JP2024035411A - Adhesive sheet for semiconductor processing and manufacturing method for semiconductor device - Google Patents

Abstract

To provide an adhesive sheet for semiconductor processing with reduced adhesion of grinding debris and a manufacturing method for a semiconductor device using the same.SOLUTION: The adhesive sheet for semiconductor processing has a surface coat layer, a buffer layer, a substrate, and an adhesive layer, in this order. The static contact angle of 1-bromonaphthalene to the surface coat layer at 23°C is 19° or more. The manufacturing method for a semiconductor device using the adhesive sheet for semiconductor processing is provided.SELECTED DRAWING: None

Description

The present invention relates to an adhesive sheet for semiconductor processing and a method for manufacturing a semiconductor device.

2. Description of the Related Art As information terminal devices rapidly become thinner, smaller, and more multifunctional, the semiconductor devices installed in these devices are also required to be thinner and more dense.
As a method for reducing the thickness of a semiconductor device, a method has been used in which the back surface of a semiconductor wafer used in the semiconductor device is ground. Back grinding of a semiconductor wafer is performed by attaching an adhesive sheet for semiconductor processing for back grinding (hereinafter also referred to as a "back grind sheet") to the front surface of the semiconductor wafer, and protecting the front surface of the semiconductor wafer with the sheet. . The back grind sheet is peeled off and removed from the front surface of the semiconductor wafer after back grinding.

In recent years, tip dicing methods, stealth tip dicing methods, and the like have been put into practice as grinding and singulation methods for reducing the thickness of semiconductor chips while suppressing damage to them. The pre-dicing method is a method of forming grooves of a predetermined depth on the surface of a semiconductor wafer using a dicing blade, etc., and then cutting the semiconductor wafer into individual semiconductor chips by grinding the semiconductor wafer from the back side to the grooves. . In addition, in the stealth tip dicing method, after a modified region is formed inside a semiconductor wafer by laser light irradiation, the semiconductor wafer is ground from the back side and the semiconductor chips are cut using the modified region as a starting point for division. This is a method of dividing into individual pieces. Also in these methods, a backgrind sheet is used to protect the surface of the semiconductor wafer.

Along with the development of these thinning process techniques, adhesive sheets for semiconductor processing are also required to have a function for thinning semiconductor chips with good yield, and various studies are being conducted.
Patent Document 1 describes an adhesive sheet for protecting the surface of a semiconductor wafer applicable to the first dicing method or the stealth first dicing method, which includes a base film and an intermediate layer provided on at least one side of the base film and made of an adhesive. and an outermost adhesive layer provided as the outermost layer on the side opposite to the base film of the intermediate layer, wherein the intermediate layer is cured by a curing treatment after forming the adhesive sheet. An adhesive sheet for protecting the surface of a semiconductor wafer is disclosed, which is characterized by being made of a hardening material.

Japanese Patent Application Publication No. 2015-56446

According to the adhesive sheet for protecting the surface of semiconductor wafers disclosed in Patent Document 1, it is possible to suppress kerf shift in which the original chip spacing is disrupted after the semiconductor wafer is diced into chips, and it is also possible to prevent contamination by grinding debris of the semiconductor wafers. It is said that it is possible to suppress adhesive residue on the chip when the surface protection tape is peeled off.

By the way, when performing back grinding, the back grind sheet attached to the semiconductor wafer is fixed with a support device such as a chuck table on the side opposite to the side to be attached to the semiconductor wafer (hereinafter also referred to as the "back side"). Ru. The back surface of the semiconductor wafer fixed on the table of the support device via the back grind sheet is ground while cooling water is supplied to the grinding surface to remove the heat caused by the grinding and the grinding debris.

If there are grinding debris between the back grind sheet and the table of the support device during back grinding, the impact caused when the semiconductor wafer is fixed to the table, starting from the part where the grinding debris is present, and during back grinding. Cracks may occur in semiconductor wafers or semiconductor chips due to pressure, vibration, etc. Grinding debris adheres to the back surface of the back grind sheet while contained in the cooling water, so in order to suppress the occurrence of the above cracks, it is necessary to reduce the amount of grind debris that adheres to the back surface of the back grind sheet. be.
The adhesive sheet for protecting the surface of a semiconductor wafer disclosed in Patent Document 1 has not been able to sufficiently meet the demand for reducing the amount of grinding debris that adheres to the back surface of a backgrind sheet.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a pressure-sensitive adhesive sheet for semiconductor processing in which the amount of adhesion of grinding debris is reduced, and a method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet for semiconductor processing. shall be.

As a result of intensive studies, the present inventors found that a semiconductor processing method having a surface coating layer, a buffer layer, a base material, and an adhesive layer, in which the static contact angle of 1-bromonaphthalene at 23° C. is 19° or more, in this order. The inventors have discovered that the above-mentioned problems can be solved by using a pressure-sensitive adhesive sheet, and have completed the following invention.

That is, the present invention relates to the following [1] to [9].
[1] Having a surface coat layer, a buffer layer, a base material and an adhesive layer in this order,
A pressure-sensitive adhesive sheet for semiconductor processing, wherein a static contact angle of 1-bromonaphthalene at 23° C. with respect to the surface coating layer is 19° or more.
[2] The pressure-sensitive adhesive sheet for semiconductor processing according to [1] above, wherein the surface coat layer is an organic layer containing a resin component.
[3] The pressure-sensitive adhesive sheet for semiconductor processing according to [2] above, wherein the resin component is a polymer of a compound having one or more ethylenically unsaturated bonds.
[4] The pressure-sensitive adhesive sheet for semiconductor processing according to [3] above, wherein the compound having one or more ethylenically unsaturated bonds is a styrene compound.
[5] The pressure-sensitive adhesive sheet for semiconductor processing according to any one of [1] to [4] above, wherein the surface coating layer has a thickness of 0.05 to 10 μm.
[6] The pressure-sensitive adhesive sheet for semiconductor processing according to any one of [1] to [5] above, wherein the buffer layer is a layer formed from a composition for forming a buffer layer containing urethane (meth)acrylate.
[7] The adhesive sheet for semiconductor processing according to any one of [1] to [6] above, which is used for backside grinding of semiconductor wafers.
[8] A step of attaching the adhesive sheet for semiconductor processing according to any one of [1] to [7] above to the surface of a semiconductor wafer using the adhesive layer as an attachment surface;
Grinding the back surface of the semiconductor wafer while the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer is fixed by a support device;
A method for manufacturing a semiconductor device, including:
[9] A dividing line forming step, which is step a of forming a groove on the surface of the semiconductor wafer, or step b of forming a modified region inside the semiconductor wafer from the front or back surface of the semiconductor wafer;
After the step a, or before or after the step b, apply the adhesive sheet for semiconductor processing according to any one of [1] to [7] above to the surface of the semiconductor wafer, using the adhesive layer as a pasting surface. A sheet pasting process for pasting the
With the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer fixed by a support device, the back surface of the semiconductor wafer is ground to form a plurality of semiconductors starting from the groove or the modified region. A grinding and singulation process for singulating into chips;
A method for manufacturing a semiconductor device, including:

According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet for semiconductor processing in which the amount of attached grinding debris is reduced, and a method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet for semiconductor processing.

In this specification, the lower and upper limits described in stages for preferred numerical ranges can be independently combined. For example, from the description "preferably 10 to 90, more preferably 30 to 60", the "preferable lower limit (10)" and "more preferable upper limit (60)" are combined to become "10 to 60". You can also do that.

As used herein, the term "active ingredient" refers to the components contained in the target composition, excluding the diluting solvent.

In this specification, for example, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid," and the same applies to other similar terms.

As used herein, the term "energy ray" refers to electromagnetic waves or charged particle beams that have energy quanta, examples of which include ultraviolet rays, radiation, electron beams, and the like. The ultraviolet rays can be irradiated using, for example, an electrodeless lamp, high pressure mercury lamp, metal halide lamp, UV-LED, etc. as an ultraviolet source. The electron beam can be generated by an electron beam accelerator or the like.
As used herein, "energy ray polymerizability" means the property of polymerizing by irradiation with energy rays. Further, "energy ray curable" means a property of being cured by irradiation with energy rays, and "non-energy ray curable" means a property of not having energy ray curability.

In this specification, the "front surface" of a semiconductor wafer refers to the surface on which circuits are formed, and the "back surface" refers to the surface on which circuits are not formed.

The mechanism of action described in this specification is speculative and does not limit the mechanism by which the adhesive sheet for semiconductor processing of the present invention exerts its effects.

[Adhesive sheet for semiconductor processing]
The adhesive sheet for semiconductor processing (hereinafter also referred to as "adhesive sheet") of the present embodiment has a surface coat layer, a buffer layer, a base material, and an adhesive layer in this order, and has a 1- This is an adhesive sheet for semiconductor processing, in which the static contact angle of bromonaphthalene at 23°C is 19° or more.

The adhesive sheet of this embodiment is attached to the surface of a semiconductor device as a workpiece, and is used to perform predetermined processing on the semiconductor device while protecting the surface. After performing predetermined processing on the workpiece, the adhesive sheet of this embodiment is peeled off and removed from the semiconductor device.
Note that in this embodiment, a "semiconductor device" refers to any device that can function by utilizing semiconductor characteristics, and includes, for example, a semiconductor wafer, a semiconductor chip, an electronic component including the semiconductor chip, and a device equipped with the electronic component. Examples include electronic devices. Among these, the adhesive sheet of this embodiment is suitable for processing semiconductor wafers.

The reason why the adhesive sheet of this embodiment has a reduced amount of adhesion of grinding debris is not certain, but it is presumed as follows.
The surface coating layer of the pressure-sensitive adhesive sheet of this embodiment has a static contact angle of 19° or more at 23° C. with 1-bromonaphthalene. It is assumed that a surface coating layer in which the static contact angle of 1-bromonaphthalene at 23° C. is 19° or more is difficult to wet with water containing grinding debris, and as a result, the amount of attached grinding debris is reduced.

The pressure-sensitive adhesive sheet of this embodiment may or may not have layers other than the surface coat layer, buffer layer, base material, and pressure-sensitive adhesive layer. Layers other than the surface coat layer, buffer layer, base material, and adhesive layer include, for example, an intermediate layer provided between the base material and the adhesive layer, and an adhesive layer provided on the side opposite to the base material. For example, a release sheet may be used.
Hereinafter, each member constituting the adhesive sheet of this embodiment will be explained in order.

<Surface coat layer>
The surface coating layer is a layer provided on the side of the buffer layer opposite to the base material, and is a layer fixed by a support device when processing a semiconductor device.

(Contact angle of 1-bromonaphthalene in surface coating layer)
The static contact angle of 1-bromonaphthalene at 23° C. (hereinafter also simply referred to as "1-bromonaphthalene contact angle") with respect to the surface coating layer of the pressure-sensitive adhesive sheet of this embodiment is 19° or more.
When the 1-bromonaphthalene contact angle of the surface coating layer is 19° or more, the amount of grinding debris adhering to the pressure-sensitive adhesive sheet of this embodiment can be reduced.
The 1-bromonaphthalene contact angle of the surface coating layer is preferably 20° or more, more preferably 21° or more, from the viewpoint of further reducing the amount of adhesion of grinding debris.
The upper limit of the 1-bromonaphthalene contact angle of the surface coating layer is not particularly limited, but from the viewpoint of ease of manufacture, it may be, for example, 50° or less, 40° or less, 35° or less. It may be.
The 1-bromonaphthalene contact angle of the surface coating layer is a value measured in accordance with JIS R 3257:1999, and specifically can be measured by the method described in Examples.

The surface coating layer of the adhesive sheet of this embodiment may be an inorganic layer or an organic layer, but from the viewpoint of productivity and handling of the adhesive sheet, it is preferably an organic layer. More preferably, it is an organic layer containing a resin component.

(resin component)
As the resin component, a thermoplastic resin is preferable from the viewpoint of reducing the amount of adhesion of grinding debris.
One type of resin component may be used alone, or two or more types may be used in combination.

〔Thermoplastic resin〕
The thermoplastic resin is preferably a polymer of a compound having one or more ethylenically unsaturated bonds (hereinafter also referred to as "polymer (1)") from the viewpoint of further reducing the amount of adhesion of grinding debris. .
Note that the "ethylenic unsaturated bond" in this embodiment means a carbon-carbon double bond capable of an addition reaction, and does not include a double bond of an aromatic ring.

The content of the structural unit derived from a compound having one or more ethylenically unsaturated bonds in the polymer (1) is not particularly limited, but is preferably 70% by mass or more, more preferably 90% by mass or more, and Preferably it is 95% by mass or more. When the content of the structural unit derived from a compound having one or more ethylenically unsaturated bonds is at least the above lower limit, the amount of adhesion of grinding debris tends to be further reduced.
Further, the content of structural units derived from a compound having one or more ethylenically unsaturated bonds in the polymer (1) may be 100% by mass, but for example, the content of structural units derived from other monomers may be 100% by mass. In order to contain the unit, it may be 99.5% by mass or less, or 99% by mass or less.

Examples of compounds having one or more ethylenically unsaturated bonds include styrene compounds such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, chlorostyrene, and methoxystyrene; ethylene, propylene, 1- Butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, Chain monoolefins such as 5-methyl-1-hexene; chain nonconjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, and 5-methyl-1,4-hexadiene Conjugated dienes such as 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene Conjugated diolefin); Cyclic monoolefins such as cyclobutene, cyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, cycloheptene, cyclooctene; Cyclic monoolefins such as cyclohexadiene, methylcyclohexadiene, cyclooctadiene, methylcyclooctadiene, phenylcyclooctadiene, etc. Diolefin; norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, tetracyclo[7.4.0.110,13.02,7]trideca-2,4,6, Polycyclic olefins such as 11-tetraene; monomers having oxygen atoms and ethylenically unsaturated bonds such as maleic anhydride and vinyl acetate; monomers having nitrogen atoms and ethylenically unsaturated bonds such as maleimide compounds and nitrile monomers; etc. can be mentioned.

Among the above options, it is preferable that the polymer (1) contains a structural unit derived from a styrene compound. Hereinafter, the polymer (1) containing a structural unit derived from a styrene compound will be referred to as a "styrene resin."

The content of the structural unit derived from the styrene compound in the styrenic resin is not particularly limited, but is preferably 50% by mass or more, more preferably 55% by mass or more, and still more preferably 60% by mass or more.
When the content of the structural unit derived from the styrene compound in the styrene resin is at least the above lower limit, the heat resistance of the surface coat layer tends to be good.
Further, the content of the structural unit derived from the styrene compound in the styrenic resin is not particularly limited, but is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less.
If the content of structural units derived from styrene-based compounds in the styrene-based resin is below the above upper limit, the amount of adhesion of grinding debris and heat resistance may be reduced by introducing structural units other than those derived from styrene-based compounds. It tends to be easier to maintain a good balance.

Examples of structural units other than those derived from styrene compounds that may be contained in the styrenic resin include those derived from compounds other than styrene compounds listed above as compounds having one or more ethylenically unsaturated bonds. Examples include structural units. Among these, it is more preferable that the styrenic resin contains a structural unit derived from a conjugated diene.
The structural unit derived from a conjugated diene refers to a structural unit formed by addition polymerization of the conjugated diene, a structural unit formed by hydrogenating a structural unit formed by addition polymerization of the conjugated diene, etc. be.
Examples of the structural unit formed by hydrogenating a structural unit formed by addition polymerization of conjugated diene include ethylene-formed by hydrogenating a structural unit formed by addition polymerization of isoprene. These include propylene units, ethylene-butylene units formed by hydrogenating structural units formed by addition polymerization of 1,3-butadiene, and the like.
When the styrenic resin contains a structural unit derived from a conjugated diene, the content in the styrenic resin is not particularly limited, but is preferably 20 to 50% by mass, more preferably 25 to 45% by mass, and even more preferably is 30 to 40% by mass.
When the content of the structural unit derived from the conjugated diene in the styrene resin is equal to or higher than the above lower limit, the amount of adhesion of grinding debris tends to be further reduced. Moreover, when the content of the structural unit derived from the conjugated diene in the styrene resin is below the above-mentioned upper limit, the transportability after processing the workpiece tends to be good.

From the viewpoint of the amount of adhesion of grinding dust and heat resistance, styrene-based resins include styrene-butadiene block copolymer, styrene-ethylene-propylene block copolymer, styrene-butadiene-styrene block copolymer, and styrene-isoprene-styrene. From the group consisting of block copolymers, styrene-ethylene-butylene-styrene block copolymers (hereinafter also referred to as "SEBS") and styrene-ethylene-propylene-styrene block copolymers (hereinafter also referred to as "SEPS") One or more types selected from the group consisting of styrene-ethylene-butylene-styrene block copolymers and styrene-ethylene-propylene-styrene block copolymers are more preferable.

Examples of polymers (1) other than styrene resins include homopolymers such as polyethylene, polypropylene, and polybutadiene; ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-maleic anhydride copolymers, ethylene - Vinyl acetate copolymer, ethylene-(meth)acrylate copolymer, ethylene-tetracyclododecene copolymer, propylene-butene copolymer, propylene-maleic anhydride copolymer, propylene-vinyl acetate copolymer , propylene-(meth)acrylate copolymer, propylene-tetracyclododecene copolymer and other binary copolymers; ethylene-maleic anhydride-vinyl acetate copolymer, ethylene-maleic anhydride-(meth)acrylate copolymer, ethylene-vinyl acetate-(meth)acrylate copolymer, propylene-maleic anhydride-vinyl acetate copolymer, propylene-maleic anhydride-(meth)acrylate copolymer, propylene-vinyl acetate-(meth)acrylate copolymer, ) acrylate copolymer, ethylene-propylene-maleic anhydride copolymer, ethylene-propylene-vinyl acetate copolymer, ethylene-propylene-(meth)acrylate copolymer, ethylene-butene-maleic anhydride copolymer, Ethylene-butene-vinyl acetate copolymer, ethylene-butene-(meth)acrylate copolymer, propylene-butene-maleic anhydride copolymer, propylene-butene-vinyl acetate copolymer, propylene-butene-(meth) Examples include multicomponent polymers such as acrylate copolymers; and the like.

The weight average molecular weight (Mw) of the thermoplastic resin is not particularly limited, but is preferably 10,000 to 600,000, more preferably 15,000 to 500,000, and even more preferably 20,000 to 400,000. .
When the mass average molecular weight (Mw) of the thermoplastic resin is equal to or greater than the above lower limit, the transportability after processing the workpiece tends to be better. Moreover, when the mass average molecular weight (Mw) of the thermoplastic resin is less than or equal to the above upper limit, the solvent solubility of the thermoplastic resin tends to improve, and the formation of a surface coat layer by coating tends to become easier.
In addition, in this embodiment, the mass average molecular weight (Mw) means a value measured by gel permeation chromatography (GPC) method in terms of standard polystyrene, and specifically, it is measured by the method described in Examples. This is the value.

The content of the resin component in the surface coat layer is not particularly limited, but is preferably 30 to 95% by mass, more preferably 40 to 90% by mass, and even more preferably is 45 to 80% by mass.
When the content of the resin component is within the above range, the amount of attached grinding debris tends to be further reduced.

(Hydrophobized silica)
It is preferable that the surface coat layer further contains hydrophobized silica together with the resin component.
Since the surface coat layer contains hydrophobized silica, the adhesive sheet of this embodiment tends to have a further reduced amount of adhesion of grinding debris.
One type of hydrophobized silica may be used alone, or two or more types may be used in combination.

Examples of hydrophobized silica include raw silica surface-treated with a hydrophobizing agent.
The raw material silica to be hydrophobized may be, for example, wet silica produced by a wet method such as a precipitation method, gel method, or sol-gel method, or may be dry method silica such as fumed silica or fused silica. . Among these, wet silica is preferred, and precipitated silica is more preferred, from the viewpoint of easy hydrophobization.

Examples of the hydrophobizing agent include organosilicon compounds, fatty acids, fatty acid metal salts, and the like.
One type of hydrophobizing agent may be used alone, or two or more types may be used in combination.

Methods for surface treating raw silica with a hydrophobizing agent include, for example, a method in which the raw silica and the hydrophobizing agent are brought into contact with each other in a solvent, and a method in which the vapor of the hydrophobizing agent carried by a carrier gas such as nitrogen is applied to the raw silica. Examples include a method of bringing the hydrophobizing treatment agent into direct contact with the raw material silica, and a method of bringing the undiluted solution of the hydrophobizing agent into direct contact with the raw material silica.

The shape of the hydrophobized silica is not particularly limited, and examples thereof include spherical and amorphous shapes. Among these, an amorphous shape is preferable from the viewpoint of further reducing the amount of adhesion of grinding debris.

Examples of hydrophobized silica include "AEROSIL (registered trademark) series" manufactured by Evonik, "QSG series" manufactured by Shin-Etsu Chemical Co., Ltd., and "Nipsil (registered trademark) SS manufactured by Tosoh Silica Corporation. "SYLOPHOBIC (registered trademark) series" manufactured by Fuji Silicia Chemical Co., Ltd. are commercially available.

When the surface coat layer contains hydrophobized silica, the content of the hydrophobized silica in the surface coat layer is not particularly limited, but is preferably 1 to 150 parts by mass based on 100 parts by mass of the resin component. Parts by weight, more preferably 10 to 120 parts by weight, even more preferably 20 to 100 parts by weight, even more preferably 30 to 90 parts by weight.
When the content of hydrophobized silica is equal to or higher than the above lower limit, the amount of adhesion of grinding debris tends to be further reduced. Furthermore, when the content of hydrophobized silica is below the above upper limit, the film formability of the surface coating layer tends to improve.

The surface coat layer may contain components other than the resin component and hydrophobized silica.
For example, from the viewpoint of improving the adhesion with the buffer layer, the surface coat layer applies energy rays to a composition containing a resin component, an energy ray polymerizable polyfunctional compound, and a photopolymerization initiator. Preferably, the layer is formed by irradiation.
In addition, in the following description, the composition used to form a surface coat layer may be referred to as a "composition for forming a surface coat layer."

(Energy ray polymerizable polyfunctional compound)
The energy ray polymerizable polyfunctional compound is a compound having two or more energy ray polymerizable functional groups.
The energy ray polymerizable polyfunctional compounds may be used alone or in combination of two or more.

The number of energy ray polymerizable functional groups possessed by the energy ray polymerizable polyfunctional compound is preferably 2 to 10, more preferably 3 to 8, and still more preferably 4 to 7.
As the energy ray polymerizable functional group that the energy ray polymerizable polyfunctional compound has, a (meth)acryloyl group is preferable.

As the energy beam polymerizable polyfunctional compound, polyfunctional (meth)acrylate monomers are preferred.
Examples of polyfunctional (meth)acrylate monomers include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate. ) acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone modified dicyclopentenyl di(meth)acrylate, ethylene oxide modified phosphoric acid Bifunctional (meth)acrylate monomers such as di(meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, isocyanuric acid ethylene oxide-modified diacrylate; trimethylolpropane tri(meth)acrylate; Dipentaerythritol tri(meth)acrylate, propionic acid modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl)isocyanurate, Bis(acryloxyethyl)hydroxyethyl isocyanurate, isocyanuric acid ethylene oxide modified triacrylate, ε-caprolactone modified tris(acryloxyethyl)isocyanurate, diglycerin tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, propionic acid Examples include modified dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate. Among these, dipentaerythritol hexaacrylate and dipentaerythritol penta(meth)acrylate are preferred, and dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate are more preferred.

When the composition for forming a surface coat layer contains an energy ray polymerizable polyfunctional compound, the content of the energy ray polymerizable polyfunctional compound is preferably 10 to 60 parts by mass, more preferably 10 to 60 parts by mass, based on 100 parts by mass of the resin component. The amount is preferably 14 to 40 parts by weight, more preferably 17 to 30 parts by weight.
When the content of the energy beam polymerizable polyfunctional compound is at least the above lower limit, the surface coat layer tends to have excellent adhesion to the buffer layer. Moreover, when the content of the energy ray polymerizable polyfunctional compound is below the above-mentioned upper limit, it tends to be easy to maintain a good balance between the adhesion to the buffer layer and the amount of grinding debris deposited.

(Photopolymerization initiator)
Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones, and more. Specifically, for example, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzylphenyl sulfide, Examples include tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and the like.
One type of photopolymerization initiator may be used alone, or two or more types may be used in combination.

When the composition for forming a surface coat layer contains a photopolymerization initiator, the content is not particularly limited, but from the viewpoint of homogeneously and sufficiently proceeding the energy beam polymerization reaction, the energy beam polymerizable polyfunctional compound 100 The amount is preferably 0.01 to 10 parts by weight, more preferably 0.03 to 7 parts by weight, and even more preferably 0.05 to 5 parts by weight.

(Other ingredients)
The surface coat layer may contain other components other than those mentioned above, within a range that does not impair the effects of the present invention. Other components include, for example, resins other than those mentioned above; additives such as antistatic agents, antioxidants, softeners, fillers, rust preventives, pigments, and dyes; and the like.

(Thickness of surface coating layer)
The thickness of the surface coating layer is not particularly limited, but is preferably 0.05 to 10 μm, more preferably 0.2 to 7 μm, and even more preferably 1 to 4 μm.
When the thickness of the surface coat layer is equal to or greater than the above lower limit, uniform layer formation becomes possible, and the amount of adhesion of grinding debris tends to be further reduced. Furthermore, if the thickness of the surface coating layer is less than or equal to the above upper limit, the effect of the buffer layer of absorbing irregularities such as foreign matter on the chuck table tends to be easily obtained.

<Buffer layer>
The buffer layer is a layer provided between the base material and the surface coating layer, and serves to absorb vibrations, shocks, etc. that occur during back grinding, and to prevent cracks from occurring in the workpiece. Furthermore, by providing a buffer layer, unevenness such as foreign matter present on the table of the support device can be absorbed, thereby improving the ability of the support device to hold the pressure-sensitive adhesive sheet.

(Buffer layer forming composition)
The buffer layer can be formed from a composition for forming a buffer layer.
From the viewpoint of obtaining physical properties suitable for a buffer layer, the buffer layer is preferably a layer obtained by curing a composition for forming a buffer layer containing an energy ray polymerizable compound with energy rays.
It is preferable that the composition for forming a buffer layer contains urethane (meth)acrylate (a1) as an energy ray polymerizable compound. When the composition for forming a buffer layer contains urethane (meth)acrylate (a1), the storage modulus of the buffer layer, etc. tends to be adjusted to a favorable range.
From the same viewpoint, the composition for forming a buffer layer also contains, in addition to urethane (meth)acrylate (a1), a polymerizable compound (a2) having an alicyclic group or a heterocyclic group having 6 to 20 ring atoms. and a functional group-containing polymerizable compound (a3), and in addition to urethane (meth)acrylate (a1), a polymer having 6 to 20 ring atoms. It is more preferable to contain a polymerizable compound (a2) having a cyclic group or a heterocyclic group and a polymerizable compound (a3) having a functional group.
In this specification, the number of ring-forming atoms refers to the number of atoms constituting the ring itself of a compound having a structure in which atoms are bonded in a cyclic manner, and refers to the number of atoms constituting the ring itself of a compound having a structure in which atoms are bonded in a cyclic manner. (bonded hydrogen atoms), and atoms contained in substituents when the ring is substituted with a substituent are not included in the number of ring-forming atoms.

[Urethane (meth)acrylate (a1)]
Urethane (meth)acrylate (a1) is a compound having a (meth)acryloyl group and a urethane bond, and has the property of polymerizing when irradiated with energy rays.
Urethane (meth)acrylate (a1) may be used alone or in combination of two or more.

The weight average molecular weight (Mw) of the urethane (meth)acrylate (a1) is not particularly limited, but is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, even more preferably 3,000 to 20,000.

The number of (meth)acryloyl groups that urethane (meth)acrylate (a1) has in one molecule is not particularly limited, but is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. It is individual.

Urethane (meth)acrylate (a1) can be obtained, for example, by reacting a (meth)acrylate having a hydroxy group with a terminal isocyanate urethane prepolymer obtained by reacting a polyol compound and a polyvalent isocyanate compound. .

The polyol compound is not particularly limited as long as it is a compound having two or more hydroxy groups.
Specific examples of polyol compounds include alkylene diols, polyether polyols, polyester polyols, polycarbonate polyols, and the like. Among these, polyester type polyols are preferred.
The polyol compound may be any of a bifunctional diol, a trifunctional triol, and a tetrafunctional or higher functional polyol, but a bifunctional diol is preferable, and a polyester type diol is more preferable.
One type of polyol compound may be used alone, or two or more types may be used in combination.

Examples of polyvalent isocyanate compounds include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; isophorone diisocyanate, norbornane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and dicyclohexylmethane-2 , 4'-diisocyanate, ω, ω'-diisocyanate, alicyclic diisocyanates such as dimethylcyclohexane; 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, toridine diisocyanate, tetramethylene xylylene diisocyanate, naphthalene. Aromatic diisocyanates such as 1,5-diisocyanate; and the like. Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferred.
One type of polyvalent isocyanate compound may be used alone, or two or more types may be used in combination.

The (meth)acrylate having a hydroxy group to be reacted with the terminal isocyanate urethane prepolymer is not particularly limited as long as it is a compound having a hydroxy group and a (meth)acryloyl group in at least one molecule.
Examples of (meth)acrylates having a hydroxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 5 -Hydroxyalkyl such as hydroxycyclooctyl (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, etc. (Meth)acrylate; Hydroxy group-containing (meth)acrylamide such as N-methylol (meth)acrylamide; Reactant obtained by reacting diglycidyl ester of vinyl alcohol, vinylphenol, or bisphenol A with (meth)acrylic acid; etc. can be mentioned. Among these, hydroxyalkyl (meth)acrylate is preferred, and 2-hydroxyethyl (meth)acrylate is more preferred.
One type of (meth)acrylate having a hydroxy group may be used alone, or two or more types may be used in combination.

The conditions for reacting the terminal isocyanate urethane prepolymer with the (meth)acrylate having a hydroxyl group are not particularly limited, but for example, at 60 to 100°C in the presence of an organic solvent, catalyst, etc. added as necessary. The conditions can be such that the reaction is carried out for 1 to 4 hours.

The content of urethane (meth)acrylate (a1) in the composition for forming a buffer layer is not particularly limited, but is preferably 10 to 10% based on the total amount (100% by mass) of the active ingredients of the composition for forming a buffer layer. The amount is 70% by weight, more preferably 20 to 60% by weight, and even more preferably 30 to 50% by weight.

[Polymerizable compound (a2) having an alicyclic group or heterocyclic group having 6 to 20 ring atoms]
The buffer layer forming composition contains a polymerizable compound (a2) having an alicyclic group or a heterocyclic group having 6 to 20 ring atoms (hereinafter referred to as "a polymerizable compound having an alicyclic group or a heterocyclic group (a2)") ), the film-forming properties of the composition for forming a buffer layer tend to improve.
Examples of atoms forming the ring structure of the heterocyclic group include carbon atoms, nitrogen atoms, oxygen atoms, and sulfur atoms.
The polymerizable compound (a2) having an alicyclic group or a heterocyclic group may be used alone or in combination of two or more.

The polymerizable compound (a2) having an alicyclic group or a heterocyclic group is preferably a compound having a (meth)acryloyl group.
The number of (meth)acryloyl groups that the polymerizable compound (a2) having an alicyclic group or a heterocyclic group has in one molecule is not particularly limited, but is preferably one or more, more preferably one or two, More preferably, it is one.

The number of ring atoms of the alicyclic group or heterocyclic group possessed by the polymerizable compound (a2) having an alicyclic group or heterocyclic group is 6 to 20, preferably 6 to 18, more preferably 6 to 16, More preferably, it is 7-12.

Examples of the polymerizable compound (a2) having an alicyclic group or a heterocyclic group include isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyloxy (meth)acrylate. (meth)acrylates containing alicyclic groups such as acrylate, cyclohexyl (meth)acrylate and adamantane (meth)acrylate; (meth)acrylates containing heterocyclic groups such as tetrahydrofurfuryl (meth)acrylate and morpholine (meth)acrylate; etc. Can be mentioned. Among these, alicyclic group-containing (meth)acrylates are preferred, and isobornyl (meth)acrylates are more preferred.

The content of the polymerizable compound (a2) having an alicyclic group or a heterocyclic group in the composition for forming a buffer layer is not particularly limited, but may be based on the total amount (100% by mass) of the active ingredients of the composition for forming a buffer layer. On the other hand, it is preferably 10 to 70% by weight, more preferably 20 to 60% by weight, and even more preferably 30 to 50% by weight.

[Polymerizable compound (a3) having a functional group]
When the composition for forming a buffer layer contains the polymerizable compound (a3) having a functional group, the viscosity of the composition for forming a buffer layer tends to be adjusted to an appropriate range.
The polymerizable compound (a3) having a functional group may be used alone or in combination of two or more.

Examples of the functional group contained in the polymerizable compound (a3) having a functional group include a hydroxyl group, an epoxy group, an amide group, and an amino group.
The number of functional groups in one molecule of the polymerizable compound (a3) having a functional group is 1 or more, preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. be.

The polymerizable compound (a3) having a functional group is preferably a compound having a (meth)acryloyl group in addition to the functional group.
The number of (meth)acryloyl groups that the functional group-containing polymerizable compound (a3) has in one molecule is not particularly limited, but is preferably 1 or more, more preferably 1 or 2, and even more preferably 1. It is.

Examples of the polymerizable compound (a3) having a functional group include a hydroxyl group-containing polymerizable compound, an epoxy group-containing polymerizable compound, an amide group-containing polymerizable compound, an amino group-containing polymerizable compound, and the like.

Examples of hydroxyl group-containing polymerizable compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-hydroxybutyl Hydroxyl group-containing (meth)acrylates such as (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate; vinyl ether compounds such as hydroxyethyl vinyl ether and hydroxybutyl vinyl ether; It will be done.

Examples of the epoxy group-containing polymerizable compound include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, and allylglycidyl ether.

Examples of the amide group-containing polymerizable compound include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, and N-methylolpropane(meth)acrylamide. , N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-vinylformamide and the like.

Examples of amino group-containing polymerizable compounds include amino group-containing (meth)acrylates such as primary amino group-containing (meth)acrylates, secondary amino group-containing (meth)acrylates, and tertiary amino group-containing (meth)acrylates. ) acrylate, etc.

Among these, hydroxyl group-containing (meth)acrylates are preferred, and hydroxyl group-containing (meth)acrylates having an aromatic ring such as 2-hydroxy-3-phenoxypropyl (meth)acrylate are more preferred.

The content of the polymerizable compound (a3) having a functional group in the composition for forming a buffer layer is not particularly limited, but preferably based on the total amount (100% by mass) of the active ingredients of the composition for forming a buffer layer. The amount is 5 to 40% by weight, more preferably 10 to 30% by weight, and even more preferably 15 to 25% by weight.

[Other polymerizable compounds]
The composition for forming a buffer layer may contain other polymerizable compounds other than components (a1) to (a3) as long as the effects of the present invention are not impaired.
Other polymerizable compounds include, for example, alkyl (meth)acrylates having an alkyl group having 1 to 20 carbon atoms; vinyl compounds such as styrene, N-vinylpyrrolidone, and N-vinylcaprolactam; and the like.
One type of other polymerizable compounds may be used alone, or two or more types may be used in combination.
The content of other polymerizable compounds in the composition for forming a buffer layer is not particularly limited, but is preferably 0 to 20% by mass based on the total amount (100% by mass) of the active ingredients of the composition for forming a buffer layer. , more preferably 0 to 10% by weight, and even more preferably 0 to 2% by weight.

[Photopolymerization initiator]
The composition for forming a buffer layer containing an energy ray polymerizable compound preferably further contains a photopolymerization initiator from the viewpoint of reducing the polymerization time and energy ray irradiation amount due to energy ray irradiation.
One type of photopolymerization initiator may be used alone, or two or more types may be used in combination.

Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones, and more. Specifically, for example, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzylphenyl sulfide, Examples include tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and the like. Among these, 1-hydroxycyclohexyl phenyl ketone is preferred.

The content of the photopolymerization initiator in the composition for forming a buffer layer is not particularly limited, but from the viewpoint of homogeneously and sufficiently proceeding the energy ray curing reaction, it is preferably set to 100 parts by mass of the energy ray polymerizable compound. is 0.05 to 15 parts by weight, more preferably 0.1 to 10 parts by weight, even more preferably 0.3 to 5 parts by weight.

(Other ingredients)
The composition for forming a buffer layer may contain other components as long as the effects of the present invention are not impaired. Other components include, for example, resin components other than the resins described above; other additives such as antistatic agents, antioxidants, softeners, fillers, rust preventives, pigments, and dyes; and the like.

(Young's modulus of buffer layer)
The Young's modulus of the buffer layer at 23° C. is smaller than the Young's modulus of the base material at 23° C., specifically, preferably less than 1,200 MPa, more preferably less than 1,000 MPa, and still more preferably less than 900 MPa. Also. The Young's modulus of the buffer layer at 23° C. is preferably 50 MPa or more, more preferably 100 MPa or more.
When the Young's modulus at 23° C. of the buffer layer is below the above upper limit, the effect of absorbing vibrations, shocks, etc. generated during back grinding and the retention of the pressure-sensitive adhesive sheet tend to improve. Moreover, when the Young's modulus of the buffer layer at 23° C. is equal to or higher than the above lower limit, it tends to be possible to suppress excessive deformation of the buffer layer when processing a workpiece.
The Young's modulus of the buffer layer at 23° C. can be measured at a test speed of 200 mm/min in accordance with JIS K 7127:1999.

(Stress relaxation rate of buffer layer)
The stress relaxation rate of the buffer layer is not particularly limited, but is preferably 70 to 100%, more preferably 75 to 100%, and still more preferably 78 to 98%.
When the stress relaxation rate of the buffer layer is within the above range, the effect of absorbing vibrations, shocks, etc. generated during back grinding and the retention of the adhesive sheet tend to be high.
The stress relaxation rate of the buffer layer is determined by the stress A (N /m ² ) and stress B (N/m ² ) one minute after stopping the extension, using the following formula.
Stress relaxation rate (%) = 100 x (AB)/A (%)

(thickness of buffer layer)
The thickness of the buffer layer is not particularly limited, but is preferably 5 to 70 μm, more preferably 7 to 50 μm, and still more preferably 10 to 40 μm.
When the thickness of the buffer layer is at least the above lower limit, the effect of absorbing vibrations, shocks, etc. generated during back grinding and the retention of the adhesive sheet tend to be high. Moreover, when the thickness of the buffer layer is less than or equal to the above upper limit value, it tends to be possible to suppress excessive deformation of the buffer layer when processing a workpiece.

<Adhesive layer>
The adhesive layer is a layer provided on the opposite side of the base material from the buffer layer, and is a layer that is attached to the workpiece.
The adhesive layer is preferably a layer formed from an energy ray-curable adhesive. By forming the adhesive layer from an energy ray-curable adhesive, the workpiece surface can be well protected with sufficient adhesiveness before energy ray curing, and the peeling force is reduced after energy ray curing. , it can be easily peeled off from the workpiece.

Examples of energy ray-curable adhesives include the following X-type adhesive compositions, Y-type adhesive compositions, and XY-type adhesive compositions.
X-type adhesive composition: an energy ray curable adhesive composition containing a non-energy ray curable adhesive resin (hereinafter also referred to as "adhesive resin I") and an energy ray curable compound other than the adhesive resin. Adhesive composition Y-type adhesive composition: Energy ray curable adhesive resin in which an unsaturated group is introduced into the side chain of a non-energy ray curable adhesive resin (hereinafter also referred to as "adhesive resin II") ) and does not contain any energy ray curable compounds other than the adhesive resin XY type adhesive composition: the above energy ray curable adhesive resin II and a material other than the adhesive resin An energy ray curable adhesive composition containing an energy ray curable compound and: Among these, the energy ray curable adhesive is preferably an XY type adhesive composition. By using an XY type adhesive composition, it tends to have sufficient tackiness before curing, while being able to sufficiently reduce the peeling force against the workpiece after curing.

The adhesive forming the adhesive layer may be a layer formed from a non-energy ray-curable adhesive that does not harden even when irradiated with energy rays.
Examples of non-energy ray-curable adhesives include those that contain adhesive resin I but do not contain adhesive resin II and energy ray-curable compound.

Next, each component constituting the adhesive layer will be explained in more detail.
In the following description, the term "adhesive resin" is used to refer to one or both of adhesive resin I and adhesive resin II. In addition, in the following description, when simply stating "adhesive composition", it refers to X-type adhesive composition, Y-type adhesive composition, XY-type adhesive composition, and other adhesive compositions. The concept also includes things.

Examples of adhesive resins include acrylic resins, urethane resins, rubber resins, and silicone resins. Among these, acrylic resins are preferred.

(acrylic resin)
It is preferable that the acrylic resin contains a structural unit derived from alkyl (meth)acrylate.
Examples of the alkyl (meth)acrylate include alkyl (meth)acrylates in which the alkyl group has 1 to 20 carbon atoms.
The alkyl group that the alkyl (meth)acrylate has may be linear or branched.

The acrylic resin preferably contains a structural unit derived from an alkyl (meth)acrylate whose alkyl group has 4 or more carbon atoms, from the viewpoint of further improving the adhesive force of the adhesive layer.
The structural units derived from alkyl (meth)acrylates whose alkyl groups have 4 or more carbon atoms contained in the acrylic resin may be used alone or in combination of two or more.
The alkyl (meth)acrylate having an alkyl group having 4 or more carbon atoms preferably has 4 to 12 carbon atoms, more preferably 4 to 8 carbon atoms, and still more preferably 4 to 6 carbon atoms.
Examples of alkyl (meth)acrylates whose alkyl group has 4 or more carbon atoms include butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl ( Examples include meth)acrylate, decyl(meth)acrylate, undecyl(meth)acrylate, and dodecyl(meth)acrylate. Among these, butyl (meth)acrylate is preferred, and butyl acrylate is more preferred.
When the acrylic resin contains a structural unit derived from an alkyl (meth)acrylate whose alkyl group has 4 or more carbon atoms, the content of the acrylic resin is determined from the viewpoint of further improving the adhesive strength of the adhesive layer. In the system resin, it is preferably 30 to 90% by weight, more preferably 40 to 80% by weight, and even more preferably 45 to 60% by weight.

From the viewpoint of improving the storage elastic modulus G' and adhesive properties of the adhesive layer, acrylic resins contain structural units derived from alkyl (meth)acrylates in which the alkyl group has 4 or more carbon atoms and It is preferable to contain a structural unit derived from an alkyl (meth)acrylate having 1 to 3 carbon atoms.
The structural unit derived from an alkyl (meth)acrylate whose alkyl group has 1 to 3 carbon atoms contained in the acrylic resin may be one type alone or two or more types.
Examples of alkyl (meth)acrylates in which the alkyl group has 1 to 3 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, and n-propyl (meth)acrylate. . Among these, methyl (meth)acrylate and ethyl (meth)acrylate are preferred, methyl (meth)acrylate is more preferred, and methyl methacrylate is even more preferred.
When the acrylic resin contains a structural unit derived from an alkyl (meth)acrylate in which the alkyl group has 1 to 3 carbon atoms, the content thereof is preferably 1 to 35% by mass, more preferably 1 to 35% by mass in the acrylic resin. It is preferably 5 to 30% by weight, more preferably 15 to 25% by weight.

It is preferable that the acrylic resin further contains a structural unit derived from a functional group-containing monomer.
Because the acrylic resin contains a structural unit derived from a functional group-containing monomer, it reacts with the functional group as a crosslinking origin that reacts with a crosslinking agent, or with an unsaturated group-containing compound, resulting in undesirable properties in the side chains of the acrylic resin. Functional groups can be introduced that make it possible to introduce saturated groups.
The structural units derived from the functional group-containing monomer contained in the acrylic resin may be one type alone or two or more types.

Examples of the functional group-containing monomer include hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, and epoxy group-containing monomers. Among these, hydroxyl group-containing monomers and carboxyl group-containing monomers are preferred, and hydroxyl group-containing monomers are more preferred.
Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-hydroxybutyl (meth)acrylate. ) acrylate, hydroxyalkyl (meth)acrylate such as 4-hydroxybutyl (meth)acrylate; unsaturated alcohol such as vinyl alcohol, allyl alcohol; and the like.
Carboxy group-containing monomers include, for example, ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid, and citraconic acid, and their anhydrides. ; 2-carboxyethyl methacrylate; and the like.

When the acrylic resin contains a structural unit derived from a functional group-containing monomer, its content is not particularly limited, but is preferably 5 to 45% by mass, more preferably 15 to 40% by mass in the acrylic resin. , more preferably 25 to 35% by mass.

In addition to the above-mentioned structural units, the acrylic resin may contain structural units derived from other monomers copolymerizable with the acrylic monomer.
The structural units derived from other monomers contained in the acrylic resin may be one type alone or two or more types.
Examples of other monomers include styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, and acrylamide.

The acrylic resin may also have an unsaturated group polymerizable with energy rays introduced therein in order to impart energy ray curability to the acrylic resin.
The unsaturated group is, for example, a functional group of an acrylic resin containing a structural unit derived from a functional group-containing monomer, a reactive substituent that is reactive with the functional group, and a compound having an unsaturated group (hereinafter referred to as " It can be introduced by reacting with a reactive substituent of an unsaturated group-containing compound). One type of unsaturated group-containing compound may be used alone, or two or more types may be used in combination.
Examples of the unsaturated group contained in the unsaturated group-containing compound include a (meth)acryloyl group, a vinyl group, and an allyl group. Among these, a (meth)acryloyl group is preferred.
Examples of the reactive substituent that the unsaturated group-containing compound has include an isocyanate group and a glycidyl group.
Examples of the unsaturated group-containing compound include (meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, glycidyl (meth)acrylate, and the like.

When reacting an acrylic resin containing structural units derived from a functional group-containing monomer with an unsaturated group-containing compound, among the total number of functional groups in the acrylic resin, the functional group that reacts with the unsaturated group-containing compound Although the ratio is not particularly limited, it is preferably 60 to 98 mol%, more preferably 70 to 95 mol%, and even more preferably 80 to 93 mol%.
When the ratio of the functional groups that react with the unsaturated group-containing compound is within the above range, sufficient energy ray curability can be imparted to the acrylic resin, and functional groups that do not react with the unsaturated group-containing compound can be crosslinked. The acrylic resin can be crosslinked by reacting with the agent.

The weight average molecular weight (Mw) of the acrylic resin is not particularly limited, but is preferably 300,000 to 1,500,000, more preferably 350,000 to 1,000,000, and still more preferably 400,000 to 600,000.
When the weight average molecular weight (Mw) of the acrylic resin is within the above range, the adhesive force and cohesive force of the adhesive layer tend to be better.

(Energy ray curable compound)
The energy ray-curable compound contained in the X-type or XY-type pressure-sensitive adhesive composition is preferably a monomer or oligomer that has an unsaturated group in its molecule and is curable by energy ray irradiation.
Examples of energy ray-curable compounds include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, 1, Polyvalent (meth)acrylate monomers such as 6-hexanediol di(meth)acrylate; oligomers such as urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and epoxy (meth)acrylate; etc. It will be done. Among these, urethane (meth)acrylate oligomers are preferred because they have a relatively high molecular weight and are difficult to reduce the elastic modulus of the adhesive layer.

The molecular weight of the energy ray curable compound is not particularly limited, but is preferably 100 to 12,000, more preferably 200 to 10,000, even more preferably 400 to 8,000, even more preferably 600 to 6,000. be. In addition, when the energy ray curable compound is an oligomer, the above molecular weight means a mass average molecular weight (Mw).

The content of the energy ray-curable compound in the X-type adhesive composition is not particularly limited, but is preferably 40 to 200 parts by mass, more preferably 50 to 150 parts by mass, based on 100 parts by mass of the adhesive resin. , more preferably 60 to 90 parts by mass.
When the content of the energy ray-curable compound in the X-type adhesive composition is within the above range, the balance between adhesive strength before energy ray irradiation and releasability after energy ray irradiation tends to be good.

The content of the energy ray-curable compound in the XY-type adhesive composition is not particularly limited, but is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, based on 100 parts by mass of the adhesive resin. , more preferably 3 to 15 parts by mass.
When the content of the energy ray-curable compound in the XY-type adhesive composition is within the above range, the balance between adhesive strength before energy ray irradiation and releasability after energy ray irradiation tends to be good. In addition, since the adhesive resin of the XY type adhesive composition is energy ray curable, it tends to be able to sufficiently reduce the peeling force after energy ray irradiation even if the content of the energy ray curable compound is small. It is in.

(Crosslinking agent)
It is preferable that the adhesive composition further contains a crosslinking agent.
The crosslinking agent crosslinks the adhesive resins by, for example, reacting with a functional group derived from a functional group-containing monomer included in the adhesive resin.
One type of crosslinking agent may be used alone, or two or more types may be used in combination.

Examples of the crosslinking agent include isocyanate crosslinking agents such as tolylene diisocyanate, hexamethylene diisocyanate, and adducts thereof; epoxy crosslinking agents such as ethylene glycol glycidyl ether; hexa[1-(2-methyl)-aziridinyl]triphosate; Examples include aziridine crosslinking agents such as sphatriazine; chelate crosslinking agents such as aluminum chelate; and the like. Among these, isocyanate-based crosslinking agents are preferred from the viewpoint of increasing cohesive force to further improve adhesive strength and from the viewpoint of easy availability.

When the adhesive composition contains a crosslinking agent, the content thereof is not particularly limited, but from the viewpoint of allowing the crosslinking reaction to proceed appropriately, it is preferably 0.01 to 10 parts by mass based on 100 parts by mass of the adhesive resin. Parts by weight, more preferably 0.03 to 7 parts by weight, still more preferably 0.05 to 4 parts by weight.

(Photopolymerization initiator)
When the adhesive is an energy ray-curable adhesive, the adhesive composition preferably further contains a photopolymerization initiator. When the energy ray curable adhesive contains a photopolymerization initiator, the curing reaction of the energy ray curable adhesive tends to proceed sufficiently even with relatively low energy energy rays such as ultraviolet rays.
One type of photopolymerization initiator may be used alone, or two or more types may be used in combination.

Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones, and more. Specifically, for example, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzylphenyl sulfide, Examples include tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and the like.

When the adhesive composition contains a photopolymerization initiator, the content is not particularly limited, but from the viewpoint of homogeneously and sufficiently proceeding the energy ray curing reaction, it is preferably based on 100 parts by mass of the adhesive resin. is 0.01 to 10 parts by weight, more preferably 0.03 to 7 parts by weight, even more preferably 0.05 to 5 parts by weight.

(Other additives)
The adhesive composition may contain other additives within a range that does not impair the effects of the present invention. Examples of other additives include antistatic agents, antioxidants, softeners, fillers, rust preventives, pigments, and dyes.

(organic solvent)
The pressure-sensitive adhesive composition may be diluted with an organic solvent to form a solution in order to further improve the applicability to substrates, release sheets, etc.
Examples of the organic solvent include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol.
One type of organic solvent may be used alone, or two or more types may be used in combination.
As the organic solvent, the organic solvent used during the synthesis of the adhesive resin may be used as it is, or one or more organic solvents other than the organic solvent used during the synthesis may be added.

The storage modulus G' at 23° C. of the adhesive layer is not particularly limited, but is preferably 0.05 to 0.5 MPa, more preferably 0.1 to 0.4 MPa, and even more preferably 0.12 to 0.3 MPa. It is.
When the storage modulus G' at 23°C of the adhesive layer is within the above range, even if the surface of the workpiece is uneven, an adhesive layer that has excellent followability to the uneven shape can be obtained, and the surface of the workpiece can be easily adjusted during processing. They tend to provide better protection.
Note that the storage elastic modulus G' of the adhesive layer means the storage elastic modulus G' before curing by energy ray irradiation when the adhesive layer is formed from an energy ray curable adhesive.
The storage modulus G' of the adhesive layer at 23° C. was determined by using a test piece obtained by cutting a 3 mm thick adhesive layer into a circular shape with a diameter of 8 mm, using a torsional shear method using a viscoelasticity measuring device at a frequency of 1 Hz, The measurement can be performed at a measurement temperature of 23°C.

The thickness of the adhesive layer is not particularly limited, but is preferably 5 to 100 μm, more preferably 10 to 80 μm, and still more preferably 15 to 60 μm.
When the thickness of the adhesive layer is at least the above lower limit, excellent adhesiveness is obtained and the surface of the workpiece tends to be better protected during processing. Furthermore, when the thickness of the adhesive layer is less than or equal to the above upper limit value, generation of tape waste when cutting the adhesive sheet is suppressed, and damage to the workpiece tends to be better prevented.

<Base material>
Examples of the base material include various resin films. Examples of the resin constituting the resin film include polyethylene such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE); polypropylene, polybutene, polybutadiene, polymethylpentene, and ethylene-norbornene. Polyolefins such as copolymers and norbornene resins; ethylene copolymers such as ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid copolymers, and ethylene-(meth)acrylic acid ester copolymers; polychlorination Vinyl, polyvinyl chloride such as vinyl chloride copolymer; polyester such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, fully aromatic polyester; polyurethane, polyimide, polyamide, polycarbonate, fluororesin, polyacetal, modified polyphenylene oxide, polyphenylene Examples include sulfide, polysulfone, polyetherketone, acrylic polymer, and the like.
The base material may be a single-layer resin film made of one or more resins selected from these resins, or may be a laminated film made by laminating two or more of these resin films. . It may also be a modified film such as a crosslinked film of the above resin or an ionomer film.
Among these resin films, the base material is preferably one or more selected from polyester films, polyamide films, polyimide films, and biaxially oriented polypropylene films, more preferably polyester films, and even more preferably polyethylene terephthalate films.

The Young's modulus of the base material is not particularly limited, but is preferably 1,000 MPa or more, more preferably 1,800 to 30,000 MPa, and still more preferably 2,500 to 6,000 MPa.
When the Young's modulus of the base material is equal to or higher than the above lower limit, the vibration suppressing effect during workpiece processing tends to be further improved. Moreover, when the Young's modulus of the base material is less than or equal to the above upper limit value, the workability when attaching to a workpiece and the workability when peeling from a workpiece tend to be good.
The Young's modulus of the base material can be measured at a test speed of 200 mm/min in accordance with JIS K 7127:1999.

The thickness of the base material is not particularly limited, but is preferably 10 to 200 μm, more preferably 25 to 100 μm, and still more preferably 30 to 70 μm.
When the thickness of the base material is equal to or greater than the above lower limit, sufficient strength to function as a support for the pressure-sensitive adhesive sheet tends to be obtained. Moreover, when the thickness of the base material is equal to or less than the above upper limit value, appropriate flexibility is obtained and handling properties tend to be improved.
In addition, "thickness of the base material" means the thickness of the entire base material, and if the base material consists of multiple layers, the total thickness of all the layers that make up the base material. means.

The base material may contain a plasticizer, a lubricant, an infrared absorber, an ultraviolet absorber, a filler, a colorant, an antistatic agent, an antioxidant, a catalyst, etc., within a range that does not impair the effects of the present invention.
The base material may be transparent or opaque, and may be colored or vapor-deposited as desired.
The base material may be surface-treated, such as corona treatment, on at least one side of the base material in order to improve adhesion with other layers, and may be coated with a coating intended to improve adhesion. It may be provided with layers.

<Release sheet>
In the pressure-sensitive adhesive sheet of this embodiment, a release sheet may be attached to at least one of the surface of the pressure-sensitive adhesive layer and the surface of the surface coating layer. The release sheet protects the surface of the adhesive sheet by being releasably attached to the surface of the adhesive sheet before use, and is peeled off and removed when the adhesive sheet is used.
The release sheet may be a release sheet that has been subjected to a release treatment on one side, or may be a release sheet that has been subjected to a release treatment on both sides.
As the release sheet, a release sheet in which a release agent is applied to a release sheet base material is preferably mentioned.
The base material for the release sheet is preferably a resin film, and examples of the resin film include polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film; polyolefin films such as polypropylene film and polyethylene film; can be mentioned.
Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins; long chain alkyl resins, alkyd resins, and fluororesins.
The thickness of the release sheet is not particularly limited, but is preferably 5 to 200 μm, more preferably 10 to 100 μm, and still more preferably 20 to 50 μm.

<Total thickness of adhesive sheet>
The total thickness of the adhesive sheet of this embodiment is not particularly limited, but is preferably 30 to 300 μm, more preferably 40 to 220 μm, and even more preferably 45 to 160 μm.
When the total thickness of the adhesive sheet is at least the above lower limit, the adhesive performance of the adhesive layer, the shock absorption performance of the buffer layer, etc. are maintained appropriately, and the adhesive sheet tends to be able to fully demonstrate its function as a semiconductor processing adhesive sheet. . Moreover, when the total thickness of the adhesive sheet is less than or equal to the above upper limit value, the peeling force when peeling the workpiece from the adhesive sheet tends to be small.
In this embodiment, the "total thickness of the adhesive sheet" means the thickness from the surface of the surface coating layer of the adhesive sheet to the surface of the adhesive layer, and when a release sheet is provided, the thickness of the release sheet The thickness is not included in the total thickness.

<Method for manufacturing adhesive sheet>
There are no particular restrictions on the method for manufacturing the adhesive sheet of this embodiment, and the adhesive sheet can be manufactured by any known method.
The adhesive sheet of this embodiment includes, for example, a process of forming an adhesive layer on one side of the base material (hereinafter also referred to as "adhesive layer forming process"), and a buffer layer on the other side of the base material. A method comprising a step of forming a surface coat layer on the opposite side of the buffer layer from the base material (hereinafter also referred to as a "surface coat layer forming step"). It can be manufactured by Note that the order of these steps is not particularly limited, and if they can be performed at the same time, they may be performed at the same time.

As a method for forming an adhesive layer, a buffer layer, or a surface coat layer, for example, an adhesive composition, a composition for forming a buffer layer, or a composition for forming a surface coat layer is applied to a predetermined position by a known method. After that, a method of performing energy ray irradiation, heat drying, etc. as necessary may be mentioned.

Examples of methods for applying the adhesive composition, buffer layer forming composition, or surface coat layer forming composition include spin coating, spray coating, bar coating, knife coating, roll coating, and blade coating. method, die coating method, gravure coating method, etc.

The adhesive layer forming step may be, for example, a method of bonding an adhesive layer formed on a release sheet to the surface of a base material, and the adhesive layer is formed by directly applying an adhesive composition to the surface of the base material. A method of forming an agent layer may also be used.
In the buffer layer forming step, the buffer layer forming composition may be applied onto a release sheet or directly onto the surface of the base material. When applying the composition for forming a buffer layer onto a release sheet, the layer formed from the composition for forming a buffer layer on the release sheet (hereinafter also referred to as "composition layer for forming a buffer layer") is then coated with a base layer. It is attached to the surface of the material. The buffer layer-forming composition layer on the release sheet may be the buffer layer itself, or if the buffer layer-forming composition is curable, it may be a layer of the buffer layer-forming composition that is curable. It may be an uncured product or a semi-cured product. When an uncured or semi-cured product of the composition for forming a buffer layer is formed on the base material, a treatment is then performed to completely cure the composition for forming a buffer layer.
In the surface coat layer forming step, the surface coat layer forming composition may be applied onto a release sheet or directly onto the surface of the buffer layer. When applying the composition for forming a surface coat layer on a release sheet, the layer formed from the composition for forming a surface coat layer on the release sheet (hereinafter also referred to as "composition layer for forming a surface coat layer") is It is then applied to the surface of the buffer layer. The surface coat layer forming composition layer on the release sheet may be the surface coat layer itself, or if the surface coat layer forming composition is curable, it may be used to form a curable surface coat layer. It may be an uncured product or a semi-cured product of the composition for use. When an uncured or semi-cured product of the composition for forming a surface coat layer is formed on the buffer layer, the composition for forming a surface coat layer is then subjected to a treatment for completely curing.
Further, the buffer layer forming step and the surface coat layer forming step may be a method in which a surface coat layer and a buffer layer are provided on a release sheet in this order, and then the buffer layer is bonded to the surface of the base material.

When the buffer layer forming composition contains an energy ray polymerizable compound, the buffer layer forming step preferably includes a step of irradiating the buffer layer forming composition with energy rays.
When the composition for forming a buffer layer contains an energy ray polymerizable compound, the curing treatment by energy ray irradiation may be performed once or in multiple steps.
When curing treatment by energy ray irradiation is performed in one time, after forming a coating film of the buffer layer forming composition on the base material, the buffer layer forming composition may be completely cured by energy ray irradiation, After the composition for forming a buffer layer is completely cured on a release sheet, it may be bonded to a base material.
When the composition for forming a surface coat layer contains an energy ray polymerizable compound, the surface coat layer forming step preferably includes a step of irradiating the composition for forming a surface coat layer with energy rays. The timing of irradiating the surface coat layer forming composition with energy rays is not particularly limited, and may be before or after laminating the surface coat layer forming composition on the buffer layer or the buffer layer forming composition layer. It may be either.
When curing the buffer layer-forming composition in multiple steps, after forming a coating film of the buffer layer-forming composition on the release sheet, the buffer layer-forming composition is not completely cured on the release sheet. Without curing, the composition for forming a buffer layer is cured to a semi-cured state and then bonded to the composition layer for forming a surface coat layer provided on a release sheet, and then irradiated with energy rays again to completely cure the composition for forming a buffer layer. It may be hardened. When the composition for forming a surface coat layer contains an energy ray polymerizable compound, the composition for forming a surface coat layer may be simultaneously cured by energy ray irradiation to completely cure the composition for forming a buffer layer. good.
In addition, ultraviolet rays are preferable as the energy rays irradiated in the curing treatment of the composition for forming a buffer layer and the composition for forming a surface coat layer.
When the composition for forming a buffer layer and the composition for forming a surface coat layer are cured by irradiating energy rays, the composition for forming a buffer layer and the composition for forming a surface coat layer are exposed to the outside. However, it is preferable to irradiate the energy beam with both sides covered with members such as release sheets and base materials and not exposed to the outside.

<Applications of adhesive sheet>
Workpiece processing performed with the adhesive sheet of this embodiment attached includes, for example, back-grinding processing in which one surface of a semiconductor device is ground with an adhesive sheet attached to the other surface, and Examples include dicing, which separates a semiconductor device into individual pieces with an adhesive sheet attached to the surface, transportation of the semiconductor device, and pickup of the semiconductor chip. Among these, the adhesive sheet of this embodiment is suitable for backgrinding, and is more suitable for backgrinding in which the backside of a semiconductor wafer is ground with the adhesive sheet of this embodiment affixed to the circuit-forming surface of the semiconductor wafer. be. In particular, the adhesive sheet of this embodiment has the effect of suppressing the occurrence of cracks when thinning a semiconductor wafer, and is therefore suitable for processes such as the first dicing method and the stealth first dicing method.

[Method for manufacturing semiconductor device]
The method for manufacturing a semiconductor device of this embodiment is as follows:
A step of attaching the adhesive sheet for semiconductor processing of the present embodiment to the surface of a semiconductor wafer using the adhesive layer as an attachment surface;
Grinding the back surface of the semiconductor wafer while the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer is fixed by a support device;
A method of manufacturing a semiconductor device, including:

Further, the method for manufacturing a semiconductor device of this embodiment includes:
A dividing line forming step, which is step a of forming a groove on the surface of the semiconductor wafer, or step b of forming a modified region inside the semiconductor wafer from the front or back surface of the semiconductor wafer;
After the step a, or before or after the step b, a sheet pasting step of pasting the adhesive sheet for semiconductor processing of the present embodiment on the surface of the semiconductor wafer with the adhesive layer as the pasting surface;
With the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer fixed by a support device, the back surface of the semiconductor wafer is ground to form a plurality of semiconductors starting from the groove or the modified region. A grinding and singulation process for singulating into chips;
Preferably, the method includes the steps of manufacturing a semiconductor device.
Furthermore, the method for manufacturing a semiconductor device of this embodiment may include a peeling step of peeling the adhesive sheet for semiconductor processing of this embodiment from a plurality of semiconductor chips after the grinding and singulation steps.
Note that the method for manufacturing a semiconductor device having the above step a is a process equivalent to a first dicing method, and the method for manufacturing a semiconductor device having the above step b is a process corresponding to a stealth first dicing method.

Examples of semiconductor wafers used in the manufacturing method of this embodiment include silicon wafers, gallium arsenide wafers, gallium nitride wafers, silicon carbide wafers, glass wafers, and sapphire wafers. Among these, silicon wafers are preferred.
Circuits such as wiring, capacitors, diodes, and transistors are usually formed on the surface of a semiconductor wafer. These circuits can be formed by conventionally known methods such as etching and lift-off methods.
The thickness of a semiconductor wafer before grinding is not particularly limited, but is usually 500 to 1,000 μm.
Each step of the method for manufacturing a semiconductor device of this embodiment will be described in detail below.

<Scheduled division line formation process>
The dividing line forming step is step a of forming grooves on the surface of the semiconductor wafer, or step b of forming modified regions inside the semiconductor wafer from the front or back surface of the semiconductor wafer.

Step a is a step of forming grooves on the surface of the semiconductor wafer, and is performed before attaching the adhesive sheet to the surface of the semiconductor wafer.
The groove formed in the surface of the semiconductor wafer in step a is a groove whose depth is shallower than the thickness of the semiconductor wafer. After step a, the back surface of the semiconductor wafer is ground down to the grooves formed in step a, and the semiconductor wafer is divided into a plurality of semiconductor chips. Therefore, in step a, the grooves are formed along the dividing line when the semiconductor wafer is divided into individual semiconductor chips.
The grooves can be formed by dicing using a conventionally known wafer dicing device or the like.

Step b is a step of forming a modified region inside the semiconductor wafer from the front or back surface of the semiconductor wafer, and may be performed before or after attaching the adhesive sheet to the front surface of the semiconductor wafer.
In step b, a modified region is formed inside the semiconductor wafer by laser irradiation focused on the inside of the semiconductor wafer. The modified region is a part of the semiconductor wafer that has become brittle, and is destroyed when the semiconductor wafer becomes thinner due to back grinding or when force is applied due to grinding, and the semiconductor wafer is broken into individual semiconductor chips. This is the starting point for the transformation. Therefore, the modified region is formed along the dividing line when the semiconductor wafer is divided into individual semiconductor chips.
Laser irradiation may be performed from the front side of the semiconductor wafer or from the back side. When step b is performed after the sheet pasting step, the semiconductor wafer may be irradiated with a laser through the adhesive sheet.

<Sheet pasting process>
The sheet attaching step is a step of attaching an adhesive sheet to the surface of a semiconductor wafer, using the adhesive layer as an attachment surface, after step a, or before or after step b.
The method of applying the adhesive sheet is not particularly limited, and for example, a conventionally known method using a laminator or the like can be applied.

<Grinding and singulation process>
In the grinding and singulation process, the back side of the semiconductor wafer is ground with the surface coating layer side of the adhesive sheet attached to the semiconductor wafer fixed by a support device, and a plurality of pieces are formed starting from the groove or the modified area. This is the process of singulating into semiconductor chips.
The semiconductor wafer to which the adhesive sheet is attached and in which grooves or modified regions are formed is fixed on the surface coat layer side of the adhesive sheet by a support device. The support device is not particularly limited, but a device that suctions and holds an object to be fixed, such as a chuck table, is preferable.

Next, the back surface of the fixed semiconductor wafer is ground to separate the semiconductor wafer into a plurality of semiconductor chips.
In back grinding, when grooves are formed in the semiconductor wafer in step a, the semiconductor wafer is ground to at least a position where the ground surface reaches the bottom of the groove. By this back grinding, the groove becomes a cut that passes through the wafer, and the semiconductor wafer is divided into individual semiconductor chips by the cut.
On the other hand, if a modified region is formed on the semiconductor wafer in step b, the ground surface may reach the modified region, but does not need to strictly reach the modified region. That is, it is sufficient to grind to a position close to the modified region so that the semiconductor wafer is broken starting from the modified region and separated into semiconductor chips. For example, after grinding a semiconductor wafer to a position close to the modified region without singulating it, a pick-up tape may be attached to the semiconductor wafer and the pick-up tape may be stretched to separate the semiconductor chips into pieces. good.

The shape of the diced semiconductor chip may be square, or may be elongated such as a rectangle.
The thickness of the diced semiconductor chip is not particularly limited, but is preferably 5 to 100 μm, more preferably 7 to 70 μm, and still more preferably 10 to 45 μm.
The chip size of the diced semiconductor chip is not particularly limited, but is preferably less than 50 mm ² , more preferably less than 30 mm ² , and even more preferably less than 10 mm ² .

<Peeling process>
The peeling process is a process of peeling the adhesive sheet from the plurality of semiconductor chips after the grinding and singulation process.
When the adhesive layer of the adhesive sheet is formed from an energy ray-curable adhesive, the adhesive is cured by irradiation with energy rays to reduce the peeling force of the adhesive layer, and then the adhesive sheet is Peel off.
Note that a pick-up tape may be used when peeling off the adhesive sheet. A pickup tape is, for example, composed of a base material and an adhesive sheet including an adhesive layer provided on one surface of the base material.
When using a pick-up tape, first, the pick-up tape is attached to the back side of a semiconductor wafer that has been diced, and the position and orientation are adjusted so that it can be picked up. At this time, it is preferable that the ring frame disposed on the outer peripheral side of the semiconductor wafer is also attached to the pickup tape, and the outer peripheral edge of the pickup tape is fixed to the ring frame. Next, the adhesive sheet is peeled off from the plurality of semiconductor chips fixed on the pickup tape.
Thereafter, a semiconductor device may be manufactured by picking up a plurality of semiconductor chips on the pick-up tape and fixing them on a substrate or the like.

Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to these Examples. The methods for measuring and evaluating various physical properties are as follows.

[Mass average molecular weight (Mw)]
The mass average molecular weight (Mw) was measured using a gel permeation chromatography device (manufactured by Tosoh Corporation, product name "HLC-8220") under the following conditions, and was calculated in terms of standard polystyrene.
(Measurement condition)
・Column: "TSK guard column HXL-H""TSK gel GMHXL (x2)""TSK gel G2000HXL" (all manufactured by Tosoh Corporation)
・Column temperature: 40℃
・Developing solvent: Tetrahydrofuran ・Flow rate: 1.0 mL/min

[Thickness measurement of adhesive sheets, etc.]
The total thickness of the adhesive sheet, the thickness of each layer, and the thickness of a test piece prepared from these were measured using a constant pressure thickness measuring device (manufactured by Techlock Co., Ltd., trade name "PG-02"). At this time, measurements were taken at 10 arbitrary points, and the average value was calculated.
Note that the total thickness of the adhesive sheet is the value obtained by measuring the thickness of the adhesive sheet with a release sheet and subtracting the thickness of the release sheet from the measured thickness.
Moreover, the thickness of the buffer layer is the value obtained by subtracting the thickness of the base material from the thickness of the base material with the buffer layer.
Further, the thickness of the surface coat layer is the value obtained by subtracting the thickness of the release sheet from the thickness of the surface coat layer with a release sheet.
The thickness of the adhesive layer is the value obtained by subtracting the thicknesses of the surface coat layer, buffer layer, and base material from the total thickness of the adhesive sheet.

[Measurement of 1-bromonaphthalene contact angle of surface coating layer]
The 1-bromonaphthalene contact angle of the surface coating layer was measured in accordance with JIS R 3257:1999. Specifically, the static contact angle when the release sheet on the surface coat layer side of the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples was peeled off and 1-bromonaphthalene was dropped onto the surface of the exposed surface coat layer was determined as follows: Measurement was performed using a fully automatic contact angle measuring meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DM-701") under the following conditions.
・Measurement temperature: 23℃
・Droplet volume: 2μl
・Measurement time: 1 second after dropping ・Image analysis method: θ/2 method

[Evaluation of the amount of grinding debris attached to the surface coat layer]
The pressure-sensitive adhesive sheets having release sheets on both sides produced in Examples and Comparative Examples were cut out into a size of 5 cm square in plan view, and the release sheet on the surface coat layer side was peeled off to expose the surface coat layer to obtain a test piece. Got ready. An arbitrary one of the four corners of the test piece was fixed and hung, and the test piece was immersed in grinding water containing 2% by mass of silicon wafer grinding waste for 10 minutes. The test piece was taken out from the grinding water, left hanging at 23°C for 24 hours to dry, and then the surface coating layer of the test piece was visually observed and the amount of grinding debris adhering was evaluated based on the following criteria. . In addition, in the following evaluation criteria, "grinding debris adhesion part" means an island-like grinding debris adhesion location formed by drying droplets of grinding water that adhered to the surface coat layer.
A: There is one part on the surface coat layer where grinding debris is attached, or there is no amount of grinding debris attached to the surface to the extent that it can be identified as a part where grinding debris is attached.
B: There are 2 to 5 places where grinding debris is attached on the surface coat layer.
C: There are 6 or more places on the surface coat layer where grinding debris is attached, but no grinding debris is attached to the entire surface of the surface coat layer.
D: Grinding debris adheres to the entire surface of the surface coat layer.

[Preparation of urethane acrylate oligomer used for buffer layer]
Manufacturing example 1
A terminal isocyanate urethane prepolymer obtained by reacting polyester diol and isophorone diisocyanate was reacted with 2-hydroxyethyl acrylate to obtain a bifunctional urethane acrylate oligomer having a weight average molecular weight (Mw) of 5,000.

[Preparation of energy ray-curable acrylic resin used for adhesive layer]
Manufacturing example 2
An acrylic polymer was obtained by copolymerizing 52 parts by mass of n-butyl acrylate, 20 parts by mass of methyl methacrylate, and 28 parts by mass of 2-hydroxyethyl acrylate. Next, 2-methacryloyloxyethyl isocyanate was reacted so as to be added to 90 mol% of the total hydroxyl groups of the acrylic polymer to form an energy ray-curable material having a mass average molecular weight (Mw) of 500,000. Acrylic resin was obtained.

[Manufacture of adhesive sheet]
Examples 1-4, Comparative Examples 1-2
Next, a pressure-sensitive adhesive sheet was manufactured by the method shown below. In addition, the amounts of each component in the following description all mean the amounts of active ingredients.

(1) Preparation of base material A 50 μm thick polyethylene terephthalate film (Young's modulus: 2,500 MPa) was prepared as a base material.

(2) Preparation of a composition for forming a surface coat layer A composition for forming a surface coat layer was prepared by dissolving each component shown in Table 1 in toluene so that the active ingredient concentration was 10% by mass.

(3) Preparation of buffer layer forming composition 40 parts by mass of the urethane acrylate oligomer obtained in Production Example 1, 40 parts by mass of isobornyl acrylate, 20 parts by mass of 2-hydroxy-3-phenoxypropyl acrylate, photopolymerization initiator 2.0 parts by mass of 1-hydroxycyclohexyl phenylketone and 0.2 parts by mass of phthalocyanine pigment were blended to prepare a composition for forming a buffer layer.

(4) Preparation of adhesive composition 100 parts by mass of the energy ray-curable acrylic resin obtained in Production Example 2, polyfunctional urethane acrylate which is an energy ray-curable compound (manufactured by Mitsubishi Chemical Corporation, product name "Shikou UT") -4332'', 6 parts by mass of mass average molecular weight (Mw) 4,700), 0.375 parts by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate L"), and bis( An adhesive composition was prepared by blending 1 part by mass of 2,4,6-trimethylbenzoyl)phenylphosphine oxide and diluting with an organic solvent.

(5) Preparation of adhesive sheet After applying the composition for forming a buffer layer obtained above on one side of the base material shown above so that the thickness of the buffer layer to be formed is 20 μm, The composition for forming a buffer layer is semi-cured by irradiating it with ultraviolet rays under the conditions of 30 mW/cm ² and an irradiation amount of 60 mJ/cm ² , and the composition for forming a buffer layer is semi-cured on one side of the base material. A layer was formed.
In addition, the composition for forming a surface coat layer obtained above was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") until the thickness of the surface coat layer formed was 2 μm. After coating with a Mayer bar, the composition was dried by heating to form a surface coating layer-forming composition layer on the release sheet.
After bonding the surface coating layer forming composition layer on the release sheet and the semi-cured layer of the buffer layer forming composition formed on one side of the base material, an illuminance of 160 mW/cm ² was applied. The composition for forming a buffer layer and the composition for forming a surface coat layer are cured by irradiation with ultraviolet rays at an irradiation amount of 500 mJ/ ^cm2 , and a buffer layer and a surface coat layer are formed on one side of the base material. A laminate having these in this order was obtained.
In addition, the adhesive composition obtained above was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") so that the thickness after drying was 20 μm, and then heated. It was dried to produce a release sheet with an adhesive layer.
By pasting the adhesive layer of the release sheet with an adhesive layer on the surface of the base material of the laminate on which the buffer layer is not provided, a release sheet is provided on both sides, a surface coat layer, a buffer layer, A pressure-sensitive adhesive sheet having a base material and a pressure-sensitive adhesive layer in this order was obtained.

Table 1 shows the evaluation results of the pressure-sensitive adhesive sheets obtained in each Example and Comparative Example.

(resin component)
・S2104: Hydrogenated styrene thermoplastic elastomer (SEPS), styrene content: 65% by mass, manufactured by Kuraray Co., Ltd., product name "Septon (registered trademark) 2104"

(Hydrophobized silica)
・Hydrophobic silica: Amorphous precipitated silica that has been treated to be hydrophobic.

・Untreated silica: Colloidal silica, manufactured by Nissan Chemical Co., Ltd., product name "Snowtex UP"

・Energy ray polymerizable polyfunctional compound: mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate, manufactured by Nippon Kayaku Co., Ltd., product name "KAYARAD DPHA"
・Photopolymerization initiator: 2-hydroxy-2-methyl-1-phenylpropanone, manufactured by IGM Resins B.V., trade name “Omnirad1173”

Table 1 shows that the adhesive sheets of Examples 1 to 4, in which the surface coating layer has a 1-bromonaphthalene contact angle of 19° or more, have sufficiently reduced adhesion of grinding debris. On the other hand, the pressure-sensitive adhesive sheets of Comparative Examples 1 and 2 in which the surface coating layer had a 1-bromonaphthalene contact angle of less than 19° did not sufficiently reduce the amount of attached grinding debris.

Claims (9)

It has a surface coat layer, a buffer layer, a base material and an adhesive layer in this order,
A pressure-sensitive adhesive sheet for semiconductor processing, wherein a static contact angle of 1-bromonaphthalene at 23° C. with respect to the surface coating layer is 19° or more. The pressure-sensitive adhesive sheet for semiconductor processing according to claim 1, wherein the surface coat layer is an organic layer containing a resin component. The pressure-sensitive adhesive sheet for semiconductor processing according to claim 2, wherein the resin component is a polymer of a compound having one or more ethylenically unsaturated bonds. The pressure-sensitive adhesive sheet for semiconductor processing according to claim 3, wherein the compound having one or more ethylenically unsaturated bonds is a styrene compound. The pressure-sensitive adhesive sheet for semiconductor processing according to any one of claims 1 to 4, wherein the surface coat layer has a thickness of 0.05 to 10 μm. The pressure-sensitive adhesive sheet for semiconductor processing according to any one of claims 1 to 4, wherein the buffer layer is a layer formed from a composition for forming a buffer layer containing urethane (meth)acrylate. The adhesive sheet for semiconductor processing according to any one of claims 1 to 4, which is used for backside grinding of semiconductor wafers. A step of attaching the adhesive sheet for semiconductor processing according to any one of claims 1 to 4 to the surface of a semiconductor wafer using the adhesive layer as an attachment surface;
Grinding the back surface of the semiconductor wafer while the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer is fixed by a support device;
A method for manufacturing a semiconductor device, including: A dividing line forming step, which is step a of forming a groove on the surface of the semiconductor wafer, or step b of forming a modified region inside the semiconductor wafer from the front or back surface of the semiconductor wafer;
After the step a, or before or after the step b, the adhesive sheet for semiconductor processing according to any one of claims 1 to 4 is applied to the surface of the semiconductor wafer using the adhesive layer as a pasting surface. A sheet pasting process,
With the surface coating layer side of the adhesive sheet for semiconductor processing attached to the semiconductor wafer fixed by a support device, the back surface of the semiconductor wafer is ground to form a plurality of semiconductors starting from the groove or the modified region. A grinding and singulation process for singulating into chips;
A method for manufacturing a semiconductor device, including: