Adhesive sheet for semiconductor wafer processing

Abstract

To provide an adhesive sheet for semiconductor wafer processing capable of sufficiently holding semiconductor wafers even when subjected to processing steps using more powerful lasers.SOLUTION: An adhesive sheet for processing semiconductor wafers according to an embodiment of the present invention comprises a base material and a base material protective layer. In one embodiment, the base material protective layer comprises an adhesive and a diffusion material. In another embodiment, the base material protective layer is a metal layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an adhesive sheet for semiconductor wafer processing, and more particularly to an adhesive sheet used in semiconductor wafer processing using an ultrashort pulse laser. [Background technology]

[0002] Pressure-sensitive adhesive sheets are widely used for the purpose of protecting the surface of an adherend and for fixing the adherend. For example, in the processing of semiconductor wafers, they are used to properly hold the adherend semiconductor wafer during the back-grinding process and the dicing process. In the dicing process, a blade or a laser is typically used to break the semiconductor wafer into small pieces (see, for example, Patent Document 1). The dicing process using a laser is a non-contact process, which imposes a small mechanical load on the semiconductor wafer surface. It may also be possible to cut harder materials that are difficult to cut with a blade. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-63640 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, in order to reduce thermal damage to semiconductor wafers, processing methods using short-wavelength lasers and ultrashort pulse lasers that can process in a shorter time have been proposed. However, when using these lasers, not only the semiconductor wafer but also the adhesive sheet that holds the semiconductor wafer is cut, and it may be difficult to sufficiently hold the semiconductor wafer.

[0005] The present invention has been made to solve the above-mentioned conventional problems, and its object is to provide an adhesive sheet for semiconductor wafer processing that can sufficiently hold a semiconductor wafer even when it is subjected to a processing process using a more powerful laser. [Means for solving the problem]

[0006] 1. A semiconductor processing sheet according to an embodiment of the present invention includes a substrate and a substrate protective layer. 2. In the adhesive sheet for semiconductor wafer processing described in 1 above, the substrate protective layer may contain an adhesive and a diffusion material. 3. In the adhesive sheet for semiconductor wafer processing described in 2 above, the diffusion material may be at least one selected from the group consisting of silicone particles, carbon black particles, zirconia particles, silicon-acrylic particles, melamine particles, acrylic particles, alumina particles, glass beads, and titanium oxide particles. 4. In the adhesive sheet for semiconductor wafer processing described in 1 above, the substrate protective layer may be a metal layer. 5. In the adhesive sheet for semiconductor wafer processing described in 4 above, the metal constituting the metal layer may be at least one selected from the group consisting of gold, copper, iron, zinc, magnesium, manganese, nickel, lead, platinum, tin, titanium, aluminum, and silver. 6. The adhesive sheet for semiconductor wafer processing according to any one of 1 to 5 above may further comprise an adhesive layer. 7. The adhesive sheet for semiconductor wafer processing according to any one of the above items 1 to 6 may be used in a semiconductor chip manufacturing process including laser dicing. 8. In the adhesive sheet for semiconductor wafer processing described in 7 above, the laser used for the laser dicing may be an ultrashort pulse laser. [Effects of the Invention]

[0007] According to an embodiment of the present invention, it is possible to provide an adhesive sheet for semiconductor wafer processing that can sufficiently hold a semiconductor wafer even when subjected to a processing step using a more powerful laser. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view of an adhesive sheet for semiconductor wafer processing according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view of an adhesive sheet for semiconductor wafer processing according to another embodiment of the present invention. [Figure 3] FIG. 10 is a schematic cross-sectional view of an adhesive sheet for semiconductor wafer processing according to yet another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] A. Adhesive sheet for semiconductor wafer processing A-1. Overall structure of adhesive sheet for semiconductor wafer processing A semiconductor processing sheet according to an embodiment of the present invention includes a substrate and a substrate protective layer. The substrate protective layer of the semiconductor wafer processing adhesive sheet according to an embodiment of the present invention prevents the substrate from being cut, even when a more powerful laser, such as an ultrashort pulse laser, is used to cut the semiconductor wafer. This provides an adhesive sheet capable of adequately holding the semiconductor wafer. FIG. 1 is a schematic cross-sectional view of an adhesive sheet according to one embodiment of the present invention. In the illustrated example, the semiconductor wafer processing adhesive sheet 100 includes a substrate 10, a substrate protective layer 20, and an adhesive layer 30. In this embodiment, the substrate protective layer 20 is an adhesive layer having a diffusing material 40 dispersed therein. The semiconductor wafer processing adhesive sheet 100 is bonded to an adherend (e.g., a semiconductor wafer) via the adhesive layer 30. Laser dicing of semiconductor wafers can be performed by irradiating the laser onto the surface of the semiconductor wafer (the adherend) that is not bonded to the semiconductor wafer processing adhesive sheet 100. The laser that penetrates the semiconductor wafer first passes through the adhesive layer 30 and then can penetrate the substrate protective layer 20. The laser that penetrates the substrate protective layer 20 can be diffused and its force dispersed within the substrate protective layer 20 by the diffusing material 40. Therefore, even when fragmentation is performed using a powerful laser such as an ultrashort pulse laser, the force of the laser is reduced within the substrate protective layer 20, and the laser does not reach the substrate 10, or even if it does reach the substrate 10, cutting of the substrate 10 can be suppressed.

[0010] 2 is a schematic cross-sectional view of an adhesive sheet for semiconductor wafer processing according to another embodiment of the present invention. In the illustrated example, the adhesive sheet for semiconductor wafer processing 101 includes a substrate 10 and a substrate protective layer 20. In this embodiment, the substrate protective layer 20 is a layer in which a diffusion material 40 is dispersed in an adhesive. In this embodiment, the substrate protective layer 20 can also function as an adhesive layer. In this embodiment, the adhesive sheet for semiconductor wafer processing 101 is used by bonding the substrate protective layer 20 to an adherend (e.g., a semiconductor wafer).

[0011] FIG. 3 is a schematic cross-sectional view of an adhesive sheet for semiconductor wafer processing according to another embodiment of the present invention. In the illustrated example, the adhesive sheet for semiconductor wafer processing 100′ includes a substrate 10, a substrate protective layer 20, and an adhesive layer 30. In the illustrated example, the substrate protective layer 20 is a metal layer. The adhesive sheet for semiconductor wafer processing 100′ is used by laminating the substrate protective layer 20 to an adherend (e.g., a semiconductor wafer). Semiconductor wafers are diced using a laser by irradiating the surface of the semiconductor wafer (the adherend) that is not laminated with the adhesive sheet for semiconductor wafer processing 100′ with a laser. The laser that penetrates the semiconductor wafer can penetrate the adhesive layer 30. The laser that penetrates the adhesive layer 30 can be reflected by the substrate protective layer 20, which is a metal layer provided on the side of the substrate 10 that can be penetrated by the laser. Therefore, even if fragmentation is performed using a powerful laser such as an ultrashort pulse laser, the laser may not reach the substrate 10, or the laser may be reflected by the adhesive layer 30 at the substrate protective layer 20, resulting in a reduction in the power of the laser, which may prevent cutting even if the laser reaches the substrate layer 10.

[0012] In the illustrated example, an embodiment is specifically described in which a substrate protective layer having a diffusion material dispersed in an adhesive layer, or a substrate protective layer that is a metal layer, but the adhesive sheet for semiconductor wafer processing may also include both a substrate protective layer having a diffusion material dispersed in an adhesive layer, or a substrate protective layer that is a metal layer.

[0013] The adhesive sheet for semiconductor wafer processing may further include any appropriate layer. For example, an intermediate layer (not shown) may be formed between the substrate 10 and the adhesive layer 30 (or the substrate protective layer 20 if the adhesive layer 30 is omitted). When the intermediate layer is included, adhesion to an adherend having an uneven surface may be improved.

[0014] The anchoring strength of the pressure-sensitive adhesive sheet before ultraviolet irradiation is preferably 1 N / 20 mm or more, more preferably 3 N / 20 mm or more, and even more preferably 5 N / 20 mm or more, and is, for example, 30 N / 20 mm or less.

[0015] The anchoring strength of the pressure-sensitive adhesive sheet after ultraviolet irradiation is preferably 1 N / 20 mm or more, more preferably 3 N / 20 mm or more, and even more preferably 5 N / 20 mm or more. The anchoring strength after ultraviolet irradiation is, for example, 30 N / 20 mm or less.

[0016] The thickness of the adhesive sheet for semiconductor wafer processing of the embodiment of the present invention can be set to any appropriate thickness, and is preferably 5 μm to 400 μm, more preferably 50 μm to 200 μm.

[0017] B. Base material The substrate may be made of any suitable resin. Specific examples of resins constituting the substrate include polyester-based resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polybutylene naphthalate (PBN); polyolefin-based 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, cellulose, fluorine-based resins, polystyrene-based resins such as polyether and polystyrene; polycarbonate, polyethersulfone, and polyetheretherketone. Polyolefin-based resins or polyester-based resins are preferred, and polyolefin-based resins are more preferred. Using polyolefin-based resins as these resins can enhance laser transmission through the substrate, thereby further suppressing cutting of the substrate.

[0018] The substrate may further contain other components within the range that does not impair the effects of the present invention. Examples of other components include antioxidants, ultraviolet absorbers, light stabilizers, heat stabilizers, antistatic agents, etc. The types and amounts of other components can be any appropriate amount depending on the purpose.

[0019] In one embodiment, the substrate may be a resin film that has been subjected to a surface treatment. Examples of surface treatments include corona treatment, adhesion-enhancing treatment, and the formation of a surface treatment layer such as a primer layer. The surface treatment layer can be formed by any appropriate method. For example, it can be formed by applying or printing any appropriate composition onto the surface of the substrate. The composition that forms the surface treatment layer preferably contains a compound having a functional group that can interact with the functional group of the compound contained in the pressure-sensitive adhesive composition.

[0020] The thickness of the substrate is preferably 30 μm to 400 μm, more preferably 40 μm to 350 μm, and even more preferably 50 μm to 250 μm.

[0021] C. Adhesive layer The adhesive sheet for semiconductor wafer processing usually includes an adhesive layer. The adhesive layer allows the adhesive sheet for semiconductor wafer processing to adhere to the adherend. The adhesive layer is typically the surface that contacts the adherend. Therefore, when the substrate protective layer is a metal layer, the adhesive layer can be formed on the surface of the metal layer that is not in contact with the substrate. As described above, when the substrate protective layer is made of an adhesive containing a diffusion material, the substrate protective layer can also function as an adhesive layer.

[0022] C-1. Adhesive The adhesive layer is formed using any appropriate adhesive. Any appropriate adhesive can be used as the adhesive. Examples include acrylic adhesives, rubber adhesives, silicone adhesives, and polyvinyl ether adhesives. In one embodiment, an ultraviolet-curable adhesive is used as the adhesive. If an ultraviolet-curable adhesive is used, the adhesive layer can be cured by irradiating it with ultraviolet light, thereby reducing adhesive residue on the adherend. Furthermore, damage to the adherend can be reduced when the adhesive sheet for semiconductor wafer processing is peeled off. Any appropriate adhesive can be used as the ultraviolet-curable adhesive. For example, an adhesive obtained by adding an ultraviolet-curable monomer and / or oligomer to any appropriate adhesive may be used, or an adhesive using a polymer having a carbon-carbon double bond as the base polymer may be used. Preferably, an adhesive using a polymer having a carbon-carbon double bond as the base polymer is used.

[0023] C-1-1. Base polymer The base polymer having a carbon-carbon double bond may have the carbon-carbon double bond in its main chain, in its side chain, or at its terminal. When using a base polymer having a carbon-carbon double bond, a polymer having a polymerizable carbon-carbon double bond and adhesive properties is used as the base polymer. Examples of such polymers include polymers in which a carbon-carbon double bond has been introduced into a resin such as a (meth)acrylic resin, a vinyl alkyl ether resin, a silicone resin, a polyester resin, a polyamide resin, a urethane resin, or a styrene-diene block copolymer. Preferably, a (meth)acrylic polymer in which a carbon-carbon double bond has been introduced into a (meth)acrylic resin is used. The use of a (meth)acrylic polymer makes it easy to adjust the storage modulus and tensile modulus of the adhesive layer, and also enables the production of a pressure-sensitive adhesive sheet with an excellent balance between adhesive strength and releasability. Furthermore, contamination of the adherend by components derived from the adhesive can be reduced. Note that "(meth)acrylic" refers to acrylic and / or methacrylic.

[0024] Any appropriate (meth)acrylic resin can be used as the (meth)acrylic resin, including, for example, a polymer obtained by polymerizing a monomer composition containing one or more esters of acrylic acid or methacrylic acid having a linear or branched alkyl group.

[0025] The linear or branched alkyl group is preferably an alkyl group having 30 or less carbon atoms, more preferably an alkyl group having 1 to 20 carbon atoms, and even more preferably an alkyl group having 4 to 18 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an isobutyl group, an amyl group, an isoamyl group, a hexyl group, a heptyl group, a cyclohexyl group, a 2-ethylhexyl group, an octyl group, an isooctyl group, a nonyl group, an isononyl group, a decyl group, an isodecyl group, an undecyl group, a lauryl group, a tridecyl group, a tetradecyl group, a stearyl group, an octadecyl group, and a dodecyl group.

[0026] Specific examples of esters of acrylic acid or methacrylic acid having a linear or branched alkyl group include 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, and isooctyl (meth)acrylate. 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, and eicosyl (meth)acrylate.

[0027] The monomer composition may contain other monomers copolymerizable with the alkyl (meth)acrylate, if necessary, for the purpose of modifying cohesive strength, heat resistance, crosslinkability, etc. Examples of such monomers include carboxyl group-containing monomers such as acrylic acid and methacrylic acid; acid anhydride monomers such as maleic anhydride and itanoic anhydride; hydroxyl group-containing monomers such as hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate; sulfonic acid group-containing monomers such as styrenesulfonic acid and allylsulfonic acid; nitrogen-containing monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and acryloylmorpholine; aminoalkyl (meth)acrylate monomers such as aminoethyl (meth)acrylate; alkoxyalkyl (meth)acrylate monomers such as methoxyethyl (meth)acrylate; maleimide monomers such as N-cyclohexylmaleimide and N-isopropylmaleimide; N-methylitaconimide and N-ethylitaconimide. Examples of suitable monomers include itaconimide monomers such as methylimide; succinimide monomers; vinyl monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, and methylvinylpyrrolidone; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; glycol-based acrylic ester monomers such as polyethylene glycol (meth)acrylate and polypropylene glycol (meth)acrylate; acrylic ester monomers having heterocycles, halogen atoms, silicon atoms, or the like, such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, and silicone (meth)acrylate; olefin monomers such as isoprene, butadiene, and isobutylene; and vinyl ether monomers such as vinyl ether. These monomer components may be used alone or in combination of two or more. The amount is preferably 1 to 50 parts by weight, more preferably 3 to 25 parts by weight, based on 100 parts by weight of the total monomers in the monomer composition.

[0028] The weight-average molecular weight of the (meth)acrylic resin is preferably 200,000 to 2,000,000, more preferably 300,000 to 1,500,000, and even more preferably 500,000 to 1,000,000. Within these ranges, 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 polymer with a narrow molecular weight distribution, bleeding of low-molecular-weight components can be prevented, and a low-contamination adhesive sheet for semiconductor wafer processing can be obtained. The weight-average molecular weight and number-average molecular weight can be determined by gel permeation chromatography (solvent: tetrahydrofuran, polystyrene equivalent).

[0029] A polymer having a carbon-carbon double bond can be obtained by any appropriate method. For example, it can be obtained by reacting (e.g., condensation reaction, addition reaction) a resin obtained by any appropriate polymerization method with a compound having a polymerizable carbon-carbon double bond. Specifically, when a (meth)acrylic resin is used, the resin can be obtained by polymerizing a (meth)acrylic resin (copolymer) having structural units derived from a monomer having any appropriate functional group in any appropriate solvent, and then reacting the functional group of the acrylic resin with a compound having a polymerizable carbon-carbon double bond that can react with the functional group. The amount of the compound having a polymerizable carbon-carbon double bond 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 appropriate solvent can be used, including, for example, various organic solvents such as ethyl acetate, methyl ethyl ketone, and toluene.

[0030] When reacting a resin with a compound having a polymerizable carbon-carbon double bond as described above, it is preferable that the resin and the compound having a polymerizable carbon-carbon double bond each have a functional group capable of reacting with each other. Examples of functional group combinations include a carboxyl group / epoxy group, a carboxyl group / aziridine group, and a hydroxyl group / isocyanate group. Among these functional group combinations, a combination of a hydroxyl group and an isocyanate group is preferred because it is easy to track the reaction.

[0031] Examples of compounds having a carbon-carbon double bond include 2-isocyanatoethyl methacrylate, methacryloisocyanate, 2-methacryloyloxyethyl isocyanate (2-isocyanatoethyl methacrylate), and m-isopropenyl-α,α-dimethylbenzyl isocyanate.

[0032] When using a pressure-sensitive adhesive containing an ultraviolet-curable monomer and / or oligomer, any suitable monomer or oligomer can be used as the ultraviolet-curable monomer and oligomer. Examples of ultraviolet-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 ultraviolet-curable oligomers include urethane-based oligomers, polyether-based oligomers, polyester-based oligomers, polycarbonate-based oligomers, and polybutadiene-based oligomers. The oligomer preferably has a molecular weight of about 100 to 30,000. The monomers and oligomers may be used alone or in combination of two or more.

[0033] The monomer and / or oligomer may be used in any appropriate amount depending on the type of adhesive used, for example, preferably 5 to 500 parts by weight, more preferably 10 to 100 parts by weight, per 100 parts by weight of the base polymer constituting the adhesive.

[0034] C-2. Photopolymerization initiator As the photopolymerization initiator, any appropriate initiator can be used. Examples of the photopolymerization initiator include acylphosphine oxide photopolymerization initiators such as ethyl 2,4,6-trimethylbenzylphenylphosphinate 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-hydroxycyclohexylphenyl ketone; acetophenone compounds such as methoxyacetophenone, 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 benzil dimethyl ketal; and aromatic compounds such as 2-naphthalenesulfonyl chloride. Sulfonyl chloride compounds; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; benzophenone compounds such as benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, and 2,4-diethylthioxanthone. Examples of the photopolymerization initiator include thioxanthone compounds such as thioxanthone and 2,4-diisopropylthioxanthone; camphorquinone; halogenated ketones; acylphosphonates; and α-hydroxyacetophenones such as 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl-2-methylpropane-1. Preferably, acetophenone compounds can be used. The photopolymerization initiator may be used alone or in combination of two or more.

[0035] As the photopolymerization initiator, commercially available products may be used, for example, Omnirad 127D, Omnirad 379EG, and Omnirad 651, both of which are trade names manufactured by IGM Resins.

[0036] The photopolymerization initiator can be used in any appropriate amount. The content of the photopolymerization initiator is preferably 0.5 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, relative to 100 parts by weight of the ultraviolet-curable adhesive. If the content of the photopolymerization initiator is less than 0.5 parts by weight, the adhesive may not be sufficiently cured when irradiated with ultraviolet light. If the content of the photopolymerization initiator is more than 10 parts by weight, the storage stability of the adhesive may be reduced.

[0037] C-3. Additives The pressure-sensitive adhesive layer-forming composition may contain any appropriate additives as needed, such as crosslinkers, catalysts (e.g., platinum catalysts), tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, conductive materials, UV absorbers, light stabilizers, release modifiers, softeners, surfactants other than phosphate ester surfactants, flame retardants, solvents, and oligomers.

[0038] In one embodiment, the ultraviolet-curable pressure-sensitive adhesive further contains 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 of the crosslinking agent is preferably 10 parts by weight or less, more preferably 0.01 to 10 parts by weight, even more preferably 0.3 to 7 parts by weight, and particularly preferably 0.5 to 5 parts by weight, relative to 100 parts by weight of the base polymer contained in the ultraviolet-curable pressure-sensitive adhesive. The flexibility of the pressure-sensitive adhesive layer can be controlled by the content of the crosslinking agent. If the content of the crosslinking agent is less than 0.01 part by weight, the pressure-sensitive adhesive may become a sol, making it difficult to form a pressure-sensitive adhesive layer. If the content of the crosslinking agent is more than 10 parts by weight, sufficient adhesion to the surface of the adherend may not be obtained.

[0039] 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 preferably, a crosslinking agent having three or more isocyanate groups is used. By using an isocyanate-based crosslinking agent as the crosslinking agent and setting the content of the crosslinking agent within the above range, it is possible to provide an ultraviolet-curable pressure-sensitive adhesive that is excellent in conformability to the irregularities of the adherend surface and in anchoring to the substrate.

[0040] The thickness of the pressure-sensitive adhesive layer can be set to any appropriate value. The thickness of the pressure-sensitive adhesive layer is preferably 5 μm to 500 μm, more preferably 10 μm to 300 μm, and even more preferably 20 μm to 100 μm. When the thickness of the pressure-sensitive adhesive layer is within the above range, sufficient adhesive strength to the adherend can be exerted.

[0041] D. Base material protective layer The substrate protective layer 20 is a layer that can prevent the substrate 10 from being cut during the semiconductor wafer dicing process using a laser. According to the adhesive sheet for semiconductor wafer processing of the embodiment of the present invention, even when the dicing process is performed using a powerful laser such as an ultrashort pulse laser, it is possible to provide an adhesive sheet for semiconductor wafer processing that can prevent the substrate from being cut and sufficiently hold the semiconductor wafer. Examples of substrate protective layers include (I) a substrate protective layer containing an adhesive and a diffusion material, and (II) a substrate protective layer that is a metal layer. Each of these will be described in detail below.

[0042] D-1. Substrate protection layer containing adhesive and diffusion material The substrate protective layer including an adhesive and a diffusing material includes any suitable adhesive and any suitable diffusing material. As described above, the substrate protective layer of this embodiment can diffuse the laser that penetrates the substrate protective layer by the diffusing material 40 in the substrate protective layer 20, thereby dispersing the force. Any suitable adhesive can be used as the adhesive. For example, the adhesives used in the adhesive layer described above can be used. Preferably, an adhesive having high transmittance for the wavelength of the laser used for cutting is used. If such an adhesive is used, the force of the laser is suppressed not only by the diffusing material but also by the adhesive, thereby further preventing the substrate from being cut.

[0043] Any suitable material having light diffusing properties can be used as the diffusing material. Examples include inorganic and organic fine particles. Specific examples include silicone particles, carbon black particles, zirconia particles, silicon-acrylic particles, melamine particles, acrylic particles, alumina particles, glass beads, and titanium oxide particles. The use of these diffusing materials improves the light diffusion in the substrate protective layer, preventing the laser from reaching the substrate, or, even if the laser does reach the substrate, reducing the laser power and preventing the substrate from being cut. Only one type of diffusing material may be used, or two or more types may be used in combination.

[0044] The content of the diffusing material in the substrate protective layer can be set to any appropriate value. For example, the content of the diffusing material in the composition forming the substrate protective layer is preferably 0.3 to 100 parts by weight, more preferably 0.5 to 80 parts by weight, and even more preferably 1 to 50 parts by weight, per 100 parts by weight of the adhesive. If the content is within the above range, cutting of the substrate can be suppressed even when the substrate is subjected to a semiconductor wafer processing step using a powerful laser such as an ultrashort pulse laser.

[0045] The thickness of the substrate protective layer containing the pressure-sensitive adhesive and the diffusion material can be set to any appropriate value. The thickness of the substrate protective layer in this embodiment is preferably 1 μm to 100 μm, more preferably 5 μm to 70 μm, and even more preferably 10 μm to 50 μm. If the thickness of the substrate protective layer is within the above range, cutting of the substrate can be suppressed even when the substrate is subjected to a semiconductor wafer processing step using a powerful laser such as an ultrashort pulse laser.

[0046] The substrate protective layer containing a pressure-sensitive adhesive and a diffusion material can be formed by any suitable method, for example, by mixing any suitable pressure-sensitive adhesive and any suitable diffusion material to prepare a composition for forming the substrate protective layer, and then applying the resulting composition to form the substrate protective layer.

[0047] D-2. Metallic base material protection layer In one embodiment, the substrate protective layer is a metal layer. As described above, if the substrate protective layer is a metal layer, the laser that has penetrated the semiconductor wafer can be reflected by the metal substrate protective layer, thereby preventing the laser from reaching the substrate.

[0048] The metal layer may be made of any suitable metal, such as gold, copper, iron, zinc, magnesium, manganese, nickel, lead, platinum, tin, titanium, aluminum, or silver. A single metal may be used, or two or more metals may be used in combination. The metal layer may be a single layer or a laminate of two or more metals.

[0049] The thickness of the substrate protective layer, which is a metal layer, can be set to any appropriate thickness. The thickness of the substrate protective layer in this embodiment is preferably 0.1 μm to 50 μm, more preferably 0.5 μm to 20 μm, and even more preferably 0.5 μm to 5 μm. If the thickness of the substrate protective layer is within the above range, cutting of the substrate can be suppressed even when the substrate is subjected to a semiconductor wafer processing step using a powerful laser such as an ultrashort pulse laser.

[0050] The substrate protective layer, which is a metal layer, can be formed by any suitable method, for example, by vapor-depositing any suitable metal onto the substrate.

[0051] As described above, the substrate protective layer may include both the substrate protective layer (I) and the substrate protective layer (II). When the substrate protective layer (I) and the substrate protective layer (II) are included, it is preferable to form the substrate protective layer as a metal layer on the substrate, and then form a substrate protective layer containing a pressure-sensitive adhesive and a diffusion material on the metal layer substrate protective layer.

[0052] E. Manufacturing method of adhesive sheet for semiconductor wafer processing The semiconductor wafer processing adhesive sheet of the present invention can be manufactured by any suitable method. For example, it can be obtained by applying an adhesive to a release liner, drying it, forming an adhesive layer on the release liner, and then transferring the adhesive layer to the surface of a substrate on which a substrate protective layer has been separately formed. Alternatively, an adhesive can be applied to the surface of the substrate on which the substrate protective layer has been formed, and then drying it to obtain an adhesive sheet for semiconductor wafer processing. Furthermore, when the substrate protective layer contains an adhesive and a diffusing material, a composition containing an adhesive and a diffusing material may be applied instead of the adhesive that forms the adhesive layer. Various methods can be used to apply the adhesive, 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. Any suitable drying method can be used.

[0053] F. Applications of adhesive sheets for semiconductor wafer processing The adhesive sheet for semiconductor wafer processing according to an embodiment of the present invention can be suitably used in the manufacturing process of semiconductor wafers. Even when subjected to a processing step using a laser, the adhesive sheet for semiconductor wafer processing according to an embodiment of the present invention can prevent the substrate from being cut by the laser, and can adequately hold the semiconductor wafer in the semiconductor wafer processing step. Therefore, it can be suitably used as a dicing tape used in the step of dividing a semiconductor wafer into small pieces using a laser (dicing step). Furthermore, even when used as a dicing tape used in a dicing step using a more powerful laser, for example, an ultrashort pulse laser, it can prevent the substrate from being cut.

[0054] Any suitable laser can be used as the ultrashort pulse laser. For example, a laser using a titanium-sapphire crystal as a medium, or a femtosecond pulse laser obtained by regenerating and amplifying a dye laser, etc. The pulse width of the ultrashort pulse laser is, for example, 10 -12 seconds or less, preferably 10 -12 seconds~10 -15 seconds, more preferably 10 -13 seconds~10 -14 The wavelength used is, for example, about 100 nm to 800 nm. The repetition frequency is, for example, about 1 Hz to 80 MHz, and preferably 10 Hz to 500 kHz. The laser pulse output is, for example, about several mW to several hundred mW. The irradiation energy of the ultrashort pulse laser can be determined depending on the numerical aperture (narrowing of the light source) of the objective lens used when irradiating the material, the moving speed of the laser focus, etc. [Example]

[0055] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0056] [Example 1] An acrylic adhesive and silicone particles were mixed to prepare a composition for forming a substrate protective layer. The above composition for forming a substrate protective layer was applied to a polyolefin resin substrate having a thickness of 210 μm to form a substrate protective layer having a thickness of 40 μm, thereby obtaining an adhesive sheet for semiconductor wafer processing comprising the substrate and the substrate protective layer. A silicon mirror wafer having a thickness of 100 μm was attached to the obtained adhesive sheet for semiconductor wafer processing. Next, an ultrashort pulse laser (pulse width: 10 -11 The silicon mirror wafer was cut by irradiating it with a laser beam (wavelength: 355 nm, repetition rate: 50 kHz, repetition rate: 50 kHz). Thereafter, the adhesive sheet for semiconductor wafer processing was visually inspected for the presence or absence of cuts in the substrate, and it was found that the substrate had not been cut.

[0057] [Example 2] An adhesive sheet for processing a semiconductor wafer was obtained in the same manner as in Example 1, except that glass beads were used instead of the silicone particles. The obtained adhesive sheet for semiconductor wafer processing was used to cut a silicon mirror wafer in the same manner as in Example 1. When visually inspected to see if the substrate of the adhesive sheet for semiconductor wafer processing had been cut, it was found that the substrate had not been cut.

[0058] [Example 3] An adhesive sheet for processing a semiconductor wafer was obtained in the same manner as in Example 1, except that silica particles were used instead of silicone particles. The obtained adhesive sheet for semiconductor wafer processing was used to cut a silicon mirror wafer in the same manner as in Example 1. When visually inspected to see if the substrate of the adhesive sheet for semiconductor wafer processing had been cut, it was found that the substrate had not been cut.

[0059] [Example 4] An adhesive sheet for processing a semiconductor wafer was obtained in the same manner as in Example 1, except that titanium oxide particles were used instead of silicone particles. The obtained adhesive sheet for semiconductor wafer processing was used to cut a silicon mirror wafer in the same manner as in Example 1. When visually inspected to see if the substrate of the adhesive sheet for semiconductor wafer processing had been cut, it was found that the substrate had not been cut.

[0060] [Example 5] Aluminum was vapor-deposited onto a 50 μm-thick polyethylene terephthalate resin substrate to form a 0.5 μm-thick substrate protective layer. An acrylic pressure-sensitive adhesive was then applied to the substrate protective layer to form a 40 μm-thick pressure-sensitive adhesive layer, thereby obtaining a pressure-sensitive adhesive sheet for semiconductor wafer processing comprising the substrate and the substrate protective layer. A silicon mirror wafer having a thickness of 100 μm was attached to the obtained adhesive sheet for semiconductor wafer processing. Next, an ultrashort pulse laser (pulse width: 10 -11 The silicon mirror wafer was cut by irradiating it with a laser beam (wavelength: 355 nm, repetition rate: 50 kHz, repetition rate: 50 kHz). Thereafter, the adhesive sheet for semiconductor wafer processing was visually inspected for the presence or absence of cuts in the substrate, and it was found that the substrate had not been cut.

[0061] [Example 6] An adhesive sheet for processing a semiconductor wafer was obtained in the same manner as in Example 5, except that the metal layer was formed using silver instead of aluminum. The obtained adhesive sheet for semiconductor wafer processing was used to cut a silicon mirror wafer in the same manner as in Example 5. When visually inspected to see if the substrate of the adhesive sheet for semiconductor wafer processing had been cut, the substrate had not been cut.

[0062] (Comparative Example) An adhesive sheet for semiconductor wafer processing was obtained in the same manner as in Example 1, except that silicone particles were not added to the composition for forming a substrate protective layer. The obtained adhesive sheet for semiconductor wafer processing was used to cut a silicon mirror wafer in the same manner as in Example 1. When visually inspected to see if the substrate of the adhesive sheet for semiconductor wafer processing had been cut, it was found that the substrate had been cut at the same time as the silicon mirror wafer. [Industrial Applicability]

[0063] The adhesive sheet for semiconductor wafer processing according to the embodiment of the present invention can be suitably used in semiconductor wafer processing steps including a dicing step using a laser. [Explanation of symbols]

[0064] 10 Base material 20 Base material protection layer 30 adhesive layer 40 Diffusion Materials 100 Adhesive sheet for semiconductor wafer processing 100' Adhesive sheet for semiconductor wafer processing 101 Adhesive sheet for semiconductor wafer processing

Claims

1. An adhesive sheet for semiconductor wafer processing, comprising a substrate and a substrate protective layer.

2. The adhesive sheet for semiconductor wafer processing according to claim 1 , wherein the substrate protective layer comprises an adhesive and a diffusion material.

3. 3. The semiconductor wafer processing adhesive sheet according to claim 2, wherein the diffusion material is at least one selected from the group consisting of silicone particles, carbon black particles, zirconia particles, silicon-acrylic particles, melamine particles, acrylic particles, alumina particles, glass beads, and titanium oxide particles.

4. The adhesive sheet for semiconductor wafer processing according to claim 1 , wherein the substrate protective layer is a metal layer.

5. 5. The adhesive sheet for semiconductor wafer processing according to claim 4, wherein the metal constituting the metal layer is at least one selected from the group consisting of gold, copper, iron, zinc, magnesium, manganese, nickel, lead, platinum, tin, titanium, aluminum, and silver.

6. The adhesive sheet for semiconductor wafer processing according to claim 1 , further comprising an adhesive layer.

7. The adhesive sheet for semiconductor wafer processing according to claim 1, which is used in a semiconductor chip manufacturing process including laser dicing.

8. The adhesive sheet for semiconductor wafer processing according to claim 7 , wherein the laser used for the laser dicing is an ultrashort pulse laser.

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