Adhesive tape for wafer processing

Abstract

Even when used in the wafer processing step using a support member, even after dissolving the adhesive that adhered the support member to the wafer using a solvent to peel off the support member or cleaning the adhesive remaining on the wafer, it is possible to appropriately hold the wafer and prevent a decrease in yield due to wafer contamination. Provided is an adhesive tape for wafer processing. 【Solution means】The adhesive tape for wafer processing of the present invention is an adhesive tape for wafer processing formed by laminating at least a base film, a first adhesive layer, and a second adhesive layer in this order, wherein the first adhesive layer is formed of an adhesive composition containing an acrylic polymer or a polyester polymer as a base polymer, and the glass transition temperature of the base polymer is -20°C or higher.

Description

Technical Field

[0001] The present invention relates to an adhesive tape for wafer processing used for dicing a wafer. More specifically, it relates to an adhesive tape for wafer processing used in a wafer processing method including a wafer cleaning step using a solvent.

Background Art

[0002] When thinning the back surface of a wafer on which a wiring pattern is formed, in order to protect the pattern surface of the wafer and fix the wafer itself, after attaching a protective tape to the pattern surface, thinning processes such as polishing and grinding are generally performed on the back surface. As such a protective tape, one in which an acrylic adhesive or the like is applied on a base material made of a plastic film is generally used. However, in recent years, due to the thinning and miniaturization of IC cards and mobile phones, the thickness of chips has been required to be at the level of 50 μm or less. In the process using a conventional protective tape, the wafer cannot be supported only by the protective tape, and warping of the wafer after grinding, bending when storing the wafer in a wafer cassette, etc. make it difficult to handle the wafer and difficult to automate handling and conveyance.

[0003] In response to this problem, a method has been proposed in which a glass substrate, a ceramic substrate, a silicon wafer substrate, etc. are bonded to a wafer via an adhesive to impart supportability to the wafer (see, for example, Patent Document 1). By using a support member such as a glass substrate, a ceramic substrate, or a silicon wafer substrate in this way, the handleability of the wafer is greatly improved and automation of conveyance becomes possible. In addition, the support member can also be used to support the wafer while the wafer is subjected to the back surface wiring and bump formation processes.

[0004] When handling a wafer using a support member, a step of peeling the support member from the wafer is required. The peeling of the support member is generally performed by dissolving an adhesive using a solvent and then cleaning. In addition to the above method, to peel the wafer from the support member, there are also methods such as heating to soften the adhesive and sliding the support member to peel it, or decomposing the adhesive by laser light irradiation to peel the support member. Even when these methods are used, adhesives or their decomposition products may remain on the wafer surface after peeling the support member. Therefore, to remove these residues, the wafer is immersed in an organic solvent to clean the wafer, or the wafer is rotated while spraying an organic solvent onto the wafer to clean the wafer.

[0005] Thereafter, the wafer is transferred to a dicing process and cut into individual chips. In the dicing process, generally, an adhesive tape for wafer processing with an adhesive layer laminated on a base film is used (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] Incidentally, as described above, when the thickness of the wafer is 50 μm or less, handling the wafer alone becomes extremely difficult due to warping of the wafer after grinding or bending when storing the wafer in a wafer cassette. Therefore, prior to peeling the support member after back grinding and polishing of the wafer, it is common practice to attach a wafer processing adhesive tape to the ground surface of the wafer and support and fix it to a ring frame. Accordingly, dissolution and cleaning with a solvent of the adhesive during peeling of the support member are performed with the wafer attached to the wafer processing adhesive tape, and high solvent resistance is required for the wafer processing adhesive tape.

[0008] However, with a normal wafer processing adhesive tape such as the one described in Patent Document 2, the solvent resistance is insufficient, the adhesive strength of the adhesive layer of the wafer processing adhesive tape decreases, and there is a problem that the wafer cannot be sufficiently held. There is also a problem that the adhesive layer of the wafer processing adhesive tape dissolves in a solvent, contaminates the wafer, and reduces the yield.

[0009] Therefore, an object of the present invention is to provide a wafer processing adhesive tape that can appropriately hold a wafer and prevent a decrease in yield due to wafer contamination even when used in a wafer processing step using a support member, after dissolving the adhesive that bonded the support member to the wafer using a solvent to peel the support member or wash the adhesive remaining on the wafer.

Means for Solving the Problems

[0010] As a result of intensive studies to achieve the above object, the present inventors have found that the glass transition temperature of the base polymer of the adhesive layer is related to solvent resistance. The present invention has been made based on this finding.

[0011] That is, the adhesive tape for wafer processing according to the invention of the present application is an adhesive tape for wafer processing formed by laminating a base film, a first adhesive layer, and a second adhesive layer in this order, wherein the first adhesive layer is formed of an adhesive composition containing an acrylic polymer or a polyester polymer as a base polymer, and the glass transition temperature of the base polymer is -20°C or higher.

[0012] Preferably, in the above adhesive tape for wafer processing, the base film is made of a polyolefin resin.

[0013] Also preferably, in the above adhesive tape for wafer processing, the thickness of the base film is 70 to 350 μm.

[0014] Also preferably, in the above adhesive tape for wafer processing, the amount of residual solvent after dropping 1 ml of p-menthane on the surface of the second adhesive layer and allowing it to stand for 30 minutes is 1% m / m or less.

[0015] Also preferably, in the above adhesive tape for wafer processing, the storage elastic modulus of the first adhesive layer is higher than that of the second adhesive layer.

[0016] Also preferably, the above adhesive tape for wafer processing is used in a wafer processing method including a step of cleaning the wafer with a solvent.

Advantages of the Invention

[0017] According to the present invention, even when used in a wafer processing step using a support member, the adhesive that adhered the support member to the wafer is dissolved using a solvent, the support member is peeled off, or after washing the adhesive remaining on the wafer, the wafer can be properly held and a decrease in yield due to wafer contamination can be prevented.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail.

[0019] The pressure-sensitive adhesive tape for wafer processing according to an embodiment of the present invention has at least a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer laminated in this order on at least one side of a base film.

[0020] Note that the base film, the first pressure-sensitive adhesive layer, and the second pressure-sensitive adhesive layer are preferably cut (pre-cut) into a shape corresponding to a ring frame used when singulating a wafer. Further, the pressure-sensitive adhesive tape for wafer processing of the present invention may be in a form cut for each wafer, or may be in a form in which a plurality of long separators cut for each wafer are wound in a roll shape.

[0021] Hereinafter, each component of the pressure-sensitive adhesive tape for wafer processing of the present embodiment will be described in detail.

[0022] (Base film) Examples of the resin constituting the base film include polypropylene, high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ethylene-propylene copolymer, propylene copolymer, ethylene-propylene-diene copolymer vulcanizate, polybutene, polybutadiene, polymethylpentene, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid methyl copolymer, ethylene-(meth)acrylic acid ethyl copolymer, ethylene-(meth)acrylic acid butyl copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl chloride-vinyl acetate copolymer, polyurethane, polyamide, ionomer, nitrile rubber, butyl rubber, styrene isoprene rubber, styrene butadiene rubber, natural rubber and its water-added or modified products, etc. may be used.

[0023] Among these, since the base film exhibits excellent stretchability during expansion, it is preferably made of a polyolefin resin. Examples of the polyolefin resin include homopolymers or copolymers of α-olefins such as polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, poly-4-methylpentene-1, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-acrylic acid copolymer, ionomer, and mixtures thereof.

[0024] In particular, in the case of a base film using an ionomer, uniform physical properties can be obtained with respect to the feeding direction and the width direction of the base film. Therefore, when expansion is performed, the chip intervals of the individualized chips can be made uniform.

[0025] Note that the base film is not limited to a single layer, and may have a multi-layer structure in which two or more resins are laminated, or one type of resin may be laminated in two or more layers. Lamination of one type of resin is preferable from the viewpoint that each characteristic is more enhanced and expressed, and lamination of two or more types of resins is preferable in that each defect is compensated.

[0026] As a method for manufacturing a multi-layer base film, conventionally known extrusion methods, lamination methods, etc. can be used. When using the lamination method, an adhesive may be interposed between the layers. As the adhesive, conventionally known adhesives can be used.

[0027] The thickness of the base film is preferably 70 to 350 μm. More preferably, it is 250 to 300 μm. If it is 350 μm or more, there is a possibility that the chip cannot be picked up from the adhesive tape for wafer processing, and if it is thinner than 70 μm, there is a possibility that the adhesive tape for wafer processing may be torn during expansion.

[0028] In order to improve the adhesion, the surface of the base film in contact with the first adhesive layer may be subjected to corona treatment or treatment with a primer or the like.

[0029] (First adhesive layer) The adhesive composition for forming the first adhesive layer may contain one or more of various rubber-like polymers such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine polymers known in the field of adhesives, but contains at least an acrylic polymer or a polyester polymer as a base polymer.

[0030] The "acrylic polymer" refers to a polymer containing monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule as a monomer unit constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an "acrylic monomer". Therefore, the acrylic polymer in this specification is defined as a polymer containing monomer units derived from acrylic monomers. As a typical example of the acrylic polymer, an acrylic polymer in which the proportion of acrylic monomers among all monomer components used for the synthesis of the acrylic polymer is more than 50% by weight can be mentioned. In addition, "(meth)acryloyl" means comprehensively referring to acryloyl and methacryloyl. Similarly, "(meth)acrylate" means comprehensively referring to acrylate and methacrylate, and "(meth)acrylic" means comprehensively referring to acrylic and methacrylic, respectively.

[0031] The "polyester polymer" refers to a polymer obtained by polycondensation of a dicarboxylic acid and a diol and having repeating units containing an ester bond in the main chain.

[0032] The base polymer constituting the first adhesive has a glass transition temperature of -20°C or higher. Here, the glass transition temperature refers to the glass transition temperature measured by DSC (Differential Scanning Calorimeter) at a heating rate of 0.1°C / min. If the glass transition temperature is -20°C or higher, the solvent resistance is sufficient. When the support member is peeled from the wafer and the adhesive is dissolved and washed with a solvent, wrinkles occur in the base film, stress is applied to the adhesive layer, and it is possible to prevent the adhesive force of the adhesive layer from decreasing, and the wafer can be sufficiently held. Also, even if the second adhesive layer is dissolved by a solvent, since the first adhesive layer holds the second adhesive layer, it is possible to prevent the second adhesive layer from falling off and contaminating the wafer, resulting in a decrease in yield. The glass transition temperature of the base polymer constituting the adhesive is more preferably more than -15°C and 1°C or less, and even more preferably more than -10°C and 1°C or less.

[0033] The first adhesive layer is preferably a radiation-curable type that cures by irradiation with radiation. As the adhesive composition constituting the radiation-curable first adhesive layer, a polymer constituting the adhesive and a radiation-polymerizable compound can be used in combination, or a polymer in which a functional group (preferably an ethylenically unsaturated group) polymerizable by radiation is incorporated into the polymer constituting the adhesive can be used. In order to promote polymerization by radiation, it is preferable to contain a photoinitiator. It is also preferable to contain a crosslinking agent. By incorporating a monomer having a functional group capable of reacting with the crosslinking agent into the polymer constituting the adhesive, the film hardness and gel fraction can be adjusted. Furthermore, additives and additives other than the above can be contained as necessary. This will be described in more detail below.

[0034] Examples of the acrylic polymer include an acrylic polymer obtained by using, as a monomer component, one or more of (meth)acrylic acid alkyl esters (for example, alkyl esters having 1 to 30 carbon atoms in the alkyl group, particularly linear or branched alkyl esters having 4 to 18 carbon atoms, such as methyl ester, ethyl ester, propyl ester, isopropyl ester, butyl ester, isobutyl ester, s-butyl ester, t-butyl ester, pentyl ester, isopentyl ester, hexyl ester, heptyl ester, octyl ester, 2-ethylhexyl ester, isooctyl ester, nonyl ester, decyl ester, isodecyl ester, undecyl ester, dodecyl ester, tridecyl ester, tetradecyl ester, hexadecyl ester, octadecyl ester, eicosyl ester, etc.) and (meth)acrylic acid cycloalkyl esters (for example, cyclopentyl ester, cyclohexyl ester, etc.). The (meth)acrylic acid ester means an acrylic acid ester and / or a methacrylic acid ester, and "(meth)" in the present invention has the same meaning in all cases.

[0035] The acrylic polymer may, if necessary, contain units corresponding to other monomer components copolymerizable with the alkyl (meth)acrylate or cycloalkyl ester for the purpose of modifying cohesion, heat resistance, etc. Examples of such monomer components include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid; acid anhydride monomers such as maleic anhydride, itaconic anhydride; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; sulfonic acid group-containing monomers such as styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid; phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate; acrylamide, acrylonitrile, etc. These copolymerizable monomer components can be used singly or in combination of two or more. The amount of these copolymerizable monomers used is preferably 40% by weight or less of the total monomer components.

[0036] Furthermore, since the acrylic polymer is crosslinked, a polyfunctional monomer or the like can also be included as a monomer component for copolymerization as needed. Examples of such polyfunctional monomers include hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, urethane (meth)acrylate, and the like. These polyfunctional monomers can also be used alone or in combination of two or more. From the viewpoint of adhesive properties and the like, the amount of the polyfunctional monomer used is preferably 30% by weight or less of the total monomer components.

[0037] The acrylic polymer can be prepared, for example, by applying an appropriate method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, or a suspension polymerization method to a mixture of one or more component monomers.

[0038] In addition, in order to control the crosslink density of the first adhesive layer, for example, an appropriate external crosslinking agent such as a polyfunctional isocyanate compound, a polyfunctional epoxy compound, a melamine compound, a metal salt compound, a metal chelate compound, an amino resin compound, or a peroxide is used for crosslinking treatment, or a low-molecular compound having two or more carbon-carbon double bonds is mixed and crosslinked by irradiation with radiation or the like. An appropriate method can be adopted. When using an external crosslinking agent, its amount used is appropriately determined by the balance with the base polymer to be crosslinked and further by the use purpose as an adhesive. Generally, it is preferably blended in an amount of about 20 parts by weight or less, more preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the base polymer. In addition, from the viewpoint of preventing deterioration and the like, additives such as various tackifiers and antioxidants may be used as needed in addition to the above components in the adhesive.

[0039] As the adhesive that constitutes the first adhesive layer, a radiation-curable adhesive is preferable. Examples of the radiation-curable adhesive include an addition-type radiation-curable adhesive in which a radiation-curable monomer component or a radiation-curable oligomer component is blended with the aforementioned adhesive.

[0040] Examples of the radiation-curable monomer component to be blended include, for example, urethane (meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxy penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, and the like. These monomer components can be used alone or in combination of two or more.

[0041] In addition, examples of the radiation-curable oligomer component include various oligomers such as urethane-based, polyether-based, polyester-based, polycarbonate-based, and polybutadiene-based oligomers, and those having a molecular weight in the range of about 100 to 30,000 are suitable. The blending amounts of the radiation-curable monomer component and the oligomer component can be appropriately determined according to the type of the first adhesive layer so as to be an amount that can reduce the adhesive strength of the first adhesive layer. Generally, it is, for example, 5 parts by weight to 500 parts by weight, preferably about 70 parts by weight to 150 parts by weight, based on 100 parts by weight of a base polymer such as an acrylic polymer that constitutes the adhesive.

[0042] In addition, examples of the radiation-curable adhesive include, in addition to the addition-type radiation-curable adhesive, an inherent-type radiation-curable adhesive in which a radiation-curable group is introduced into the polymer side chain, main chain, or main chain end as a base polymer. The inherent-type radiation-curable adhesive is preferable because it does not need to contain, or contains little, an oligomer component or the like that is a low-molecular component, and thus can form a first adhesive layer having a stable layer structure without the oligomer component or the like moving in the adhesive over time.

[0043] As the base polymer into which a radiation-curable group is introduced, those having a carbon-carbon double bond and adhesiveness can be used without particular limitation. As such a base polymer, those having an acrylic polymer as a basic skeleton are preferable. Examples of the basic skeleton of the acrylic polymer include the acrylic polymers exemplified above.

[0044] The method for introducing a radiation-curable group into an acrylic polymer is not particularly limited, and various methods can be adopted. However, it is easy in terms of molecular design to introduce the radiation-curable group into the polymer side chain. For example, after copolymerizing a monomer having a functional group with an acrylic polymer in advance, a compound having a functional group capable of reacting with this functional group and a carbon-carbon double bond is subjected to a condensation or addition reaction while maintaining the radiation curability of the carbon-carbon double bond.

[0045] Examples of combinations of these functional groups include a carboxylic acid group and an epoxy group, a carboxylic acid group and an aziridyl group, a hydroxyl group and an isocyanate group, etc. Among these combinations of functional groups, a combination of a hydroxyl group and an isocyanate group is preferable because of the ease of reaction tracking. Further, as long as the combination of these functional groups is such that an acrylic polymer having the carbon-carbon double bond is generated, the functional group may be on either side of the acrylic polymer and the compound, but in the above-mentioned preferable combination, it is preferable that the acrylic polymer has a hydroxyl group and the compound has an isocyanate group. In this case, examples of the isocyanate compound having a carbon-carbon double bond include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, etc. Further, as the acrylic polymer, those obtained by copolymerizing the above-exemplified hydroxyl group-containing monomers, ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether are used.

[0046] For the internal radiation-curable pressure-sensitive adhesive, the base polymer having the carbon-carbon double bond (especially an acrylic polymer) can be used alone, but a photopolymerizable compound such as the radiation-curable monomer component or oligomer component can also be blended to such an extent that the properties are not deteriorated. The blending amount of the photopolymerizable compound is usually within the range of 30 parts by weight or less, preferably within the range of 0 to 10 parts by weight, based on 100 parts by weight of the base polymer.

[0047] It is preferable that the radiation-curable pressure-sensitive adhesive contains a photoinitiator when it is cured by ultraviolet rays or the like.

[0048] Among the above acrylic polymers, a (meth)acrylate copolymer in which a radiation-curable group is introduced into the side chain, more specifically, an acrylate represented by CH2=CHCOOR (wherein R is an alkyl group having 4 to 18 carbon atoms), a hydroxyl group-containing monomer, and an isocyanate compound having a radical-reactive carbon-carbon double bond in the molecule is preferably used.

[0049] The amount of the carbon-carbon double bond is preferably 1.2 to 1.8 meq / g. The amount of the double bond can be quantitatively measured by the weight increase method by the bromine addition reaction in a vacuum and in the dark for about 10 g of the dried pressure-sensitive adhesive.

[0050] The above (meth)acrylate copolymer may contain units corresponding to other monomer components as necessary.

[0051] Examples of the double bond-containing isocyanate compound include methacryloyl isocyanate, acryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, and the like. The double bond-containing isocyanate compound can be used alone or in combination of two or more.

[0052] In addition, for radiation-curable adhesives, in order to adjust the adhesive strength before radiation irradiation and the adhesive strength after radiation irradiation, an external crosslinking agent can also be appropriately used. Specific means of the external crosslinking method include a method of adding and reacting a so-called crosslinking agent such as a polyisocyanate compound, an epoxy compound, an aziridine compound, or a melamine-based crosslinking agent. When using an external crosslinking agent, its usage amount is appropriately determined by the balance with the base polymer to be crosslinked and further by the usage purpose as an adhesive. Generally, the usage amount of the external crosslinking agent is 20 parts by weight or less (preferably 0.1 part by weight to 10 parts by weight) based on 100 parts by weight of the base polymer. Further, if necessary, in addition to the above components, various conventionally known additives such as tackifiers, antioxidants, and foaming agents may be blended in the radiation-curable adhesive.

[0053] The polyester used in the polyester-based polymer is a polyester obtained by polycondensing a carboxylic acid component having two or more functional groups and a diol component, and it is preferable that the weight average molecular weight of the polyester is 8,500 to 50,000. Further, the polyester preferably contains at least a carboxylic acid component having two or more functional groups, and the carboxylic acid component is preferably a dicarboxylic acid component having two carboxyl groups in the molecule.

[0054] The dicarboxylic acid is not particularly limited, and examples thereof include sebacic acid derived from castor oil, dimer acids derived from oleic acid, erucic acid, etc. Other examples include aliphatic and alicyclic dicarboxylic acids such as adipic acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, dodecenyl succinic anhydride, fumaric acid, succinic acid, dodecanedioic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, maleic acid, maleic anhydride, itaconic acid, citraconic acid, etc., and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 2,2'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, etc. Among them, dimer acid is particularly preferred because it has a low glass transition temperature, enables the design of a flexible adhesive, can exhibit good wetting properties, and is a preferred embodiment. In addition, dimer acid is a non-petroleum-derived material (plant-derived raw material), so it can be environmentally friendly and useful. These can be used alone or in combination of two or more.

[0055] Further, the polyester contains a diol component, and as the diol component, it is preferably contained at least one having two hydroxyl groups in the molecule. Among them, it is preferable to use aliphatic diols, polyether glycols, etc.

[0056] As the aliphatic diol, an aliphatic diol having an alkylene group with 3 to 10 carbon atoms is particularly preferred. The aliphatic diol having an alkylene group with 3 to 10 carbon atoms is not particularly limited, but specifically, 1,2-propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,5-pentanediol, 2-ethyl-2-butylpropanediol, 1,9-nonanediol, 2-methyloctanediol, 1,10-decanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol and other aliphatic glycols can be mentioned. These can be used alone or in combination of two or more.

[0057] Also, as the polyether glycol, although not particularly limited, it is preferable to use a polyether glycol having hydroxyl groups at both ends. As the polyether glycol having hydroxyl groups at both ends, the number average molecular weight (Mn) of the polyether glycol is not particularly limited. Specifically, polyalkylene ether glycols such as polytetramethylene ether glycol, polytrimethylene ether glycol, etc., a copolymer polyether polyol of 3-methyltetrahydrofuran and tetrahydrofuran in an amount of 1 to 20 mol% (for example, "PTG-L1000", "PTG-L2000", "PTG-L3500", etc. manufactured by Hodogaya Chemical Co., Ltd.), or a copolymer polyether glycol of neopentyl glycol and tetrahydrofuran are preferable. These can be used alone or in combination of two or more.

[0058] The polyester can be obtained by polycondensing a carboxylic acid component and a diol component. The molar ratio (OH / COOH) of the carboxyl group of the carboxylic acid component to the hydroxyl group of the diol component is preferably 1 or more, more preferably 1.02 to 3, still more preferably 1.04 to 2.60, and particularly preferably 1.06 to 2.40. When the molar ratio is less than 1, the terminal of the polyester (polymer) after polymerization becomes a carboxyl group, and there is a risk that crosslinking with a crosslinking agent (for example, an isocyanate-based crosslinking agent) cannot be performed promptly, and there is also a risk that the holding force (cohesive force) of the adhesive layer cannot be sufficiently obtained.

[0059] In addition, it is also possible to polymerize or add other components other than the carboxylic acid component and the diol component after polymerization.

[0060] The method for synthesizing the polyester is not particularly limited, and a known polymerization method can be used. The polymerization (condensation polymerization) reaction of the carboxylic acid component and the diol component may be carried out using a solvent or without a solvent under reduced pressure, and a conventionally known method can be used.

[0061] When a polyester-based polymer is used as the base polymer, the adhesive composition of the first adhesive layer preferably contains a fatty acid ester having no functional group and a molecular weight (molar molecular weight: g / mol) of 200 to 700 together with the polyester-based polymer. Examples of the fatty acid ester include isopropyl myristate, isopropyl palmitate, methyl linoleate, and dibasic acid esters such as adipic acid ester, sebacic acid ester, and phthalic acid ester. These can be used alone or in combination of two or more. The blending amount of the fatty acid ester is 10 to 150 parts by weight, preferably 20 to 150 parts by weight, more preferably 30 to 140 parts by weight, and still more preferably 40 to 130 parts by weight based on 100 parts by weight of the polyester-based polymer.

[0062] In addition, the pressure-sensitive adhesive composition contains a crosslinking agent together with the polyester-based polymer. The crosslinking agent is not particularly limited, and conventionally known ones can be used. For example, isocyanate-based crosslinking agents such as polyvalent isocyanurates and polyfunctional isocyanate compounds, polyfunctional melamine compounds, polyfunctional epoxy compounds, polyfunctional oxazoline compounds, polyfunctional aziridine compounds, metal chelate compounds, etc. can be used. These can be used alone or in combination of two or more.

[0063] In particular, it is preferable to use an isocyanate-based crosslinking agent such as conventionally known polyvalent isocyanurates and polyfunctional isocyanates. Examples of the polyvalent isocyanurate include polyisocyanurate bodies of hexamethylene diisocyanate. The polyfunctional isocyanate compound is preferably a compound having at least two or more isocyanate groups in the molecule, more preferably three or more, and is not particularly limited. Specifically, aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, etc. can be mentioned.

[0064] The thickness of the first pressure-sensitive adhesive layer is preferably 5 μm or more and 70 μm or less, more preferably 5 μm or more and 30 μm or less, and still more preferably 5 μm or more and 15 μm or less. If the pressure-sensitive adhesive layer is thinner than 5 μm, there is a risk that sufficient adhesive force cannot be exhibited. On the other hand, if the pressure-sensitive adhesive layer is thicker than 70 μm, the force during expansion may not be sufficiently transmitted to the wafer, and there is a risk that the wafer cannot be divided into chips.

[0065] The method for forming the first pressure-sensitive adhesive layer on the base film is not particularly limited. For example, the above pressure-sensitive adhesive composition is applied on the base film by a commonly used coating method and dried to form it. Alternatively, it can be produced by transferring the pressure-sensitive adhesive layer applied on the separator to the base film by laminating it with the base film.

[0066] (Second pressure-sensitive adhesive layer) The pressure-sensitive adhesive composition for forming the second pressure-sensitive adhesive layer may contain, as a base polymer, one or more of various rubber-like polymers such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine polymers, which are known in the field of pressure-sensitive adhesives.

[0067] The second pressure-sensitive adhesive layer is preferably a radiation-curable type that cures by irradiation with radiation. As the pressure-sensitive adhesive composition constituting the radiation-curable second pressure-sensitive adhesive layer, a polymer constituting the pressure-sensitive adhesive and a radiation-polymerizable compound can be used in combination, or a polymer in which a functional group (preferably an ethylenically unsaturated group) that polymerizes with radiation is incorporated into the polymer constituting the pressure-sensitive adhesive can be used. In order to promote polymerization by radiation, it is preferably contained a photoinitiator. It is also preferable to contain a crosslinking agent. By incorporating a monomer having a functional group capable of reacting with the crosslinking agent into the polymer constituting the pressure-sensitive adhesive, the film hardness and gel fraction can be adjusted. Further, if necessary, additives and additives other than the above can also be contained. This will be described in more detail below.

[0068] Examples of the acrylic polymer include (meth)acrylic acid alkyl esters (for example, methyl ester, ethyl ester, propyl ester, isopropyl ester, butyl ester, isobutyl ester, s-butyl ester, t-butyl ester, pentyl ester, isopentyl ester, hexyl ester, heptyl ester, octyl ester, 2-ethylhexyl ester, isooctyl ester, nonyl ester, decyl ester, isodecyl ester, undecyl ester, dodecyl ester, tridecyl ester Examples include acrylic polymers using, as monomer components, one or more of (meth)acrylic acid alkyl esters having 1 to 30 carbon atoms in the alkyl group, particularly linear or branched alkyl esters having 4 to 18 carbon atoms such as butyl ester, tetradecyl ester, hexadecyl ester, octadecyl ester, eicosyl ester, etc., and (meth)acrylic acid cycloalkyl esters (e.g., cyclopentyl ester, cyclohexyl ester, etc.). Here, (meth)acrylic acid ester means acrylic acid ester and / or methacrylic acid ester, and "(meth)" in the present invention has the same meaning throughout.

[0069] For the purpose of modifying cohesion, heat resistance, etc., the acrylic polymer may, if necessary, contain units corresponding to other monomer components copolymerizable with the above (meth)acrylic acid alkyl ester or cycloalkyl ester. Examples of such monomer components include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, etc.; acid anhydride monomers such as maleic anhydride, itaconic anhydride, etc.; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl (meth)acrylate, etc.; sulfonic acid group-containing monomers such as styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, etc.; phosphate group-containing monomers such as 2-hydroxyethylacryloyl phosphate, etc.; acrylamide, acrylonitrile, etc. These copolymerizable monomer components can be used singly or in combination of two or more. The usage amount of these copolymerizable monomers is preferably 40% by weight or less of the total monomer components.

[0070] Furthermore, since the acrylic polymer is crosslinked, a polyfunctional monomer or the like can also be included as a monomer component for copolymerization as needed. Examples of such polyfunctional monomers include hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, urethane (meth)acrylate, and the like. These polyfunctional monomers can be used alone or in combination of two or more. From the viewpoint of adhesive properties and the like, the amount of the polyfunctional monomer used is preferably 30% by weight or less of the total monomer components.

[0071] The acrylic polymer can be prepared, for example, by applying an appropriate method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, or a suspension polymerization method to a mixture of one or more component monomers.

[0072] In addition, in order to control the crosslink density of the second adhesive layer, for example, an appropriate external crosslinking agent such as a polyfunctional isocyanate compound, a polyfunctional epoxy compound, a melamine compound, a metal salt compound, a metal chelate compound, an amino resin compound, or a peroxide is used for crosslinking treatment, or a low-molecular compound having two or more carbon-carbon double bonds is mixed and crosslinked by irradiation with radiation or the like. When using an external crosslinking agent, its amount used is appropriately determined by the balance with the base polymer to be crosslinked and further by the intended use as an adhesive. Generally, it is preferably blended in an amount of about 20 parts by weight or less, more preferably 0.1 to 20 parts by weight, per 100 parts by weight of the base polymer. In addition, from the viewpoint of preventing deterioration and the like, additives such as various tackifiers and antioxidants may be used as needed in addition to the above components in the adhesive.

[0073] As the adhesive constituting the second adhesive layer, a radiation-curable adhesive is preferable. Examples of the radiation-curable adhesive include an addition-type radiation-curable adhesive in which a radiation-curable monomer component or a radiation-curable oligomer component is blended with the aforementioned adhesive.

[0074] Examples of the radiation-curable monomer component to be blended include, for example, urethane (meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxy penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, and the like. These monomer components can be used alone or in combination of two or more.

[0075] Also, examples of the radiation-curable oligomer component include various oligomers such as urethane-based, polyether-based, polyester-based, polycarbonate-based, and polybutadiene-based oligomers, and those having a molecular weight in the range of about 100 to 30,000 are suitable. The blending amounts of the radiation-curable monomer component and the oligomer component can be appropriately determined according to the type of the first adhesive layer so that the adhesive strength of the first adhesive layer can be reduced. Generally, it is, for example, 5 to 500 parts by weight, preferably about 70 to 150 parts by weight, based on 100 parts by weight of a base polymer such as an acrylic polymer constituting the adhesive.

[0076] In addition to the addition-type radiation-curable adhesive, examples of the radiation-curable adhesive also include an inherent-type radiation-curable adhesive in which a radiation-curable group is introduced into the polymer side chain, main chain, or main chain end as the base polymer. The inherent-type radiation-curable adhesive is preferable because it does not need to contain or contains little oligomer component or the like which is a low molecular weight component, and thus can form a first adhesive layer having a stable layer structure without the oligomer component or the like moving in the adhesive over time.

[0077] As the base polymer into which a radiation-curable group is introduced, those having a carbon-carbon double bond and adhesiveness can be used without particular limitation. As such a base polymer, those having an acrylic polymer as a basic skeleton are preferable. Examples of the basic skeleton of the acrylic polymer include the acrylic polymers exemplified above.

[0078] The method for introducing a radiation-curable group into an acrylic polymer is not particularly limited, and various methods can be adopted. However, it is easy in terms of molecular design to introduce the radiation-curable group into the polymer side chain. For example, after copolymerizing a monomer having a functional group with an acrylic polymer in advance, a compound having a functional group capable of reacting with this functional group and a carbon-carbon double bond is subjected to a condensation or addition reaction while maintaining the radiation curability of the carbon-carbon double bond.

[0079] Examples of combinations of these functional groups include a carboxylic acid group and an epoxy group, a carboxylic acid group and an aziridyl group, a hydroxyl group and an isocyanate group, etc. Among these combinations of functional groups, a combination of a hydroxyl group and an isocyanate group is preferable because of the ease of reaction tracking. Also, as long as the combination of these functional groups is such that an acrylic polymer having the carbon-carbon double bond is formed, the functional groups may be on either side of the acrylic polymer and the compound. In the above-preferred combination, it is preferable that the acrylic polymer has a hydroxyl group and the compound has an isocyanate group. In this case, examples of the isocyanate compound having a carbon-carbon double bond include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, etc. Also, as the acrylic polymer, those copolymerized with the above-exemplified hydroxyl group-containing monomers, ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether are used.

[0080] The internal radiation-curable pressure-sensitive adhesive can use the base polymer having the carbon-carbon double bond (especially an acrylic polymer) alone, but it is also possible to blend a photopolymerizable compound such as the radiation-curable monomer component or oligomer component to such an extent that the properties are not deteriorated. The blending amount of the photopolymerizable compound is usually within the range of 30 parts by weight or less, preferably within the range of 0 to 10 parts by weight, based on 100 parts by weight of the base polymer.

[0081] It is preferable that the radiation-curable pressure-sensitive adhesive contains a photoinitiator when it is cured by ultraviolet rays or the like.

[0082] Among the above-mentioned acrylic polymers, in particular, a (meth)acrylate copolymer in which a radiation-curable group is introduced into the side chain, more specifically, an acrylate represented by CH2=CHCOOR (wherein R is an alkyl group having 4 to 18 carbon atoms), a hydroxyl group-containing monomer, and an isocyanate compound having a radical-reactive carbon-carbon double bond in the molecule is preferably used.

[0083] The amount of the carbon-carbon double bond is preferably 1.2 to 1.8 meq / g. Regarding the amount of the double bond, the amount of the carbon-carbon double bond contained in about 10 g of the dried adhesive can be quantitatively measured by the weight addition method by the bromine addition reaction in a vacuum and in the dark.

[0084] The above (meth)acrylate copolymer may contain units corresponding to other monomer components, if necessary.

[0085] Examples of the double bond-containing isocyanate compound include methacryloyl isocyanate, acryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, and the like. The double bond-containing isocyanate compound can be used alone or in combination of two or more.

[0086] In addition, for radiation-curable adhesives, an external crosslinking agent can be appropriately used to adjust the adhesive strength before radiation irradiation and the adhesive strength after radiation irradiation. Specific means of the external crosslinking method include a method of adding and reacting so-called crosslinking agents such as polyisocyanate compounds, epoxy compounds, aziridine compounds, and melamine-based crosslinking agents. When using an external crosslinking agent, its usage amount is appropriately determined according to the balance with the base polymer to be crosslinked and further according to the usage purpose as an adhesive. Generally, the usage amount of the external crosslinking agent is 20 parts by weight or less (preferably 0.1 part by weight to 10 parts by weight) based on 100 parts by weight of the base polymer. Furthermore, if necessary, additives such as various conventionally known tackifiers, anti-aging agents, and foaming agents may be blended in the radiation-curable adhesive in addition to the above components.

[0087] Also, prior to the peeling of the support member after the back grinding and polishing of the wafer, a wafer processing adhesive tape is bonded to the polished surface of the wafer. However, when it is bonded to the wafer surface before the formation of the oxide film immediately after the back grinding, there is a problem that the subsequent peeling of the wafer processing adhesive tape becomes difficult. Therefore, in order to facilitate peeling even when it is bonded to the wafer surface before the formation of the oxide film immediately after the back grinding, it is preferable to add polypropylene oxide to the adhesive of the second adhesive layer.

[0088] The polypropylene oxide is not particularly limited and can be appropriately selected from conventional polypropylene oxides. The number average molecular weight of the polypropylene oxide is preferably greater than 3000 and 10000 or less, more preferably 4000 to 10000. If the number average molecular weight of the polypropylene oxide is too large, the affinity between the polypropylene oxide and the acrylic polymer (X) is poor, and contamination of the adherend occurs. If the number average molecular weight of the polypropylene oxide is too small, the water resistance of the adhesive layer becomes insufficient, the adhesive layer swells due to cutting water, and meandering of the dicing line occurs.

[0089] From the perspective of contamination of the wafer, polyoxypropylene-glyceryl ether having a number average molecular weight of more than 3,000 and not more than 10,000, more preferably 4,000 to 10,000, is preferred. By using polyoxypropylene-glyceryl ether having a number average molecular weight within this range, the number of hydroxyl groups in the polypropylene oxide molecule increases from 2 to 3. Therefore, the probability of incorporating polypropylene oxide into the crosslinked structure by reaction with a crosslinking agent such as polyisocyanate increases, and the migration of polypropylene oxide to the wafer interface and the contamination of the wafer surface can be reduced.

[0090] Examples of polypropylene oxide having a number average molecular weight of more than 3,000 and not more than 10,000 include Uniol D-4000 (number average molecular weight 4,000) (trade name, manufactured by NOF Corporation), Preminol S4007 (number average molecular weight 5,000) (trade name, manufactured by Asahi Glass Co., Ltd.), Preminol S4011 (number average molecular weight 10,000) (trade name, manufactured by Asahi Glass Co., Ltd.), and the like. Examples of polyoxypropylene-glyceryl ether having a number average molecular weight of more than 3,000 and not more than 10,000 include Uniol TG-4000 (number average molecular weight 4,000) (trade name, manufactured by NOF Corporation), Preminol S3006 (number average molecular weight 5,000) (trade name, manufactured by Asahi Glass Co., Ltd.), Preminol S3011 (number average molecular weight 10,000) (trade name, manufactured by Asahi Glass Co., Ltd.), etc., but are not limited thereto.

[0091] As the blending amount of polypropylene oxide having a number average molecular weight greater than 3000 and not exceeding 10000, it can be appropriately selected from the range of 0.1 to 3.0 parts by mass, preferably 0.5 to 2.0 parts by mass, based on 100 parts by mass of the base polymer. If the blending amount of polypropylene oxide is too small, when a wafer processing adhesive tape is bonded to an unstable wafer polishing surface where the natural oxide film is not completely formed, it is not possible to efficiently pick up thin semiconductor chips from a large-diameter wafer. If the blending amount of polypropylene oxide is too large, the adhesiveness before radiation curing becomes insufficient, the tip of the chip peels off during dicing, and cutting dust adheres to the back surface of the chip.

[0092] In the present invention, when it is stated that "the base film, the first adhesive layer, and the second adhesive layer are laminated in this order", it also includes a mode in which another layer is further laminated between the first adhesive layer and the second adhesive layer. In that case, the adhesive layer in contact with the base film is constituted by the above-mentioned first adhesive layer, and the adhesive layer for bonding the semiconductor wafer is constituted by the above-mentioned second adhesive layer.

[0093] The thickness of the first adhesive layer is preferably 5 μm or more and 70 μm or less, more preferably 8 μm or more and 50 μm or less, and still more preferably 10 μm or more and 30 μm or less. If the adhesive layer is thinner than 5 μm, there is a possibility that sufficient adhesive strength cannot be exhibited. On the other hand, if the adhesive layer is thicker than 70 μm, the force during expansion may not be sufficiently transmitted to the wafer, and there is a possibility that the wafer cannot be divided into chips. Further, if the adhesive layer is thicker than 30 μm, the parallel line transmittance of the wafer processing adhesive tape may decrease.

[0094] The method for forming the second adhesive layer on the first adhesive layer or another layer is not particularly limited. After applying the adhesive composition of the above-mentioned second adhesive layer on a release liner (for example, a plastic film or sheet coated with a release agent) to form the second adhesive layer, it is laminated on the first adhesive layer or another layer provided on the base film, whereby a wafer processing adhesive tape can be obtained.

[0095] The storage elastic modulus G’ of the first adhesive layer is preferably higher than that of the second adhesive layer. The storage elastic modulus G’ is measured by preparing a plurality of adhesive layers formed on a known release film, laminating two layers, peeling off the release film on one side, and repeating the process of laminating one more layer to create a test piece with a thickness of 1 to 2 mm, and then measuring with a dynamic viscoelasticity measuring machine at 23°C and a frequency of 1 Hz. Note that the storage elastic modulus is measured for the adhesive layer before radiation irradiation.

[0096] The storage elastic modulus G’ of the first adhesive layer is preferably 5×10 4 Pa to 100×10 4 Pa, more preferably 5×10 4 to 80×10 4 Pa, and even more preferably 10×10 4 to 70×10 4 Pa. If the storage elastic modulus G’ of the first adhesive layer is 30×10 4 Pa or more, the solvent resistance is sufficient. When peeling the support member from the wafer, when the adhesive is dissolved and washed with a solvent, wrinkles occur on the base film, stress is applied to the adhesive layer, and it is possible to prevent the adhesive force of the adhesive layer from decreasing, and the wafer can be sufficiently held. Also, even if the second adhesive layer is dissolved by a solvent, since the first adhesive layer holds the second adhesive layer, it is possible to prevent the second adhesive layer from falling off and contaminating the wafer, resulting in a reduction in yield.

[0097] The storage elastic modulus G’ of the second adhesive layer is preferably 5×10 4 Pa to 40×10 4 Pa, more preferably 5×10 4 to 20×10 4 Pa, and even more preferably 5×10 4 to 10×10 4 Pa. If the storage elastic modulus G’ of the second adhesive layer is higher than 10×10 4 Pa, in the case of a wafer having a step on the surface, the followability to the step becomes insufficient, and there is a possibility that the wafer cannot be sufficiently held.

[0098] The adhesive tape for wafer processing preferably has a residual solvent amount of 1% m / m or less on the surface of the second adhesive layer after dropping 1 ml of p-menthane and allowing it to stand for 30 minutes. If the residual solvent amount is 1% m / m or less, when the adhesive that bonded the support member to the wafer is dissolved using a solvent to peel off the support member and the adhesive remaining on the wafer is washed, wrinkles do not occur on the base film of the adhesive tape for wafer processing, stress is not applied to the adhesive layer, and a decrease in the adhesive strength of the adhesive layer can be prevented, and the wafer can be sufficiently held. Further, even if the second adhesive layer of the adhesive tape for wafer processing is dissolved by a solvent, since the first adhesive layer holds the second adhesive layer, it is possible to prevent the second adhesive layer from falling off and contaminating the wafer, resulting in a decrease in yield.

[0099] <Measurement of Residual Solvent Amount> After producing the adhesive tape for wafer processing (after taping), cut it into a 40 mm square, peel off the release liner, drop 1 mL of p-menthane, allow it to stand for 30 minutes, then discard the solvent, dry it at room temperature for 30 minutes, and immerse 1.0 g of the cut adhesive layer sample in 10 mL of acetone. The supernatant is measured under the following conditions by gas chromatography-mass spectrometry (GC-MS). [Analysis Conditions] Injection volume: 1 μL Column: db-1 0.25 mm × 30 m Inj: 200 °C (held at 40 °C for 4 minutes, then heated to 200 °C at 20 °C / min) He flow rate: 1.0 mL / min

[0100] To make the residual solvent amount 1% m / m or less, it is preferable to set the glass transition temperature of the base polymer of the second adhesive layer to -20 °C or higher.

[0101] In addition, for the adhesive tape for wafer processing, if necessary, a synthetic resin film, which is usually used as a separator to protect the adhesive layer until it is put into practical use, may be attached to the adhesive layer side. Examples of the constituent material of the synthetic resin film include synthetic resin films such as polyethylene, polypropylene, and polyethylene terephthalate, and paper. The surface of the synthetic resin film may be subjected to a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment, if necessary, to enhance the releasability from the adhesive layer. The thickness of the synthetic resin film is usually about 10 to 100 μm, preferably about 25 to 50 μm.

[0102] (Step of dissolving the adhesive with a solvent and cleaning the wafer) When peeling the wafer from the support member, the adhesive tape for wafer processing and the ring frame are attached to the surface of the wafer where the support member is not attached. Then, the wafer and the support member supported by the adhesive tape for wafer processing and the ring frame are immersed in an organic solvent to dissolve the adhesive that has attached the support member to the wafer, peel off the support member, and clean the surface of the wafer where the adhesive has adhered. In addition to the above method, to peel the wafer from the support member, there are also a method of heating to soften the adhesive and sliding the support member to peel it off, and a method of decomposing the adhesive by laser light irradiation to peel the support member. Even when these methods are used, adhesives or their decomposition products may remain on the wafer surface after peeling the support member. Therefore, in order to remove these residues, the wafer supported by the adhesive tape for wafer processing and the ring frame is immersed in an organic solvent to clean the wafer, or the wafer is rotated while spraying an organic solvent onto the wafer to clean the wafer.

[0103] The adhesive tape for electronic components according to the present invention includes the following aspects.

[0104] [1] An adhesive tape for wafer processing formed by laminating at least a base film, a first adhesive layer, and a second adhesive layer in this order, The first adhesive layer is formed of an adhesive composition containing an acrylic polymer or a polyester polymer as a base polymer, A wafer processing adhesive tape, characterized in that the glass transition temperature of the base polymer is -20°C or higher.

[0105] [2] The wafer processing adhesive tape according to [1], wherein the base film is composed of a polyolefin resin.

[0106] [3] The wafer processing adhesive tape according to [1] or [2], wherein the thickness of the base film is 70 to 350 μm.

[0107] [4] The wafer processing adhesive tape according to any one of [1] to [3], wherein the amount of residual solvent after dropping 1 ml of p-menthane on the surface of the second adhesive layer and allowing it to stand for 30 minutes is 1% (m / m) or less.

[0108] [5] The wafer processing adhesive tape according to any one of [1] to [4], wherein the storage modulus of the first adhesive layer is higher than that of the second adhesive layer.

[0109] [6] The wafer processing adhesive tape according to any one of [1] to [5], which is used in a wafer processing method including a step of cleaning the wafer with a solvent.

[0110] Next, the present invention will be described in more detail based on examples. Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples.

[0111] (1) Preparation of the base film <Base film 1> Using an ethylene-vinyl acetate copolymer (trade name "NUC-3660" manufactured by NUC Corporation), it was melted at 140°C and formed into a base film 1 with a thickness of 80 μm using an extruder. <Base film 2> Ethylene-methacrylic acid-(2-methyl-propyl acrylate)-Zn++ ionomer resin (manufactured by Mitsui DuPont Polychemical Co., Ltd., trade name "Hymilan AM7316") was melted at 140°C and formed into a base film 2 with a thickness of 350 μm using an extruder. <Base film 3> Polypropylene (manufactured by Prime Polymer Co., Ltd., trade name "F227D") was melted at 140°C and formed into a base film 3 with a thickness of 70 μm using an extruder.

[0112] (2) Preparation of adhesive <Adhesive 1> An acrylic copolymer consisting of ethyl acrylate (81 wt%), methacrylic acid (1 wt%), and 2-hydroxyethyl acrylate (18 wt%) was prepared. Then, 2-methacryloyloxyethyl isocyanate was added to react the OH group at the end of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer with the NCO group of 2-methacryloyloxyethyl isocyanate, and a residue having a (meth)acrylic monomer part with a radiation-curable carbon-carbon double bond-containing group was bonded to the repeating unit of the main chain to obtain an acrylic polymer as a base polymer. When the glass transition temperature of this acrylic polymer was measured by a differential scanning calorimeter (DSC), it was -20°C. To 100 parts by mass of the acrylic polymer, 2 parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "Coronate L") and 1.5 parts by mass of a photoinitiator (manufactured by BASF, trade name "Irgacure 184") were added and mixed to obtain an acrylic adhesive 1.

[0113] <Adhesive 2> Nichigo Polyester (registered trademark) S-0097S55EO, an adhesive containing a polyester polymer as the base polymer, manufactured by Mitsubishi Chemical Corporation, was prepared. The glass transition temperature of the polyester polymer, which is the base polymer, is 1°C. To 100 parts by mass of the polyester polymer, 3 parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "Coronate L") was added and mixed to obtain a polyester-based adhesive 2.

[0114] <Adhesive 3> An acrylic copolymer consisting of 2-ethylhexyl acrylate (69 wt%), methyl methacrylate (10 wt%), 2-hydroxyethyl acrylate (20 wt%), and methacrylic acid (1 wt%) was prepared. Then, 2-methacryloyloxyethyl isocyanate was added to react the OH group at the end of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer with the NCO group of 2-methacryloyloxyethyl isocyanate, and a residue having a (meth)acrylic monomer part with a radiation-curable carbon-carbon double bond-containing group was bonded to the repeating unit of the main chain to obtain an acrylic polymer as the base polymer. When the glass transition temperature of this acrylic polymer was measured by a differential scanning calorimeter (DSC), it was -50°C. To 100 parts by mass of the acrylic polymer, 2 parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "Coronate L") and 1.5 parts by mass of a photoinitiator (manufactured by BASF, trade name "Irgacure 184") were added and mixed to obtain an acrylic-based adhesive 3.

[0115] <Adhesive 4> An acrylic copolymer consisting of 2-ethylhexyl acrylate (78 wt%), methacrylic acid (1 wt%), and 2-hydroxyethyl acrylate (21 wt%) was prepared. Then, 2-methacryloyloxyethyl isocyanate was added to react the OH group at the end of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer with the NCO group of 2-methacryloyloxyethyl isocyanate, and a residue having a (meth)acrylic monomer part having a radiation-curable carbon-carbon double bond-containing group with respect to the repeating unit of the main chain was bonded. An acrylic polymer was obtained as a base polymer. When the glass transition temperature of this acrylic polymer was measured by a differential scanning calorimeter (DSC), it was -64°C. To 100 parts by mass of the acrylic polymer, 2 parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "Coronate L") and 1.5 parts by mass of a photopolymerization initiator (manufactured by BASF, trade name "Irgacure 184") were added and mixed to obtain an acrylic adhesive 4.

[0116] <Adhesive 5> An acrylic copolymer consisting of butyl acrylate (70 wt%), methacrylic acid (1 wt%), and 2-hydroxyethyl acrylate (29 wt%) was prepared. Then, 2-methacryloyloxyethyl isocyanate was added to react the OH group at the end of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer with the NCO group of 2-methacryloyloxyethyl isocyanate, and a residue having a (meth)acrylic monomer part having a radiation-curable carbon-carbon double bond-containing group with respect to the repeating unit of the main chain was bonded. An acrylic polymer was obtained as a base polymer. When the glass transition temperature of this acrylic polymer was measured by a differential scanning calorimeter (DSC), it was -45°C. To 100 parts by mass of the acrylic polymer, 2 parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "Coronate L") and 1.5 parts by mass of a photopolymerization initiator (manufactured by BASF, trade name "Irgacure 184") were added and mixed to obtain an acrylic adhesive 5.

[0117] <Adhesive 6> An acrylic copolymer consisting of methyl acrylate (62 wt%), acrylic acid (6 wt%), 2-hydroxyethyl acrylate (4 wt%), and 2-ethylhexyl acrylate (28 wt%) was prepared, and an acrylic polymer was obtained as the base polymer. When the glass transition temperature of this acrylic polymer was measured by a differential scanning calorimeter (DSC), it was -10°C. To 100 parts by mass of the acrylic polymer, 2 parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "Coronate L") was added and mixed to obtain an acrylic adhesive 6.

[0118] <Adhesive 7> An acrylic copolymer consisting of methyl methacrylate (25 wt%), 2-ethylhexyl acrylate (54 wt%), methacrylic acid (1 wt%), and 2-hydroxyethyl acrylate (20 wt%) was prepared. Then, 2-methacryloyloxyethyl isocyanate was added, and the OH group at the terminal of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer was reacted with the NCO group of 2-methacryloyloxyethyl isocyanate to bond a residue having a (meth)acrylic monomer unit having a radiation-curable carbon-carbon double bond-containing group to the repeating unit of the main chain. An acrylic polymer was obtained as the base polymer. When the glass transition temperature of this acrylic polymer was measured by a differential scanning calorimeter (DSC), it was -30°C. To 100 parts by mass of the acrylic polymer, 4 parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "Coronate L") and 1.5 parts by mass of a photoinitiator (manufactured by BASF, trade name "Irgacure 184") were added and mixed to obtain an acrylic adhesive 7.

[0119] (3) Preparation of Adhesive Tape for Wafer Processing <Example 1> The pressure-sensitive adhesive composition obtained by dissolving the pressure-sensitive adhesive 1 in ethyl acetate and stirring was applied to a release liner made of a polyethylene terephthalate film subjected to a release treatment so that the thickness after drying would be 10 μm, dried at 110°C for 3 minutes, and then laminated to the base film 1 to form a first pressure-sensitive adhesive layer on the base film. Also, the pressure-sensitive adhesive composition obtained by dissolving the pressure-sensitive adhesive 4 in ethyl acetate and stirring was applied to a release liner made of a polyethylene terephthalate film subjected to a release treatment so that the thickness after drying would be 10 μm, dried at 110°C for 3 minutes to obtain a second pressure-sensitive adhesive layer. Then, the release liner was peeled off from the first pressure-sensitive adhesive layer, and the second pressure-sensitive adhesive layer was laminated on the first pressure-sensitive adhesive layer to prepare a pressure-sensitive adhesive tape for wafer processing according to Example 1.

[0120] <Examples 2 to 9, Comparative Examples 1 to 5> Except that the base film and the pressure-sensitive adhesive layer were made into the combinations described in Tables 1 and 2, pressure-sensitive adhesive tapes for wafer processing according to Examples 2 to 9 and Comparative Examples 1 to 5 were prepared by the same method as in Example 1.

[0121] <Measurement of Residual Solvent Amount> After the pressure-sensitive adhesive tape for wafer processing was produced (after being made into a tape), it was cut into a 40 mm square, the release liner was peeled off, 1 mL of p-menthane was dropped, and it was allowed to stand for 30 minutes. Then, the solvent was discarded and it was dried at room temperature for 30 minutes. 1.0 g of the cut pressure-sensitive adhesive layer sample was immersed in 10 mL of acetone. The supernatant was measured under the following conditions by gas chromatography-mass spectrometry (GC-MS). The results are shown in Tables 1 and 2. [Analysis Conditions] Injection volume: 1 μL Column: db-1 0.25 mm × 30 m Inj: 200°C (held at 40°C for 4 minutes and then heated to 200°C at 20°C / min) He flow rate: 1.0 mL / min

[0122] <Measurement of Storage Elastic Modulus> The storage elastic modulus of the first adhesive layer and the second adhesive layer according to the examples and comparative examples was measured as follows. 100 sheets were prepared by coating an adhesive on a release film so that the thickness after drying was 20 μm, drying at 110 °C for 3 minutes to form an adhesive layer, peeling off the release film, laminating until the thickness reached 2.0 mm, and punching out test pieces with a diameter of 8 mm. These test pieces were supplied to a dynamic viscoelasticity measuring machine (manufactured by Rheometric), and the storage elastic modulus G' at 23 °C and a frequency of 1 Hz was measured. The results are shown in Tables 1 and 2.

[0123] <Evaluation of solvent resistance> An adhesive tape for wafer processing according to the examples and comparative examples was bonded to an 8-inch wafer and fixed to a ring frame. Then, while spraying p-menthane as an organic solvent from the wafer side, it was rotated at 2000 rpm for spin cleaning. After washing and drying, the adhesive layer in the area where the wafer of the dicing tape for wafer processing was not adhered was observed. Samples in which the second adhesive layer was dissolved or swollen but there was no portion held by the first adhesive layer and peeled off were evaluated as good products with ○, and samples in which the second adhesive layer was dissolved or swollen and there was a portion peeled off from the first adhesive layer, or samples in which wrinkles occurred in the base film were evaluated as defective products with ×. The results are shown in Tables 1 and 2.

[0124]

Table 1

[0125]

Table 2

[0126] As shown in Table 1, the adhesive tape for wafer processing according to the examples has a first adhesive layer and a second adhesive layer laminated in this order on a base film. The first adhesive layer is formed of an adhesive composition containing an acrylic polymer or a polyester polymer as a base polymer, and since the glass transition temperature of the base polymer is -20 °C or higher, excellent results were obtained in the evaluation of solvent resistance.

[0127] On the other hand, as shown in Table 2, the adhesive tape for wafer processing according to the comparative example had a glass transition temperature of the base polymer of the first adhesive layer lower than -20°C, resulting in inferior results in the solvent resistance evaluation.

Claims

1. An adhesive tape for wafer processing comprising at least a base film, a first adhesive layer, and a second adhesive layer laminated in this order, the first pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing an acrylic polymer or a polyester polymer as a base polymer, The glass transition temperature of the base polymer is −20° C. or higher, An adhesive tape for wafer processing, characterized in that the storage modulus of the first adhesive layer is higher than the storage modulus of the second adhesive layer.

2. 2. The adhesive tape for wafer processing according to claim 1, wherein the base film is made of a polyolefin resin.

3. 3. The adhesive tape for wafer processing according to claim 1, wherein the thickness of the base film is 70 to 350 μm.

4. 3. The adhesive tape for wafer processing according to claim 1, wherein the amount of residual solvent is 1% m / m or less after 1 ml of p-menthane is dropped onto the surface of the second adhesive layer and allowed to stand for 30 minutes.

5. An adhesive tape for wafer processing as described in claim 1 or claim 2, characterized in that it is used in a wafer processing method including a wafer cleaning step using a solvent.

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