Workpiece processing sheet and method for using same

Abstract

The present invention provides a workpiece processing sheet provided with a base material and an adhesive layer laminated on the single sheet side of the base material, the adhesive layer comprising an emulsion-based adhesive formed from an adhesive composition containing an acrylic polymer, the acrylic polymer has a benzophenone group structure represented by the following formula (1). The sheet for workpiece processing is a novel sheet for workpiece processing which can reduce environmental load and can easily control adhesive force. In the formula (1), R1 represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, respectively.

Description

Technical Field

[0001] The present invention relates to a workpiece processing sheet used for processing workpieces such as semiconductor wafers and a method of using the sheet. Background Art

[0002] Semiconductor wafers such as silicon and gallium arsenide and various packages are manufactured in a large diameter state, cut (diced) into chips, peeled (picked 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 having a base material and an adhesive layer (hereinafter sometimes referred to as a "workpiece processing sheet"), and is processed and handled such as back grinding, dicing, cleaning, drying, expanding (expanding), picking up, and mounting.

[0003] In the above-mentioned workpiece processing sheet, as the above-mentioned adhesive layer, an adhesive layer composed of an adhesive having active energy ray curability is sometimes used. In this case, by irradiating the adhesive layer with active energy rays, the adhesive force of the adhesive layer to the workpiece can be reduced, thereby making it easy to separate the workpiece from the adhesive sheet (for example, pick up). Examples of such workpiece processing sheets are disclosed in Patent Documents 1 and 2.

[0004] In particular, in the workpiece processing sheet disclosed in Patent Document 1, the adhesive layer is composed of an acrylic adhesive containing a radiation-polymerizable compound having two or more unsaturated bonds. In addition, in the workpiece processing sheet disclosed in Patent Document 2, the adhesive layer is composed of an acrylic adhesive containing an acrylic polymer having a radiation-curable carbon-carbon double bond in the molecule.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 5032740

[0008] Patent Document 2: Japanese Patent No. 5764518 Summary of the invention

[0009] 1. Technical issues to be resolved

[0010] In recent years, electronic components using semiconductor materials and the like have become increasingly miniaturized and complex, and it is hoped that the workpiece processing sheets used can meet these needs. From this perspective, new workpiece processing sheets are being developed, especially workpiece processing sheets that can control adhesion in a new way.

[0011] In addition, in the past workpiece processing sheets such as Patent Documents 1 and 2, an adhesive composition dissolved and mixed in an organic solvent is used in the formation of the adhesive layer. In this case, there is a possibility of volatilization of the organic solvent when forming the adhesive layer, and movement of the residual organic solvent from the adhesive layer to the surrounding when using the workpiece processing sheet. Therefore, from the perspective of reducing the environmental load, it is also required to avoid using such organic solvents.

[0012] The present invention has been made in view of such actual conditions, and an object of the present invention is to provide a novel workpiece processing sheet capable of reducing environmental load and easily controlling adhesive force.

[0013] (II) Technical solution

[0014] In order to achieve the above-mentioned object, first, the present invention provides a workpiece processing sheet, which is a workpiece processing sheet comprising a substrate and an adhesive layer laminated on a single sheet side of the substrate, characterized in that the adhesive layer is composed of an emulsion adhesive formed by an adhesive composition containing an acrylic polymer, and the acrylic polymer has a benzophenone group (benzophenyl) structure represented by the following formula (1):

[0015] [Chemical formula 1]

[0016]

[0017] In formula (1), R 1 Each represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms (Invention 1).

[0018] In the workpiece processing sheet of the above invention (Invention 1), the adhesive layer is formed using the acrylic polymer having the benzophenone group structure, thereby enabling the adhesive force to be controlled in a new manner. Furthermore, the adhesive layer is composed of an emulsion adhesive, thereby enabling the environmental load to be reduced well.

[0019] In the above invention (Invention 1), the acrylic polymer preferably contains a monomer having a benzophenone group structure represented by the formula (1) as a monomer unit constituting the polymer (Invention 2).

[0020] In the above invention (Invention 1), the acrylic polymer preferably has a structure represented by the following formula (2):

[0021] [Chemical formula 2]

[0022]

[0023] In formula (2), R 2 and R 3Each of them represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and n represents an integer of 1 to 15 (Invention 3).

[0024] In the above invention (Invention 1), the acrylic polymer preferably contains a monomer having a structure represented by the above formula (2) as a monomer unit constituting the polymer (Invention 4).

[0025] In the above invention (Invention 1), the workpiece processing sheet is preferably used as at least one of a back grinding sheet, a dicing sheet, and a pickup sheet (Invention 5).

[0026] Second, the present invention provides a method of use, which is a method of use of the workpiece processing sheet (Invention 1), characterized in that it includes the following steps: a step of attaching the surface of the adhesive layer opposite to the substrate to the workpiece; a step of processing the workpiece on the workpiece processing sheet; and a step of irradiating the adhesive layer with active energy rays (Invention 6).

[0027] (III) Beneficial effects

[0028] The present invention can provide a novel workpiece processing sheet which reduces environmental load and can easily control adhesive force. DETAILED DESCRIPTION

[0029] Hereinafter, embodiments of the present invention will be described.

[0030] The workpiece processing sheet of this embodiment comprises a substrate and an adhesive layer laminated on one side of the substrate. The adhesive layer is composed of an emulsion adhesive formed of an adhesive composition containing an acrylic polymer. In addition, the acrylic polymer has a benzophenone group structure represented by the following formula (1).

[0031] [Chemical formula 3]

[0032]

[0033] In formula (1), R 1 They respectively represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.

[0034] The adhesive layer of the present embodiment is composed of an emulsion-based adhesive and therefore substantially contains no organic solvent. Therefore, the environmental load of the workpiece processing sheet of the present embodiment is reduced. Specifically, there will be no problems such as volatilization of organic solvents during manufacture and movement of residual organic solvents from the adhesive layer to the surroundings when the workpiece processing sheet is used. In addition, the adhesive layer of the present embodiment substantially contains no organic solvent, which means that the content of organic solvents (particularly volatile organic solvents such as methyl ethyl ketone, toluene, and ethyl acetate) in the adhesive layer is less than 0.3%, particularly less than 0.1%.

[0035] In addition, the adhesive layer in this embodiment contains an acrylic polymer having a benzophenone-based structure represented by the above formula (1), which can be cured well. Due to the curing, the workpiece processing sheet of this embodiment can reduce the adhesive force to the adherend, and the workpiece after processing can be easily separated.

[0036] The curing of the adhesive layer is caused by a cross-linking reaction between acrylic polymers. Specifically, the cross-linking reaction is a hydrogen abstraction reaction of hydrogen atoms present in the acrylic polymer using the ketone group in the benzophenone structure shown in the above formula (1). By carrying out this reaction at multiple sites in the acrylic polymer, a higher-order structure formed by cross-linking the acrylic polymer is formed, and as a result, the adhesive layer has a high elastic modulus.

[0037] The following formula (3) shows an example of the above-mentioned hydrogen abstraction reaction. The following formula (3) shows the reaction between any benzophenone-based structure (derived from 4-benzoylphenyl methacrylate as a constituent monomer) in an acrylic polymer and any structure containing a hydrogen atom (derived from 2-ethylhexyl acrylate as a constituent monomer) in an acrylic polymer. In particular, the ketone group in the benzophenone-based structure captures hydrogen atoms bonded to tertiary carbon atoms in other structures, and the result shows that a covalent bond is formed between the carbon atom constituting the above-mentioned ketone group and the tertiary carbon atom to which the above-mentioned hydrogen atom is bonded. In addition, the hydrogen abstraction reaction is not limited to tertiary carbon atoms, but also occurs from hydrogen atoms bonded to primary carbon atoms or secondary carbon atoms. For example, in formula (3), the possibility of hydrogen atoms other than the hydrogen atoms encircled by the dotted line being captured is not excluded.

[0038] [Chemical formula 4]

[0039]

[0040] As shown in the above formula (3), the above hydrogen abstraction reaction can be generated by irradiating a prescribed active energy ray. As examples of the active energy ray, ultraviolet rays, electron beams, etc. can be listed. From the perspective of easy and effective reaction, ultraviolet rays are preferred, particularly preferably ultraviolet rays (UV-C) with a wavelength of 200~280nm, and particularly preferably ultraviolet rays with a wavelength of 250~260nm. In this way, the above hydrogen abstraction reaction occurs by irradiation with prescribed active energy rays, and as a result, the adhesive layer is cured, so the workpiece processing sheet of the present embodiment can reduce the adhesion to the adherend at any time.

[0041] In addition, the structure that provides a hydrogen atom in the above-mentioned hydrogen abstraction reaction is not particularly limited as long as it is a hydrogen atom present in the acrylic polymer. For example, it can be a hydrogen atom bonded to any carbon atom in the acrylic polymer. However, from the perspective of the above-mentioned hydrogen abstraction reaction being easy to occur effectively, the acrylic polymer preferably has a structure shown in the following formula (2).

[0042] [Chemical formula 5]

[0043]

[0044] In formula (2), R 2 and R 3 Each of them represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and n represents an integer of 1 to 15.

[0045] 1. Constituent components of workpiece processing sheets

[0046] (1) Base material

[0047] As the substrate in the present embodiment, as long as the desired function is exerted when using the workpiece processing sheet, there is no particular limitation. In particular, the substrate is preferably a resin film with a resin-based material as the main material. As its specific examples, polyolefin films such as polyethylene film, polypropylene film, polybutylene film, polybutadiene film, polymethylpentene film, ethylene-norbornene copolymer film, and norbornene resin film can be listed; polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film; ethylene-vinyl acetate copolymer film; ethylene-(methyl) acrylic acid copolymer film, ethylene-(methyl) methyl acrylate copolymer film, and 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 films and ionomer films of the above-mentioned films can also be used. Furthermore, the substrate may be a laminated film in which a plurality of the above films are laminated. In the laminated film, the materials constituting each layer may be the same or different.

[0048] In the above, when the workpiece processing sheet of the present embodiment is used as a cutting sheet, a polyester film (particularly a polyethylene terephthalate film) is preferably used as a substrate. In addition, when the workpiece processing sheet of the present embodiment is used as a back grinding sheet, a polyurethane film is preferably used as a substrate. In addition, "(meth) acrylic acid" in this specification refers to both acrylic acid and methacrylic acid. This is also true for other similar terms. In addition, the "polymer" in this specification also includes the concept of "copolymer".

[0049] The substrate may also 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 set to a range in which the substrate exerts the desired function.

[0050] In order to improve the adhesion with the adhesive layer, the surface of the substrate on which the adhesive layer is to be laminated may be subjected to a surface treatment such as primer treatment, corona treatment, or plasma treatment.

[0051] The thickness of the substrate can be appropriately set according to the method of using the workpiece processing sheet, and is, for example, preferably 200 μm or less, particularly preferably 150 μm or less. The thickness of the substrate is preferably 10 μm or more, particularly preferably 25 μm or more.

[0052] (2)Adhesive layer

[0053] As described above, the adhesive layer in the present embodiment is composed of an emulsion-based adhesive formed of an adhesive composition containing an acrylic polymer having a benzophenone group structure represented by the following formula (1).

[0054] [Chemical formula 6]

[0055]

[0056] As mentioned above, in the above formula (1), R 1 represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. 1 In the case of the alkyl group, the number of carbon atoms is particularly preferably 1 to 14, and more preferably 1 to 10. As typical examples of the benzophenone group structure, all R 1 For the case of hydrogen atoms.

[0057] In the acrylic polymer of the present embodiment, the benzophenone-based structure may exist in any form, but from the perspective of ease of preparation of the acrylic polymer, the acrylic polymer preferably contains a monomer having a benzophenone-based structure shown in the above formula (1) as a monomer unit constituting the polymer. Examples of the monomer include 4-benzoylphenyl (meth)acrylate, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, and the like, among which 4-benzoylphenyl methacrylate is preferred. The above monomers may be used alone or in combination of two or more.

[0058] Furthermore, as another example of the monomer having the benzophenone group structure represented by the above formula (1), a monomer represented by the following formula (4) is also preferably used. The following monomers may be used alone or in combination of two or more.

[0059] [Chemical formula 7]

[0060]

[0061] In formula (4), R 4 They respectively represent an alkylene group having 1 to 18 carbon atoms, an oxygen atom or an -NH- group.

[0062] Relative to the monomeric unit constituting the acrylic copolymer, the ratio of the monomer with the benzophenone-based structure shown in the above formula (1) is preferably more than 0.1% by mass, particularly preferably more than 1% by mass, and more preferably more than 5% by mass. By making the above ratio more than 0.1% by mass, the acrylic copolymer is easy to carry out cross-linking reaction well. In addition, the above ratio is preferably below 70% by mass, particularly preferably below 50% by mass, and more preferably below 20% by mass. By making the above ratio below 15% by mass, it is easy to ensure that other monomers that contribute to adhesion, etc., the adhesive layer is easy to play a desired performance.

[0063] As described above, the acrylic copolymer of the present embodiment also preferably has a structure represented by the following formula (2).

[0064] [Chemical formula 8]

[0065]

[0066] In formula (2), R 2 and R 3 Each of them represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and n represents an integer of 1 to 15.

[0067] In R 2 In the case of the above-mentioned alkyl group, the number of carbon atoms is particularly preferably 1 to 18, and more preferably 1 to 10. Furthermore, n is particularly preferably 1 to 15, and more preferably 1 to 8.

[0068] In the acrylic polymer of this embodiment, the structure represented by the above formula (2) may exist in any form, but from the perspective of ease of preparation of the acrylic polymer, the acrylic polymer preferably contains a monomer having the structure represented by the above formula (2) as a monomer unit constituting the polymer.

[0069] Examples of monomers having a structure represented by the above formula (2) 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, etc. Among them, 2-ethylhexyl acrylate is preferred. The above monomers may be used alone or in combination of two or more.

[0070] Relative to the monomeric unit constituting the acrylic copolymer, the ratio of the monomer having the structure shown in the above formula (2) is preferably 60% by mass or more, particularly preferably 70% by mass or more, and further preferably 80% by mass or more. By making the above ratio 60% by mass or more, the acrylic copolymer is easy to carry out cross-linking reaction well. In addition, the above ratio is preferably 99.9% by mass or less, particularly preferably 99% by mass or less, and further preferably 95% by mass or less. By making the above ratio 99.9% by mass or less, it is easy to ensure that other monomers that contribute to adhesion, etc., the adhesive layer is easy to play the desired performance.

[0071] The acrylic copolymer in the present embodiment also preferably contains, as a monomer unit constituting the polymer, a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 20 carbon atoms and not belonging to a monomer having a structure represented by the above formula (2).

[0072] As the alkyl (meth)acrylate, it is particularly preferred to use an alkyl (meth)acrylate having an alkyl group with 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, etc. The alkyl (meth)acrylate may be used alone or in combination of two or more.

[0073] Relative to the monomer units constituting the acrylic copolymer, the ratio of the above-mentioned (meth) alkyl acrylate is preferably 60% by mass or more, particularly preferably 70% by mass or more, and more preferably 80% by mass or more. In addition, the above-mentioned ratio is preferably 99.9% by mass or less, particularly preferably 99% by mass or less, and more preferably 95% by mass or less. By making the ratio of the above-mentioned (meth) alkyl acrylate within the above-mentioned range, the effect brought by the above-mentioned benzophenone-based structure can be ensured, and the desired performance can be easily given to the obtained adhesive.

[0074] Furthermore, the acrylic copolymer in this embodiment also preferably contains a functional group-containing monomer as a monomer unit constituting the polymer. The 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.

[0075] Examples of the hydroxyl-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. These hydroxyl-containing monomers may be used alone or in combination of two or more.

[0076] Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. The carboxyl group-containing monomers may be used alone or in combination of two or more.

[0077] Examples of the amino group-containing monomer or substituted amino group-containing monomer include aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, etc. The amino group-containing monomer or substituted amino group-containing monomer may be used alone or in combination of two or more.

[0078] Relative to the monomer units constituting the acrylic copolymer, the ratio of the functional group-containing monomer is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and more preferably 1% by mass or more. In addition, the above ratio is preferably 30% by mass or less, particularly preferably 25% by mass or less, and more preferably 20% by mass or less. By making the ratio of the functional group-containing monomer within the above range, the effect brought by the above benzophenone-based structure can be ensured, and the desired performance can be easily given to the obtained adhesive.

[0079] The acrylic polymer of this embodiment is obtained by emulsion polymerization. As the method of this emulsion polymerization, a conventionally known method can be used, for example, it can be obtained by emulsion polymerization of an emulsion containing one or more acrylic monomers, an emulsifier and a polymerization initiator by free radical polymerization.

[0080] The emulsifier is not particularly limited, and a non-reactive emulsifier, a reactive emulsifier, or the like can be used.

[0081] As the non-reactive emulsifier, for example, anionic emulsifiers such as alkylarylsulfonates, alkyl sulfate esters, alkenyl sulfate esters, polyoxyethylene alkyl ether sulfate esters, polyoxyethylene alkenyl ether sulfate esters, polyoxyethylene alkylaryl ether sulfate esters, alkyl sulfosuccinates, alkyl sulfosuccinate derivatives, alkyl diaryl ether disulfonates, or alkyl diaryl ether disulfonate derivatives; and nonionic emulsifiers such as polyoxyethylene alkyl ethers, polyoxyethylene alkenyl ethers, polyoxyethylene alkylphenyl ethers, sorbitan higher fatty acid esters, polyoxyethylene sorbitan higher fatty acid esters, polyoxyethylene higher fatty acid esters, and glycerol higher fatty acid esters can be used.

[0082] In addition, as the reactive emulsifier, for example, "AdekariaSoap" series manufactured by Asahi Denka Kogyo Co., Ltd. and "AQUARON" series manufactured by DKS Co. Ltd. can be used. If a reactive emulsifier is used, contamination of the wafer can be further reduced.

[0083] The acrylic polymer obtained by the emulsion polymerization can be used alone as an adhesive composition, or other components can be added thereto to form an adhesive composition. When other components are added, there is no limitation on the examples of such components as long as the above-mentioned effects of the workpiece processing sheet of the embodiment are not impaired, and for example, a crosslinking agent, an active energy ray curable compound, a photopolymerization initiator, a silane coupling agent, an antistatic agent, a tackifier, an antioxidant, a light stabilizer, a softener, a filler, a refractive index modifier, etc. can be added.

[0084] However, from the perspective of suppressing the generation of particles on the adherend surface after the workpiece processing sheet is peeled off from the adherend, the adhesive composition preferably does not contain low-molecular weight components, and particularly preferably does not contain low-molecular weight components as active energy ray curable compounds. In addition, the so-called low-molecular weight components herein refer to, for example, components with a molecular weight of less than 1000, and particularly refer to components with a molecular weight of less than 800.

[0085] The thickness of the adhesive layer of this embodiment is preferably 1 μm or more, particularly preferably 3 μm or more, and more preferably 5 μm or more. By making the thickness of the adhesive layer 1 μm or more, the workpiece processing sheet is easy to exert good adhesion, for example, it is easy to suppress chip scattering. In addition, the thickness is preferably 60 μm or less, particularly preferably 30 μm or less, and more preferably 20 μm or less. By making the thickness of the adhesive layer 60 μm or less, it is easy to better pick up the workpiece.

[0086] (3) Peel sheet

[0087] 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”) before being attached to the workpiece for the purpose of protecting the surface.

[0088] The structure of the release sheet is arbitrary, and for example, a plastic film subjected 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 and polyethylene. As the release agent, silicone-based, fluorine-based, long-chain alkyl, and rubber-based can be used, among which silicone-based is preferred because it is inexpensive and can provide stable performance.

[0089] The thickness of the release sheet is not particularly limited, and may be, for example, 16 μm or more and 250 μm or less.

[0090] (4) Others

[0091] In the workpiece processing sheet of the present embodiment, an adhesive layer can also be stacked on the surface of the adhesive layer on the opposite side to the substrate. In this case, the workpiece processing sheet of the present embodiment can be used as a cutting chip. In this sheet, a workpiece is attached to the surface of the adhesive layer on the opposite side to the adhesive layer, and the adhesive layer is cut together with the workpiece, thereby obtaining a chip stacked with a singulated adhesive layer. The chip can be easily fixed to the object carrying the chip through the singulated adhesive layer. 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.

[0092] In addition, in the workpiece processing sheet of the present embodiment, a protective film forming layer can also be laminated 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 and cutting sheet. In such a sheet, the workpiece is attached to the surface of the protective film forming layer opposite to the adhesive layer, and the protective film forming layer is cut together with the workpiece, thereby obtaining a chip laminated with a singulated protective film forming layer. As the workpiece, it is preferred to use a workpiece with a circuit formed on one side. In this case, the protective film forming layer is usually laminated on the surface opposite to the surface with the circuit formed. By curing the singulated protective film forming layer at a specified time, a protective film with sufficient durability can be formed on the chip. The protective film forming layer is preferably composed of an uncured curable adhesive.

[0093] 2. Method for manufacturing sheet for workpiece processing

[0094] 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.

[0095] The adhesive layer can be laminated on the single-sided side of the substrate by a known method. For example, the adhesive layer formed on the release sheet is preferably transferred to the single-sided side of the substrate. In this case, for example, a coating liquid containing an adhesive composition constituting the adhesive layer is prepared, and a die coater, a curtain coater, a spray coater, a slit coater, a blade coater, an applicator, etc. are used to apply the coating liquid on the peeling-processed surface of the release sheet (hereinafter sometimes referred to as "peeling surface") 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 properties are not particularly limited, and the components used to form the adhesive layer are sometimes contained as a solute, and sometimes as a dispersion. The release sheet in the laminate can be peeled off as a process 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.

[0096] Alternatively, the adhesive layer may be directly formed on the substrate instead of being transferred to one side of the substrate by forming the adhesive layer formed on the release sheet as described above. In this case, the coating liquid for forming the adhesive layer is applied to one side of the substrate to form a coating film, and the coating film is dried to form the adhesive layer.

[0097] 3. How to use the workpiece processing sheet

[0098] The workpiece processing sheet of the present embodiment can be used for processing workpieces such as semiconductor wafers. That is, after the adhesive surface of the workpiece processing sheet of the present embodiment is attached to the workpiece, the workpiece can be processed on the workpiece processing sheet. According to the processing, the workpiece processing sheet of the present embodiment is used as a back grinding sheet, a cutting sheet, an expansion sheet (expandsheet), a pickup sheet, etc. As examples of workpieces, semiconductor components such as semiconductor wafers and semiconductor packages; glass components such as glass plates can be listed.

[0099] As described above, the workpiece processing sheet of this embodiment can effectively reduce the adhesion to the adherend by curing the adhesive layer by irradiating a predetermined active energy ray. Therefore, the workpiece processing sheet of this embodiment is preferably used as at least one of a back grinding sheet, a cutting sheet, and a pickup sheet.

[0100] As an example of a preferred method of using the workpiece processing sheet of the present embodiment, there can be listed a method of use comprising the following steps: a step of attaching the surface of the adhesive layer opposite to the substrate to the workpiece; a step of processing the workpiece on the workpiece processing sheet; and a step of irradiating the adhesive layer with active energy rays.

[0101] In the above-mentioned attaching step, as long as the adhesive surface of the workpiece processing sheet of this embodiment is attached to the workpiece, the specific method is not limited.

[0102] The subsequent processing steps are performed according to the type of processing, and as the method, a conventionally known method can be used. For example, in the case of cutting, a plurality of semiconductor chips can be obtained by cutting the workpiece on the workpiece processing sheet using a cutting device. The type of cutting here is not particularly limited, and for example, it can also be blade cutting, laser cutting, stealth cutting, etc.

[0103] The irradiation with active energy rays in the irradiation step can be performed by a conventionally known method. The types of active energy rays and the like are as described above.

[0104] In addition, when the workpiece processing sheet of this embodiment has the above-mentioned adhesive layer, the workpiece processing sheet can be used as a dicing wafer. Further, when the workpiece processing sheet of this embodiment has the above-mentioned protective film forming layer, the workpiece processing sheet can be used as a protective film forming and dicing sheet.

[0105] 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 is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[0106] For example, another layer may be provided between the substrate and the adhesive layer, or on the surface of the substrate opposite to the adhesive layer.

[0107] Example

[0108] Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

[0109] [Example 1]

[0110] (1) Preparation of adhesive composition

[0111] In a four-necked flask equipped with a nitrogen inlet tube, a thermometer, a reflux condenser and a stirring device, 20 parts by mass of 2-ethylhexyl acrylate, 65 parts by mass of butyl acrylate, 4 parts by mass of methyl methacrylate, 10 parts by mass of 4-benzoylphenyl methacrylate, 1 part by mass of acrylic acid, 1 part by mass of polyoxyethylene alkyl ether sulfate as an emulsifier, and 150 parts by mass of distilled water were added, and the mixture was stirred thoroughly and heated to 70° C. Then, 0.3 parts by mass of ammonium persulfate as a polymerization initiator was added, and emulsion polymerization was carried out at 80° C. for 3 hours. After stirring, the obtained product was filtered (mesh #200), and the pH was adjusted to 11-14 with aqueous ammonia to prepare an acrylic polymer as an emulsion polymer.

[0112] (2) Production of cutting discs

[0113] While adjusting the gap with an applicator, the coating liquid of the adhesive composition prepared in step (1) was applied to the release surface of a release sheet (manufactured by LINTEC Corporation, product name "SP-PET381031") having a thickness of 38 μm and a silicone release layer formed on one side of a polyethylene terephthalate film. The coating film thus obtained was dried at 100° C. for 2 minutes to form an adhesive layer having a thickness of 20 μm, thereby obtaining a laminate of the adhesive layer and the release sheet.

[0114] The surface of the laminate obtained as described above on the adhesive layer side was laminated to the easy-adhesion treated surface of a polyethylene terephthalate film (manufactured by Mitsubishi Chemical Corporation, product name "DIAFOIL", thickness: 100 μm) as a substrate to obtain a workpiece processing sheet having a structure of a release sheet / adhesive layer (20 μm) / substrate. In addition, the workpiece processing sheet was used as a dicing sheet in Test Examples 1 to 3 described later.

[0115] (3) Production of back grinding sheet

[0116] A resin composition prepared by mixing 50 parts by weight of a urethane acrylate oligomer (weight average molecular weight (Mw): about 5000), 50 parts by weight of isobornyl acrylate, and 2.0 parts by weight of 1-hydroxycyclohexyl phenyl ketone (manufactured by BASF, product name "Omnirad 184") as a photopolymerization initiator was applied to the release surface of the release sheet by a fountain die method. The thus formed coating film was irradiated with ultraviolet rays (250 mJ / cm 2 ) was cured to obtain a resin sheet with a thickness of 160 μm. This resin sheet was used as a substrate.

[0117] In addition, while adjusting the spacing with an applicator, the coating liquid of the adhesive composition prepared in step (1) was applied to the release surface of a release sheet (manufactured by LINTEC Corporation, product name "SP-PET3811 (S)") having a thickness of 38 μm and a silicone release layer formed on one side of a polyethylene terephthalate film. The coating film thus obtained was dried at 100° C. for 2 minutes to form an adhesive layer having a thickness of 20 μm, thereby obtaining a laminate of the adhesive layer and the release sheet.

[0118] The adhesive layer side surface of the laminate obtained as described above was bonded to one side of the substrate obtained as described above to obtain a workpiece processing sheet having a structure of release sheet / adhesive layer (20 μm) / substrate. This workpiece processing sheet was used as a back grinding sheet in Test Example 4 described below.

[0119] [Example 2]

[0120] A workpiece processing sheet (dicing sheet and back grinding sheet) was produced in the same manner as in Example 1 except that the amount of n-butyl acrylate used was changed to 74.9 parts by mass and the amount of 4-benzoylphenyl methacrylate used was changed to 0.1 parts by mass.

[0121] [Comparative Example 1]

[0122] 80 parts by mass of 2-ethylhexyl acrylate and 20 parts by mass of 2-hydroxyethyl acrylate were polymerized by solution polymerization to obtain an acrylic copolymer. Then, isocyanoethyl methacrylate (MOI) was added in an amount corresponding to 80 mol% of 2-hydroxyethyl acrylate constituting the acrylic copolymer. Then, the mixture was reacted at 60° C. for 48 hours to obtain an acrylic polymer having an active energy ray-curable group introduced into the side chain.

[0123] 100 parts by mass (solid content conversion, the same applies hereinafter) of the obtained acrylic polymer and 3 parts by mass of 1-hydroxycyclohexyl phenyl ketone (manufactured by BASF, product name "Omnirad 184") as a photopolymerization initiator were mixed in a solvent to obtain a coating liquid of an adhesive composition.

[0124] Except having used the said coating liquid as the coating liquid of the adhesive composition of Comparative Example 1, it carried out similarly to Example 1, and produced the sheet|seat for workpiece|work processing (dicing sheet and back grinding sheet).

[0125] [Comparative Example 2]

[0126] Workpiece processing sheets (dicing sheets and back grinding sheets) were produced in the same manner as in Example 1 except that the monomer composition in preparing the acrylic polymer was changed to 83 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of methyl methacrylate, 3 parts by mass of methyl acrylate, and 1 part by mass of acrylic acid.

[0127] [Test Example 1] (Evaluation of residual organic solvent)

[0128] After cutting the workpiece processing sheet (cutting sheet) made in the embodiment and the comparative example into a size of 10mm×50mm, peel off the peeling sheet, and use the laminate of the adhesive layer and the substrate thus obtained as the measurement sample. The measurement sample is sealed in a measurement bottle, heated at 120°C for 30 minutes, and the generated gas is introduced into a gas chromatograph mass spectrometer (manufactured by Shimadzu Corporation, product name "GCMS-QP2010") to confirm the presence or absence of peaks equivalent to methyl ethyl ketone, toluene and ethyl acetate. Then, based on the following benchmarks, evaluate the presence or absence of residual organic solvents. The results are shown in Table 1.

[0129] ○: No peak appears.

[0130] ×: At least one peak appears.

[0131] [Test Example 2] (Evaluation of haze of wafer after peeling)

[0132] The workpiece processing sheets (dicing sheets) prepared in Examples and Comparative Examples were cut into strips with a width of 25 mm, the release sheet was peeled off, and the exposed surface of the adhesive layer was attached to the mirror surface of a 6-inch silicon wafer with a thickness of 625 μm.

[0133] Next, the substrate-side surface of the workpiece processing sheet was irradiated with ultraviolet light (UV) (illuminance: 230 mW / cm 2 , light intensity: 190mJ / cm 2 ) to solidify the adhesive layer.

[0134] Then, the workpiece processing sheet was peeled off from the wafer at a speed of 300 mm / min. Then, the portion of the wafer to which the workpiece processing sheet was once attached was visually confirmed to be blurry. Then, based on the following criteria, the peeled wafer was evaluated to be blurry. The results are shown in Table 1.

[0135] ○: No blurring.

[0136] ×: There is blur.

[0137] [Test Example 3] (Evaluation of cutting properties)

[0138] The peeling sheet was peeled off from the workpiece processing sheet (dicing sheet) prepared in the examples and comparative examples, and the exposed surface of the adhesive layer was attached to the mirror surface of an 8-inch silicon wafer with a thickness of 150 μm and a dicing ring frame. Then, the workpiece processing sheet was cut according to the outer diameter of the ring frame.

[0139] Next, dicing was performed using a dicing device (manufactured by DISCO Corporation, product name "DFD-6362") under the following dicing conditions.

[0140] <Cutting conditions>

[0141] Cutting device: DFD-6362 manufactured by DISCO Corporation

[0142] Blade: NBC-2H 2050 27HECC manufactured by DISCO Corporation

[0143] Blade speed: 30000rpm

[0144] Cutting speed: 50mm / sec

[0145] ·Substrate cutting depth: 20μm

[0146] Chip size: 10mm×10mm

[0147] After the dicing was completed, it was confirmed whether the chips had fallen off the workpiece processing sheet (whether there was chip scattering). Next, the dicing properties were evaluated based on the following criteria. The results are shown in Table 1.

[0148] ○: No chip scattering.

[0149] ×: Chips are scattered.

[0150] [Test Example 4] (Evaluation of back surface polishing properties)

[0151] The release sheet was peeled off from the workpiece processing sheet (back grinding sheet) prepared in the examples and comparative examples, and the exposed surface of the adhesive layer was attached to the integrated circuit side of a semiconductor silicon wafer (6 inches in diameter, 625 μm thick) having an integrated circuit formed on one side.

[0152] Next, the surface of the semiconductor silicon wafer opposite to the surface to which the workpiece processing sheet was attached was back-ground using a grinder (manufactured by DISCO Corporation, product name "Back Grinder DFG8540") until the thickness of the semiconductor silicon wafer reached 350 μm.

[0153] The above-mentioned backside grinding was performed twice independently, and the thickness of the semiconductor silicon wafer was measured twice. Next, the backside grinding property was evaluated based on the following criteria. The results are shown in Table 1.

[0154] ○: The predetermined thickness (350 μm) was achieved in both attempts.

[0155] ×: The predetermined thickness (350 μm) was not reached at least once.

[0156] In addition, the details of the abbreviations and the like described in Table 1 are as follows.

[0157] 2EHA: 2-Ethylhexyl acrylate

[0158] BA: n-butyl acrylate

[0159] MMA: Methyl Methacrylate

[0160] AA: Acrylic acid

[0161] 4MBP: 4-Benzoylphenyl methacrylate

[0162] HEA: 2-Hydroxyethyl Acrylate

[0163] MOI: Isocyanoethyl methacrylate

[0164] MA: Methyl acrylate

[0165] DPHA: Dipentaerythritol hexaacrylate

[0166] [Table 1]

[0167]

[0168] As shown in Table 1, the workpiece processing sheet obtained in the embodiment does not detect residual organic solvent, so the environmental load can be effectively reduced. In addition, the workpiece processing sheet obtained in the embodiment does not cause residual blur in the wafer after peeling, that is, it can be seen that the generation of particles caused by low molecular components in the workpiece processing sheet (especially in the adhesive layer) is well suppressed. Further, it can be seen that the workpiece processing sheet obtained in the embodiment has excellent cutting and back grinding properties, and can exert sufficient adhesion to the adherend.

[0169] Industrial Applicability

[0170] 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 a single sheet side of the base material, characterized in that: The adhesive layer is composed of an emulsion adhesive formed of an adhesive composition containing an acrylic polymer. The acrylic polymer has a benzophenone group structure represented by the following formula (1): [Chemical formula 1] In formula (1), R 1 They respectively represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.

2. The workpiece processing sheet according to claim 1, characterized in that: The acrylic polymer contains a monomer having a benzophenone group structure represented by the formula (1) as a monomer unit constituting the polymer.

3. The workpiece processing sheet according to claim 1, characterized in that: The acrylic polymer has a structure represented by the following formula (2): [Chemical formula 2] In formula (2), R 2 and R 3 Each of them represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and n represents an integer of 1 to 15.

4. The workpiece processing sheet according to claim 3, characterized in that: The acrylic polymer contains a monomer having a structure represented by the formula (2) as a monomer unit constituting the polymer.

5. The workpiece processing sheet according to claim 1, characterized in that: The workpiece processing sheet is used as at least one of a back grinding sheet, a cutting sheet, and a pickup sheet.

6. A method for using a workpiece processing sheet, which is the method for using the workpiece processing sheet according to claim 1, characterized in that: The process includes the following steps: A step of attaching the surface of the adhesive layer opposite to the substrate to a workpiece; a processing step of processing the workpiece on the workpiece processing sheet; and The adhesive layer is irradiated with an active energy ray.

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