Sheet for workpiece processing

Abstract

The present invention is a workpiece processing sheet provided with a base material and an adhesive layer laminated on one surface side of the base material, the workpiece processing sheet being characterized in that the adhesive layer is composed of an adhesive formed from an adhesive composition containing a blocking agent that blocks a cross-linking reaction, the weight loss rate of the retarder after heating the retarder in an air atmosphere at 60 DEG C for 60 minutes is 5% or less. The sheet for workpiece processing can reduce environmental load, and an adhesive composition for forming an adhesive layer has a sufficient pot life.

Description

Technical Field

[0001] The present invention relates to a workpiece processing sheet used for processing a workpiece such as a semiconductor wafer. Background Art

[0002] Semiconductor wafers such as silicon and gallium arsenide, and various packages are manufactured in a large diameter state, cut into chips (dicing), peeled off (pick up), and then transferred to the mounting process as the next process. At this time, the workpiece such as the semiconductor wafer is stacked on an adhesive sheet (hereinafter sometimes referred to as a "workpiece processing sheet") having a base material and an adhesive layer, and back grinding, dicing, cleaning, drying, expansion, picking up, mounting and other processes are performed.

[0003] As an example of the above-mentioned workpiece processing sheet, Patent Document 1 discloses a workpiece processing sheet including an adhesive layer formed using an adhesive composition containing an acrylic copolymer and a cross-linking agent.

[0004] However, sometimes the pot life of the coating liquid of the adhesive composition (which refers to the time during which the coating liquid is kept in a state that can be used for coating after being mixed for coating, also referred to as "usable period") is appropriately extended to improve the operability of the coating liquid, or to improve the surface state of the adhesive layer formed using the coating liquid, etc. For example, Patent Document 2 discloses an adhesive sheet having an adhesive layer formed using an acrylic adhesive composition containing a retarder, but it is not a sheet for workpiece processing.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2010-106283

[0008] Patent Document 2: Japanese Patent Application Publication No. 2016-94492 Summary of the invention

[0009] 1. Technical issues to be resolved

[0010] In recent years, there has been an increasing demand for reducing environmental load in various technical fields. Such a demand also exists in the technical field related to workpiece processing sheets, for example, it is required to reduce components that have an impact on the environment as much as possible.

[0011] Among them, acetylacetone has been generally used as the above-mentioned inhibitor. However, acetylacetone has a certain degree of toxicity and is preferably not used from the viewpoint of reducing environmental load.

[0012] The present invention has been made in view of such actual circumstances, and an object of the present invention is to provide a workpiece processing sheet which can reduce environmental load and in which an adhesive composition for forming an adhesive layer has a sufficient pot life.

[0013] (II) Technical solution

[0014] In order to achieve the above-mentioned purpose, first, the present invention provides a workpiece processing sheet, which is 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 adhesive, and the adhesive is formed by an adhesive composition containing an inhibitor that inhibits a cross-linking reaction, and after the inhibitor is heated at 60°C for 60 minutes in an air atmosphere, the weight reduction rate of the inhibitor is less than 5% (Invention 1).

[0015] The workpiece processing sheet of the above invention (Invention 1) forms the adhesive layer using the adhesive composition containing the above retarder, and can well reduce environmental load while the above adhesive composition has a sufficient pot life.

[0016] In the above invention (Invention 1), it is preferred that the retardant is a compound having a diketone skeleton (Invention 2).

[0017] In the above invention (Invention 1), it is preferred that the retarder is a compound having a vinyl group (Invention 3).

[0018] In the above invention (Invention 1), it is preferred that the molecular weight of the retarder is 80 or more and 500 or less (Invention 4).

[0019] In the above invention (Invention 1), it is preferred that the retarder is 2-acetoacetoxyethyl methacrylate (Invention 5).

[0020] In the above invention (Invention 1), it is preferred that the adhesive composition contains an acrylic polymer (Invention 6).

[0021] In the above invention (Invention 1), the adhesive composition preferably contains a cross-linking agent (Invention 7).

[0022] (III) Beneficial effects

[0023] The workpiece processing sheet of the present invention can reduce environmental load, and the adhesive composition for forming the adhesive layer has a sufficient pot life. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present invention will be described.

[0025] The workpiece processing sheet of this embodiment comprises a substrate and an adhesive layer laminated on one side of the substrate. In addition, the adhesive layer is composed of an adhesive, and the adhesive is formed of an adhesive composition containing a retarder for retarding a crosslinking reaction. Furthermore, after the retarder is heated at 60° C. for 60 minutes in an air atmosphere, the weight reduction rate of the retarder is 5% or less.

[0026] The adhesive composition in this embodiment can appropriately inhibit the progress of curing due to the inclusion of a retarder, thereby having a sufficient pot life. Thus, when manufacturing the workpiece processing sheet of this embodiment, the adhesive composition can be applied in a manner that makes the thickness uniform, and in addition, the generation of stripes on the surface of the formed adhesive layer can be well suppressed.

[0027] Furthermore, by making the retarder exhibit the above-mentioned weight reduction rate, it is not easy to volatilize even when heated. Therefore, when forming the adhesive layer or when storing or using the workpiece processing sheet, the retarder is not easy to be released from the adhesive layer. As a result, the workpiece processing sheet of this embodiment can well reduce the environmental load.

[0028] 1. Composition of workpiece processing sheets

[0029] (1) Base material

[0030] As the substrate of the present embodiment, as long as the desired function is exerted when using the workpiece processing sheet, it is not particularly limited. In particular, the substrate is preferably a resin film based on the material of the resin system. As its specific example, the polyolefin film of polyethylene film, polypropylene film, polybutylene film, polybutadiene film, polymethylpentene film, ethylene-norbornene copolymer film, norbornene resin film, etc. can be listed; polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, polyethylene naphthalate, etc.; ethylene-vinyl acetate copolymer film; ethylene-(methyl) acrylic acid copolymer film, ethylene-(methyl) methyl acrylate copolymer film, other ethylene-(methyl) acrylic acid ester copolymer films and other ethylene-(methyl) acrylic acid ester copolymer films; polyvinyl chloride films such as polyvinyl chloride film and vinyl chloride copolymer film; (methyl) acrylic acid ester copolymer film; polyurethane film; polyimide film; polystyrene film; polycarbonate film; fluororesin film, etc. In addition, modified films such as cross-linked membranes and ionomer membranes of the above-mentioned components can also be used. In addition, the substrate can also be a laminated film formed by stacking a plurality of the above-mentioned films. In this laminated film, the materials constituting each layer can be of the same type or of different types. Among them, a polyester film (particularly a polyethylene terephthalate film) is preferably used as the substrate. In addition, "(meth) acrylic acid" in this specification refers to both acrylic acid and methacrylic acid. Other similar terms are also the same. In addition, "polymer" in this specification also includes the concept of "copolymer".

[0031] The substrate may contain various additives such as flame retardants, plasticizers, antistatic agents, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, ion scavengers, etc. The content of these additives is not particularly limited, but is preferably within a range in which the substrate exerts the desired function.

[0032] In order to improve the adhesion with the adhesive layer, the surface of the substrate on which the adhesive layer is laminated may be subjected to a surface treatment such as primer treatment, corona treatment, plasma treatment, or the like.

[0033] The thickness of the substrate can be appropriately set according to the method of use of the workpiece processing sheet, and is, for example, preferably 200 μm or less, particularly preferably 150 μm or less. In addition, the thickness of the substrate is preferably 10 μm or more, particularly preferably 25 μm or more.

[0034] (2)Adhesive layer

[0035] As mentioned above, the adhesive constituting the adhesive layer of the present embodiment is formed by the adhesive composition containing the retarder that makes crosslinking reaction retard.As the example of this adhesive, it is not particularly limited, and acrylic acid adhesive, rubber adhesive, silicone adhesive, urethane adhesive, polyester adhesive, polyvinyl ether adhesive etc. can be listed.Wherein, from the angle of easily bringing into play desired adhesive force, preferably use acrylic acid adhesive.In addition, above-mentioned adhesive can have active energy ray curing property, also can not have active energy ray curing property.

[0036] When the adhesive layer of the present embodiment is composed of an acrylic adhesive, it is preferred that the adhesive composition further contains an acrylic polymer and a crosslinking agent in addition to the above-mentioned retardant.

[0037] (2-1) Acrylic polymer

[0038] The units constituting the acrylic copolymer are not particularly limited, and preferably include, for example, a structural unit derived from a reactive functional group-containing monomer or a structural unit derived from a (meth)acrylic acid ester monomer or a derivative thereof.

[0039] The acrylic polymer contains a monomer unit containing a reactive functional group as a constituent of the polymer, and can react with a crosslinking agent described later via the reactive functional group from the monomer containing the reactive functional group. As a result, a crosslinked structure (three-dimensional network structure) can be formed, and an adhesive having a desired cohesive force can be obtained.

[0040] The reactive functional group-containing monomer is preferably a monomer having a polymerizable double bond and a functional group such as a hydroxyl group, a carboxyl group, an amino group, a substituted amino group, or an epoxy group in the molecule.

[0041] Examples of hydroxyl-containing monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. These monomers may be used alone or in combination of two or more.

[0042] As carboxyl group-containing monomers, for example, ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid can be cited. Among them, acrylic acid and methacrylic acid are preferred from the perspective of the cohesive force of the obtained (meth)acrylate polymer (A). These can be used alone or in combination of two or more.

[0043] Examples of the amino group-containing monomer or substituted amino group-containing monomer include aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0044] When the acrylic acid polymer contains the above-mentioned reactive functional group-containing monomer, the mass ratio of the structural part from the above-mentioned reactive functional group-containing monomer in the acrylic acid polymer is preferably 1% by mass or more, particularly preferably 3% by mass or more, and further preferably 5% by mass or more. In addition, the above ratio is preferably 50% by mass or less, particularly preferably 30% by mass or less, and further preferably 25% by mass or less. By making the ratio of the structural part from the reactive functional group-containing monomer within the above range, the acrylic acid polymer is easy to carry out the desired crosslinking reaction with the crosslinking agent, and the resulting adhesive is easy to have good cohesive force.

[0045] As the (meth)acrylic acid ester monomer constituting the acrylic polymer, it is preferable to use an alkyl (meth)acrylate having an alkyl group having 1 to 20 carbon atoms, or the like, from the viewpoint of easily expressing preferred adhesiveness.

[0046] Examples of the (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0047] When the acrylic polymer contains the above-mentioned (meth) alkyl acrylate monomer, the mass ratio of the structural part derived from the above-mentioned (meth) alkyl acrylate monomer in the acrylic polymer is preferably 50 mass % or more, particularly preferably 70 mass % or more, and more preferably 75 mass % or more. In addition, the above ratio is preferably 99 mass % or less, particularly preferably 95 mass % or less, and more preferably 85 mass % or less. By making the ratio of the structural part derived from the (meth) alkyl acrylate monomer within the above range, the desired adhesive force can be easily exerted.

[0048] The acrylic polymer may contain components other than the monomers described above as structural monomers, and may contain, for example, dimethylacrylamide, vinyl formate, vinyl acetate, styrene, a monomer having an alicyclic structure, and the like.

[0049] The polymerization method of the acrylic acid polymer in this embodiment may be a random copolymer or a block copolymer. In addition, the acrylic acid polymer can be obtained by polymerizing the above-mentioned monomers by conventional methods. For example, it can be prepared by polymerization by emulsion polymerization, solution polymerization, suspension polymerization, bulk polymerization, aqueous solution polymerization, etc. Among them, it is preferably prepared by solution polymerization in an organic solvent from the perspective of stability during polymerization and ease of handling during use.

[0050] When the acrylic polymer is prepared by solution polymerization, the weight average molecular weight of the acrylic polymer is preferably 100,000 or more, particularly preferably 300,000 or more, and further preferably 400,000 or more. In addition, the weight average molecular weight is preferably 1.5 million or less, particularly preferably 1.2 million or less, and further preferably 1 million or less.

[0051] When the acrylic polymer is prepared by a method other than the solution polymerization method, the weight average molecular weight of the acrylic polymer (acrylic oligomer) is preferably 1,000 or more, particularly preferably 1,500 or more, and further preferably 2,500 or more. In addition, the weight average molecular weight is preferably 40,000 or less, particularly preferably 25,000 or less, and further preferably 18,000 or less.

[0052] In addition, the adhesive composition of this embodiment may contain one or more of the above-mentioned acrylic polymers. In addition, the adhesive composition of this embodiment may contain other acrylic polymers in addition to the above-mentioned acrylic polymers.

[0053] Furthermore, the adhesive composition of the present embodiment may contain an acrylic polymer having an active energy ray-curable group introduced into the side chain. In this case, the formed adhesive layer exhibits active energy ray curability. The introduction of the active energy ray-curable group can be carried out, for example, by reacting the acrylic polymer having the above-mentioned functional group-containing monomer unit with an unsaturated group-containing compound having a functional group bonded to the functional group.

[0054] (2-2) Cross-linking agent

[0055] As the crosslinking agent, there is no particular limitation as long as it is a crosslinking agent capable of undergoing a crosslinking reaction (particularly a crosslinking agent capable of crosslinking with an acrylic polymer), and a known crosslinking agent can be used. In particular, if the acrylic polymer is a polymer having the above-mentioned reactive group, it is preferred that the crosslinking agent is a crosslinking agent capable of reacting with the reactive group.

[0056] Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, melamine crosslinking agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, ammonium salt crosslinking agents, etc. The crosslinking agent may be used alone or in combination of two or more.

[0057] Among them, when the acrylic polymer has a hydroxyl group as the reactive group, it is preferable to use an isocyanate crosslinking agent having excellent reactivity with the hydroxyl group as the crosslinking agent.

[0058] The isocyanate crosslinking agent contains at least a polyisocyanate compound. As the polyisocyanate compound, for example, aromatic polyisocyanates such as toluene 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 the like, as well as their biuret bodies, isocyanurate bodies, allophanate bodies, and adducts as antiproducts with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil, etc. Among them, from the perspective of reactivity with hydroxyl groups, it is preferred to use trimethylolpropane-modified aromatic polyisocyanates, and it is particularly preferred to use trimethylolpropane-modified toluene diisocyanate.

[0059] When adhesive composition contains above-mentioned acrylic acid polymer and crosslinking agent, relative to acrylic acid polymer 100 mass parts, the content of the crosslinking agent in adhesive composition is preferably more than 0.1 mass parts, particularly preferably more than 1.0 mass parts, more preferably more than 5 mass parts.By making the content of crosslinking agent be more than 0.1 mass parts, crosslinking reaction can be easily carried out well, and easily form the adhesive layer fully solidified.In addition, relative to acrylic acid polymer 100 mass parts, the content of crosslinking agent is preferably below 15 mass parts, particularly preferably below 25 mass parts, more preferably below 35 mass parts.By making the content of crosslinking agent be below 15 mass parts, adhesive composition (coating liquid) can be easily made to have appropriate pot life.

[0060] (2-3) Blockers

[0061] The above-mentioned inhibitor is not particularly limited as long as it can inhibit the crosslinking reaction of the adhesive composition and exhibit the above-mentioned weight loss rate.

[0062] As described above, after the retarder is heated at 60°C for 60 minutes in an air atmosphere, the weight reduction rate of the retarder is less than 5%, but from the perspective of more easily achieving better environmental performance, the weight reduction rate of the retarder is preferably less than 4%, and particularly preferably less than 3%. In addition, there is no particular limitation on the lower limit of the above-mentioned weight reduction rate, and it can be more than 0.01%, particularly more than 0.03%, and even more than 0.05%. The details of the method for determining the above-mentioned weight reduction rate are described in the test examples described later. In addition, the weight reduction rate of the retarder can also be determined by analyzing the adhesive layer of the workpiece processing sheet to determine the retarder.

[0063] From the viewpoint of being easy to produce appropriate retardation, the above-mentioned retardant is preferably a compound having a diketone skeleton. A diketone skeleton is a skeleton in which two ketone groups are connected via a carbon atom.

[0064] In addition, the above-mentioned retarder is preferably a compound having a vinyl group. When the retarder has a vinyl group, the vinyl group reacts with the above-mentioned alkyl polymer or the three-dimensional network structure formed by cross-linking the alkyl polymer through a cross-linking agent, and the retarder is fixed thereon. This makes it difficult for the retarder to migrate from the adhesive layer to the outside, thereby achieving more excellent environmental performance.

[0065] In addition, the molecular weight of the above-mentioned retarder is preferably 80 or more, particularly preferably 120 or more, and further preferably 200 or more. When the molecular weight is 80 or more, the retarder becomes difficult to migrate from the adhesive layer to the outside, thereby achieving better environmental performance. In addition, the molecular weight of the above-mentioned retarder is preferably 500 or less, particularly preferably 400 or less, and further preferably 300 or less. When the molecular weight is 500 or less, the viscosity of the adhesive composition becomes appropriate, and the desired adhesive layer is easily formed.

[0066] Examples of compounds that can be used as the retarder of this embodiment include 2-acetoacetoxyethyl methacrylate (AAEM), methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, malonic acid esters, etc. Among them, 2-acetoacetoxyethyl methacrylate is preferably used.

[0067] When the adhesive composition contains the above-mentioned acrylic polymer and retarder, relative to 100 parts by mass of acrylic polymer, the content of the retarder in the adhesive composition is preferably more than 1 part by mass, particularly preferably more than 3 parts by mass, and more preferably more than 5 parts by mass. By having the content of the retarder be more than 1 part by mass, the adhesive composition (coating liquid) can be easily made to have a moderate pot life. In addition, relative to 100 parts by mass of acrylic polymer, the content of the retarder is preferably less than 20 parts by mass, particularly preferably less than 15 parts by mass, and more preferably less than 10 parts by mass. By having the content of the retarder be less than 20 parts by mass, the cross-linking reaction can be easily carried out well, and a sufficiently cured adhesive layer can be easily formed.

[0068] (2-4) Other ingredients

[0069] As long as it does not impair the above-mentioned effects brought about by the workpiece processing sheet of this embodiment, the desired additives may be added to the adhesive composition of this embodiment, for example, active energy ray-curable components, photopolymerization initiators, catalysts, silane coupling agents, antistatic agents, thickeners, antioxidants, light stabilizers, softeners, fillers, refractive index regulators, etc.

[0070] In particular, when the adhesive layer of the present embodiment is constituted by an active energy ray-curable adhesive, it is preferred that the adhesive composition contains an active energy ray-curable component and a photopolymerization initiator.

[0071] As the above-mentioned active energy ray curable component, monomers and / or oligomers of active energy ray curability can be listed. As specific examples, monofunctional acrylates such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate can be listed; trimethylolpropane tri(meth) acrylate, pentaerythritol tri(meth) acrylate, pentaerythritol tetra(meth) acrylate, dipentaerythritol hexa(meth) acrylate, 1,4-butanediol di(meth) acrylate, 1,6-hexanediol di(meth) acrylate, polyethylene glycol di(meth) acrylate, dihydroxymethyl tricyclodecane di(meth) acrylate and other multifunctional acrylates; polyester oligomeric (meth) acrylate, polyurethane oligomeric (meth) acrylate, etc. These can be used alone or in combination of two or more.

[0072] When the adhesive composition of the present embodiment contains the above-mentioned acrylic polymer and an active energy ray-curable component, the content of the active energy ray-curable component in the adhesive composition is preferably 5 parts by mass or more, particularly preferably 10 parts by mass or more, and further preferably 20 parts by mass or more, relative to 100 parts by mass of the acrylic polymer. In addition, the content is preferably 1,000 parts by mass or less, particularly preferably 800 parts by mass or less, and further preferably 500 parts by mass or less, relative to 100 parts by mass of the acrylic polymer.

[0073] Examples of the photopolymerization initiator include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin benzoic acid methyl ester, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl -propane-1-one, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzil, bibenzyl, diacetyl, β-chloroanthraquinone, (2,4,6-trimethylbenzyldiphenyl)phosphine oxide, 2-benzothiazolyl diethyldithiocarbamate, oligo {2-hydroxy-2-methyl-1-[4-(1-propenyl)phenyl]propanone}, 2,2-dimethoxy-1,2-diphenylethane-1-one, etc. These may be used alone or in combination of two or more.

[0074] When the adhesive composition of the present embodiment contains a photopolymerization initiator, the content of the photopolymerization initiator in the adhesive composition is preferably 0.1 parts by mass or more, particularly preferably 0.5 parts by mass or more, and further preferably 1 parts by mass or more, relative to 100 parts by mass of the active energy ray-curable component. In addition, the content is preferably 20 parts by mass or less, particularly preferably 15 parts by mass or less, and further preferably 10 parts by mass or less, relative to 100 parts by mass of the active energy ray-curable component.

[0075] (2-5) Preparation of adhesive composition

[0076] As an example, the adhesive composition of the present embodiment can be prepared by, for example, preparing the above-mentioned acrylic copolymer and mixing the obtained acrylic copolymer with a crosslinking agent, a retarder, and other components added as needed.

[0077] The acrylic copolymer can be manufactured by polymerizing a mixture of monomers constituting the polymer by a common free radical polymerization method. Preferably, a polymerization initiator is used as needed and the polymerization is carried out by a solution polymerization method. As the polymerization solvent, for example, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, etc. can be listed, and two or more kinds can be used simultaneously.

[0078] After obtaining the acrylic copolymer, a crosslinking agent, a retardant, and other components added as needed and a diluent solvent are added to the acrylic copolymer solution and fully mixed to obtain a coating liquid of an adhesive composition. In addition, when any of the above components is a solid substance, or when precipitation occurs when mixed with other components in an undiluted state, the component can be dissolved or diluted in a diluent solvent alone in advance and then mixed with other components.

[0079] As the above-mentioned dilution solvent, for example, aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as dichloromethane and dichloroethane; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and melting agent solvents such as ethyl melting agent.

[0080] As the concentration and viscosity of the coating fluid thus prepared, as long as it is the scope that can be coated, then there is no particular restriction, and it can be appropriately selected according to the situation.For example, so that the concentration of the adhesive composition is more than 10 mass % and the mode below 60 mass % is diluted.In addition, when obtaining the coating fluid, the addition of diluting solvent etc. is not a necessary condition, as long as the adhesive composition is the viscosity that can be coated, then diluting solvent can not be added.In this case, the adhesive composition is the coating fluid that directly uses the polymerization solvent of acrylic acid polymer as diluting solvent.

[0081] (2-6) Thickness of adhesive layer

[0082] The thickness of the adhesive layer of the present embodiment is preferably 1 μm or more, particularly preferably 3 μm or more, and more preferably 5 μm or more. In addition, the thickness of the adhesive layer is preferably 100 μm or less, particularly preferably 80 μm or less, and more preferably 60 μm or less. When the thickness of the adhesive layer is within the above range, the workpiece processing sheet of the present embodiment is easy to exert the desired adhesion.

[0083] (3) Peel sheet

[0084] The workpiece processing sheet of the present embodiment may be laminated with a release sheet on the surface of the adhesive layer opposite to the substrate (hereinafter sometimes referred to as “adhesive surface”) in order to protect the surface until the workpiece is attached to the surface.

[0085] The composition of the release sheet is arbitrary, and a film obtained by subjecting a plastic film to a release treatment using a release agent or the like can be exemplified. Specific examples of the plastic film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene or polyethylene. As the release agent, silicone-based, fluorine-based, and long-chain alkyl-based films can be used, and silicone-based films are preferred because they are low-cost and can provide stable performance.

[0086] The thickness of the release sheet is not particularly limited, and may be, for example, 20 μm or more and 250 μm or less.

[0087] (4) Others

[0088] In the workpiece processing sheet of the present embodiment, an adhesive layer can be stacked on the surface of the adhesive layer on the opposite side of the substrate. At this time, the workpiece processing sheet of the present embodiment can be used as a cutting and solidifying chip. In this sheet, the workpiece is attached to the surface of the adhesive layer on the opposite side of the adhesive layer, and the adhesive layer is cut together with the workpiece, thereby obtaining a singulated chip stacked with an adhesive layer. Through the singulated adhesive layer, the chip can be easily fixed on the object carrying the chip. As the material constituting the above-mentioned adhesive layer, it is preferred to use a material containing a thermoplastic resin and a low-molecular-weight thermosetting adhesive component, a material containing a B-stage (semi-cured) thermosetting adhesive component, etc.

[0089] In addition, in the workpiece processing sheet of the present embodiment, a protective film forming layer can also be stacked on the adhesive surface of the adhesive layer. In this case, the workpiece processing sheet of the present embodiment can be used as a protective film forming sheet and a cutting sheet. In such a sheet, a workpiece is attached to the surface of the protective film forming layer on the opposite side of the adhesive layer, and the protective film forming layer is cut together with the workpiece, thereby obtaining a singulated chip stacked with a protective film forming layer. As the workpiece, it is preferred to use a workpiece with a circuit formed on one surface, and in this case, the protective film forming layer is usually stacked on the surface opposite to the surface on which the circuit is formed. The singulated protective film forming layer can form a protective film with sufficient durability on the chip by curing it for a specified time. The protective film forming layer is preferably formed of an uncured curable adhesive.

[0090] 2. Method for manufacturing sheet for workpiece processing

[0091] The method for producing the workpiece processing sheet of the present embodiment is not particularly limited, but it is preferably produced by laminating an adhesive layer on one side of a substrate.

[0092] The adhesive layer can be laminated to the single-sided side of the substrate by a known method. For example, it is preferred that the adhesive layer formed on the release sheet is transferred to the single-sided side of the substrate. At this time, a coating liquid containing an adhesive composition constituting the adhesive layer and a solvent or a dispersion medium further added as needed is prepared, and the coating liquid is applied to the peeled surface (hereinafter, sometimes referred to as "peeling surface") of the release sheet by a die coater, a curtain coater, a spray coater, a slit coater, a blade coater, an applicator, etc. to form a coating film, and the coating film is dried to form an adhesive layer. As long as the coating liquid can be applied, its shape is not particularly limited, and sometimes contains a component for forming an adhesive layer as a solute, and sometimes contains a component for forming an adhesive layer as a dispersed substance. The release sheet of the laminate can be peeled off as an engineering material, and can also be used to protect the adhesive surface of the adhesive layer before the workpiece processing sheet is attached to the adherend.

[0093] When the coating liquid for forming the adhesive layer contains a crosslinking agent, the crosslinking reaction between the acrylic copolymer and the crosslinking agent in the coating film is carried out by changing the above-mentioned drying conditions (temperature, time, etc.) or by separately providing a heat treatment, so as to form a crosslinked structure with a desired density in the adhesive layer. In order to fully carry out the crosslinking reaction, the adhesive layer is laminated on the substrate by the above-mentioned method, and then the obtained workpiece processing sheet is left to stand for several days in an environment of, for example, 23° C. and a relative humidity of 50% for aging.

[0094] Instead of transferring the adhesive layer formed on the release sheet to one side of the substrate as described above, the adhesive layer can be directly formed on the substrate. In this case, the coating film is formed by applying the coating liquid for forming the adhesive layer to one side of the substrate, and the coating film is dried to form the adhesive layer.

[0095] 3. How to use the workpiece processing sheet

[0096] The workpiece processing sheet of this embodiment can be used for processing workpieces such as semiconductor wafers. That is, after the adhesive surface of the workpiece processing sheet of this embodiment is attached to the workpiece, the workpiece can be processed on the workpiece processing sheet. Through this processing, the workpiece processing sheet of this embodiment can be used as a back grinding sheet, a cutting sheet, an expansion sheet, a pick-up sheet, etc. Among them, as examples of workpieces, semiconductor components such as semiconductor wafers and semiconductor packages; glass components such as glass plates can be listed.

[0097] In addition, when the workpiece processing sheet of the present embodiment has the above-mentioned adhesive layer, the workpiece processing sheet can be used as a cutting and fixing wafer. Further, when the workpiece processing sheet of the present embodiment has the above-mentioned protective film forming layer, the workpiece processing sheet can be used as a protective film forming sheet and a cutting sheet.

[0098] In addition, when the adhesive layer of the workpiece processing sheet of the present embodiment is composed of an adhesive that exhibits active energy ray curing properties, it is preferably irradiated with active energy rays as described below during use. That is, it is preferred that the adhesive layer be irradiated with active energy rays before the processed workpiece is separated from the workpiece processing sheet. Thus, the adhesive layer is cured, the adhesive force of the adhesive sheet relative to the processed workpiece is well reduced, and the processed workpiece is easily separated.

[0099] The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments also covers all design changes or equivalents within the technical scope of the present invention.

[0100] For example, another layer may be laminated between the base material and the adhesive layer of the workpiece processing sheet of the present embodiment or on the surface of the base material on the opposite side to the adhesive layer.

[0101] Example

[0102] Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to these Examples and the like.

[0103] [Example 1]

[0104] (1) Preparation of acrylic polymer

[0105] In a reaction apparatus equipped with a stirrer, a condenser, a thermometer, and a nitrogen inlet pipe, 80 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of methyl methacrylate, 10 parts by mass of 2-hydroxyethyl acrylate, and 0.1 parts by mass of azobisisobutyronitrile as a polymerization initiator were added, and the air in the reaction container was replaced with nitrogen. Then, the mixture was reacted at 60° C. in ethyl acetate as a solvent for 24 hours to obtain a solution containing an acrylic polymer (solid content concentration 35% by mass).

[0106] (2) Preparation of adhesive composition

[0107] 100 parts by mass (solid content conversion, the same below) of the obtained acrylic polymer, 5 parts by mass of 2-acetoacetoxyethyl methacrylate (AAEM) (manufactured by Mitsubishi Chemical Group Corporation) as a retarder, and 10 parts by mass of an isocyanate crosslinking agent (manufactured by TOSOH CORPORATION; trade name "Coronate L") as a crosslinking agent were mixed in a solvent to obtain a coating liquid of an adhesive composition (solid content concentration 35% by mass).

[0108] (3) Preparation of sheets for workpiece processing

[0109] The coating liquid of the adhesive composition obtained in the above step (2) was applied to the release surface of a release sheet (manufactured by LINTEC Corporation; product name "SP-PET3810") having a silicone release agent layer formed on one surface of a polyethylene terephthalate film having a thickness of 38 μm using a roll knife coater, and the coating liquid was dried at 90° C. for 1 minute to obtain a laminate having an adhesive layer having a thickness of 10 μm formed on the release sheet.

[0110] The adhesive layer-side surface of the obtained laminate was bonded to one surface of an ethylene-methacrylic acid copolymer (EMAA) film (thickness: 80 μm) as a substrate to obtain a workpiece processing sheet in which a release sheet, an adhesive layer and a substrate were laminated in this order.

[0111] [Example 2]

[0112] Except having changed the composition of the monomer which comprises an acrylic polymer as described in Table 1, it carried out similarly to Example 1, and produced the sheet|seat for workpiece|work processing.

[0113] [Example 3]

[0114] The composition of the monomers constituting the acrylic polymer was changed as described in Table 1, and a workpiece processing sheet was produced in the same manner as in Example 1, except that 100 parts by mass of a difunctional urethane acrylate (weight average molecular weight: about 3,000) as an active energy ray-curable component and 4 parts by mass of 1-hydroxycyclohexyl phenyl ketone (manufactured by BASF, trade name "Omnirad 184") as a photopolymerization initiator were added when preparing the adhesive composition.

[0115] [Comparative Example 1]

[0116] A workpiece processing sheet was produced in the same manner as in Example 1 except that acetylacetone (acac) (manufactured by FUJIFILM Wako Pure Chemical Corporation, trade name "Acetylacetone") was used as a retarder.

[0117] [Comparative Example 2]

[0118] A workpiece processing sheet was produced in the same manner as in Example 1 except that no retarder was used.

[0119] [Test Example 1] (Measurement of weight reduction rate)

[0120] For the retarder used in the examples and comparative examples, the weight loss rate due to heating was measured using a differential thermal and thermogravimetric simultaneous measuring apparatus (manufactured by SHIMADZUCORPORATION; product name "DTG-60"). Specifically, first weigh 20 mg of the retarder and put it in an aluminum pan. The mass of the retarder is recorded as the mass before heating. Next, the temperature is raised from 25°C to 60°C in an air atmosphere at a heating rate of 10°C / min, and the mass (g) of the retarder after being kept at 60°C for 60 minutes is measured.

[0121] Then, the weight reduction rate (%) of the retarder was calculated according to the following calculation formula. The results are shown in Table 1.

[0122] {(mass before heating) - (mass after heating)} / (mass before heating) × 100 = weight reduction rate (%)

[0123] Furthermore, based on the above-mentioned weight reduction rate (%), the performance of the retarder was evaluated according to the following criteria. The results are also shown in Table 1.

[0124] ○: Weight reduction rate is 5% or less.

[0125] ×: Weight reduction rate is greater than 5%.

[0126] [Test Example 2] (Evaluation of coating properties)

[0127] The coating liquid of the adhesive composition prepared in the examples and comparative examples was stored in a lightly sealed container at 23°C for 24 hours. Then, the coating liquid was applied to the release surface of the release sheet in the same manner as in step (2) of Example 1 above, and the condition during coating was confirmed. Then, the coating properties were evaluated according to the following criteria. The results are shown in Table 1.

[0128] ○: The entire release surface can be coated with a uniform thickness.

[0129] ×: The entire release surface cannot be coated, or the coating cannot be performed with a uniform thickness.

[0130] [Test Example 3] (Evaluation of environmental performance)

[0131] The retarders used in the examples and comparative examples were checked for toxic and hazardous substances as specified in the Toxic and Hazardous Substances Control Act and for any of the GHS classifications, and the environmental performance of the retarders was evaluated according to the following standards. The results are shown in Table 1.

[0132] ○: It is not a toxic or hazardous substance specified in the Toxic and Hazardous Substances Control Act and is not classified in the GHS classification.

[0133] ×: It is a toxic or hazardous substance specified in the Toxic and Hazardous Substances Control Act, or belongs to one of the GHS classifications.

[0134] [Test Example 4] (Evaluation of operability)

[0135] The blockers used in the examples and comparative examples were left open for 5 minutes to check for the presence of odor. At this time, the distance from the blocker to the nose was set to 5 cm. The operability of the blocker was then evaluated based on the following criteria. The results are shown in Table 1.

[0136] ○: No odor

[0137] ×: There is a peculiar smell.

[0138] In addition, the details of the abbreviations and the like described in Table 1 are as follows.

[0139] [Acrylic polymer]

[0140] 2EHA: 2-Ethylhexyl acrylate

[0141] MMA: Methyl Methacrylate

[0142] HEA: 2-Hydroxyethyl Acrylate

[0143] BA: n-butyl acrylate

[0144] AA: Acrylic acid

[0145] [Blockers]

[0146] AAEM: 2-acetoacetoxyethyl methacrylate (manufactured by Mitsubishi Chemical Group Corporation)

[0147] acac: Acetylacetone (manufactured by FUJIFILM Wako Pure Chemical Corporation, trade name "Acetylacetone")

[0148] [Table 1]

[0149]

[0150] As can be seen from Table 1, the workpiece processing sheet of the example has excellent coating properties of the coating liquid of the adhesive composition and a sufficiently long pot life of the coating liquid. In addition, the retarder used in the preparation of the workpiece processing sheet of the example has excellent environmental performance and hardly produces any odor problem.

[0151] Industrial Applicability

[0152] The workpiece processing sheet of the present invention can be suitably used for processing a workpiece such as a semiconductor wafer.

Claims

1. A workpiece processing sheet comprising a base material and an adhesive layer laminated on one side of the base material, characterized in that: The adhesive layer is composed of an adhesive, and the adhesive is formed of an adhesive composition containing an inhibitor for inhibiting a cross-linking reaction. After the retarder is heated at 60° C. for 60 minutes in an air atmosphere, the weight reduction rate of the retarder is 5% or less.

2. The workpiece processing sheet according to claim 1, characterized in that: The blocker is a compound having a diketone skeleton.

3. The workpiece processing sheet according to claim 1, characterized in that: The retarder is a compound having a vinyl group.

4. The workpiece processing sheet according to claim 1, characterized in that: The molecular weight of the retarder is 80 or more and 500 or less.

5. The workpiece processing sheet according to claim 1, characterized in that: The retarder is 2-acetoacetoxyethyl methacrylate.

6. The workpiece processing sheet according to claim 1, characterized in that: The adhesive composition contains an acrylic polymer.

7. The workpiece processing sheet according to claim 1, characterized in that: The adhesive composition contains a cross-linking agent.

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