Bonding sheet for workpiece processing, method for manufacturing the same, and method for manufacturing electronic device

Abstract

The present application provides an adhesive sheet for workpiece processing having a buffer layer, a substrate, and an adhesive layer, and the buffer layer is a layer containing a cured product of a thermosetting resin composition, and a method for manufacturing an electronic device using the same.

Description

Technical Field

[0001] This invention relates to adhesive sheets for workpiece processing and methods for manufacturing the same, as well as methods for manufacturing electronic devices. Background Technology

[0002] As information terminal equipment rapidly develops towards thinner, smaller, and more multifunctional designs, it also demands thinner and higher-density electronic devices such as semiconductor devices mounted on these devices.

[0003] As a method for thinning electronic devices, a method for grinding the back side of workpieces such as semiconductor wafers used in electronic devices has been developed. Back side grinding is performed with a workpiece processing adhesive sheet (hereinafter also referred to as a "back grinding sheet") for back grinding attached to the surface of the workpiece, and the surface of the workpiece protected by the sheet. The back grinding sheet can be peeled off and removed from the surface of the workpiece after back side grinding.

[0004] In recent years, practical grinding and monolithic methods for achieving thinner profiles while minimizing damage to workpieces have included pre-cutting and stealth pre-cutting. Pre-cutting involves creating grooves of a predetermined depth on the workpiece surface using a cutting tool, then grinding the workpiece from the back side until reaching the grooves, thereby monolithicizing the workpiece into a single piece. Stealth pre-cutting, on the other hand, involves creating modified regions inside the workpiece using laser irradiation, then grinding the workpiece from the back side, cutting off the modified regions as the dividing point, thereby monolithicizing a semiconductor chip. These methods also utilize back abrasive pads to protect the workpiece surface.

[0005] For adhesive sheets used in workpiece machining, good grindability is required to stably hold the workpiece during machining and to suppress cracks and other defects in the workpiece.

[0006] As an adhesive sheet for workpiece processing, for example, an adhesive tape for semiconductor processing has been proposed, which has a substrate, a buffer layer disposed on at least one side of the substrate, and an adhesive layer disposed on the other side of the substrate. The buffer layer has a Young's modulus of 10 to 400 MPa and a fracture energy of 1 to 9 MJ / m at 23°C. 3 The Young's modulus of the above-mentioned substrate at 23°C is greater than that of the above-mentioned buffer layer (see Patent Document 1).

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: International Publication No. 2020 / 003920 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] In the semiconductor processing adhesive tape of Patent Document 1, the buffer layer is provided to absorb vibrations generated during workpiece grinding, mitigate unevenness caused by foreign objects, stabilize the workpiece, and maintain its flatness.

[0012] However, for adhesive sheets used in workpiece machining, unpleasant odors can sometimes be generated during manufacturing, storage, or use due to the composition of the adhesive sheet. With the increasing emphasis on the working environment, there is a demand for adhesive sheets used in workpiece machining to have low unpleasant odors. However, it is difficult to achieve excellent low unpleasant odor properties while maintaining good workpiece machinability.

[0013] The present invention was made in view of the above-mentioned actual situation, and its object is to provide a workpiece processing adhesive sheet with low unpleasant odor and excellent machinability, a method for manufacturing the same, and a method for manufacturing an electronic device using the above-mentioned workpiece processing adhesive sheet.

[0014] Methods for solving problems

[0015] The inventors conducted in-depth research and discovered that by providing a buffer layer containing a cured thermosetting resin composition in an adhesive sheet for workpiece processing, the above-mentioned problems can be solved, thereby completing the following invention.

[0016] That is, the present invention relates to the following [1]~

[10] .

[0017] [1] An adhesive sheet for workpiece processing, comprising a buffer layer, a substrate and an adhesive layer,

[0018] The aforementioned buffer layer is a cured layer containing a thermosetting resin composition.

[0019] [2] According to the adhesive sheet for workpiece processing described in [1] above, wherein,

[0020] The above thermosetting resin composition contains polyester resin.

[0021] [3] According to the adhesive sheet for workpiece processing described in [2] above, wherein,

[0022] The aforementioned polyester resin is a polyester urethane resin.

[0023] [4] The adhesive sheet for workpiece processing according to [2] or [3] above, wherein,

[0024] The aforementioned polyester resin is a polyester resin having two or more hydroxyl groups, and the aforementioned thermosetting resin composition further contains a polyisocyanate compound.

[0025] [5] An adhesive sheet for workpiece processing according to any one of [1] to [4] above, wherein,

[0026] The aforementioned buffer layer is provided on one side of the aforementioned substrate, and the aforementioned adhesive layer is provided on the other side of the aforementioned substrate.

[0027] [6] The adhesive sheet for workpiece processing according to any one of [1] to [5] above is used for grinding workpieces.

[0028] [7] An adhesive sheet for workpiece processing according to any one of [1] to [5] above, wherein,

[0029] The workpiece has grooves on its surface or modified areas inside.

[0030] The aforementioned adhesive sheet for workpiece processing is used to: grind the back side of the workpiece while the adhesive sheet for workpiece processing is fixed to the surface of the workpiece, and to divide the workpiece into multiple workpiece monoliths starting from the groove or the modified area.

[0031] [8] A method for manufacturing an adhesive sheet for workpiece processing, comprising the method of manufacturing an adhesive sheet for workpiece processing as described in any one of [1] to [7] above, the method comprising:

[0032] The process of curing the above-mentioned thermosetting resin composition by heating it.

[0033] [9] A method for manufacturing an electronic device, the method comprising:

[0034] The process of attaching the adhesive sheet for workpiece processing as described in any one of [1] to [7] above to the surface of the workpiece using the adhesive layer as the adhesive surface; and

[0035] The process of grinding the back of the workpiece while the adhesive sheet for workpiece processing attached to the workpiece is fixed in place.

[0036]

[10] A method for manufacturing an electronic device, the method comprising:

[0037] The process of forming a predetermined dividing line includes process a, which is forming a groove on the surface of a workpiece, or process b, forming a modified region inside the workpiece from the surface or back of the workpiece.

[0038] In the sheet bonding process, after step a above, or before or after step b above, the adhesive sheet for workpiece processing described in any one of [1] to [7] above is bonded to the surface of the workpiece using the adhesive layer as the bonding surface; and

[0039] In the grinding and monolithization process, the back side of the workpiece is ground while the adhesive sheet for workpiece processing is fixed to the workpiece. The workpiece is monolithized into multiple workpiece monoliths starting from the groove or the modified area.

[0040] The effects of the invention

[0041] According to the present invention, a workpiece processing adhesive sheet with low unpleasant odor and excellent machinability, and a method for manufacturing an electronic device using the workpiece processing adhesive sheet, are provided. Detailed Implementation

[0042] In this specification, the lower limit and upper limit values ​​of the preferred numerical range are described in a hierarchical manner and can be combined independently. For example, based on the description "preferred to be 10 to 90, more preferably 30 to 60", the "preferred lower limit value (10)" and the "more preferably upper limit value (60)" can be combined to obtain "10 to 60".

[0043] In this specification, "active ingredient" means any component in the composition to which the object is made, excluding the diluent.

[0044] In this specification, the number-average molecular weight (Mn) and weight-average molecular weight (Mw) are values ​​converted from standard polystyrene determined by gel permeation chromatography (GPC), specifically, values ​​determined based on the methods described in the examples.

[0045] In this specification, for example, "(meth)acrylic acid" means both "acrylic acid" and "methacrylic acid", and so on.

[0046] In this specification, "energy ray" refers to a ray containing energy quanta within an electromagnetic wave or a beam of charged particles. Examples of such rays include ultraviolet light, radiation, and electron beams. For instance, ultraviolet light sources such as electrodeless lamps, high-pressure mercury lamps, metal halide lamps, and UV-LEDs can be used to irradiate the target area. Regarding electron beams, electron beams generated by electron beam accelerators or similar devices can be used for irradiation.

[0047] In this specification, "energy-ray polymerizability" refers to the property of polymerization occurring upon irradiation with energy rays. Furthermore, "energy-ray curing property" refers to the property of curing occurring upon irradiation with energy rays, and "non-energy-ray curing property" refers to the property that does not possess energy-ray curing properties.

[0048] In this specification, "workpiece" refers to a plate-shaped body formed by pasting the workpiece processing adhesive sheet of this embodiment and then processing it.

[0049] Examples of workpieces include: wafers, panel-level packages, strips (elongated substrates) sealed with molding resin, etc., among which wafers are preferred from the viewpoint of easily obtaining the effects of the present invention.

[0050] The wafer can be, for example, a semiconductor wafer such as a silicon wafer, gallium arsenide wafer, silicon carbide wafer, gallium nitride wafer, or indium phosphide wafer, or an insulator wafer such as a glass wafer, lithium tantalate wafer, or lithium niobate wafer. Additionally, it can be a reconstructed wafer formed from resin and semiconductor for use in fan-out packaging and the like. From the viewpoint of easily obtaining the effects of the present invention, a semiconductor wafer or an insulator wafer is preferred, more preferably a semiconductor wafer, and even more preferably a silicon wafer.

[0051] Circuits such as wiring, capacitors, diodes, and transistors are typically formed on the surface of a semiconductor wafer. These circuits can be formed using known methods such as etching and lift-off.

[0052] There is no particular limitation on the thickness of the workpiece before processing; it is usually 500~1000μm.

[0053] In this specification, "workpiece monolithization" refers to an object after the workpiece has been divided. For example, if the workpiece is a semiconductor wafer, the workpiece monolithization is a semiconductor chip; if the workpiece is a strip (elongated substrate) that has undergone panel-level packaging or molding resin sealing, the workpiece monolithization is a semiconductor package.

[0054] In this specification, "electronic device" may include, for example, a workpiece, a workpiece monolith, an electronic component comprising the workpiece monolith, and an electronic device having the electronic component.

[0055] In this specification, the “surface” of a workpiece refers to the surface on which a circuit is formed, and the “back side” refers to the surface on which a circuit is not formed.

[0056] The mechanism of action described in this specification is speculative and does not limit the mechanism by which the adhesive sheet for workpiece processing of the present invention achieves its effect.

[0057] [Adhesive sheet for workpiece machining]

[0058] The adhesive sheet for workpiece processing in this embodiment (hereinafter also referred to as "adhesive sheet") has a buffer layer, a substrate and an adhesive layer, wherein the buffer layer is a layer containing a cured thermosetting resin composition.

[0059] In this embodiment, the adhesive sheet is adhered to the surface of a workpiece to protect the surface while performing a given machining operation on the workpiece. After the given machining operation is performed on the workpiece, the adhesive sheet of this embodiment is peeled off and removed from the workpiece.

[0060] The laminated structure of the adhesive sheet in this embodiment is not particularly limited as long as it can bond the adhesive layer to the workpiece. For example, it can be a structure with a buffer layer on one side of the substrate and an adhesive layer on the other side of the substrate, or it can be a structure with a substrate, a buffer layer and an adhesive layer in sequence. From the viewpoint of easily obtaining better machinability, it is preferable to have a buffer layer on one side of the substrate and an adhesive layer on the other side of the substrate.

[0061] The adhesive sheet of this embodiment may have layers other than the buffer layer, the substrate and the adhesive layer, or it may not have layers other than the buffer layer, the substrate and the adhesive layer.

[0062] Examples of layers other than the buffer layer, substrate, and adhesive layer include: an intermediate layer disposed between the substrate and the adhesive layer, and a release sheet disposed on the surface of the adhesive sheet.

[0063] Hereinafter, each component constituting the adhesive sheet of this embodiment will be described in turn.

[0064] <Buffer Layer>

[0065] The adhesive sheet of this embodiment, by having a buffer layer, can absorb vibrations and impacts generated during processing such as grinding of the workpiece, preventing cracks from forming in the workpiece. Furthermore, by providing the buffer layer, it can also absorb unevenness or foreign objects present on the worktable of the support device, improving the support device's ability to hold the adhesive sheet.

[0066] The buffer layer of the adhesive sheet in this embodiment is a layer containing a cured thermosetting resin composition. By making the buffer layer a layer containing a cured thermosetting resin composition, the adhesive sheet of this embodiment exhibits excellent low odor and machinability. Although the reason is not yet certain, it can be speculated as follows: When the raw materials constituting the thermosetting resin composition are heated to form a cross-linked structure, the raw materials that cause unpleasant odors are less likely to remain, thus suppressing the unpleasant odor of the buffer layer, and it can be considered that excellent low odor can be obtained. Furthermore, it can be considered that due to the good shape retention provided by the cross-linked structure of the cured thermosetting resin composition, the workpiece can be well maintained during grinding, and excellent machinability can be obtained.

[0067] The buffer layer of the adhesive sheet in this embodiment can be any layer containing a cured thermosetting resin composition.

[0068] From the viewpoint of low unpleasant odor and abrasiveness, the content of cured thermosetting resin composition in the buffer layer of the 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 adhesive sheet of this embodiment is preferably a cured thermosetting resin composition after layer formation (that is, the buffer layer of the adhesive sheet of this embodiment is composed only of cured thermosetting resin composition).

[0069] The above-mentioned thermosetting resin composition will now be described in detail.

[0070] (Thermosetting resin composition)

[0071] Thermosetting resin composition can be any thermosetting resin composition, without any particular limitation.

[0072] The thermosetting resin contained in the thermosetting resin composition may be a resin that exhibits thermosetting properties on its own, or a resin that exhibits thermosetting properties by being used in combination with one or more selected from crosslinking agents and catalysts.

[0073] [Thermosetting resins]

[0074] Examples of thermosetting resins include epoxy resins, phenolic resins, silicone resins, melamine resins, acrylic resins, and polyester resins. Among these, polyester resins are preferred from the viewpoint of low odor and good abrasiveness.

[0075] Thermosetting resins can be used alone or in combination of two or more.

[0076] Examples of polyester resins include polymers obtained by polycondensation of alcohol and carboxylic acid components, wherein the alcohol component is ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentanediol, cyclohexane-1,4-diethanol, hydrogenated bisphenol A, ethylene oxide or propylene oxide adducts of bisphenol A, etc., and the carboxylic acid component is terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, adipic acid, azelaic acid, maleic acid, fumaric acid, itaconic acid, their anhydrides, etc.

[0077] Alcohol and carboxylic acid components can be used individually or in combination.

[0078] Polyester resins can be resins modified from polyester. From the viewpoint of low unpleasant odor and abrasive properties, polyester urethane resins modified from polyester are preferred. It should be noted that in this specification, polyester urethane resins are also included in the concept of polyester resins, and the preferred method for polyester resins can be replaced with the preferred method for polyester urethane resins.

[0079] Examples of polyester urethane resins include resins obtained by reacting a polyisocyanate compound with a polyester polyol, wherein the polyester polyol is a polyester polyol with hydroxyl groups at the end obtained by polycondensation of the alcohol component and the carboxylic acid component.

[0080] The polyisocyanate compound used as a raw material component of polyester urethane resin can be any compound among aromatic polyisocyanate compounds, aliphatic polyisocyanate compounds, and alicyclic polyisocyanate compounds. Specific examples of such polyisocyanate compounds include diphenylmethane diisocyanate, toluene diisocyanate, 1,3-phenylenediethylene diisocyanate, isophorone diisocyanate, and 1,6-hexane diisocyanate.

[0081] Polyester polyols and polyisocyanate compounds, which are raw material components of polyester urethane resins, can be used individually or in combination.

[0082] Polyester resins have reactive functional groups for thermosetting. From the viewpoint of good thermosetting properties, it is preferable to have two or more hydroxyl groups, and more preferably two or more hydroxyl groups at the molecular ends. It should be noted that "molecular ends" in the case of a linear polyester resin refers to its two ends, and in the case of a branched polyester resin, it also includes the ends of the branches. Specifically, in the case of a linear polyester resin, it is preferable to have hydroxyl groups at both ends.

[0083] The glass transition temperature (Tg) of polyester resins is not particularly limited, but is preferably 50~140℃, more preferably 60~120℃, and even more preferably 70~110℃.

[0084] When the glass transition temperature (Tg) of polyester resin is above the lower limit mentioned above, it tends to suppress excessive deformation of the buffer layer during workpiece processing. Furthermore, when the glass transition temperature (Tg) of polyester resin is below the upper limit mentioned above, it tends to improve the absorption of vibrations and impacts generated during workpiece grinding and enhance the retention of the adhesive sheet.

[0085] The glass transition temperature (Tg) of polyester resins can be determined according to JIS K 7121:2012.

[0086] The number average molecular weight (Mn) of polyester resins 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.

[0087] When the number average molecular weight (Mn) of the polyester resin is above the lower limit mentioned above, it tends to suppress excessive deformation of the buffer layer during workpiece processing. Furthermore, when the number average molecular weight (Mn) of the polyester resin is below the upper limit mentioned above, it tends to improve the absorption of vibrations and impacts generated during grinding of the workpiece and the retention of the adhesive sheet.

[0088] The hydroxyl value of the polyester resin is not particularly limited, but is preferably 0.5~30 KOH mg / g, more preferably 1~25 KOH mg / g, and even more preferably 2~20 KOH mg / g.

[0089] When the hydroxyl value of polyester resin is above the lower limit mentioned above, its thermosetting properties become good, and it tends to suppress excessive deformation of the buffer layer during workpiece processing while improving low unpleasant odor properties. Furthermore, when the hydroxyl value of polyester resin is below the upper limit mentioned above, it tends to improve the absorption of vibrations and impacts generated during workpiece grinding and the retention of the adhesive sheet.

[0090] The hydroxyl value of polyester resins can be determined according to JIS K 0070:1992.

[0091] When the thermosetting resin composition contains polyester resin, the content of polyester resin in the thermosetting resin composition is not particularly limited, but is preferably 30 to 98% by mass relative to the total solid content (100% by mass) of the thermosetting resin composition, more preferably 50 to 98% by mass, and even more preferably 70 to 98% by mass.

[0092] When the content of polyester resin is within the above range, it tends to have lower unpleasant odor and better abrasive properties.

[0093] It should be noted that in this specification, "total solid content of the thermosetting resin composition" refers to the components other than the solvent contained in the thermosetting resin composition. Components other than the solvent are considered solid components even if they are liquid at room temperature (23°C).

[0094] It should be noted that extrusion molding is a common molding method for polyester resins. However, since extrusion molding requires heating the polyester resin to high temperatures, it places a heavy burden on equipment and energy, making it difficult to achieve good productivity. Furthermore, problems specific to extrusion molding, such as the formation of cavities, can occur, hindering the attainment of excellent quality stability. In contrast, in the adhesive sheet of this embodiment, since polyester resin is used as the raw material for the thermosetting resin composition, a buffer layer with uniform quality can be formed under relatively mild heating conditions. Therefore, the adhesive sheet of this embodiment exhibits excellent productivity and excellent quality stability.

[0095] The content of thermosetting resin in the thermosetting resin composition is not particularly limited, but is preferably 30 to 98% by mass relative to the total solid content (100% by mass) of the thermosetting resin composition, more preferably 50 to 98% by mass, and even more preferably 70 to 98% by mass.

[0096] When the content of thermosetting resin is within the above range, it tends to have a lower unpleasant odor and better machinability.

[0097] [Cross-linking agent]

[0098] Thermosetting resin compositions may contain crosslinking agents for crosslinking the thermosetting resin, as needed. A single crosslinking agent may be used, or two or more may be used in combination.

[0099] Crosslinking agents can be well-known compounds that correspond to the type of reactive groups present in the thermosetting resin to which they are crosslinked. Examples include: isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, melamine crosslinking agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, ammonium salt crosslinking agents, etc.

[0100] In the case of the thermosetting resin composition containing a polyester resin having two or more hydroxyl groups, from the viewpoint of improving thermosetting properties, the crosslinking agent is preferably an isocyanate-based crosslinking agent. The isocyanate-based crosslinking agent is preferably a polyisocyanate compound. Since polyisocyanate compounds are reactive with hydroxyl groups, they can bond hydroxyl-containing polyester resins to form a crosslinked structure.

[0101] Depending on the type of thermosetting resin to which the crosslinking is applied, the number of isocyanate groups in the polyisocyanate compound can be, for example, two or three, or more than three.

[0102] Examples of polyisocyanate compounds include: aromatic isocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, phenyl 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, bicycloheptanane triisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, and hydrogenated phenyl diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate; and so on.

[0103] In addition, the polyisocyanate compound can be the biuret or isocyanurate form of the compounds exemplified above; adducts of these compounds with the reaction products of non-aromatic low-molecular-weight compounds containing active hydrogen, such as ethylene glycol, trimethylolpropane, and castor oil; and other modified forms.

[0104] From the viewpoint of easily obtaining good reactivity, the adduct of trimethylolpropane is preferred.

[0105] When the thermosetting resin composition contains a polyester resin having two or more hydroxyl groups and a polyisocyanate compound, the content of the polyisocyanate compound in the thermosetting resin composition is not particularly limited, but is preferably 1 to 15 parts by weight relative to 100 parts by weight of the polyester resin having two or more hydroxyl groups.

[0106] When the content of polyisocyanate compounds is within the above range, the adhesive sheet tends to have a lower unpleasant odor and better abrasive properties.

[0107] 〔catalyst〕

[0108] Thermosetting resin compositions may contain catalysts to promote the thermosetting reaction of the resin, as needed. A single catalyst may be used, or two or more catalysts may be used in combination.

[0109] Examples of catalysts include organometallic compounds and tertiary amine compounds. Among these, organometallic compounds are preferred from a reactivity point of view.

[0110] As organometallic compounds, tin-based organometallic compounds are preferred, such as: dibutyltin diacetate, dibutyltin dioctanoate, dibutyltin dilaurate, di(2-ethylhexanoate)dibutyltin, dibutyltin dineodecanate, dioctyltin diacetate, dioctyltin dioctanoate, dioctyltin dilaurate, di(2-ethylhexanoate)dioctyltin, dioctyltin dineodecanate, etc. From a reactivity point of view, dioctyltin dilaurate is preferred. Other organometallic compounds include: metal carboxylates of bismuth, titanium, zirconium, zinc, iron, etc. (e.g., octanoic acid compounds, naphthenic acid compounds, stearic acid compounds, etc.), metal chelates, metal alkoxides, etc. These can be used alone or in combination of two or more.

[0111] 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 weight relative to 100 parts by weight of the thermosetting resin, more preferably 0.05 to 5 parts by weight, and even more preferably 0.1 to 1 part by weight.

[0112] When the catalyst content is within the above range, the thermosetting reaction can proceed uniformly and fully.

[0113] [Other ingredients]

[0114] Without impairing the effects of the present invention, the thermosetting resin composition may contain other components. Examples of other components include resin components other than those described above; antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, dyes, and other additives; etc.

[0115] (Young's modulus of the buffer layer)

[0116] The Young's modulus of the buffer layer at 23°C is not particularly limited, but is preferably 200~4000MPa, more preferably 1000~3500MPa, and even more preferably 1500~3200MPa.

[0117] When the Young's modulus of the buffer layer at 23°C is above the lower limit mentioned above, it tends to suppress excessive deformation of the buffer layer during workpiece processing. Furthermore, when the Young's modulus of the buffer layer at 23°C is below the upper limit mentioned above, it tends to improve the absorption of vibrations and impacts generated during workpiece grinding and the retention of the adhesive sheet.

[0118] It should be noted that the Young's modulus of the buffer layer at 23°C can be determined using the method described in the examples.

[0119] (Thickness of the buffer layer)

[0120] The thickness of the buffer layer is not particularly limited, but is preferably 2~100μm, more preferably 3~60μm, even more preferably 4~40μm, and even more preferably 5~30μm.

[0121] When the thickness of the buffer layer is above the lower limit mentioned above, it tends to absorb vibrations and impacts generated during grinding of the workpiece and has a higher retention capacity for the adhesive sheet. Furthermore, when the thickness of the buffer layer is below the upper limit mentioned above, it tends to suppress excessive deformation of the buffer layer during workpiece processing and also offers excellent economic efficiency.

[0122] <Adhesive layer>

[0123] The adhesive layer is not particularly limited, but is preferably formed of an energy-curable adhesive. By forming the adhesive layer with an energy-curable adhesive, sufficient adhesion can be used to protect the workpiece surface well before energy-curing, and the peel force can be reduced after energy-curing, thereby achieving easy peeling from the workpiece.

[0124] Examples of energy ray curable adhesives include, for example, the X-type adhesive composition, the Y-type adhesive composition, and the XY-type adhesive composition described below.

[0125] 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.

[0126] Type Y adhesive composition: An energy-ray curable adhesive composition containing an energy-ray curable adhesive resin (hereinafter also referred to as "Adhesive Resin II") with unsaturated groups introduced into the side chains of a non-energy-ray curable adhesive resin, but not containing energy-ray curable compounds other than the adhesive resin.

[0127] XY type adhesive composition: an energy-ray curable adhesive composition containing the above-mentioned energy-ray curable adhesive resin II and energy-ray curable compounds other than the adhesive resin.

[0128] Among them, the energy-curable adhesive is preferably an XY-type adhesive composition. By using an XY-type adhesive composition, there is a tendency to have sufficient adhesion before curing, while on the other hand, to sufficiently reduce the peel force relative to the workpiece after curing.

[0129] The adhesive forming the adhesive layer can also be a layer formed by a non-energy-curable adhesive that will not cure even when exposed to energy rays. Examples of non-energy-curable adhesives include adhesives containing adhesive resin I but not adhesive resin II or energy-curable compounds.

[0130] Next, we will provide a more detailed explanation of the components that make up the adhesive layer.

[0131] In the following description, the term "adhesive resin" is used to mean one or both of adhesive resin I and adhesive resin II. Furthermore, in the following description, when referred to only as "adhesive composition," it is considered to include the concepts of type X adhesive compositions, type Y adhesive compositions, type XY adhesive compositions, and other adhesive compositions besides these.

[0132] Examples of adhesive resins include acrylic resins, urethane resins, rubber resins, and silicone resins. Among these, acrylic resins are preferred.

[0133] (Acrylic resins)

[0134] Acrylic resins preferably contain structural units derived from alkyl methacrylates.

[0135] Examples of alkyl (meth)acrylates include, for example, alkyl (meth)acrylates in which the alkyl group has 1 to 20 carbon atoms.

[0136] The alkyl groups in (meth)acrylates can be either straight-chain or branched.

[0137] From the viewpoint of further improving the adhesive strength of the adhesive layer, acrylic resins preferably contain structural units of (meth)acrylate alkyl esters with 4 or more carbon atoms derived from alkyl groups.

[0138] The structural units of (meth)acrylate alkyl esters containing alkyl groups with 4 or more carbon atoms can be a single type or two or more types.

[0139] The alkyl ester of (meth)acrylate having 4 or more carbon atoms preferably has 4 to 12 carbon atoms, more preferably 4 to 8, and even more preferably 4 to 6.

[0140] Examples of alkyl (meth)acrylates having 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. Butyl (meth)acrylate is preferred, and butyl acrylate is more preferred.

[0141] When an acrylic resin contains a structural unit of (meth)acrylate alkyl ester with 4 or more carbon atoms derived from an alkyl group, from the viewpoint of further improving the adhesive strength of the adhesive layer, its content in the acrylic resin is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 45 to 60% by mass.

[0142] From the viewpoint of improving the storage modulus G' and adhesive properties of the adhesive layer, acrylic resins preferably contain structural units of (meth)acrylate alkyl esters with 4 or more carbon atoms derived from alkyl groups, as well as structural units of (meth)acrylate alkyl esters with 1 to 3 carbon atoms derived from alkyl groups.

[0143] The structural units of alkyl (meth)acrylates with 1 to 3 carbon atoms derived from alkyl groups contained in acrylic resins can be a single type or two or more types.

[0144] Alkyl methacrylates having 1 to 3 carbon atoms as the alkyl group include, for example, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, and n-propyl methacrylate. Among these, methyl methacrylate and ethyl methacrylate are preferred, methyl methacrylate is more preferred, and methyl methacrylate is even more preferred.

[0145] When an acrylic resin contains a structural unit of an alkyl (meth)acrylate with 1 to 3 carbon atoms derived from an alkyl group, the content of the alkyl group in the acrylic resin is preferably 1 to 35% by mass, more preferably 5 to 30% by mass, and even more preferably 15 to 25% by mass.

[0146] Acrylic resins preferably further contain structural units derived from monomers containing functional groups.

[0147] By incorporating structural units derived from functionalized monomers into acrylic resins, functional groups that serve as crosslinking initiation points for reactions with crosslinking agents, or functional groups that can react with compounds containing unsaturated groups to introduce unsaturated groups into the side chains of acrylic resins, can be introduced.

[0148] The structural units in acrylic resins derived from functional group monomers can be one or more.

[0149] Examples of functional group-containing monomers include hydroxyl-containing monomers, carboxyl-containing monomers, amino-containing monomers, and epoxy-containing monomers. Among these, hydroxyl-containing monomers and carboxyl-containing monomers are preferred, and hydroxyl-containing monomers are more preferred.

[0150] Examples of hydroxyl-containing monomers include: 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, and other hydroxyalkyl methacrylates; unsaturated alcohols such as vinyl alcohol and allyl alcohol; and so on.

[0151] Examples of carboxyl-containing monomers include: (meth)acrylic acid, crotonic acid, and other olefinic unsaturated monocarboxylic acids; fumaric acid, itaconic acid, maleic acid, citraconic acid, and other olefinic unsaturated dicarboxylic acids and their anhydrides; 2-carboxyethyl methacrylate; and so on.

[0152] When acrylic resins contain structural units derived from monomers with functional groups, their content is not particularly limited, but is preferably 5 to 45% by mass, more preferably 15 to 40% by mass, and even more preferably 25 to 35% by mass in acrylic resins.

[0153] In addition to the structural units mentioned above, acrylic resins may also contain structural units derived from other monomers that can copolymerize with acrylic monomers.

[0154] The structural units derived from other monomers contained in acrylic resins can be one or more.

[0155] Other monomers that can be listed include: styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, acrylamide, etc.

[0156] In acrylic resins, unsaturated groups with energy-ray polymerizability can be further introduced to impart energy-ray curability.

[0157] Unsaturated groups can be introduced, for example, by reacting a functional group of an acrylic resin containing a structural unit derived from a functional group monomer with a reactive substituent that is reactive with the functional group and an unsaturated group (hereinafter also referred to as "compound containing unsaturated groups"). A compound containing unsaturated groups can be used alone or in combination of two or more.

[0158] Examples of unsaturated groups in compounds containing unsaturated groups include (meth)acryloyl, vinyl, and allyl groups. Among these, (meth)acryloyl is preferred.

[0159] Examples of reactive substituents in compounds containing unsaturated groups include isocyanate groups and glycidyl groups.

[0160] Examples of compounds containing unsaturated groups include (meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, and (meth)acrylate glycidyl ester.

[0161] When reacting an acrylic resin containing structural units derived from functional group monomers with a compound containing unsaturated groups, the ratio of the total number of functional groups in the acrylic resin that react with the compound containing unsaturated groups 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%.

[0162] When the ratio of functional groups that react with compounds containing unsaturated groups is within the above range, acrylic resins can be endowed with sufficient energy-curable properties, and the functional groups that have not reacted with compounds containing unsaturated groups can react with the crosslinking agent to crosslink the acrylic resins.

[0163] The weight-average molecular weight (Mw) of acrylic resins 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 weight-average molecular weight (Mw) of acrylic resins is within the above range, there is a tendency for the adhesive strength and cohesiveness of the adhesive layer to become better.

[0164] (Compounds that are cured by energy rays)

[0165] The energy-curable compound contained in the X-type or XY-type adhesive composition is preferably a monomer or oligomer having unsaturated groups in its molecule and capable of being cured by irradiation with energy rays.

[0166] Examples of energy-curable compounds include: trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and other poly(meth)acrylate monomers; urethane (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, epoxy (meth)acrylates, and other oligomers; etc. Among these, urethane (meth)acrylate oligomers are preferred from the viewpoint of having a higher molecular weight and being less likely to cause a decrease in the elastic modulus of the adhesive layer.

[0167] The molecular weight of the energy-curable compound is not particularly limited, but is preferably 100-12000, more preferably 200-10000, further preferably 400-8000, and even more preferably 600-6000. It should be noted that when the energy-curable compound is an oligomer, the above molecular weights represent weight-average molecular weight (Mw).

[0168] The content of the energy-curable compound in the XY type adhesive composition is not particularly limited, but is preferably 1 to 30 parts by weight relative to 100 parts by weight of adhesive resin, more preferably 2 to 20 parts by weight, and even more preferably 3 to 15 parts by weight.

[0169] When the content of the energy-curing compound in the XY type adhesive composition is within the above range, there is a tendency for a good balance to be achieved between the adhesive strength before energy irradiation and the peel strength after energy irradiation. It should be noted that, since the adhesive resin in the XY type adhesive composition is energy-curing, there is a tendency for the peel strength to be sufficiently reduced after energy irradiation even if the content of the energy-curing compound is low.

[0170] (Cross-linking agent)

[0171] The adhesive composition preferably further contains a crosslinking agent.

[0172] Crosslinking agents are, for example, components that crosslink adhesive resins with each other by reacting with functional groups derived from functional group-containing monomers.

[0173] Crosslinking agents can be used alone or in combination of two or more.

[0174] Examples of crosslinking agents include: isocyanate crosslinking agents such as toluene diisocyanate, hexamethylene diisocyanate, and their adducts; epoxy crosslinking agents such as ethylene glycol glycidyl ether; aziridine crosslinking agents such as hexa[1-(2-methyl)-aziridinyl]triazine triphosphate; chelate crosslinking agents such as aluminum chelates; and so on. Among these, isocyanate crosslinking agents are preferred from the viewpoint of improving cohesiveness and thus further enhancing adhesiveness, as well as from the viewpoint of ease of acquisition.

[0175] When the adhesive composition contains a crosslinking agent, its content is not particularly limited. From the viewpoint of allowing the crosslinking reaction to proceed moderately, it 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 4 parts by weight, relative to 100 parts by weight of the adhesive resin.

[0176] (Photopolymerization initiator)

[0177] When the adhesive is an energy-curable adhesive, the adhesive composition preferably further contains a photopolymerization initiator. By including a photopolymerization initiator in the energy-curable adhesive, there is a tendency to ensure that the curing reaction of the energy-curable adhesive can be fully carried out even using energy rays with lower energy, such as ultraviolet light.

[0178] Photopolymerization initiators can be used alone or in combination of two or more.

[0179] Examples of photopolymerization initiators include: benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, diacetic acid compounds, thioxanone compounds, peroxide compounds, and photosensitizers such as amines and quinones. More specifically, examples include: 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzylphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, bibenzyl, butanedione, 8-chloroanthraquinone, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0180] When the adhesive composition contains a photopolymerization initiator, its content is not particularly limited. From the viewpoint of ensuring that the energy ray curing reaction proceeds 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 adhesive resin.

[0181] (Other additives)

[0182] The adhesive composition may also contain other additives without compromising the effects of the present invention. Examples of other additives include, for instance, antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, dyes, etc.

[0183] (Organic solvents)

[0184] From the viewpoint of further improving the coatability to substrates, release sheets, etc., the adhesive composition can be diluted with an organic solvent to form a solution. Examples of organic solvents include those that may be contained in the thermosetting resin composition described later. The organic solvent can be the one used directly in the synthesis of the adhesive resin, or one or more organic solvents other than those used in the synthesis can be added.

[0185] 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.

[0186] When the thickness of the adhesive layer is above the aforementioned lower limit, there is a tendency to obtain excellent adhesion and better protect the surface of the workpiece during processing. Conversely, when the thickness of the adhesive layer is below the aforementioned upper limit, there is a tendency to suppress the generation of chips when cutting the adhesive sheet and better prevent workpiece breakage.

[0187] <Substrate>

[0188] Examples of resin films can be cited as substrates. Examples of resins constituting resin films include: polyethylene 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 copolymer, and norbornene resin; ethylene copolymers such as ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, and ethylene-(meth)acrylic acid copolymer; polyvinyl chloride such as polyvinyl chloride copolymer; polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and fully aromatic polyesters; polyurethane, polyimide, polyamide, polycarbonate, fluoropolymers, polyacetal, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyetherketone, and acrylic polymers; and so on.

[0189] The substrate can be a single-layer film formed from one or more resins selected from these resins, or a laminated film formed by stacking two or more of these resin films. Alternatively, it can be a modified film such as a cross-linked film or an ionomer film of the above-mentioned resins.

[0190] In these resin films, the substrate is preferably selected from one or more of polyester film, polyamide film, polyimide film and biaxially oriented polypropylene film, more preferably polyester film, and even more preferably polyethylene terephthalate film.

[0191] The Young's modulus of the substrate is not particularly limited, but is preferably 1000 MPa or more, more preferably 1800 to 30000 MPa, and even more preferably 2500 to 6000 MPa.

[0192] It should be noted that the Young's modulus of the substrate can be determined based on JIS K 7127:1999, at a test speed of 200 mm / min.

[0193] The thickness of the substrate is not particularly limited, but is preferably 10~200μm, more preferably 25~100μm, and even more preferably 30~70μm.

[0194] When the thickness of the substrate is above the aforementioned lower limit, there is a tendency to obtain sufficient strength to function as a support for the adhesive sheet. Furthermore, when the thickness of the substrate is below the aforementioned upper limit, there is a tendency to obtain moderately improved flexibility and processability.

[0195] It should be noted that "the thickness of the substrate" refers to the overall thickness of the substrate. In the case of a substrate composed of multiple layers, it refers to the total thickness of all the layers that make up the substrate.

[0196] The substrate may also contain plasticizers, lubricants, infrared absorbers, ultraviolet absorbers, fillers, colorants, antistatic agents, antioxidants, catalysts, etc., within a range that does not impair the effects of the present invention.

[0197] The substrate can be transparent or opaque, and can be colored or vapor-deposited as desired.

[0198] From the viewpoint of improving adhesion to other layers, surface treatments such as corona treatment can be applied to at least one side of the substrate, or a coating layer can be applied to improve adhesion.

[0199] <Peeling tablets>

[0200] The release tab protects the surface of the adhesive sheet by being peeled off before use and is removed when the adhesive sheet is used.

[0201] The peeling sheet can be a peeling sheet that has undergone single-sided peeling treatment or a peeling sheet that has undergone double-sided peeling treatment.

[0202] As a release sheet, a release sheet having a release agent such as an organosilicon resin coated on a release sheet substrate is preferably provided. As a release sheet substrate, a substrate identical to the substrate exemplified as the substrate of the adhesive sheet of this embodiment can be provided.

[0203] <Total thickness of adhesive sheet>

[0204] The total thickness of the adhesive sheet in this embodiment is not particularly limited, but is preferably 30-300 μm, more preferably 40-220 μm, and even more preferably 45-160 μm.

[0205] When the total thickness of the adhesive sheet is above the aforementioned lower limit, there is a tendency to appropriately maintain the adhesive properties of the adhesive layer and the impact absorption properties of the buffer layer, thus fully realizing its function as an adhesive sheet for workpiece processing. Conversely, when the total thickness of the adhesive sheet is below the aforementioned upper limit, there is a tendency to reduce the peeling force when the workpiece is peeled from the adhesive sheet.

[0206] It should be noted that when the adhesive sheet in this embodiment is provided with a release liner, the thickness of the release liner is not included in the "total thickness of the adhesive sheet".

[0207] <Young's modulus of adhesive sheet>

[0208] The Young's modulus of the adhesive sheet in this embodiment is not particularly limited at 23°C, but is preferably 1200~4200MPa, more preferably 1700~3700MPa, and even more preferably 2200~3200MPa.

[0209] When the Young's modulus of the adhesive sheet at 23°C is below the upper limit mentioned above, it tends to improve the absorption of vibrations and impacts generated during workpiece grinding and to enhance the retention of the adhesive sheet. Furthermore, when the Young's modulus of the adhesive sheet at 23°C is above the lower limit mentioned above, it tends to suppress excessive deformation of the adhesive sheet during workpiece machining.

[0210] It should be noted that the Young's modulus of the adhesive sheet at 23°C can be measured using the method described in the examples. In the case where the adhesive sheet of this embodiment is provided with a release liner, the "Young's modulus of the adhesive sheet" is measured after the release liner has been removed.

[0211] [Manufacturing method of adhesive sheet]

[0212] The method for manufacturing the adhesive sheet according to this embodiment includes a step of curing a thermosetting resin composition by heating it (hereinafter also referred to as the "thermosetting step"). Through this thermosetting step, the buffer layer of the adhesive sheet of this embodiment can be formed.

[0213] The thermosetting process is preferably a process in which the coating film formed by applying the thermosetting resin composition is heated to cure it.

[0214] When coating a thermosetting resin composition, the thermosetting resin composition is preferably in the form of a solution diluted with an organic solvent. By diluting with an organic solvent, the coating operation becomes easier, and the thickness of the buffer layer can be easily adjusted, allowing even a thin buffer layer to be formed with excellent thickness accuracy.

[0215] Examples of organic solvents include: methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, isopropanol, etc. Organic solvents can be used alone or in combination of two or more.

[0216] The content of organic solvent in the thermosetting resin composition after dilution with 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.

[0217] Thermosetting resin compositions can be applied to release sheets or directly to the surface of a substrate or adhesive layer.

[0218] Methods for coating thermosetting resin compositions include, for example, spin coating, spray coating, bar coating, doctor blade coating, roller coating, scraper coating, mold coating, gravure coating, etc.

[0219] From the viewpoint of the productivity of the adhesive sheet and the sufficient curing of the thermosetting resin composition, the heating temperature of the thermosetting resin composition is preferably 80~150°C, more preferably 90~140°C, and even more preferably 100~130°C.

[0220] Furthermore, from the viewpoint of the productivity of the adhesive sheet and the sufficient curing of the thermosetting resin composition, the heating time of 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.

[0221] When a release sheet with a buffer layer is obtained by coating a thermosetting resin composition onto the release sheet, the buffer layer of the release sheet with the buffer layer can then be adhered to the surface of the substrate or adhesive layer.

[0222] In the method for manufacturing the adhesive sheet in this embodiment, the method for forming the adhesive layer is not particularly limited; for example, a method of drying after coating with the above-described adhesive composition can be cited.

[0223] The adhesive composition can be applied to the release sheet or directly to the surface of the substrate or buffer layer. When a release sheet with an adhesive layer is obtained by applying the adhesive composition to the release sheet, the adhesive layer of the release sheet can then be simply adhered to the surface of the substrate or buffer layer. The method for applying the adhesive composition is described in the same manner as the method for applying the thermosetting resin composition described above.

[0224] <Uses of Adhesive Sheets>

[0225] Examples of workpiece processing performed with the adhesive sheet of this embodiment attached include: back grinding with the adhesive sheet attached to one side of the workpiece, cutting the workpiece into individual pieces with the adhesive sheet attached to one side of the workpiece, workpiece handling, and picking up individual workpiece pieces.

[0226] The adhesive sheet of this embodiment is suitable for grinding workpieces, more suitable for back grinding of workpieces, and even more suitable for back grinding of the back side of workpieces with the adhesive sheet of this embodiment attached to the circuit forming surface of the workpiece.

[0227] In particular, the adhesive sheet of this embodiment has the effect of suppressing cracks when the workpiece is thinned, and is therefore suitable for processes such as pre-cutting and invisible pre-cutting. Specifically, the workpiece has a groove on its surface or a modified area inside, and is suitable for grinding the back side of the workpiece while the adhesive sheet for workpiece processing is fixed to the surface of the workpiece, thereby using the groove or the modified area as a starting point to divide the workpiece into multiple workpiece monoliths.

[0228] [Manufacturing Method of Electronic Devices]

[0229] The method for manufacturing the electronic device in this embodiment includes:

[0230] The process of attaching the adhesive sheet for workpiece processing according to this embodiment to the surface of the workpiece using the aforementioned adhesive layer as the bonding surface; and

[0231] The process of grinding the back of the workpiece while the adhesive sheet for workpiece processing attached to the workpiece is fixed in place.

[0232] Furthermore, the preferred method for manufacturing the electronic device according to this embodiment includes:

[0233] The process of forming a predetermined dividing line includes process a, which is forming a groove on the surface of a workpiece, or process b, forming a modified region inside the workpiece from the surface or back of the workpiece.

[0234] The sheet bonding process involves bonding the workpiece processing adhesive sheet of this embodiment to the surface of the workpiece using the adhesive layer as the bonding surface, either after step a above or before or after step b above; and

[0235] In the grinding and monolithization process, the back side of the workpiece is ground while the adhesive sheet for workpiece processing is fixed to the workpiece. The workpiece is monolithized into multiple workpiece monoliths starting from the groove or the modified area.

[0236] Furthermore, the manufacturing method of the electronic device of this embodiment may also include a peeling process after the grinding and monolithization processes, in which the adhesive sheet for workpiece processing of this embodiment is peeled off from multiple workpieces.

[0237] It should be noted that the manufacturing method of the electronic device having the above-mentioned step a is equivalent to the pre-cutting process, and the manufacturing method of the electronic device having the above-mentioned step b is equivalent to the stealth pre-cutting process.

[0238] The following describes in detail each step of the manufacturing method of the electronic device according to this embodiment.

[0239] <Process for forming pre-defined dividing lines>

[0240] The process of forming a predefined dividing line is either process a, which forms a groove on the surface of a workpiece, or process b, which forms a modified region inside the workpiece from the surface or back of the workpiece.

[0241] Process a is the process of forming grooves on the surface of the workpiece, which is performed before the adhesive sheet is bonded to the surface of the workpiece.

[0242] In process a, the groove formed on the surface of the workpiece is shallower than the thickness of the workpiece. After process a, the workpiece is back-ground until it reaches the position of the groove formed in process a, thereby being divided into multiple workpiece monoliths. Therefore, in process a, the groove is formed along the dividing line when the workpiece is divided and monolithized.

[0243] The groove can be formed by cutting using existing, known wafer cutting equipment, etc.

[0244] Step b is the process of forming a modified region inside the workpiece from the surface or back of the workpiece. It can be performed before or after the adhesive sheet is attached to the surface of the workpiece.

[0245] In process b, a modified region is formed inside the workpiece by irradiating it with a laser whose focus is concentrated on the interior of the workpiece. This modified region is the part of the workpiece that has become brittle, the area where the workpiece has been thinned by back-side grinding or broken by the applied grinding force, thus becoming the starting point for the workpiece to be monolithized. Therefore, the modified region is formed along the dividing line when the workpiece is divided and monolithized.

[0246] Laser irradiation can be performed from either the surface or the back of the workpiece. When process b is performed after the sheet bonding process, the laser can be applied to the workpiece through the bonding sheet.

[0247] <Panel pasting process>

[0248] The adhesive bonding process is a process in which adhesive sheets are bonded to the surface of a workpiece with the adhesive layer as the bonding surface, either after process a or before or after process b.

[0249] There are no particular limitations on the method of applying the adhesive sheet; existing known methods, such as using a laminator, can be employed.

[0250] <Grinding and Single-piece Process>

[0251] The grinding and single-piece process involves grinding the back of the workpiece while the workpiece processing adhesive sheet is fixed to the workpiece using a support device, and then single-pieceing the workpiece into multiple single-piece workpieces starting from the groove or the modified area mentioned above.

[0252] For workpieces with adhesive sheets bonded to them and grooves or modified areas formed, a support device is used to fix the adhesive sheets to one side. There are no particular limitations on the support device; a chuck or worktable, or similar device that draws in and holds the object in place, is preferred.

[0253] Next, the back of the fixed workpiece is ground to break it down into multiple workpiece pieces.

[0254] Regarding back-side grinding, if a groove is formed in the workpiece through process a, the workpiece is ground at least until the grinding surface reaches the bottom of the groove. Through this back-side grinding, the groove becomes a cut through the workpiece, and the workpiece is divided and monolithically processed into individual workpiece monoliths through the cut.

[0255] On the other hand, if a modified region is formed on the workpiece through process b, the grinding surface can reach the modified region, but it can also reach it less strictly. That is, it is sufficient to grind to a position close to the modified region, so that the workpiece is destroyed and monolithized starting from the modified region. For example, after grinding to a position close to the modified region without monolithizing the workpiece, a pick-up tape can be attached to the workpiece, and the semiconductor chip can be monolithized by stretching the pick-up tape.

[0256] After being pieced together, the shape of the pieced workpiece can be square, rectangular, or other slender shapes.

[0257] The thickness of the monolithic workpiece after monolithization is not particularly limited, but is preferably 5~100μm, more preferably 7~70μm, and even more preferably 10~45μm.

[0258] The size of the single-piece workpiece after the process of modularization is not particularly limited, but it is preferred to be less than 50mm. 2 More preferably less than 30mm 2 Further preferred size is less than 10mm 2 .

[0259] <Stripping Process>

[0260] The peeling process is the process of peeling the adhesive sheet from the multiple workpieces after the grinding and slabification processes.

[0261] In cases where the adhesive layer of the adhesive sheet is formed by an energy-curable adhesive, the adhesive sheet is peeled off after the adhesive is cured by irradiating with energy rays to reduce the peeling force of the adhesive layer.

[0262] It should be noted that a pickup tape can also be used when peeling off the adhesive sheet. The pickup tape can be, for example, an adhesive sheet having a substrate and an adhesive layer disposed on one side of the substrate.

[0263] When using a pickup tape, first attach the pickup tape to the back side of the pieced workpiece, aligning its position and orientation for pickup. At this point, it is preferable to also attach the annular frame located on the outer periphery of the pieced workpiece to the pickup tape, and fix the outer periphery of the pickup tape to the annular frame. Next, peel the adhesive sheet from the multiple pieced workpieces fixed to the pickup tape.

[0264] Then, after picking up multiple monolithic workpieces located on the pick-up belt, they can be fixed onto a substrate or the like, thereby manufacturing electronic device devices.

[0265] Example

[0266] The present invention will now be described in more detail based on embodiments, but the invention is not limited to these examples. Methods for measuring and evaluating various physical properties are described below.

[0267] It should be noted that the proportions of each component mentioned below refer to the total proportions of all active ingredients.

[0268] The methods for determining and evaluating various physical properties are described below.

[0269] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)]

[0270] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) were determined using a gel permeation chromatography apparatus (manufactured by Tosoh Corporation, trade name "HLC-8220") under the following conditions and obtained by conversion to standard polystyrene.

[0271] (Measurement conditions)

[0272] • Columns: “TSK guard column HXL-H”, “TSK gel GMHXL (×2)”, “TSK gel G2000HXL” (all manufactured by Tosoh Corporation)

[0273] Column temperature: 40℃

[0274] Elution solvent: tetrahydrofuran

[0275] • Flow rate: 1.0 mL / min

[0276] [Thickness measurement of adhesive sheets, etc.]

[0277] The total thickness of the adhesive sheet, the thickness of each layer, and the thickness of the test piece made from them were measured using a constant pressure thickness gauge (manufactured by TECLOCK Co., Ltd., trade name "PG-02"). At this time, 10 arbitrary points were measured and the average value was calculated.

[0278] It should be noted that the total thickness of the adhesive sheet is the value obtained by measuring the thickness of the adhesive sheet with the release liner and subtracting the thickness of the release liner from its total thickness.

[0279] In addition, the thickness of the buffer layer is obtained by subtracting the thickness of the substrate from the thickness of the substrate with the buffer layer.

[0280] In addition, the thickness of the adhesive layer is obtained by subtracting the thickness of the buffer layer and the substrate from the total thickness of the adhesive sheet.

[0281] [Method for determining the Young's modulus of a buffer layer]

[0282] A monomeric film containing only the buffer layer, prepared using the same method as in the examples and comparative examples, was cut into pieces 15 mm wide and 150 mm long, and stacked to achieve a thickness of 0.1 mm, resulting in a test piece. This test piece was mounted on a precision universal testing machine (manufactured by Shimadzu Corporation, trade name "Autograph AG-IS") with a clamp spacing of 100 mm, and the Young's modulus of the buffer layer was measured according to JIS K7127:1999 at a test speed of 200 mm / min. It should be noted that the measurement was performed at 23°C and 50% RH.

[0283] [Method for determining the Young's modulus of adhesive sheets]

[0284] The adhesive sheet for workpiece processing prepared in the examples and comparative examples was cut into pieces 15 mm wide and 150 mm long. The piece after the release liner was peeled off was used as a test piece. This test piece was mounted on a precision universal testing machine (manufactured by Shimadzu Corporation, trade name "Autograph AG-IS") with a clamp spacing of 100 mm. The Young's modulus of the adhesive sheet was measured according to JIS K 7127:1999 at a test speed of 200 mm / min. It should be noted that the measurement was performed at 23°C and 50% RH.

[0285] [Evaluation of low unpleasant odor]

[0286] The release sheet was peeled off from the adhesive sheet for workpiece processing manufactured in the examples and comparative examples, and a sensory evaluation of unpleasant odor was conducted at room temperature (23°C). The low unpleasant odor of the adhesive sheet was evaluated based on the following criteria.

[0287] A: No unpleasant odor

[0288] C: Has an unpleasant odor

[0289] [Evaluation of grindability: back grinding]

[0290] Using a back-grinding belt laminator (manufactured by Lintec Corporation, trade name "RAD3510F / 12"), the workpiece processing adhesive sheet manufactured in the examples and comparative examples was bonded to a 12-inch diameter, 775μm thick silicon wafer with the adhesive layer as the bonding surface. Next, using a back-grinding apparatus (manufactured by DISCO Corporation, trade name "DGP8761"), the silicon wafer was ground (including dry polishing) with the workpiece processing adhesive sheet fixed in place until a thickness of 30μm was achieved. The appearance of the ground silicon wafer was observed visually, and the grindability during back-grinding was evaluated based on the following criteria.

[0291] A: No silicon wafer damage has been confirmed.

[0292] C: The silicon wafer damage has been confirmed.

[0293] [Evaluation of machinability: Invisible pre-cut machining]

[0294] Using a back-grinding belt laminator (manufactured by Lintec Corporation, trade name "RAD3510F / 12"), the workpiece processing adhesive sheets manufactured in the examples and comparative examples were bonded to a 12-inch diameter, 775μm thick silicon wafer with the adhesive layer as the bonding surface. Next, using a laser saw (manufactured by DISCO Corporation, trade name "DFL7361"), a lattice-shaped modification area was formed inside the silicon wafer. It should be noted that the lattice size was set to 10mm × 10mm.

[0295] Next, the silicon wafer was ground (including dry polishing) using a back-side grinding device (DISCO, trade name "DGP8761") until a thickness of 30 μm was achieved. Starting from the modified region, the silicon wafer was monolithically formed into multiple chips. Then, the workpiece bonding sheet was irradiated with energy rays (ultraviolet light). Next, a dicing tape (Lindecco, trade name "Adwill D-175D") was attached to the side of the multiple chips opposite to the bonding surface of the workpiece bonding sheet, and the workpiece bonding sheet was peeled off from the multiple chips.

[0296] Multiple chips after the adhesive sheet for workpiece processing was removed were observed using a digital microscope. They were classified according to the size of each crack using the following criteria. The number of chips with confirmed cracks was counted, and the grindability in stealth pre-cutting was evaluated based on these criteria. It should be noted that the crack size (μm) is determined by comparing the length (μm) of the crack along the longitudinal direction of the chip with the length (μm) of the crack along the transverse direction of the chip, and taking the larger value.

[0297] (Crack classification based on crack size)

[0298] Large cracks: Cracks exceeding 20 μm in size

[0299] Medium crack: Crack size greater than 10μm and less than 20μm

[0300] Small cracks: Cracks smaller than 10μm

[0301] (Evaluation Criteria)

[0302] A: There are 0 large cracks, fewer than 7 medium cracks, and fewer than 15 small cracks.

[0303] B: 0 large cracks, 8 to 10 medium cracks, and 15 to 15 small cracks; or 0 large cracks, 7 to 16 medium cracks, and 16 to 20 small cracks.

[0304] C: There is one or more large cracks, or eleven or more medium cracks, or twenty-one or more small cracks.

[0305] [Preparation of the adhesive composition]

[0306] Manufacturing Example 1

[0307] An acrylic polymer was obtained by copolymerizing 65 parts by weight of n-butyl acrylate (BA), 20 parts by weight of methyl methacrylate (MMA), and 15 parts by weight of 2-hydroxyethyl acrylate (2HEA). 2-Methacryloxyethyl isocyanate (MOI) was then reacted with the acrylic polymer by adding hydroxyl groups to 80 equivalents of all hydroxyl groups (100 equivalents) of the acrylic polymer to obtain an energy-curable acrylic copolymer (Mw: 500,000).

[0308] To 100 parts by weight of this energy-ray curable acrylic copolymer, 6 parts by weight of a polyfunctional urethane acrylate UV-curable compound (manufactured by Mitsubishi Chemical Corporation, trade name "UT-4332"), 0.375 parts by weight of an isocyanate crosslinking agent (manufactured by Mitsui Chemicals Corporation, trade name "Takenate D-101E"), and 1 part by weight of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide as a photopolymerization initiator were added, and the mixture was diluted with methyl ethyl ketone to prepare an adhesive composition with a solid content of 34% by weight.

[0309] The adhesive composition obtained above was applied to the release surface of the release sheet (manufactured by Lindeco Co., Ltd., trade name "SP-PET381031"), so that the thickness after drying was 20 μm, and then heated and dried to produce a release sheet with an adhesive layer.

[0310] Manufacturing of adhesive sheets for workpiece machining

[0311] Examples 1-7

[0312] (1) Preparation of composition for forming buffer layer

[0313] A thermosetting resin composition for forming a buffer layer was prepared by combining 100 parts by weight of the polyester resin shown in Table 1 as the thermosetting resin, 7.5 parts by weight of the isocyanate crosslinking agent (manufactured by Tosoh Corporation, trade name "CORONATE HL", ethyl acetate diluent, solid content concentration 74-76 by weight), and 0.5 parts by weight of dibutyltin dilaurate (manufactured by Toyochem Corporation, trade name "BXX3778G") as the curing catalyst.

[0314] It should be noted that the details of the polyester resins shown in Table 1 are as follows.

[0315] UR-1400: A polyester urethane resin with two or more hydroxyl groups, manufactured by Toyobo Co., Ltd., trade name, glass transition temperature 83°C, number average molecular weight (Mn) 40000, hydroxyl value 2~3 KOH mg / g, solvent (the solvent contains 50% by mass of methyl ethyl ketone and 50% by mass of toluene), diluent, solids concentration 30% by mass.

[0316] UR-1700: A polyester urethane resin with two or more hydroxyl groups, manufactured by Toyobo Co., Ltd., trade name, glass transition temperature 92°C, number average molecular weight (Mn) 16000, hydroxyl value 19 KOH mg / g, solvent (the content of methyl ethyl ketone in the solvent is 100% by mass), diluent, solids concentration 30% by mass.

[0317] UR-4800: A polyester urethane resin with two or more hydroxyl groups, manufactured by Toyobo Co., Ltd., trade name, glass transition temperature 106℃, number average molecular weight (Mn) 25000, hydroxyl value 4~6, KOH mg / g, solvent (the solvent contains 50% by mass of methyl ethyl ketone and 50% by mass of toluene), diluent, solids concentration 32% by mass.

[0318] (2) Fabrication of adhesive sheets for workpiece machining

[0319] A polyethylene terephthalate film (50 μm thick) was prepared as a substrate, and the thermosetting resin composition obtained above was coated onto one side of the substrate to form a coated film. It should be noted that the coating amount for the thermosetting resin composition was adjusted so that the thickness of the formed buffer layer was as described in Table 1. Next, the coated film was heated at 110°C for 2 minutes to allow the organic solvent to dry while simultaneously carrying out the thermosetting resin composition's thermal curing reaction, resulting in a substrate with a buffer layer having the thickness described in Table 1 formed on one side of the substrate.

[0320] Next, the adhesive layer of the release sheet with adhesive layer obtained in Manufacturing Example 1 is bonded to the surface of the substrate opposite to the buffer layer of the substrate with the buffer layer, and a workpiece processing adhesive sheet having a buffer layer, a substrate and an adhesive layer in sequence is obtained.

[0321] Example 8

[0322] In Example 1, “(2) Fabrication of adhesive sheet for workpiece processing”, the adhesive layer of the release liner with adhesive layer is bonded to the surface of the buffer layer of the substrate with buffer layer, instead of the substrate of the substrate with buffer layer. Otherwise, the adhesive sheet for workpiece processing is obtained in the same manner as in Example 1. That is, the adhesive sheet for workpiece processing obtained in Example 8 is an adhesive sheet for workpiece processing that has a substrate, a buffer layer and an adhesive layer in sequence.

[0323] Comparative Example 1

[0324] (1) Preparation of composition for forming buffer layer

[0325] An energy-curable resin composition for forming a buffer layer was prepared by combining 50 parts by weight of an urethane acrylate oligomer (manufactured by Sartomer, trade name "CN8881") as an energy-curable compound, 50 parts by weight of polyethylene glycol (400) diacrylate, and 2.0 parts by weight of 2-hydroxy-2-methyl-1-phenylpropane-1-one (manufactured by IGM Resins, trade name "Omnirad 1173") as a photopolymerization initiator.

[0326] (2) Fabrication of adhesive sheet

[0327] The energy-curable resin composition obtained above was coated onto the release surface of a release sheet (manufactured by Lintec Corporation, trade name "SP-PET381031") to form a coated film. Next, the coated film was irradiated with ultraviolet light to semi-cur the energy-curable resin composition, forming a 28 μm thick layer of the energy-curable resin composition on the release sheet.

[0328] It should be noted that the aforementioned ultraviolet irradiation was performed using a conveyor belt-type ultraviolet irradiation device (manufactured by EyeGraphics, trade name "ECS-401GX") and a high-pressure mercury lamp (manufactured by EyeGraphics, trade name "H04-L41") at a lamp height of 260mm, an output of 80W / cm, and an illuminance of 70mW / cm. 2 Irradiation dose 30mW / cm 2 It was carried out under irradiation conditions.

[0329] Next, the surface of the layer formed by semi-curing the energy-curable resin composition on the release sheet is bonded to one side of a PET film (manufactured by Mitsubishi Resin Co., Ltd., trade name "PET50 T910 WM19", thickness 50 μm) serving as the substrate. Then, the energy-curable resin composition is completely cured by irradiating it with ultraviolet light from the release sheet side, resulting in a substrate with a buffer layer having a thickness of 28 μm formed on one side of the substrate.

[0330] It should be noted that the above-mentioned ultraviolet irradiation was performed using the aforementioned ultraviolet irradiation device and high-pressure mercury lamp at a lamp height of 210mm, a lamp output of 120W / cm, and an illuminance of 155mW / cm. 2 Irradiation dose 600mW / cm 2 It was carried out under irradiation conditions.

[0331] Next, the adhesive layer of the release sheet with adhesive layer obtained in Manufacturing Example 1 is attached to the side of the substrate opposite to the buffer layer of the substrate with buffer layer, thereby obtaining a workpiece processing adhesive sheet having a buffer layer, a substrate and an adhesive layer in sequence.

[0332] Comparative Example 2

[0333] (1) Preparation of composition for forming buffer layer

[0334] A thermosetting resin composition was prepared as a composition for forming a buffer layer, similar to that in Example 1.

[0335] (2) Fabrication of adhesive sheets for workpiece machining

[0336] The thermosetting resin composition obtained above was coated onto the release surface of a release sheet (manufactured by Lintec Corporation, trade name "SP-PET381031") to form a coated film. It should be noted that the coating amount of the thermosetting resin composition was adjusted so that the thickness of the resulting buffer layer was as described in Table 1. Next, the coated film was heated at 110°C for 2 minutes to allow the organic solvent to dry while simultaneously performing a thermosetting reaction of the thermosetting resin composition, resulting in a release sheet with a buffer layer having the thickness described in Table 1.

[0337] Next, the buffer layer of the release sheet with the buffer layer is bonded to the adhesive layer of the release sheet with the adhesive layer obtained in Manufacturing Example 1, thereby obtaining an adhesive sheet for workpiece processing having a buffer layer and an adhesive layer in sequence.

[0338] The evaluation results of the adhesive sheets obtained in each embodiment and comparative example are shown in Table 1.

[0339]

[0340] As shown in Table 1, the adhesive sheets for workpiece processing in Examples 1-8 of this embodiment exhibit excellent low odor and machinability. On the other hand, the adhesive sheet for workpiece processing in Comparative Example 1, which uses an energy-curable resin composition to form a buffer layer, has poor low odor. Furthermore, the adhesive sheet for workpiece processing in Comparative Example 2, which does not contain a substrate, has poor machinability.

Claims

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

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

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

4. The adhesive sheet for workpiece processing according to claim 2 or 3, wherein, The polyester resin is a polyester resin having two or more hydroxyl groups, and the thermosetting resin composition further contains a polyisocyanate compound.

5. The adhesive sheet for workpiece machining according to any one of claims 1 to 3, wherein, The buffer layer is provided on one side of the substrate, and the adhesive layer is provided on the other side of the substrate.

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

7. The adhesive sheet for workpiece machining according to any one of claims 1 to 3, wherein, The workpiece has grooves on its surface or modified areas inside. The adhesive sheet for workpiece processing is used to: grind the back side of the workpiece while the adhesive sheet for workpiece processing is fixed to the surface of the workpiece, and to divide the workpiece into multiple workpiece monoliths starting from the groove or the modified area.

8. A method for manufacturing an adhesive sheet for workpiece processing, comprising the method for manufacturing an adhesive sheet for workpiece processing according to any one of claims 1 to 3, the method comprising: The process of curing the thermosetting resin composition by heating it.

9. A method for manufacturing an electronic device, the method comprising: The process of attaching the adhesive sheet for workpiece processing according to any one of claims 1 to 3 to the surface of the workpiece with the adhesive layer as the adhesive surface; as well as The process of grinding the back side of the workpiece while the adhesive sheet for workpiece processing is fixed to the workpiece.

10. A method for manufacturing an electronic device, the method comprising: The process of forming a predetermined dividing line is either process a, which is forming a groove on the surface of a workpiece, or process b, which forms a modified region inside the workpiece from the surface or back of the workpiece. In the sheet bonding process, after step a, or before or after step b, the adhesive sheet for workpiece processing according to any one of claims 1 to 3 is bonded to the surface of the workpiece with the adhesive layer as the bonding surface; and The grinding and modularization process involves grinding the back of the workpiece while the adhesive sheet for workpiece processing is fixed to the workpiece, and modularizing the workpiece into multiple workpiece modular pieces starting from the groove or the modified area.

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