Workpiece processing sheet

Abstract

To provide a workpiece processing sheet which can suppress generation of a cut piece in dicing and suppress unevenness of adhesive force.SOLUTION: There is provided a workpiece processing sheet comprising: a substrate; and an adhesive layer laminated on one surface side on the substrate. The substrate is subjected to electron beam (EB) radiation processing, and the adhesive layer is constituted by an adhesive formed of an adhesive composition including a component having a benzo phenyl structure expressed by the following formula (1). (In formula (1), R1's express a hydrogen atom, or an alkyl group having C1-C18.) The content of a component having a polymerizable carbon-carbon double bond in the adhesive composition is 0.1 mass% or lower in the workpiece processing sheet.SELECTED DRAWING: None

Description

[Technical Field]

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

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

[0003] In the above-mentioned workpiece processing sheet, the adhesive layer may be made of an adhesive having active energy ray curability. In this case, by irradiating the adhesive layer with active energy rays, the adhesive strength of the adhesive layer to the workpiece can be reduced, thereby making it easier to separate (e.g., pick up) the workpiece from the adhesive sheet.

[0004] Patent Document 1 discloses an example of a workpiece processing sheet having an adhesive layer made of an adhesive having active energy ray curability. In particular, the Examples section of Patent Document 1 discloses a workpiece processing sheet having an adhesive layer made of an acrylic adhesive containing an active energy ray polymerizable compound having a polymerizable carbon-carbon double bond. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-033059 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when a semiconductor wafer or the like is diced using a workpiece processing sheet, there is a problem that thread-like scraps (cutting chips) are generated. In order to suppress the generation of such chips, a treatment of irradiating an electron beam (EB) onto the substrate constituting the workpiece processing sheet has been performed. A workpiece processing sheet formed by laminating an adhesive layer on a substrate irradiated with an electron beam can effectively suppress the generation of chips during dicing.

[0007] On the other hand, the inventors discovered that in a work processing sheet in which an adhesive layer composed of an active energy ray polymerizable adhesive containing a polymerizable carbon-carbon double bond is laminated onto a substrate that has been subjected to electron beam irradiation treatment, a difference in adhesive strength is likely to occur between the central region and the peripheral region of the adhesive layer.

[0008] The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a workpiece processing sheet that can suppress the generation of cutting chips during dicing while also being less likely to cause uneven adhesive strength. [Means for solving the problem]

[0009] In order to achieve the above object, first, the present invention provides a workpiece processing sheet including a substrate and an adhesive layer laminated on one side of the substrate, wherein the substrate is irradiated with an electron beam (EB), and the adhesive layer has a structure represented by the following formula (1): [ka] (In formula (1), R1 represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.) The present invention provides a workpiece processing sheet, which is composed of an adhesive formed from an adhesive composition containing a component having a benzophenyl structure represented by the following formula: wherein the content of a component having a polymerizable carbon-carbon double bond in the adhesive composition is 0.1 mass % or less (Invention 1).

[0010] In the workpiece processing sheet according to the above invention (Invention 1), the substrate is subjected to electron beam irradiation treatment, which effectively suppresses the generation of chips when used in dicing. Furthermore, the adhesive constituting the adhesive layer is formed from an adhesive composition containing the above-mentioned component having a benzophenyl structure, which makes it less likely that a difference in adhesive strength will occur between the central region and the peripheral region.

[0011] In the above invention (Invention 1), the pressure-sensitive adhesive composition contains an acrylic polymer, and the acrylic polymer preferably contains a monomer having a benzophenyl structure represented by the formula (1) as a monomer unit constituting the polymer (Invention 2).

[0012] In the above inventions (Inventions 1 and 2), the pressure-sensitive adhesive layer is a compound represented by the following formula (2): [ka] (In formula (2), R 2 and R 3 each represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and n represents an integer of 1 to 15. It is preferable that the compound has a structure represented by the following formula (Invention 3).

[0013] In the above invention (Invention 3), the pressure-sensitive adhesive composition contains an acrylic polymer, and the acrylic polymer preferably contains a monomer having a structure represented by the formula (2) as a monomer unit constituting the polymer (Invention 4). [Effects of the Invention]

[0014] The workpiece processing sheet according to the present invention can suppress the generation of chips during dicing, while also being less likely to have uneven adhesive strength. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described. The workpiece processing sheet according to this embodiment includes a substrate and an adhesive layer laminated on one side of the substrate.

[0016] In the workpiece processing sheet according to this embodiment, the substrate is subjected to electron beam (EB) irradiation treatment. By including this substrate, the workpiece processing sheet according to this embodiment can effectively suppress the generation of chips even when used for dicing with a rotating circular blade.

[0017] Generally, when dicing with a rotating circular blade, not only is a workpiece such as a semiconductor wafer cut, but a portion of the workpiece processing sheet is also cut. During dicing, the substrate is softened by the frictional heat generated during dicing, and then the rotating circular blade contacts the substrate, applying a pulling force to the cut portion of the substrate, stretching it as it is scraped off. As a result, thread-like shavings are generated.

[0018] On the other hand, in the workpiece processing sheet according to this embodiment, the substrate is irradiated with electron beams, which causes covalent crosslinking within the substrate, and as a result, it is presumed that the generation of the above-mentioned cutting chips is suppressed.

[0019] Furthermore, in the workpiece processing sheet according to this embodiment, the adhesive layer has a structure represented by the following formula (1): [ka] (In formula (1), R1 represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.) The adhesive is formed from an adhesive composition containing a component having a benzophenyl structure represented by the formula:

[0020] In the workpiece processing sheet of this embodiment, the adhesive layer is made of the above-mentioned adhesive, so that the adhesive layer can be hardened by an external stimulus, thereby reducing the adhesive strength to the workpiece.

[0021] The hardening of the pressure-sensitive adhesive layer described above is caused by a crosslinking reaction between components having the benzophenyl structure (for example, an acrylic polymer as described below). Specifically, this crosslinking reaction is a hydrogen abstraction reaction from a hydrogen atom by a ketone group in the benzophenyl structure represented by the above formula (1). As this reaction progresses multiple times, a higher-order structure is formed in which the components having the benzophenyl structure are crosslinked, resulting in the pressure-sensitive adhesive layer having a high elastic modulus.

[0022] The following formula (3) shows an example of the hydrogen abstraction reaction described above. In particular, formula (3) shows the reaction occurring between any benzophenyl structure in the acrylic polymer (derived from 4-benzoylphenyl methacrylate as a constituent monomer) and any hydrogen-containing structure in the acrylic polymer (derived from 2-ethylhexyl acrylate as a constituent monomer). As shown here, the ketone group in the benzophenyl structure abstracts a hydrogen atom bonded to a tertiary carbon atom in the other structure, resulting in the formation of a covalent bond between the carbon atom constituting the ketone group and the tertiary carbon atom to which the hydrogen atom was bonded. This hydrogen abstraction reaction is not limited to tertiary carbon atoms, but can also occur from hydrogen atoms bonded to primary or secondary carbon atoms. For example, formula (3) does not exclude the possibility of abstracting hydrogen atoms other than those enclosed by the dashed line. [ka]

[0023] As shown in the above formula (3), the above-mentioned hydrogen abstraction reaction can be induced by irradiation with a predetermined active energy ray. Examples of such active energy ray include ultraviolet light and electron beams. However, from the viewpoint of easily inducing the reaction effectively, ultraviolet light is preferred, particularly ultraviolet light (UV-C) having a wavelength of 200 to 280 nm, and especially ultraviolet light having a wavelength of 250 to 260 nm. In this way, the above-mentioned hydrogen abstraction reaction occurs upon irradiation with a predetermined active energy ray, and as a result, the adhesive layer hardens. Therefore, the workpiece processing sheet according to this embodiment can reduce its adhesive strength to an adherend at any time.

[0024] The structure that provides the hydrogen atom in the hydrogen abstraction reaction is not particularly limited as long as it is a hydrogen atom present in the pressure-sensitive adhesive layer. However, from the viewpoint of facilitating efficient hydrogen abstraction reaction, the pressure-sensitive adhesive layer may preferably have a structure represented by the following formula (2): [ka] (In formula (2), R 2 and R 3 each represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and n represents an integer of 1 to 15. It is also preferred that the compound has a structure represented by the following formula:

[0025] Furthermore, since the adhesive layer of the workpiece processing sheet according to this embodiment is composed of an adhesive having a benzophenyl structure, unevenness in adhesive strength (particularly, a difference in adhesive strength between the central region and the peripheral region of the adhesive layer) is unlikely to occur, even though the substrate has been subjected to electron beam irradiation treatment as described above.

[0026] Conventional workpiece processing sheets are constructed by laminating a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive containing a polymerizable carbon-carbon double bond onto a substrate treated with electron beam irradiation. The inventors have confirmed that such workpiece processing sheets are prone to differences in adhesive strength between the central and peripheral regions of the pressure-sensitive adhesive layer. They have then discovered that this uneven adhesive strength is caused by radicals remaining on the substrate treated with electron beam irradiation. It is presumed that radicals are more likely to remain in the central region of a substrate treated with electron beam irradiation than in the peripheral region, which is in greater contact with the surroundings. When a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive containing a polymerizable carbon-carbon double bond is laminated on such a substrate, the radicals remaining on the substrate react with the polymerizable carbon-carbon double bonds present in the pressure-sensitive adhesive layer, slightly promoting a polymerization reaction. In particular, as described above, radicals tend to remain in the center of the substrate, leading to a greater polymerization reaction in the center of the pressure-sensitive adhesive layer. As a result, it is presumed that the adhesive strength is lower in the central region than in the peripheral region of the pressure-sensitive adhesive layer.

[0027] In contrast, the adhesive layer of the workpiece processing sheet according to this embodiment is composed of an adhesive containing the above-mentioned benzophenyl structure, rather than an adhesive containing a polymerizable carbon-carbon double bond, and the adhesive hardens through the above-mentioned hydrogen abstraction reaction, so it is essentially unaffected by radicals remaining in the substrate, thereby suppressing the occurrence of unevenness in the adhesive layer.

[0028] In the workpiece processing sheet according to this embodiment, the content of the component having a polymerizable carbon-carbon double bond in the pressure-sensitive adhesive composition is 0.1% by mass or less. This makes the pressure-sensitive adhesive layer less susceptible to the effects of radicals remaining on the substrate, further suppressing the occurrence of unevenness in the pressure-sensitive adhesive layer. From this perspective, the content of the component having a polymerizable carbon-carbon double bond is preferably 0.05% by mass or less, and particularly preferably 0.01% by mass or less.

[0029] The polymerizable carbon-carbon double bond referred to here includes a double bond contained in a (meth)acryloyl group, etc. The presence of a component having a polymerizable carbon-carbon double bond in the pressure-sensitive adhesive composition may include the presence of an acrylic polymer having a moiety having a polymerizable carbon-carbon double bond as a side chain, the presence of a low molecular weight compound (e.g., a polyfunctional acrylate) having a polymerizable carbon-carbon double bond, or the presence of an acrylic monomer that would constitute the acrylic polymer remaining in the pressure-sensitive adhesive composition.

[0030] 1. Components of workpiece processing sheets (1) Base material The substrate in this embodiment is not particularly limited as long as it has been subjected to electron beam irradiation treatment. From the viewpoint that covalent bonds are easily formed inside the substrate by electron beam irradiation treatment, the substrate is preferably a resin film.

[0031] Examples of the resin film include ethylene copolymer films such as ethylene-(meth)acrylic acid copolymer films, ethylene-methyl(meth)acrylate copolymer films, and other ethylene-(meth)acrylic acid ester copolymer films; polyolefin films such as polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, ethylene-norbornene copolymer films, and norbornene resin films; polyester films such as polyethylene terephthalate films, polybutylene terephthalate films, and polyethylene naphthalate; ethylene-vinyl acetate copolymer films; polyvinyl chloride films such as polyvinyl chloride films and vinyl chloride copolymer films; (meth)acrylic acid ester copolymer films; polyurethane films; polyimide films; polystyrene films; polycarbonate films; and fluororesin films. Modified films such as crosslinked films and ionomer films of these films may also be used. The substrate may also be a laminate film formed by laminating multiple of the above-mentioned films. In this laminate film, the materials constituting each layer may be the same or different.

[0032] Among the above resin films, from the viewpoint of easily suppressing the generation of chips by electron beam irradiation treatment, it is preferable to use at least one of an ethylene-based copolymer film, a polyethylene film, and a polypropylene film, and it is particularly preferable to use an ethylene-based copolymer film, and among these, it is particularly preferable to use an ethylene-methacrylic acid copolymer film.

[0033] The substrate may contain various additives such as a flame retardant, a plasticizer, an antistatic agent, a lubricant, an antioxidant, a colorant, an infrared absorber, an ultraviolet absorber, an ion scavenger, etc. The content of these additives is not particularly limited, but is preferably set within a range in which the substrate exhibits the desired function.

[0034] In this specification, the term "electron beam" refers to a free electron beam, i.e., a cathode ray. To irradiate a substrate with an electron beam, an electron beam source (including any type, such as high energy, low energy, or scanning) is typically used, and the film is passed under the generated electron beam under specified conditions. The type of electron beam source is not particularly limited, and various electron beam accelerators, such as Cockcroft-Walton type, Van de Graaf type, resonant transformer type, insulating core transformer type, linear type, dynamitron type, and high frequency type, can be used. The electron beam may be a beta ray (i.e., an electron beam generated by radioactive decay of an atomic nucleus).

[0035] Typically, electron beam irradiation is carried out by irradiating the electron beam from at least one main surface of the substrate. The electron beam irradiation can be carried out by appropriately adjusting conditions such as the cumulative irradiation dose, cumulative irradiation time, and irradiation dose per irradiation. Among these conditions, the cumulative irradiation dose of the electron beam is preferably 10 kGy or more, more preferably 100 kGy or more, particularly preferably 200 kGy or more, and even more preferably 300 kGy or more. Furthermore, the cumulative irradiation dose of the electron beam is preferably 900 kGy or less, particularly preferably 600 kGy or less, and even more preferably 300 kGy or less. By keeping the cumulative irradiation dose within the above range, it becomes easier to effectively suppress the generation of chips.

[0036] The substrate may be subjected to a treatment other than electron beam irradiation treatment. For example, the surface of the substrate on which the pressure-sensitive adhesive layer is to be laminated may be subjected to a surface treatment such as a primer treatment, a corona treatment, or a plasma treatment in order to improve adhesion to the pressure-sensitive adhesive layer.

[0037] The thickness of the substrate can be set appropriately depending on the method for using the workpiece processing sheet, but is preferably 200 μm or less, particularly 150 μm or less, and is preferably 10 μm or more, particularly 25 μm or more.

[0038] (2) Adhesive layer As described above, the pressure-sensitive adhesive layer in this embodiment is a polymerizable compound represented by the following formula (1): [ka] The adhesive is formed from an adhesive composition containing a component having a benzophenyl structure represented by the formula:

[0039] In the above formula (1), as described above, R 1 R represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. 1 When R is the alkyl group, the number of carbon atoms is particularly preferably 1 to 14, and more preferably 1 to 10. A typical example of the benzophenyl structure is a benzophenyl structure in which all R 1 is a hydrogen atom.

[0040] Examples of the pressure-sensitive adhesive include acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives, silicone pressure-sensitive adhesives, urethane pressure-sensitive adhesives, polyester pressure-sensitive adhesives, polyvinyl ether pressure-sensitive adhesives, etc. Among these, it is preferable to use acrylic pressure-sensitive adhesives because they can easily exert the desired adhesive strength.

[0041] When the pressure-sensitive adhesive layer in this embodiment is composed of an acrylic pressure-sensitive adhesive, the pressure-sensitive adhesive is preferably formed from a pressure-sensitive adhesive composition containing an acrylic polymer. In the pressure-sensitive adhesive layer in this embodiment, the benzophenyl structure may be present in any form, but from the viewpoint of ease of preparation of the acrylic polymer, it is preferred that the acrylic polymer contains a monomer having a benzophenyl structure represented by the above formula (1) as a monomer unit constituting the polymer.

[0042] 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, etc., and among these, 4-benzoylphenyl methacrylate is preferred. These may be used alone or in combination of two or more.

[0043] Furthermore, another example of the monomer having a benzophenyl structure represented by the above formula (1) is a monomer represented by the following formula (4): [ka] (In formula (4), R 4 each represents an alkylene group having 1 to 18 carbon atoms, an oxygen atom, or an -NH- group. It is also preferable to use a monomer represented by the following formula: These may be used alone or in combination of two or more.

[0044] The ratio of the monomer having the structure represented by the above formula (1) to the monomer units constituting the acrylic copolymer is preferably 0.1% by mass or more, particularly preferably 1% by mass or more, and even more preferably 5% by mass or more. When the ratio is 0.1% by mass or more, the acrylic copolymer is more likely to efficiently undergo the hydrogenation reaction described above. Furthermore, the ratio is preferably 70% by mass or less, particularly preferably 50% by mass or less, and even more preferably 15% by mass or less. When the ratio is 70% by mass or less, it is easier to secure other monomers that contribute to adhesion, etc., and the pressure-sensitive adhesive layer is more likely to exhibit the desired performance.

[0045] As described above, the pressure-sensitive adhesive layer in the present embodiment comprises a compound represented by the following formula (2): [ka] (In formula (2), R 2 and R 3 each represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and n represents an integer of 1 to 15. It is also preferred that the compound has a structure represented by the formula: 2 When is the alkyl group, the number of carbon atoms therein 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.

[0046] When the pressure-sensitive adhesive layer in the present embodiment is formed from a pressure-sensitive adhesive composition containing an acrylic polymer, the acrylic polymer preferably contains, as a monomer unit constituting the polymer, a monomer having a structure represented by the above formula (2).

[0047] Examples of monomers having the 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., and among these, 2-ethylhexyl acrylate is preferred. These may be used alone or in combination of two or more.

[0048] The ratio of the monomer having the structure represented by formula (2) to the monomer units constituting the acrylic copolymer is preferably 60% by mass or more, particularly preferably 70% by mass or more, and even more preferably 80% by mass or more. A ratio of 60% by mass or more facilitates efficient hydrogenation reaction in the acrylic copolymer. Furthermore, the ratio is preferably 99.9% by mass or less, particularly preferably 99% by mass or less, and even more preferably 95% by mass or less. A ratio of 99.9% by mass or less facilitates the availability of other monomers that contribute to adhesion, etc., and facilitates the pressure-sensitive adhesive layer to exhibit the desired performance.

[0049] It is also preferable that the acrylic copolymer contains, as a monomer unit constituting the polymer, an alkyl (meth)acrylate having an alkyl group with 1 to 20 carbon atoms, which does not fall under the category of monomers having the structure represented by the above formula (2).

[0050] As the alkyl(meth)acrylate, alkyl(meth)acrylates in which the alkyl group has 1 to 18 carbon atoms, such as methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, etc., are particularly preferred. These may be used alone or in combination of two or more.

[0051] The proportion of the alkyl (meth)acrylate relative to the monomer units constituting the acrylic copolymer is preferably 60% by mass or more, particularly preferably 70% by mass or more, and even more preferably 80% by mass or more. Furthermore, the proportion is preferably 99.9% by mass or less, particularly preferably 99% by mass or less, and even more preferably 95% by mass or less. By ensuring the effect of the benzophenyl structure described above, the desired performance can be easily imparted to the resulting pressure-sensitive adhesive.

[0052] Furthermore, the acrylic copolymer of the present embodiment 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 hydroxy group, a carboxy group, an amino group, a substituted amino group, or an epoxy group in the molecule.

[0053] Examples of hydroxy group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, and these may be used alone or in combination of two or more.

[0054] Examples of the carboxy group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, etc. These may be used alone or in combination of two or more.

[0055] 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.

[0056] The ratio of the functional group-containing monomer to the monomer units constituting the acrylic copolymer is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and even more preferably 1% by mass or more. Furthermore, the ratio is preferably 30% by mass or less, particularly preferably 25% by mass or less, and even more preferably 20% by mass or less. By ensuring the effect of the benzophenyl structure described above, the ratio of the functional group-containing monomer within the above-mentioned range makes it easier to impart the desired performance to the resulting adhesive.

[0057] The acrylic polymer of the present embodiment can be obtained by polymerizing the above-mentioned monomers by a conventional method, such as solution polymerization, emulsion polymerization, suspension polymerization, bulk polymerization, or aqueous solution polymerization.

[0058] The polymerization mode of the acrylic polymer in this embodiment may be a random polymer or a block polymer.

[0059] The weight-average molecular weight of the acrylic polymer is preferably 100,000 to 1,200,000, particularly preferably 200,000 to 1,000,000, and even more preferably 300,000 to 800,000. The weight-average molecular weight in this specification is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0060] In this embodiment, the thickness of the adhesive layer is preferably 1 μm or more, particularly preferably 3 μm or more, and even more preferably 5 μm or more. Having a thickness of 1 μm or more makes it easier for the workpiece processing sheet to exhibit good adhesive strength, making it easier to suppress chipping, for example. Furthermore, the thickness is preferably 60 μm or less, particularly preferably 30 μm or less, and even more preferably 20 μm or less. Having a thickness of 60 μm or less makes it easier to pick up the workpiece.

[0061] (3) Release sheet In the workpiece processing sheet of this embodiment, a release sheet may be laminated on the side of the adhesive layer opposite the substrate (hereinafter sometimes referred to as the "adhesive side") in order to protect that side until it is attached to the workpiece.

[0062] The release sheet may have any configuration, and may be, for example, a plastic film that has been subjected to a release treatment using a release agent or the like. Specific examples of such plastic films include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene. Examples of the release agent that can be used include silicone-based, fluorine-based, long-chain alkyl, and rubber-based agents, and among these, silicone-based agents are preferred because they are inexpensive and provide stable performance.

[0063] There are no particular limitations on the thickness of the release sheet, and it may be, for example, 16 μm or more and 250 μm or less.

[0064] (4) Other In the workpiece processing sheet according to this embodiment, an adhesive layer may be laminated on the surface of the adhesive layer opposite the substrate. In this case, the workpiece processing sheet according to this embodiment can be used as a dicing / die bonding sheet. In this sheet, a workpiece is attached to the surface of the adhesive layer opposite the adhesive layer, and the adhesive layer is diced together with the workpiece to obtain a chip on which the individualized adhesive layer is laminated. The individualized adhesive layer allows the chip to be easily fixed to the object on which it is to be mounted. As a material for constituting the adhesive layer, it is preferable to use a material containing a thermoplastic resin and a low-molecular-weight thermosetting adhesive component, or a material containing a B-stage (semi-cured) thermosetting adhesive component.

[0065] Furthermore, in the workpiece processing sheet according to this embodiment, a protective film forming layer may be laminated on the adhesive surface of the adhesive layer. In this case, the workpiece processing sheet according to this embodiment can be used as a sheet for both protective film formation and dicing. With such a sheet, a workpiece is attached to the surface of the protective film forming layer opposite the adhesive layer, and the protective film forming layer is diced together with the workpiece to obtain a chip on which a singulated protective film forming layer is laminated. It is preferable that the workpiece has a circuit formed on one side. In this case, the protective film forming layer is typically laminated on the surface opposite the surface on which the circuit is formed. By curing the singulated protective film forming layer at a predetermined timing, a protective film with sufficient durability can be formed on the chip. The protective film forming layer is preferably made of an uncured curable adhesive.

[0066] 2. Manufacturing method of workpiece processing sheet The method for producing the workpiece processing sheet according to this embodiment is not particularly limited, and it is preferably produced by laminating an adhesive layer on one side of a substrate.

[0067] The adhesive layer can be laminated on one side of the substrate by a known method. For example, it is preferable to transfer an adhesive layer formed on a release sheet to one side of the substrate. In this case, for example, a coating liquid containing the adhesive composition constituting the adhesive layer is prepared, and the coating liquid is applied to the release-treated surface of the release sheet (hereinafter sometimes referred to as the "release surface") using a die coater, curtain coater, spray coater, slit coater, knife coater, applicator, etc. to form a coating film, and the coating film is dried to form the adhesive layer. The properties of the coating liquid are not particularly limited as long as it can be applied, and it may contain the components for forming the adhesive layer as a solute or as a dispersoid. The release sheet in this laminate may be peeled off as a processing material, or it may be used to protect the adhesive surface of the adhesive layer until the work processing sheet is attached to the adherend.

[0068] Instead of transferring the PSA layer formed on the release sheet to one side of the substrate as described above, the PSA layer may be formed directly on the substrate. In this case, the PSA layer is formed by applying the coating liquid for forming the PSA layer to one side of the substrate to form a coating film, and then drying the coating film.

[0069] 3. How to use the workpiece processing sheet The workpiece processing sheet according to this embodiment can be used to process workpieces such as semiconductor wafers. That is, after the adhesive surface of the workpiece processing sheet according to this embodiment is attached to the workpiece, the workpiece can be processed on the workpiece processing sheet. Depending on the processing, the workpiece processing sheet according to this embodiment can be used as a backgrinding sheet, dicing sheet, expanding sheet, pickup sheet, or sheet used for workpiece selection, inspection, rearrangement, storage, shipping, transport, etc. Examples of workpieces include semiconductor components such as semiconductor wafers and semiconductor packages, and glass components such as glass plates.

[0070] As described above, the workpiece processing sheet according to this embodiment can cure the adhesive layer by irradiating it with a predetermined amount of active energy, thereby effectively reducing the adhesive strength to the adherend. Therefore, the workpiece processing sheet according to this embodiment is preferably used as at least one of a dicing sheet, a pickup sheet, and a backgrinding sheet.

[0071] An example of a preferred method of using the workpiece processing sheet according to this embodiment includes an attachment step of attaching the side of the adhesive layer opposite the substrate to the workpiece, a processing step of processing the workpiece on the workpiece processing sheet, and an irradiation step of irradiating the adhesive layer with active energy rays.

[0072] In the above-mentioned attaching step, the specific method is not limited as long as the adhesive surface of the workpiece processing sheet according to this embodiment is attached to the workpiece.

[0073] The subsequent processing step is performed according to the type of processing, and a conventionally known method can be used. For example, when dicing is performed, a dicing device is used to dice the workpiece on the workpiece processing sheet to obtain multiple semiconductor chips. The type of dicing is not particularly limited, and may be, for example, blade dicing, laser dicing, stealth dicing, etc.

[0074] The irradiation of active energy rays in the irradiation step can be carried out by a conventionally known method. The types of active energy rays are as described above.

[0075] When the workpiece processing sheet according to this embodiment has the adhesive layer described above, the workpiece processing sheet can be used as a dicing / die bonding sheet. Furthermore, when the workpiece processing sheet according to this embodiment has the protective film forming layer described above, the workpiece processing sheet can be used as a protective film forming / dicing sheet.

[0076] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0077] For example, another layer may be provided between the substrate and the pressure-sensitive adhesive layer, or on the surface of the substrate opposite to the pressure-sensitive adhesive layer. [Example]

[0078] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0079] Example 1 (1) Preparation of the substrate Ethylene-methacrylic acid copolymer (EMAA) (manufactured by DuPont-Mitsui Polychemicals, product name "Nucrel N0903HC") was extruded using a small T-die extruder (manufactured by Toyo Seiki Seisakusho, product name "Labo Plastomill") to obtain a long EMAA film with a width of 380 mm and a thickness of 80 μm. This produced the substrate.

[0080] (2) Preparation of adhesive composition 84 parts by mass of butyl acrylate, 6 parts by mass of 2-hydroxyethyl acrylate, and 10 parts by mass of 4-benzoylphenyl methacrylate (4MBP) were polymerized by solution polymerization to obtain a (meth)acrylic acid ester polymer. The weight average molecular weight (Mw) of this acrylic polymer was measured by the method described below and was found to be 800,000.

[0081] 39.7 parts by mass (solid content equivalent, same below) of the acrylic polymer obtained above and 0.6 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., product name "Takenate D-101E") as a crosslinking agent were mixed in a solvent to obtain a coating liquid of a pressure-sensitive adhesive composition.

[0082] (3) Formation of adhesive layer The adhesive composition coating solution obtained in step (2) was applied to the release surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031"), which was a 38 μm-thick polyethylene terephthalate film with a silicone-based release agent layer formed on one side thereof, and the resulting coating film was dried by heating to obtain a laminate consisting of a 10 μm-thick adhesive layer formed by the dried coating film and the release sheet.

[0083] (4) Preparation of workpiece processing sheet Using an electron beam irradiation device (ESI: TYPE300 / 165 / 800), one side of the substrate obtained in the above step (1) was irradiated with an electron beam at a cumulative dose of 50 kGy (irradiation time 2.2 seconds).

[0084] 24 hours after irradiation with the electron beam, the adhesive layer side of the laminate prepared in step (3) was bonded to the electron beam irradiated surface of the substrate, and the laminate was left to stand for one week in an environment of 23°C and 50% humidity to obtain a work processing sheet.

[0085] (4) Method for measuring weight-average molecular weight The weight average molecular weight (Mw) mentioned above is a weight average molecular weight measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement) and converted into standard polystyrene. <Measurement conditions> Measurement equipment: Tosoh HLC-8320 GPC columns (passed in the following order): Tosoh Corporation TSK gel superH-H TSK gel super HM-H TSK gel superH2000 Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0086] Example 2 A workpiece processing sheet was obtained in the same manner as in Example 1, except that the cumulative dose of electron beams applied to the substrate was changed to 100 kGy.

[0087] Comparative Example 1 91 parts by mass of butyl acrylate and 9 parts by mass of acrylic acid were polymerized by solution polymerization to obtain a (meth)acrylic acid ester polymer. The weight average molecular weight (Mw) of this acrylic polymer was measured by the method described below and was found to be 420,000.

[0088] 33.6 parts by mass of the acrylic polymer obtained above, 5.6 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., product name "Takenate D-101E") as a crosslinking agent, 40.0 parts by mass of urethane acrylate (manufactured by Dainichiseika Color & Chemicals Co., Ltd., product name "Seikabeam 14-29B", having a polymerizable carbon-carbon double bond) as an active energy ray-curable component, and 1.2 parts by mass of 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins BV, product name "Omnirad184") as a photopolymerization initiator were mixed in a solvent to obtain a coating liquid of a pressure-sensitive adhesive composition.

[0089] A workpiece processing sheet was obtained in the same manner as in Example 1, except that the above adhesive composition was used.

[0090] Comparative Example 2 A workpiece processing sheet was obtained in the same manner as in Comparative Example 1, except that the cumulative dose of electron beams applied to the substrate was changed to 100 kGy.

[0091] Comparative Example 3 A workpiece processing sheet was obtained in the same manner as in Comparative Example 1, except that the substrate was not irradiated with electron beams.

[0092] [Test Example 1] (Measurement of adhesive strength) Test samples measuring 25 mm wide and 300 mm long were cut out from the workpiece processing sheets (380 mm wide) produced in the Examples and Comparative Examples. Here, the 120 mm wide region from the end of the workpiece processing sheet in the width direction was defined as the peripheral edge, and the 140 mm wide region sandwiched between the peripheral edges was defined as the central region. One test sample was obtained from each of the peripheral and central regions.

[0093] The release sheet was peeled off from each of the obtained peripheral test samples and central test samples, and the exposed surface of the adhesive layer was placed on the mirror surface of a 6-inch silicon wafer. The samples were then laminated by applying a load by rolling a 2 kg roller back and forth once, and left for 20 minutes. This was used as a laminate for adhesive strength measurement.

[0094] The adhesive strength (mN / 25 mm) of the obtained laminate for adhesive strength measurement was measured by peeling the workpiece processing sheet from the silicon wafer at a peeling speed of 300 mm / min and a peeling angle of 180° using the 180° peeling method in accordance with JIS Z0237: 2009. The adhesive strengths of the peripheral and central areas are shown in Table 1.

[0095] Furthermore, the rate of change, which indicates how much the adhesive strength at the center has decreased, was calculated using the adhesive strength at the periphery as the standard using the following formula. The results are shown in Table 1. Change rate (%) = {(adhesive strength of periphery - adhesive strength of center) / adhesive strength of periphery} x 100

[0096] The calculated change rate was then evaluated for unevenness in adhesive strength based on the following criteria. The results are shown in Table 1. ○: The rate of change was 30% or less. ×: The rate of change was more than 30%.

[0097] [Test Example 2] (Evaluation of Cutting Chips) One side of the silicon wafer was ground using a grinding device, and then the release sheet was peeled off from the workpiece processing sheet produced in the Examples and Comparative Examples, and the exposed adhesive surface of the adhesive layer was attached to the ground surface of the silicon wafer using a laminator.

[0098] Twenty minutes after the above attachment, the silicon wafer was diced into individual chips using a dicing device (manufactured by Disco Corporation, product name "DFD6362") under the following dicing conditions. <Dicing conditions> Chip size: 10mm x 10mm Cutting height: 60 μm Blade: Product name "ZH05-SD2000-Z1-90 CC" Blade rotation speed: 35,000 rpm Cutting speed: 60mm / sec Cutting water amount: 1.0L / min Cutting water temperature: 20℃

[0099] Next, the workpiece processing sheet was irradiated with ultraviolet light from the substrate side using an ultraviolet irradiation device (manufactured by Lintec Corporation, product name "RAD-2010") (illuminance: 230 mW / cm 2 ,Light amount: 190mJ / cm 2 ), and the adhesive layer was cured.

[0100] After the workpiece was completely separated from the workpiece processing sheet, a magnifying glass was used to count the number of thread-like scraps (cutting chips) with a length of 100 μm or more that had occurred on the dicing line of the workpiece processing sheet. The results are shown in Table 1.

[0101] The number of chips was evaluated based on the following criteria to evaluate chip suppression. The results are shown in Table 1. ◯: There were 50 or fewer cutting chips. ×: More than 50 cutting chips were found.

[0102] [Table 1]

[0103] As can be seen from Table 1, the workpiece processing sheets obtained in the examples were able to effectively suppress the generation of cutting chips, while there was no difference in adhesive strength between the center and the peripheral areas. [Industrial Applicability]

[0104] The workpiece processing sheet of the present invention can be suitably used for processing workpieces such as semiconductor wafers.

Claims

1. A workpiece processing sheet comprising a substrate and an adhesive layer laminated on one side of the substrate, The substrate is subjected to an electron beam (EB) irradiation treatment, The pressure-sensitive adhesive layer is represented by the following formula (1): 【Chemical 1】 (In formula (1), R1 represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.) The adhesive is formed from an adhesive composition containing a component having a benzophenyl structure represented by The content of a component having a polymerizable carbon-carbon double bond in the pressure-sensitive adhesive composition is 0.1% by mass or less. A workpiece processing sheet characterized by:

2. the pressure-sensitive adhesive composition contains an acrylic polymer, The acrylic polymer contains, as a monomer unit constituting the polymer, a monomer having a benzophenyl structure represented by the formula (1).

2. The workpiece processing sheet according to claim 1.

3. The pressure-sensitive adhesive layer may be formed by a method represented by the following formula (2): 【Chemistry 2】 (In formula (2), R ２ and R ３ each represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and n represents an integer of 1 to 15.

2. The workpiece processing sheet according to claim 1, characterized in that it has a structure shown in FIG.

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

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