Sheet for processing workpiece and method for manufacturing processed workpiece

Abstract

To provide a sheet for workpiece processing capable of suppressing an excessive increase in adhesion even to an active surface of a workpiece and realizing good processing of the workpiece.SOLUTION: A workpiece processing sheet includes a substrate and an adhesive layer laminated on one side of the substrate, the adhesive layer is composed of an active energy ray-curable adhesive containing a hindered amine stabilizer, the workpiece processing sheet is intended to be attached to the ground surface of a workpiece within 120 minutes of grinding the surface.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a workpiece processing sheet that can be suitably used for processing workpieces such as semiconductor wafers, and a method for manufacturing a processed workpiece using the workpiece processing sheet. In particular, the present invention relates to a workpiece processing sheet that can be suitably used for processing a workpiece having a surface in an active state (hereinafter sometimes referred to as an "active surface"), and a method for manufacturing a processed workpiece using the workpiece processing sheet. [Background technology]

[0002] Semiconductor wafers such as silicon and gallium arsenide and various packages are manufactured in a large diameter state, cut (diced) into small element pieces (semiconductor chips), peeled off (picked up), and then transferred to the next process, the mounting process. At this time, the workpieces such as semiconductor wafers are attached to a workpiece processing sheet having a base material and an adhesive layer, and are processed in such a state that back grinding, dicing, cleaning, drying, expanding, picking up, mounting, etc. are performed.

[0003] In the back grinding process, the workpiece is usually fixed on a workpiece processing sheet, and the exposed surface of the workpiece is ground using a grinding device. After grinding, the workpiece is diced on the workpiece processing sheet in a dicing process and divided into a plurality of chips. Then, the resulting plurality of chips are individually picked up from the workpiece processing sheet in a pick-up process.

[0004] The workpiece having one side ground in the back grinding process may be replaced with a new workpiece processing sheet prior to the grinding process. In this case, the adhesive layer side of the new workpiece processing sheet (hereinafter sometimes referred to as the "adhesive side") is attached to the ground surface, and the previous workpiece processing sheet is peeled off.

[0005] In recent years, the above-mentioned grinding, re-attaching and dicing processes are sometimes performed continuously in-line. In this case, the workpiece processing sheet is attached to the ground surface of the workpiece immediately after grinding.

[0006] Here, generally, the grinding surface of the workpiece immediately after grinding is in an activated state by grinding. Therefore, when attaching the workpiece processing sheet immediately after grinding the workpiece, the workpiece processing sheet is attached to the activated surface of the workpiece. In this case, the adhesion between the workpiece and the workpiece processing sheet is likely to increase excessively due to the activation of the activated surface. In particular, the adhesion tends to increase the longer the workpiece and the workpiece processing sheet are stacked. And, if the workpiece and the workpiece processing sheet are excessively adhered to each other in the subsequent pick-up process, the obtained chips will be strongly adhered to the workpiece processing sheet, and good pick-up will not be possible.

[0007] Generally, in order to enable good pick-up, a workpiece processing sheet having an adhesive layer made of an adhesive having active energy ray curing properties is used. In this case, the adhesive layer is irradiated with active energy rays just before pick-up to harden the adhesive layer, thereby reducing the adhesive force to the chip and facilitating the separation of the chip. However, even when such a workpiece processing sheet is used, it is difficult to avoid the problem of not being able to pick up well as described above.

[0008] In order to solve the problems related to increased adhesion to the active surface of the workpiece as described above, Patent Document 1 discloses a workpiece processing sheet having an active energy ray-curable adhesive layer that contains an alkylene glycol-modified rosin ester as a tackifier. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 7254669 Summary of the Invention [Problem to be solved by the invention]

[0010] By using the workpiece processing sheet disclosed in Patent Document 1, it is possible to obtain a certain effect in terms of reducing adhesion to the active surface of the workpiece. However, there is still a demand for further reducing the adhesion and achieving better processing of the workpiece.

[0011] The present invention has been made in consideration of the above-described circumstances, and aims to provide a workpiece processing sheet that can suppress excessive adhesion to the active surface of the workpiece and achieve good workpiece processing, and a method for manufacturing a processed workpiece using the workpiece processing sheet. [Means for solving the problem]

[0012] In order to achieve the above-mentioned object, firstly, the present invention provides a workpiece processing sheet comprising a base material and an adhesive layer laminated on one side of the base material, wherein the adhesive layer is composed of an active energy ray-curable adhesive containing a hindered amine stabilizer, and the workpiece processing sheet is intended to be attached to the ground surface of a workpiece within 120 minutes of grinding the surface (Invention 1).

[0013] In the workpiece processing sheet according to the above invention (Invention 1), the adhesive layer is composed of an active energy ray curable adhesive containing a hindered amine stabilizer, so that even when the sheet is applied to the active surface of a workpiece, the adhesive layer can be cured well by irradiation with active energy rays, and the adhesive strength can be sufficiently reduced accordingly. Therefore, the workpiece processing sheet can be easily separated from the workpiece even after it is applied to the active surface of the workpiece and stored for a long period of time.

[0014] Secondly, the present invention provides a workpiece processing sheet comprising a substrate and an adhesive layer laminated on one side of the substrate, the adhesive layer being made of an active energy ray curable adhesive containing a hindered amine stabilizer, and the surface of the adhesive layer opposite the substrate is attached to the ground surface of a silicon wafer within 20 minutes of grinding the surface, the laminate of the workpiece processing sheet and the silicon wafer being obtained, the adhesive strength of the workpiece processing sheet to the silicon wafer after irradiating the adhesive layer with ultraviolet light immediately after the attachment is F0, and the adhesive strength of the workpiece processing sheet to the silicon wafer after storing the workpiece processing sheet for 7 days and irradiating the adhesive layer with ultraviolet light is F7, the adhesive strength increase rate calculated as the ratio of F7 to F0 (F7 / F0) is 2.0 or less (Invention 2).

[0015] In the workpiece processing sheet according to the above invention (invention 2), the adhesive layer is composed of an active energy ray curable adhesive containing a hindered amine stabilizer, and by showing the above-mentioned adhesive strength increase rate, even when the sheet is applied to the active surface of a workpiece, the adhesive layer can be cured well by irradiation with active energy rays, and the adhesive strength can be sufficiently reduced accordingly. Therefore, the workpiece processing sheet allows easy separation of the workpiece, for example, even after being applied to the active surface of the workpiece and being stored for a long period of time.

[0016] In the above inventions (Inventions 1 and 2), the hindered amine stabilizer is preferably an N-alkyl hindered amine stabilizer (Invention 3).

[0017] In the above inventions (Inventions 1 to 3), the active energy ray-curable adhesive is preferably formed from an adhesive composition containing an acrylic polymer having an active energy ray-curable group introduced into a side chain thereof and the hindered amine stabilizer (Invention 4).

[0018] Thirdly, the present invention provides a method for manufacturing a machined workpiece, comprising a grinding step for grinding the surface of the workpiece, an attachment step for attaching the workpiece processing sheet (Inventions 1 to 4) to the ground surface of the workpiece, a dicing step for dicing the workpiece on the workpiece processing sheet to obtain a plurality of chips formed by dividing the workpiece, an active energy ray irradiation step for irradiating the adhesive layer on the workpiece processing sheet with active energy rays, and a pick-up step for individually picking up the chips from the workpiece processing sheet (Invention 5).

[0019] In the above invention (Invention 5), it is preferable that the attachment of the workpiece processing sheet to the workpiece in the attachment step is performed within 120 minutes after grinding of the surface of the workpiece in the grinding step (Invention 6). Effect of the Invention

[0020] The workpiece processing sheet according to the present invention can suppress excessive adhesion to the active surface of the workpiece, and can achieve good processing of the workpiece. Also, the manufacturing method according to the present invention can produce a processed workpiece in a good condition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described. The workpiece processing sheet according to the present embodiment includes a substrate and an adhesive layer laminated on one side of the substrate. The adhesive layer is made of an active energy ray-curable adhesive containing a hindered amine stabilizer.

[0022] In the first embodiment, the workpiece processing sheet is intended to be attached to the ground surface of a workpiece within 120 minutes of the surface being ground.

[0023] In addition, as a second embodiment, the workpiece processing sheet is obtained by attaching the side of the adhesive layer opposite the substrate to the ground surface of a silicon wafer within 20 minutes of grinding the surface, and the laminate of the workpiece processing sheet and the silicon wafer satisfies the following conditions.

[0024] First, the adhesive strength of the workpiece processing sheet to the silicon wafer after the adhesive layer is irradiated with ultraviolet light immediately after the attachment is defined as F0.

[0025] In addition, the adhesive strength of the workpiece processing sheet to the silicon wafer after storing for 7 days from the application and then irradiating the adhesive layer with ultraviolet light is designated as F7.

[0026] In the above cases, in the workpiece processing sheet according to the second embodiment, the adhesive strength increase rate calculated as the ratio of F7 to F0 (F7 / F0) is 2.0 or less.

[0027] In the workpiece processing sheet according to the present embodiment including the above-mentioned first and second embodiments, the adhesive layer is made of an active energy ray curable adhesive, so that the adhesive layer is cured by irradiation with active energy rays, thereby reducing the adhesive strength to the workpiece. Therefore, when it is desired to separate the workpiece processing sheet according to the present embodiment from the workpiece, the workpiece can be easily separated without destroying the workpiece or preventing a part of the adhesive constituting the adhesive layer from adhering to the workpiece (glue residue).

[0028] Furthermore, in the workpiece processing sheet according to the present embodiment, since the active energy ray curable adhesive contains a hindered amine stabilizer, even if the workpiece processing sheet is attached to the active surface of the workpiece and is stored in the attached state for a long period of time, the adhesion to the workpiece is prevented from increasing excessively. As a result, the workpiece processing sheet can be easily separated from the workpiece by irradiating the active energy ray as described above.

[0029] The workpiece processing sheet according to this embodiment is expected to suppress an excessive increase in adhesion to the workpiece for the following reasons, although they are not limited to these.

[0030] First, the mechanism by which the surface of the workpiece is activated is that by grinding the surface of the workpiece, the inactive parts present on the surface are removed, and the active parts inside are exposed. For example, when the workpiece is a silicon wafer, it is considered that the surface of the silicon wafer is oxidized under normal conditions, and an inactive SiO2 film is formed. When the surface of such a silicon wafer is ground, the SiO2 film is removed, and the unoxidized silicon atoms are exposed. The exposed silicon atoms may react with the cleaning water used in the back grinding process or with moisture in the air to partially form Si-H or Si-OH structures. The surface exposed by removing the SiO2 film in this way is easily interacted with the adhesive surface of a general workpiece processing sheet, and is also in a state where it is easily chemically bonded with the adhesive that constitutes the adhesive layer.

[0031] In addition, grinding the surface of the workpiece may generate radicals on the surface, which may activate the surface. For example, on the ground surface, radicals (R·) are generated by hydrogen abstraction from the RH group. Then, some of the radicals (R·) react with oxygen molecules in the air to generate peroxy radicals (ROO·). Some of these radicals then abstract hydrogen from the RH group to generate hydroperoxides (ROOH) and radicals (R·). Furthermore, some of the generated hydroperoxides (ROOH) decompose to generate oxyl (RO·) and hydroxyl (·OH). A surface on which a large number of radicals are generated in this way is prone to interact with the adhesive surface of a typical workpiece processing sheet, and is prone to chemical bonding with the adhesive that constitutes the adhesive layer.

[0032] However, in the workpiece processing sheet according to this embodiment, the hindered amine stabilizer and the stable radicals generated in the system due to it are considered to trap or inactivate the generated radicals as described above, thereby suppressing the interaction with the active energy ray curable adhesive and the generation of chemical bonds. As a result, the workpiece processing sheet according to this embodiment can effectively suppress the increase in adhesion with the active surface.

[0033] In particular, it is considered that the hindered amine stabilizer can trap at least three of the above-mentioned multiple types of radicals, namely, R·, RO·, and ROO·. In contrast, other stabilizers (hindered phenol stabilizers, phosphite stabilizers, etc.) can trap fewer types of radicals or cannot trap radicals at all. Therefore, the workpiece processing sheet according to this embodiment can effectively suppress the increase in adhesion to the active surface by using the hindered amine stabilizer.

[0034] In addition, after trapping the radical (bonding with the radical), the hindered amine stabilizer undergoes a reaction to separate the radical portion again, and is regenerated as a hindered amine stabilizer. Therefore, the hindered amine stabilizer can continuously exert its effect as a stabilizer. Note that such a regenerating action does not occur in the hindered phenol compounds that have been used conventionally. From this point of view, the workpiece processing sheet according to this embodiment can effectively suppress an increase in adhesion to the active surface.

[0035] In this specification, the surface of the workpiece being in an activated state refers to a state within 120 minutes after the surface of the workpiece has been ground, preferably within 30 minutes after the surface of the workpiece has been ground, and more preferably within 5 minutes after the surface of the workpiece has been ground.

[0036] In addition, the storage period of the laminate of the workpiece and the workpiece processing sheet after the workpiece processing sheet according to this embodiment is attached to the active surface of the workpiece can be set according to the purpose of use. In general, the storage period is often 0 to 500 days, particularly 1 to 90 days, and more often 7 to 30 days.

[0037] 1. Base material The substrate in this embodiment is not particularly limited as long as it exhibits the desired function when the workpiece processing sheet is used. In particular, the substrate in this embodiment is preferably made of a resin, and examples of the resin include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin resins such as polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, ethylene-norbornene copolymer, and norbornene resin; ethylene-vinyl acetate copolymer; ethylene-(meth)acrylic acid copolymer, ethylene-methyl(meth)acrylate copolymer, and other ethylene-(meth)acrylic acid ester copolymers; polyvinyl chloride resins such as polyvinyl chloride copolymers; (meth)acrylic acid ester copolymers; polyurethane; polyimide; polystyrene; polycarbonate; and fluororesins. The resin constituting the substrate may be a crosslinked resin or a modified resin such as an ionomer of the above-mentioned resin. In this specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid. The same applies to other similar terms. In addition, the term "polymer" in this specification also includes the concept of "copolymer."

[0038] The substrate in this embodiment may be a single-layer film made of the above-mentioned resin, or may be a laminate film in which a plurality of such films are laminated. In this laminate film, the materials constituting the layers may be the same or different.

[0039] The substrate may contain various additives such as a flame retardant, a plasticizer, an antistatic agent, a lubricant, an antioxidant, a colorant, an infrared absorbing agent, an ultraviolet absorbing agent, an ion trapping agent, etc. The content of these additives is not particularly limited, but is preferably within a range in which the substrate exhibits the desired function.

[0040] In addition, the substrate is preferably transparent to active energy rays. By using such a substrate, the pressure-sensitive adhesive layer can be easily cured well even when the pressure-sensitive adhesive layer is irradiated with active energy rays through the substrate.

[0041] Furthermore, the surface of the substrate on which the pressure-sensitive adhesive layer is to be laminated may be subjected to a surface treatment such as a primer treatment, a corona treatment, or a plasma treatment in order to enhance adhesion to the pressure-sensitive adhesive layer.

[0042] The thickness of the substrate can be appropriately set depending on the method in which the workpiece processing sheet is used, but is preferably 200 μm or less, particularly preferably 150 μm or less, and is preferably 10 μm or more, particularly preferably 25 μm or more.

[0043] 2. Adhesive layer As described above, the pressure-sensitive adhesive layer in this embodiment is composed of an active energy ray-curable pressure-sensitive adhesive containing a hindered amine-based stabilizer.

[0044] Examples of the pressure-sensitive adhesive are not particularly limited, and 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. However, it is preferable to use an acrylic pressure-sensitive adhesive, from the viewpoints of easiness in forming an active energy ray-curable pressure-sensitive adhesive and easiness in exerting a desired adhesive strength.

[0045] The active energy ray curable adhesive may be one that mainly comprises a polymer having active energy ray curability, or one that mainly comprises a mixture of a non-active energy ray curable polymer (a polymer not having active energy ray curability) and a monomer and / or oligomer having at least one or more active energy ray curable groups. Furthermore, the active energy ray curable adhesive may be a mixture of a polymer having active energy ray curability and a monomer and / or oligomer having at least one or more active energy ray curable groups. Among these, the active energy ray curable adhesive in this embodiment is preferably one that mainly comprises a polymer having active energy ray curability (particularly, an acrylic polymer having active energy ray curability) from the viewpoint of suppressing the adverse effect caused by an excessive increase in adhesive strength even after heat treatment and facilitating separation of a good workpiece by reducing adhesive strength using a trigger.

[0046] The active energy ray-curable acrylic polymer is preferably an acrylic polymer having a functional group (active energy ray-curable group) having active energy ray-curability introduced into a side chain (hereinafter, may be referred to as "active energy ray-curable polymer (A)"). In this case, the active energy ray-curable adhesive in this embodiment is preferably formed from an adhesive composition containing an acrylic polymer having an active energy ray-curable group introduced into a side chain (active energy ray-curable polymer (A) and a hindered amine-based stabilizer.

[0047] (1) Active energy radiation curable polymer (A) The active energy radiation curable polymer (A) is preferably obtained by reacting a (meth)acrylic acid ester polymer (a1) having a functional group-containing monomer unit with an unsaturated group-containing compound (a2) having a functional group bonded to the functional group.

[0048] As the functional group-containing monomer described above, a monomer having a polymerizable double bond and a functional group such as a hydroxyl group, a carboxyl group, an amino group, an amide group, a benzyl group, or a glycidyl group in the molecule is preferred, and among these, it is preferred to use a monomer containing a hydroxyl group as a functional group (a hydroxyl group-containing monomer).

[0049] Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc., and among these, it is preferable to use at least one of 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate. These may be used alone or in combination of two or more.

[0050] Examples of the carboxyl 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 kinds.

[0051] Examples of the amino group-containing monomer or amide group-containing monomer include aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0052] The (meth)acrylic acid ester polymer (a1) preferably contains 5% by mass or more, particularly preferably 10% by mass or more, of the structural unit derived from the functional group-containing monomer. The (meth)acrylic acid ester polymer (a1) preferably contains 40% by mass or less, particularly preferably 35% by mass or less, of the structural unit derived from the functional group-containing monomer. When the (meth)acrylic acid ester polymer (a1) contains the functional group-containing monomer in the above range, it becomes easy to form the desired active energy radiation curable polymer (A).

[0053] From the viewpoint of facilitating the formation of a pressure-sensitive adhesive having desired properties, the (meth)acrylic acid ester polymer (a1) preferably contains a (meth)acrylic acid alkyl ester as a monomer unit constituting the (meth)acrylic acid ester polymer (a1). The (meth)acrylic acid alkyl ester is preferably one in which the alkyl group has 1 to 18 carbon atoms, and more preferably one in which the alkyl group has 1 to 8 carbon atoms.

[0054] Specific examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate. These may be used alone or in combination of two or more. Among the above-mentioned (meth)acrylic acid alkyl esters, it is preferable to use 2-ethylhexyl acrylate.

[0055] The (meth)acrylic acid ester polymer (a1) preferably contains 20% by mass or more, particularly preferably 30% by mass or more, of the structural units derived from the (meth)acrylic acid alkyl ester. The (meth)acrylic acid ester polymer (a1) preferably contains 95% by mass or less, particularly preferably 85% by mass or less, of the structural units derived from the (meth)acrylic acid alkyl ester. When the (meth)acrylic acid ester polymer (a1) contains the (meth)acrylic acid alkyl ester in the above range, the work processing sheet is more likely to exhibit the desired adhesive strength.

[0056] The (meth)acrylic acid ester polymer (a1) may contain, as monomer units constituting the (meth)acrylic acid ester polymer (a1), other monomers in addition to the above-mentioned functional group-containing monomer and (meth)acrylic acid alkyl ester.

[0057] Examples of the other monomers include nitrogen atom-containing monomers; alkoxyalkyl group-containing (meth)acrylic acid esters such as methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, and ethoxyethyl (meth)acrylate; (meth)acrylic acid esters having an aliphatic ring such as cyclohexyl (meth)acrylate; (meth)acrylic acid esters having an aromatic ring such as phenyl (meth)acrylate; non-crosslinkable acrylamide such as (meth)acrylamide and N,N-dimethyl(meth)acrylamide; (meth)acrylic acid esters having a non-crosslinkable tertiary amino group such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate; vinyl acetate; and styrene.

[0058] Examples of the nitrogen atom-containing monomer include a monomer having an amino group, a monomer having an amide group, a monomer having a nitrogen-containing heterocycle, etc. Examples of the monomer having a nitrogen-containing heterocycle include N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylaziridine, aziridinylethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, and N-vinylphthalimide.

[0059] It is also preferable that the (meth)acrylic acid ester polymer (a1) uses, as a monomer unit constituting the (meth)acrylic acid ester polymer (a1), a monomer having a glass transition temperature (Tg) as a homopolymer of more than 10° C. Examples of such monomers include vinyl acetate, N-(meth)acryloylmorpholine, and methyl methacrylate. When using the above monomers, the (meth)acrylic acid ester polymer (a1) preferably contains 10% by mass or more and 60% by mass or less of the structural units derived from the above monomers.

[0060] The polymerization mode of the (meth)acrylic acid ester polymer (a1) may be a random copolymer or a block copolymer. The polymerization method is not particularly limited, and the polymer can be polymerized by a general polymerization method, for example, a solution polymerization method.

[0061] The (meth)acrylic acid ester polymer (a1) having the functional group-containing monomer unit is reacted with an unsaturated group-containing compound (a2) having a functional group bonded to the functional group, to obtain an active energy radiation-curable polymer (A).

[0062] The functional group of the unsaturated group-containing compound (a2) can be appropriately selected according to the type of functional group of the functional group-containing monomer unit of the (meth)acrylic acid ester polymer (a1). For example, when the functional group of the (meth)acrylic acid ester polymer (a1) is a hydroxyl group, an amino group, or a carboxyl group, the functional group of the unsaturated group-containing compound (a2) is preferably an isocyanate group, an epoxy group, or an aziridinyl group, and when the functional group of the (meth)acrylic acid ester polymer (a1) is a glycidyl group, the functional group of the unsaturated group-containing compound (a2) is preferably an amino group, a carboxyl group, or an aziridinyl group.

[0063] The unsaturated group-containing compound (a2) contains at least one, preferably 1 to 6, more preferably 1 to 4 active energy ray-polymerizable carbon-carbon double bonds in one molecule. Specific examples of such unsaturated group-containing compound (a2) include, for example, 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, 2-(2-methacryloyloxyethyloxy)ethyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate; diisocyanate compounds. or an acryloyl monoisocyanate compound obtained by reacting a polyisocyanate compound with hydroxyethyl (meth)acrylate; an acryloyl monoisocyanate compound obtained by reacting a diisocyanate compound or a polyisocyanate compound with a polyol compound and hydroxyethyl (meth)acrylate; glycidyl (meth)acrylate; (meth)acrylic acid, 2-(1-aziridinyl)ethyl (meth)acrylate, 2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline, and the like.

[0064] The unsaturated group-containing compound (a2) is preferably used in an amount of 50 mol% or more, particularly preferably 60 mol% or more, and even more preferably 70 mol% or more, based on the mole number of the functional group-containing monomer in the (meth)acrylic acid ester polymer (a1). The unsaturated group-containing compound (a2) is preferably used in an amount of 95 mol% or less, particularly preferably 93 mol% or less, and even more preferably 90 mol% or less, based on the mole number of the functional group-containing monomer in the (meth)acrylic acid ester polymer (a1).

[0065] In the reaction between the (meth)acrylic acid ester polymer (a1) and the unsaturated group-containing compound (a2), the reaction temperature, pressure, solvent, time, presence or absence of a catalyst, and type of catalyst can be appropriately selected according to the combination of the functional group of the (meth)acrylic acid ester polymer (a1) and the functional group of the unsaturated group-containing compound (a2). As a result, the functional group present in the (meth)acrylic acid ester polymer (a1) reacts with the functional group in the unsaturated group-containing compound (a2), and the unsaturated group is introduced into the side chain of the (meth)acrylic acid ester polymer (a1), thereby obtaining the active energy radiation curable polymer (A).

[0066] The weight average molecular weight (Mw) of the active energy radiation curable polymer (A) thus obtained is preferably 10,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more. The weight average molecular weight (Mw) is preferably 1,500,000 or less, and even more preferably 1,000,000 or less. In this specification, the weight average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0067] (2) Hindered amine stabilizers In the present specification, the hindered amine stabilizer refers to a stabilizer having one or more amine skeletons in the molecule. The hindered amine stabilizer in the present embodiment is not particularly limited as long as it has such a structure.

[0068] In addition, generally, the hindered amine stabilizer includes N-alkyl hindered amine stabilizers, which are compounds having one or more structures in the molecule in which an alkyl group is bonded to a nitrogen atom of a 2,2,6,6-tetramethylpiperidine skeleton; N-alkoxy hindered amine stabilizers, which are compounds having one or more structures in the molecule in which an alkoxy group is bonded to a nitrogen atom of a 2,2,6,6-tetramethylpiperidine skeleton; and NH-type hindered amine stabilizers, which are compounds having one or more structures in the molecule in which a hydrogen atom is bonded to a nitrogen atom of a 2,2,6,6-tetramethylpiperidine skeleton. In the workpiece processing sheet according to the present embodiment, good effects can be obtained even when any of these compounds are used, but from the viewpoint of easily achieving separation of the workpiece even after long-term storage in a state where it is attached to the active surface of the workpiece, it is preferable to use N-alkyl hindered amine stabilizers.

[0069] Examples of the alkyl group in the above-mentioned N-alkyl hindered amine stabilizer include methyl, ethyl, n-propyl, isopropyl, n-butyl, n-pentyl, n-hexyl, and n-octyl groups. Among these, the methyl group is preferred from the viewpoint of achieving easy separation of the workpiece even after long-term storage while attached to the active surface of the workpiece.

[0070] Specific examples of the hindered amine stabilizer include p,p'-dioctyldiphenylamine, phenyl-α-naphthylamine, poly(2,2,4-trimethyl-1,2-dihydroquinoline), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, N,N'-diphenyl-p-phenylenediamine, N,N'-di-β-naphthyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N,N'-diallyl-p-phenylenediamine, 4,4'-(α,α-dimethylbenzyl)diphenylamine, p,p-toluenesulfonyl ether, and the like. phenylsulfonylaminodiphenylamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, N-(1-methylheptyl)-N'-phenyl-p-phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamine, N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine, alkylated diphenylamines, dimethyl succinate-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensates, poly[[6-(1,1,3,3-tetramethylpiperidine) N,N'-bis(3-aminopropyl)ethylenediamine-2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazine condensate, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl) bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2-n-butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl) 1,2,3,4-butane tetracarboxylate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butane tetracarboxylate, 1,2,3,4-butane tetracarboxylic acid and 1,2,Mixed esters of 2,6,6-pentamethyl-4-piperidinol and 1-tridecanol, mixed esters of 1,2,3,4-butanetetracarboxylic acid with 2,2,6,6-tetramethyl-4-piperidinol and 1-tridecanol, mixed esters of 1,2,3,4-butanetetracarboxylic acid with 1,2,2,6,6-pentamethyl-4-piperidinol and 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane mixed esters of 1,2,3,4-butanetetracarboxylic acid with 2,2,6,6-tetramethyl-4-piperidinol and 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane; (2,2,6,6-tetramethylene-4-piperidyl)-2-propylenecarboxylate; and (1,2,2,6,6-pentamethyl-4-piperidyl)-2-propylenecarboxylate.

[0071] Among the above specific examples, it is preferable to use a mixed ester of 1,2,3,4-butanetetracarboxylic acid with 1,2,2,6,6-pentamethyl-4-piperidinol and 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane as an N-alkyl hindered amine stabilizer.

[0072] The molar mass of the hindered amine stabilizer is preferably 200 g / mol or more, more preferably 600 g / mol or more, and even more preferably 1000 g / mol or more. The molar mass is preferably 10000 g / mol or less, more preferably 5000 g / mol or less, and even more preferably 3000 g / mol or less. By having the molar mass of the hindered amine stabilizer within these ranges, it becomes easier to achieve easy separation of the workpiece even after it is stored for a long period of time in a state where it is attached to the active surface of the workpiece.

[0073] The content of the hindered amine stabilizer in the above-mentioned adhesive composition is preferably 0.1 parts by mass or more, particularly preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the acrylic polymer (active energy radiation curable polymer (A)) having an active energy radiation curable group introduced into the side chain. The content is preferably 30 parts by mass or less, particularly preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. By having the content of the hindered amine stabilizer within these ranges, it becomes easier to achieve easy separation of the workpiece even after it has been stored for a long period of time while being attached to the active surface of the workpiece.

[0074] (3) Crosslinking agent The above-mentioned adhesive composition also preferably contains a crosslinking agent. By containing a crosslinking agent in the adhesive composition, the active energy radiation curable polymer (A) is crosslinked in the adhesive layer, and a good three-dimensional network structure can be formed. This improves the cohesive strength of the obtained adhesive, and effectively suppresses the occurrence of glue residue in the workpiece separated from the workpiece processing sheet after irradiation with active energy rays. In addition, when the adhesive composition contains a crosslinking agent, the active energy radiation curable polymer (A) preferably contains the above-mentioned functional group-containing monomer as a monomer unit constituting the polymer, and in particular, it is preferable to contain a functional group-containing monomer having a functional group highly reactive with the crosslinking agent used.

[0075] Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. These crosslinking agents can be selected according to the functional groups derived from the functional group-containing monomers possessed by the acrylic copolymer. These crosslinking agents can be used alone or in combination of two or more.

[0076] The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and biuret and isocyanurate forms thereof, as well as adducts which are reaction products with low-molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, it is preferable to use at least one of an isocyanurate of hexamethylene diisocyanate, particularly an isocyanurate trimer of 1,6-hexamethylene diisocyanate, trimethylolpropane-modified tolylene diisocyanate, and trimethylolpropane-modified hexamethylene diisocyanate.

[0077] When the above-mentioned adhesive composition contains a crosslinking agent, the content of the crosslinking agent in the adhesive composition is preferably 0.01 parts by mass or more, particularly preferably 0.1 parts by mass or more, and more preferably 0.4 parts by mass or more, relative to 100 parts by mass of the active energy radiation curable polymer (A). In addition, the content is preferably 20 parts by mass or less, particularly preferably 5 parts by mass or less. When the content of the crosslinking agent is 0.01 parts by mass or more, it becomes easier to improve the cohesive force of the adhesive layer after irradiation with active energy rays, and therefore it becomes possible to effectively suppress adhesive residue. In addition, when the content of the crosslinking agent is 20 parts by mass or less, the degree of crosslinking becomes appropriate, and the adhesive layer easily exhibits the desired adhesive force.

[0078] (4) Photopolymerization initiator The pressure-sensitive adhesive composition in the present embodiment also preferably contains a photopolymerization initiator. By containing a photopolymerization initiator in the pressure-sensitive adhesive composition, it is possible to reduce the polymerization curing time and the light irradiation dose when the pressure-sensitive adhesive layer is cured by irradiating with active energy rays.

[0079] Examples of photopolymerization initiators include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, and diphenyl ether. Cetyl, β-chloroanthraquinone, (2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one), (2,4,6-trimethylbenzyldiphenyl)phosphine oxide, 2-benzothiazole-N,N-diethyldithiocarbamate, oligo{2-hydroxy-2-methyl-1-[4-(1-propenyl)phenyl]propanone}, 2,2-dimethoxy-1,2-diphenylethane-1-one, etc. Among these, it is preferable to use at least one of 1-hydroxycyclohexyl phenyl ketone and (2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one). The above-mentioned photopolymerization initiators may be used alone or in combination of two or more.

[0080] When the above-mentioned adhesive composition contains a photopolymerization initiator, the content of the photopolymerization initiator in the adhesive composition is preferably 0.1 parts by mass or more, particularly preferably 1 part by mass or more, relative to 100 parts by mass of the active energy radiation curable polymer (A). The content is preferably 20 parts by mass or less, particularly preferably 5 parts by mass or less. When the content of the photopolymerization initiator is within the above range, the adhesive layer can be efficiently cured by irradiation with active energy rays, and therefore the adhesive force of the work processing sheet to the adherend can be easily and satisfactorily reduced.

[0081] (5) Other ingredients The adhesive composition described above can contain desired additives, such as silane coupling agents, antistatic agents, tackifiers, antioxidants, softeners, fillers, refractive index adjusters, etc., as long as the additives do not impair the effects of the workpiece processing sheet according to this embodiment.

[0082] (6) Method for preparing pressure-sensitive adhesive composition The pressure-sensitive adhesive composition in this embodiment can be produced by producing an active energy radiation curable polymer (A), and mixing the obtained active energy radiation curable polymer (A) with a hindered amine stabilizer, and optionally a crosslinking agent, a photopolymerization initiator, and optional additives. At this time, a dilution solvent may be added as desired to obtain a coating solution of the pressure-sensitive adhesive composition.

[0083] Examples of the dilution solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve-based solvents such as ethyl cellosolve.

[0084] The concentration and viscosity of the coating solution thus prepared are not particularly limited as long as they are within the range that allows coating, and can be appropriately selected according to the situation. For example, the pressure-sensitive adhesive composition is diluted so that its concentration is 10% by mass or more and 60% by mass or less. In addition, when obtaining a coating solution, the addition of a dilution solvent or the like is not a necessary condition, and if the pressure-sensitive adhesive composition has a viscosity that allows coating, it is not necessary to add a dilution solvent. In this case, the pressure-sensitive adhesive composition becomes a coating solution in which the polymerization solvent of the acrylic copolymer (a1) is used as the dilution solvent.

[0085] (7) Thickness of adhesive layer The thickness of the adhesive layer in this embodiment is preferably 1 μm or more, particularly preferably 3 μm or more, and more preferably 4 μm or more. When the thickness of the adhesive layer is 1 μm or more, the workpiece processing sheet can easily exhibit good adhesive strength and can easily suppress chipping. In addition, the thickness is preferably 75 μm or less, particularly preferably 30 μm or less, and more preferably 20 μm or less. When the thickness of the adhesive layer is 75 μm or less, the workpiece can be easily separated.

[0086] 3.Other configurations In the workpiece processing sheet of this embodiment, a release sheet may be laminated on the side (adhesive side) of the adhesive layer opposite the substrate in order to protect that side until it is attached to the workpiece.

[0087] The release sheet may have any structure, 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 the plastic film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene. The release agent may be silicone-based, fluorine-based, long-chain alkyl, rubber-based, or the like, and among these, silicone-based, which is inexpensive and provides stable performance, is preferred.

[0088] There is no particular limitation on the thickness of the release sheet, and it may be, for example, 16 μm or more and 250 μm or less.

[0089] In addition, in the workpiece processing sheet according to this embodiment, an adhesive layer may be laminated on the surface of the adhesive layer opposite to 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 to 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 makes it possible for the chip to be easily fixed to the object on which the chip is mounted. As the material constituting the above-mentioned adhesive layer, it is preferable to use one containing a thermoplastic resin and a low molecular weight thermosetting adhesive component, one containing a B-stage (semi-cured) thermosetting adhesive component, or the like.

[0090] 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 forming a protective film and dicing. In such a sheet, a workpiece is attached to the surface of the protective film forming layer opposite to the adhesive layer, and the protective film forming layer is diced together with the workpiece to obtain a chip on which the individualized protective film forming layer is laminated. As the workpiece, it is preferable to use one having a circuit formed on one side, and in this case, the protective film forming layer is usually laminated on the surface opposite to the surface on which the circuit is formed. The individualized protective film forming layer can be cured at a predetermined timing to form a protective film having sufficient durability on the chip. The protective film forming layer is preferably made of an uncured curable adhesive.

[0091] 4. Physical properties of workpiece processing sheet (1) Rate of increase in adhesive strength It is preferable that the workpiece processing sheet according to this embodiment (particularly the second embodiment) satisfies the above-mentioned conditions for the rate of increase in adhesive strength. That is, it is preferable that the following conditions are satisfied.

[0092] First, consider a laminate of the workpiece processing sheet and the silicon wafer, which is obtained by attaching the side of the adhesive layer opposite the substrate to the ground surface of a silicon wafer within 20 minutes of grinding the surface.

[0093] The adhesive strength of the workpiece processing sheet to the silicon wafer after the adhesive layer is irradiated with ultraviolet light immediately after the attachment is defined as F0.

[0094] In addition, the adhesive strength of the workpiece processing sheet to the silicon wafer after storing for 7 days from the application and then irradiating the adhesive layer with ultraviolet light is designated as F7.

[0095] In the above cases, the adhesive strength increase rate calculated as the ratio of F7 to F0 (F7 / F0) is preferably 2.0 or less, more preferably 1.8 or less, and even more preferably 1.5 or less. This makes it easier to achieve easy separation of the workpiece even after long-term storage in a state where it is attached to the active surface of the workpiece. The lower limit of the adhesive strength increase rate is not particularly limited, and is preferably, for example, 0.9 or more.

[0096] Details of the method for measuring the adhesive strengths F0 and F7 are as described in the test examples described later.

[0097] (2) Increase in adhesive strength In the workpiece processing sheet according to the present embodiment, the adhesive force increase (F7-F0) calculated by subtracting the adhesive force F0 from the adhesive force F7 is preferably 500 mN / 25 mm or less, more preferably 100 mN / 25 mm or less, and even more preferably 50 mN / 25 mm or less. This makes it easier to achieve easy separation of the workpiece even after it has been stored for a long period of time while attached to the active surface of the workpiece. The lower limit of the adhesive force increase (F7-F0) is not particularly limited, and is preferably, for example, 10 mN / 25 mm or less.

[0098] (3) Adhesive strength In the workpiece processing sheet according to the present embodiment, the adhesive strength F0 is preferably 20 mN / 25 mm or more, more preferably 30 mN / 25 mm or more, and even more preferably 40 mN / 25 mm or more. The adhesive strength F0 is preferably 1200 mN / 25 mm or less, more preferably 600 mN / 25 mm or less, and even more preferably 400 mN / 25 mm or less. By being within these ranges, it becomes easier to satisfy the above-mentioned adhesive strength increase rate and adhesive strength increase amount.

[0099] In the workpiece processing sheet according to the present embodiment, the adhesive strength F7 is preferably 20 mN / 25 mm or more, more preferably 30 mN / 25 mm or more, and even more preferably 40 mN / 25 mm or more. The adhesive strength F7 is preferably 1200 mN / 25 mm or less, more preferably 600 mN / 25 mm or less, and even more preferably 400 mN / 25 mm or less. By being within these ranges, the adhesive strength increase rate and adhesive strength increase amount described above are easily satisfied.

[0100] 5. 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.

[0101] The adhesive layer can be laminated on one side of the substrate by a known method. For example, it is preferable to transfer the adhesive layer formed on the release sheet to one side of the substrate. In this case, a coating liquid containing an adhesive composition constituting the adhesive layer and, if desired, a solvent or a dispersion medium 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") by a die coater, curtain coater, spray coater, slit coater, knife coater, roll 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 the components for forming the adhesive layer may be contained as a solute or may be contained as a dispersoid. The release sheet in this laminate may be peeled off as a process material, or may be used to protect the adhesive surface of the adhesive layer until the work processing sheet is attached to the adherend.

[0102] When the coating liquid for forming the adhesive layer contains a crosslinking agent, the crosslinking reaction between the active energy radiation curable polymer (A) in the coating film and the crosslinking agent can be promoted by changing the above-mentioned drying conditions (temperature, time, etc.) or by separately providing a heat treatment, and a crosslinked structure can be formed with a desired density in the adhesive layer. In order to promote this crosslinking reaction sufficiently, the adhesive layer can be laminated on the substrate by the above-mentioned method, and then the obtained work processing sheet can be cured by leaving it for several days in an environment of, for example, 23°C and 50% relative humidity.

[0103] Instead of transferring the pressure-sensitive adhesive layer formed on the release sheet to one side of the substrate as described above, the pressure-sensitive adhesive layer may be formed directly on the substrate. In this case, the coating liquid for forming the pressure-sensitive adhesive layer described above is applied to one side of the substrate to form a coating film, and the coating film is dried to form the pressure-sensitive adhesive layer.

[0104] 6. How to use the workpiece processing sheet The workpiece processing sheet according to this embodiment can be used for processing a workpiece. That is, after the adhesive surface of the workpiece processing sheet according to this embodiment is attached to one side of the workpiece, the workpiece can be processed on the workpiece processing sheet. Examples of the processing include back grinding, dicing, expanding, picking up, and the like. The dicing may be, for example, blade dicing using a rotating round blade, laser dicing in which a semiconductor wafer is fully cut by irradiating a laser beam, or stealth dicing in which a modified layer is formed on a semiconductor wafer by irradiating a laser beam, and then the semiconductor wafer is stretched to divide the semiconductor wafer at the modified layer. The workpiece processing sheet according to this embodiment can be used as a back grinding sheet, a dicing sheet, an expanding sheet, a picking up sheet, or the like, depending on the type of processing.

[0105] Examples of workpieces processed using the workpiece processing sheet according to this embodiment include semiconductor materials such as semiconductor wafers and semiconductor packages, and glass materials such as glass plates. As described above, the workpiece processing sheet according to this embodiment can effectively suppress the increase in adhesion of the workpiece processing sheet to the active surface even when the adhesive surface is attached to the active surface of a workpiece having an active surface. Therefore, the workpiece processing sheet according to this embodiment is suitable for use in processing a workpiece having an active surface (particularly, the ground surface of a semiconductor wafer whose surface has been ground for 120 minutes or less). However, the workpiece processing sheet according to this embodiment can be attached to both a workpiece having an active surface (particularly, the ground surface of a semiconductor wafer whose surface has been ground for 120 minutes or less) and a normal workpiece not having an active surface (particularly, the surface other than the ground surface of a semiconductor wafer whose surface has been ground for 120 minutes or less).

[0106] When the processing of the workpiece on the workpiece processing sheet according to the present embodiment is completed and the processed workpiece is to be separated from the workpiece processing sheet, it is preferable to irradiate the adhesive layer on the workpiece processing sheet with active energy rays before the separation, which hardens the adhesive layer and effectively reduces the adhesive force of the workpiece processing sheet to the processed workpiece, making it easy to separate the processed workpiece.

[0107] As the above-mentioned active energy rays, for example, electromagnetic waves or charged particle beams having an energy quantum can be used, and specifically, ultraviolet rays and electron beams can be used. In particular, ultraviolet rays, which are easy to handle, are preferable. The irradiation of ultraviolet rays can be performed by a high-pressure mercury lamp, a xenon lamp, an LED, etc., and the irradiation amount of ultraviolet rays is 1 mW / cm illuminance. 2 More than 1000mW / cm 2 The light quantity is preferably 10 mJ / cm or less. 2 More preferably, it is 80 mJ / cm or more. 2 More preferably, it is 150 mJ / cm or more. 2 The light quantity is preferably 10,000 mJ / cm or more. 2 It is preferable that the concentration is equal to or less than 5000 mJ / cm 2 It is preferable that the intensity is 2000 mJ / cm or less, and more preferably 2000 mJ / cm 2 On the other hand, the irradiation of the electron beam can be carried out by an electron beam accelerator or the like, and the irradiation dose of the electron beam is preferably 10 krad or more and 1000 krad or less.

[0108] The workpiece processing sheet according to this embodiment is particularly preferably used in a manufacturing method for a machined workpiece, comprising the following steps: That is, the manufacturing method for the machined workpiece comprises a grinding step of grinding the surface of the workpiece, an attachment step of attaching the workpiece processing sheet according to this embodiment to the grinded surface of the workpiece, a dicing step of dicing the workpiece on the workpiece processing sheet to obtain chips formed by dividing the workpiece, an active energy ray irradiation step of irradiating the adhesive layer on the workpiece processing sheet with active energy rays, and a pick-up step of picking up the chips individually from the workpiece processing sheet.

[0109] The grinding step can be carried out using a conventionally known method. For example, the adhesive surface of a desired adhesive sheet (which may be the workpiece processing sheet according to this embodiment) is attached to one side of the workpiece, and the other side of the workpiece is ground on the adhesive sheet using a grinding device. The degree of grinding at this time is selected according to the purpose, and for example, the workpiece is ground until the thickness and surface condition reach a predetermined level. After the grinding, the ground surface may be subjected to a conventionally known surface treatment.

[0110] In the subsequent pasting step, the adhesive surface of the workpiece processing sheet according to the present embodiment is pasted on the ground surface of the workpiece, so long as the adhesive surface is pasted on the ground surface of the workpiece, the specific method is not limited. Here, the time from grinding the surface of the workpiece in the grinding step to the above-mentioned pasting may be within 120 minutes, particularly within 30 minutes, and even within 5 minutes. When the above-mentioned time is within 120 minutes, the ground surface of the workpiece is an activated surface that maintains an activated state, but according to the workpiece processing sheet according to the present embodiment, even with such an activated surface, excessive increase in adhesion is suppressed, and a good pick-up can be performed in the pick-up step described later.

[0111] The subsequent dicing step can be performed using a conventionally known method. That is, a dicing device is used to dice the work on the work processing sheet, and the work is divided into a plurality of chips. The type of dicing is not particularly limited, and may be, for example, blade dicing, laser dicing, stealth dicing, etc.

[0112] The irradiation of the active energy rays in the active energy ray irradiation step can be carried out by a conventionally known method. The type of the active energy rays and the irradiation conditions are as described above.

[0113] The pick-up in the subsequent pick-up process can also be performed by a conventionally known method. For example, the workpiece processing sheet is expanded using a pick-up device, and the semiconductor chip is pushed up from the back side of the workpiece processing sheet with a needle, and the chip is picked up using a suction collet. According to the workpiece processing sheet of this embodiment, an excessive increase in adhesion to the workpiece and the chip is suppressed, so that the problem of being unable to pick up the chip can be avoided and good pick-up can be performed.

[0114] The above-described embodiments are described for the purpose of facilitating understanding of the present invention, and are not described for the purpose of limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0115] For example, another layer may be provided between the substrate and the pressure-sensitive adhesive layer, or on the surface of the substrate opposite the pressure-sensitive adhesive layer. EXAMPLES

[0116] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0117] Example 1 (1) Preparation of substrate Ethylene-methacrylic acid copolymer (EMAA) (manufactured by Mitsui DuPont Polychemicals, product name "Nucrel N0903HC") was extruded using a small T-die extruder (manufactured by Toyo Seiki Seisakusho, product name "Labo Plastomill") to obtain an EMAA film with a thickness of 80 μm. Then, both sides of the obtained EMAA film were subjected to corona treatment. This resulted in the production of a substrate.

[0118] (2) Preparation of Pressure Sensitive Adhesive Composition 40 parts by mass of 2-ethylhexyl acrylate, 40 parts by mass of vinyl acetate, and 20 parts by mass of 2-hydroxyethyl acrylate were polymerized by solution polymerization to obtain a (meth)acrylic acid ester polymer. The weight average molecular weight of the (meth)acrylic acid ester polymer was measured by the method described below and found to be 650,000.

[0119] The (meth)acrylic acid ester polymer obtained was reacted with methacryloyloxyethyl isocyanate (MOI) in an amount equivalent to 80 mol % of the 2-hydroxyethyl acrylate constituting the (meth)acrylic acid ester polymer to obtain an acrylic polymer (active energy radiation curable polymer) having an active energy radiation curable group introduced into the side chain. The weight average molecular weight (Mw) of the active energy radiation curable polymer was measured by the method described below and was found to be 700,000.

[0120] 100 parts by mass of the obtained active energy ray curable polymer, 1 part by mass of trimethylolpropane modified tolylene diisocyanate (manufactured by Mitsui Chemicals, Inc., product name "Takenate D-101E") as a crosslinking agent, 3 parts by mass of 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one (manufactured by IGM Resins, product name "Omnirad 127") as a photopolymerization initiator, and 1.1 parts by mass of tetrakis(2,2,6,6-tetramethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate (N-methyl type hindered amine stabilizer, manufactured by ADEKA, product name "Adekastab LA-52") as a stabilizer were mixed in a solvent to obtain a coating liquid of a pressure-sensitive adhesive composition (solid concentration 30% by mass).

[0121] (3) Formation of adhesive layer The adhesive composition coating solution obtained in step (2) above was applied to the release surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") consisting of a 38 μm-thick polyethylene terephthalate film with a silicone-based release agent layer formed on one side thereof, and the resulting sheet was dried by heating to obtain a laminate consisting of a 5 μm-thick adhesive layer formed on the release sheet.

[0122] (4) Preparation of adhesive sheet One side of the substrate obtained in the above step (1) was laminated to the side of the adhesive layer of the laminate obtained in the above step (3), and then the laminate was stored for 10 days in a light-shielded environment at 23°C and 50% humidity. This produced a workpiece processing sheet.

[0123] (5) Measurement of weight average molecular weight (Mw) of (meth)acrylic acid ester copolymer The above-mentioned weight average molecular weight (Mw) of the (meth)acrylic acid ester copolymer is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement). <Measurement conditions> GPC measuring device: Tosoh HLC-8320 GPC columns (passed in the following order): Tosoh Corporation TSK gel superH-H TSK gel superHM-H TSK gel superH2000 Measurement solvent: Tetrahydrofuran ·Measurement temperature: 40℃

[0124] [Examples 2 to 4 and Comparative Examples 2 to 4] A workpiece processing sheet was obtained in the same manner as in Example 1, except that the type and content of the stabilizer were changed as shown in Table 1.

[0125] Example 5 A workpiece processing sheet was obtained in the same manner as in Example 1, except that the composition of the acrylic polymer (active energy ray curable polymer), the content of the crosslinking agent, and the type and content of the stabilizer were changed as shown in Table 1. The weight average molecular weight (Mw) of the acrylic polymer (active energy ray curable polymer) obtained in Example 5 was measured by the above-mentioned method and was found to be 800,000.

[0126] Example 6 68.5 parts by mass of n-butyl acrylate, 30 parts by mass of methyl acrylate, 0.5 parts by mass of 2-hydroxyethyl acrylate, and 1 part by mass of acrylamide were polymerized by solution polymerization to obtain an acrylic acid polymer. The weight average molecular weight of the acrylic acid polymer was measured by the method described below and found to be 1,000,000.

[0127] A mixture of 100 parts by mass of the obtained acrylic acid polymer, 120 parts by mass of a pentaerythritol-based 5- to 9-functional urethane acrylate oligomer having a weight average molecular weight of 2300 as an oligomer having an active energy ray-curable group, 8 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Mitsui Chemicals, Inc., product name "Takenate D-101E") as a crosslinking agent, and 1-hydroxycyclohexyl phenyl ketone (IGM) as a photopolymerization initiator was used. A coating solution of the adhesive composition (solid concentration 30% by mass) was obtained by mixing 6 parts by mass of Omnirad 184 (manufactured by Resins) and 2.0 parts by mass of a mixed ester of 1,2,3,4-butanetetracarboxylic acid with 1,2,2,6,6-pentamethyl-4-piperidinol and 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane (N-methyl-type hindered amine stabilizer, manufactured by ADEKA Corporation, product name Adekastab LA-63P) as a stabilizer in a solvent.

[0128] A workpiece processing sheet was obtained in the same manner as in Example 1, except that the above-mentioned coating liquid of the adhesive composition was used.

[0129] Comparative Example 1 A workpiece processing sheet was obtained in the same manner as in Example 1, except that no stabilizer was used.

[0130] Comparative Example 5 A workpiece processing sheet was obtained in the same manner as in Example 6, except that no stabilizer was used.

[0131] [Test Example 1] (Measurement of adhesive strength to active surface) The workpiece processing sheets manufactured in the examples and comparative examples were cut into strips of 25 mm width. On the other hand, one side of a silicon wafer was ground using a grinding device (manufactured by Disco, product name "DFG8540") until the thickness of the silicon wafer was 500 μm. The exposed surface of the adhesive layer exposed by peeling the release sheet from the strip-shaped workpiece processing sheet was attached to the ground surface (active surface) activated by the grinding using a 2 kg rubber roller under an environment of a temperature of 23 ° C. and a relative humidity of 50%, and then left to stand for 20 minutes to prepare a measurement sample. The workpiece processing sheet was attached to the active surface within 5 minutes of the grinding.

[0132] The measurement sample was stored in an environment with a temperature of 23° C. and a relative humidity of 50% for one hour.

[0133] After storage, the adhesive layer was irradiated with ultraviolet (UV) light through the substrate 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.

[0134] Next, using a universal tensile testing machine (manufactured by Orientec, product name "Tensilon UTM-4-100"), the workpiece processing sheet was peeled off from the silicon wafer at a peel speed of 300 mm / min and a peel angle of 180°, and the adhesive strength (mN / 25 mm) was measured using the 180° peel method in accordance with JIS Z0237:2009. The adhesive strength thus obtained is shown in Table 1 as the adhesive strength after 0 days of storage (F0).

[0135] The adhesive strength of the sample was also measured in the same manner as above after changing the storage period to 7 days (approximately 168 hours). The results are also shown in Table 1 as adhesive strength after 7 days of storage (F7).

[0136] The increase in adhesive strength (mN / 25 mm) 7 days after application was calculated by subtracting the adhesive strength (F0) from the adhesive strength (F7) measured as described above. The results are also shown in Table 1.

[0137] Furthermore, the adhesive strength increase rate 7 days after application was calculated as the ratio (F7 / F0) of the adhesive strength (F7) to the adhesive strength (F0) measured as described above. The results are also shown in Table 1.

[0138] [Test Example 2] (Evaluation of pick-up properties) Using a grinding device (manufactured by Disco, product name "DFG8540"), one side of the silicon wafer was ground until the thickness of the silicon wafer was 150 μm. The release sheet was peeled off from the workpiece processing sheet manufactured in the examples and comparative examples, and the adhesive surface of the exposed adhesive layer was attached to the ground surface (active surface) activated by the grinding using a laminator. This attachment was performed within 5 minutes of the above grinding.

[0139] After the above attachment, the substrate was stored for 7 days in an environment of a temperature of 23° C. and a relative humidity of 50%, and then dicing was performed under the following conditions. <Dicing conditions> Dicing equipment: Disco DFD-6362 Blade: Disco NBC-2H 2050 27HECC Blade width: 0.025~0.030mm Blade tip exposure: 0.640~0.760mm Blade rotation speed: 35000 rpm ·Cutting speed: 60mm / sec Substrate cut depth: 20μm ·Cutting water amount: 1.0L / min ·Cutting water temperature: 20℃ Dicing size: 2.0mm square

[0140] Furthermore, the adhesive layer of the workpiece processing sheet was irradiated with ultraviolet light (UV) through the substrate 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.

[0141] Next, among the multiple chips obtained by the above dicing, one chip located near the center when the workpiece processing sheet is viewed in plan was picked up using a pickup device. Specifically, the chip was pushed up to a height of 500 μm from the substrate side of the workpiece processing sheet with a needle, while the surface of the chip opposite the workpiece processing sheet was adsorbed by a vacuum collet, thereby attempting to separate the chip from the workpiece processing sheet. The pick-up ability of the chip at this time was evaluated according to the following criteria regarding whether it could be separated. The results are shown in Table 1 as the pick-up ability of the active wafer. ○: The chip was separated. ×: The chip could not be separated.

[0142] Details of the abbreviations and other information in Table 1 are as follows: [monomer] 2EHA: 2-ethylhexyl acrylate VAc: Vinyl acetate HEA: 2-hydroxyethyl acrylate ACMO: Acryloylmorpholine BA: n-butyl acrylate MA: Methyl acrylate AAm: Acrylamide [Oligomers having active energy ray-curable groups] 5-9 functional acrylate: Pentaerythritol-based 5-9 functional urethane acrylate oligomer with weight average molecular weight of 2300 [Photopolymerization initiator] Omnirad 127: 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one (manufactured by IGM Resins, product name "Omnirad 127") Omnirad 184: 1-Hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins, product name "Omnirad 184") [Stabilizer] LA-52: Tetrakis(2,2,6,6-tetramethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate (N-methyl type hindered amine stabilizer, manufactured by ADEKA Corporation, product name "ADEKA STAB LA-52") LA-63P: Mixed ester of 1,2,3,4-butanetetracarboxylic acid with 1,2,2,6,6-pentamethyl-4-piperidinol and 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane (N-methyl type hindered amine stabilizer, manufactured by ADEKA Corporation, product name "ADEKA STAB LA-63P") AO-50: Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (hindered phenol stabilizer, manufactured by ADEKA Corporation, product name "ADEKA STAB AO-50") AO-60: Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (hindered phenol stabilizer, manufactured by ADEKA Corporation, product name "ADEKA STAB AO-60") 2112: Tris(2,4-ditert-butylphenyl)phosphite (phosphite stabilizer, manufactured by ADEKA Corporation, product name "ADEKA STAB 2112")

[0143] [Table 1]

[0144] As can be seen from Table 1, the workpiece processing sheet of the embodiment was able to exhibit excellent pick-up properties even when stored for a long period of time (7 days) after being attached to the active surface of a silicon wafer. [Industrial Applicability]

[0145] The workpiece processing sheet according to the present invention is suitably used as a dicing sheet for a workpiece having an active surface.

Claims

1. A workpiece processing sheet comprising a substrate and an adhesive layer laminated on one side of the substrate, the pressure-sensitive adhesive layer is made of an active energy ray-curable pressure-sensitive adhesive containing a hindered amine stabilizer, The workpiece processing sheet is intended to be attached to the ground surface of a workpiece within 120 minutes of having its surface ground. A workpiece processing sheet characterized by the above.

2. A workpiece processing sheet comprising a substrate and an adhesive layer laminated on one side of the substrate, the pressure-sensitive adhesive layer is made of an active energy ray-curable pressure-sensitive adhesive containing a hindered amine stabilizer, The surface of the adhesive layer opposite to the substrate is attached to a ground surface of a silicon wafer within 20 minutes after grinding the surface, to obtain a laminate of the workpiece processing sheet and the silicon wafer, The adhesive strength of the workpiece processing sheet to the silicon wafer after irradiating the adhesive layer with ultraviolet light immediately after the attachment is defined as F0, When the adhesive strength of the workpiece processing sheet to the silicon wafer after storing for 7 days from the application and then irradiating the adhesive layer with ultraviolet light is F7, The adhesive strength increase rate calculated as the ratio of F7 to F0 (F7 / F0) is 2.0 or less. A workpiece processing sheet characterized by the above.

3. 3. The workpiece processing sheet according to claim 1, wherein the hindered amine-based stabilizer is an N-alkyl type hindered amine-based stabilizer.

4. The workpiece processing sheet according to claim 1 or 2, characterized in that the active energy ray-curable adhesive is formed from an adhesive composition containing an acrylic polymer having an active energy ray-curable group introduced into its side chain and the hindered amine-based stabilizer.

5. a grinding step of grinding a surface of a workpiece; a sticking step of sticking the workpiece processing sheet according to claim 1 or 2 to the surface of the workpiece that has been ground; a dicing step of dicing the workpiece on the workpiece processing sheet to obtain a plurality of chips formed by dividing the workpiece; an active energy ray irradiation step of irradiating the pressure-sensitive adhesive layer of the workpiece processing sheet with active energy rays; a pick-up step of picking up the chips individually from the workpiece processing sheet; A method for manufacturing a machined workpiece, comprising:

6. The method for manufacturing a machined workpiece according to claim 5, characterized in that the attachment of the workpiece processing sheet to the workpiece in the attachment step is performed within 120 minutes from grinding the surface of the workpiece in the grinding step.

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