JP7689002B2 - Workpiece processing sheet - Google Patents

Description

The present invention relates to a workpiece processing sheet used for processing workpieces such as semiconductor wafers.

Semiconductor wafers such as silicon and gallium arsenide and various packages are manufactured in a large diameter state, cut (diced) into chips, peeled off (picked up), and then moved to the next process, the mounting process. At this time, the workpieces such as semiconductor wafers are stacked on an adhesive sheet (hereinafter sometimes referred to as the "workpiece processing sheet") that has a base material and an adhesive layer, and are then processed, such as backgrinding, dicing, cleaning, drying, expanding, picking up, and mounting.

When a sheet having an adhesive layer exhibiting active energy ray curing properties is used as the workpiece processing sheet, the adhesive strength can be reduced by irradiation with active energy rays, making it possible to easily peel the workpiece processing sheet from the processed workpiece. Patent Document 1 discloses such a workpiece processing sheet.

JP 2010-106283 A

However, workpiece processing sheets can become charged when transported or used, and such charging can cause damage to semiconductor chips and malfunctions of dicing devices. For example, when separating a processed workpiece from the workpiece processing sheet, static electricity called peeling charging can occur between the workpiece processing sheet and the processed workpiece. If the processed workpiece is, for example, a semiconductor chip, the generation of such static electricity can cause the circuits formed on the chip to be destroyed.

For this reason, it has been considered to give the workpiece processing sheet an antistatic function to prevent static electricity. For example, it has been considered to provide an antistatic layer containing an antistatic agent between the base material and the adhesive layer. However, the inventors have confirmed that with such a workpiece processing sheet provided with an antistatic layer, when the processed workpiece is separated from the workpiece processing sheet, the adhesive that constitutes the adhesive layer is likely to adhere to the processed workpiece (hereinafter sometimes referred to as "glue residue").

The present invention was made in consideration of these circumstances, and aims to provide a workpiece processing sheet that reduces glue residue on the workpiece.

In order to achieve the above object, first, the present invention provides a workpiece processing sheet comprising a substrate and an adhesive layer laminated on one side of the substrate, the workpiece processing sheet being characterized in that the tin atom content in the adhesive layer is 0.002% by mass or more and 0.015% by mass or less (Invention 1).

In the workpiece processing sheet according to the above invention (Invention 1), the content of tin atoms in the adhesive layer is within the above range, so that even if the substrate has an antistatic layer (including the "organic conductive film" described below), the adhesive layer adheres well to the substrate (or the antistatic layer), and the occurrence of adhesive residue on the processed workpiece that has been separated from the adhesive layer is suppressed.

In the above invention (Invention 1), it is preferable that the adhesive layer is composed of an active energy ray-curable adhesive (Invention 2).

In the above invention (Invention 2), the active energy ray-curable adhesive preferably contains a polymer having active energy ray-curability and a tin-containing catalyst containing tin atoms (Invention 3).

In the above invention (Invention 3), the active energy ray-curable polymer is a (meth)acrylic acid ester polymer having an active energy ray-curable group introduced into the side chain, and the (meth)acrylic acid ester polymer is preferably obtained by reacting an acrylic copolymer having a functional group-containing monomer unit with an unsaturated group-containing compound having a functional group bonded to the functional group, under the catalytic action of the tin-containing catalyst (Invention 4).

In the above inventions (Inventions 1 to 4), the surface resistivity of the surface of the substrate on which the pressure-sensitive adhesive layer is laminated is preferably 1×10 ¹⁰ Ω/□ or less (Invention 5).

In the above inventions (Inventions 1 to 5), it is preferable that the substrate has an organic conductive film on the surface on which the pressure-sensitive adhesive layer is laminated (Invention 6).

In the above inventions (Inventions 1 to 6), it is preferable to use it for dicing (Invention 7).

The workpiece processing sheet of the present invention can prevent glue from being left behind on the workpiece.

1 is a cross-sectional view of a workpiece processing sheet according to one embodiment of the present invention. FIG. 4 is a cross-sectional view of a workpiece processing sheet according to another embodiment of the present invention. FIG. 11 is a cross-sectional view of a workpiece processing sheet according to yet another embodiment of the present invention.

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, and the adhesive layer has a tin atom content of 0.002% by mass or more and 0.015% by mass or less.

In general, when using a workpiece processing sheet, a workpiece is attached to the side of the adhesive layer of the workpiece processing sheet opposite the substrate (hereinafter sometimes referred to as the "adhesive side"), and then the workpiece is subjected to a predetermined processing on the workpiece processing sheet. Next, (if the adhesive layer is made of an active energy ray-curable adhesive, the adhesive layer is irradiated with active energy rays to cure the adhesive layer) the processed workpiece is separated from the workpiece processing sheet. During this separation, with conventional workpiece processing sheets, adhesive residue as described above tends to occur.

However, in the workpiece processing sheet according to this embodiment, the content of tin atoms in the adhesive layer is within the above range, which improves the adhesion between the substrate and the adhesive layer. This suppresses the occurrence of peeling at the interface between the substrate and the adhesive layer that accompanies separation of the workpiece from the workpiece processing sheet. As a result, adhesion of the adhesive that constitutes the adhesive layer to the workpiece being separated is suppressed. In other words, adhesive residue on the workpiece is effectively suppressed.

In addition, as a general means of improving the adhesion between the substrate and the adhesive layer, the surface of the substrate on which the adhesive layer is to be provided may be subjected to a surface treatment such as a corona treatment. However, when a film (organic conductive film) for the purpose of preventing static electricity is provided on the surface of the substrate, the surface of the organic conductive film cannot be subjected to a surface treatment such as a corona treatment in order to avoid damage to the organic conductive film. Therefore, when using a substrate having the above-mentioned organic conductive film, there is a problem that adhesive residue is particularly likely to occur.

However, with the workpiece processing sheet according to this embodiment, even if it is not possible to perform a surface treatment on the substrate to enhance adhesion between the substrate and the adhesive layer, such as when an organic conductive film is provided on the surface of the substrate, it is possible to achieve excellent adhesion between the substrate and the adhesive layer, and it is possible to effectively prevent the occurrence of residual glue.

From the viewpoint of further improving the adhesion between the substrate and the adhesive layer, the upper limit of the tin atom content in the adhesive layer is preferably 0.014% or less, and more preferably 0.013% or less. From the same viewpoint, the lower limit of the tin atom content in the adhesive layer is preferably 0.0022% or more, and more preferably 0.0024% or more.

In addition, the origin of the tin atoms in the adhesive layer in this embodiment may be a tin-containing catalyst as a material for forming the adhesive layer, as described below. In this case, by adjusting the amount of the tin-containing catalyst used so that the content of tin atoms in the adhesive layer falls within the above-mentioned range, it is possible to obtain a work processing sheet that can effectively suppress adhesive residue while achieving the desired performance such as adhesion.

In this embodiment, the content of tin atoms in the adhesive layer may be determined by quantitative analysis, or may be calculated from the composition of the material (e.g., the adhesive composition described below) used to form the adhesive layer.

The type of quantitative analysis is not particularly limited, but the following method is one example. First, 50 mg of the adhesive constituting the adhesive layer is sampled and pretreated by pressurized acid decomposition. Then, the content of tin atoms in the adhesive can be obtained by inductively coupled plasma mass spectrometry (ICP-MS) (for example, an apparatus manufactured by Agilent Technologies is used).

Examples of workpieces for which the workpiece processing sheet according to this embodiment can be used include semiconductor components such as semiconductor chips, semiconductor wafers, and semiconductor packages, and glass components such as glass chips and glass plates.

1. Constituent Members of the Workpiece Processing Sheet Fig. 1 to Fig. 3 show an example of the workpiece processing sheet according to this embodiment.
The workpiece processing sheet 1A shown in FIG. 1 includes a substrate 11a having an organic conductive film 112 provided on both sides of a base film 111, and an adhesive layer 12 laminated on one side of the substrate 11a.

The workpiece processing sheet 1B shown in FIG. 2 comprises a substrate 11b having an organic conductive film 112 on one side of a base film 111, and an adhesive layer 12 laminated on the surface of the substrate 11a on which the organic conductive film 112 is provided.

The workpiece processing sheet 1C shown in FIG. 3 comprises a substrate 11c made of a base film 111' containing an antistatic agent, and an adhesive layer 12 laminated on one side of the substrate 11c.

(1) Substrate The substrate in this embodiment is not particularly limited as long as it exhibits the desired function in the process of using the workpiece processing sheet. The substrate in this embodiment may be one having an organic conductive film 112 on both sides or one side of a base film 111 as shown in Figures 1 and 2, or one consisting of a base film 111' containing an antistatic agent as shown in Figure 3. Furthermore, the substrate in this embodiment may be one consisting of a base film 111 that does not have an organic conductive film 112 and does not contain an antistatic agent, or one consisting of an organic conductive film 112 on both sides or one side of a base film 111' containing an antistatic agent.

As described above, the workpiece processing sheet according to this embodiment can effectively prevent the occurrence of adhesive residue even in cases where the substrate cannot be surface-treated to improve adhesion between the substrate and the adhesive layer. Therefore, it is preferable that the substrate in this embodiment is provided with an organic conductive film 112 as shown in Figures 1 and 2, since this provides a high benefit in preventing adhesive residue.

(1-1) Base Film The base film 111 is preferably a resin film mainly made of a resin material, and specific examples thereof include ethylene-vinyl acetate copolymer film; ethylene-(meth)acrylic acid copolymer film, ethylene-(meth)methyl acrylate copolymer film, other ethylene-(meth)acrylic acid ester copolymer film, and other ethylene-(meth)acrylic acid ester copolymer films; polyolefin films such as polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, ethylene-norbornene copolymer film, and norbornene resin film; polyvinyl chloride films such as polyvinyl chloride copolymer film, and other polyvinyl chloride films; polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate; (meth)acrylic acid ester copolymer film; polyurethane film; polyimide film; polystyrene film; polycarbonate film; fluororesin film, etc. Examples of polyethylene films include low-density polyethylene (LDPE) film, linear low-density polyethylene (LLDPE) film, and high-density polyethylene (HDPE) film. Modified films such as crosslinked films and ionomer films are also used. Preferred examples of the base film 111' include films containing an antistatic agent. When the adhesive layer 12 is made of an active energy ray-curable adhesive, the base film 111 and the base film 111' are preferably made of a material that exhibits good transmittance to the active energy rays irradiated for curing the adhesive layer 12.

The base film 111 may also be a laminated film in which a plurality of the above-mentioned films are laminated. In this laminated film, the materials constituting each layer may be the same or different. The base film 111' may also be a laminated film, in which case all of the layers constituting the base film may contain an antistatic agent, or at least one layer may contain an antistatic agent.

Of the above films, it is preferable to use an ethylene-methyl methacrylate copolymer film as the base film 111, because it has excellent flexibility. It is also preferable to use an ethylene-methyl methacrylate copolymer film containing an antistatic agent as the base film 111'. In this specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid. The same applies to other similar terms.

The base film 111 may contain various additives such as flame retardants, plasticizers, antistatic agents, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion traps. The content of these additives is not particularly limited, but is preferably within a range in which the base film 111 exhibits the desired functions. The base film 111' may also contain the various additives described above in addition to the antistatic agent.

The surface of the base film 111 on which the organic conductive film 112 is laminated may be subjected to a surface treatment such as a primer treatment, a corona treatment, or a plasma treatment to improve adhesion to the organic conductive film 112.

(1-2) Organic Conductive Film The organic conductive film 112 is not particularly limited as long as it can exhibit the desired functions, such as antistatic properties.

The organic conductive film 112 preferably contains a conductive material and a binder resin. Examples of the conductive material include conductive polymers, conductive fillers, anionic or cationic compounds, and compounds having a quaternary ammonium base in the main chain or side chain of the molecule.

Examples of the conductive polymer include polythiophene-based, polyaniline-based, and polypyrrole-based conductive polymers. Examples of polythiophene-based conductive polymers include polythiophene, poly(3-alkylthiophene), poly(3-thiophene-β-ethanesulfonic acid), and a mixture of polyalkylenedioxythiophene and polystyrene sulfonate. Examples of polyalkylenedioxythiophene include polyethylenedioxythiophene, polypropylenedioxythiophene, and poly(ethylene/propylene)dioxythiophene. Examples of polyaniline-based conductive polymers include polyaniline, polymethylaniline, and polymethoxyaniline. Examples of polypyrrole-based conductive polymers include polypyrrole, poly3-methylpyrrole, and poly3-octylpyrrole. These conductive polymer compounds may be used alone or in combination of two or more. It is preferable to use these conductive polymers in the form of an aqueous solution by dispersing them in water.

Examples of conductive fillers include particles of gold, silver, copper, nickel, aluminum, stainless steel, carbon, conductive ceramics, tin oxide, antimony-doped tin oxide (ATO), indium oxide-tin oxide (ITO), zinc oxide, and antimony pentoxide.

Examples of anionic and cationic compounds include ionic liquids, ionic solids, anionic surfactants, alkali metal salts, cationic surfactants, and nonionic surfactants. Examples of ionic liquids and ionic solids include nitrogen-containing onium salts, sulfur-containing onium salts, and phosphorus-containing onium salts. Examples of alkali metal salts include lithium salts and potassium salts. These may be used alone or in combination of two or more.

Specific examples of compounds having a quaternary ammonium base include pyrrolidium rings, quaternized alkylamines, copolymers of these with acrylic acid or methacrylic acid, quaternized N-alkylaminoacrylamides, vinylbenzyltrimethylammonium salts, and 2-hydroxy-3-methacryloxypropyltrimethylammonium salts.

The compound having a quaternary ammonium base is preferably a polymer compound. The number average molecular weight of the compound having a quaternary ammonium base is preferably 1000 or more, more preferably 2000 or more, and even more preferably 5000 or more. In addition, the upper limit of the number average molecular weight is preferably 500,000 or less from the viewpoint of preventing the viscosity of the coating liquid containing the conductive material from becoming too high. In addition, the number average molecular weight in this specification is a value calculated in terms of standard polystyrene measured by gel permeation chromatography (GPC).

The content of the conductive material in the organic conductive film 112 is preferably 1% by mass or more, and more preferably 5% by mass or more. The content is also preferably 30% by mass or less, and more preferably 20% by mass or less. When the content of the conductive material is 1% by mass or more, the desired functions such as antistatic properties are effectively exhibited. Furthermore, when the content of the conductive polymer is 30% by mass or less, the ratio of the binder resin in the organic conductive film 112 is sufficient, and the coating strength of the organic conductive film 112 itself is good.

Examples of binder resins include melamine resin, polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, amide resin, polyvinyl alcohol, etc. Examples of melamine resins include methylated melamine resin, butylated melamine resin, methyl/butylated melamine resin, etc., and among these, it is preferable to use butylated melamine resin. These binder resins may have a composite skeletal structure due to copolymerization or the like. Examples of binder resins having a composite structure include acrylic resin grafted polyester, acrylic resin grafted polyurethane, vinyl resin grafted polyester, vinyl resin grafted polyurethane, etc.

The organic conductive film 112 may further include a cross-linking reactive compound. The cross-linking reactive compound is obtained by adding a cross-linking agent to a coating liquid containing a conductive material and causing a cross-linking reaction with the functional group of the compound contained in the coating liquid. By adding a cross-linking agent to the coating liquid, the water resistance, solvent resistance, mechanical strength, etc. of the organic conductive film 112 are improved.

Examples of crosslinking agents include melamine-based crosslinking agents and epoxy-based crosslinking agents. Examples of melamine-based crosslinking agents include methoxymethylated melamine and butoxymethylated melamine, which are alkylol or alkoxyalkylolated melamine compounds, and melamine that is partially co-condensed with urea or the like may also be used. As epoxy-based crosslinking agents, it is preferable to use compounds that are water-soluble or have an epoxy group with a water-solubilization rate of 50% or more.

The organic conductive film 112 may contain at least one additive, such as an antifoaming agent, a coating improver, a thickener, an organic lubricant, organic particles, or inorganic particles, as necessary.

The organic conductive film 112 can be formed by applying a coating liquid containing the above-mentioned conductive polymer and binder resin, etc., to one or both sides of the base film 111 and drying the resulting coating film.

The thickness of the organic conductive film 112 can be set appropriately depending on the method in which the workpiece processing sheet is used, but is usually preferably 0.003 μm or more, and more preferably 0.005 μm or more. The thickness is also preferably 1.5 μm or less, and more preferably 0.5 μm or less.

(1-3) Antistatic Agent in Base Film When the substrate according to this embodiment is composed only of a base film 111′ containing an antistatic agent, the antistatic agent contained in the base film 111′ is not particularly limited as long as it is capable of imparting the desired antistatic properties.

Preferred antistatic agents include low molecular weight antistatic agents, polymeric antistatic agents, metal oxides, carbon materials, etc., with polymeric antistatic agents being particularly preferred. Examples of the polymeric antistatic agent include vinyl copolymers having sulfonate salts in the molecule, alkylsulfonates, alkylbenzenesulfonates, betaines, etc. In particular, examples of inorganic protonic acid salts of polyethers, polyamide elastomers, polyester elastomers, polyether amides, or polyether ester amides can be mentioned. Examples of inorganic protonic acid salts include alkali metal salts, alkaline earth metal salts, zinc salts, and ammonium salts.

The content of the antistatic agent in the base film 111' is preferably 3% by mass or more and 20% by mass or less. When the content of the antistatic agent is within the above range, the obtained base film 111' is likely to have good antistatic properties.

(1-4) Physical Properties of the Substrate The surface resistivity of the surface of the substrate 11 on which the adhesive layer is laminated is preferably 1×10 ¹² Ω/□ or less, particularly preferably 5×10 ¹¹ Ω/□ or less, and more preferably 1×10 ¹¹ Ω/□ or less. When the substrate 11 exhibits the above-mentioned surface resistivity, the workpiece processing sheet is likely to exhibit excellent antistatic properties. The lower limit of the surface resistivity is not particularly limited, and may be, for example, 1×10 ⁴ Ω/□ or more, particularly 1×10 ⁵ Ω/□ or more. Details of the method for measuring the surface resistivity are as described in the test examples described below.

The thickness of the substrate 11 (including the organic conductive film 112 if the substrate 11 has an organic conductive film 112) can be set appropriately depending on the method in which the workpiece processing sheet is used, but is usually preferably 20 μm or more, and more preferably 25 μm or more. In addition, the thickness is usually preferably 450 μm or less, and more preferably 300 μm or less.

(2) Adhesive Layer In the workpiece processing sheet according to this embodiment, the adhesive layer is not particularly limited as long as it contains tin atoms in the above-mentioned content and can exert sufficient adhesive strength to the adherend (particularly, adhesive strength to the workpiece sufficient for processing the workpiece).

Examples of adhesives constituting the adhesive layer in this embodiment include acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, polyvinyl ether adhesives, etc. Among these, it is preferable to use acrylic adhesives, from the viewpoints that the tin atom content can be easily adjusted to the above-mentioned range and that the desired adhesive strength can be easily exerted.

In the adhesive layer of this embodiment, the aforementioned content of tin atoms may be achieved by adding simple tin and/or a tin-containing compound to the adhesive constituting the adhesive layer. Alternatively, the aforementioned content of tin atoms may be achieved by using a tin-containing compound (particularly a tin-containing catalyst, which will be described later) as one of the materials of the adhesive layer.

The adhesive constituting the adhesive layer in this embodiment may be an adhesive that does not have active energy ray curing properties, but is preferably an adhesive that has active energy ray curing properties (hereinafter, may be referred to as an "active energy ray curable adhesive"). Since the adhesive layer is composed of an active energy ray curable adhesive, the adhesive layer can be cured by irradiation with active energy rays, and the adhesive strength of the workpiece processing sheet to the adherend can be easily reduced. In particular, irradiation with active energy rays makes it possible to easily separate the processed workpiece from the workpiece processing sheet.

The active energy ray curable adhesive constituting the adhesive layer may be one whose main component is a polymer having active energy ray curability, or may be one whose main component is 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 active energy ray curable group. It may also be a mixture of a polymer having active energy ray curability and a non-active energy ray curable polymer, a mixture of a polymer having active energy ray curability and a monomer and/or oligomer having at least one active energy ray curable group, or a mixture of these three types.

First, the case where the active energy ray-curable adhesive contains a polymer having active energy ray-curing properties as the main component will be described below.

The active energy ray curable polymer is preferably a (meth)acrylic acid ester (co)polymer (A) (hereinafter sometimes referred to as "active energy ray curable polymer (A)") having a functional group (active energy ray curable group) having active energy ray curability introduced into the side chain. This active energy ray curable polymer (A) is preferably obtained by reacting an acrylic copolymer (a1) having a functional group-containing monomer unit with an unsaturated group-containing compound (a2) having a functional group bonded to the functional group.

The acrylic copolymer (a1) preferably contains a structural unit derived from a functional group-containing monomer and a structural unit derived from a (meth)acrylic acid ester monomer or a derivative thereof.

The functional group-containing monomer as a constituent unit of the acrylic copolymer (a1) is preferably a monomer having a polymerizable double bond and a functional group such as a hydroxy group, a carboxy group, an amino group, a substituted amino group, or an epoxy group in the molecule.

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

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

Examples of amino group-containing monomers or substituted amino group-containing monomers include aminoethyl (meth)acrylate and n-butylaminoethyl (meth)acrylate. These may be used alone or in combination of two or more.

The acrylic copolymer (a1) preferably contains 1% by mass or more, particularly preferably 5% by mass or more, and even more preferably 10% by mass or more of the structural units derived from the functional group-containing monomer. The acrylic copolymer (a1) preferably contains 35% by mass or less, particularly preferably 30% by mass or less, of the structural units derived from the functional group-containing monomer. By containing the functional group-containing monomer in the above range, the acrylic copolymer (a1) can easily form the desired active energy radiation-curable polymer (A).

As the (meth)acrylic acid ester monomer constituting the acrylic copolymer (a1), in addition to (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 20 carbon atoms, for example, monomers having an alicyclic structure in the molecule (alicyclic structure-containing monomers) are preferably used.

As the (meth)acrylic acid alkyl ester, particularly (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, are preferably used. These may be used alone or in combination of two or more.

As the alicyclic structure-containing monomer, for example, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, etc. are preferably used. These may be used alone or in combination of two or more.

The acrylic copolymer (a1) preferably contains 50% by mass or more, particularly preferably 60% by mass or more, and even more preferably 70% by mass or more, of structural units derived from (meth)acrylic acid ester monomers or derivatives thereof. The acrylic copolymer (a1) preferably contains 99% by mass or less, particularly preferably 95% by mass or less, and even more preferably 90% by mass or less, of structural units derived from (meth)acrylic acid ester monomers or derivatives thereof.

The acrylic copolymer (a1) is obtained by copolymerizing the functional group-containing monomers described above with (meth)acrylic acid ester monomers or their derivatives in a conventional manner, but in addition to these monomers, dimethylacrylamide, vinyl formate, vinyl acetate, styrene, etc. may also be copolymerized.

The acrylic copolymer (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).

The functional group of the unsaturated group-containing compound (a2) can be appropriately selected depending on the type of functional group of the functional group-containing monomer unit of the acrylic copolymer (a1). For example, when the functional group of the acrylic copolymer (a1) is a hydroxy group, an amino group, or a substituted amino group, the functional group of the unsaturated group-containing compound (a2) is preferably an isocyanate group or an epoxy group, and when the functional group of the acrylic copolymer (a1) is an epoxy group, the functional group of the unsaturated group-containing compound (a2) is preferably an amino group, a carboxy group, or an aziridinyl group.

In addition, the 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 in each molecule. Specific examples of such unsaturated group-containing compounds (a2) include, for example, 2-methacryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate; acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with hydroxyethyl (meth)acrylate; acryloyl monoisocyanate compounds 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.

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 number of moles of the functional group-containing monomer in the acrylic copolymer (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 number of moles of the functional group-containing monomer in the acrylic copolymer (a1).

In the reaction between the acrylic copolymer (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 acrylic copolymer (a1) and the functional group of the unsaturated group-containing compound (a2). As a result, the functional group present in the acrylic copolymer (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 acrylic copolymer (a1), thereby obtaining the active energy radiation-curable polymer (A).

In the adhesive of this embodiment, it is preferable to use a tin-containing catalyst as a catalyst that promotes the reaction between the acrylic copolymer (a1) and the unsaturated group-containing compound (a2). By using a tin-containing catalyst, the reaction between the acrylic copolymer (a1) and the unsaturated group-containing compound (a2) proceeds effectively, making it easier to form an adhesive having the desired performance, and making it easier to adjust the tin atom content in the obtained adhesive layer to the above-mentioned range.

Examples of the tin-containing catalyst include organic tin compounds such as dibutyltin dilaurate, trimethyltin hydroxide, and tetra-n-butyltin, organic acid tin compounds such as tin octenate and tin octoate, and tin salts such as stannous chloride and stannic chloride, among which dibutyltin dilaurate is preferred. These may be used alone or in combination of two or more.

The amount of the tin-containing catalyst is preferably 0.010% by mass or more, more preferably 0.015% by mass or more, and even more preferably 0.02% by mass or more, based on the total amount of the monomers constituting the acrylic copolymer (a1).The amount of the tin-containing catalyst is preferably 0.12% by mass or less, more preferably 0.10% by mass or less, and even more preferably 0.08% by mass or less, based on the total amount of the monomers constituting the acrylic copolymer (a1).
When the amount of the tin-containing catalyst is within the above range, it is possible to favorably form the active energy radiation-curable polymer (A), while making it easy to adjust the content of tin atoms in the pressure-sensitive adhesive layer to the above range.

The weight average molecular weight (Mw) of the active energy radiation curable polymer (A) obtained in the above manner 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.

Even when the active energy ray curable adhesive contains as its main component a polymer having active energy ray curability, such as an active energy ray curable polymer (A), the active energy ray curable adhesive may further contain an active energy ray curable monomer and/or oligomer (B).

As the active energy ray-curable monomer and/or oligomer (B), for example, an ester of a polyhydric alcohol and (meth)acrylic acid can be used.

Examples of such active energy ray-curable monomers and/or oligomers (B) include monofunctional acrylic acid esters such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate, polyfunctional acrylic acid esters such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and dimethyloltricyclodecane di(meth)acrylate, polyester oligo(meth)acrylate, polyurethane oligo(meth)acrylate, etc.

When active energy ray curable monomers and/or oligomers (B) are blended with active energy ray curable polymer (A), the content of active energy ray curable monomers and/or oligomers (B) in the active energy ray curable adhesive is preferably more than 0 parts by mass, and more preferably 60 parts by mass or more, per 100 parts by mass of active energy ray curable polymer (A). In addition, the content is preferably 250 parts by mass or less, and more preferably 200 parts by mass or less, per 100 parts by mass of active energy ray curable polymer (A).

Here, when ultraviolet light is used as the active energy ray for curing the active energy ray-curable adhesive, it is preferable to add a photopolymerization initiator (C), and the use of this photopolymerization initiator (C) can reduce the polymerization curing time and the amount of light irradiation.

Specific examples of the photopolymerization initiator (C) 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, diacetyl, β-chloroanthraquinone, (2,4,6-trimethylbenzyldiphenyl)phosphine oxide, 2-benzothiazole-N,N-diethyldithiocarbamate, oligo{2-hydroxy-2-methyl-1-[4-(1-propenyl)phenyl]propanone}, and 2,2-dimethoxy-1,2-diphenylethan-1-one. These may be used alone or in combination of two or more.

The photopolymerization initiator (C) is preferably used in an amount of 0.1 parts by mass or more, particularly 0.5 parts by mass or more, per 100 parts by mass of the active energy ray curable polymer (A) (when active energy ray curable monomers and/or oligomers (B) are blended, the total amount of the active energy ray curable polymer (A) and the active energy ray curable monomers and/or oligomers (B) is 100 parts by mass). The photopolymerization initiator (C) is preferably used in an amount of 10 parts by mass or less, particularly 6 parts by mass or less, per 100 parts by mass of the active energy ray curable polymer (A) (when active energy ray curable monomers and/or oligomers (B) are blended, the total amount of the active energy ray curable polymer (A) and the active energy ray curable monomers and/or oligomers (B) is 100 parts by mass).

In addition to the above components, other components may be appropriately blended into the active energy ray curable adhesive. Examples of other components include a non-active energy ray curable polymer component or oligomer component (D), a crosslinking agent (E), etc.

Examples of non-active energy ray curable polymer or oligomer components (D) include polyacrylic acid esters, polyesters, polyurethanes, polycarbonates, polyolefins, etc., and polymers or oligomers having a weight average molecular weight (Mw) of 3,000 to 2.5 million are preferred. By blending the component (D) with the active energy ray curable adhesive, it is possible to improve the adhesion and peelability before curing, the strength after curing, the adhesion to other layers, storage stability, etc. The blending amount of the component (D) is not particularly limited, and is appropriately determined in the range of more than 0 parts by mass and not more than 50 parts by mass per 100 parts by mass of the active energy ray curable polymer (A).

As the crosslinking agent (E), a polyfunctional compound having reactivity with the functional groups of the active energy radiation curable polymer (A) or the like can be used. Examples of such polyfunctional compounds include isocyanate compounds, epoxy compounds, amine compounds, melamine compounds, aziridine compounds, hydrazine compounds, aldehyde compounds, oxazoline compounds, metal alkoxide compounds, metal chelate compounds, metal salts, ammonium salts, reactive phenolic resins, and the like. Among these, isocyanate compounds are preferred from the viewpoint of easily improving the adhesion of the adhesive layer to the substrate, and hexamethylene diisocyanate (HMDI) compounds are particularly preferred.

The amount of the crosslinking agent (E) is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, and even more preferably 0.04 parts by mass or more, per 100 parts by mass of the active energy ray curable polymer (A). The amount of the crosslinking agent (E) is preferably 8 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3.5 parts by mass or less, per 100 parts by mass of the active energy ray curable polymer (A).

Next, the case where the active energy ray-curable adhesive is mainly composed of a mixture of a non-active energy ray-curable polymer component and a monomer and/or oligomer having at least one active energy ray-curable group will be described below.

As the non-active energy ray curable polymer component, for example, a component similar to the acrylic copolymer (a1) described above can be used.

The monomer and/or oligomer having at least one active energy ray curable group may be the same as the above-mentioned component (B). The blending ratio of the non-active energy ray curable polymer component and the monomer and/or oligomer having at least one active energy ray curable group is preferably 1 part by mass or more of the monomer and/or oligomer having at least one active energy ray curable group per 100 parts by mass of the non-active energy ray curable polymer component, and more preferably 60 parts by mass or more. The blending ratio is preferably 200 parts by mass or less of the monomer and/or oligomer having at least one active energy ray curable group per 100 parts by mass of the non-active energy ray curable polymer component, and more preferably 160 parts by mass or less.

In this case, the photopolymerization initiator (C) and crosslinking agent (E) can be added as appropriate, as described above.

The thickness of the adhesive layer can be set appropriately depending on the method in which the workpiece processing sheet is used, but is usually preferably 3 μm or more, and more preferably 5 μm or more. The thickness is also preferably 50 μm or less, and more preferably 40 μm or less.

(3) Release sheet In the workpiece processing sheet according to this embodiment, a release sheet may be laminated on the adhesive surface of the adhesive layer in order to protect the surface until the adhesive surface is attached to the workpiece. The configuration of the release sheet is arbitrary, and an example is a plastic film that has been subjected to a release treatment using a release agent or the like. Specific examples of 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-based, and the like can be used, and among these, silicone-based, which is inexpensive and provides stable performance, is preferred. There is no particular limit to the thickness of the release sheet, but it is usually 20 μm or more and 250 μm or less.

(4) Others 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.

In addition, 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 an 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.

2. Physical properties of the workpiece processing sheet In the workpiece processing sheet according to this embodiment, the surface resistivity of the surface (adhesive surface) of the adhesive layer opposite to the substrate is preferably 1×10 ¹³ Ω/□ or less, particularly preferably 1×10 ¹⁰ Ω/□ or less, and more preferably 1×10 ⁶ Ω/□ or less. When the adhesive surface exhibits the above-mentioned surface resistivity, the workpiece processing sheet is likely to exhibit excellent antistatic properties. The lower limit of the surface resistivity is not particularly limited, and may be, for example, 1×10 ⁴ Ω/□ or more, particularly 1×10 ⁵ Ω/□ or more. The surface resistivity is measured at an applied voltage of 100V using a device such as DIGITAL ELECTROMETER (manufactured by ADVANTEST).

3. Manufacturing method of the work processing sheet The manufacturing method of the work processing sheet according to the present embodiment is not particularly limited, and for example, it is preferable to obtain the work processing sheet by forming an adhesive layer on a release sheet, and then laminating one side of a substrate on the side of the adhesive layer opposite to the release sheet. Note that, when using a substrate 11b having an organic conductive film 112 on only one side of the base film 111, the adhesive layer 12 may be laminated on either side of the substrate 11b.

The above-mentioned adhesive layer can be formed by a known method. For example, a coating liquid containing an adhesive composition for forming the adhesive layer and, if desired, a solvent or dispersion medium is prepared. Then, the coating liquid is applied to the releasable surface of the release sheet (hereinafter, sometimes referred to as the "release surface"). The resulting coating film is then dried to form the adhesive layer.

The coating of the coating liquid described above can be carried out by a known method, such as bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, etc. The properties of the coating liquid are not particularly limited as long as it can be applied, and the liquid may contain the components for forming the adhesive layer as a solute or as a dispersoid. The release sheet may be peeled off as a processing material, or may protect the adhesive layer until it is applied to the adherend.

When the adhesive composition for forming the adhesive layer contains the above-mentioned crosslinking agent, it is preferable to advance the crosslinking reaction between the polymer component in the coating film and the crosslinking agent by changing the above-mentioned drying conditions (temperature, time, etc.) or by separately providing a heat treatment, and form a crosslinked structure with the desired density in the adhesive layer. Furthermore, in order to advance the above-mentioned crosslinking reaction sufficiently, after laminating the adhesive layer and the substrate, curing may be performed, for example by leaving the adhesive layer to stand for several days in an environment of 23°C and a relative humidity of 50%.

4. Method of using 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 the workpiece, the workpiece can be processed on the workpiece processing sheet. Examples of processing at this time include back grinding of semiconductor wafers and glass plates, dicing of semiconductor wafers and glass plates, expanding of semiconductor chips and glass chips, picking up of semiconductor chips and glass chips, etc.

Here, when the workpiece processing sheet according to this embodiment is provided with substrates 11a, 11b having an organic conductive film 112 or substrate 11c containing an antistatic agent, charging of the workpiece processing sheets 1A, 1B, 1C during transport or use is effectively suppressed. As a result, damage to the workpiece and malfunction of the processing device can be effectively suppressed.

After the processing of the workpiece on the workpiece processing sheet is completed, the workpiece processing sheet and the workpiece can be separated. For example, a semiconductor wafer or glass plate serving as the workpiece is diced on the workpiece processing sheet to separate it into multiple semiconductor chips, and the workpiece processing sheet is expanded as necessary, and the semiconductor chips or glass chips are individually picked up from the workpiece processing sheet.

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

Here, when the adhesive layer in this embodiment is made of an active energy ray-curable adhesive, the adhesive layer can be irradiated with active energy rays to harden the adhesive layer, thereby reducing the adhesion between the adhesive layer and the workpiece. This makes it possible to easily pick up the workpiece from the workpiece processing sheet when picking up a semiconductor chip or a glass chip.

In the workpiece processing sheet according to this embodiment, the content of tin atoms in the adhesive layer is within the above-mentioned range, so that when the workpiece is picked up from the workpiece processing sheet, peeling at the interface between the substrate and the adhesive layer can be suppressed. This makes it possible to suppress the adhesive constituting the adhesive layer from adhering to the surface of the picked-up workpiece. In other words, it is possible to suppress the occurrence of glue residue on the workpiece.

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

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

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

(1) Preparation of Pressure-Sensitive Adhesive Composition 52 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl methacrylate, 28 parts by mass of 2-hydroxyethyl acrylate, and 0.1% azobisisobutyronitrile (polymerization initiator) based on the total amount of these monomers were mixed in ethyl acetate, and then reacted at 60° C. for 24 hours to obtain a solution containing an acrylic copolymer (solid concentration: 40% by mass). The weight-average molecular weight of the acrylic copolymer was measured by the method described below and found to be 500,000.

Next, methyl ethyl ketone was added to the above solution to adjust the solid concentration to 35% by mass. Then, 2-methacryloyloxyethyl isocyanate (MOI) was added to the solution in an amount equivalent to 90 mol% of the 2-hydroxyethyl acrylate constituting the above acrylic copolymer, and dibutyltin dilaurate (DBTDL) was added as a tin-containing catalyst in an amount of 0.02% by mass relative to the total amount of the above-mentioned monomers. After that, the mixture was reacted at 50°C for 24 hours to obtain a (meth)acrylic acid ester polymer (active energy ray curable polymer) having an active energy ray curable group introduced into the side chain. The weight average molecular weight of the active energy ray curable polymer was measured by the method described below and was found to be 500,000.

100 parts by mass of the obtained active energy ray curable polymer (solid content equivalent, the same applies below), 0.3 parts by mass of 1-hydroxycyclohexyl phenyl ketone (manufactured by BASF, product name "Omnirad 184") as a photopolymerization initiator, and 2 parts by mass of a hexamethylene diisocyanate trimer adduct of trimethylolpropane (manufactured by Tosoh, product name "Coronate HL") as a crosslinking agent were mixed in a solvent to obtain a coating solution of the adhesive composition (solid content concentration 25% by mass).

When a pressure-sensitive adhesive layer is formed as described below using the coating solution of the pressure-sensitive adhesive composition, the content of tin atoms in the resulting pressure-sensitive adhesive layer is calculated to be 0.0027% by mass.

(2) Formation of Adhesive Layer A coating solution of the adhesive composition was applied using a comma coater to the release surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET3801") consisting of a 38 μm-thick polyethylene terephthalate (PET) film with a silicone-based release agent layer formed on one side thereof, and the coating was dried at 90°C for 1 minute to form a 5 μm-thick adhesive layer on the release sheet.

(3) Preparation of Substrate A coating solution for an organic conductive film was obtained by adding 2 parts by mass of a butylated melamine resin (manufactured by DIC Corporation, product name "Super Beckamine J820-60") as a binder resin to an emulsion containing a polypyrrole-based conductive polymer as a conductive material obtained by emulsion polymerization of a pyrrole monomer, per 100 parts by mass of the polypyrrole-based conductive polymer, and thoroughly mixing the mixture.

One side of an 80 μm thick ethylene-methacrylic acid copolymer (EMAA) film was irradiated with corona radiation. The coating liquid for the organic conductive film obtained as described above was then applied to the corona irradiated side of the EMAA film, and dried by heating to form an organic conductive film with a thickness of 50 nm. The other side of the EMAA film was also irradiated with corona radiation in the same manner as above, and an organic conductive film with a thickness of 50 nm was then formed. This resulted in a substrate having organic conductive films formed on both sides of the EMAA film.

The surface resistivity of both sides of this substrate was measured using a DIGITAL ELECTROMETER (manufactured by ADVANTEST) at an applied voltage of 100 V, and was found to be 1.5×10 ⁶ Ω/□. This value is very small compared to the general surface resistivity of a single PET film (1×10 ¹⁵ to 1×10 ¹⁶ Ω/□). Therefore, it is expected that the workpiece processing sheet obtained using the substrate prepared as described above will exhibit excellent antistatic properties.

(4) Preparation of workpiece processing sheet The surface opposite to the release sheet in the adhesive layer formed in the above step (2) and one side of the substrate obtained in the above step (3) were laminated together, and then stored for one week under an environment of 23°C and 50% humidity. As a result, a workpiece processing sheet was obtained in which a release sheet, an adhesive layer, and a substrate having an organic conductive film on both sides were laminated in order. The content of tin atoms in the adhesive layer of the workpiece processing sheet was 0.0027% by mass, as described above.

The weight average molecular weight (Mw) of the acrylic copolymer and the active energy ray curable polymer described above is a weight average molecular weight measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement) in terms of standard polystyrene.
<Measurement conditions>
Measuring device: Tosoh Corporation, HLC-8320
GPC columns (passed in the following order): TSK gel super H-H manufactured by Tosoh Corporation
TSK gel superHM-H
TSK gel superH2000
Measurement solvent: tetrahydrofuran Measurement temperature: 40°C

[Examples 2 to 6 and Comparative Examples 1 to 2]
A workpiece processing sheet was produced in the same manner as in Example 1, except that the composition of the active energy radiation curable polymer was changed as shown in Table 1, and the amount of the tin-containing catalyst was adjusted so that the tin atom content in the formed adhesive layer was as shown in Table 1.

Example 7
Except for using a polypropylene film having a thickness of 80 μm as the substrate, a workpiece processing sheet was manufactured in the same manner as in Example 1. The surface resistivity of both sides of the substrate was measured with a DIGITAL ELECTROMETER (manufactured by ADVANTEST) at an applied voltage of 100 V, and was found to be 1.8×10 ¹⁵ Ω/□.

Example 8
Except for using a polybutylene terephthalate film having a thickness of 80 μm as the substrate, a workpiece processing sheet was manufactured in the same manner as in Example 1. The surface resistivity of both sides of the substrate was measured with a DIGITAL ELECTROMETER (manufactured by ADVANTEST) at an applied voltage of 100 V, and was found to be 2.4× ¹⁰ Ω/□.

Example 9
100 parts by weight of polypropylene and 5 parts by weight of a polyolefin block polymer (manufactured by Sanyo Chemical Industries, product name "Pelectron PVL"), which is a polymer-type antistatic agent, were kneaded in a twin-screw kneader, and then extruded into a sheet using an extruder to obtain an antistatic agent-containing polypropylene film having a thickness of 80 μm. A workpiece processing sheet was manufactured in the same manner as in Example 1, except that the film was used as the substrate. The surface resistivity of both sides of the substrate was measured using a DIGITAL ELECTROMETER (manufactured by ADVANTEST) at an applied voltage of 100 V, and was found to be 2.3×10 ¹⁰ Ω/□.

[Test Example 1] (Evaluation of pick-up properties)
A laser marking device (manufactured by Keyence Corporation, product name "MD-S9910A") was used to mark the #2000 polished surface of a silicon wafer (size 8 inches, thickness 350 μm). As a result, a groove with a width of about 50 μm and a depth of about 15 μm in cross section was formed on the polished surface.

Next, the release sheet was peeled off from the workpiece processing sheets produced in the examples and comparative examples, and the exposed adhesive surface was attached to the polished surface after the laser marking using a 2 kg rubber roller, and left for 20 minutes.

Thereafter, the silicon wafer was diced into individual chips having a size of 5 mm×5 mm by dicing under the following dicing conditions using a dicing device (manufactured by Disco Corporation, product name “Fully Auto Dicer DF636”).
Dicing conditions Cutting method: Single cut Blade: Disco Corporation, product name "SD3000-N1-90EC"
Blade rotation speed: 35,000 rpm
Cutting speed: 50 mm/sec
Blade height: 20 μm as cutting depth into the substrate

After dicing, the adhesive layer was irradiated with ultraviolet light from the substrate side of the workpiece processing sheet (light amount: 200 mJ/cm ² ). Then, the obtained chips were picked up from the workpiece processing sheet using a die bonder (Canon Machinery, product name "BESTEM-D02"). At this time, 10 chips were picked up, and when the amount of push-up at the time of successful pick-up was 300 μm or less for all chips, the pick-up ability was evaluated as "good". On the other hand, when there was a chip with an amount of push-up exceeding 300 μm or when there was a chip that could not be picked up, the pick-up ability was evaluated as "poor". The results are shown in Table 1.

[Test Example 2] (Evaluation of adhesive residue)
For the workpiece processing sheets whose pickup property was evaluated as "○" in Test Example 1, the presence or absence of adhesive (glue residue) on the printed portion of the 10 chips picked up was confirmed. Then, the percentage of chips with confirmed adhesive residue out of the 10 chips was calculated. The results are shown in Table 1.

Details of the abbreviations and the like in Table 1 are as follows.
EMAA: Ethylene-methacrylic acid copolymer PP: Polypropylene PBT: Polybutylene terephthalate 2EHA: 2-ethylhexyl acrylate MMA: Methyl methacrylate HEA: 2-hydroxyethyl acrylate MOI: 2-methacryloyloxyethyl isocyanate VAc: Vinyl acetate BA: n-butyl acrylate

As can be seen from Table 1, when the workpiece processing sheet obtained in the example was used, no adhesive residue was left behind.

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

1A, 1B, 1C... Workpiece processing sheet 11a, 11b, 11c... Substrate 111, 111'... Base film 112... Organic conductive film 12... Adhesive layer

Claims (5)

A workpiece processing sheet comprising a substrate and an adhesive layer laminated on one side of the substrate,
The content of tin atoms in the pressure-sensitive adhesive layer is 0.002% by mass or more and 0.015% by mass or less ,
the surface resistivity of the surface of the substrate on which the pressure-sensitive adhesive layer is laminated is 1×10 ^Ω /□ or less;
The workpiece processing sheet is used for dicing,
The workpiece processing sheet does not have an unevenness-absorbing resin layer.
A workpiece processing sheet characterized by the above. The workpiece processing sheet according to claim 1, characterized in that the adhesive layer is composed of an active energy ray-curable adhesive. The workpiece processing sheet according to claim 2, characterized in that the active energy ray-curable adhesive contains a polymer having active energy ray-curability and a tin-containing catalyst containing tin atoms. The active energy ray-curable polymer is a (meth)acrylic acid ester polymer having an active energy ray-curable group introduced into a side chain thereof,
The workpiece processing sheet according to claim 3, characterized in that the (meth)acrylic acid ester polymer is obtained by reacting an acrylic copolymer having a functional group-containing monomer unit with an unsaturated group-containing compound having a functional group bonded to the functional group, under the catalytic action of the tin-containing catalyst. The workpiece processing sheet according to any one of claims 1 to 4 , characterized in that the base material has an organic conductive film on the surface on which the adhesive layer is laminated.

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