Workpiece processing sheet and method for manufacturing processed workpieces

Abstract

To provide a workpiece processing sheet that allows for easy separation of the workpiece even after heat treatment. [Solution] 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 formed from an adhesive composition containing an oxime ester-based photopolymerization initiator having a carbazole skeleton and a hindered amine-based stabilizer.

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 to a method for manufacturing a processed workpiece using the workpiece processing sheet. [Background technology]

[0002] A method for manufacturing a semiconductor device generally includes a dicing step of dicing a semiconductor wafer, which is a workpiece, onto a workpiece processing sheet to obtain multiple semiconductor chips, and a pickup step of individually picking up the obtained semiconductor chips from the workpiece processing sheet. The workpiece processing sheet described above usually comprises a base material and an adhesive layer provided on one side of the base material, and the workpiece is laminated on the side of the adhesive layer opposite to the base material (hereinafter sometimes referred to as the "adhesive surface").

[0003] In recent years, it has become increasingly common to perform heat treatment on workpieces before or after processing while they are laminated on a workpiece processing sheet. For example, workpieces on the workpiece processing sheet may undergo processes such as vapor deposition, sputtering, or baking for dehumidification, or heat tests may be conducted to confirm reliability in high-temperature environments. In such heat-intensive processes, problems can arise such as deformation of the workpiece processing sheet or fusion of the workpiece processing sheet to equipment. Therefore, there is consideration being given to imparting a certain level of heat resistance to workpiece processing sheets used in processes involving heat.

[0004] As an example of a heat-resistant adhesive sheet, Patent Document 1 discloses a sheet having an adhesive layer (adhesion resin layer) in which the gel fraction before and after heating satisfies predetermined conditions. Patent Document 2 also discloses a sheet having an adhesive layer having a specific range of rigidity (product of nanoindenter modulus and thickness at 25°C). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 6546378 [Patent Document 2] Patent No. 6887766 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, when the heat treatment described above is applied to the workpiece processing sheet, there is a problem in that the adhesive force to the workpiece increases, making it difficult to separate the workpiece processing sheet from the workpiece.

[0007] Generally, in workpiece processing sheets, the adhesive layer is composed of an active energy ray curable adhesive, and the adhesive layer is cured by irradiation with active energy rays, thereby reducing the adhesive strength to the workpiece and facilitating its separation. With workpiece processing sheets using such an active energy ray curable adhesive, the adhesive strength to the workpiece can be reduced to some extent even when the aforementioned heat treatment is performed.

[0008] However, heat treatment under more stringent conditions is also being considered. For example, heating to over 200°C, such as in a reflow process, is being explored. Under such stringent heating conditions, even workpiece processing sheets with active energy ray curability experience increased adhesion to the workpiece, making it difficult to separate the workpiece processing sheet from the workpiece.

[0009] This invention has been made in view of the above circumstances, and aims to provide a workpiece processing sheet that allows for easy separation of the workpiece even after heat treatment. [Means for solving the problem]

[0010] To achieve the above objective, 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 formed from an adhesive composition containing an oxime ester-based photopolymerization initiator having a carbazole skeleton and a hindered amine-based stabilizer (Invention 1).

[0011] 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 an oxime ester-based photopolymerization initiator having a carbazole skeleton and a hindered amine-based stabilizer. As a result, even after heat treatment, the curing reaction of the adhesive layer proceeds well by irradiation with active energy rays, thereby sufficiently reducing the adhesive strength. Therefore, even after heat treatment, the workpiece can be easily separated from the workpiece processing sheet.

[0012] In the above invention (Invention 1), the oxime ester-based photopolymerization initiator is the following formula (1) [ka] The structure is such that, in formula (1), at least one of R1 to R8 is an oxime ester-containing group, and the other R1 to R8 are, each, a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkanoyl group having 2 to 12 carbon atoms, a substituted or unsubstituted alkoxycarbonyl group having 2 to 12 carbon atoms, a substituted or unsubstituted cyclopentyl group, a substituted or unsubstituted cyclohexyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted benzoyl group, R9 is preferably one selected from a hydrogen atom, a C1-C12 alkyl group, a C2-C12 substituted or unsubstituted alkanoyl group, a C2-C12 substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted cyclopentyl group, a substituted or unsubstituted cyclohexyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted benzoyl group, and a substituted or unsubstituted phenoxycarbonyl group (Invention 2).

[0013] In the above invention (Invention 2), the oxime ester-containing group is the following formula (2) [ka] The structure is such that, in formula (2), X is a single bond, a carbonyl group, or a chemical structure that is bonded to the aromatic compound skeleton with or without a carbonyl group, and R 10 R is one selected from a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkanoyl group having 2 to 12 carbon atoms, a substituted or unsubstituted alkenoyl group having 4 to 6 carbon atoms that is not conjugated with a carbonyl group, a substituted or unsubstituted alkoxycarbonyl group having 2 to 6 carbon atoms, a substituted or unsubstituted benzoyl group, and a substituted or unsubstituted phenoxycarbonyl group. 11 It is preferable that this is an alkyl group having 1 to 12 carbon atoms, or a phenyl group (Invention 3).

[0014] In the above inventions (Inventions 1 to 3), the hindered amine stabilizer is preferably an N-alkyl type hindered amine stabilizer (Invention 4).

[0015] In the above inventions (Inventions 1 to 4), the substrate does not fuse to the contact object after being heated under the conditions of 260 °C for 10 minutes with the contact object placed on the surface of the substrate, and the contact object preferably does not change its state when heated under the above conditions (Invention 5).

[0016] In the above inventions (Inventions 1 to 5), the adhesive composition preferably contains an acrylic polymer having an active energy ray curable group introduced into its side chain (Invention 6).

[0017] In the above inventions (Inventions 1 to 6), it is preferably used in a workpiece processing method including a step of heating the workpiece processing sheet in a state where a workpiece before or after processing is laminated on the surface side of the adhesive layer opposite to the substrate (Invention 7).

[0018] Second, the present invention provides a method for manufacturing a processed workpiece, comprising: a bonding step of bonding a workpiece to the surface of the workpiece processing sheet (Inventions 1 to 7) on the side opposite to the substrate in the adhesive layer; a heating step of subjecting the workpiece, in a state where it is bonded to the workpiece processing sheet, to a treatment involving heating; and a dicing step of dicing the workpiece, which has been subjected to the treatment involving heating, on the workpiece processing sheet to obtain a processed workpiece in which the workpiece is separated into individual pieces (Invention 8).

Effects of the Invention

[0019] The workpiece processing sheet according to the present invention can easily separate the workpiece even when a heat treatment is performed.

Modes for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described. The workpiece processing sheet according to this embodiment comprises a base material and an adhesive layer laminated on one side of the base material. The adhesive is composed of an active energy ray curable adhesive formed from an adhesive composition containing an oxime ester-based photopolymerization initiator having a carbazole skeleton and a hindered amine-based stabilizer.

[0021] In the workpiece processing sheet according to this embodiment, the adhesive layer is composed of an active energy ray curable adhesive. By irradiating it with active energy rays, the adhesive layer is hardened, thereby reducing its adhesive strength to the workpiece. Therefore, when it is desired to separate the workpiece processing sheet according to this embodiment from the workpiece, it is possible to easily separate it while suppressing damage to the workpiece and preventing some of the adhesive constituting the adhesive layer from adhering to the workpiece (adhesive residue).

[0022] Furthermore, in the workpiece processing sheet according to this embodiment, the adhesive is formed from an adhesive composition containing an oxime ester-based photopolymerization initiator having a carbazole skeleton and a hindered amine-based stabilizer. Therefore, even if the workpiece processing sheet is heated (especially if the workpiece processing sheet is heated with workpieces stacked on top of it), it can be easily separated from the workpiece by subsequently irradiating it with active energy rays, as described above.

[0023] Conventionally, it was known that when a workpiece processing sheet was heat-treated while workpieces were stacked, the adhesive force to the workpieces increased, making it difficult to separate them. Furthermore, the inventors confirmed that even if the adhesive layer of the workpiece processing sheet was composed of an active energy ray curable adhesive, after heat treatment, not only did the adhesive force increase, but the hardening of the adhesive layer due to active energy ray irradiation (and the resulting decrease in adhesive force) itself became less likely to occur.

[0024] However, in the workpiece processing sheet according to this embodiment, even after heat treatment, it is possible to achieve good hardening of the adhesive layer (and the resulting decrease in adhesive strength) by irradiation with active energy rays. The following reasons are expected for this. However, this does not mean that the reasons are limited to those listed below, and the possibility of other reasons is not ruled out.

[0025] When an active energy ray-curable adhesive is heated, thermal decomposition (including depolymerization and various elimination reactions) and oxidation (including peroxide formation) occur in the polymers and additives constituting the adhesive, and active radicals are generated. These active radicals are thought to cause further decomposition and oxidation of the polymer, or to cause modification, deactivation, or thermal polymerization of sites that play an important role in active energy ray curing (especially carbon-carbon double bonds). However, in the workpiece processing sheet according to this embodiment, hindered amine-based stabilizers and stable radicals generated in the system from them are thought to trap or inactivate the active radicals and growth ends generated in the high-temperature environment as described above, thereby preventing the aforementioned modification of the active energy ray-curable adhesive.

[0026] In particular, hindered amine stabilizers trap (bind with) radicals, and then a reaction proceeds to cleave the radical portion again. The cleaved radical reacts with another radical to inactivate it, while the hindered amine stabilizer itself is regenerated. Therefore, hindered amine stabilizers can exert their stabilizing effect for a long period of time. This regenerative effect does not occur with conventionally used hindered phenol compounds.

[0027] Furthermore, the carbazole skeleton of the oxime ester-based photopolymerization initiator described above contributes to both improved quantum yield in light absorption and improved heat resistance as a molecule, due to its rigid structure. In addition, the oxime ester moiety efficiently generates radicals (e.g., alkyl radicals such as methyl radicals and ethyl radicals, and phenyl radicals) with high radical polymerization initiation efficiency in response to light irradiation. As a result, the curing reaction can proceed smoothly even in adhesive layers that have deteriorated to some extent due to exposure to high temperatures.

[0028] As described above, in the workpiece processing sheet according to this embodiment, even when the adhesive layer is cured by irradiation with active energy rays and then heat-treated, an excessive increase in adhesive strength is suppressed, and the workpiece can be separated well. In particular, even when the heat treatment is performed under harsh conditions, such as heating at 260°C for 10 minutes, good separation of the workpiece is possible.

[0029] 1. Base material The base material in this embodiment is not particularly limited, as long as it performs the desired function when used as a workpiece processing sheet. From the viewpoint of reducing the likelihood of malfunctions even when used in applications involving heat treatment, it is preferable that the base material has a predetermined heat resistance. For example, it is preferable that the base material according to this embodiment does not fuse to the contacting object after being heated at 260°C for 10 minutes with the contacting object placed on the surface of the base material. Here, the contacting object is something that does not change state when heated under the above conditions, and is, for example, a mesh or plate made of metal or the like that constitutes a conveyor that passes through a furnace, a plate made of glass or the like that is used as a support when it is placed in the furnace, a table or stage made of ceramics or the like, etc.

[0030] Furthermore, from the viewpoint of facilitating the efficient curing reaction of the adhesive layer, the substrate according to this embodiment is preferably transparent to active energy rays, and particularly preferably transparent to ultraviolet light. For example, the substrate according to this embodiment is preferably transparent to light rays with a wavelength of at least 405 nm, and more preferably transparent to light rays with a wavelength of 365 nm. In this case, the transmittance of light rays with a wavelength of 405 nm is preferably 30% or more, particularly preferably 50% or more, and even more preferably 75% or more. The upper limit of the transmittance of light rays with a wavelength of 405 nm is not particularly limited, and is, for example, 100% or less. Similarly, the transmittance of light rays with a wavelength of 365 nm is preferably 30% or more, particularly preferably 50% or more, and even more preferably 75% or more. The upper limit of the transmittance of light rays with a wavelength of 365 nm is not particularly limited, and is, for example, 100% or less.

[0031] The substrate according to this embodiment is preferably made of a resin, from the viewpoint of easily achieving the heat resistance and permeability described above. Examples of such resins include polyamides; polyimides; polyether ether ketones; 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 copolymers; ethylene copolymer resins such as ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylate methyl copolymers, and other ethylene-(meth)acrylic acid ester copolymers; polyvinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers; (meth)acrylic acid ester copolymers; polyurethanes; polystyrene; polycarbonates; and fluororesins. Furthermore, the resin constituting the substrate may be a crosslinked version of the above-mentioned resins or a modified version such as an ionomer of the above-mentioned resins. In this specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the term "polymer" in this specification also includes the concept of "polymer."

[0032] Among the above, the substrate according to this embodiment is preferably composed of at least one of polyamide, polyimide, and polyetheretherketone, from the viewpoint of having excellent heat resistance and being able to easily achieve good permeability.

[0033] The substrate in this embodiment may be a single-layer film made of the resin described above, or it may be a laminated film formed by laminating multiple such films. In this laminated film, the materials constituting each layer may be of the same type or different types.

[0034] Furthermore, the base material may contain various additives such as flame retardants, plasticizers, antistatic agents, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers. While there are no particular limitations on the content of these additives, it is preferable to keep it within a range that allows the base material to exhibit the desired function.

[0035] The surface of the substrate to which the adhesive layer is laminated may be subjected to surface treatments such as primer treatment, corona treatment, or plasma treatment in order to improve adhesion with the adhesive layer.

[0036] The thickness of the base material can be appropriately set depending on the method in which the workpiece processing sheet is used, but it is preferably 200 μm or less, and particularly preferably 150 μm or less. Furthermore, the thickness of the base material is preferably 10 μm or more, and particularly preferably 25 μm or more.

[0037] 2. Adhesive layer As described above, the adhesive layer in this embodiment is composed of an active energy ray curable adhesive formed from an adhesive composition containing an oxime ester-based photopolymerization initiator having a carbazole skeleton and a hindered amine-based stabilizer.

[0038] Examples of the above-mentioned adhesives are not limited to acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, polyvinyl ether adhesives, etc. However, it is preferable to use acrylic adhesives because they are easy to form into active energy ray curable adhesives and easily exhibit the desired adhesive strength.

[0039] Furthermore, the above-mentioned active energy ray curable adhesive may be mainly composed of a polymer having active energy ray curability, or it may be mainly composed of a mixture of an active energy ray non-curable polymer (a polymer that does not have active energy ray curability) and a monomer and / or oligomer having at least one active energy ray curable group. Moreover, the active energy ray curable adhesive may be a mixture of an active energy ray curable polymer and a monomer and / or oligomer having at least one active energy ray curable group. Among these, in this embodiment, the active energy ray curable adhesive is preferably mainly composed of an active energy ray curable polymer (particularly an active energy ray curable acrylic polymer) from the viewpoint of suppressing adverse effects due to excessive increase in adhesive strength even after heat treatment and facilitating good work separation by reducing adhesive strength using a trigger.

[0040] The acrylic polymer having active energy ray curability described above is preferably an acrylic polymer in which an active energy ray curable functional group (active energy ray curable group) is introduced into the side chain (hereinafter sometimes referred to as "active energy ray curable polymer (A)"). In this case, the adhesive composition in this embodiment preferably contains the above-mentioned photopolymerization initiator and hindered amine-based stabilizer, along with an acrylic polymer in which an active energy ray curable group is introduced into the side chain (active energy ray curable polymer (A)).

[0041] (1) Active energy ray curable polymer (A) The above-mentioned active energy ray 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 that functional group.

[0042] As the functional group-containing monomers mentioned above, monomers having a polymerizable double bond and a functional group such as a hydroxyl group, carboxyl group, amino group, amide group, benzyl group, or glycidyl group within the molecule are preferred, and among these, monomers containing a hydroxyl group as a functional group (hydroxyl group-containing monomers) are preferred.

[0043] Examples of the above-mentioned hydroxyl 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. Among these, it is preferable to use at least one of 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate. These can be used individually or in combination of two or more.

[0044] Examples of the carboxyl group-containing monomers mentioned above include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used individually or in combination of two or more.

[0045] Examples of the above-mentioned amino group-containing monomers or amide group-containing monomers include (meth)acrylate aminoethyl and (meth)acrylate n-butylaminoethyl. These may be used individually or in combination of two or more.

[0046] The (meth)acrylic acid ester polymer (a1) preferably contains 5% by mass or more of the structural units derived from the functional group-containing monomer, and more preferably 10% by mass or more. Furthermore, the (meth)acrylic acid ester polymer (a1) preferably contains 40% by mass or less of the structural units derived from the functional group-containing monomer, and more preferably 35% by mass or less. By containing the functional group-containing monomer within the above ranges, the (meth)acrylic acid ester polymer (a1) is more likely to form the desired active energy ray-curable polymer (A).

[0047] From the viewpoint of easily forming an adhesive with desired performance, the (meth)acrylic acid ester polymer (a1) may also contain an alkyl (meth)acrylate as a monomer unit constituting the (meth)acrylic acid ester polymer (a1). The alkyl (meth)acrylate is preferably one in which the alkyl group has 1 to 18 carbon atoms, and particularly preferably one in which it has 1 to 8 carbon atoms.

[0048] Specific examples of the alkyl (meth)acrylate esters mentioned above 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 individually or in combination of two or more. Among the alkyl (meth)acrylate esters mentioned above, 2-ethylhexyl (meth)acrylate is preferred, and 2-ethylhexyl acrylate is particularly preferred.

[0049] The (meth)acrylic acid ester polymer (a1) preferably contains 20% by mass or more of the constituent units derived from the above-mentioned alkyl (meth)acrylic acid ester, and more preferably 40% by mass or more. Furthermore, the (meth)acrylic acid ester polymer (a1) preferably contains 95% by mass or less of the constituent units derived from the above-mentioned alkyl (meth)acrylic acid ester, and more preferably 85% by mass or less. By containing the alkyl (meth)acrylic acid ester in the above ranges in the (meth)acrylic acid ester polymer (a1), the workpiece processing sheet 1 is more likely to exhibit the desired adhesive strength.

[0050] The (meth)acrylic acid ester polymer (a1) preferably contains nitrogen atom-containing monomers as monomer units constituting the (meth)acrylic acid ester polymer (a1). This allows the workpiece to be held better on the workpiece processing sheet during processing, and also makes it easier to suppress an excessive increase in adhesive force to the workpiece when the workpiece processing sheet is heated. Examples of nitrogen atom-containing monomers include monomers having an amino group, monomers having an amide group, and monomers having a nitrogen-containing heterocycle, with monomers having a nitrogen-containing heterocycle being preferred.

[0051] Examples of monomers 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. Among these, N-(meth)acryloylmorpholine is preferred, and N-acryloylmorpholine is particularly preferred.

[0052] The (meth)acrylic acid ester polymer (a1) preferably contains 3% by mass or more of the constituent units derived from the nitrogen atom-containing monomer, more preferably 5% by mass or more, and even more preferably 8% by mass or more. Furthermore, the (meth)acrylic acid ester polymer (a1) preferably contains 12% by mass or less of the constituent units derived from the nitrogen atom-containing monomer, more preferably 11% by mass or less, and even more preferably 10% by mass or less. By containing nitrogen atom-containing monomers within the above ranges in the (meth)acrylic acid ester polymer (a1), the workpiece can be held more securely on the workpiece processing sheet during processing, and when the workpiece processing sheet is heated, it becomes easier to suppress an excessive increase in adhesive strength to the workpiece.

[0053] The (meth)acrylic acid ester polymer (a1) may contain other monomers as constituent monomer units, in addition to the functional group-containing monomers, alkyl (meth)acrylates, and nitrogen atom-containing monomers described above.

[0054] Examples of other monomers mentioned above include 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-crosslinked acrylamides such as (meth)acrylamide and N,N-dimethyl(meth)acrylamide; non-crosslinked (meth)acrylic acid esters having a tertiary amino group such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate; vinyl acetate; and styrene.

[0055] The polymerization mode of the (meth)acrylic acid ester polymer (a1) may be a random copolymer or a block copolymer. Furthermore, the polymerization method is not particularly limited and can be polymerized by a general polymerization method, such as solution polymerization.

[0056] A (meth)acrylic acid ester polymer (a1) having the above-mentioned functional group-containing monomer units is reacted with an unsaturated group-containing compound (a2) having a functional group bonded to that functional group to obtain an active energy ray-curable polymer (A).

[0057] 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, if 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 azilidinyl group. If 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 azilidinyl group.

[0058] Furthermore, the above-mentioned unsaturated group-containing compound (a2) contains at least one, preferably 1 to 6, and more preferably 1 to 4, active energy ray polymerizable carbon-carbon double bonds per molecule. Specific examples of such unsaturated group-containing compounds (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; and diisocyanate compounds. Examples include acryloyl monoisocyanate compounds obtained by the reaction of a polyisocyanate compound with hydroxyethyl (meth)acrylate; acryloyl monoisocyanate compounds obtained by the reaction of a diisocyanate compound or 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, etc.

[0059] The above unsaturated group-containing compound (a2) is used in a ratio of preferably 50 mol% or more, particularly preferably 60 mol% or more, and even more preferably 70 mol% or more, relative to the number of moles of the functional group-containing monomer in the above (meth)acrylic acid ester polymer (a1). Furthermore, the above unsaturated group-containing compound (a2) is used in a ratio of preferably 95 mol% or less, particularly preferably 93 mol% or less, and even more preferably 90 mol% or less, relative to the number of moles of the functional group-containing monomer in the above (meth)acrylic acid ester polymer (a1).

[0060] 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 depending on the combination of functional groups present in the (meth)acrylic acid ester polymer (a1) and the functional groups present in the unsaturated group-containing compound (a2). As a result, the functional groups present in the (meth)acrylic acid ester polymer (a1) react with the functional groups in the unsaturated group-containing compound (a2), introducing unsaturated groups into the side chains of the (meth)acrylic acid ester polymer (a1), and yielding an active energy ray-curable polymer (A).

[0061] The weight-average molecular weight (Mw) of the activated energy ray-curable polymer (A) obtained in this manner is preferably 10,000 or more, particularly preferably 150,000 or more, and even more preferably 200,000 or more. Furthermore, the weight-average molecular weight (Mw) is preferably 1,500,000 or less, and particularly preferably 1,000,000 or less.

[0062] (2) Oxime ester photopolymerization initiators having a carbazole skeleton The photopolymerization initiator described above in this embodiment is not particularly limited as long as it has a carbazole skeleton and is of the oxime ester type. In particular, the oxime ester type photopolymerization initiator in this embodiment is of the following formula (1) [ka] It is preferable that it has the following structure.

[0063] In formula (1) above, at least one of R1 to R8 is an oxime ester-containing group. Furthermore, each of R1 to R8 other than the oxime ester-containing group is selected from a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkanoyl group having 2 to 12 carbon atoms, a substituted or unsubstituted alkoxycarbonyl group having 2 to 12 carbon atoms, a substituted or unsubstituted cyclopentyl group, a substituted or unsubstituted cyclohexyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted benzoyl group, and a substituted or unsubstituted phenoxycarbonyl group. Here, if it is an alkyl group, its carbon number is preferably 1 to 3, and specifically, it is preferably selected from a methyl group, an ethyl group, and a propyl group.

[0064] In formula (1) above, R9 is selected from a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkanoyl group having 2 to 12 carbon atoms, a substituted or unsubstituted alkoxycarbonyl group having 2 to 12 carbon atoms, a substituted or unsubstituted cyclopentyl group, a substituted or unsubstituted cyclohexyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted benzoyl group, and a substituted or unsubstituted phenoxycarbonyl group. Here, if it is an alkyl group, the number of carbon atoms is preferably 1 to 3, and specifically, it is preferably selected from a methyl group, an ethyl group, and a propyl group.

[0065] The above oxime ester-containing group is not particularly limited as long as it contains an oxime ester structure, but is especially true for the following formula (2) [ka] It is preferable that the structure is as follows. In formula (2), X is preferably a single bond, a carbonyl group, or a chemical structure that is bonded to the aromatic compound skeleton with or without a carbonyl group. Also, in formula (2), R 10R is one selected from a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkanoyl group having 2 to 12 carbon atoms, a substituted or unsubstituted alkenoyl group having 4 to 6 carbon atoms that is not conjugated to a carbonyl group, a substituted or unsubstituted alkoxycarbonyl group having 2 to 6 carbon atoms, a substituted or unsubstituted benzoyl group, and a substituted or unsubstituted phenoxycarbonyl group. 10 If it is an alkyl group, the number of carbon atoms is preferably 1 to 3, and specifically, it is preferably one selected from a methyl group, an ethyl group, and a propyl group. Furthermore, R 11 This is an alkyl group having 1 to 12 carbon atoms, or a phenyl group.

[0066] In this embodiment, it is preferable to use, for example, the product name "NikkacureTG-05" or "NikkacureTG-10" commercially available from Nippon Chemical Industries, Ltd., or the product name "Irgacure OXE02" commercially available from BASF Japan as the photopolymerization initiator.

[0067] The content of the oxime ester-based photopolymerization initiator having a carbazole skeleton in the adhesive composition is preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, per 100 parts by mass of the active energy ray-curable polymer (A). Furthermore, the content is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less. By having the above-mentioned range for the photopolymerization initiator content, the adhesive layer can be efficiently cured by irradiation with active energy rays, thereby making it easier to effectively reduce the adhesive strength of the workpiece processing sheet to the adherend.

[0068] (3) Hindered amine stabilizers In this specification, a hindered amine stabilizer refers to a stabilizer having one or more amine skeletons in its molecule. The hindered amine stabilizer in this embodiment is not particularly limited as long as it has such a structure.

[0069] Furthermore, generally speaking, hindered amine stabilizers include N-alkyl type hindered amine stabilizers, which are compounds having one or more alkyl groups bonded to the nitrogen atom of the 2,2,6,6-tetramethylpiperidine skeleton in their molecule, and NH-type hindered amine stabilizers, which are compounds having one or more hydrogen atoms bonded to the nitrogen atom of the 2,2,6,6-tetramethylpiperidine skeleton in their molecule. In the workpiece processing sheet according to this embodiment, good effects can be obtained regardless of which of these compounds is used, but from the viewpoint of easily reducing the adhesive strength to the workpiece after heating and irradiation with active energy rays, it is preferable to use an N-alkyl type hindered amine stabilizer.

[0070] Examples of alkyl groups in the above-mentioned N-alkyl type hindered amine stabilizers 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 easily reducing the adhesiveness to the workpiece after heating and irradiation with active energy rays.

[0071] Specific examples of hindered amine stabilizers 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, and p,p-Tol Ensulfonylaminodiphenylamine, N-phenyl-N'-(3-methchlorolyloxy-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 diphenylamine, dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly[[6-(1,1,3,3-tetramethylpiperidine] (Methylbutyl)amino-1,3,5-triazine-2,4-diyl[(2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino]], 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-octyroxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl 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-butanetetracarboxylate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate, 1,2,3,4-butanetetracarboxylic acid and 1,2,Mixed esterified product of 2,6,6-pentamethyl-4-piperidinol and 1-tridecanol, mixed esterified product of 1,2,3,4-butanetetracarboxylic acid and 2,2,6,6-tetramethyl-4-piperidinol and 1-tridecanol, 1,2,3,4-butanetetracarboxylic acid and 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 Examples include mixed esterified products of 1,2,3,4-butanetetracarboxylic acid, 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-propylene carboxylate, (1,2,2,6,6-pentamethyl-4-piperidyl)-2-propylene carboxylate, etc.

[0072] Among the specific examples above, it is preferable to use tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate as an N-alkyl type hindered amine stabilizer, and at least one of a mixed ester of 1,2,3,4-butanetetracarboxylic acid, 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 type hindered amine stabilizer.

[0073] Furthermore, the molar mass of the hindered amine stabilizer is preferably 200 g / mol or more, particularly preferably 600 g / mol or more, and even more preferably 1000 g / mol or more. Also, the molar mass is preferably 10000 g / mol or less, particularly preferably 5000 g / mol or less, and even more preferably 3000 g / mol or less. Having the molar mass of the hindered amine stabilizer within these ranges makes it easier to effectively reduce the adhesion to the workpiece after heating and irradiation with active energy rays.

[0074] The content of the hindered amine stabilizer in the aforementioned adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and more preferably 1.0 part by mass or more, per 100 parts by mass of the acrylic polymer (active energy ray curable polymer (A)) in which an active energy ray curable group is introduced into the side chain. Furthermore, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and more preferably 15 parts by mass or less. Having the hindered amine stabilizer content within these ranges makes it easier to effectively reduce the adhesive strength to the workpiece after heating and irradiation with active energy rays.

[0075] (4) Crosslinking agent The adhesive composition described above may also preferably contain a crosslinking agent. The inclusion of a crosslinking agent in the adhesive composition allows the active energy ray-curable polymer (A) to crosslink in the adhesive layer, forming a good three-dimensional network structure. This further improves the cohesive strength of the resulting adhesive, effectively suppressing the generation of adhesive residue in the workpiece separated from the workpiece processing sheet after irradiation with active energy rays. When the adhesive composition contains a crosslinking agent, the active energy ray-curable polymer (A) preferably contains the above-mentioned functional group-containing monomers as monomer units constituting the polymer, and in particular, it is preferable to contain functional group-containing monomers having functional groups that are highly reactive with the crosslinking agent used.

[0076] Examples of the above crosslinking agents 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 present in the acrylic copolymer. These crosslinking agents can be used individually or in combination of two or more.

[0077] The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of polyisocyanate compounds 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 their biuret and isocyanurate forms, as well as adducts which are reaction products with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, trimethylolpropane-modified tolylene diisocyanate is preferred.

[0078] When the aforementioned adhesive composition contains a crosslinking agent, the amount of crosslinking agent in the adhesive composition is preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, and even more preferably 0.10 parts by mass or more, per 100 parts by mass of the active energy ray curable polymer (A). Furthermore, the amount is preferably 30 parts by mass or less, and particularly preferably 5 parts by mass or less. A crosslinking agent content of 0.01 parts by mass or more makes it easier to improve the cohesive force of the adhesive layer after irradiation with active energy rays, thereby effectively suppressing adhesive residue. Furthermore, a crosslinking agent content of 30 parts by mass or less results in an appropriate degree of crosslinking, making it easier for the adhesive layer to exhibit the desired adhesive strength.

[0079] (5) Other ingredients The aforementioned adhesive composition may contain desired additives, such as silane coupling agents, antistatic agents, tackifiers, antioxidants, softeners, fillers, refractive index adjusters, etc., as long as they do not impair the effects of the workpiece processing sheet according to this embodiment.

[0080] (6) Method for preparing an adhesive composition The adhesive composition in this embodiment can be produced by manufacturing an active energy ray-curable polymer (A), and mixing the obtained active energy ray-curable polymer (A) with an oxime ester-based photopolymerization initiator having a carbazole skeleton, a hindered amine-based stabilizer, and optionally a crosslinking agent and a desired additive. At this time, a diluent solvent may be added optionally to obtain a coating solution of the adhesive composition.

[0081] Examples of the diluent solvents used 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 solvents such as ethyl cellosolve.

[0082] The concentration and viscosity of the coating solution prepared in this manner are not particularly limited as long as they are within the range of coating, and can be appropriately selected depending on the situation. For example, the adhesive composition is diluted to a concentration of 10% by mass or more and 60% by mass or less. Note that the addition of a diluent is not a necessary condition when obtaining the coating solution; if the adhesive composition has a viscosity suitable for coating, a diluent may not be added. In this case, the adhesive composition becomes a coating solution in which the polymerization solvent of the acrylic copolymer (a1) is used directly as the diluent.

[0083] (7) Thickness of the adhesive layer 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. A thickness of 1 μm or more in the adhesive layer makes it easier for the workpiece processing sheet to exhibit good adhesion and helps suppress chip breakage. Furthermore, the thickness is preferably 50 μm or less, particularly preferably 30 μm or less, and even more preferably 20 μm or less. A thickness of 50 μm or less in the adhesive layer makes it easier to separate the workpiece.

[0084] 3. Other components In the workpiece processing sheet according to this embodiment, a release sheet may be laminated on the side of the adhesive layer opposite to the substrate (the adhesive side) for the purpose of protecting that side until it is attached to the workpiece.

[0085] The composition of the release sheet described above is arbitrary, and examples include plastic films that have been treated with a release agent. 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. As the release agent, silicone-based, fluorine-based, long-chain alkyl, and rubber-based agents can be used, and among these, silicone-based agents are preferred because they are inexpensive and provide stable performance.

[0086] There are no particular restrictions on the thickness of the release sheet mentioned above; for example, it may be between 16 μm and 250 μm.

[0087] Furthermore, in the workpiece processing sheet according to this embodiment, an adhesive layer may be laminated on the side 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. With this sheet, a workpiece can be attached to the side of the adhesive layer opposite to the adhesive layer, and by dicing the adhesive layer together with the workpiece, a chip can be obtained in which individual pieces of the adhesive layer are laminated. The chip can be easily fixed to the object on which it is mounted by these individual pieces of adhesive layer. As the material constituting the adhesive layer described above, it is preferable to use one that contains a thermoplastic resin and a low molecular weight thermosetting adhesive component, or one that contains a B-stage (semi-cured) thermosetting adhesive component.

[0088] 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 protective film forming and dicing sheet. With such a sheet, a workpiece is attached to the side 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 with individual pieces of the protective film forming layer laminated on it. Preferably, a workpiece with a circuit formed on one side is used, and in this case, the protective film forming layer is usually laminated on the side opposite to the side with the circuit formed. By curing the individual pieces of the protective film forming layer at a predetermined timing, a protective film with sufficient durability can be formed on the chip. Preferably, the protective film forming layer is made of an uncured curable adhesive.

[0089] 4. Physical properties of workpiece processing sheets In the workpiece processing sheet according to this embodiment, before heating and before irradiation with active energy rays (at 23°C, with a light intensity of 0 mJ / cm²), the following conditions are met: 2 The adhesive force to the silicon wafer (the mirror surface of a silicon wafer that has been mirror-finished, the same applies hereinafter) in the ) is preferably 200 mN / 25 mm or more, particularly preferably 800 mN / 25 mm or more, and even more preferably 2000 mN / 25 mm or more. Having an adhesive force of 200 mN / 25 mm or more makes it easier to securely fix the workpiece onto the workpiece processing sheet and makes it easier to prevent unintended detachment of the workpiece (especially after it has been pieced) (especially chip flying off). The upper limit of the adhesive force is not particularly limited, but for example, it is preferably 30000 mN / 25 mm or less, particularly preferably 25000 mN / 25 mm or less, and even more preferably 22000 mN / 25 mm or less.

[0090] In the workpiece processing sheet according to this embodiment, before heating and with a light intensity of 200 mJ / cm² 2 After irradiation with activated energy rays (at 23°C, light intensity 200 mJ / cm²) 2The adhesive force to the silicon wafer in is preferably 1500 mN / 25 mm or less, particularly preferably 600 mN / 25 mm or less, and even more preferably 200 mN / 25 mm or less. In the work processing sheet according to this embodiment, since the adhesive layer is composed of an active energy ray curable adhesive, it becomes easy to achieve the above-described adhesive force after irradiation with active energy rays. And when the said adhesive force is 1500 mN / 25 mm or less, it becomes easy to peel a work from the work processing sheet. Further, the adhesive force is preferably 10 mN / 25 mm or more, particularly preferably 25 mN / 25 mm or more, and even more preferably 35 mN / 25 mm or more. Thereby, it becomes easy to suppress the separation and dropping of the work at an unintended stage after irradiation with active energy rays.

[0091] Furthermore, in the work processing sheet according to this embodiment, after heating at 260° C. for 10 minutes and then irradiating with active energy rays at a light amount of 1000 mJ / cm 2 (260° C. heating for 10 minutes, light amount 1000 mJ / cm 2 ) the adhesive force to the silicon wafer is preferably 1500 mN / 25 mm or less, more preferably 1000 mN / 25 mm or less, particularly preferably 800 mN / 25 mm or less, and even more preferably 600 mN / 25 mm or less. In the work processing sheet according to this embodiment, by using an oxime ester-based photopolymerization initiator having a carbazole skeleton and a hindered amine-based stabilizer in combination, even after heating, it becomes easy to reduce the adhesive force after irradiation with active energy rays to the above range. And when the said adhesive force is 1500 mN / 25 mm or less, it becomes easy to peel a work from the work processing sheet. Further, the adhesive force is preferably 10 mN / 25 mm or more, particularly preferably 25 mN / 25 mm or more, and even more preferably 35 mN / 25 mm or more. Thereby, it becomes easy to suppress the separation and dropping of the work at an unintended stage after irradiation with active energy rays.

[0092] Further details regarding the adhesive strength measurement method are described in the test examples below.

[0093] 5. Method for manufacturing workpiece processing sheets The method for manufacturing the workpiece processing sheet according to this embodiment is not particularly limited, and is preferably manufactured by laminating an adhesive layer on one side of a base material.

[0094] Lamination of an adhesive layer onto one side of a substrate can be carried out by known methods. For example, it is preferable to transfer an adhesive layer formed on a release sheet to one side of the substrate. In this case, a coating liquid containing an adhesive composition constituting the adhesive layer, and optionally a solvent or dispersion medium, is prepared, and the coating liquid is applied to the peeled 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, roll knife coater, applicator, etc. to form a coating film, and the adhesive layer can be formed by drying the coating film. The properties of the coating liquid are not particularly limited as long as it can be applied, and it may contain components for forming the adhesive layer as a solute or as a dispersed phase. The release sheet in this laminate may be peeled off as a process material, or it may be used to protect the adhesive surface of the adhesive layer until the workpiece processing sheet is attached to the adherend.

[0095] If the coating liquid for forming the adhesive layer contains a crosslinking agent, the crosslinking reaction between the active energy ray-curable polymer (A) and the crosslinking agent in the coating film can be promoted by changing the drying conditions (temperature, time, etc.) or by providing a separate heat treatment, thereby forming a crosslinked structure at a desired density in the adhesive layer. To ensure this crosslinking reaction progresses sufficiently, after laminating the adhesive layer onto the substrate by the method described above, the resulting workpiece processing sheet may be cured by, for example, leaving it undisturbed in an environment of 23°C and 50% relative humidity for several days.

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

[0097] 6. How to use the workpiece processing sheet The workpiece processing sheet according to this embodiment is preferably used for processing workpieces such as semiconductor wafers. In this case, after attaching the adhesive surface of the workpiece processing sheet according to this embodiment to the workpiece, processing of the workpiece can be performed on the workpiece processing sheet. Depending on the processing, the workpiece processing sheet according to this embodiment can be used as a backgrind sheet, dicing sheet, expand sheet, pickup sheet, etc. Examples of workpieces include semiconductor wafers, semiconductor components such as semiconductor packages, and glass components such as glass plates.

[0098] As described above, the workpiece processing sheet according to this embodiment can effectively reduce its adhesive strength to the workpiece by irradiation with active energy rays, even after heat treatment. This allows for easy separation of the workpiece. Therefore, the workpiece processing sheet according to this embodiment is particularly suitable for use in a workpiece processing method that includes a step of heating the workpiece processing sheet with the workpiece before or after processing laminated on the adhesive side.

[0099] For example, the workpiece processing sheet according to this embodiment can be suitably used in a method for manufacturing a processed workpiece, which comprises a bonding step of bonding a workpiece to the side of the adhesive layer of the sheet opposite to the substrate, a heating step of subjecting the workpiece, while bonded to the workpiece processing sheet, to a heat-inducing treatment, and a dicing step of dicing the workpiece that has been subjected to the heat-inducing treatment on the workpiece processing sheet to obtain a processed workpiece in which the workpiece has been divided into individual pieces.

[0100] Furthermore, in the above-described method for manufacturing processed workpieces, the processed workpieces obtained by the dicing process can be appropriately separated from the workpiece processing sheet. For example, the above manufacturing method may also preferably include an active energy ray irradiation step in which active energy rays are irradiated onto the adhesive layer of the workpiece processing sheet to which the processed workpieces are bonded to, thereby curing the adhesive layer, and a pickup step in which the processed workpieces are picked up from the workpiece processing sheet having the cured adhesive layer.

[0101] The bonding process, dicing process, active energy ray irradiation process, and pickup process described above can each be carried out by known methods. Furthermore, there are no particular limitations on the heating process described above; for example, treatments such as vapor deposition, sputtering, and baking can be performed on the workpiece before or after processing, or heating tests can be conducted to confirm reliability in high-temperature environments.

[0102] The heating conditions in the above heating process can be set appropriately according to the purpose of heating. For example, the heating temperature may be 80°C or higher, particularly 100°C or higher, and even 110°C or higher. The temperature may also be, for example, 300°C or lower, particularly 270°C or lower, and even 200°C or lower. The heating time may be, for example, 10 minutes or more, particularly 30 minutes or more, and even 120 minutes or more. The heating time may also be, for example, 25 hours or less, particularly 10 hours or less, and even 5 hours or less. As for the heating equipment, an equipment suitable for the purpose of heating can be used, for example, an oven, a heatable table, etc.

[0103] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Accordingly, 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.

[0104] For example, other layers may be provided between the substrate and the adhesive layer, or on the surface of the substrate opposite to the adhesive layer. [Examples]

[0105] 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.

[0106] [Example 1] (1) Preparation of adhesive composition A (meth)acrylic acid ester polymer was obtained by polymerizing 60 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of N-acryloylmorpholine, and 30 parts by mass of 2-hydroxyethyl acrylate using a solution polymerization method. The weight-average molecular weight of the (meth)acrylic acid ester polymer was measured by the method described later and was found to be 500,000.

[0107] The obtained (meth)acrylic acid ester polymer was reacted with methacryloyloxyethyl isocyanate (MOI) in an amount equivalent to 90 mol% of the 2-hydroxyethyl acrylate that constitutes the (meth)acrylic acid ester polymer to obtain an acrylic polymer (active energy ray curable polymer) in which active energy ray curable groups were introduced into the side chains. The weight-average molecular weight (Mw) of the active energy ray curable polymer was measured by the method described later and was found to be 500,000.

[0108] The obtained active energy ray curable polymer is 100 parts by mass (based on solid content, the same applies hereinafter), 1.6 parts by mass of trimethylolpropane-modified hexamethylene diisocyanate as a crosslinking agent, and an oxime ester-based photopolymerization initiator having a carbazole skeleton (manufactured by Nippon Chemical Industries, Ltd., product name "Nikkacure") as a photopolymerization initiator. 0.3 parts by mass of "TG-10" (maximum absorption wavelength: 345 nm; melting point: 110~150°C) and 1 part by mass of a mixed ester of 1,2,3,4-butanetetracarboxylic acid, 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 (manufactured by ADEKA, product name "ADEKA Stab LA-63P", N-methyl type hindered amine stabilizer) were mixed in a solvent to obtain a coating solution of the adhesive composition (solid content concentration 30% by mass).

[0109] (2) Formation of the adhesive layer A release sheet (Lintec Corporation, product name "SP-PET381031"), which has a silicone-based release agent layer formed on one side of a 38 μm thick polyethylene terephthalate film, was coated with the adhesive composition solution obtained in step (2) above, and dried by heating, thereby obtaining a laminate in which a 10 μm thick adhesive layer was formed on the release sheet.

[0110] (3) Preparation of adhesive sheets One side of a polyamide film (manufactured by Unitika, product name "Uniamide EX-50", thickness: 50 μm) used as a base material was bonded to the adhesive layer side of the laminate obtained in step (2) above. The laminate was then stored in a light-shielded environment at 23°C and 50% humidity for 10 days. This yielded a sheet for workpiece processing.

[0111] Furthermore, when the above substrate was heated at 260°C for 10 minutes with a metal plate placed on its surface as a contact object, a test was conducted to confirm whether or not it fused to the contact object (hereinafter sometimes referred to as the "fusion test"), and it was confirmed that it did not fuse. In addition, the light transmittance of the above substrate at wavelengths of 365 nm and 405 nm was measured to be 85% and 88%, respectively.

[0112] (4) Measurement of weight-average molecular weight (Mw) The weight-average molecular weight (Mw) mentioned above is the weight-average molecular weight in polystyrene terms, measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement). <Measurement conditions> • GPC measuring device: Tosoh Corporation, HLC-8320 • GPC column (passes through in the following order): Manufactured by Tosoh Corporation TSK Gel Super H-H TSK gel superHM-H TSK Gel Super H2000 • Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0113] [Examples 2-5, Comparative Examples 1-6] A sheet for workpiece processing was obtained in the same manner as in Example 1, except that the base material, the composition of the active energy ray-curable polymer, the content of the crosslinking agent, the type and content of the photopolymerization initiator, and the type and content of the hindered amine-based stabilizer were changed as shown in Table 1.

[0114] Further details regarding the abbreviations and other terms listed in Table 1 are as follows: [Base material] Polyamide: Polyamide film (Unitika Corporation, product name "Uniamide EX-50", thickness: 50 μm, fusion test: did not fuse, 365 nm light transmittance: 85%, 405 nm light transmittance: 88%) Polyimide: Polyimide film (IST Corporation, product name "Tohmed Type C", thickness: 25 μm, fusion test: no fusion, 365 nm light transmittance: 0.4%, 405 nm light transmittance: 60%) PEEK: Polyether ether ketone film (manufactured by Kurabo Industries Ltd., product name "Expeak", thickness: 25 μm, fusion test: did not fuse, 365 nm light transmittance: 0.3%, 405 nm light transmittance: 72%) [Activated energy ray curing polymer] 2EHA: 2-ethylhexyl acrylate ACMO:N-Acryloylmorpholin HEA: 2-hydroxyethyl acrylate BA: n-butyl acrylate MMA: Methyl methacrylate MOI: Methacryloyloxyethyl isocyanate [Photopolymerization initiator] Nikkacure TG-10: Oxime ester-based photopolymerization initiator with a carbazole skeleton (manufactured by Nippon Chemical Industries, Ltd., product name "Nikkacure TG-10", maximum absorption wavelength: 345 nm; melting point: 110~150°C) Nikkacure TG-05: Oxime ester-based photopolymerization initiator with a carbazole skeleton (manufactured by Nippon Chemical Industries, Ltd., product name "Nikkacure TG-5", maximum absorption wavelength: 344 nm; melting point: 184~190°C) Omnirad 127: 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]phenyl}-2-methylpropan-1-one (manufactured by IGM Resins, product name "Omnirad 127") Omnirad TPO: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (manufactured by IGM Resins, product name "OMNIRAD TPO") Irgacure OXE01: 1-[4-(phenylthio)-2-(O-benzoyloxime)]1,2-octanedione) (Manufactured by BASF Japan, product name "Irgacure OXE01") [Hindered amine stabilizers] ADEKA LA-63P: A mixed ester of 1,2,3,4-butanetetracarboxylic acid, 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 (manufactured by ADEKA, product name "ADEKA LA-63P", N-methyl hindered amine stabilizer) Adekastab LA-52: Tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate (manufactured by ADEKA, product name "Adekastab LA-52", N-methyl hindered amine stabilizer)

[0115] [Test Example] (Measurement of Adhesion) The workpiece processing sheets produced in the examples and comparative examples were cut into strips with a width of 25 mm. The release sheet was peeled off from the resulting strip-shaped workpiece processing sheets, and the adhesive side of the exposed adhesive layer was attached to the mirror-finished surface of a silicon wafer using a 2 kg rubber roller under conditions of 23°C and 50% relative humidity to obtain the measurement sample.

[0116] For the obtained measurement samples, 20 minutes after attachment to the silicon wafer, the workpiece processing sheet was peeled off the silicon wafer at a peeling speed of 300 mm / min and a peeling angle of 180° using a universal tensile testing machine (Orientec Co., Ltd., product name "Tensilon UTM-4-100") at 23°C. The adhesive force (mN / 25mm) to the silicon wafer was measured using the 180° peeling method in accordance with JIS Z0237:2009. The resulting adhesive force was measured before heating and before UV irradiation (23°C, 0 mJ / cm²). 2 The adhesive strength was defined as the adhesive strength in the given area. The results are shown in Table 1.

[0117] Furthermore, the measurement samples obtained in the same manner as described above were subjected to ultraviolet (UV) irradiation using a UV irradiation device (Lintec Corporation, product name "RAD-2000m / 12") 20 minutes after being attached to a silicon wafer, under conditions of 23°C and 50% relative humidity (light source: high-pressure mercury lamp, illuminance: 230 mW / cm²). 2 , Light amount: 200mJ / cm 2 The following procedure was performed. For the measurement samples after UV irradiation, the workpiece processing sheet was pulled away from the silicon wafer in the same manner as above, and the adhesive force to the silicon wafer (mN / 25mm) was measured. The adhesive force obtained was then measured before heating and after UV irradiation (23℃, 200mJ / cm²). 2 The adhesive strength was defined as the adhesive strength in the given area. The results are shown in Table 1.

[0118] Furthermore, the measurement samples obtained in the same manner as above were heated in an oven at 260°C for 10 minutes. After heating, the measurement samples were removed from the oven and allowed to cool at room temperature for 5 minutes, and then irradiated with ultraviolet light in the same manner as above. For these measurement samples, the adhesive force (mN / 25mm) to the silicon wafer was measured by pulling the workpiece processing sheet away from the silicon wafer in the same manner as above. The adhesive force obtained was measured after heating and after UV irradiation (260°C, 10 min, 1000 mJ / cm²). 2 The adhesive strength was defined as the adhesive strength in the given area. The results are shown in Table 1.

[0119] [Table 1]

[0120] As can be seen from Table 1, the workpiece processing sheet according to the example was able to have its adhesive strength effectively reduced by ultraviolet irradiation in its pre-heating state. Furthermore, even after heating the workpiece processing sheet according to the example under the harsh heating conditions of 260°C for 10 minutes, its adhesive strength was still effectively reduced by ultraviolet irradiation.

[0121] On the other hand, in the case of the workpiece processing sheet according to the comparative example, the adhesive strength hardly decreased in the state after heating as described above. [Industrial applicability]

[0122] The workpiece processing sheet of the present invention can be suitably used for processing workpieces such as semiconductor wafers, and in particular, it can be suitably used in workpiece processing methods that include a step of heating the workpiece processing sheet while the workpieces are stacked before or after processing.

Claims

1. A workpiece processing sheet comprising a base material and an adhesive layer laminated on one side of the base material, The adhesive layer is composed of an active energy ray curable adhesive formed from an adhesive composition containing an oxime ester-based photopolymerization initiator having a carbazole skeleton and a hindered amine-based stabilizer. A workpiece processing sheet characterized by the following features.

2. The oxime ester-based photopolymerization initiator is given by the following formula (1) 【Chemistry 1】 It has the structure of, In formula (1) above, R １ ~R ８ At least one of them is an oxime ester-containing group, and R other than the oxime ester-containing group １ ~R ８ Each of these is selected from a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkanoyl group having 2 to 12 carbon atoms, a substituted or unsubstituted alkoxycarbonyl group having 2 to 12 carbon atoms, a substituted or unsubstituted cyclopentyl group, a substituted or unsubstituted cyclohexyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted benzoyl group, and a substituted or unsubstituted phenoxycarbonyl group, R ９ This is one selected from a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkanoyl group having 2 to 12 carbon atoms, a substituted or unsubstituted alkoxycarbonyl group having 2 to 12 carbon atoms, a substituted or unsubstituted cyclopentyl group, a substituted or unsubstituted cyclohexyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted benzoyl group, and a substituted or unsubstituted phenoxycarbonyl group. The workpiece processing sheet according to feature 1.

3. The oxime ester-containing group is represented by the following formula (2) 【Chemistry 2】 It has the structure of, In formula (2) above, X is a single bond, a carbonyl group, or a chemical structure that is bonded to the aromatic compound skeleton with or without a carbonyl group, and R １０ R is selected from a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkanoyl group having 2 to 12 carbon atoms, a substituted or unsubstituted alkenoyl group having 4 to 6 carbon atoms that is not conjugated with a carbonyl group, a substituted or unsubstituted alkoxycarbonyl group having 2 to 6 carbon atoms, a substituted or unsubstituted benzoyl group, and a substituted or unsubstituted phenoxycarbonyl group. １１ This is an alkyl group having 1 to 12 carbon atoms, or a phenyl group. The workpiece processing sheet according to feature 2.

4. The workpiece processing sheet according to claim 1, characterized in that the aforementioned hindered amine-based stabilizer is an N-alkyl type hindered amine-based stabilizer.

5. The aforementioned substrate does not fuse to the contacting object after being heated at 260°C for 10 minutes with the contacting object placed on the surface of the substrate. The contact material is one that does not change state when heated under the above conditions. The workpiece processing sheet according to feature 1.

6. The workpiece processing sheet according to claim 1, characterized in that the adhesive composition contains an acrylic polymer in which an active energy ray curable group is introduced into the side chain.

7. The workpiece processing sheet according to claim 1, characterized in that it is used in a workpiece processing method comprising the step of heating the workpiece processing sheet while the workpiece before or after processing is laminated on the side of the adhesive layer opposite to the substrate.

8. A bonding step of bonding a workpiece to the side of the adhesive layer of the workpiece processing sheet according to any one of claims 1 to 7 that is opposite to the substrate, A heating step in which the workpiece, while bonded to the workpiece processing sheet, is subjected to a heating process, A dicing step is performed to obtain a processed workpiece in which the workpiece has been divided into individual pieces by dicing the workpiece that has been subjected to the aforementioned heating process on the workpiece processing sheet. A method for manufacturing a processed workpiece, characterized by comprising the following features.

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