Adhesive tape for wafer processing

Abstract

To provide an adhesive tape for wafer processing that can properly hold a wafer even when used in a wafer processing process using a support member, by dissolving the adhesive that has stuck the support member to the wafer with a solvent, peeling off the support member, and cleaning off the adhesive remaining on the wafer, thereby preventing a decrease in yield due to wafer contamination.SOLUTION: An adhesive tape for wafer processing according to the present invention includes at least a base film, a first adhesive layer, and a second adhesive layer laminated in this order, and the first adhesive layer is formed from 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.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive tape for wafer processing used in wafer dicing, and more particularly to an adhesive tape for wafer processing used in a wafer processing method including a wafer cleaning step with a solvent. [Background technology]

[0002] When thinning the backside of a wafer carrying a wiring pattern, a protective tape is typically applied to the patterned surface of the wafer to protect the wafer's patterned surface and secure the wafer in place, followed by thinning processes such as polishing and grinding. Such protective tapes typically comprise a plastic film substrate coated with an acrylic adhesive. However, with the recent trend toward thinner and more compact IC cards and mobile phones, chip thicknesses of 50 μm or less are now required. In processes using conventional protective tapes, the protective tape alone is insufficient to support the wafer. This makes handling difficult due to wafer warpage after grinding and bending during storage in a wafer cassette, making automated handling and transport difficult.

[0003] To address this issue, a method has been proposed in which a glass substrate, ceramic substrate, silicon wafer substrate, or the like is bonded to the wafer with an adhesive to provide support to the wafer (see, for example, Patent Document 1). By using a support member such as a glass substrate, ceramic substrate, or silicon wafer substrate in this way, wafer handling is greatly improved and automated transport becomes possible. The support member can also be used to support the wafer while it is being subjected to the backside wiring and bump formation process.

[0004] When a wafer is handled using a support member, a process of peeling the support member from the wafer is required. Peeling the support member is generally performed by dissolving the adhesive using a solvent and then cleaning the support member. Other methods for peeling the wafer from the support member include heating to soften the adhesive and sliding the support member to peel it off, and laser irradiation to decompose the adhesive and peel the support member. Even when using these methods, adhesive or its decomposition products may remain on the wafer surface after the support member is peeled off. To remove these residues, the wafer is cleaned by immersing it in an organic solvent or by rotating the wafer while spraying the organic solvent on it.

[0005] The wafer is then transferred to a dicing process where it is cut into individual chips. In the dicing process, an adhesive tape for wafer processing, in which an adhesive layer is laminated on a base film, is generally used (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-135272 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-100064 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, when the thickness of a wafer is 50 μm or less, handling the wafer alone becomes very difficult due to warping of the wafer after grinding and bending during storage in a wafer cassette, so it is common practice to apply a wafer processing adhesive tape to the ground surface of the wafer after backgrinding and polishing, and then support and fix the wafer to a ring frame before removing the support member. Therefore, when the adhesive is dissolved or cleaned with a solvent during support member removal, the wafer remains attached to the wafer processing adhesive tape, and high solvent resistance is required for the wafer processing adhesive tape.

[0008] However, ordinary adhesive tapes for wafer processing, such as the adhesive tape for wafer processing described in Patent Document 2, have insufficient solvent resistance, which reduces the adhesive strength of the adhesive layer of the adhesive tape for wafer processing, making it unable to hold the wafer sufficiently.In addition, there is also the problem that the adhesive layer of the adhesive tape for wafer processing dissolves in solvents, contaminating the wafer and reducing yield.

[0009] Therefore, an object of the present invention is to provide an adhesive tape for wafer processing that, even when used in a wafer processing step using a support member, can properly hold the wafer even after the adhesive that has bonded the support member to the wafer is dissolved with a solvent to peel off the support member or after the adhesive remaining on the wafer is washed away, thereby preventing a decrease in yield due to wafer contamination. [Means for solving the problem]

[0010] As a result of extensive research to achieve the above object, the present inventors have found that the glass transition temperature of the base polymer of the pressure-sensitive adhesive layer is related to solvent resistance. The present invention is based on this finding.

[0011] That is, the adhesive tape for wafer processing according to the present invention is an adhesive tape for wafer processing comprising a base film, a first adhesive layer, and a second adhesive layer laminated in this order, wherein the first adhesive layer is formed from 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] In the above-mentioned adhesive tape for wafer processing, the base film is preferably made of a polyolefin resin.

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

[0014] Furthermore, the adhesive tape for wafer processing preferably has a residual solvent amount of 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.

[0015] In the pressure-sensitive adhesive tape for wafer processing, the storage modulus of the first pressure-sensitive adhesive layer is preferably higher than the storage modulus of the second pressure-sensitive adhesive layer.

[0016] The adhesive tape for wafer processing is preferably used in a wafer processing method including a step of cleaning the wafer with a solvent. [Effects of the Invention]

[0017] According to the present invention, even when used in a wafer processing process that uses a support member, the adhesive that has attached the support member to the wafer can be dissolved using a solvent, and even after the support member has been peeled off and the adhesive remaining on the wafer has been washed away, the wafer can still be held in place, preventing a decrease in yield due to wafer contamination. DETAILED DESCRIPTION OF THE INVENTION

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

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

[0020] The base film, the first pressure-sensitive adhesive layer, and the second pressure-sensitive adhesive layer are preferably cut (precut) into shapes corresponding to ring frames used for dividing wafers. Furthermore, the pressure-sensitive adhesive tape for wafer processing of the present invention may be cut into pieces corresponding to individual wafers, or may be in the form of a long separator formed by cutting a plurality of pieces corresponding to individual wafers and wound into a roll.

[0021] Hereinafter, each of the components of the adhesive tape for wafer processing of this embodiment will be described in detail.

[0022] (Base film) Examples of resins that may be used to form the substrate 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-methyl(meth)acrylate copolymer, ethylene-ethyl(meth)acrylate copolymer, ethylene-butyl(meth)acrylate 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 water-added or modified natural rubbers.

[0023] Among these, the base film is preferably made of a polyolefin resin, since it exhibits excellent extensibility when expanded. Examples of polyolefin resins include α-olefin homopolymers or copolymers, 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, and ionomers, as well as mixtures thereof.

[0024] In particular, in the case of a substrate film using an ionomer, uniform physical properties can be obtained in the unwinding direction and width direction of the substrate film, and therefore, when dividing by expanding, the intervals between the individual chips can be made uniform.

[0025] The substrate 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. A laminate of one type of resin is preferred from the viewpoint of enhancing and manifesting the properties of each resin, while a laminate of two or more resins is preferred from the viewpoint of compensating for the drawbacks of each resin.

[0026] The multilayer substrate film can be produced by a conventionally known extrusion method, lamination method, or the like. When a lamination method is used, an adhesive may be interposed between the layers. A conventionally known adhesive can be used as the adhesive.

[0027] The thickness of the base film is preferably 70 to 350 μm, and more preferably 250 to 300 μm. If it is 350 μm or more, it may be difficult to pick up the chip from the adhesive tape for wafer processing, and if it is thinner than 70 μm, the adhesive tape for wafer processing may tear during expansion.

[0028] The surface of the substrate film that comes into contact with the first pressure-sensitive adhesive layer may be subjected to a corona treatment or a treatment such as a primer in order to improve adhesion.

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

[0030] An "acrylic polymer" refers to a polymer containing, as a monomer unit constituting the polymer, a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an "acrylic monomer." Therefore, in this specification, an acrylic polymer is defined as a polymer containing a monomer unit derived from an acrylic monomer. A typical example of an acrylic polymer is an acrylic polymer in which the proportion of acrylic monomers in all monomer components used in the synthesis of the acrylic polymer is more than 50% by weight. Additionally, "(meth)acryloyl" refers collectively to acryloyl and methacryloyl. Similarly, "(meth)acrylate" refers collectively to acrylate and methacrylate, and "(meth)acrylic" refers collectively to acrylic and methacrylic.

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

[0032] The base polymer constituting the first PSA 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 calorimetry) at a heating rate of 0.1°C / min. A glass transition temperature of -20°C or higher provides sufficient solvent resistance, and when the adhesive is dissolved and washed with a solvent to peel the support member from the wafer, wrinkles are generated in the base film, which can prevent stress from being applied to the PSA layer and a decrease in the adhesive strength of the PSA layer, thereby enabling sufficient wafer retention. Furthermore, even if the second PSA layer dissolves in a solvent, the first PSA layer holds the second PSA layer in place, preventing the second PSA layer from falling off and contaminating the wafer, resulting in a decrease in yield. The glass transition temperature of the base polymer constituting the PSA is more preferably greater than -15°C and less than 1°C, and even more preferably greater than -10°C and less than 1°C.

[0033] The first pressure-sensitive adhesive layer is preferably a radiation-curable type that is cured by irradiation with radiation. The pressure-sensitive adhesive composition constituting the radiation-curable first pressure-sensitive adhesive layer can be a combination of a polymer constituting the pressure-sensitive adhesive and a radiation-polymerizable compound, or a polymer constituting the pressure-sensitive adhesive that incorporates a functional group (preferably an ethylenically unsaturated group) that polymerizes upon radiation. It is preferable to contain a photopolymerization initiator to promote polymerization upon radiation. It is also preferable to contain a crosslinking agent. By incorporating a monomer having a functional group that can react with the crosslinking agent into the polymer constituting the pressure-sensitive adhesive, it is possible to adjust the film hardness and gel fraction. Furthermore, additives other than those mentioned above can also be contained as necessary. These will be explained in more detail below.

[0034] Examples of acrylic polymers include acrylic polymers using one or more of (meth)acrylic acid alkyl esters (e.g., 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, and other linear or branched alkyl esters having 1 to 30 carbon atoms, particularly 4 to 18 carbon atoms) and (meth)acrylic acid cycloalkyl esters (e.g., cyclopentyl ester, cyclohexyl ester). The term "(meth)acrylic acid ester" refers to 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 contain, as necessary, units corresponding to other monomer components copolymerizable with the (meth)acrylic acid alkyl ester or cycloalkyl ester for the purpose of improving cohesive strength, 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, and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and 10-hydroxydecyl (meth)acrylate; Examples of copolymerizable monomers include hydroxyl group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; phosphate group-containing monomers such as 2-hydroxyethylacryloylphosphate; acrylamide, and acrylonitrile. These copolymerizable monomer components can be used alone or in combination. The amount of these copolymerizable monomers used is preferably 40% by weight or less of the total monomer components.

[0036] Furthermore, since acrylic polymers are crosslinked, polyfunctional monomers can also be included as copolymerization monomer components 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, and urethane (meth)acrylate. These polyfunctional monomers can also be used alone or in combination. The amount of polyfunctional monomer used is preferably 30% by weight or less of the total monomer components in terms of adhesive properties, etc.

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

[0038] In addition, various methods can be used to control the crosslink density of the first pressure-sensitive adhesive layer, such as a crosslinking treatment using 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, or a crosslinking treatment by mixing a low-molecular-weight compound having two or more carbon-carbon double bonds and irradiating it with radiation. When an external crosslinking agent is used, the amount used is determined appropriately based on the balance with the base polymer to be crosslinked and the intended use of the pressure-sensitive adhesive. Generally, it is preferable to blend about 20 parts by weight or less, and more preferably 0.1 to 20 parts by weight, per 100 parts by weight of the base polymer. In addition to the above components, various additives such as tackifiers and antioxidants may be used in the pressure-sensitive adhesive, as needed, to prevent deterioration.

[0039] The adhesive constituting the first adhesive layer is preferably a radiation-curable adhesive, such as an additive-type radiation-curable adhesive obtained by blending a radiation-curable monomer component or a radiation-curable oligomer component with the adhesive described above.

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

[0041] The radiation-curable oligomer component may be a variety of 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 amount of the radiation-curable monomer component or oligomer component to be added can be determined appropriately depending on the type of first pressure-sensitive adhesive layer, so as to reduce the adhesive strength of the first pressure-sensitive adhesive layer. Generally, the amount is, for example, 5 to 500 parts by weight, and preferably about 70 to 150 parts by weight, per 100 parts by weight of the base polymer, such as an acrylic polymer, that constitutes the pressure-sensitive adhesive.

[0042]

[0033] In addition to the additive-type radiation-curable adhesives, examples of the radiation-curable adhesive include intrinsic-type radiation-curable adhesives that use a base polymer in which a radiation-curable group has been introduced into a polymer side chain, main chain, or main chain terminal. Intrinsic-type radiation-curable adhesives do not need to contain low-molecular-weight components such as oligomer components, or do not contain large amounts thereof, and are therefore preferred because they do not allow the oligomer components to migrate within the adhesive over time, allowing the formation of a first adhesive layer with a stable layer structure.

[0043] The base polymer into which the radiation-curable group is introduced can be any polymer that has a carbon-carbon double bond and adhesiveness, without any particular limitations. Such a base polymer is preferably one having an acrylic polymer skeleton. Examples of the acrylic polymer skeleton 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 used, but it is easy in terms of molecular design to introduce the radiation-curable group into the polymer side chain. For example, there is a method in which a monomer having a functional group is copolymerized into an acrylic polymer in advance, and then a compound having a functional group and a carbon-carbon double bond that can react with the functional group 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, and a hydroxyl group and an isocyanate group. Among these combinations of functional groups, a combination of a hydroxyl group and an isocyanate group is preferred due to the ease of reaction tracking. Furthermore, as long as the combination of these functional groups produces the acrylic polymer having a carbon-carbon double bond, the functional group may be located on either the acrylic polymer or the compound. However, the preferred combination is one in which the acrylic polymer has a hydroxyl group and the compound has an isocyanate group. In this case, examples of isocyanate compounds having a carbon-carbon double bond include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate. Furthermore, acrylic polymers that are copolymerized with the hydroxyl group-containing monomers listed above or ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether can be used.

[0046] The inherent radiation-curable adhesive can use the base polymer having a carbon-carbon double bond (particularly an acrylic polymer) alone, but can also contain a photopolymerizable compound such as the radiation-curable monomer or oligomer component to the extent that the properties are not impaired. The amount of the photopolymerizable compound is usually 30 parts by weight or less, and preferably 0 to 10 parts by weight, per 100 parts by weight of the base polymer.

[0047] When the radiation-curable adhesive is to be cured by ultraviolet light or the like, it is preferable that the adhesive contains a photopolymerization initiator.

[0048] Among the above-mentioned acrylic polymers, a (meth)acrylic acid ester copolymer having a radiation-curable group introduced into the side chain is particularly preferred, more specifically, a (meth)acrylic acid ester copolymer comprising an acrylic acid ester represented by CH═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.

[0049] The amount of carbon-carbon double bonds is preferably 1.2 to 1.8 meq / g. The amount of double bonds can be quantitatively measured by a weight increase method using a bromine addition reaction in a dark place under vacuum, where the amount of carbon-carbon double bonds contained in approximately 10 g of heat-dried PSA can be determined.

[0050] The (meth)acrylic acid ester copolymer may contain units corresponding to other monomer components, if 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, etc. The double bond-containing isocyanate compounds can be used alone or in combination of two or more.

[0052] An external crosslinking agent may also be used in the radiation-curable pressure-sensitive adhesive to adjust the adhesive strength before and after irradiation. Specific examples of external crosslinking methods include 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 an external crosslinking agent is used, its amount is determined appropriately based on the balance with the base polymer to be crosslinked and the intended use of the pressure-sensitive adhesive. The amount of external crosslinking agent used is generally 20 parts by weight or less (preferably 0.1 to 10 parts by weight) per 100 parts by weight of the base polymer. Furthermore, the radiation-curable pressure-sensitive adhesive may contain, as necessary, various conventionally known additives, such as tackifiers, antioxidants, and foaming agents, in addition to the above components.

[0053] The polyester used in the polyester-based polymer is a polyester obtained by polycondensation of a difunctional or higher carboxylic acid component and a diol component, and the weight-average molecular weight of the polyester is preferably 8500 to 50000. Furthermore, the polyester preferably contains at least a difunctional or higher carboxylic acid component, 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, but examples thereof include sebacic acid derived from castor oil, and dimer acids derived from oleic acid, erucic acid, etc. Other examples include adipic acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, dodecenylsuccinic anhydride, fumaric acid, succinic acid, dodecanedioic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, maleic acid, maleic anhydride, itaconic acid, citraconic acid, and other aliphatic or alicyclic dicarboxylic acids, as well 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 these, dimer acids are particularly preferred because they have a low glass transition temperature, making it possible to design flexible pressure-sensitive adhesives and they can exhibit good wetting properties. Furthermore, dimer acids are non-petroleum-derived materials (plant-derived raw materials), which makes them environmentally friendly and useful. These can be used alone or in combination of two or more.

[0055] The polyester preferably contains a diol component having at least two hydroxyl groups in the molecule, and among these, it is preferable to use an aliphatic diol or polyether glycol.

[0056] The aliphatic diol is particularly preferably an aliphatic diol having an alkylene group having 3 to 10 carbon atoms. The aliphatic diol having an alkylene group having 3 to 10 carbon atoms is not particularly limited, but specific examples include aliphatic glycols such as 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, and 1,2-cyclohexanedimethanol. These may be used alone or in combination of two or more.

[0057] The polyether glycol is not particularly limited, but it is preferable to use a polyether glycol having hydroxyl groups at both ends. The number-average molecular weight (Mn) of the polyether glycol having hydroxyl groups at both ends is not particularly limited, and specific examples include polyalkylene ether glycols such as polytetramethylene ether glycol and polytrimethylene ether glycol, copolymer polyether polyols of 1 to 20 mol% 3-methyltetrahydrofuran and tetrahydrofuran (e.g., "PTG-L1000," "PTG-L2000," "PTG-L3500," etc., manufactured by Hodogaya Chemical Co., Ltd.), and copolymer polyether glycols of neopentyl glycol and tetrahydrofuran. These may be used alone or in combination of two or more.

[0058] The polyester is obtained by polycondensation of a carboxylic acid component and a diol component. The molar ratio (OH / COOH) of the carboxyl groups of the carboxylic acid component to the hydroxyl groups of the diol component is preferably 1 or greater, more preferably 1.02 to 3, even more preferably 1.04 to 2.60, and particularly preferably 1.06 to 2.40. If the molar ratio is less than 1, the polyester (polymer) after polymerization will have a carboxyl group at its terminal, which may hinder subsequent crosslinking with a crosslinking agent (e.g., an isocyanate-based crosslinking agent) from proceeding quickly, and the adhesive layer may not have sufficient holding power (cohesion).

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

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

[0061] When a polyester polymer is used as the base polymer, the pressure-sensitive adhesive composition of the first pressure-sensitive adhesive layer preferably contains, in addition to the polyester polymer, a fatty acid ester that does not have a functional group and has a molecular weight (molar molecular weight: g / mol) of 200 to 700. Examples of fatty acid esters that can be used include isopropyl myristate, isopropyl palmitate, methyl linoleate, and dibasic acid esters such as adipate, sebacate, and phthalate. These can be used alone or in combination of two or more. The amount of fatty acid ester to be added is 10 to 150 parts by weight, preferably 20 to 150 parts by weight, more preferably 30 to 140 parts by weight, and even more preferably 40 to 130 parts by weight, per 100 parts by weight of the polyester polymer.

[0062] The pressure-sensitive adhesive composition also contains a crosslinking agent in addition to the polyester polymer. The crosslinking agent is not particularly limited, and conventionally known crosslinking agents can be used, such as isocyanate crosslinking agents such as polyisocyanurates and polyfunctional isocyanate compounds, polyfunctional melamine compounds, polyfunctional epoxy compounds, polyfunctional oxazoline compounds, polyfunctional aziridine compounds, and metal chelate compounds. 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 a conventionally known polyisocyanurate or polyfunctional isocyanate. Examples of polyisocyanurates include polyisocyanurates of hexamethylene diisocyanate. The polyfunctional isocyanate compound is preferably, for example, a compound having at least two isocyanate groups in the molecule, more preferably three or more, and is not particularly limited. Specific examples include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

[0064] The thickness of the first adhesive layer is preferably 5 μm to 70 μm, more preferably 5 μm to 30 μm, and even more preferably 5 μm to 15 μm. If the adhesive layer is thinner than 5 μm, sufficient adhesive strength may not 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, making it impossible to separate the wafer into chips.

[0065] The method for forming the first pressure-sensitive adhesive layer on the base film is not particularly limited, and for example, the first pressure-sensitive adhesive layer can be formed by applying the above-mentioned pressure-sensitive adhesive composition to the base film by a commonly used application method and drying it, or by transferring the pressure-sensitive adhesive layer applied to a separator to the base film by laminating the separator to the base film.

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

[0067] The second pressure-sensitive adhesive layer is preferably a radiation-curable type that is cured by irradiation with radiation. The pressure-sensitive adhesive composition constituting the radiation-curable second pressure-sensitive adhesive layer can be a combination of a polymer constituting the pressure-sensitive adhesive and a radiation-polymerizable compound, or a polymer constituting the pressure-sensitive adhesive that incorporates a functional group (preferably an ethylenically unsaturated group) that polymerizes upon radiation. It is preferable to contain a photopolymerization initiator to promote polymerization upon radiation. It is also preferable to contain a crosslinking agent. By incorporating a monomer having a functional group that can react with the crosslinking agent into the polymer constituting the pressure-sensitive adhesive, it is possible to adjust the film hardness and gel fraction. Furthermore, additives other than those mentioned above can also be contained as necessary. These will be explained in more detail below.

[0068] Examples of acrylic polymers include (meth)acrylic acid alkyl esters (e.g., 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 of such acrylic polymers include acrylic polymers using, as monomer components, one or more of (meth)acrylic acid cycloalkyl esters (e.g., cyclopentyl ester, cyclohexyl ester, etc.) and (meth)acrylic acid cycloalkyl esters (e.g., cyclopentyl ester, cyclohexyl ester, etc.) of alkyl esters having 1 to 30 carbon atoms, particularly 4 to 18 carbon atoms, such as tetradecyl ester, hexadecyl ester, octadecyl ester, eicosyl ester, etc. In addition, the term "(meth)acrylic acid ester" refers to an acrylic acid ester and / or a methacrylic acid ester, and all "(meth)" in the present invention has the same meaning.

[0069] The acrylic polymer may contain, as necessary, units corresponding to other monomer components copolymerizable with the (meth)acrylic acid alkyl ester or cycloalkyl ester for the purpose of improving cohesive strength, 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, and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and 10-hydroxydecyl (meth)acrylate; Examples of copolymerizable monomers include hydroxyl group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; phosphate group-containing monomers such as 2-hydroxyethylacryloylphosphate; acrylamide, and acrylonitrile. These copolymerizable monomer components can be used alone or in combination. The amount of these copolymerizable monomers used is preferably 40% by weight or less of the total monomer components.

[0070] Furthermore, since acrylic polymers are crosslinked, polyfunctional monomers can also be included as copolymerization monomer components 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, and urethane (meth)acrylate. These polyfunctional monomers can also be used alone or in combination. The amount of polyfunctional monomer used is preferably 30% by weight or less of the total monomer components in terms of adhesive properties, etc.

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

[0072] In addition, various methods can be used to control the crosslink density of the second pressure-sensitive adhesive layer, such as a crosslinking treatment using 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, or a crosslinking treatment by mixing a low-molecular-weight compound having two or more carbon-carbon double bonds and irradiating it with radiation. When an external crosslinking agent is used, the amount used is determined appropriately based on the balance with the base polymer to be crosslinked and the intended use of the pressure-sensitive adhesive. Generally, it is preferable to blend about 20 parts by weight or less, and more preferably 0.1 to 20 parts by weight, per 100 parts by weight of the base polymer. In addition to the above components, various additives such as tackifiers and antioxidants may be used in the pressure-sensitive adhesive, as needed, to prevent deterioration.

[0073] The adhesive constituting the second adhesive layer is preferably a radiation-curable adhesive, such as an additive-type radiation-curable adhesive obtained by blending a radiation-curable monomer component or a radiation-curable oligomer component with the above-mentioned adhesive.

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

[0075] The radiation-curable oligomer component may be a variety of 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 amount of the radiation-curable monomer component or oligomer component to be added can be determined appropriately depending on the type of first pressure-sensitive adhesive layer, so as to reduce the adhesive strength of the first pressure-sensitive adhesive layer. Generally, the amount is, for example, 5 to 500 parts by weight, and preferably about 70 to 150 parts by weight, per 100 parts by weight of the base polymer, such as an acrylic polymer, that constitutes the pressure-sensitive adhesive.

[0076]

[0033] In addition to the additive-type radiation-curable adhesives, examples of the radiation-curable adhesive include intrinsic-type radiation-curable adhesives that use a base polymer in which a radiation-curable group has been introduced into a polymer side chain, main chain, or main chain terminal. Intrinsic-type radiation-curable adhesives do not need to contain low-molecular-weight components such as oligomer components, or do not contain large amounts thereof, and are therefore preferred because they do not allow the oligomer components to migrate within the adhesive over time, allowing the formation of a first adhesive layer with a stable layer structure.

[0077] The base polymer into which the radiation-curable group is introduced can be any polymer that has a carbon-carbon double bond and adhesiveness, without any particular limitations. Such a base polymer is preferably one having an acrylic polymer skeleton. Examples of the acrylic polymer skeleton 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 used, but it is easy in terms of molecular design to introduce the radiation-curable group into the polymer side chain. For example, there is a method in which a monomer having a functional group is copolymerized into an acrylic polymer in advance, and then a compound having a functional group and a carbon-carbon double bond that can react with the functional group 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, and a hydroxyl group and an isocyanate group. Among these combinations of functional groups, a combination of a hydroxyl group and an isocyanate group is preferred due to the ease of reaction tracking. Furthermore, as long as the combination of these functional groups produces the acrylic polymer having a carbon-carbon double bond, the functional group may be located on either the acrylic polymer or the compound. However, the preferred combination is one in which the acrylic polymer has a hydroxyl group and the compound has an isocyanate group. In this case, examples of isocyanate compounds having a carbon-carbon double bond include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate. Furthermore, acrylic polymers that are copolymerized with the hydroxyl group-containing monomers listed above or ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether can be used.

[0080] The inherent radiation-curable adhesive can use the base polymer having a carbon-carbon double bond (particularly an acrylic polymer) alone, but can also contain a photopolymerizable compound such as the radiation-curable monomer or oligomer component to the extent that the properties are not impaired. The amount of the photopolymerizable compound is usually 30 parts by weight or less, and preferably 0 to 10 parts by weight, per 100 parts by weight of the base polymer.

[0081] When the radiation-curable adhesive is to be cured by ultraviolet light or the like, it is preferable that the adhesive contains a photopolymerization initiator.

[0082] Among the above-mentioned acrylic polymers, a (meth)acrylic acid ester copolymer having a radiation-curable group introduced into the side chain is particularly preferred, more specifically, a (meth)acrylic acid ester copolymer comprising an acrylic acid ester represented by CH═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.

[0083] The amount of carbon-carbon double bonds is preferably 1.2 to 1.8 meq / g. The amount of double bonds can be quantitatively measured by a weight increase method using a bromine addition reaction in a dark place under vacuum, where the amount of carbon-carbon double bonds contained in approximately 10 g of heat-dried PSA can be determined.

[0084] The (meth)acrylic acid ester 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, etc. The double bond-containing isocyanate compounds can be used alone or in combination of two or more.

[0086] An external crosslinking agent may also be used in the radiation-curable pressure-sensitive adhesive to adjust the adhesive strength before and after irradiation. Specific examples of external crosslinking methods include 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 an external crosslinking agent is used, its amount is determined appropriately based on the balance with the base polymer to be crosslinked and the intended use of the pressure-sensitive adhesive. The amount of external crosslinking agent used is generally 20 parts by weight or less (preferably 0.1 to 10 parts by weight) per 100 parts by weight of the base polymer. Furthermore, the radiation-curable pressure-sensitive adhesive may contain, as necessary, various conventionally known additives, such as tackifiers, antioxidants, and foaming agents, in addition to the above components.

[0087] Furthermore, although the adhesive tape for wafer processing is applied to the polished surface of the wafer prior to peeling off the support member after backside grinding and polishing of the wafer, there has been a problem in that if the adhesive tape for wafer processing is applied to the wafer surface immediately after backside grinding and before oxide film formation, it becomes difficult to peel off thereafter. Therefore, it is preferable to add polypropylene oxide to the adhesive of the second adhesive layer to make peeling easier even when the adhesive tape is applied to the wafer surface immediately after backside grinding and before oxide film formation.

[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 more than 3,000 and not more than 10,000, more preferably 4,000 to 10,000. If the number-average molecular weight of the polypropylene oxide is too high, the affinity between the polypropylene oxide and the acrylic polymer (X) is poor, resulting in contamination of the adherend. If the number-average molecular weight of the polypropylene oxide is too low, 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 viewpoint of preventing wafer contamination, preferred is a polyoxypropylene-glyceryl ether having a number-average molecular weight of more than 3000 and not more than 10000, more preferably 4000 to 10000. By using a 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, increasing the probability that the polypropylene oxide will be incorporated into a crosslinked structure by reaction with a crosslinking agent such as polyisocyanate, thereby reducing the risk of the polypropylene oxide migrating to the wafer interface and contaminating the wafer surface.

[0090] Examples of polypropylene oxides 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.), and Preminol S4011 (number average molecular weight 10,000) (trade name, manufactured by Asahi Glass Co., Ltd.). Examples of polyoxypropylene glyceryl ethers 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.), and Preminol S3011 (number average molecular weight 10,000) (trade name, manufactured by Asahi Glass Co., Ltd.), but are not limited thereto.

[0091] The amount of polypropylene oxide having a number-average molecular weight of greater than 3,000 and not greater than 10,000 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, per 100 parts by mass of the base polymer. If the amount of polypropylene oxide is too small, when the adhesive tape for wafer processing is applied to an unstable polished wafer surface in which a native oxide film is not formed entirely, it becomes impossible to efficiently pick up thin semiconductor chips from a large-diameter wafer. If the amount of polypropylene oxide is too large, the adhesiveness before radiation curing becomes insufficient, causing the edges of the chips to peel off during dicing and resulting in cutting dust adhering to the backside of the chips.

[0092] In the present invention, the phrase "a base film, a first pressure-sensitive adhesive layer, and a second pressure-sensitive adhesive layer laminated in this order" also includes an embodiment in which another layer is laminated between the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer. In this case, the pressure-sensitive adhesive layer in contact with the base film is composed of the first pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer to which the semiconductor wafer is attached is composed of the second pressure-sensitive adhesive layer.

[0093] The thickness of the first adhesive layer is preferably 5 μm to 70 μm, more preferably 8 μm to 50 μm, and even more preferably 10 μm to 30 μm. If the adhesive layer is thinner than 5 μm, it may not be able to exhibit sufficient adhesive strength. 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, making it impossible to separate the wafer into chips. Furthermore, if the adhesive layer is thicker than 30 μm, the parallel ray transmittance of the adhesive tape for wafer processing may decrease.

[0094] There are no particular limitations on the method for forming the second adhesive layer on the first adhesive layer or another layer. The adhesive composition for the second adhesive layer described above can be applied to a release liner (e.g., a plastic film or sheet coated with a release agent) to form the second adhesive layer, and then laminated onto the first adhesive layer or another layer provided on a base film, thereby obtaining an adhesive tape for wafer processing.

[0095] The storage modulus G' of the first pressure-sensitive adhesive layer is preferably higher than the storage modulus G' of the second pressure-sensitive adhesive layer. The storage modulus G' is measured by preparing a plurality of pressure-sensitive adhesive layers formed on known release films, laminating two layers, peeling off the release film on one side, and laminating another layer, repeatedly to prepare a test piece with a thickness of 1 to 2 mm, and measuring the storage modulus G' with a dynamic viscoelasticity measuring device at 23°C and a frequency of 1 Hz. The storage modulus is measured for the pressure-sensitive adhesive layer before irradiation.

[0096] The storage modulus G' of the first pressure-sensitive adhesive layer is 5×10 4 Pa~100×10 4 Pa is preferable, and 5×10 4 ~80×10 4 Pa, more preferably 10 × 10 4 ~70×10 4 The storage modulus G' of the first pressure-sensitive adhesive layer is 30×10 4 If the surface tension is 0.05 Pa or more, the solvent resistance is sufficient, and when the adhesive is dissolved and washed with a solvent to peel the support member from the wafer, wrinkles are generated in the base film, which causes stress to be applied to the pressure-sensitive adhesive layer, preventing a decrease in the adhesive strength of the pressure-sensitive adhesive layer, and the wafer can be sufficiently held. Furthermore, even if the second pressure-sensitive adhesive layer is dissolved in a solvent, the first pressure-sensitive adhesive layer holds the second pressure-sensitive adhesive layer, preventing the second pressure-sensitive adhesive layer from falling off and contaminating the wafer, thereby preventing a decrease in yield.

[0097] The storage modulus G' of the second adhesive layer is 5×10 4 Pa~40×10 4 Pa is preferable, and 5×10 4 ~20×10 4 Pa, more preferably 5×10 4 ~10×10 4 The storage modulus G' of the second pressure-sensitive adhesive layer is 10×10 4 If the pressure is higher than Pa, in the case of a wafer having steps on its surface, the ability to conform to the steps may be insufficient, and the wafer may not be held sufficiently.

[0098] The wafer processing adhesive tape preferably has a residual solvent content of 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. If the residual solvent content is 1% m / m or less, when the adhesive bonding the support member to the wafer is dissolved with a solvent, the support member is peeled off, and the remaining adhesive on the wafer is washed away, wrinkles are generated in the base film of the wafer processing adhesive tape, which causes stress on the adhesive layer and a decrease in adhesive strength of the adhesive layer. Therefore, the wafer can be sufficiently held. Furthermore, even if the second adhesive layer of the wafer processing adhesive tape is dissolved by a solvent, the first adhesive layer holds the second adhesive layer, preventing the second adhesive layer from falling off and contaminating the wafer and reducing yield.

[0099] <Measurement of residual solvent amount> After preparing the adhesive tape for wafer processing (after tape formation), cut it into 40 mm squares, peel off the release liner, add 1 mL of p-menthane dropwise, leave it for 30 minutes, discard the solvent, dry it at room temperature for 30 minutes, and then immerse 1.0 g of the cut adhesive layer sample in 10 mL of acetone. The supernatant is measured by gas chromatography-mass spectrometry (GC-MS) under the following conditions. [Analysis conditions] Injection volume: 1μL Column: db-1 0.25mm x 30m Inj: 200°C (hold at 40°C for 4 minutes, then increase to 200°C at 20°C / min) He flow rate: 1.0mL / min

[0100] In order to keep the amount of residual solvent at 1%, m / m or less, it is advisable to set the glass transition temperature of the base polymer of the second pressure-sensitive adhesive layer to -20°C or higher.

[0101] If necessary, a synthetic resin film, which is usually used as a separator, may be attached to the adhesive layer side of the wafer processing adhesive tape to protect the adhesive layer until it is put into practical use. Examples of materials for the synthetic resin film include synthetic resin films such as polyethylene, polypropylene, and polyethylene terephthalate, as well as 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, as needed, to improve its releasability from the adhesive layer. The thickness of the synthetic resin film is usually 10 to 100 μm, preferably about 25 to 50 μm.

[0102] (Dissolving adhesive with solvent and cleaning wafers) When peeling a wafer from a support member, a wafer processing adhesive tape and a ring frame are applied to the side of the wafer that does not have the support member attached. The wafer and support member supported by the wafer processing adhesive tape and ring frame are then immersed in an organic solvent to dissolve the adhesive that attached the support member to the wafer, peeling the support member, and cleaning the adhesive-covered surface of the wafer. Other methods for peeling a wafer from a support member include heating to soften the adhesive and sliding the support member to peel it off, and irradiating the support member with laser light to decompose the adhesive and peel the support member. Even with these methods, adhesive or its decomposition products may remain on the wafer surface after peeling the support member. To remove these residues, the wafer supported by the wafer processing adhesive tape and ring frame is cleaned by immersing the wafer in an organic solvent or by rotating the wafer while spraying the organic solvent on it.

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

[0104] [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, An adhesive tape for wafer processing, characterized in that the glass transition temperature of the base polymer is -20°C or higher.

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

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

[0107] [4] The adhesive tape for wafer processing according to any one of [1] to [3], 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.

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

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

[0110] EXAMPLES The present invention will now be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[0111] (1) Creating the base film <Base film 1> An ethylene-vinyl acetate copolymer (manufactured by NUC Corporation under the trade name "NUC-3660") was used, which was melted at 140°C and extruded using an extruder to have a thickness of 80 µm, thereby preparing a substrate film 1. <Base film 2> Ethylene-methacrylic acid-(2-methyl-propyl acrylate)-Zn++ ionomer resin (manufactured by DuPont-Mitsui Polychemicals Co., Ltd., product name "Himilan AM7316") was melted at 140°C and molded using an extruder to a thickness of 350 μm to produce substrate film 2. <Base film 3> Polypropylene (manufactured by Prime Polymer Co., Ltd., product name "F227D") was melted at 140°C and extruded using an extruder to form a film having a thickness of 70 µm, thereby preparing a substrate film 3.

[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. 2-Methacryloyloxyethyl isocyanate was then added, and the terminal OH groups of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer reacted with the NCO groups of 2-methacryloyloxyethyl isocyanate to obtain an acrylic polymer as a base polymer, in which the repeating units of the main chain were linked to residues containing a (meth)acrylic monomer moiety with a radiation-curable carbon-carbon double bond-containing group. The glass transition temperature of this acrylic polymer was measured using a differential scanning calorimeter (DSC) and found to be -20°C. Acrylic pressure-sensitive adhesive 1 was obtained by adding 2 parts by weight of a polyisocyanate compound (manufactured by Tosoh Corporation, product name "Coronate L") and 1.5 parts by weight of a photopolymerization initiator (manufactured by BASF, product name "Irgacure 184") to 100 parts by weight of the acrylic polymer and mixing them.

[0113] <Adhesive 2> Nichigo Polyester (registered trademark) S-0097S55EO manufactured by Mitsubishi Chemical Corporation was prepared as an adhesive containing a polyester polymer as a base polymer. The glass transition temperature of the polyester polymer serving as the base polymer was 1°C. 3 parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "Coronate L") was added to and mixed with 100 parts by mass of the polyester polymer to obtain polyester 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. 2-Methacryloyloxyethyl isocyanate was then added, and the terminal OH groups of the 2-hydroxyethyl acrylate side chains of this acrylic copolymer reacted with the NCO groups of the 2-methacryloyloxyethyl isocyanate to obtain an acrylic polymer as the base polymer, in which the repeating units of the main chain contained residues containing (meth)acrylic monomer moieties bearing radiation-curable carbon-carbon double bond-containing groups. The glass transition temperature of this acrylic polymer was measured by differential scanning calorimetry (DSC) to be -50°C. Acrylic adhesive 3 was obtained by adding and mixing 2 parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, product name "Coronate L") and 1.5 parts by mass of a photopolymerization initiator (manufactured by BASF, product name "Irgacure 184") to 100 parts by mass of an acrylic polymer.

[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. 2-Methacryloyloxyethyl isocyanate was then added to the copolymer, reacting the terminal OH groups of the 2-hydroxyethyl acrylate side chain with the NCO groups of the 2-methacryloyloxyethyl isocyanate to obtain an acrylic polymer as a base polymer, in which the repeating units of the main chain are linked to residues containing a (meth)acrylic monomer moiety with a radiation-curable carbon-carbon double bond-containing group. The glass transition temperature of this acrylic polymer was measured using a differential scanning calorimeter (DSC) and found to be −64°C. Acrylic pressure-sensitive adhesive 4 was obtained by adding 2 parts by weight of a polyisocyanate compound (manufactured by Tosoh Corporation, product name: Coronate L) and 1.5 parts by weight of a photopolymerization initiator (manufactured by BASF, product name: Irgacure 184) to 100 parts by weight of the acrylic polymer and mixing them.

[0116] <Adhesive 5> An acrylic copolymer consisting of butyl acrylate (70 wt%), methacrylic acid (1 wt%), and 2-hydroxyethyl acrylate (29 wt%) was prepared. 2-Methacryloyloxyethyl isocyanate was then added, and the terminal OH groups of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer reacted with the NCO groups of 2-methacryloyloxyethyl isocyanate to obtain an acrylic polymer as a base polymer, in which the repeating units of the main chain were linked to residues containing a (meth)acrylic monomer moiety with a radiation-curable carbon-carbon double bond-containing group. The glass transition temperature of this acrylic polymer was measured using a differential scanning calorimeter (DSC) and found to be −45°C. Acrylic Pressure-Sensitive Adhesive 5 was obtained by adding 2 parts by weight of a polyisocyanate compound (manufactured by Tosoh Corporation, product name: Coronate L) and 1.5 parts by weight of a photopolymerization initiator (manufactured by BASF, product name: Irgacure 184) to 100 parts by weight of the acrylic polymer and mixing them.

[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. The glass transition temperature of this acrylic polymer was measured using a differential scanning calorimeter (DSC) and found to be -10°C. Two parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, product name "Coronate L") were added to 100 parts by mass of the acrylic polymer and mixed to obtain acrylic pressure-sensitive 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. 2-Methacryloyloxyethyl isocyanate was then added, and the terminal OH groups of the 2-hydroxyethyl acrylate side chains of this acrylic copolymer reacted with the NCO groups of 2-methacryloyloxyethyl isocyanate to obtain an acrylic polymer as the base polymer, in which the repeating units of the main chain contained residues containing (meth)acrylic monomer moieties bearing radiation-curable carbon-carbon double bond-containing groups. The glass transition temperature of this acrylic polymer was measured by differential scanning calorimetry (DSC) to be -30°C. Acrylic adhesive 7 was obtained by adding and mixing 4 parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, product name "Coronate L") and 1.5 parts by mass of a photopolymerization initiator (manufactured by BASF, product name "Irgacure 184") to 100 parts by mass of an acrylic polymer.

[0119] (3) Preparation of adhesive tape for wafer processing Example 1 The adhesive composition obtained by dissolving and stirring adhesive 1 in ethyl acetate was coated onto a release liner made of a release-treated polyethylene terephthalate film to a dry thickness of 10 μm, dried at 110°C for 3 minutes, and then bonded to base film 1 to form a first adhesive layer on the base film. The adhesive composition obtained by dissolving and stirring adhesive 4 in ethyl acetate was coated onto a release liner made of a release-treated polyethylene terephthalate film to a dry thickness of 10 μm, and then dried at 110°C for 3 minutes to form a second adhesive layer. The release liner was then peeled from the first adhesive layer, and the second adhesive layer was laminated onto the first adhesive layer, thereby producing an adhesive tape for wafer processing according to Example 1.

[0120] <Examples 2 to 9 and Comparative Examples 1 to 5> Adhesive tapes for wafer processing according to Examples 2 to 9 and Comparative Examples 1 to 5 were produced in the same manner as in Example 1, except that the base film and adhesive layer were combined as shown in Tables 1 and 2.

[0121] <Measurement of residual solvent amount> After preparing the wafer processing adhesive tape (after tape preparation), the tape was cut into 40 mm square pieces, the release liner was peeled off, 1 mL of p-menthane was added dropwise, and the tape was left to stand for 30 minutes. After that, the solvent was discarded and the tape was allowed to dry at room temperature for 30 minutes. 1.0 g of the cut adhesive layer sample was immersed in 10 mL of acetone. The supernatant was analyzed by gas chromatography-mass spectrometry (GC-MS) under the following conditions. The results are shown in Tables 1 and 2. [Analysis conditions] Injection volume: 1μL Column: db-1 0.25mm x 30m Inj: 200°C (hold at 40°C for 4 minutes, then increase to 200°C at 20°C / min) He flow rate: 1.0mL / min

[0122] <Measurement of storage modulus> The storage modulus of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer according to the examples and comparative examples was measured as follows. The pressure-sensitive adhesive was coated onto a release film so that the thickness after drying was 20 μm, and dried at 110°C for 3 minutes to form a pressure-sensitive adhesive layer. 100 sheets were prepared, the release film was peeled off, and the layer was laminated to a thickness of 2.0 mm. Then, a test piece was punched out to a diameter of 8 mm to prepare a test piece. This test piece was fed into a dynamic viscoelasticity measuring machine (manufactured by Rheometrics) and the storage modulus G' was measured at 23°C and a frequency of 1 Hz. The results are shown in Tables 1 and 2.

[0123] <Evaluation of Solvent Resistance> The wafer processing adhesive tapes of the Examples and Comparative Examples were attached to an 8-inch wafer and fixed to a ring frame. Afterwards, the tape was spin-cleaned by rotating at 2000 rpm while spraying p-menthane as an organic solvent onto the wafer side. After cleaning and drying, the adhesive layer on the wafer processing dicing tape in the areas where the wafer was not attached was observed. Products in which dissolution or swelling of the second adhesive layer was observed but no part of it was still held by the first adhesive layer were evaluated as good products with a circle. Products in which the second adhesive layer had dissolved or swelled and fallen off the first adhesive layer, or where wrinkles had developed in the base film, were evaluated as defective products with a cross. 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 example has a first adhesive layer and a second adhesive layer laminated in that order on a base film, and the first adhesive layer is formed from 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, so it achieved excellent results 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, and therefore showed poor results in the evaluation of solvent resistance.

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 PSA layer is formed from a PSA composition containing an acrylic polymer or a polyester polymer as a base polymer, The adhesive tape for wafer processing is characterized in that the glass transition temperature of the base polymer is −20° C. or higher.

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. 3. The adhesive tape for wafer processing according to claim 1, wherein the storage modulus of the first adhesive layer is higher than the storage modulus of the second adhesive layer.

6. 3. The adhesive tape for wafer processing according to claim 1, which is used in a wafer processing method including a step of cleaning the wafer with a solvent.

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