Sheet for workpiece processing, method for producing sheet for workpiece processing, and method for producing processed workpiece

Abstract

To provide a sheet for workpiece processing that makes it possible to lower environmental burden and to perform favorable dicing of a workpiece.SOLUTION: A sheet for workpiece processing comprises a base material and an adhesive layer laminated on one side of the base material, wherein the adhesive layer comprises an acrylic adhesive composed of a solvent-free adhesive composition containing a tackifier that is liquid at 23°C and 1 atm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a workpiece processing sheet used for processing workpieces such as semiconductor wafers. [Background technology]

[0002] Semiconductor wafers such as silicon and gallium arsenide and various packages are manufactured in large diameters, cut into chips (diced), peeled off (picked up), and then transferred to the next process, the mounting process. At this time, the workpieces such as semiconductor wafers are stacked on an adhesive sheet (hereinafter sometimes referred to as a "workpiece processing sheet") that has a base material and an adhesive layer, and then undergo processing such as backgrinding, dicing, cleaning, drying, expanding, picking up, and mounting.

[0003] As the above-mentioned workpiece processing sheets, there are those in which an adhesive layer is formed using an adhesive composition containing an acrylic copolymer produced by a solution polymerization method (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-106283 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been an increasing demand for reducing environmental impact in various technical fields. This also applies to the technical field related to workpiece processing sheets. For example, there is a demand to reduce components that may have an impact on the environment as much as possible.

[0006] Here, in the workpiece processing sheet disclosed in Patent Document 1, an acrylic copolymer produced by solution polymerization is used during production, and therefore the pressure-sensitive adhesive layer contains a certain amount of organic solvent. Such organic solvents generally have an impact on the environment, and it is desirable to reduce their content as much as possible.

[0007] From this viewpoint, it has been considered to form an adhesive layer of a workpiece processing sheet using an acrylic adhesive formed basically without using an organic solvent. However, when a workpiece processing sheet having an adhesive layer made of such a solvent-free adhesive is used to perform blade dicing of a workpiece such as a semiconductor wafer, there are problems such as chips easily flying off or chipping at the edge of the chip easily occurring.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide a workpiece processing sheet that can reduce the environmental load and enable good dicing of the workpiece. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, first, the present invention provides a workpiece processing sheet comprising a substrate and an adhesive layer laminated on one side of the substrate, characterized in that the adhesive layer is composed of an acrylic adhesive formed from a solventless adhesive composition containing a tackifier that is liquid in an environment of 23°C and 1 atm (Invention 1).

[0010] The workpiece processing sheet according to the above invention (Invention 1) has an adhesive layer composed of an acrylic adhesive formed from a solventless adhesive composition containing a liquid tackifier, as described above, which provides good adhesion to the workpiece, and even when dicing is performed, chip flying and chipping at the chip edges can be effectively prevented, i.e., good dicing can be performed.

[0011] In the above invention (Invention 1), the tackifier preferably has a hydroxy group (Invention 2).

[0012] In the above inventions (Inventions 1 and 2), the tackifier is preferably a rosin-based resin (Invention 3).

[0013] In the above inventions (Inventions 1 to 3), the tackifier is preferably at least one of disproportionated rosin, diethylene glycol ester of hydrogenated rosin, and triethylene glycol ester of rosin (Invention 4).

[0014] Secondly, the present invention provides a method for producing the workpiece processing sheet (Inventions 1 to 4), characterized in that the method comprises a coating step of applying the solventless adhesive composition to one side of the substrate to form a coating film, and a heating step of heating the coating film to form the adhesive layer by curing the coating film (Invention 5).

[0015] Thirdly, the present invention provides a method for manufacturing a processed workpiece, characterized by comprising a lamination step of laminating a workpiece to the surface of the adhesive layer of the workpiece processing sheet (Inventions 1 to 4) opposite the substrate, a processing step of processing the workpiece on the workpiece processing sheet to obtain a processed workpiece stacked on the workpiece processing sheet, and a separation step of separating the processed workpiece from the workpiece processing sheet (Invention 6).

[0016] In the above invention (Invention 6), it is preferable to provide an irradiation step between the processing step and the separation step in which active energy rays are irradiated onto the adhesive layer to harden the adhesive layer and reduce the adhesive strength of the workpiece processing sheet to the processed workpiece (Invention 7). [Effects of the Invention]

[0017] The workpiece processing sheet according to the present invention can reduce the environmental load and can perform dicing of the workpiece well. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described. The workpiece processing sheet according to this embodiment includes a substrate and an adhesive layer laminated on one side of the substrate.

[0019] In the workpiece processing sheet according to this embodiment, the adhesive layer is composed of an acrylic adhesive formed from a solventless adhesive composition containing a liquid tackifier in an environment of 23°C and 1 atm.

[0020] The workpiece processing sheet according to this embodiment contains a solventless adhesive composition used to form the adhesive layer that is substantially free of organic solvents, and thus the use of the workpiece processing sheet according to this embodiment can effectively reduce environmental impact. Here, "substantially free of organic solvents" means that the content of organic solvents in the adhesive layer is 1% by mass or less, particularly 0.5% by mass or less. The content of volatile components in the adhesive layer is preferably 2.5% by mass or less, particularly 1.8% by mass or less.

[0021] Furthermore, in the workpiece processing sheet according to this embodiment, the solventless adhesive composition contains a liquid tackifier at 23°C and 1 atm, thereby enabling the sheet to exhibit good adhesive strength to the workpiece. This allows the workpiece to be sufficiently fixed on the workpiece processing sheet during processing, enabling the workpiece to be processed well. In particular, when blade dicing the workpiece using the workpiece processing sheet according to this embodiment, chips formed can be effectively prevented from flying off and chipping at the chip edges can be effectively prevented.

[0022] 1. Composition of workpiece processing sheet (1) Base material The substrate in this embodiment is not particularly limited as long as it exhibits the desired function when the workpiece processing sheet is used. In particular, the substrate is preferably a resin film primarily composed of a resin-based material. Specific examples include polyolefin-based films such as polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, ethylene-norbornene copolymer film, and norbornene resin film; polyester-based films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate; ethylene-vinyl acetate copolymer film; ethylene-(meth)acrylic acid copolymer film, ethylene-methyl(meth)acrylate copolymer film, and other ethylene-(meth)acrylic acid ester copolymer films; polyvinyl chloride-based films such as polyvinyl chloride film and vinyl chloride copolymer film; (meth)acrylic acid ester copolymer film; polyurethane film; polyimide film; polystyrene film; polycarbonate film; and fluororesin film. Modified films such as these crosslinked films and ionomer films can also be used. The substrate may also be a laminate film formed by laminating multiple of the above-mentioned films. In this laminated film, the materials constituting each layer may be the same or different. Among these, it is preferable to use a polyester film (particularly a polyethylene terephthalate film or a polybutylene terephthalate film) as the substrate. In this specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid. The same applies to other similar terms. In this specification, "polymer" also includes the concept of "copolymer."

[0023] The substrate may contain various additives such as a flame retardant, a plasticizer, an antistatic agent, a lubricant, an antioxidant, a colorant, an infrared absorber, an ultraviolet absorber, an ion scavenger, etc. The content of these additives is not particularly limited, but is preferably set within a range in which the substrate exhibits the desired function.

[0024] The surface of the substrate on which the pressure-sensitive adhesive layer is to be laminated may be subjected to a surface treatment such as a primer treatment, a corona treatment, or a plasma treatment in order to enhance adhesion to the pressure-sensitive adhesive layer.

[0025] The thickness of the substrate can be set appropriately depending on the method for using the workpiece processing sheet, but is preferably 200 μm or less, particularly 150 μm or less, and is preferably 10 μm or more, particularly 25 μm or more.

[0026] (2) Adhesive layer As described above, the pressure-sensitive adhesive layer according to this embodiment is composed of an acrylic pressure-sensitive adhesive formed from a solventless pressure-sensitive adhesive composition containing a tackifier that is liquid at 23° C. and 1 atm. Components other than the tackifier contained in the pressure-sensitive adhesive composition are not particularly limited as long as they enable the formation of a pressure-sensitive adhesive layer composed of an acrylic pressure-sensitive adhesive.

[0027] From the viewpoint of facilitating the formation of a satisfactory pressure-sensitive adhesive layer, the solventless pressure-sensitive adhesive composition preferably contains, in addition to the tackifier, an acrylic oligomer, a crosslinking agent, and a retarder. In this case, the acrylic oligomer is crosslinked by the crosslinking agent, thereby forming a satisfactory pressure-sensitive adhesive layer. The retarder appropriately delays the crosslinking reaction, thereby appropriately extending the pot life of the solventless pressure-sensitive adhesive composition.

[0028] The solventless pressure-sensitive adhesive composition preferably contains a catalyst in addition to the acrylic oligomer and crosslinking agent. In this case, the action of the catalyst efficiently promotes crosslinking of the acrylic oligomer by the crosslinking agent, making it easier to form a desired pressure-sensitive adhesive layer.

[0029] Furthermore, when the adhesive layer is formed from an adhesive having active energy ray curability, the solventless adhesive composition preferably contains a photopolymerization initiator, from the viewpoint of facilitating separation of the processed workpiece from the workpiece processing sheet. The use of a photopolymerization initiator can reduce the polymerization and curing time and the amount of light irradiation when irradiated with active energy rays (especially ultraviolet rays).

[0030] (2-1) Acrylic oligomer The acrylic oligomer is not particularly limited as long as it contains an acrylic monomer as a monomer constituting the oligomer and is capable of undergoing the above-mentioned crosslinking reaction, and known acrylic oligomers can be used. For example, the acrylic oligomer may be an oligomer formed from one or more acrylic monomers, or an oligomer formed from one or more acrylic monomers and a monomer other than the acrylic monomer. In addition, the solventless pressure-sensitive adhesive composition may contain only one acrylic oligomer, or may contain multiple acrylic oligomers.

[0031] From the viewpoint of enabling the above-mentioned crosslinking reaction to proceed satisfactorily, the acrylic oligomer preferably contains, as a monomer unit constituting the oligomer, a monomer having a functional group that can serve as a crosslinking point in the crosslinking reaction.

[0032] As the functional group-containing monomer, it is preferable to use a monomer having a polymerizable double bond and a functional group such as a hydroxy group, a carboxy group, an amino group, a substituted amino group, or an epoxy group in the molecule. Among these, it is preferable to contain at least one of a hydroxy group-containing monomer, an amino group-containing monomer, and a substituted amino group-containing monomer, and it is particularly preferable to use a hydroxy group-containing monomer.

[0033] Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, and these may be used alone or in combination of two or more.

[0034] The acrylic oligomer preferably contains 1% by mass or more, particularly preferably 5% by mass or more, and even more preferably 10% by mass or more of the structural units derived from the functional group-containing monomer. The acrylic oligomer preferably contains 35% by mass or less, particularly preferably 30% by mass or less, and even more preferably 28% by mass or more of the structural units derived from the functional group-containing monomer.

[0035] The acrylic oligomer may contain a monomer unit other than the functional group-containing monomer unit. For example, the acrylic oligomer preferably contains a (meth)acrylic acid ester monomer.

[0036] As the (meth)acrylic acid ester monomer, alkyl(meth)acrylates in which the alkyl group has 1 to 20 carbon atoms are preferably used. In particular, alkyl(meth)acrylates in which the alkyl group has 1 to 18 carbon atoms, such as methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, n-butyl(meth)acrylate, and 2-ethylhexyl(meth)acrylate, are preferably used. These may be used alone or in combination of two or more.

[0037] The acrylic oligomer preferably contains 55% by mass or more, particularly preferably 60% by mass or more, and even more preferably 65% ​​by mass or more, of the structural units derived from the (meth)acrylic acid ester monomer. The acrylic oligomer preferably contains 95% by mass or less, particularly preferably 90% by mass or less, and even more preferably 85% by mass or more, of the structural units derived from the (meth)acrylic acid ester monomer.

[0038] The weight-average molecular weight of the acrylic oligomer is preferably 40,000 or less, particularly preferably 25,000 or less, and even more preferably 18,000 or less. A weight-average molecular weight of 40,000 or less prevents the viscosity of the solventless pressure-sensitive adhesive composition (or a coating solution thereof) from becoming excessively high, making it easier to form a pressure-sensitive adhesive layer with a better surface condition. Furthermore, the weight-average molecular weight is preferably 1,000 or more, particularly preferably 1,500 or more, and even more preferably 2,500 or more. A weight-average molecular weight of 1,000 or more ensures that the pressure-sensitive adhesive layer formed has sufficient cohesive strength, making it easier to exhibit the strength and adhesive strength required of a pressure-sensitive adhesive layer.

[0039] When the acrylic oligomer has a hydroxy group, the hydroxyl value of the acrylic oligomer is preferably 20 mgKOH / g or more, particularly preferably 30 mgKOH / g or more, and even more preferably 100 mgKOH / g or more. When the acrylic oligomer has a hydroxyl value of 20 mgKOH / g or more, the acrylic oligomer has sufficient crosslinking points, which makes it easier to cause a good crosslinking reaction. Furthermore, the hydroxyl value of the acrylic oligomer is preferably 170 mgKOH / g or less. When the acrylic oligomer has a hydroxyl value of 170 mgKOH / g or less, it makes it easier to prevent the crosslinking reaction of the acrylic oligomer from proceeding excessively, and it makes it easier to achieve an appropriate pot life of the solvent-based pressure-sensitive adhesive composition (coating solution thereof).

[0040] In addition, the acrylic oligomer in this embodiment may have an active energy ray-curable group introduced into the side chain. When using such an acrylic oligomer having an active energy ray-curable group introduced into the side chain, the formed adhesive layer will have active energy ray curability. As a result, in a work processing sheet having such an adhesive layer, the adhesive layer can be cured by irradiating it with active energy rays, thereby reducing the adhesive strength to the adherend.

[0041] The above-mentioned acrylic oligomer having an active energy ray-curable group introduced into its side chain is preferably one obtained by reacting the above-mentioned acrylic oligomer (a1) having a functional group-containing monomer unit with an unsaturated group-containing compound (a2) having a functional group bonded to the functional group.

[0042] The functional group of the unsaturated group-containing compound (a2) can be appropriately selected depending on the type of functional group of the functional group-containing monomer unit of the acrylic oligomer (a1). For example, when the functional group of the acrylic oligomer (a1) is a hydroxy group, an amino group, or a substituted amino group, the functional group of the unsaturated group-containing compound (a2) is preferably an isocyanate group or an epoxy group, and when the functional group of the acrylic oligomer (a1) is an epoxy group, the functional group of the unsaturated group-containing compound (a2) is preferably an amino group, a carboxy group, or an aziridinyl group.

[0043] The unsaturated group-containing compound (a2) preferably contains at least one, preferably 1 to 6, more preferably 1 to 4 energy ray-polymerizable carbon-carbon double bonds in one molecule. Specific examples of such unsaturated group-containing compounds (a2) include 2-(meth)acryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, (meth)acryloyl isocyanate, allyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate; acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with hydroxyethyl (meth)acrylate; acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with a polyol compound and hydroxyethyl (meth)acrylate; glycidyl (meth)acrylate; (meth)acrylic acid, 2-(1-aziridinyl)ethyl (meth)acrylate, 2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline, and the like.

[0044] The amount of the unsaturated group-containing compound (a2) is preferably 40 mol % or more, particularly preferably 50 mol % or more, based on the amount of functional groups in the acrylic oligomer (a1), and is preferably 99 mol % or less, particularly preferably 95 mol % or less, and even more preferably 90 mol % or less, based on the amount of functional groups in the acrylic oligomer (a1).

[0045] In the reaction between the acrylic oligomer (a1) and the unsaturated group-containing compound (a2), the reaction temperature, pressure, solvent, time, presence or absence of a catalyst, and type of catalyst can be appropriately selected depending on the combination of the functional groups of the acrylic oligomer (a1) and the unsaturated group-containing compound (a2). As a result, the functional groups present in the acrylic oligomer (a1) react with the functional groups in the unsaturated group-containing compound (a2), and the unsaturated groups are introduced into the side chains of the acrylic oligomer (a1).

[0046] In this embodiment, the weight-average molecular weight of the acrylic oligomer having an active energy ray-curable group introduced into its side chain is preferably 40,000 or less, particularly preferably 25,000 or less, and even more preferably 18,000 or less. A weight-average molecular weight of 40,000 or less prevents the viscosity of the solventless pressure-sensitive adhesive composition (or a coating solution thereof) from becoming excessively high, making it easier to form a pressure-sensitive adhesive layer with a better surface condition. Furthermore, the weight-average molecular weight is preferably 1,000 or more, particularly preferably 1,500 or more, and even more preferably 2,500 or more. A weight-average molecular weight of 1,000 or more ensures that the pressure-sensitive adhesive layer formed has sufficient cohesive strength and is more likely to exhibit the strength and adhesive force required of a pressure-sensitive adhesive layer.

[0047] (2-2) Tackifier The tackifier is not particularly limited as long as it is liquid at 23°C and 1 atm, and known tackifiers can be used. In terms of being liquid, the glass transition temperature (Tg) of the tackifier is preferably 40°C or lower, particularly preferably 30°C or lower, and even more preferably 20°C or lower. By satisfying these conditions, the adhesive layer is more likely to exhibit good adhesive strength. The lower limit of the glass transition temperature is not particularly limited, and is, for example, preferably -40°C or higher, particularly preferably -30°C or higher, and even more preferably -20°C or higher.

[0048] Specific examples of the tackifier include rosin-based resins, terpene-phenolic resins, terpene resins, aromatic hydrocarbon-modified terpene resins, petroleum resins, coumarone-indene resins, styrene-based resins, phenolic resins, xylene resins, etc. Among these, it is preferable to use rosin-based resins because they can easily achieve the desired adhesiveness.

[0049] Examples of the rosin-based resin include raw rosins such as gum rosin, wood rosin, and tall oil rosin; disproportionated products of the raw rosins; stabilized rosins obtained by hydrogenating the raw rosins; and polymerized rosins; esterified products of the rosins; phenol-modified products of the rosins; and unsaturated acid-modified rosins.

[0050] The esterified product refers to an esterified product of the rosins and alcohols described above. Examples of the alcohols include monohydric alcohols such as methanol and 2-ethylhexyl alcohol; dihydric alcohols such as trimethylolethane, trimethylolpropane, ethylene glycol, ethylene glycol monoalkyl ethers, diethylene glycol, diethylene glycol monoalkyl ethers, triethylene glycol, triethylene glycol monoalkyl ethers, polyethylene glycol, polyethylene glycol monoalkyl ethers, propylene glycol, propylene glycol monoalkyl ethers, dipropylene glycol, dipropylene glycol monoalkyl ethers, tripropylene glycol, tripropylene glycol monoalkyl ethers, polypropylene glycol, and polypropylene glycol monoalkyl ethers; trihydric alcohols such as trimethylolethane and trimethylolpropane; tetrahydric alcohols such as pentaerythritol and diglycerin; and hexahydric alcohols such as dipentaerythritol. These alcohols can be used alone or in combination of two or more.

[0051] Examples of the phenol-modified products include those obtained by adding phenols such as phenol and alkylphenols to the rosins, esters of the phenol adducts of the rosins with alcohols, so-called rosin-modified phenolic resins obtained by reacting the rosins with resol-type phenolic resins, and esters thereof.

[0052] Examples of the unsaturated acid-modified rosins include those obtained by modifying the above-mentioned rosins with unsaturated acids such as maleic acid, fumaric acid, and (meth)acrylic acid, as well as esters thereof. These can be used alone or in combination of two or more. The esters of unsaturated acid-modified rosins are those obtained by esterifying the above-mentioned unsaturated acid-modified rosins with the above-mentioned alcohols.

[0053] Among the above, it is preferable to use at least one of disproportionated rosin, diethylene glycol ester of hydrogenated rosin, and triethylene glycol ester of rosin as the tackifier in this embodiment.

[0054] It is also preferable that the tackifier has a hydroxyl group. The use of a tackifier having a hydroxyl group improves the flexibility and polarity of the resulting adhesive. This makes it easier to perform better dicing and picking up using the workpiece processing sheet according to this embodiment.

[0055] In particular, when the tackifier has a hydroxy group, the hydroxyl value of the tackifier is preferably 15 mgKOH / g or more, particularly preferably 50 mgKOH / g or more, and even more preferably 100 mgKOH / g or more. Furthermore, the hydroxyl value of the tackifier is preferably 800 mgKOH / g or less, particularly preferably 500 mgKOH / g or less, and even more preferably 300 mgKOH / g or less. Having a hydroxyl value of the tackifier within the above range facilitates improved compatibility with other materials in the pressure-sensitive adhesive composition.

[0056] The acid value of the tackifier is preferably 5 mgKOH / g or more, particularly preferably 10 mgKOH / g or more, and even more preferably 20 mgKOH / g or more. The acid value of the tackifier is preferably 100 mgKOH / g or less, particularly preferably 50 mgKOH / g or less, and even more preferably 30 mgKOH / g or less. When the acid value of the tackifier is within the above range, compatibility with other materials in the pressure-sensitive adhesive composition is easily improved.

[0057] The content of the tackifier in the solventless pressure-sensitive adhesive composition is preferably 1% by mass or more, particularly preferably 3% by mass or more, and even more preferably 5% by mass or more. The content of the tackifier is preferably 50% by mass or less, particularly preferably 40% by mass or less, and even more preferably 30% by mass or less. When the content of the tackifier is within the above range, the desired adhesive strength is easily exerted, which makes it easier to perform better dicing.

[0058] (2-3) Crosslinking agent The crosslinking agent is not particularly limited as long as it can crosslink the acrylic oligomer, and any known crosslinking agent can be used. In particular, if the acrylic oligomer has the above-mentioned functional group, the crosslinking agent is preferably one that can react with the functional group.

[0059] Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, ammonium salt-based crosslinking agents, etc. The crosslinking agents can be used alone or in combination of two or more.

[0060] Here, when the acrylic oligomer has a hydroxy group as the functional group, it is preferable to use an isocyanate-based crosslinking agent, which has excellent reactivity with the hydroxy group, as the crosslinking agent.

[0061] The isocyanate-based crosslinking agent contains at least a polyisocyanate compound, such as aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as pentamethylene diisocyanate and hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and biuret, isocyanurate, and allophanate forms thereof, as well as adducts obtained by reaction with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil.

[0062] Among these, from the viewpoint of easily and effectively extending the pot life, isocyanurates or allophanates of aliphatic polyisocyanates are preferred, and it is particularly preferred to use at least one of pentamethylene diisocyanate-based isocyanurates, hexamethylene diisocyanate-based isocyanurates, and hexamethylene diisocyanate-based isocyanurates.

[0063] The content of the crosslinking agent in the solventless pressure-sensitive adhesive composition is preferably 10% by mass or more, and particularly preferably 15% by mass or more. When the content of the crosslinking agent is 10% by mass or more, the crosslinking reaction tends to proceed smoothly, and a sufficiently cured pressure-sensitive adhesive layer tends to be formed. Furthermore, the content of the crosslinking agent is preferably 50% by mass or less, and particularly preferably 40% by mass or less. When the content of the crosslinking agent is 50% by mass or less, the solventless pressure-sensitive adhesive composition (coating solution thereof) tends to have an appropriate pot life.

[0064] (2-4) Retarder The retarder is not limited as long as it is capable of delaying the crosslinking reaction of the solventless pressure-sensitive adhesive composition, but from the viewpoint of easily causing a moderate delay, it is preferably a compound having a diketone skeleton.

[0065] The diketone skeleton refers to a skeleton in which two ketone groups are linked via a carbon atom. Examples of compounds having the diketone skeleton include β-diketones and β-diesters, and specific examples include acetylacetone (acac), 2-acetoacetoxyethyl methacrylate (AAEM), methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, and malonic acid esters. Among these, it is preferable to use β-diketones, and specifically, it is preferable to use at least one of acetylacetone and 2-acetoacetoxyethyl methacrylate.

[0066] The content of the retarder in the solventless pressure-sensitive adhesive composition is preferably 2% by mass or more, and particularly preferably 6% by mass or more. When the content of the retarder is 2% by mass or more, the solventless pressure-sensitive adhesive composition (coating solution thereof) tends to have an appropriate pot life. Furthermore, the content of the retarder is preferably 30% by mass or less, and particularly preferably 18% by mass or less. When the content of the retarder is 30% by mass or less, the crosslinking reaction tends to proceed well, and a sufficiently cured pressure-sensitive adhesive layer tends to be formed.

[0067] (2-5) Catalyst The catalyst is not particularly limited as long as it can accelerate the crosslinking reaction between the acrylic oligomer and the crosslinking agent, and known catalysts can be used. From the viewpoint of effectively accelerating the crosslinking reaction, it is preferable to use an organometallic compound as the catalyst. Examples of the organometallic compound include organotitanium compounds, organotin compounds, organozirconium compounds, organobismuth compounds, organolead compounds, and organozinc compounds, and among these, it is preferable to use an organotitanium compound.

[0068] Examples of the organic titanium compound include titanium tetra-2-ethylhexoxide and titanium tetra-normal butoxide, and among these, it is preferable to use titanium tetra-2-ethylhexoxide.

[0069] The content of the catalyst in the solventless pressure-sensitive adhesive composition is preferably 0.05% by mass or more, particularly preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more. When the content of the catalyst is 0.05% by mass or more, the crosslinking reaction tends to proceed smoothly, and a sufficiently cured pressure-sensitive adhesive layer tends to be formed. Furthermore, the content of the catalyst is preferably 4% by mass or less, particularly preferably 2% by mass or less, and even more preferably 0.5% by mass or less. When the content of the catalyst is 4% by mass or less, the solventless pressure-sensitive adhesive composition (coating solution thereof) tends to have an appropriate pot life.

[0070] (2-6) Photopolymerization initiator As the photopolymerization initiator, known ones can be used. Specific examples include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloroanthraquinone, (2,4,6-trimethylbenzyldiphenyl)phosphine oxide, 2-benzothiazole-N,N-diethyldithiocarbamate, oligo{2-hydroxy-2-methyl-1-[4-(1-propenyl)phenyl]propanone}, and 2,2-dimethoxy-1,2-diphenylethan-1-one. These may be used alone or in combination of two or more.

[0071] The content of the photopolymerization initiator in the solventless adhesive composition is preferably 0.5 parts by mass or more, particularly preferably 1 part by mass or more, relative to a total of 100 parts by mass of the active energy ray-curable materials. Furthermore, the content of the photopolymerization initiator is preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less, relative to a total of 100 parts by mass of the active energy ray-curable materials. By having the content of the photopolymerization initiator within the above range, the adhesive layer can be efficiently cured by irradiation with active energy rays, thereby making it easier to effectively reduce the adhesive strength of the workpiece processing sheet to the adherend.

[0072] (2-7) Other ingredients The solvent-free adhesive composition of this embodiment can contain desired additives, such as silane coupling agents, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, refractive index adjusters, etc., as long as the effects of the workpiece processing sheet of this embodiment as described above are not impaired.

[0073] (2-8) Preparation of solventless adhesive composition The solventless adhesive composition according to this embodiment can be produced by mixing a tackifier with other components (particularly, an acrylic oligomer, a crosslinking agent, a retarder, a catalyst, and a photopolymerization initiator) and adding additives as desired.

[0074] Since the solvent-free pressure-sensitive adhesive composition according to the present embodiment is solvent-free and has an appropriate viscosity mainly due to the polymerization components, the solvent-free pressure-sensitive adhesive composition according to the present embodiment can be used as a coating solution without adding a diluent or the like.

[0075] (2-9) Thickness of adhesive layer The thickness of the adhesive layer in this embodiment is preferably 1 μm or more, particularly preferably 3 μm or more, and even more preferably 5 μm or more. The thickness of the adhesive layer is preferably 100 μm or less, particularly preferably 80 μm or less, and even more preferably 60 μm or less. By keeping the thickness of the adhesive layer within the above-mentioned range, the workpiece processing sheet according to this embodiment can easily exhibit the desired adhesiveness.

[0076] (3) Release sheet In the workpiece processing sheet according to this embodiment, a release sheet may be laminated on the side of the adhesive layer opposite the substrate (adhesive side) in order to protect that side until it is attached to the workpiece.

[0077] The release sheet may have any configuration, and may be, for example, a plastic film that has been subjected to a release treatment using a release agent or the like. Specific examples of such plastic films include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene. Silicone-based, fluorine-based, and long-chain alkyl-based release agents can be used, and among these, silicone-based ones are preferred because they are inexpensive and provide stable performance.

[0078] There are no particular limitations on the thickness of the release sheet, and it may be, for example, 20 μm or more and 250 μm or less.

[0079] (4) Other In the workpiece processing sheet according to this embodiment, an adhesive layer may be laminated on the surface of the adhesive layer opposite the substrate. In this case, the workpiece processing sheet according to this embodiment can be used as a dicing / die bonding sheet. In this sheet, a workpiece is attached to the surface of the adhesive layer opposite the adhesive layer, and the adhesive layer is diced together with the workpiece to obtain a chip on which the individualized adhesive layer is laminated. The individualized adhesive layer allows the chip to be easily fixed to the object on which it is to be mounted. As a material for constituting the adhesive layer, it is preferable to use a material containing a thermoplastic resin and a low-molecular-weight thermosetting adhesive component, or a material containing a B-stage (semi-cured) thermosetting adhesive component.

[0080] Furthermore, in the workpiece processing sheet according to this embodiment, a protective film forming layer may be laminated on the adhesive surface of the adhesive layer. In this case, the workpiece processing sheet according to this embodiment can be used as a sheet for both protective film formation and dicing. With such a sheet, a workpiece is attached to the surface of the protective film forming layer opposite the adhesive layer, and the protective film forming layer is diced together with the workpiece to obtain a chip on which a singulated protective film forming layer is laminated. It is preferable that the workpiece has a circuit formed on one side. In this case, the protective film forming layer is typically laminated on the surface opposite the surface on which the circuit is formed. By curing the singulated protective film forming layer at a predetermined timing, a protective film with sufficient durability can be formed on the chip. The protective film forming layer is preferably made of an uncured curable adhesive.

[0081] 2. Physical properties of workpiece processing sheets In the workpiece processing sheet according to this embodiment, the adhesive strength (adhesive strength before irradiation with active energy rays when the adhesive layer is composed of an active energy ray-curable adhesive) to a silicon wafer (the mirror surface of a mirror-finished silicon wafer; the same applies hereinafter) is preferably 700 mN / 25 mm or more, more preferably 1000 mN / 25 mm or more, particularly preferably 2000 mN / 25 mm or more, and even more preferably 3000 mN / 25 mm or more. Having an adhesive strength of 700 mN / 25 mm or more facilitates favorable fixation of the workpiece to the workpiece processing sheet, and facilitates better prevention of chipping and chip edge chipping. While the upper limit of the adhesive strength is not particularly limited, it is preferably 20,000 mN / 25 mm or less, particularly preferably 10,000 mN / 25 mm or less, and even more preferably 7,000 mN / 25 mm or less. Details of the method for measuring the adhesive strength are as described in the test examples below.

[0082] Furthermore, in the workpiece processing sheet according to this embodiment, when the adhesive layer is composed of an active energy ray-curable adhesive, the adhesive strength to a silicon wafer after active energy ray irradiation is preferably 2000 mN / 25 mm or less, particularly preferably 1800 mN / 25 mm or less, and even more preferably 1000 mN / 25 mm or less. Having an adhesive strength to a workpiece of 2000 mN / 25 mm or less after active energy ray irradiation facilitates peeling of the workpiece from the workpiece processing sheet. Furthermore, the adhesive strength to a silicon wafer after active energy ray irradiation is preferably 10 mN / 25 mm or more, particularly preferably 15 mN / 25 mm or more, and even more preferably 20 mN / 25 mm or more. This facilitates preventing unintended separation or detachment of the workpiece after active energy ray irradiation. Details of the method for measuring the adhesive strength are described in the test examples below.

[0083] 3. Manufacturing method of workpiece processing sheet The method for producing the workpiece processing sheet according to the present embodiment is not particularly limited. Preferably, the workpiece processing sheet according to the present embodiment is produced by a method including a coating step of applying the above-mentioned solventless pressure-sensitive adhesive composition to one side of a substrate to form a coating film, and a heating step of heating the coating film to form a pressure-sensitive adhesive layer by hardening the coating film.

[0084] The coating in the coating step can be carried out by a known method, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, etc. The properties of the coating solution of the solventless pressure-sensitive adhesive composition are not particularly limited as long as it allows coating, and the coating solution may contain components for forming the pressure-sensitive adhesive layer as a solute or as a dispersoid.

[0085] In the heating step, heating allows the crosslinking reaction of the solventless pressure-sensitive adhesive composition to proceed satisfactorily, thereby sufficiently curing the coating film to form a pressure-sensitive adhesive layer. The heating temperature is preferably 95°C or higher, more preferably 100°C or higher, particularly preferably 105°C or higher, and even more preferably 110°C or higher. The temperature is preferably 150°C or lower, particularly preferably 145°C or lower, and even more preferably 140°C or lower. The heating time is preferably 1 minute or longer, particularly preferably 1.5 minutes or longer, and even more preferably 2 minutes or longer. The heating time is preferably 6 minutes or shorter, particularly preferably 5 minutes or shorter, and even more preferably 4.5 minutes or shorter. Furthermore, to sufficiently promote the crosslinking reaction, after laminating the pressure-sensitive adhesive layer and the substrate, curing may be performed, for example, by leaving the laminate to stand in an environment of 23°C and a relative humidity of 50% for several days.

[0086] 4. How to use the workpiece processing sheet The workpiece processing sheet according to this embodiment can be used to process workpieces such as semiconductor wafers. That is, after the adhesive surface of the workpiece processing sheet according to this embodiment is attached to the workpiece, the workpiece can be processed on the workpiece processing sheet. Depending on the processing, the workpiece processing sheet according to this embodiment can be used as a backgrinding sheet, dicing sheet, expanding sheet, pickup sheet, etc. Examples of workpieces include semiconductor components such as semiconductor wafers and semiconductor packages, and glass components such as glass plates.

[0087] When the workpiece processing sheet according to this embodiment has the adhesive layer described above, the workpiece processing sheet can be used as a dicing / die bonding sheet. Furthermore, when the workpiece processing sheet according to this embodiment has the protective film forming layer described above, the workpiece processing sheet can be used as a protective film forming / dicing sheet.

[0088] The workpiece processing sheet according to this embodiment is particularly preferably used in the method for manufacturing a processed workpiece, which will be described below. This method comprises a lamination step in which the workpiece is bonded to the surface of the adhesive layer of the workpiece processing sheet according to this embodiment opposite the substrate, a processing step in which the workpiece is processed on the workpiece processing sheet to obtain a processed workpiece stacked on the workpiece processing sheet, and a separation step in which the processed workpiece is separated from the workpiece processing sheet.

[0089] Furthermore, when the adhesive layer of the workpiece processing sheet used is composed of an adhesive that is curable with active energy rays, it is preferable that the manufacturing method includes an irradiation step between the processing step and the separation step in which the adhesive layer is irradiated with active energy rays to harden the adhesive layer and reduce the adhesive strength of the workpiece processing sheet to the processed workpiece.

[0090] Each of these steps will be described below. The lamination of the workpiece and the workpiece processing sheet in the lamination step can be carried out by a conventionally known method. When dicing the workpiece in the subsequent processing step, it is preferable to laminate a ring frame on the adhesive layer side of the workpiece processing sheet in the outer peripheral area of ​​the area where the workpiece is to be laminated. The workpiece to be used may be any desired one depending on the processed workpiece to be manufactured, and the aforementioned examples can be used.

[0091] In the processing step, the workpiece can be subjected to desired processing, such as back grinding, dicing, etc. These processing steps can be performed by conventionally known methods.

[0092] In the irradiation step, the conditions for irradiating the active energy rays are not limited, and can be performed based on a conventionally known method, as long as the adhesive strength of the workpiece processing sheet to the processed workpiece can be reduced to the desired level. The types of active energy rays used include, for example, ionizing radiation, i.e., X-rays, ultraviolet rays, electron beams, etc., and among them, ultraviolet rays are preferred because they are relatively easy to install in irradiation equipment.

[0093] In the separation process, separation is performed by a method that depends on the type of processing and the obtained processed workpiece. For example, if dicing is performed as the processing and chips are obtained by dividing the workpiece into individual pieces, the obtained chips are individually picked up from the workpiece processing sheet using a conventionally known pick-up device. In addition, to facilitate this pick-up, the workpiece processing sheet may be expanded to separate the processed workpieces from each other.

[0094] The above-described manufacturing method of a processed workpiece may include other processes than those described above. For example, after the laminating process, a transport process may be included in which the resulting laminate of the workpiece and the workpiece processing sheet is transported to a predetermined location, or a storage process may be included in which the laminate is stored for a predetermined period of time. Furthermore, after the separating process, a mounting process may be included in which the resulting processed workpiece is mounted on a predetermined base or the like.

[0095] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0096] For example, another layer may be provided between the substrate and the pressure-sensitive adhesive layer, or on the surface of the substrate opposite to the pressure-sensitive adhesive layer. [Example]

[0097] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0098] Example 1 (1) Preparation of solventless adhesive composition To 100 parts by mass (solid content equivalent, same below) of acrylic oligomer (Toagosei Co., Ltd., product name "ARUFON UH-2041", weight average molecular weight: 2,500, hydroxyl value: 120 mgKOH / g, viscosity at 25°C: 12,000 mPa·s, glass transition temperature: -50°C), 3.00 parts by mass of acetylacetone (acac) (Fujifilm Wako Pure Chemical Industries, Ltd., product name "Acetylacetone") as a retarder, 30 parts by mass of pentamethylene diisocyanate-based isocyanurate (Mitsui Chemicals, Inc., product name "STABIO D-370N") as a crosslinking agent, and titanium tetra-2-ethylhexoxide (organotitanium compound, Matsumoto Fine Chemicals, product name "Orgatics") as a catalyst were added. 0.50 parts by mass of acrylic acid acrylate copolymer (TA-30) and 10 parts by mass of disproportionated rosin (manufactured by Arakawa Chemical Industries, Ltd., product name "KE364C", molecular weight: 360, acid value: 35 mg KOH / g, hydroxyl value: 100 mg KOH / g, Tg: -13°C) as a tackifier were added in this order and thoroughly mixed to obtain a coating liquid of a solventless pressure-sensitive adhesive composition (solid content concentration: 100 mass%).

[0099] (2) Formation of adhesive layer The adhesive composition coating solution obtained in step (1) above was applied to the release surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031"), which consists of a 38 μm thick polyethylene terephthalate film with a silicone-based release agent layer formed on one side, using a roll knife coater at a coating speed of 1 m / min, and heated at 130°C for 2 minutes to obtain a laminate with a 25 μm thick adhesive layer formed on the release sheet.

[0100] (3) Preparation of workpiece processing sheet A workpiece processing sheet was obtained by bonding the adhesive layer side of the laminate obtained in step (2) to the easy-adhesion coated surface of a polyethylene terephthalate sheet (manufactured by Mitsubishi Chemical Corporation, thickness: 100 μm) that had been given an easy-adhesion coating as a base material.

[0101] Examples 2 to 6 A workpiece processing sheet was produced in the same manner as in Example 1, except that the type and amount of tackifier (amount added relative to 100 parts by mass of acrylic oligomer as the main component) were changed as shown in Table 1.

[0102] Example 7 An acrylic oligomer (manufactured by Toagosei Co., Ltd., product name "ARUFON UH-2041", weight average molecular weight: 2,500, hydroxyl value: 120 mgKOH / g, viscosity at 25°C: 12,000 mPa·s, glass transition temperature: -50°C) was reacted with methacryloyloxyethyl isocyanate (MOI) in an amount equivalent to 60 mol% of the hydroxy groups of the acrylic oligomer to obtain an acrylic oligomer with active energy ray-curable groups introduced into the side chains.

[0103] 100 parts by mass (solid content equivalent, same below) of the obtained acrylic oligomer (main component) with active energy ray-curable groups introduced into the side chains was mixed with pentamethylene diisocyanate-based isocyanurate (manufactured by Mitsui Chemicals, product name "Stabio") as a crosslinking agent. D-370N"), 30 parts by mass of acetylacetone (acac) as a retarder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name "Acetylacetone"), 3.00 parts by mass of a 1:1 mass ratio mixture of 1-hydroxycyclohexyl phenyl ketone and benzophenone as a photopolymerization initiator (manufactured by BASF, product name "Omnirad 500"), and 10 parts by mass of disproportionated rosin as a tackifier (manufactured by Arakawa Chemical Industries, Ltd., product name "KE364C", molecular weight: 360, acid value: 35 mg KOH / g, hydroxyl value: 100 mg KOH / g, Tg: -13 ° C.) were added in this order and mixed thoroughly to obtain a coating solution (solid concentration: 100 mass%) of a solventless adhesive composition.

[0104] A workpiece processing sheet was produced in the same manner as in Example 1, except that the solventless adhesive composition was used.

[0105] Examples 8 to 11 A workpiece processing sheet was produced in the same manner as in Example 7, except that the type and amount of tackifier (amount added relative to 100 parts by mass of acrylic oligomer as the main component) were changed as shown in Table 1.

[0106] Example 12 A workpiece processing sheet was manufactured in the same manner as in Example 7, except that a polybutylene terephthalate sheet (manufactured by OG Film Co., Ltd., thickness: 80 μm) was used as the substrate and the amount of tackifier (amount compounded per 100 parts by mass of acrylic oligomer as the main agent) was changed as shown in Table 1.

[0107] Examples 13 and 14 A workpiece processing sheet was produced in the same manner as in Example 12, except that the type of tackifier was changed as shown in Table 1.

[0108] Comparative Example 1 A workpiece processing sheet was produced in the same manner as in Example 1, except that no tackifier was used.

[0109] Comparative Example 2 A workpiece processing sheet was produced in the same manner as in Example 7, except that no tackifier was used.

[0110] [Test Example 1] (Measurement of adhesive strength) The workpiece processing sheets produced in the examples and comparative examples were cut into 25 mm wide strips. The release sheet was peeled off from the resulting strip-shaped workpiece processing sheets, and the exposed adhesive surface of the adhesive layer was attached to the mirror-finished surface of a silicon wafer at a temperature of 23 ° C. and a relative humidity of 50% using a 2 kg rubber roller, and left to stand for 20 minutes to obtain a measurement sample. Note that the mirror surface of the silicon wafer was a surface that had been ground for more than one month and had lost activity.

[0111] Using a universal tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon UTM-4-100"), the workpiece processing sheet was peeled from the silicon wafer at a peeling speed of 300 mm / min and a peeling angle of 180°, and the adhesive strength (mN / 25 mm) to the silicon wafer was measured using the 180° peeling method in accordance with JIS Z0237:2009. The adhesive strength obtained in this way was the adhesive strength before ultraviolet irradiation (pre-UV) and is shown in Table 2.

[0112] In addition, for the workpiece processing sheets according to Examples 7 to 14 and Comparative Example 2, which use an active energy ray-curable adhesive as the adhesive, the measurement samples obtained in the same manner as above were irradiated with ultraviolet (UV) light (illuminance: 230 mW / cm ) using an ultraviolet light irradiation device (manufactured by Lintec Corporation, product name "RAD-2010") in an environment of a temperature of 23°C and a relative humidity of 50% 20 minutes after being attached to the silicon wafer. 2 , Light intensity: 190mJ / cm 2) was performed twice. After UV irradiation, the measurement sample was subjected to the same procedure as above, in which the workpiece processing sheet was separated from the silicon wafer, and the adhesive strength (mN / 25 mm) to the silicon wafer was measured. The adhesive strength thus obtained was taken as the adhesive strength after UV irradiation (post-UV), and is shown in Table 2.

[0113] [Test Example 2] (Dicing test) The release sheet was peeled off from the workpiece processing sheet produced in the Examples and Comparative Examples to expose the adhesive layer. One side of a 6-inch silicon wafer (350 μm thick) had been ground using a grinder (Disco Corporation, product name "DFG8540") to a surface roughness of #2000. The exposed surface of the adhesive layer on the workpiece processing sheet was then attached to the ground surface using a laminator. The ground surface of the silicon wafer had been inactive for more than one month since grinding.

[0114] One hour after application, the silicon wafer was diced into individual chips on the workpiece processing sheet using a dicing device (DISCO, product name "DFD6362") under the following dicing conditions: Note that this dicing was performed twice on each independent workpiece processing sheet. Dicing Conditions Chip size: 10mm x 10mm Blade height: 60μm Blade: Product name "ZH05-SD2000-N1-90 CC" Blade rotation speed: 40,000 rpm Cutting speed: 10mm / sec Cutting water amount: 1.0L / min Cutting water temperature: 20℃

[0115] The number of chips that flew off during each of the two dicing processes was then counted. The counts and the total number are shown in Table 2. The total number was then compared to the following criteria to evaluate the chip-fly suppression performance. The results are also shown in Table 2. ◯: The total number of chips was 0. △: The total number of chips that flew off was 1 to 5. ×: The total number of chips flying was 6 or more.

[0116] The number of scattered end chips was counted for each of the two dicing processes. The counts and totals are shown in Table 2. The totals were then compared to the following criteria to evaluate the performance of the device in suppressing scattering of end chips. The results are also shown in Table 2. ⊚: The total number of scattered end chips was 5 or less. ◯: The total number of scattered end chips was 6 to 10. △: The total number of scattered end chips was 11 to 30. ×: The total number of scattered end chips was 31 or more.

[0117] [Test Example 3] (Pickup test) After dicing in Test Example 2, the obtained chips were placed on a workpiece processing sheet and stored for 7 days. Thereafter, for the workpiece processing sheets according to Examples 7 to 14 and Comparative Example 2, which use an active energy ray-curable adhesive as the adhesive, ultraviolet (UV) irradiation (illuminance: 230 mW / cm) was performed on the substrate side of the workpiece processing sheet using an ultraviolet irradiation device (manufactured by Lintec Corporation, product name "RAD-2010"). 2 ,Light amount: 190mJ / cm 2 ) was performed twice to cure the adhesive layer.

[0118] Next, using a pick-up device (Canon Machinery, product name "BESTEM D510"), chips were picked up from the workpiece processing sheet under the following pick-up conditions. <Pickup conditions> Pickup type: 4-pin Pin thrust speed: 5mm / s Pin thrust height: 100~600μm

[0119] Here, the push-up height started at 100 μm and was increased in 100 μm increments. Then, at each push-up height, an attempt was made to pick up five chips, and the smallest push-up height at which all five chips could be picked up was recorded as the minimum push-up height, along with the force required for pick-up (N / 10 mm□). These are shown in Table 2.

[0120] For cases where picking up was not possible, the column for minimum thrust height and pick-up force in Table 2 is marked "Not possible."

[0121] The pickup was evaluated based on the following criteria, and the results are shown in Table 2. 〇: All five chips were picked up at any thrust height. ×: Pickup of all five chips was not achieved at any of the thrust heights.

[0122] Details of the abbreviations and other information listed in Table 1 are as follows: [Base material] PBT: Polybutylene terephthalate sheet (manufactured by OG Films, thickness: 80 μm) PET: Polyethylene terephthalate sheet with an easy-adhesion coating (manufactured by Mitsubishi Chemical Corporation, thickness: 100 μm) [Tackifier] KE364C: Disproportionated rosin (manufactured by Arakawa Chemical Industries, Ltd., product name "KE364C", molecular weight: 360, acid value: 35 mg KOH / g, hydroxyl value: 100 mg KOH / g, Tg: -13°C) Ester Gum HT: Diethylene glycol ester of hydrogenated rosin (manufactured by Arakawa Chemical Industries, Ltd., product name "Ester Gum HT", molecular weight: 610, acid value: 15 mg KOH / g, hydroxyl value: 105 mg KOH / g, Tg: -28) Ester Gum AT: Triethylene glycol ester of rosin (manufactured by Arakawa Chemical Industries, Ltd., product name "Ester Gum AT", molecular weight: 440, acid value: 6 mg KOH / g, hydroxyl value: 35 mg KOH / g, Tg: -18°C)

[0123] [Table 1]

[0124] [Table 2]

[0125] As can be seen from Table 2, the workpiece processing sheets obtained in the examples were able to be diced well. [Industrial Applicability]

[0126] The workpiece processing sheet of the present invention can be suitably used for processing workpieces such as semiconductor wafers.

Claims

1. A workpiece processing sheet comprising a substrate and an adhesive layer laminated on one side of the substrate, The pressure-sensitive adhesive layer is composed of an acrylic pressure-sensitive adhesive formed from a solventless pressure-sensitive adhesive composition containing a tackifier that is liquid in an environment of 23°C and 1 atm. A workpiece processing sheet characterized by:

2. 2. The workpiece processing sheet according to claim 1, wherein the tackifier has a hydroxy group.

3. 2. The workpiece processing sheet according to claim 1, wherein the tackifier is a rosin-based resin.

4. 2. The workpiece processing sheet according to claim 1, wherein the tackifier is at least one of disproportionated rosin, diethylene glycol ester of hydrogenated rosin, and triethylene glycol ester of rosin.

5. A method for manufacturing the workpiece processing sheet according to claim 1, The manufacturing method includes: a coating step of applying the solventless pressure-sensitive adhesive composition to one side of the substrate to form a coating film; a heating step of heating the coating film to form the pressure-sensitive adhesive layer by curing the coating film; A manufacturing method comprising:

6. a lamination step of laminating a surface of the adhesive layer of the workpiece processing sheet according to claim 1 opposite to the substrate to a workpiece; a processing step of processing the workpiece on the workpiece processing sheet to obtain processed workpieces stacked on the workpiece processing sheet; a separation step of separating the processed workpiece from the workpiece processing sheet; A method for manufacturing a machined workpiece, comprising:

7. Between the processing step and the separation step, an irradiation step of irradiating the adhesive layer with active energy rays to harden the adhesive layer and reduce the adhesive strength of the workpiece processing sheet to the processed workpiece; The method for manufacturing a machined workpiece according to claim 6, further comprising:

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