Adhesive sheet for workpiece processing and method for manufacturing same, and method for manufacturing electronic device

Abstract

Provided are: an adhesive sheet for workpiece processing, the adhesive sheet having a buffer layer, a substrate, and an adhesive layer, wherein the buffer layer contains a cured product of a thermosetting resin composition; and a method for manufacturing an electronic device using said adhesive sheet for workpiece processing.

Description

Adhesive sheet for workpiece processing, manufacturing method thereof, and manufacturing method of electronic device

[0001] The present invention relates to an adhesive sheet for workpiece processing, a method for manufacturing the same, and a method for manufacturing an electronic device.

[0002] As information terminal devices are rapidly becoming thinner, smaller, and more multifunctional, there is a demand for thinner and denser electronic devices, such as semiconductor devices, installed in these devices. A method for thinning electronic devices has been to grind the backside of workpieces, such as semiconductor wafers, used in electronic devices. Backside grinding of a workpiece is performed by attaching an adhesive sheet for workpiece processing (hereinafter also referred to as a "backgrinding sheet") to the surface of the workpiece, protecting the surface of the workpiece. After backside grinding, the backgrinding sheet is peeled off and removed from the surface of the workpiece.

[0003] In recent years, grinding and singulation methods such as the first-edge dicing method and the stealth first-edge dicing method have been put into practical use as grinding and singulation methods for thinning a workpiece while suppressing damage to the workpiece. The first-edge dicing method involves forming grooves of a predetermined depth on the surface of the workpiece using a dicing blade or the like, and then grinding the workpiece from the back side down to the grooves to singulate the workpiece into individual workpieces. The stealth first-edge dicing method involves forming modified regions inside the workpiece by irradiating it with laser light, then grinding the workpiece from the back side and splitting the modified regions as starting points to singulate the workpiece into individual workpieces. These methods also use a back-grinding sheet to protect the surface of the workpiece.

[0004] Adhesive sheets for workpiece processing are required to have good grinding properties that allow them to stably hold a workpiece when processing the workpiece and prevent cracks, etc. Examples of adhesive sheets for workpiece processing include adhesive tapes having a substrate, a buffer layer provided on at least one surface of the substrate, and an adhesive layer provided on the other surface of the substrate, in which the Young's modulus of the buffer layer at 23°C is 10 to 400 MPa and the breaking energy is 1 to 9 MJ / m ３An adhesive tape for semiconductor processing has been proposed in which the Young's modulus at 23° C. of the substrate is greater than the Young's modulus of the buffer layer (see Patent Document 1).

[0005] International Publication No. 2020 / 003920

[0006] In the adhesive tape for semiconductor processing of Patent Document 1, the buffer layer is provided to absorb vibrations that occur when the workpiece is ground and to reduce unevenness caused by foreign matter, thereby holding the workpiece stably and flat.

[0007] However, adhesive sheets for workpiece processing may emit odors due to the components of the adhesive sheets during production, storage, or use. In response to the recent increase in awareness of the working environment, low odor is also required for adhesive sheets for workpiece processing, but it has been difficult to achieve excellent low odor properties while maintaining good grinding properties for workpieces.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an adhesive sheet for work processing that has low odor and excellent grinding properties, a method for manufacturing the same, and a method for manufacturing electronic devices using the adhesive sheet for work processing.

[0009] After extensive research, the present inventors discovered that the above-mentioned problems can be solved by providing a buffer layer containing a cured product of a thermosetting resin composition in an adhesive sheet for workpiece processing, and thus completed the present invention described below.

[0010] That is, the present invention relates to the following items [1] to

[10] . [1] A pressure-sensitive adhesive sheet for workpiece processing, comprising a buffer layer, a substrate, and a pressure-sensitive adhesive layer, wherein the buffer layer is a layer containing a cured product of a thermosetting resin composition. [2] The pressure-sensitive adhesive sheet for workpiece processing according to item [1] above, wherein the thermosetting resin composition contains a polyester-based resin. [3] The pressure-sensitive adhesive sheet for workpiece processing according to item [2] above, wherein the polyester-based resin is a polyester urethane resin. [4] The pressure-sensitive adhesive sheet for workpiece processing according to item [2] or [3] above, wherein the polyester-based resin is a polyester-based resin having two or more hydroxy groups, and the thermosetting resin composition further contains a polyvalent isocyanate compound. [5] The pressure-sensitive adhesive sheet for workpiece processing according to any one of items [1] to [4] above, comprising the buffer layer on one side of the substrate and the pressure-sensitive adhesive layer on the other side of the substrate. [6] The pressure-sensitive adhesive sheet for workpiece processing according to any one of items [1] to [5] above, which is used for grinding a workpiece. [7] The adhesive sheet for workpiece processing according to any one of [1] to [5] above, wherein the workpiece has a groove on its surface or a modified region therein, and the adhesive sheet for workpiece processing is attached to the surface of the workpiece and then ground on the backside of the workpiece, thereby singulating the workpiece into a plurality of individual workpieces starting from the groove or the modified region. [8] A method for producing the adhesive sheet for workpiece processing according to any one of [1] to [7] above, comprising a step of curing the thermosetting resin composition by heating. [9] A method for producing an electronic device, comprising a step of attaching the adhesive sheet for workpiece processing according to any one of [1] to [7] above to the surface of a workpiece, with the adhesive layer as an attachment surface, and a step of grinding on the backside of the workpiece, while the adhesive sheet for workpiece processing attached to the workpiece is fixed.

[10] A method for manufacturing an electronic device, comprising: a division line forming step, which is step a of forming grooves on the surface of a workpiece, or step b of forming modified regions inside the workpiece from the surface or back surface of the workpiece; a sheet attaching step of attaching the adhesive sheet for workpiece processing described in any of [1] to [7] above to the surface of the workpiece, with the adhesive layer serving as an attachment surface, after step a or before or after step b; and a grinding and singulating step of grinding the back surface of the workpiece while the adhesive sheet for workpiece processing is fixed, to singulate the workpiece into a plurality of workpieces starting from the grooves or the modified regions.

[0011] According to the present invention, it is possible to provide an adhesive sheet for workpiece processing that has low odor and excellent abrasive properties, and a method for manufacturing electronic devices using the adhesive sheet for workpiece processing.

[0012] In this specification, the lower and upper limits of preferred numerical ranges described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60."

[0013] In this specification, the term "active ingredient" refers to the components contained in the target composition excluding the diluent solvent.

[0014] In this specification, the number average molecular weight (Mn) and the mass average molecular weight (Mw) are values ​​measured by gel permeation chromatography (GPC) in terms of standard polystyrene, and specifically, are values ​​measured based on the method described in the examples.

[0015] In this specification, for example, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid," and the same applies to other similar terms.

[0016] As used herein, "energy rays" refers to electromagnetic waves or charged particle beams that have an energy quantum, and examples thereof include ultraviolet rays, radioactive rays, and electron beams. Ultraviolet rays can be irradiated using, for example, an electrodeless lamp, a high-pressure mercury lamp, a metal halide lamp, a UV-LED, or the like as an ultraviolet light source. Electron beams can be irradiated using electron beam accelerators or the like. As used herein, "energy ray polymerizable" refers to the property of polymerizing when irradiated with energy rays. Furthermore, "energy ray curable" refers to the property of curing when irradiated with energy rays, and "non-energy ray curable" refers to the property of not having energy ray curability.

[0017] In this specification, the term "workpiece" refers to a plate-shaped body to which the adhesive sheet for workpiece processing of this embodiment is attached and then processed. Examples of workpieces include wafers, panel-level packages, and strips (rectangular substrates) sealed with molded resin. Among these, wafers are preferred from the viewpoint of easily achieving the effects of the present invention. Wafers may be, for example, semiconductor wafers such as silicon wafers, gallium arsenide wafers, silicon carbide wafers, gallium nitride wafers, and indium phosphide wafers, or insulator wafers such as glass wafers, lithium tantalate wafers, and lithium niobate wafers. They may also be reconstructed wafers made of resin and semiconductors used in the manufacture of fan-out packages, etc. Among these, semiconductor wafers and insulator wafers are preferred from the viewpoint of easily achieving the effects of the present invention. Semiconductor wafers typically have circuits such as wiring, capacitors, diodes, and transistors formed on their surfaces. These circuits can be formed by conventional methods such as etching and lift-off. The thickness of the workpiece before processing is not particularly limited, but is typically 500 to 1,000 μm.

[0018] In this specification, the term "single workpiece" refers to a workpiece that has been divided. For example, if the workpiece is a semiconductor wafer, the single workpiece is a semiconductor chip, and if the workpiece is a panel level package or a strip (rectangular substrate) sealed with molded resin, the single workpiece is a semiconductor package.

[0019] In this specification, the term "electronic device" refers to, for example, a workpiece, a workpiece singulation, an electronic component including the workpiece singulation, and electronic equipment including the electronic component.

[0020] In this specification, the "front surface" of a workpiece refers to the surface on which a circuit is formed, and the "back surface" refers to the surface on which no circuit is formed.

[0021] The mechanism of action described in this specification is speculation and does not limit the mechanism by which the adhesive sheet for workpiece processing of the present invention exerts its effects.

[0022] [Adhesive sheet for workpiece processing] The adhesive sheet for workpiece processing of this embodiment (hereinafter also referred to as "adhesive sheet") has a buffer layer, a base material, and an adhesive layer, and the buffer layer is a layer containing a cured product of a thermosetting resin composition.

[0023] The adhesive sheet of this embodiment is attached to the surface of a workpiece and is used to perform a predetermined processing on the workpiece while protecting the surface. After the predetermined processing is performed on the workpiece, the adhesive sheet of this embodiment is peeled off and removed from the workpiece.

[0024] The laminated structure of the pressure-sensitive adhesive sheet of this embodiment is not particularly limited as long as it is a structure that allows the pressure-sensitive adhesive layer to be attached to a workpiece, and may, for example, have a buffer layer on one side of the substrate and a pressure-sensitive adhesive layer on the other side of the substrate, or may have a substrate, buffer layer, and pressure-sensitive adhesive layer in this order. Among these, from the viewpoint of easily obtaining better grinding properties, a structure that has a buffer layer on one side of the substrate and a pressure-sensitive adhesive layer on the other side of the substrate is preferred.

[0025] The pressure-sensitive adhesive sheet of this embodiment may have layers other than the buffer layer, substrate, and pressure-sensitive adhesive layer, or may not have layers other than the buffer layer, substrate, and pressure-sensitive adhesive layer. Examples of layers other than the buffer layer, substrate, and pressure-sensitive adhesive layer include an intermediate layer provided between the substrate and the pressure-sensitive adhesive layer, and a release sheet provided on the surface of the pressure-sensitive adhesive sheet. Each component constituting the pressure-sensitive adhesive sheet of this embodiment will be described below in order.

[0026] <Buffer layer> The adhesive sheet of this embodiment has a buffer layer, which absorbs vibrations, shocks, etc. that occur when processing the workpiece, such as grinding, and can prevent cracks from occurring in the workpiece. Furthermore, by providing a buffer layer, it is possible to absorb unevenness, such as foreign matter, that exists on the table of the support device, thereby improving the holding ability of the adhesive sheet by the support device.

[0027] The buffer layer of the pressure-sensitive adhesive sheet of this embodiment is a layer containing a cured product of a thermosetting resin composition. By using a layer containing a cured product of a thermosetting resin composition as the buffer layer, the pressure-sensitive adhesive sheet of this embodiment has low odor and excellent grinding properties. The reason for this is unclear, but is presumed to be as follows. The raw materials constituting the thermosetting resin composition form a crosslinked structure by heating, and at that time, the raw materials that cause odor are unlikely to remain. Therefore, it is thought that the odor of the buffer layer is suppressed, resulting in excellent low odor properties. Furthermore, it is thought that the good shape retention due to the crosslinked structure of the cured product of the thermosetting resin composition allows the workpiece to be well held during grinding, resulting in excellent grinding properties.

[0028] The buffer layer of the pressure-sensitive adhesive sheet of this embodiment may be any layer containing a cured product of a thermosetting resin composition. From the viewpoints of low odor and grindability, the content of the cured product of the thermosetting resin composition in the buffer layer of the pressure-sensitive adhesive sheet of this embodiment is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, and even more preferably 98 to 100% by mass. The buffer layer of the pressure-sensitive adhesive sheet of this embodiment is preferably a layer of the cured product of the thermosetting resin composition (i.e., the buffer layer of the pressure-sensitive adhesive sheet of this embodiment is preferably composed solely of the cured product of the thermosetting resin composition). The thermosetting resin composition will be described in detail below.

[0029] (Thermosetting resin composition) The thermosetting resin composition is not particularly limited as long as it is a resin composition having thermosetting properties. The thermosetting resin contained in the thermosetting resin composition may be a resin that exhibits thermosetting properties by itself, or may be a resin that exhibits thermosetting properties by being used in combination with one or more selected from the group consisting of a crosslinking agent and a catalyst.

[0030] [Thermosetting resin] Examples of the thermosetting resin include epoxy resin, phenol resin, silicone resin, melamine resin, acrylic resin, polyester resin, etc. Among these, polyester resin is preferred from the viewpoint of low odor and grindability. The thermosetting resin may be used alone or in combination of two or more.

[0031] Examples of polyester resins include polymers obtained by condensation polymerization of alcohol components such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, cyclohexane-1,4-dimethanol, hydrogenated bisphenol A, and ethylene oxide or propylene oxide adducts of bisphenol A, with carboxylic acid components such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, adipic acid, azelaic acid, maleic acid, fumaric acid, itaconic acid, and acid anhydrides thereof. One type of alcohol component and one type of carboxylic acid component may be used alone, or two or more types may be used in combination.

[0032] The polyester-based resin may be a resin obtained by modifying polyester, and from the viewpoints of low odor and grindability, a polyesterurethane resin obtained by urethane-modifying polyester is preferred. In this specification, polyesterurethane resins are included in the concept of polyester-based resins, and suitable aspects of polyester-based resins can be interpreted as suitable aspects of polyesterurethane resins. Examples of polyesterurethane resins include those obtained by reacting a polyisocyanate compound with a polyester polyol having hydroxy groups at its terminals, which is obtained by condensation polymerization of the alcohol component and the carboxylic acid component. The polyisocyanate compound used as a raw material for the polyesterurethane resin may be any of aromatic polyisocyanate compounds, aliphatic polyisocyanate compounds, and alicyclic polyisocyanate compounds. Specific examples of the polyisocyanate compound include diisocyanate compounds such as diphenylmethane diisocyanate, tolylene diisocyanate, 1,3-xylylene diisocyanate, isophorone diisocyanate, and 1,6-hexane diisocyanate. The polyester polyol and the polyvalent isocyanate compound as raw material components of the polyester urethane resin may each be used alone or in combination of two or more kinds.

[0033] The polyester resin has a reactive functional group for thermosetting, and from the viewpoint of improving thermosetting properties, it is preferable that it has two or more hydroxy groups, and more preferable that it has two or more hydroxy groups at the molecular end. Note that the "molecular end" of the polyester resin refers to both ends of the polyester resin when the polyester resin is linear, and also includes the ends of the branched chain when the polyester resin has a branched chain. Among these, the polyester resin is preferably linear and has hydroxy groups at both ends.

[0034] The glass transition temperature (Tg) of the polyester resin is not particularly limited, but is preferably 50 to 140°C, more preferably 60 to 120°C, and even more preferably 70 to 110°C. When the glass transition temperature (Tg) of the polyester resin is equal to or higher than the lower limit, excessive deformation of the buffer layer during processing of the workpiece tends to be suppressed. Furthermore, when the glass transition temperature (Tg) of the polyester resin is equal to or lower than the upper limit, the effect of absorbing vibrations, impacts, etc. that occur during grinding of the workpiece and the retention of the pressure-sensitive adhesive sheet tend to be improved. The glass transition temperature (Tg) of the polyester resin can be measured in accordance with JIS K 7121:2012.

[0035] The number average molecular weight (Mn) of the polyester resin is not particularly limited, but is preferably 5,000 to 100,000, more preferably 10,000 to 70,000, and even more preferably 15,000 to 50,000. When the number average molecular weight (Mn) of the polyester resin is equal to or greater than the lower limit, excessive deformation of the buffer layer during processing of the workpiece tends to be suppressed. Furthermore, when the number average molecular weight (Mn) of the polyester resin is equal to or less than the upper limit, the effect of absorbing vibrations, shocks, etc. that occur during grinding of the workpiece and the retention of the adhesive sheet tend to be improved.

[0036] The hydroxyl value of the polyester-based resin is not particularly limited, but is preferably 0.5 to 30 KOHmg / g, more preferably 1 to 25 KOHmg / g, and even more preferably 2 to 20 KOHmg / g. When the hydroxyl value of the polyester-based resin is equal to or greater than the lower limit, the thermosetting properties are improved, the low odor properties are improved, and excessive deformation of the buffer layer during workpiece processing tends to be suppressed. Furthermore, when the hydroxyl value of the polyester-based resin is equal to or less than the upper limit, the effect of absorbing vibrations, impacts, etc. that occur during workpiece grinding and the retention of the adhesive sheet tend to be improved. The hydroxyl value of the polyester-based resin can be measured in accordance with JIS K 0070:1992.

[0037] When the thermosetting resin composition contains a polyester-based resin, the content of the polyester-based resin in the thermosetting resin composition is not particularly limited, but is preferably 30 to 98% by mass, more preferably 50 to 98% by mass, and even more preferably 70 to 98% by mass, based on the total solid content (100% by mass) of the thermosetting resin composition. When the content of the polyester-based resin is within the above range, low odor and grindability tend to be more favorable. In this specification, the "total solid content of the thermosetting resin composition" refers to the components other than the solvent contained in the thermosetting resin composition, and components other than the solvent are considered to be solids even if they are liquid at room temperature (23°C).

[0038] In addition, as a molding method for polyester-based resins, processing by extrusion molding is commonly performed. However, since extrusion molding requires heating the polyester-based resin to high temperatures, the equipment and energy load is large, making it difficult to achieve good productivity. Furthermore, problems specific to extrusion molding, such as the formation of lumps called fish eyes, can occur, making it difficult to achieve excellent quality stability. In contrast, in the pressure-sensitive adhesive sheet of this embodiment, a polyester-based resin is used as a raw material for the thermosetting resin composition, so a buffer layer of uniform quality can be formed under relatively mild heating conditions. Therefore, the pressure-sensitive adhesive sheet of this embodiment has excellent productivity and excellent quality stability.

[0039] The content of the thermosetting resin in the thermosetting resin composition is not particularly limited, but is preferably 30 to 98 mass%, more preferably 50 to 98 mass%, and even more preferably 70 to 98 mass%, based on the total solid content (100 mass%) of the thermosetting resin composition. When the content of the thermosetting resin is within the above range, low odor and grindability tend to be more favorable.

[0040] [Crosslinking Agent] The thermosetting resin composition may contain a crosslinking agent for crosslinking the thermosetting resin, if necessary. The crosslinking agent may be used alone or in combination of two or more. Known crosslinking agents can be used depending on the type of reactive group possessed by the thermosetting resin to be crosslinked. Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. Among the above crosslinking agents, when the thermosetting resin composition contains a polyester-based resin having two or more hydroxy groups, an isocyanate-based crosslinking agent is preferred from the viewpoint of improving thermosetting properties. The isocyanate-based crosslinking agent is preferably a polyvalent isocyanate compound. Because polyvalent isocyanate compounds are reactive with hydroxy groups, they can bond polyester-based resins having hydroxy groups to form a crosslinked structure. The number of isocyanate groups that the polyvalent isocyanate compound has may be, for example, two, three, or more, depending on the type of thermosetting resin to be crosslinked.

[0041] Examples of polyisocyanate compounds include aromatic isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, 1,3,5-triisocyanate benzene, 1,3,5-triisocyanate methylbenzene, 2,4,6-triisocyanate toluene, and triphenylmethane-4,4',4''-triisocyanate; alicyclic isocyanate compounds such as dicyclohexylmethane-4,4'-diisocyanate, bicycloheptane triisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, and hydrogenated xylylene diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate. The polyvalent isocyanate compound may also be a modified product such as a biuret or isocyanurate of the above-mentioned compounds, or an adduct which is a reaction product of these compounds with a non-aromatic low-molecular-weight active hydrogen-containing compound such as ethylene glycol, trimethylolpropane, castor oil, etc. Among these, an adduct of trimethylolpropane is preferred from the viewpoint of facilitating good reactivity.

[0042] When the thermosetting resin composition contains a polyester resin having two or more hydroxy groups and a polyvalent isocyanate compound, the content of the polyvalent isocyanate compound in the thermosetting resin composition is not particularly limited, but is preferably 1 to 15 parts by mass per 100 parts by mass of the polyester resin having two or more hydroxy groups. When the content of the polyvalent isocyanate compound is within the above range, the PSA sheet tends to have better low odor properties and grindability.

[0043] [Catalyst] The thermosetting resin composition may contain a catalyst for accelerating the thermosetting reaction of the thermosetting resin, as necessary. A single catalyst may be used, or two or more catalysts may be used in combination. Examples of catalysts include organometallic compounds and tertiary amine compounds. Among these, organometallic compounds are preferred from the viewpoint of reactivity. Preferred organometallic compounds are tin-based organometallic compounds, such as dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin bis(2-ethylhexanoate), dibutyltin dineodecanoate, dioctyltin diacetate, dioctyltin dioctoate, dioctyltin dilaurate, dioctyltin bis(2-ethylhexanoate), and dioctyltin dineodecanoate. Among these, dioctyltin dilaurate is preferred from the viewpoint of reactivity. Other organometallic compounds include, for example, metal acylates of bismuth, titanium, zirconium, zinc, iron, etc. (e.g., octylic acid compounds, naphthenic acid compounds, stearic acid compounds, etc.), metal chelates, metal alkoxides, etc. These may be used alone or in combination of two or more.

[0044] When the thermosetting resin composition contains a catalyst, the content of the catalyst in the thermosetting resin composition is not particularly limited, but is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and even more preferably 0.1 to 1 part by mass, relative to 100 parts by mass of the thermosetting resin. When the content of the catalyst is within the above range, the thermosetting reaction can proceed uniformly and sufficiently.

[0045] [Other Components] The thermosetting resin composition may contain other components within the range that does not impair the effects of the present invention. Examples of other components include resin components other than the above-mentioned resins, and other additives such as antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, and dyes.

[0046] (Young's modulus of buffer layer) The Young's modulus of the buffer layer at 23°C is not particularly limited, but is preferably 200 to 4,000 MPa, more preferably 1,000 to 3,500 MPa, and even more preferably 1,500 to 3,200 MPa. When the Young's modulus of the buffer layer at 23°C is equal to or greater than the lower limit, excessive deformation of the buffer layer during workpiece processing tends to be suppressed. Furthermore, when the Young's modulus of the buffer layer at 23°C is equal to or less than the upper limit, the effect of absorbing vibrations, shocks, etc. that occur during workpiece grinding and the retention of the adhesive sheet tend to be improved. The Young's modulus of the buffer layer at 23°C can be measured by the method described in the Examples.

[0047] (Thickness of buffer layer) The thickness of the buffer layer is not particularly limited, but is preferably 2 to 100 μm, more preferably 3 to 60 μm, even more preferably 4 to 40 μm, and even more preferably 5 to 30 μm. If the thickness of the buffer layer is equal to or greater than the above-mentioned lower limit, the effect of absorbing vibrations, shocks, etc. that occur during grinding of the workpiece and the retention of the adhesive sheet tend to be enhanced. Furthermore, if the thickness of the buffer layer is equal to or less than the above-mentioned upper limit, excessive deformation of the buffer layer during processing of the workpiece can be suppressed, and the cost efficiency also tends to be excellent.

[0048] <Adhesive Layer> The adhesive layer is not particularly limited, but is preferably a layer formed from an energy ray-curable adhesive. By forming the adhesive layer from an energy ray-curable adhesive, the adhesive layer can provide sufficient adhesion to protect the workpiece surface well before energy ray curing, and the peel force is reduced after energy ray curing, making it easy to peel from the workpiece.

[0049] Examples of energy ray-curable adhesives include the following X-type adhesive composition, Y-type adhesive composition, and XY-type adhesive composition. 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. Y-type adhesive composition: An energy ray-curable adhesive composition containing an energy ray-curable adhesive resin (hereinafter also referred to as "adhesive resin II") in which an unsaturated group has been introduced into the side chain of a non-energy ray-curable adhesive resin, and containing no energy ray-curable compound other than the adhesive resin. XY-type adhesive composition: An energy ray-curable adhesive composition containing the energy ray-curable adhesive resin II and an energy ray-curable compound other than the adhesive resin. Among these, the energy ray-curable adhesive is preferably an XY-type adhesive composition. Use of an XY-type adhesive composition tends to provide sufficient adhesion before curing while sufficiently reducing the peel force from the workpiece after curing.

[0050] The adhesive forming the adhesive layer may be a layer formed from a non-energy ray-curable adhesive that does not cure 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 or an energy ray-curable compound.

[0051] Next, each component constituting the pressure-sensitive adhesive layer will be described 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 the following description, when simply referring to an "adhesive composition," this concept includes an X-type adhesive composition, a Y-type adhesive composition, an XY-type adhesive composition, and other adhesive compositions.

[0052] Examples of adhesive resins include acrylic resins, urethane resins, rubber resins, silicone resins, etc. Among these, acrylic resins are preferred.

[0053] (Acrylic Resin) The acrylic resin preferably contains a structural unit derived from an alkyl(meth)acrylate. Examples of the alkyl(meth)acrylate include alkyl(meth)acrylates having an alkyl group with 1 to 20 carbon atoms. The alkyl group in the alkyl(meth)acrylate may be linear or branched.

[0054] From the viewpoint of further improving the adhesive strength of the pressure-sensitive adhesive layer, the acrylic resin preferably contains a structural unit derived from an alkyl(meth)acrylate in which the alkyl group has 4 or more carbon atoms. The structural unit derived from an alkyl(meth)acrylate in which the alkyl group has 4 or more carbon atoms contained in the acrylic resin may be one type alone or two or more types. The number of carbon atoms in the alkyl group of the alkyl(meth)acrylate in which the alkyl group has 4 or more carbon atoms is preferably 4 to 12, more preferably 4 to 8, and even more preferably 4 to 6. Examples of alkyl(meth)acrylates in which the alkyl group has 4 or more carbon atoms include butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, nonyl(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 in which the alkyl group has 4 or more carbon atoms, the content thereof in the acrylic resin is preferably 30 to 90 mass%, more preferably 40 to 80 mass%, and even more preferably 45 to 60 mass%, from the viewpoint of further improving the adhesive strength of the pressure-sensitive adhesive layer.

[0055] From the viewpoint of improving the storage modulus G' and adhesive properties of the pressure-sensitive adhesive layer, the acrylic resin preferably contains a structural unit derived from an alkyl(meth)acrylate in which the alkyl group has 1 to 3 carbon atoms, as well as a structural unit derived from an alkyl(meth)acrylate in which the alkyl group has 4 or more carbon atoms. The structural unit derived from an alkyl(meth)acrylate in which the 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)acrylate 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 in the acrylic resin is preferably 1 to 35 mass%, more preferably 5 to 30 mass%, and even more preferably 15 to 25 mass%.

[0056] The acrylic resin preferably further contains a structural unit derived from a functional group-containing monomer. By containing a structural unit derived from a functional group-containing monomer in the acrylic resin, a functional group that serves as a crosslinking origin that reacts with a crosslinking agent, or a functional group that reacts with an unsaturated group-containing compound to introduce an unsaturated group into a side chain of the acrylic resin, can be introduced. The structural unit derived from the functional group-containing monomer contained in the acrylic resin may be of one type alone or two or more types.

[0057] Examples of functional group-containing monomers 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 hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; and the like. Examples of carboxyl group-containing monomers include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids and anhydrides thereof such as fumaric acid, itaconic acid, maleic acid, and citraconic acid; and 2-carboxyethyl methacrylate.

[0058] When the acrylic resin contains a structural unit derived from a functional group-containing monomer, the content thereof is not particularly limited, but is preferably 5 to 45 mass %, more preferably 15 to 40 mass %, and even more preferably 25 to 35 mass % in the acrylic resin.

[0059] In addition to the above 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 of one type alone or two or more types. Examples of other monomers include styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, and acrylamide.

[0060] The acrylic resin may further contain an energy ray-polymerizable unsaturated group to impart energy ray curability. The unsaturated group can be introduced, for example, by reacting a functional group of an acrylic resin containing a structural unit derived from a functional group-containing monomer with a reactive substituent of a compound having a reactive substituent reactive with the functional group and an unsaturated group (hereinafter also referred to as an "unsaturated group-containing compound"). One unsaturated group-containing compound may be used alone, or two or more may be used in combination. Examples of unsaturated groups 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 reactive substituents contained in the unsaturated group-containing compound include an isocyanate group and a glycidyl group. Examples of unsaturated group-containing compounds include (meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, and glycidyl (meth)acrylate.

[0061] When an acrylic resin containing a structural unit derived from a functional group-containing monomer is reacted with an unsaturated group-containing compound, the ratio of functional groups reactive with the unsaturated group-containing compound to the total number of functional groups in the acrylic resin is not particularly limited, but is preferably 60 to 98 mol%, more preferably 70 to 95 mol%, and even more preferably 80 to 93 mol%. When the ratio of functional groups reactive 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 have not reacted with the unsaturated group-containing compound can be reacted with a crosslinking agent to crosslink the acrylic resin.

[0062] The mass 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 even more preferably 400,000 to 600,000. When the mass average molecular weight (Mw) of the acrylic resin is within the above range, the adhesive strength and cohesive strength of the pressure-sensitive adhesive layer tend to be better.

[0063] (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 having an unsaturated group in the molecule and curable by energy ray irradiation. Examples of the energy ray-curable compound include polyvalent (meth)acrylate monomers such as trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate; and oligomers such as urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and epoxy (meth)acrylate. Among these, urethane (meth)acrylate oligomers are preferred from the viewpoints of having a relatively high molecular weight and being less likely to reduce the elastic modulus of the pressure-sensitive adhesive layer.

[0064] 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, and still more preferably 600 to 6,000. When the energy ray-curable compound is an oligomer, the molecular weight refers to the mass average molecular weight (Mw).

[0065] The content of the energy ray-curable compound in the XY-type pressure-sensitive adhesive composition is not particularly limited, but is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, and even more preferably 3 to 15 parts by mass, relative to 100 parts by mass of the pressure-sensitive adhesive resin. When the content of the energy ray-curable compound in the XY-type pressure-sensitive adhesive composition is within the above range, the balance between the adhesive strength before energy ray irradiation and the releasability after energy ray irradiation tends to be good. Note that, because the pressure-sensitive adhesive resin in the XY-type pressure-sensitive adhesive composition is energy ray-curable, even if the content of the energy ray-curable compound is small, the peel strength after energy ray irradiation tends to be sufficiently reduced.

[0066] (Crosslinking Agent) The pressure-sensitive adhesive composition preferably further contains a crosslinking agent. The crosslinking agent crosslinks the pressure-sensitive adhesive resins together by reacting with, for example, a functional group derived from a functional group-containing monomer contained in the pressure-sensitive adhesive resin. One type of crosslinking agent may be used alone, or two or more types may be used in combination.

[0067] Examples of crosslinking agents include isocyanate-based crosslinking agents such as tolylene diisocyanate, hexamethylene diisocyanate, and adducts thereof; epoxy-based crosslinking agents such as ethylene glycol glycidyl ether; aziridine-based crosslinking agents such as hexa[1-(2-methyl)-aziridinyl]triphosphatriazine; and chelate-based crosslinking agents such as aluminum chelate. Among these, isocyanate-based crosslinking agents are preferred from the viewpoints of increasing cohesive strength and further improving adhesive strength, and from the viewpoints of ease of availability.

[0068] When the pressure-sensitive 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, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 4 parts by mass relative to 100 parts by mass of the pressure-sensitive adhesive resin.

[0069] (Photopolymerization initiator) When the pressure-sensitive adhesive is an energy ray-curable pressure-sensitive adhesive, it is preferable that the pressure-sensitive adhesive composition further contains a photopolymerization initiator. When the energy ray-curable pressure-sensitive adhesive contains a photopolymerization initiator, the curing reaction of the energy ray-curable pressure-sensitive 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.

[0070] Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and further photosensitizers such as amines and quinones. More specific examples include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0071] When the pressure-sensitive adhesive composition contains a photopolymerization initiator, the content thereof is not particularly limited, but from the viewpoint of allowing the energy ray curing reaction to proceed uniformly and sufficiently, it is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 5 parts by mass relative to 100 parts by mass of the pressure-sensitive adhesive resin.

[0072] (Other Additives) The pressure-sensitive adhesive composition may contain other additives within the range that does not impair the effects of the present invention. Examples of other additives include antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, dyes, etc.

[0073] (Organic solvent) The pressure-sensitive adhesive composition may be diluted with an organic solvent to form a solution, from the viewpoint of further improving the coatability to a substrate, a release sheet, etc. Examples of the organic solvent include the same organic solvents that may be contained in the thermosetting resin composition described below. As the organic solvent, the organic solvent used in the synthesis of the pressure-sensitive adhesive resin may be used as is, or one or more organic solvents other than the organic solvent used in the synthesis may be added.

[0074] The thickness of the adhesive layer is not particularly limited, but is preferably 5 to 100 μm, more preferably 10 to 80 μm, and even more preferably 15 to 60 μm. When the thickness of the adhesive layer is equal to or greater than the above-mentioned 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 equal to or less than the above-mentioned upper limit, the generation of tape scraps when the adhesive sheet is cut is suppressed, and damage to the workpiece tends to be better prevented.

[0075] <Substrate> Examples of the substrate include various resin films. Examples of resins constituting the resin film include polyethylenes such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE); polyolefins such as polypropylene, polybutene, polybutadiene, polymethylpentene, ethylene-norbornene copolymers, and norbornene resins; ethylene-based copolymers such as ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid copolymers, and ethylene-(meth)acrylic acid ester copolymers; polyvinyl chlorides such as polyvinyl chloride and vinyl chloride copolymers; polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and wholly aromatic polyesters; polyurethanes, polyimides, polyamides, polycarbonates, fluororesins, polyacetals, modified polyphenylene oxides, polyphenylene sulfides, polysulfones, polyether ketones, and acrylic polymers. The substrate may be a single-layer film of a resin film made of one or more resins selected from these resins, or a laminate film in which two or more of these resin films are laminated. The substrate may also be a modified film such as a crosslinked film or an ionomer film of the above resin. Among these resin films, the substrate is preferably one or more selected from polyester film, polyamide film, polyimide film, and biaxially oriented polypropylene film, more preferably polyester film, and even more preferably polyethylene terephthalate film.

[0076] The Young's modulus of the substrate is not particularly limited, but is preferably 1,000 MPa or more, more preferably 1,800 to 30,000 MPa, and even more preferably 2,500 to 6,000 MPa. The Young's modulus of the substrate can be measured in accordance with JIS K 7127:1999 at a test speed of 200 mm / min.

[0077] The thickness of the substrate is not particularly limited, but is preferably 10 to 200 μm, more preferably 25 to 100 μm, and even more preferably 30 to 70 μm. When the thickness of the substrate is equal to or greater than the above lower limit, sufficient strength to function as a support for the PSA sheet tends to be obtained. Furthermore, when the thickness of the substrate is equal to or less than the above upper limit, appropriate flexibility tends to be obtained, and handling tends to be improved. Note that the "thickness of the substrate" refers to the thickness of the entire substrate, and when the substrate is a substrate consisting of multiple layers, it refers to the total thickness of all layers constituting the substrate.

[0078] The substrate 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 substrate may be transparent or opaque, and may be colored or vapor-deposited as desired. From the viewpoint of improving adhesion to other layers, the substrate may be subjected to a surface treatment such as a corona treatment on at least one side, or may have a coating layer formed thereon for the purpose of improving adhesion.

[0079] <Release Sheet> The release sheet is releasably attached to the surface of the pressure-sensitive adhesive sheet before use to protect the surface, and is peeled off and removed when the pressure-sensitive adhesive sheet is used. The release sheet may be a release sheet that has been treated for release on one side, or may be a release sheet that has been treated for release on both sides. Preferred examples of the release sheet include release sheets in which a release agent such as a silicone resin is applied to a release sheet substrate. Examples of the release sheet substrate include the same as those exemplified as the substrate of the pressure-sensitive adhesive sheet of this embodiment.

[0080] <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 equal to or greater than the above-mentioned lower limit, the adhesive performance of the adhesive layer and the shock absorption performance of the buffer layer are appropriately maintained, and the adhesive sheet tends to be able to fully function as an adhesive sheet for workpiece processing. Furthermore, when the total thickness of the adhesive sheet is equal to or less than the above-mentioned upper limit, the peel force when peeling the workpiece from the adhesive sheet tends to be reduced. Note that, when a release sheet is provided on the adhesive sheet of this embodiment, the thickness of the release sheet is not included in the "total thickness of the adhesive sheet."

[0081] <Young's Modulus of Adhesive Sheet> The Young's modulus of the adhesive sheet of the present embodiment at 23°C is not particularly limited, but is preferably 1,200 to 4,200 MPa, more preferably 1,700 to 3,700 MPa, and even more preferably 2,200 to 3,200 MPa. When the Young's modulus of the adhesive sheet at 23°C is equal to or less than the above upper limit, the effect of absorbing vibrations, shocks, etc. that occur during grinding of the workpiece and the retention of the adhesive sheet tend to be improved. Furthermore, when the Young's modulus of the adhesive sheet at 23°C is equal to or greater than the above lower limit, excessive deformation of the adhesive sheet during processing of the workpiece tends to be suppressed. The Young's modulus of the adhesive sheet at 23°C can be measured by the method described in the Examples. When a release sheet is provided on the adhesive sheet of the present embodiment, the "Young's modulus of the adhesive sheet" is measured in a state where the release sheet is peeled off.

[0082] [Method for manufacturing pressure-sensitive adhesive sheet] The method for manufacturing a pressure-sensitive adhesive sheet of the present embodiment includes a step of curing a thermosetting resin composition by heating (hereinafter also referred to as a "thermal curing step"). The thermal curing step can form the buffer layer of the pressure-sensitive adhesive sheet of the present embodiment.

[0083] The thermosetting step is preferably a step of curing a coating film formed by applying a thermosetting resin composition by heating. When applying the thermosetting resin composition, the thermosetting resin composition is preferably in the form of a solution diluted with an organic solvent. Diluting with an organic solvent facilitates the application process and makes it easier to adjust the thickness of the buffer layer, allowing even a thin buffer layer to be formed with excellent thickness precision. Examples of organic solvents include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol. One organic solvent may be used alone, or two or more organic solvents may be used in combination. The content of the organic solvent in the thermosetting resin composition diluted with an organic solvent is not particularly limited, but is preferably 40 to 90% by mass, more preferably 50 to 85% by mass, and even more preferably 60 to 80% by mass.

[0084] The thermosetting resin composition may be applied onto a release sheet or directly onto the surface of the substrate or the pressure-sensitive adhesive layer. Examples of methods for applying the thermosetting resin composition include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0085] The heating temperature for the thermosetting resin composition is preferably 80 to 150°C, more preferably 90 to 140°C, and even more preferably 100 to 130°C, from the viewpoints of productivity of the pressure-sensitive adhesive sheet and sufficient curing of the thermosetting resin composition. The heating time for the thermosetting resin composition is preferably 0.1 to 60 minutes, more preferably 0.3 to 30 minutes, and even more preferably 0.5 to 5 minutes, from the viewpoints of productivity of the pressure-sensitive adhesive sheet and sufficient curing of the thermosetting resin composition. When a release sheet with a buffer layer is obtained by applying a thermosetting resin composition onto a release sheet, the buffer layer of the release sheet with a buffer layer can then be attached to the surface of the substrate or the pressure-sensitive adhesive layer.

[0086] In the method for producing a pressure-sensitive adhesive sheet of this embodiment, the method for forming the pressure-sensitive adhesive layer is not particularly limited, but examples include a method in which the above-mentioned pressure-sensitive adhesive composition is applied and then dried. The pressure-sensitive adhesive composition may be applied onto a release sheet, or may be applied directly to the surface of a substrate or a buffer layer. When the pressure-sensitive adhesive composition is applied onto a release sheet to obtain a release sheet with a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer of the release sheet with a pressure-sensitive adhesive layer may then be attached to the surface of a substrate or a buffer layer. The method for applying the pressure-sensitive adhesive composition is explained in the same manner as the method for applying the thermosetting resin composition described above.

[0087] <Uses of Adhesive Sheet> Examples of workpiece processing performed with the adhesive sheet of this embodiment attached include backgrinding, in which one surface of a workpiece is ground with the other surface attached, dicing, in which a workpiece is divided into individual pieces with an adhesive sheet attached to one surface of the workpiece, workpiece transport, picking up the divided workpieces, etc. Among these, the adhesive sheet of this embodiment is suitable for grinding a workpiece, more suitable for backgrinding, and even more suitable for backgrinding, in which the back surface of a workpiece is ground with the adhesive sheet of this embodiment attached to the circuit-forming surface of the workpiece. In particular, the adhesive sheet of this embodiment has the effect of suppressing the occurrence of cracks when thinning a workpiece, and is therefore suitable for processes such as first dicing and stealth first dicing. Specifically, when a workpiece has a groove on its surface or a modified area inside, and the adhesive sheet for workpiece processing is attached to the surface of the workpiece and fixed, the adhesive sheet is suitable for use in grinding the back surface of the workpiece to separate the workpiece into multiple workpiece pieces starting from the groove or the modified area.

[0088] [Method for manufacturing electronic device] The method for manufacturing an electronic device of this embodiment includes the steps of: attaching the adhesive sheet for workpiece processing of this embodiment to the surface of a workpiece, with the adhesive layer serving as an attachment surface; and grinding the back surface of the workpiece while the adhesive sheet for workpiece processing attached to the workpiece is fixed.

[0089] Furthermore, the manufacturing method for an electronic device according to the present embodiment preferably includes: a division line forming step, which is a step a of forming grooves on the surface of a workpiece, or a step b of forming a modified region inside the workpiece from the surface or back surface of the workpiece; a sheet attaching step of attaching the adhesive sheet for workpiece processing according to the present embodiment to the surface of the workpiece, with the adhesive layer serving as the attachment surface, after the step a, or before or after the step b; and a grinding and singulating step of grinding the back surface of the workpiece while the adhesive sheet for workpiece processing attached to the workpiece is fixed, thereby singulating the workpiece into multiple workpieces starting from the grooves or the modified regions. Furthermore, the manufacturing method for an electronic device according to the present embodiment may also include a peeling step of peeling the adhesive sheet for workpiece processing according to the present embodiment from the multiple workpieces after the grinding and singulating step. The manufacturing method for an electronic device according to the present embodiment, including the above step a, is a process equivalent to a first-edge dicing method, and the manufacturing method for an electronic device according to the above step b, is a process equivalent to a stealth first-edge dicing method. Each step of the method for manufacturing an electronic device according to this embodiment will be described in detail below.

[0090] <Division Line Forming Step> The division line forming step is step a of forming grooves on the surface of the workpiece, or step b of forming modified regions inside the workpiece from the surface or rear surface of the workpiece.

[0091] Process a is a process of forming grooves on the surface of the workpiece, and is performed before the adhesive sheet is attached to the surface of the workpiece. The grooves formed on the surface of the workpiece in process a are shallower than the thickness of the workpiece. After process a, the backside of the workpiece is ground down to the grooves formed in process a, and the workpiece is divided into a plurality of individual workpieces. Therefore, in process a, the grooves are formed along the dividing lines when the workpiece is divided into individual pieces. The grooves can be formed by dicing using a conventionally known wafer dicing device or the like.

[0092] Step b is a step of forming a modified region inside the workpiece from the front or back surface of the workpiece, and may be performed before or after attaching the adhesive sheet to the surface of the workpiece. In step b, the modified region is formed inside the workpiece by irradiating a laser focused on the inside of the workpiece. The modified region is an embrittled part of the workpiece, and is a region that becomes the starting point for dividing the workpiece when the workpiece becomes thinner due to back grinding or when grinding force is applied. Therefore, the modified region is formed along the dividing line when the workpiece is divided and divided into individual pieces. The laser irradiation may be performed from the front side or the back side of the workpiece. If step b is performed after the sheet attaching step, the laser may be irradiated onto the workpiece through the adhesive sheet.

[0093] <Sheet Attachment Step> The sheet attachment step is a step of attaching a pressure-sensitive adhesive sheet to the surface of a workpiece, with the pressure-sensitive adhesive layer serving as the attachment surface, after step a or before or after step b. The method for attaching the pressure-sensitive adhesive sheet is not particularly limited, and a conventionally known method using, for example, a laminator or the like can be applied.

[0094] <Grinding and Singulation Process> The grinding and singulation process is a process in which, while the adhesive sheet for workpiece processing attached to the workpiece is fixed by a support device, the back surface of the workpiece is ground to separate the workpiece into multiple individual workpieces starting from the grooves or modified regions. The workpiece to which the adhesive sheet is attached and which has formed grooves or modified regions is fixed on the adhesive sheet side by the support device. The support device is not particularly limited, but is preferably a device that suctions and holds a fixed object, such as a chuck table.

[0095] Next, the back surface of the fixed workpiece is ground to separate the workpiece into a plurality of workpiece pieces. In the back grinding, if a groove is formed in the workpiece by step a, the workpiece is ground at least to a position where the grinding surface reaches the bottom of the groove. This back grinding turns the groove into a cut that penetrates the workpiece, and the workpiece is divided by the cut and separated into individual workpiece pieces. On the other hand, if a modified region is formed in the workpiece by step b, the grinding surface may reach the modified region, but does not necessarily have to reach the modified region strictly. In other words, it is sufficient to grind to a position close to the modified region so that the workpiece is destroyed and separated starting from the modified region. For example, the workpiece may be ground to a position close to the modified region without being separated, and then a pickup tape may be attached to the workpiece and stretched to separate the workpiece.

[0096] The shape of the individualized workpiece may be square or may be an elongated shape such as a rectangle. The thickness of the individualized workpiece is not particularly limited, but is preferably 5 to 100 μm, more preferably 7 to 70 μm, and even more preferably 10 to 45 μm. The size of the individualized workpiece is not particularly limited, but is preferably 50 mm. ２ less than, more preferably 30 mm ２ less than, more preferably 10 mm ２ is less than.

[0097] <Peeling Process> The peeling process is a process of peeling the adhesive sheet from the multiple workpieces after the grinding and singulation processes. When the adhesive layer of the adhesive sheet is formed from an energy ray-curable adhesive, the adhesive is cured by irradiating it with energy rays, reducing the peel strength of the adhesive layer, and then the adhesive sheet is peeled off. A pickup tape may be used when peeling off the adhesive sheet. The pickup tape may be, for example, composed of a substrate and an adhesive sheet having an adhesive layer provided on one side of the substrate. When using a pickup tape, the pickup tape is first attached to the back side of the individualized workpieces, and the position and orientation are adjusted so that the workpieces can be picked up. At this time, it is preferable to also attach a ring frame arranged on the outer periphery of the workpieces to the pickup tape, and fix the outer edge of the pickup tape to the ring frame. Next, the adhesive sheet is peeled off from the multiple workpieces fixed on the pickup tape. The multiple workpieces on the pickup tape may then be picked up and fixed on a substrate or the like to manufacture an electronic device.

[0098] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following description, the amount of each component refers to the amount of the active ingredient. The methods for measuring and evaluating various physical properties are as follows.

[0099] [Mass-average molecular weight (Mw) and number-average molecular weight (Mn)] The mass-average molecular weight (Mw) and number-average molecular weight (Mn) were measured under the following conditions using a gel permeation chromatograph (manufactured by Tosoh Corporation, trade name "HLC-8220") and calculated in terms of standard polystyrene. (Measurement conditions) Column: "TSK guard column HXL-H", "TSK gel GMHXL (x2)", "TSK gel G2000HXL" (all manufactured by Tosoh Corporation) Column temperature: 40°C Developing solvent: tetrahydrofuran Flow rate: 1.0 mL / min

[0100] [Measurement of thickness of adhesive sheets, etc.] The total thickness of the adhesive sheet, the thickness of each layer, and the thickness of test pieces made from these were measured using a constant pressure thickness gauge (manufactured by Teclock Corporation, product name "PG-02"). Measurements were taken at 10 random points, and the average value was calculated. The total thickness of the adhesive sheet was determined by measuring the thickness of the adhesive sheet with a release sheet and subtracting the thickness of the release sheet from that thickness. The thickness of the buffer layer was determined by subtracting the thickness of the substrate from the thickness of the substrate with a buffer layer. The thickness of the adhesive layer was determined by subtracting the thickness of the buffer layer and the substrate from the total thickness of the adhesive sheet.

[0101] [Method for measuring Young's modulus of buffer layer] A single film containing only the buffer layer, prepared in the same manner as in the Examples and Comparative Examples, was cut into a width of 15 mm and a length of 150 mm, and these were laminated to a thickness of 0.1 mm to obtain a test piece. This test piece was attached to a precision universal testing machine (manufactured by Shimadzu Corporation, product name "Autograph AG-IS") with a chuck distance of 100 mm, and the Young's modulus of the buffer layer was measured at a test speed of 200 mm / min in accordance with JIS K 7127:1999. The measurement was performed in an environment of 23°C and 50% RH.

[0102] [Method for measuring Young's modulus of adhesive sheet] The adhesive sheets for workpiece processing prepared in the Examples and Comparative Examples were cut into a width of 15 mm and a length of 150 mm, and the release sheet was peeled off to obtain a test piece. The test piece was attached to a precision universal testing machine (manufactured by Shimadzu Corporation, product name "Autograph AG-IS") with a chuck distance of 100 mm, and the Young's modulus of the adhesive sheet was measured at a test speed of 200 mm / min in accordance with JIS K 7127:1999. The measurement was carried out in an environment of 23°C and 50% RH.

[0103] [Evaluation of Low Odor] The release sheets were peeled off from the adhesive sheets for workpiece processing produced in the Examples and Comparative Examples, and a sensory evaluation of odor was performed at room temperature (23°C), and the low odor properties of the adhesive sheets were evaluated based on the following criteria: A: No odor C: Odor present

[0104] [Evaluation of Grindability: Backgrinding] The adhesive sheets for workpiece processing produced in the Examples and Comparative Examples were attached to a silicon wafer having a diameter of 12 inches and a thickness of 775 μm using a backgrinding tape laminator (manufactured by Lintec Corporation, product name "RAD3510F / 12") with the adhesive layer facing the attachment surface. Next, using a backgrinding device (manufactured by Disco Corporation, product name "DGP8761"), the silicon wafer was ground (including dry polishing) to a thickness of 30 μm with the adhesive sheet for workpiece processing fixed. The appearance of the silicon wafer after grinding was visually observed, and the grindability in the backgrinding process was evaluated based on the following criteria: A: No damage was observed in the silicon wafer. C: Damage was observed in the silicon wafer.

[0105] [Evaluation of Grindability: Stealth Tip Dicing] The workpiece processing adhesive sheets manufactured in the Examples and Comparative Examples were attached to a silicon wafer with a diameter of 12 inches and a thickness of 775 μm using a backgrinding tape laminator (manufactured by Lintec Corporation, product name "RAD3510F / 12"), with the adhesive layer facing the attachment surface. Subsequently, a laser saw (manufactured by Disco Corporation, product name "DFL7361") was used to form a lattice-shaped modified region inside the silicon wafer. The lattice size was 10 mm x 10 mm. Next, using a backgrinding machine (manufactured by Disco Corporation, product name "DGP8761"), the silicon wafer was ground (including dry polishing) to a thickness of 30 μm, and the silicon wafer was singulated into multiple chips starting from the modified region. The workpiece processing adhesive sheet was then irradiated with energy rays (ultraviolet rays). Next, a dicing tape (manufactured by Lintec Corporation, product name "Adwill D-175D") was attached to the surface of each of the chips opposite to the surface to which the adhesive sheet for workpiece processing was attached, and the adhesive sheet for workpiece processing was peeled off from the chips. The chips after peeling off the adhesive sheet for workpiece processing were observed with a digital microscope and classified according to the following criteria for crack size. The number of chips with confirmed cracks was counted, and the grindability in the stealth tip dicing process was evaluated based on the following criteria. The crack size (μm) was determined by comparing the length (μm) of the crack along the vertical direction of the chip with the length (μm) of the crack along the horizontal direction of the chip, and the larger of these values ​​was used. (Classification of cracks by crack size) Large crack: Crack size greater than 20 μm Medium crack: Crack size from 10 μm to 20 μm Small crack: Crack size less than 10 μm (Evaluation criteria) A: 0 large cracks, 7 or less medium cracks, and 15 or less small cracks B: 0 large cracks, 8 to 10 medium cracks, and 15 or less small cracks, or 0 large cracks, 7 or less medium cracks, and 16 to 20 small cracks C: 1 or more large cracks, or 11 or more medium cracks, or 21 or more small cracks

[0106] [Production of Pressure-Sensitive Adhesive Composition] Production Example 1 An energy ray-curable acrylic copolymer (Mw: 500,000) was obtained by reacting an acrylic polymer obtained by copolymerizing 65 parts by mass of n-butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 15 parts by mass of 2-hydroxyethyl acrylate (2HEA) with 2-methacryloyloxyethyl isocyanate (MOI) so as to be added to 80 equivalents of hydroxyl groups out of all hydroxyl groups (100 equivalents) of the acrylic polymer. 100 parts by mass of this energy ray-curable acrylic copolymer was blended with 6 parts by mass of a multifunctional urethane acrylate ultraviolet-curable compound (manufactured by Mitsubishi Chemical Corporation, trade name "UT-4332"), 0.375 parts by mass of an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., trade name "Takenate D-101E"), and 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as a photopolymerization initiator, and the blend was diluted with methyl ethyl ketone to prepare a pressure-sensitive adhesive composition with a solids concentration of 34% by mass. The pressure-sensitive adhesive composition obtained above was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, trade name "SP-PET381031") to a dry thickness of 20 μm, and then heated and dried to produce a release sheet with a pressure-sensitive adhesive layer.

[0107] [Production of adhesive sheet for workpiece processing] Examples 1 to 7 (1) Preparation of buffer layer-forming composition As a thermosetting resin, 100 parts by mass of the polyester-based resin shown in Table 1, 7.5 parts by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate HL", diluted with ethyl acetate, solid content concentration 74 to 76% by mass), and 0.5 parts by mass of dibutyltin dilaurate (manufactured by Toyochem Co., Ltd., trade name "BXX3778G") as a curing catalyst were blended to prepare a thermosetting resin composition as a buffer layer-forming composition. The details of the polyester-based resin shown in Table 1 are as follows. UR-1400: Polyester urethane resin having two or more hydroxy groups, manufactured by Toyobo Co., Ltd., trade name, glass transition temperature 83°C, number average molecular weight (Mn) 40,000, hydroxyl value 2 to 3 KOH mg / g, diluted with a solvent (containing 50% by mass of methyl ethyl ketone and 50% by mass of toluene), solid content 30% by mass UR-1700: Polyester urethane resin having two or more hydroxy groups, manufactured by Toyobo Co., Ltd., trade name, glass transition temperature 92°C, number average molecular weight (Mn) 16,000, hydroxyl value 19 KOH mg / g, diluted with a solvent (containing 100% by mass of methyl ethyl ketone), solid content 30% by mass UR-4800: Polyester urethane resin having two or more hydroxy groups, manufactured by Toyobo Co., Ltd., trade name, glass transition temperature 106 ° C, number average molecular weight (Mn) 25,000, hydroxyl value 4 to 6 KOH mg / g, solvent (in the solvent, the content of methyl ethyl ketone is 50% by mass, the content of toluene is 50% by mass) diluted product, solid content concentration 32% by mass (2) Preparation of adhesive sheet for workpiece processing A polyethylene terephthalate film (thickness 50 μm) was prepared as a substrate, and the thermosetting resin composition obtained above was applied to one side of the substrate to form a coating film. The amount of the thermosetting resin composition applied was adjusted so that the thickness of the buffer layer formed would be the thickness listed in Table 1. Next, the coating film was heated at 110 ° C for 2 minutes to dry the organic solvent while the thermosetting reaction of the thermosetting resin composition was allowed to proceed, and a buffer layer-attached substrate having a buffer layer having the thickness listed in Table 1 was formed on one side of the substrate.Next, the adhesive layer of the release sheet with adhesive layer obtained in Production Example 1 was bonded to the surface of the substrate with the buffer layer opposite the buffer layer of the substrate, thereby obtaining an adhesive sheet for work processing having a buffer layer, substrate, and adhesive layer in that order.

[0108] Example 8 An adhesive sheet for workpiece processing was obtained in the same manner as in Example 1, except that in "(2) Preparation of adhesive sheet for workpiece processing" in Example 1, the adhesive layer of the release sheet with adhesive layer was attached to the surface of the buffer layer of the substrate with a buffer layer, rather than to the substrate of the substrate with a buffer layer. That is, the adhesive sheet for workpiece processing obtained in Example 8 is an adhesive sheet for workpiece processing having a substrate, a buffer layer, and an adhesive layer in this order.

[0109] Comparative Example 1 (1) Preparation of Buffer Layer-Forming Composition 50 parts by mass of a urethane acrylate oligomer (manufactured by Sartomer, trade name "CN8881") as an energy ray-curable compound, 50 parts by mass of polyethylene glycol (400) diacrylate, and 2.0 parts by mass of 2-hydroxy-2-methyl-1-phenyl-propan-1-one (manufactured by IGM Resins, trade name "Omnirad 1173") as a photopolymerization initiator were blended to prepare an energy ray-curable resin composition as a buffer layer-forming composition. (2) Preparation of Pressure-Sensitive Adhesive Sheet The energy ray-curable resin composition obtained above was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, trade name "SP-PET381031") to form a coating film. Next, the energy ray-curable resin composition was semi-cured by irradiating the coating film with ultraviolet light, forming a 28 μm-thick layer of semi-cured energy ray-curable resin composition on the release sheet. The ultraviolet irradiation was carried out using a belt conveyor type ultraviolet irradiation device (manufactured by iGraphics, product name "ECS-401GX") and a high-pressure mercury lamp (manufactured by iGraphics, product name "H04-L41"), with a lamp height of 260 mm, an output of 80 W / cm, and an illuminance of 70 mW / cm. ２ , irradiation amount 30mW / cm ２The irradiation conditions were as follows. Next, the surface of the layer of semi-cured energy ray-curable resin composition formed on the release sheet was bonded to one side of a PET film (manufactured by Mitsubishi Plastics, Inc., trade name "PET50 T910 WM19", thickness 50 μm) as a substrate. Subsequently, the energy ray-curable resin composition was completely cured by irradiating ultraviolet light from the release sheet side, thereby obtaining a substrate with a buffer layer in which a buffer layer of 28 μm in thickness was formed on one side of the substrate. The ultraviolet irradiation was performed using the above-mentioned ultraviolet irradiation device and high-pressure mercury lamp, with a lamp height of 210 mm, a lamp output of 120 W / cm, and an illuminance of 155 mW / cm. ２ , irradiation amount 600mW / cm ２ Next, the adhesive layer of the release sheet with adhesive layer obtained in Production Example 1 was attached to the surface of the substrate with a buffer layer opposite to the buffer layer, to obtain an adhesive sheet for workpiece processing having a buffer layer, a substrate, and an adhesive layer in this order.

[0110] Comparative Example 2 (1) Preparation of Buffer Layer-Forming Composition A thermosetting resin composition was prepared as a buffer layer-forming composition in the same manner as in Example 1. (2) Preparation of Adhesive Sheet for Workpiece Processing The thermosetting resin composition obtained above was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") to form a coating film. The amount of the thermosetting resin composition applied was adjusted so that the thickness of the buffer layer formed would be the thickness listed in Table 1. The coating film was then heated at 110°C for 2 minutes to dry the organic solvent while allowing the thermosetting reaction of the thermosetting resin composition to proceed, resulting in a release sheet with a buffer layer formed on the release sheet and having a thickness listed in Table 1. The buffer layer of the buffer layer-formed release sheet and the adhesive layer of the adhesive layer-formed release sheet obtained in Production Example 1 were then bonded together to obtain an adhesive sheet for workpiece processing having a buffer layer and an adhesive layer in that order.

[0111] Table 1 shows the evaluation results of the pressure-sensitive adhesive sheets obtained in the examples and comparative examples.

[0112]

[0113] It can be seen from Table 1 that the adhesive sheets for workpiece processing of Examples 1 to 8 of this embodiment have low odor properties and excellent grinding ability. On the other hand, the adhesive sheet for workpiece processing of Comparative Example 1, in which the buffer layer was formed using an energy ray-curable resin composition, was inferior in low odor properties. Furthermore, the adhesive sheet for workpiece processing of Comparative Example 2, which did not include a substrate, was inferior in grinding ability.

Claims

1. An adhesive sheet for workpiece processing, comprising a buffer layer, a substrate, and an adhesive layer, wherein the buffer layer is a layer containing a cured product of a thermosetting resin composition.

2. The adhesive sheet for workpiece processing according to claim 1, wherein the thermosetting resin composition contains a polyester resin.

3. The adhesive sheet for workpiece processing according to claim 2, wherein the polyester resin is a polyester urethane resin.

4. An adhesive sheet for workpiece processing as described in claim 2 or 3, wherein the polyester resin is a polyester resin having two or more hydroxy groups, and the thermosetting resin composition further contains a polyvalent isocyanate compound.

5. An adhesive sheet for workpiece processing according to any one of claims 1 to 3, having the buffer layer on one side of the substrate and the adhesive layer on the other side of the substrate.

6. The adhesive sheet for workpiece processing according to any one of claims 1 to 3, which is used for grinding a workpiece.

7. An adhesive sheet for workpiece processing according to any one of claims 1 to 3, wherein the workpiece has a groove on its surface or a modified region inside, and the adhesive sheet for workpiece processing is attached to the surface of the workpiece and fixed, and the back surface of the workpiece is ground to separate the workpiece into a plurality of individual workpieces starting from the groove or the modified region.

8. A method for producing an adhesive sheet for workpiece processing according to any one of claims 1 to 3, comprising a step of curing the thermosetting resin composition by heating.

9. A method for manufacturing an electronic device, comprising the steps of: attaching the adhesive sheet for workpiece processing described in any one of claims 1 to 3 to the surface of a workpiece, with the adhesive layer serving as an attachment surface; and grinding the back surface of the workpiece while the adhesive sheet for workpiece processing attached to the workpiece is fixed.

10. A method for manufacturing an electronic device, comprising: a division line forming step, which is step a) of forming grooves on the surface of a workpiece, or step b) of forming modified regions inside the workpiece from the surface or back surface of the workpiece; a sheet attaching step, after step a) or before or after step b), of attaching an adhesive sheet for workpiece processing according to any one of claims 1 to 3 to the surface of the workpiece, with the adhesive layer serving as an attachment surface; and a grinding and singulating step, with the adhesive sheet for workpiece processing attached to the workpiece fixed, grinding the back surface of the workpiece to singulate the workpiece into a plurality of workpieces starting from the grooves or the modified regions.

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