Adhesive tape for wafer processing

Abstract

This invention provides a wafer processing adhesive tape that, even when used in wafer processing steps employing support members, allows for proper wafer retention even after solvent dissolution of the adhesive that holds the support members to the wafer, thereby peeling off the support members, or after cleaning away residual adhesive on the wafer, preventing yield reduction due to wafer contamination. The wafer processing adhesive tape of this invention is characterized by being a wafer processing adhesive tape formed by sequentially stacking at least a substrate film, a first adhesive layer, and a second adhesive layer, wherein the first adhesive layer is formed of an adhesive composition comprising 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] This invention relates to an adhesive tape for wafer processing used in wafer dicing. More specifically, it relates to an adhesive tape for wafer processing used in wafer processing methods that include a solvent-based wafer cleaning process. Background Technology

[0002] On the back side of a wafer formed by thin-film fabrication wiring patterns, protective tape is typically applied to the patterned surface to protect the wafer and secure it. Then, thin-film processing such as grinding and polishing is performed on the back side. This protective tape is generally made by coating a substrate composed of plastic film with acrylic adhesives. However, in recent years, with the miniaturization and thinning of IC cards and mobile phones, chip thickness has been required to be below 50μm. In processes using traditional protective tape, the tape alone cannot support the wafer. Wafer handling becomes difficult due to warping after grinding and deflection when stored in a wafer cassette, hindering the automation of operation and transport.

[0003] To address this issue, a proposed method involves attaching a glass substrate, ceramic substrate, or silicon wafer substrate to the wafer using an adhesive to provide support for the wafer (see, for example, Patent Document 1). In this way, by using support members such as glass substrates, ceramic substrates, or silicon wafer substrates, the wafer's maneuverability is significantly improved, and automated handling becomes possible. Furthermore, the support members can also be used to support the wafer during the back-side wiring and bump formation processes.

[0004] When operating wafers using support members, a process of peeling the support members from the wafer is required. Peeling the support members is generally performed by dissolving the adhesive with a solvent and then cleaning. In addition to the methods mentioned above, other methods for peeling the wafer from the support members include: heating to soften the adhesive, causing the support member to slide and peel off; and using laser irradiation to decompose the adhesive, thereby peeling off the support member. When using these methods, adhesive and its decomposition products may remain on the wafer surface after peeling off the support member. Therefore, to remove these residues, the wafer is cleaned by immersing it in an organic solvent, or by rotating the wafer while blowing organic solvent onto it.

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

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2006-135272

[0009] Patent Document 2: Japanese Patent Application Publication No. 2007-100064 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, as mentioned above, when the wafer thickness becomes 50 μm or less, wafer processing becomes very difficult for individual wafers due to warping after grinding and deflection when stored in a wafer cassette. Therefore, it is common practice to apply wafer processing adhesive tape to the ground surface of the wafer after grinding and polishing on the back side, and before peeling off the support member, to support and fix it to the ring frame. Therefore, the solvent-based dissolution and cleaning of the adhesive during the peeling off of the support member is performed with the wafer attached to the wafer processing adhesive tape. High solvent resistance is required for the wafer processing adhesive tape.

[0012] However, conventional wafer processing adhesive tapes, such as the wafer processing adhesive tape described in Patent Document 2, suffer from insufficient solvent resistance, resulting in reduced adhesion of the adhesive layer and an inability to adequately hold the wafer. Furthermore, the adhesive layer of the wafer processing adhesive tape dissolves in solvents, contaminating the wafer and reducing yield.

[0013] Therefore, the object of the present invention is to provide an adhesive tape for wafer processing that, even when used in a wafer processing step that employs a support member, allows for the proper holding of the wafer by dissolving the adhesive that bonds the support member to the wafer with a solvent, thereby peeling off the support member, or by cleaning off any adhesive residue on the wafer, thus preventing a decrease in yield due to wafer contamination.

[0014] Methods for solving problems

[0015] Through repeated research efforts to achieve the above objectives, the inventors discovered that the glass transition temperature of the substrate polymer in the adhesive layer is related to its solvent resistance. This invention is based on this discovery.

[0016] That is, the wafer processing adhesive tape of the present invention is characterized in that it is a wafer processing adhesive tape formed by sequentially stacking a substrate film, a first adhesive layer and a second adhesive layer, wherein the first adhesive layer is formed by an adhesive composition comprising 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.

[0017] The aforementioned adhesive tape for wafer processing preferably has a substrate film formed from polyolefin resin.

[0018] In addition, the thickness of the substrate film of the above-mentioned wafer processing adhesive tape is preferably 70 to 350 μm.

[0019] In addition, the residual solvent content of the above-mentioned wafer processing adhesive tape after adding 1 ml of menthol to the surface of the second adhesive layer and letting it stand for 30 minutes is preferably less than 1% m / m.

[0020] Furthermore, the energy storage modulus of the first adhesive layer of the aforementioned wafer processing adhesive tape is preferably higher than that of the second adhesive layer.

[0021] Furthermore, the aforementioned wafer processing adhesive tape is preferably used in wafer processing methods that include a solvent-based wafer cleaning process.

[0022] Invention Effects

[0023] According to the present invention, even when used in a wafer processing step that employs a support member, the wafer can be properly held in place by dissolving the adhesive bonded to the wafer with a solvent to remove the support member, or by cleaning off any adhesive residue on the wafer, thus preventing a decrease in yield due to wafer contamination. Detailed Implementation

[0024] The following is a detailed description of how the present invention is implemented.

[0025] In embodiments of the present invention, the wafer processing adhesive tape has at least a first adhesive layer and a second adhesive layer sequentially stacked on at least one side of the substrate film.

[0026] It should be noted that the substrate film, the first adhesive layer, and the second adhesive layer are preferably cut (pre-cut) into shapes corresponding to the ring frame used when monolithic wafers. Furthermore, the wafer processing adhesive tape of the present invention can also be cut into wafer segments, or it can be formed by winding a diaphragm having multiple strips cut into wafer segments into a roll.

[0027] The following is a detailed description of each component of the wafer processing adhesive tape according to this embodiment.

[0028] (Substrate film)

[0029] Regarding the resin constituting the substrate film, for example, polypropylene, high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ethylene-propylene copolymer, propylene copolymer, ethylene-propylene-diene copolymer sulfurized, polybutene, polybutadiene, polymethylpentene, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid methyl copolymer, ethylene-(meth)acrylic acid ethyl ester copolymer, ethylene-(meth)acrylic acid butyl ester 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 hydrogenated or modified varieties, etc.

[0030] In particular, the substrate film is preferably formed of a polyolefin resin because it exhibits excellent tensile strength during expansion. Examples of polyolefin resins include individual polymers 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, and ionomers, or mixtures thereof.

[0031] In particular, when using an ionomer substrate film, uniform physical properties can be obtained relative to the feed direction and width direction of the substrate film. Therefore, when performing expansion-based segmentation, the spacing between monolithic chips can be made uniform.

[0032] It should be noted that the substrate film is not limited to a single layer; it can be a multilayer structure with two or more resins stacked, or a single resin can be stacked in two or more layers. From the viewpoint of further enhancing the properties of each resin, stacking a single resin is preferred, while stacking two or more resins is preferred in terms of compensating for their respective shortcomings.

[0033] As a method for manufacturing multilayer substrate films, conventional methods such as extrusion and lamination can be used. When using lamination, an adhesive can be inserted between the layers. Conventional adhesives can be used as the adhesive.

[0034] The thickness of the substrate film is preferably 70 to 350 μm. More preferably, it is 250 to 300 μm. When it is 350 μm or more, there is a concern that the chip cannot be picked up from the wafer processing adhesive tape. When it is thinner than 70 μm, there is a concern that the wafer processing adhesive tape will break during expansion.

[0035] To improve adhesion, corona treatment or primer treatment may be applied to the surface of the substrate film that contacts the first adhesive layer.

[0036] (First adhesive layer)

[0037] The adhesive composition forming the first adhesive layer may include 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 fluoropolymers known in the field of adhesives, and may include at least an acrylic polymer or a polyester polymer as the base polymer.

[0038] The term "acrylic polymer" refers to a polymer in which the monomer units constituting the polymer include monomer units 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 will also be 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 an acrylic polymer, 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 can be listed. Furthermore, the term "(meth)acryloyl" includes both acryloyl and methacryloyl groups. Similarly, the term "(meth)acrylate" includes both acrylate and methacrylate, and the term "(meth)acryloyl" includes both acryloyl and methacryloyl groups.

[0039] The term "polyester polymer" refers to polymers obtained by the condensation polymerization of dicarboxylic acids and diols, which have repeating units containing ester bonds in their main chain.

[0040] The glass transition temperature of the base polymer constituting the first adhesive is -20°C or higher. Here, glass transition temperature refers to the glass transition temperature measured using a 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 peeling the support member from the wafer, and dissolving and cleaning the adhesive with a solvent, stress on the adhesive layer due to wrinkles in the substrate film can be prevented, thus reducing the adhesive strength and preserving the wafer. Furthermore, since the first adhesive layer retains the second adhesive layer even if the second adhesive layer dissolves in the solvent, the second adhesive layer is prevented from detaching and contaminating the wafer, thus preventing a decrease in yield. More preferably, the glass transition temperature of the base polymer constituting the adhesive is greater than -15°C and less than 1°C, and even more preferably greater than -10°C and less than 1°C.

[0041] The first adhesive layer is preferably a radiation-cured type that is cured by irradiation. As the adhesive composition constituting the radiation-cured first adhesive layer, a polymer constituting the adhesive and a radiation-polymerizable compound can be used, or a polymer incorporating functional groups (preferably vinyl unsaturated groups) that are polymerizable by irradiation can be used. To promote polymerization by irradiation, a photopolymerization initiator is preferably included. Additionally, the inclusion of a crosslinking agent is also preferred. By incorporating monomers having functional groups that can react with the crosslinking agent into the polymer constituting the adhesive, the film hardness and gel fraction can be adjusted. Furthermore, additives or additives other than those mentioned above may be included as needed. The following will describe this in more detail.

[0042] Examples of acrylic polymers include acrylic polymers that use one or more of the following monomer components: alkyl methacrylates (e.g., methyl esters, ethyl esters, propyl esters, isopropyl esters, butyl esters, isobutyl esters, sec-butyl esters, tert-butyl esters, pentyl esters, isopentyl esters, hexyl esters, heptyl esters, octyl esters, 2-ethylhexyl esters, isooctyl esters, nonyl esters, decyl esters, isodecanyl esters, undecyl esters, dodecyl esters, tridecyl esters, tetradecyl esters, hexadecyl esters, octadecyl esters, eicosyl esters, etc., in the form of straight-chain or branched chains with 1 to 30 carbon atoms, especially 4 to 18 carbon atoms) and cycloalkyl methacrylates (e.g., cyclopentyl esters, cyclohexyl esters, etc.). It should be noted that the term "(meth)acrylate" refers to acrylates and / or methacrylates, and has the exact same meaning as "(methyl)" in this invention.

[0043] Regarding acrylic polymers, for the purpose of modifying cohesiveness, heat resistance, etc., other monomer components that can be included and copolymerized with the aforementioned alkyl or cycloalkyl methacrylates may be included as needed. Examples of such monomer components include, for instance, acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and other monomers containing carboxyl groups; 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-hydroxyethyl (meth)acrylate. Monomers containing hydroxyl groups, such as hydroxydecyl ester, 12-hydroxylaurate (meth)acrylate, and (4-hydroxymethylcyclohexyl)meth(meth)acrylate; monomers containing sulfonic acid groups, such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acryloylamide-2-methylpropane sulfonic acid, (meth)acryloylamide propane sulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalene sulfonic acid; monomers containing phosphate groups, such as 2-hydroxyethylacryloyl phosphate; and monomers such as acryloylamide and acrylonitrile. One or more of these copolymerizable monomers may be used. Preferably, the amount of these copolymerizable monomers used is less than 40% by weight of all monomer components.

[0044] Furthermore, regarding acrylic polymers, in order to facilitate crosslinking, multifunctional monomers may be included as copolymerizing monomer components as needed. Examples of such multifunctional monomers include hexanediol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, pentaerythritol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexamethacrylate, epoxy methacrylate, polyester methacrylate, and urethane methacrylate. One or more of these multifunctional monomers may be used. From the perspective of adhesive properties, the amount of multifunctional monomer used is preferably 30% by weight or less of the total monomer composition.

[0045] The preparation of acrylic polymers can be carried out by appropriate methods such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization for mixtures of one or more component monomers.

[0046] In addition, to control the crosslinking density of the first adhesive layer, appropriate methods can be used, such as: crosslinking treatment using suitable external crosslinking agents like polyfunctional isocyanate compounds, polyfunctional epoxy compounds, melamine compounds, metal salt compounds, metal chelating agent compounds, amino resin compounds, or peroxides; or crosslinking treatment by mixing low-molecular-weight compounds with two or more carbon-carbon double bonds and subjecting the crosslinking to radiation. When using an external crosslinking agent, its amount is determined appropriately based on the balance with the substrate polymer to be crosslinked, and further, based on the intended use of the adhesive. Generally, about 20 parts by weight or less is used relative to 100 parts by weight of the substrate polymer, and more preferably, 0.1 to 20 parts by weight. It should be noted that, from the viewpoint of preventing degradation, various adhesive additives, anti-aging agents, and other additives may be used in the adhesive as needed, in addition to the above-mentioned components.

[0047] The adhesive constituting the first adhesive layer is preferably a radiation-curing adhesive. Examples of radiation-curing adhesives include those that incorporate radiation-curing monomeric components and radiation-curing oligomeric components.

[0048] Examples of suitable radiocurable monomers include urethane (meth)acrylates, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and 1,4-butanediol di(meth)acrylate. One or more of these monomers may be used in combination.

[0049] Furthermore, various oligomers such as urethane-based, polyether-based, polyester-based, polycarbonate-based, and polybutadiene-based oligomers can be used as the radiation-curable component, with a molecular weight ranging from approximately 100 to 30,000 being suitable. The amount of radiation-curable monomer and oligomer components can be appropriately determined according to the type of the first adhesive layer, reducing the adhesive strength of the first adhesive layer. Generally, the amount is approximately 5 to 500 parts by weight, preferably 70 to 150 parts by weight, relative to 100 parts by weight of the base polymer such as an acrylic polymer constituting the adhesive.

[0050] In addition to the aforementioned additive-type radiation-curing adhesives, intrinsic radiation-curing adhesives, in which radiation-curing groups are incorporated into the polymer side chains or main chains or at the ends of the main chains as the base polymer, can also be cited as examples. Intrinsic radiation-curing adhesives are preferred because they do not require or contain large amounts of oligomer components as low-molecular-weight components; therefore, these oligomer components do not migrate into the adhesive over time, allowing the formation of a stable first adhesive layer.

[0051] The base polymer for incorporating radiation-curable groups is not particularly limited to those having carbon-carbon double bonds and adhesive properties. As such a base polymer, an acrylic polymer as the basic backbone is preferred. Examples of acrylic polymers exemplified above can be cited as examples of the basic backbone of an acrylic polymer.

[0052] There are no particular limitations on the methods for introducing radiocurable groups into acrylic polymers; various methods can be used to introduce radiocurable groups into the polymer side chains, which is easy in terms of molecular design. For example, one method is to first copolymerize monomers with functional groups into acrylic polymers, and then carry out condensation or addition reactions of compounds with functional groups and carbon-carbon double bonds that can react with those functional groups while maintaining the radiocurability of the carbon-carbon double bonds.

[0053] Examples of combinations of these functional groups include carboxylic acid group and epoxy group, carboxylic acid group and aziridinyl group, hydroxyl group and isocyanate group, etc. Among these combinations of functional groups, the combination of hydroxyl group and isocyanate group is preferred due to the ease of reaction traceability. Furthermore, if the combination of these functional groups results in the formation of the above-mentioned acrylic polymer having a carbon-carbon double bond, the functional group can be on either side of the acrylic polymer and the above-mentioned compound. However, for the preferred combination described above, it is preferable that the acrylic polymer has a hydroxyl group and the above-mentioned compound has an isocyanate group. In this case, examples of isocyanate compounds having a carbon-carbon double bond include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, etc. Additionally, as the acrylic polymer, copolymers of the monomers containing hydroxyl groups exemplified above, or ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether are used.

[0054] The intrinsically radiocurable adhesive can use the aforementioned base polymer (especially acrylic polymers) with carbon-carbon double bonds alone, but it can also be combined with the aforementioned photopolymerizable compounds such as radiocurable monomer components and oligomer components to a degree that does not degrade the properties. The amount of the photopolymerizable compound is usually in the range of 30 parts by weight or less relative to 100 parts by weight of the base polymer, preferably in the range of 0 to 10 parts by weight.

[0055] In radiation-curing adhesives, when cured by ultraviolet light or the like, it is preferable to contain a photopolymerization initiator.

[0056] Among the aforementioned acrylic polymers, especially (meth)acrylate copolymers with radiation-curable groups introduced into the side chains, more specifically, (meth)acrylate copolymers comprising an acrylate represented by CH2=CHCOOR (where R is an alkyl group having 4 to 18 carbon atoms), a monomer containing hydroxyl groups, and an isocyanate compound having a free radical reactive carbon-carbon double bond within the molecule are preferred.

[0057] The amount of carbon-carbon double bonds is preferably 1.2 to 1.8 meq / g. Regarding the amount of double bonds, the amount of carbon-carbon double bonds contained in approximately 10g of the heated and dried binder can be quantitatively determined by the gravimetric method of bromine addition reaction in a vacuum in the dark.

[0058] The above-mentioned (meth)acrylate copolymer may, as needed, contain units corresponding to other monomer components.

[0059] Examples of isocyanate compounds containing double bonds include methacryloyl isocyanate, acryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate. Two or more isocyanate compounds containing double bonds can be used alone or in combination.

[0060] In addition, external crosslinking agents can be appropriately used in radiation-curing adhesives to adjust the adhesive strength before or after radiation irradiation. Specific methods for external crosslinking include adding polyisocyanate compounds, epoxy compounds, aziridine compounds, melamine-based crosslinking agents, etc., to induce a reaction. When using an external crosslinking agent, its amount is appropriately determined by balancing it with the base polymer to be crosslinked, and further by its intended use as an adhesive. Generally, the amount of external crosslinking agent used is 20 parts by weight or less (preferably 0.1 to 10 parts by weight) relative to 100 parts by weight of the base polymer. Furthermore, in addition to the above-mentioned components, various conventionally known adhesive additives, anti-aging agents, foaming agents, etc., can be added to radiation-curing adhesives as needed.

[0061] The polyester used in polyester-based polymers is preferably a polyester obtained by polycondensation of a carboxylic acid component with two or more functions and a diol component, wherein the weight-average molecular weight of the polyester is 8,500 to 50,000. Furthermore, the polyester preferably contains at least a carboxylic acid component with two or more functions, wherein the carboxylic acid component is a dicarboxylic acid component having two carboxyl groups in its molecule.

[0062] There are no particular limitations on the dicarboxylic acids mentioned above. Examples include sebacic acid derived from castor oil or 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, dodecanoic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, maleic acid, maleic anhydride, itaconic acid, citraconic acid, etc. (aliphatic or alicyclic dicarboxylic acids), or terephthalic acid, isophthalic acid, phthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 2,2'-diphenyldicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, etc. Dimer acids, in particular, have low glass transition temperatures, allowing for the design of flexible adhesives, thus exhibiting good wetting properties and are therefore preferred. Furthermore, dimer acids are derived from non-petroleum materials (plant-based raw materials), thus being environmentally friendly and useful. These can be used individually or in combination of two or more.

[0063] In addition, the aforementioned polyester contains a diol component, which preferably contains at least two hydroxyl groups (hydroxyl groups) in the molecule. Aliphatic diols or polyether diols are preferred.

[0064] As the aforementioned aliphatic diols, aliphatic diols having 3 to 10 alkylene groups are particularly preferred. There are no particular limitations on the aliphatic diols having 3 to 10 alkylene groups; specifically, examples include 1,2-propanediol, 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, neopentanediol, 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-cyclohexanediethanol, and 1,2-cyclohexanediethanol. These can be used individually or in combinations of two or more.

[0065] Furthermore, there are no particular limitations on the polyether glycols mentioned above, but polyether glycols with hydroxyl groups at both ends are preferred. As for the polyether glycols with hydroxyl groups at both ends, there are no particular limitations on the number-average molecular weight (Mn). Specifically, polyalkylene ether glycols such as polytetramethylene ether glycol and polytrimethylene ether glycol are preferred; 1 to 20 mol% of copolymer polyether polyols of 3-methyltetrahydrofuran and tetrahydrofuran (e.g., "PTG-L1000", "PTG-L2000", "PTG-L3500", etc. manufactured by Hodogaya Chemical Co., Ltd.); or copolymer polyether glycols of neopentyl glycol and tetrahydrofuran, etc. These can be used individually or in combination of two or more.

[0066] The above-mentioned polyester-based polycondensation is obtained by combining 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, even more preferably 1.04 to 2.60, and particularly preferably 1.06 to 2.40. When the above molar ratio is less than 1, there is a concern that the polymerized polyester (polymer) ends with carboxyl groups, making rapid crosslinking by a crosslinking agent (e.g., an isocyanate-based crosslinking agent) impossible. Furthermore, there is a concern that the adhesive layer's holding power (cohesion) may become insufficient.

[0067] Alternatively, other components besides the above-mentioned carboxylic acid components or diol components can be polymerized, or added after polymerization.

[0068] There are no particular limitations on the synthesis method of the aforementioned polyesters, and known polymerization methods can be used. It should be noted that the polymerization (condensation polymerization) reaction of the carboxylic acid component and the diol component can be carried out using a solvent, or under reduced pressure without solvent, or using conventionally known methods.

[0069] When a polyester polymer is used as the base polymer, the adhesive composition of the first adhesive layer preferably contains, together with the polyester polymer, a fatty acid ester with a molecular weight (molar molecular weight: g / mol) of 200 to 700 without functional groups. Examples of fatty acid esters include isopropyl myristate, isopropyl palmitate, methyl linoleate, and, in addition, dicarboxylic acid esters such as adipate, sebate, and phthalate. One or more of these can be used. The amount of fatty acid ester contained is 10 to 150 parts by weight relative to 100 parts by weight of the polyester polymer, 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.

[0070] In addition, the adhesive composition contains a crosslinking agent along with the aforementioned polyester polymer. There are no particular limitations on the crosslinking agent; previously known agents can be used, such as isocyanate-based crosslinking agents (e.g., polyvalent isocyanurates or polyfunctional isocyanate compounds), polyfunctional melamine compounds, polyfunctional epoxy compounds, polyfunctional oxazoline compounds, polyfunctional aziridine compounds, metal chelating agents, etc. One or more of these can be used.

[0071] In particular, isocyanate-based crosslinking agents, such as polyvalent isocyanurates and multifunctional isocyanates, which are known in the past, are preferred. Examples of polyvalent isocyanurates include polyisocyanates of hexamethylene diisocyanate. As for multifunctional isocyanate compounds, compounds having at least two or more isocyanate groups in the molecule are preferred, more preferably three or more, but there are no particular limitations. Specifically, examples include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

[0072] The thickness of the first 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 even more preferably 5 μm or more and 15 μm or less. When the adhesive layer is thinner than 5 μm, there is a concern that it may not exhibit sufficient adhesive strength. On the other hand, when the adhesive layer is thicker than 70 μm, there is a concern that the force during expansion may not be sufficiently transmitted to the wafer, making it impossible to diced the wafer into chips.

[0073] The method for forming the first adhesive layer on the substrate film is not particularly limited. For example, in addition to forming it by coating the substrate film with the adhesive composition described above by a coating method that is usually used, it can also be made by bonding the adhesive layer coated on the diaphragm to the substrate film and transferring it to the substrate film.

[0074] (Second adhesive layer)

[0075] The adhesive composition forming the second adhesive layer, as the base polymer, may be one or more of various rubber-like polymers including acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, fluoropolymers, etc., which are known in the field of adhesives.

[0076] The second adhesive layer is preferably a radiation-cured type that is cured by irradiation. As a radiation-cured adhesive composition constituting the second adhesive layer, a polymer constituting the adhesive and a radiation-polymerizable compound can be used together, or a polymer constituting the adhesive may contain radiation-polymerizable functional groups (preferably vinyl unsaturated groups). To promote polymerization under radiation, a photopolymerization initiator is preferably included. Additionally, a crosslinking agent is also preferred. By incorporating monomers having functional groups capable of reacting with the crosslinking agent into the polymer constituting the adhesive, the film hardness or gel fraction can be adjusted. Furthermore, additives or additives other than those mentioned above may be included as needed. The following describes this in more detail.

[0077] Examples of acrylic polymers include acrylic polymers that use one or more of the following monomer components: alkyl methacrylates (e.g., methyl esters, ethyl esters, propyl esters, isopropyl esters, butyl esters, isobutyl esters, sec-butyl esters, tert-butyl esters, pentyl esters, isopentyl esters, hexyl esters, heptyl esters, octyl esters, 2-ethylhexyl esters, isooctyl esters, nonyl esters, decyl esters, isodecanyl esters, undecyl esters, dodecyl esters, tridecyl esters, tetradecyl esters, hexadecyl esters, octadecyl esters, eicosyl esters, etc., in the form of straight-chain or branched chains with 1 to 30 carbon atoms, especially 4 to 18 carbon atoms) and cycloalkyl methacrylates (e.g., cyclopentyl esters, cyclohexyl esters, etc.). It should be noted that the term "(meth)acrylate" refers to acrylates and / or methacrylates, and has the same meaning as "(methyl)" in this invention.

[0078] Acrylic polymers, aimed at modifying cohesiveness, heat resistance, etc., may, as needed, contain units corresponding to other monomer components that can be copolymerized with the aforementioned alkyl or cycloalkyl methacrylates. Examples of such monomer components include, for instance, carboxyl-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic 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-hydroxyethyl (meth)acrylate. Monomers containing hydroxyl groups, such as hydroxydecyl ester, 12-hydroxylaurate (meth)acrylate, and (4-hydroxymethylcyclohexyl)meth(meth)acrylate; monomers containing sulfonic acid groups, such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acryloylamide-2-methylpropane sulfonic acid, (meth)acryloylamide propane sulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalene sulfonic acid; monomers containing phosphate groups, such as 2-hydroxyethylacryloyl phosphate; and acryloylamides and acrylonitriles. One or more of these copolymerizable monomers may be used. Preferably, the amount of these copolymerizable monomers used is less than 40% by weight of all monomer components.

[0079] Furthermore, since acrylic polymers undergo crosslinking, multifunctional monomers may be included as copolymerizing monomers as needed. Examples of such multifunctional monomers include hexanediol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, pentaerythritol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexamethacrylate, epoxy methacrylate, polyester methacrylate, and urethane methacrylate. One or more of these multifunctional monomers may be used. From the perspective of adhesive properties, the amount of multifunctional monomer used is preferably 30% by weight or less of the total monomer composition.

[0080] The preparation of acrylic polymers can be carried out by appropriate methods such as solution polymerization, emulsion polymerization, bulk polymerization, or suspension polymerization for mixtures of one or more component monomers.

[0081] In addition, to control the crosslinking density of the second adhesive layer, appropriate external crosslinking agents can be used for crosslinking treatment, such as polyfunctional isocyanate compounds, polyfunctional epoxy compounds, melamine compounds, metal salt compounds, metal chelating agent compounds, amino resin compounds, or peroxides. Alternatively, a suitable method can be used, such as mixing low-molecular-weight compounds with two or more carbon-carbon double bonds and crosslinking through radiation. When using an external crosslinking agent, its amount is appropriately determined by balancing it with the base polymer to be crosslinked, and further by considering its intended use as an adhesive. Generally, it is preferable to use about 20 parts by weight or less, or even 0.1 to 20 parts by weight, relative to 100 parts by weight of the base polymer. It should be noted that, from the viewpoint of preventing degradation, various adhesive additives, anti-aging agents, and other additives can be used in the adhesive as needed, in addition to the above-mentioned components.

[0082] As the adhesive constituting the second adhesive layer, a radiation-curing adhesive is preferred. Examples of radiation-curing adhesives include those described above, and radiation-curing adhesives with added radiation-curing monomeric or oligomeric components.

[0083] Examples of suitable radiocurable monomers include urethane (meth)acrylates, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and 1,4-butanediol di(meth)acrylate. One or more of these monomers may be used in combination.

[0084] Furthermore, various oligomers such as urethane-based, polyether-based, polyester-based, polycarbonate-based, and polybutadiene-based oligomers can be used as the radiation-curable component, with a molecular weight ranging from approximately 100 to 30,000 being suitable. The amount of radiation-curable monomer and oligomer components can be appropriately determined according to the type of the first adhesive layer, thereby reducing the adhesive strength of the first adhesive layer. Generally, relative to 100 parts by weight of the base polymer such as acrylic polymer constituting the adhesive, the amount is, for example, 5 to 500 parts by weight, preferably about 70 to 150 parts by weight.

[0085] In addition to the aforementioned additive-type radiation-curing adhesives, intrinsic radiation-curing adhesives, in which a radiation-curable group is introduced into the polymer side chain, main chain, or main chain end, can also be cited as the base polymer. Intrinsic radiation-curing adhesives are preferred because they do not require oligomer components containing or containing very little low molecular weight components, and therefore, as these oligomer components do not migrate into the adhesive over time, a stable first adhesive layer can be formed.

[0086] The base polymer for incorporating radiation-curable groups is not particularly limited to those having carbon-carbon double bonds and adhesive properties. As such a base polymer, an acrylic polymer as the basic backbone is preferred. Examples of acrylic polymers exemplified above can be cited as examples of the basic backbone of an acrylic polymer.

[0087] There are no particular limitations on the method of introducing radiocurable groups into acrylic polymers, and various methods can be used. However, introducing radiocurable groups into the polymer side chains is easier in terms of molecular design. For example, one method is to first copolymerize a monomer with a functional group with the acrylic polymer, and then directly maintain the radiocurability of the carbon-carbon double bond by condensation or addition reactions with a compound having a functional group that can react with this functional group and a carbon-carbon double bond.

[0088] Examples of combinations of these functional groups include carboxylic acid group and epoxy group, carboxylic acid group and aziridinyl group, hydroxyl group and isocyanate group, etc. Among these combinations of functional groups, the combination of hydroxyl group and isocyanate group is preferred due to the ease of reaction traceability. In addition, if the combination of these functional groups results in the formation of the above-mentioned acrylic polymer having carbon-carbon double bonds, the functional group can be on either side of the acrylic polymer and the above-mentioned compound, but in the preferred combination described above, the acrylic polymer has a hydroxyl group and the above-mentioned compound has an isocyanate group. In this case, examples of isocyanate compounds having carbon-carbon double bonds include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, etc. In addition, as acrylic polymers, copolymers of the monomers containing hydroxyl groups exemplified above or ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether are used.

[0089] The intrinsically radiocurable adhesive can use the aforementioned base polymer (especially acrylic polymers) with carbon-carbon double bonds alone, but it can also be combined with the aforementioned photopolymerizable compounds such as radiocurable monomer components and oligomer components to a degree that does not degrade the properties. The amount of the photopolymerizable compound is usually in the range of 30 parts by weight or less relative to 100 parts by weight of the base polymer, preferably in the range of 0 to 10 parts by weight.

[0090] In radiation-curing adhesives, when cured by ultraviolet light or the like, it is preferable to contain a photopolymerization initiator.

[0091] Among the aforementioned acrylic polymers, especially (meth)acrylate copolymers with radiation-curable groups introduced into the side chains, more specifically, (meth)acrylate copolymers comprising an acrylate represented by CH2=CHCOOR (where R is an alkyl group having 4 to 18 carbon atoms), a monomer containing hydroxyl groups, and an isocyanate compound having a free radical reactive carbon-carbon double bond within the molecule are preferred.

[0092] The amount of carbon-carbon double bonds is preferably 1.2 to 1.8 meq / g. Regarding the amount of double bonds, the amount of carbon-carbon double bonds contained in approximately 10g of the heated and dried binder can be quantitatively determined by the gravimetric method of bromine addition reaction in a vacuum in the dark.

[0093] The above-mentioned (meth)acrylate copolymer may, as needed, contain units corresponding to other monomer components.

[0094] Examples of isocyanate compounds containing double bonds include methacryloyl isocyanate, acryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate. Two or more isocyanate compounds containing double bonds can be used alone or in combination.

[0095] In addition, external crosslinking agents can be appropriately used in radiation-curing adhesives to adjust the adhesive strength before or after radiation irradiation. Specific methods for external crosslinking include adding polyisocyanate compounds, epoxy compounds, aziridine compounds, melamine-based crosslinking agents, etc., to induce a reaction. When using an external crosslinking agent, its amount is appropriately determined by balancing it with the base polymer to be crosslinked, and further by its intended use as an adhesive. Generally, the amount of external crosslinking agent used is 20 parts by weight or less (preferably 0.1 to 10 parts by weight) relative to 100 parts by weight of the base polymer. Furthermore, in addition to the above-mentioned components, various conventionally known adhesive additives, anti-aging agents, foaming agents, etc., can be added to radiation-curing adhesives as needed.

[0096] Furthermore, after grinding and polishing the back side of the wafer, before peeling off the support member, a wafer processing adhesive tape is first applied to the ground surface of the wafer. However, when applying the tape to the wafer surface immediately after back-side grinding but before oxide film formation, peeling off the subsequent wafer processing adhesive tape becomes difficult. Therefore, even when applying the tape to the wafer surface immediately after back-side grinding but before oxide film formation, it is preferable to add polypropylene oxide to the adhesive of the second adhesive layer in order to facilitate peeling.

[0097] There are no particular limitations on the polypropylene oxide used, and it can be appropriately selected from conventional polypropylene oxides. The number-average molecular weight of the polypropylene oxide is preferably greater than 3000 and less than 10000, more preferably 4000 to 10000. If the number-average molecular weight of the polypropylene oxide is too high, the affinity between the polypropylene oxide and the aforementioned acrylic polymer (X) deteriorates, resulting in contamination of the adhered material. If the number-average molecular weight of the polypropylene oxide is too low, the water resistance of the adhesive layer becomes insufficient, and the adhesive layer swells due to cutting water, resulting in meandering cut lines.

[0098] From the viewpoint of reducing wafer contamination, polyoxypropylene-glycerol ethers with a number average molecular weight greater than 3000 and less than 10000 are preferred, and more preferably 4000 to 10000. By using polyoxypropylene-glycerol ethers with a number average molecular weight in this range, the number of hydroxyl groups within the polyoxypropylene molecule increases from 2 to 3. Therefore, through reaction with crosslinking agents such as polyisocyanates, the possibility of incorporating polyoxypropylene into the crosslinking structure is increased, and the movement of polyoxypropylene to the wafer interface can reduce wafer surface contamination.

[0099] Examples of polypropylene oxides with a number average molecular weight greater than 3000 but less than 10000 include UNIOL D-4000 (number average molecular weight 4000) (trade name, manufactured by Nippon Oil Co., Ltd.), PREMINOL S4007 (number average molecular weight 5000) (trade name, manufactured by Asahi Glass Co., Ltd.), and PREMINOL S4011 (number average molecular weight 10000) (trade name, manufactured by Asahi Glass Co., Ltd.). Examples of polyoxypropylene-glycerol ethers with a number average molecular weight greater than 3000 but less than 10000 include UNIOLTG-4000 (number average molecular weight 4000) (trade name, manufactured by Nippon Yu Co., Ltd.), PREMINOL S3006 (number average molecular weight 5000) (trade name, manufactured by Asahi Glass Co., Ltd.), and PREMINOL S3011 (number average molecular weight 10000) (trade name, manufactured by Asahi Glass Co., Ltd.), but are not limited to these.

[0100] The amount of polypropylene oxide (PPO) with a number average molecular weight greater than 3000 and less than 10000 can be appropriately selected from 0.1 to 3.0 parts by weight, preferably 0.5 to 2.0 parts by weight, relative to 100 parts by weight of the substrate polymer. If the amount of PPO is too small, the wafer grinding surface is unstable due to the incomplete formation of the natural oxide film, making it difficult to efficiently pick up thin semiconductor chips from large-diameter wafers when using wafer processing adhesive tape. If the amount of PPO is too large, the adhesion before radiation curing becomes insufficient, causing chip ends to peel off during dicing and leaving cutting dust on the back of the chip.

[0101] It should be noted that, in this invention, the situation of "sequentially stacking a substrate film, a first adhesive layer, and a second adhesive layer" also includes situations where other layers are further stacked between the first adhesive layer and the second adhesive layer. In this case, the adhesive layer in contact with the substrate film is composed of the aforementioned first adhesive layer, and the adhesive layer bonded to the semiconductor wafer is composed of the aforementioned second adhesive layer.

[0102] The thickness of the second adhesive layer is preferably 5 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less. When the adhesive layer is thinner than 5 μm, there is a concern that it may not exhibit sufficient adhesive strength. On the other hand, when the adhesive layer is thicker than 30 μm, there is a concern that adhesive residue may adhere to the semiconductor wafer.

[0103] The method of forming the second adhesive layer on the first adhesive layer or other layers is not particularly limited. By applying the adhesive composition of the second adhesive layer described above to a release liner (e.g., a plastic film or sheet coated with a release agent, etc.), forming the second adhesive layer, and then laminating the first adhesive layer or other layers disposed on the substrate film, an adhesive tape for wafer processing can be obtained.

[0104] The storage modulus G' of the first adhesive layer is preferably higher than that of the second adhesive layer. The storage modulus G' is determined by repeatedly preparing multiple adhesive layers formed on a known release film, performing two-layer stacking, peeling off the release film from one side, and further performing one-layer stacking to prepare a test piece with a thickness of 1–2 mm. The test piece is then measured using a dynamic viscoelasticity tester at 23°C and a frequency of 1 Hz. It should be noted that the storage modulus is measured on the adhesive layer before radiation irradiation.

[0105] The storage modulus G' of the first adhesive layer is preferably 5×10⁴ Pa to 100×10⁴ Pa, more preferably 5×10⁴ to 80×10⁴ Pa, and even more preferably 10×10⁴ to 70×10⁴ Pa. If the storage modulus G' of the first adhesive layer is 30×10⁴ Pa or higher, the solvent resistance is sufficient. When peeling the support member from the wafer, and dissolving and cleaning the adhesive with a solvent, stress on the adhesive layer due to wrinkles in the substrate film can be prevented, thus reducing the adhesive strength of the adhesive layer and ensuring adequate wafer retention. Furthermore, since the first adhesive layer retains the second adhesive layer even if the second adhesive layer dissolves in the solvent, the second adhesive layer can be prevented from detaching and contaminating the wafer, thus preventing a decrease in yield.

[0106] The storage modulus G' of the second adhesive layer is preferably 5×10⁴ Pa to 40×10⁴ Pa, more preferably 5×10⁴ to 20×10⁴ Pa, and even more preferably 5×10⁴ to 10×10⁴ Pa. When the storage modulus G' of the second adhesive layer is higher than 10×10⁴ Pa, there is a concern that the ability to follow the steps becomes insufficient, and the wafer cannot be adequately held in place, especially when dealing with wafers with surface steps.

[0107] The adhesive tape for wafer processing is preferably applied to the surface of the second adhesive layer. After adding 1 ml of menthol and allowing it to stand for 30 minutes, the residual solvent content is less than 1% (m / m). If the residual solvent content is less than 1% (m / m), when dissolving the adhesive on the wafer by using the solvent, or peeling off the support member, and cleaning the residual adhesive on the wafer, wrinkles can be prevented from forming on the substrate film of the adhesive tape for wafer processing. Therefore, stress is applied to the adhesive layer, reducing the adhesive strength of the adhesive layer and effectively holding the wafer. Furthermore, since the first adhesive layer retains the second adhesive layer even if the second adhesive layer dissolves in the solvent, it prevents the second adhesive layer from detaching and contaminating the wafer, thus preventing a decrease in yield.

[0108] <Determination of Residual Solvent Content>

[0109] After the adhesive tape for wafer processing is fabricated (after tape formation), it is cut into 40 mm square pieces. The release liner is peeled off, 1 mL of p-menthane is added, and the mixture is allowed to stand for 30 minutes. Then, the solvent is discarded, and the mixture is dried at room temperature for 30 minutes. 1.0 g of the cut adhesive layer sample is then immersed in 10 mL of acetone. The supernatant is analyzed by gas chromatography-mass spectrometry (GC-MS) under the following conditions.

[0110] [Analysis Conditions]

[0111] Injection volume: 1μL

[0112] Column: db-1 0.25mm × 30m

[0113] Inj: 200℃ (after holding at 40℃ for 4 minutes, increase the temperature to 200℃ at a rate of 20℃ / min)

[0114] He flow rate: 1.0 mL / min

[0115] In order to keep the residual solvent content below 1% and m / m, the glass transition temperature of the base polymer of the second adhesive layer can be set to above -20°C.

[0116] It should be noted that, as needed until the wafer processing adhesive tape is put into practical use, a synthetic resin film, typically used as a separator, may be attached to the adhesive layer side to protect the adhesive layer. Examples of materials constituting the synthetic resin film include polyethylene, polypropylene, polyethylene terephthalate, and paper. To improve peelability from the adhesive layer, the surface of the synthetic resin film may be subjected to peeling treatments such as silicone treatment, long-chain alkyl treatment, or fluorine treatment, as needed. The thickness of the synthetic resin film is typically 10–100 μm, preferably around 25–50 μm.

[0117] (The dissolution of solvent-based adhesives and the cleaning process of wafers)

[0118] When peeling the wafer from the support member, wafer processing adhesive tape and a ring frame are attached to the side of the support member that is not attached to the wafer. Then, the wafer and support member supported by the wafer processing adhesive tape and ring frame are immersed in an organic solvent to dissolve the adhesive that holds the support member to the wafer, peeling off the support member and cleaning the surface of the wafer where the adhesive adheres. In addition to the methods described above, methods for peeling the wafer from the support member include heating to soften the adhesive, causing the support member to slide and peeling off, or using laser irradiation to decompose the adhesive and peel off the support member. Even when using these methods, adhesive or its decomposition products may remain on the wafer surface after peeling off the support member. Therefore, to remove these residues, the wafer supported by the wafer processing adhesive tape and ring frame is immersed in an organic solvent to clean the wafer, or the wafer is cleaned by blowing organic solvent onto it while rotating.

[0119] The adhesive tape for electronic components according to the present invention includes the following methods.

[0120] [1] An adhesive tape for wafer processing, comprising at least a substrate film, a first adhesive layer, and a second adhesive layer sequentially laminated, characterized in that,

[0121] The first adhesive layer is formed from an adhesive composition comprising an acrylic polymer or a polyester polymer as the base polymer.

[0122] The glass transition temperature of the base polymer is above -20℃.

[0123] [2] As described in [1], the wafer processing adhesive tape, wherein the substrate film is formed of polyolefin resin.

[0124] [3] The wafer processing adhesive tape as described in [1] or [2], wherein the thickness of the substrate film is 70 to 350 μm.

[0125] [4] The wafer processing adhesive tape described in any of [1] to [3], wherein the residual solvent content after adding 1 ml of menthol to the surface of the second adhesive layer and letting it stand for 30 minutes is less than 1%, m / m.

[0126] [5] The wafer processing adhesive tape described in any of [1] to [4], wherein the energy storage modulus of the first adhesive layer is higher than that of the second adhesive layer.

[0127] [6] The wafer processing adhesive tape described in any of [1] to [5] is used in a wafer processing method that includes a solvent-based wafer cleaning process.

[0128] Next, the present invention will be further described in detail based on embodiments. The present invention will be described below through embodiments, but the present invention is not limited to these embodiments.

[0129] (1) Fabrication of substrate film

[0130] <Substrate Film 1>

[0131] The substrate film 1 was made by using an ethylene-vinyl acetate copolymer (trade name "NUC-3660" manufactured by NUC Corporation), melting it at 140°C, and forming it with a thickness of 80 μm using an extruder.

[0132] <Substrate Film 2>

[0133] Ethylene-methacrylate-(2-methyl-propyl acrylate)-Zn++ ionomer resin (manufactured by Mitsui & DuPont Polychemicals Co., Ltd., trade name "HIMILAN AM7316") was melted at 140°C and extruded to form a substrate film 2 with a thickness of 350 μm.

[0134] <Substrate Film 3>

[0135] Polypropylene (manufactured by Prime Polymer Co., Ltd., trade name "F227D") was melted at 140°C and shaped using an extruder to a thickness of 70 μm to produce a substrate film 3.

[0136] (2) Preparation of adhesive

[0137] <Adhesive 1>

[0138] An acrylic copolymer composed of ethyl acrylate (81 wt%), methacrylic acid (1 wt%), and 2-hydroxyethyl acrylate (18 wt%) was prepared. Then, 2-methacryloyloxyethyl isocyanate was added, causing the terminal OH group of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer to react with the NCO group of the 2-methacryloyloxyethyl isocyanate, resulting in an acrylic polymer as a base polymer having residues of a (meth)acrylic monomer portion bonded to the repeating unit of the main chain with a group containing a radioactive carbon-carbon double bond. The glass transition temperature of this acrylic polymer, measured by differential scanning calorimetry (DSC), was -20°C. For every 100 parts by weight of the acrylic polymer, 2 parts by weight of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "CORONATE L") and 1.5 parts by weight of a photopolymerization initiator (manufactured by BASF Corporation, trade name "Irgacure 184") were added and mixed to obtain an acrylic adhesive 1.

[0139] <Adhesive 2>

[0140] As the base polymer, an adhesive comprising a polyester polymer was prepared, namely Nichigo-POLYESTER (registered trademark) S-0097S55EO manufactured by Mitsubishi Chemical Corporation. It should be noted that the glass transition temperature of the polyester polymer in the base polymer is 1°C. 3 parts by weight of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "CORONATE L") were added to 100 parts by weight of the polyester polymer and mixed to obtain polyester adhesive 2.

[0141] <Adhesive 3>

[0142] An acrylic copolymer composed 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, causing the terminal OH group of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer to react with the NCO group of the 2-methacryloyloxyethyl isocyanate, yielding an acrylic polymer as a base polymer in which residues of a (meth)acrylic monomer portion, containing a group with a radioactive carbon-carbon double bond, are bonded to the repeating unit of the main chain. The glass transition temperature of this acrylic polymer, measured by differential scanning calorimetry (DSC), was -50 °C. To obtain a polyester-based adhesive 3, 2 parts by weight of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "CORONATE L") and 1.5 parts by weight of a photopolymerization initiator (manufactured by BASF Corporation, trade name "Irgacure 184") were added to 100 parts by weight of an acrylic polymer and mixed.

[0143] <Adhesive 4>

[0144] An acrylic copolymer composed of 2-ethylhexyl acrylate (78 wt%), methacrylic acid (1 wt%), and 2-hydroxyethyl acrylate (21 wt%) was prepared. Then, 2-methacryloyloxyethyl isocyanate was added, causing the terminal OH group of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer to react with the NCO group of 2-methacryloyloxyethyl isocyanate, resulting in an acrylic polymer as a base polymer having residues of a (meth)acrylic monomer portion bonded to the repeating unit of the main chain with a group containing a radioactive carbon-carbon double bond. The glass transition temperature of this acrylic polymer, measured by differential scanning calorimetry (DSC), was -64°C. 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 Corporation, trade name "Irgacure 184") were added to 100 parts by mass of the acrylic polymer and mixed to obtain a polyester-based adhesive 4.

[0145] <Adhesive 5>

[0146] An acrylic copolymer composed of butyl acrylate (70 wt%), methacrylic acid (1 wt%), and 2-hydroxyethyl acrylate (29 wt%) was prepared. Then, 2-methacryloyloxyethyl isocyanate was added, causing the terminal OH group of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer to react with the NCO group of 2-methacryloyloxyethyl isocyanate, resulting in an acrylic polymer as a base polymer having residues of a (meth)acrylic monomer portion bonded to the repeating unit of the main chain with a group containing a radioactive carbon-carbon double bond. The glass transition temperature of this acrylic polymer, measured by differential scanning calorimetry (DSC), was -45°C. For every 100 parts by weight of the acrylic polymer, 2 parts by weight of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "CORONATE L") and 1.5 parts by weight of a photopolymerization initiator (manufactured by BASF Corporation, trade name "Irgacure 184") were added and mixed to obtain a polyester-based adhesive 5.

[0147] <Adhesive 6>

[0148] An acrylic copolymer composed of methacrylate (62 wt%), acrylic acid (6 wt%), 2-hydroxyethyl acrylate (4 wt%), and 2-ethylhexyl acrylate (28 wt%) was prepared to obtain an acrylic polymer as the base polymer. The glass transition temperature of this acrylic polymer, measured by differential scanning calorimetry (DSC), was -10°C. Two parts by mass of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "CORONATEL") were mixed with 100 parts by mass of the acrylic polymer to obtain a polyester-based adhesive 6.

[0149] <Adhesive 7>

[0150] An acrylic copolymer composed 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, causing the terminal OH group of the 2-hydroxyethyl acrylate side chain of this acrylic copolymer to react with the NCO group of the 2-methacryloyloxyethyl isocyanate, yielding an acrylic polymer as a base polymer in which residues of a (meth)acrylic monomer portion, containing a radioactive carbon-carbon double bond, are bonded to the repeating unit of the main chain. The glass transition temperature of this acrylic polymer, measured by differential scanning calorimetry (DSC), was -30 °C. To obtain a polyester-based adhesive 7, 4 parts by weight of a polyisocyanate compound (manufactured by Tosoh Corporation, trade name "CORONATE L") and 1.5 parts by weight of a photopolymerization initiator (manufactured by BASF Corporation, trade name "Irgacure 184") were added to 100 parts by weight of an acrylic polymer and mixed.

[0151] (3) Fabrication of adhesive tape for wafer fabrication

[0152] <Example 1>

[0153] Adhesive 1 was dissolved in ethyl acetate, and the stirred adhesive composition was applied to a release liner made of a release-molded polyethylene terephthalate film to a thickness of 10 μm after drying. After drying at 110°C for 3 minutes, it was bonded to a substrate film 1 to form a first adhesive layer on the substrate film. Meanwhile, adhesive 4 was dissolved in ethyl acetate, and the stirred adhesive composition was applied to a release liner made of a release-molded polyethylene terephthalate film to a thickness of 10 μm after drying. After drying at 110°C for 3 minutes, a second adhesive layer was obtained. Then, the release liner was peeled off from the first adhesive layer, and the second adhesive layer was laminated onto the first adhesive layer to produce the wafer processing adhesive tape of Example 1.

[0154] <Examples 2-9, Comparative Examples 1-5>

[0155] Except for the substrate film and adhesive layer being the combinations described in Tables 1 and 2, the wafer processing adhesive tapes of Examples 2 to 9 and Comparative Examples 1 to 5 were prepared by the same method as in Example 1.

[0156] <Determination of Residual Solvent Content>

[0157] After the adhesive tape for wafer processing is fabricated (after tape formation), it is cut into 40 mm square pieces. The release liner is peeled off, 1 mL of p-menthane is added, and the mixture is allowed to stand for 30 minutes. The solvent is then discarded, and the mixture is dried at room temperature for 30 minutes. 1.0 g of the cut adhesive layer sample is then immersed in 10 mL of acetone. The supernatant is analyzed by gas chromatography-mass spectrometry (GC-MS) under the following conditions. The results are shown in Tables 1 and 2.

[0158] [Analysis Conditions]

[0159] Injection volume: 1μL

[0160] Column: db-1 0.25mm × 30m

[0161] Inj: 200℃ (after holding at 40℃ for 4 minutes, increase the temperature to 200℃ at a rate of 20℃ / min)

[0162] He flow rate: 1.0 mL / min

[0163] <Determination of Storage Modulus>

[0164] The storage modulus of the first and second adhesive layers of the Examples and Comparative Examples was determined as follows: Adhesive was applied to the release film to a dried thickness of 20 μm, and dried at 110°C for 3 minutes to form an adhesive layer, yielding a product. One hundred sheets of this product were prepared. The release film was peeled off, and the layers were laminated to a thickness of 2.0 mm. Test pieces were then produced by punching with an 8 mm diameter. These test pieces were fed into a dynamic viscoelasticity measuring machine (manufactured by Rheometrics) to measure the storage modulus G' at 23°C and a frequency of 1 Hz. The results are shown in Tables 1 and 2.

[0165] <Evaluation of solvent resistance>

[0166] On an 8-inch wafer, the wafer processing adhesive tape of the embodiment and comparative example was attached and fixed to a ring frame. While blowing menthol as an organic solvent from the wafer side, the wafer was rotated at 2000 rpm to perform rotational cleaning. After cleaning and drying, the adhesive layer in the areas of the wafer where the wafer processing dicing tape was not attached was observed. Products where the first adhesive layer remained intact and no detachment was observed was considered good and rated as ○. Products where the second adhesive layer dissolved or swollen, detached from the first adhesive layer, or wrinkled the substrate film were considered defective and rated as ×. The results are shown in Tables 1 and 2.

[0167] [Table 1]

[0168]

[0169] [Table 2]

[0170]

[0171] As shown in Table 1, the wafer processing adhesive tape of the embodiment has a first adhesive layer and a second adhesive layer sequentially stacked on the substrate film. The first adhesive layer is formed by an adhesive composition containing an acrylic polymer or a polyester polymer as the base polymer. The glass transition temperature of the base polymer is above -20°C, so it achieves excellent results in the evaluation of solvent resistance.

[0172] On the other hand, as shown in Table 2, the glass transition temperature of the base polymer of the first adhesive layer of the wafer processing adhesive tape in the comparative example is lower than -20°C, thus resulting in a poor result in the evaluation of solvent resistance.

Claims

1. An adhesive tape for wafer processing, characterized in that, It is an adhesive tape for wafer processing formed by at least sequentially stacking a substrate film, a first adhesive layer, and a second adhesive layer. The first adhesive layer is formed of an adhesive composition comprising an acrylic polymer or a polyester polymer as the base polymer. The glass transition temperature of the substrate polymer is above -20°C.

2. The adhesive tape for wafer processing according to claim 1, wherein, The substrate film is formed of polyolefin resin.

3. The adhesive tape for wafer processing according to claim 1 or 2, wherein, The thickness of the substrate film is 70μm to 350μm.

4. The adhesive tape for wafer processing according to claim 1 or 2, wherein, The residual solvent content after adding 1 ml of menthol to the surface of the second adhesive layer and letting it stand for 30 minutes is less than 1% m / m.

5. The adhesive tape for wafer processing according to claim 1 or 2, wherein, The energy storage modulus of the first adhesive layer is higher than that of the second adhesive layer.

6. The adhesive tape for wafer processing according to claim 1 or 2, characterized in that, A wafer processing method used in wafer cleaning processes that include solvent-based wafer cleaning.

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