), 25 mol of acryloyl morpholine (ACMO), and 22 mol of HEA in toluene) was used instead of acrylic resin 2 in the adhesive layer forming composition.

[0086] The following evaluations were performed using the adhesive sheets obtained in the examples and comparative examples. The results are shown in Table 2. (1) Initial implantability The adhesive sheets (230 cm x 400 cm) obtained in the examples and comparative examples were attached to wafers (8 inch, bump height 75 μm, diameter 90 μm, pitch 200 μm) using a tape application device (manufactured by Nitto Seiki Co., Ltd., product name: DR-3000III). The attachment was carried out under the following conditions. Roller pressure: 0.40 MPa Roller speed: 5 mm / second Table temperature: 80℃ After attachment, the adhesion state of the adhesive sheet and wafer was observed using a laser microscope (magnification: 100x). Additionally, images were taken of the adhesive sheet and wafer with the adhesive sheet facing upwards, and the images were binarized (8-bit grayscale, brightness: 0-255, threshold: 114) using image analysis software (Image J (free software)). Five bumps were arbitrarily selected, and the number of dots used to display each bump was measured. The image of only the bumps without tape had 220 dots; with tape, a dot count closer to 220 indicates better embedding. Bumps with an average dot count of 830 or less were evaluated as ○, and those with an average dot count exceeding 830 were evaluated as ×.

[0087] (2) Time-dependent embedding The adhesive sheet and wafer stack, which had undergone initial embedding performance evaluation, was left at room temperature for one week. Subsequently, the adhesive sheet and wafer were imaged in the same manner as in the initial embedding performance evaluation, and the images were binarized. The obtained average number of dots was compared with the average number of dots in the initial embedding performance evaluation, and the change in the average number of dots (|(average number of dots in initial embedding performance evaluation) - (average number of dots in time-dependent embedding performance evaluation)|) was calculated. A change in the average number of dots of 15 or less was evaluated as ○, and a change exceeding 15 was evaluated as ×.

[0088] (3) Adhesive residue Figure 2 is a schematic cross-sectional view showing a semiconductor wafer processing adhesive sheet attached to a substrate with a step. A silicon mirror wafer was ground to 500 μm, and an adhesive tape with a thickness of 75 μm was attached to the ground surface of the silicon mirror wafer to create a substrate 200 with a step as shown in Figure 2. The height x of the step in the substrate was 75 μm. The adhesive sheets (semiconductor wafer processing adhesive sheets) 100 obtained in the examples and comparative examples were laminated onto the substrate 200 with a step so as to be perpendicular to the adhesive tape, and were attached using a 2 kg roller at the temperature shown in Table 2. Then, they were stored in a 60°C heating device for 4 days. After that, the semiconductor wafer processing adhesive sheets removed from the heating device were exposed to ultraviolet light (1000 mJ / cm²). 2The wafer was irradiated with a laser. Next, the adhesive sheet was peeled off using a 180° peel test (room temperature, peeling speed 300 mm / min). After peeling, the silicon wafer surface was observed with a laser microscope (magnification: 100x), and evaluated as ○ if no adhesive residue remained, and × if adhesive residue remained.

[0089] (4) Adhesive sheet cutability Using a tape application device (manufactured by Nitto Seiki Co., Ltd., product name: DR-3000III), the adhesive sheets obtained in the examples or comparative examples were applied to 25 silicon mirror wafers under the following conditions. An unused cutter blade was used for application. Application was carried out at the temperatures listed in Table 2. Roll speed: 100 mm / min Roll pressure: 0.4 MPa Cutter speed: 300 mm / min Cutter temperature: 180℃ Blade angle: 1° Cutting angle: 5° Next, the first and 25th silicon mirror wafers were observed from the side using a microscope. Stringing (presence or absence of contact between the intermediate layer and the wafer side) was checked, and a circle (○) was used if no stringing was observed, and a cross (×) if stringing was observed.

[0090] (5) Stickiness on the sides The adhesive sheets (2 cm wide) obtained in the examples and comparative examples were wound onto a 3-inch core until the thickness reached 0.5 cm, thereby obtaining a roll-shaped adhesive sheet winding. The sides of the obtained winding were pressed by hand against an acrylic plate (5 mm thick). Next, the winding was lifted by hand, and it was evaluated as ○ if the acrylic plate did not lift with the winding, and × if the acrylic plate lifted with the winding.

[0091] [Table 2] [Industrial applicability]

[0092] The adhesive sheet for semiconductor wafer processing of the present invention can be suitably used in semiconductor wafer processing processes. [Explanation of symbols]

[0093] 10 Adhesive layer 20 Middle Class 30 Base material 100 Adhesive sheets for semiconductor wafer processing A substrate with a 200 step difference

Claims

1. An adhesive sheet for semiconductor wafer processing comprising a base material, an intermediate layer, and an ultraviolet-curable adhesive layer in this order, The UV-curable adhesive layer is formed from an acrylic adhesive and contains an acrylic resin in which polymerizable carbon-carbon double bonds are introduced into the side chains. The intermediate layer is formed of an acrylic resin, and the monomer component used for polymerization of the acrylic resin contains 1% to 50% by weight of an acrylic monomer having a glass transition temperature of 40°C or higher, Storage modulus G'1 of the intermediate layer at room temperature ＲＴ The pressure is between 300 kPa and 2000 kPa, and the storage modulus G'1 at 80°C is ８０ The pressure ranges from 10 kPa to 500 kPa. Storage modulus G'2 of the UV-curable adhesive layer at room temperature ＲＴ The pressure is between 100 kPa and 1000 kPa, and the storage modulus G'2 at 80°C is ８０ The pressure range is 10 kPa to 1000 kPa. G'1 ＲＴ / G'2 ＲＴ An adhesive sheet for semiconductor wafer processing, wherein the value is 1 or greater.

2. The adhesive sheet for semiconductor wafer processing according to claim 1, wherein the intermediate layer contains a photopolymerization initiator and does not contain an ultraviolet-curable component.

3. The adhesive sheet for semiconductor wafer processing according to claim 1, wherein the acrylic resin contained in the intermediate layer is a polymer obtained by emulsion polymerization or solution polymerization.

4. An adhesive sheet for semiconductor wafer processing according to any one of claims 1 to 3, used as a backgrind tape.

5. The semiconductor wafer processing adhesive sheet according to claims 1 to 3, which is used by attaching it to a semiconductor wafer having an uneven surface.

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