Adhesive tape for wafer processing

Abstract

To provide an adhesive tape for wafer processing that can be easily picked up without leaving adhesive residue during a pick-up process even without using a release agent.SOLUTION: An adhesive tape for wafer processing consisting of a base film and at least one radiation-curable adhesive layer formed on the base film has a tensile modulus of elasticity of 90 to 400 MPa, and after a release film is attached to the adhesive layer and subjected to ultraviolet irradiation treatment with an accumulated light dose of 200 mJ / cm2, the release film is peeled off, and a probe is contacted with the surface of the adhesive layer, and the force required to peel it upward is measured. In this test, the peak value is 3.2 kPa or less, the adhesive layer contains a base polymer having a carbon-carbon double bond, and the carbon-carbon double bond content of the base polymer is 1.0 meq / g or less, and the base film contains 45 to 85 wt% polypropylene.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive tape for wafer processing, and more particularly to a radiation-curable adhesive tape for wafer processing that changes adhesive strength when irradiated with radiation and is used to pick up chips obtained by dividing a wafer. [Background technology]

[0002] Conventionally, semiconductor wafers and semiconductor-related materials such as semiconductor packages are cut using cutting blades such as rotary blades to separate them into small semiconductor elements and IC components. For example, semiconductor wafers made of materials such as silicon, germanium, and gallium arsenide are manufactured in large diameters, then back-ground to a predetermined thickness, and then further processed as needed (etching, polishing, etc.). Next, the semiconductor wafers are cut (diced) and picked up before being mounted and molded. During this dicing process, adhesive tape for wafer processing is used to hold the semiconductor wafer in place and cut it into chips.

[0003] Adhesive tapes for wafer processing are required to have strong retention properties to prevent chips from flying off due to the impact of the dicing blade cutting the wafer during the cutting process, resulting in a decrease in yield and damage to the dicing blade. Furthermore, when picking up chips, the chips are lifted from the backside of the adhesive tape using a push-up pin, so they are required to be easily releasable to prevent chip breakage and a decrease in yield due to poor release. Thus, adhesive tapes for wafer processing are required to have conflicting performance characteristics in the dicing and pick-up processes. To achieve these requirements, it is known to use radiation-curable adhesive tapes for wafer processing, whose adhesive strength changes when exposed to radiation (see, for example, Patent Document 1).

[0004] Adhesive tapes for wafer processing generally consist of a base film and at least one adhesive layer formed on the base film. To improve pickup properties, the adhesive layer contains a crosslinking agent, which crosslinks the base polymer to form a three-dimensional network structure, improving the cohesive strength of the adhesive and preventing adhesive residue from being left on the chip when it is picked up after irradiation (see, for example, Patent Document 2, paragraphs

[0054] to

[0057] ).

[0005] In recent years, in response to demands for further miniaturization, thinning, and weight reduction of devices, similar demands have been placed on electronic components, such as semiconductor devices, used inside these devices. To achieve the miniaturization of electronic components, for example, three-dimensional packaging technology has been proposed, which achieves high-density packaging by stacking semiconductor chips. Furthermore, as a method for implementing three-dimensional packaging technology, for example, a semiconductor package structure has been proposed in which electrodes (through electrodes) that penetrate from the front surface to the back surface of a chip are formed, and the chip is stacked on a packaging chip called an interposer via the electrodes.

[0006] The use of adhesive tape for wafer dicing processing having a radiation-curable adhesive layer is being considered for the process of cutting and separating a wafer with through electrodes into small element pieces (semiconductor chips) (dicing process) and picking up these semiconductor chips (pickup process).

[0007] In the radiation-curable adhesive tapes for dicing disclosed in Patent Documents 1 and 2, after dicing, the adhesive layer is irradiated with radiation to harden it, thereby reducing its adhesive strength, and the adhesive layer shrinks upon hardening.

[0008] However, in recent years, chip shapes have become more complex, and when the adhesive reacts with the chip to conform to the unevenness of the adhesive, the adhesive reacts with high crosslink density and hardens, causing the adhesive to become trapped in the unevenness due to cure shrinkage, making it difficult to pick up the chip. Therefore, in addition to increasing crosslink density, methods for improving pick-up include reducing the surface free energy of the adhesive surface. For example, it is known to add a release agent to the adhesive layer to reduce the peel strength of the adhesive layer against the adherend, allowing for smooth release from the adhesive layer (see, for example, Patent Document 3, paragraphs

[0056] to

[0058] ). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-19607 [Patent Document 2] Japanese Patent Application Laid-Open No. 2024-7771 [Patent Document 3] Japanese Patent Publication No. 2023-13021 Summary of the Invention [Problem to be solved by the invention]

[0010] However, if a release agent is added to the adhesive layer, the release agent may adhere to the chip, which can cause bonding problems such as chip misalignment during packaging. Therefore, to prevent the release agent from adhering to the chip, there is a demand for an adhesive tape for wafer processing that is release-agent-free but can still pick up chips well.

[0011] Therefore, an object of the present invention is to provide an adhesive tape for wafer processing that can be easily picked up even when a release agent-free adhesive is used while suppressing cure shrinkage of the adhesive. [Means for solving the problem]

[0012] The inventors of the present application discovered that the physical properties of the base film affect the pickup properties, and further discovered that the above-mentioned problems can be solved by controlling the mechanical properties of the adhesive tape for wafer processing, which are predominantly influenced by the base film, and thus completed the present invention.

[0013] That is, the adhesive tape for wafer processing according to the present invention is an adhesive tape for wafer processing comprising a base film and at least one radiation-curable adhesive layer formed on the base film, and has a tensile modulus of 90 to 400 MPa when a test piece processed to a width of 25 mm is pulled at 25°C with a chuck distance of 50 mm and a pulling speed of 300 mm / min, and has an integrated light dose of 200 mJ / cm when a release film is attached to the adhesive layer. 2 After the ultraviolet irradiation treatment, the release film is peeled off, and a probe made of SUS304 and having a diameter of 5 mm is brought into contact with the surface of the pressure-sensitive adhesive layer at 25°C for 1 second at a speed of 30 mm / min and a contact load of 100 gf. The force required to peel the probe upward at a peeling speed of 600 mm / min is measured, and the peak value in a probe tack test is 3.2 kPa or less; the pressure-sensitive adhesive layer contains a base polymer having a carbon-carbon double bond, and the base polymer has a carbon-carbon double bond content of 1.0 meq / g or less; and the substrate film contains 45 to 85 wt% of polypropylene.

[0014] The above-mentioned adhesive tape for wafer processing is preferably used in a pick-up step for picking up diced chips.

[0015] In the pressure-sensitive adhesive tape for wafer processing, the base film preferably contains a hydrogenated styrene-based thermoplastic elastomer.

[0016] In addition, in the adhesive tape for wafer processing, the base film preferably contains 20% or more of a biomass component.

[0017] In addition, in the adhesive tape for wafer processing, the polypropylene preferably contains 40% or more of a biomass component. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide an adhesive tape for wafer processing that can be easily picked up in the pick-up step even for semiconductor chips and the like that require a release agent-free adhesive tape for wafer processing. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail.

[0020] The adhesive tape for wafer processing according to an embodiment of the present invention has at least one radiation-curable adhesive layer formed on at least one side of a base film.

[0021] The base film and the 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 in a form cut into individual wafers, or may be in a form in which a long separator formed by cutting a plurality of pieces each cut into one wafer is wound into a roll.

[0022] Hereinafter, each of the components of the adhesive tape for wafer processing of this embodiment will be described in detail.

[0023] (Base film) The base film preferably has uniform and isotropic extensibility so that the spacing between chips can be uniformly expanded in all directions during the pick-up process in which the adhesive tape for wafer processing is expanded and the chips are picked up with pins. The base film also preferably has appropriate rigidity so that the stress generated by the pins can be easily transmitted and the tackiness of the adhesive tape for wafer processing can be controlled.

[0024] The base film contains 45 to 85% by weight of polypropylene. The base film contains 45 to 85% by weight of polypropylene, which gives it appropriate rigidity, making it easier to transmit stress during pin thrusting and reducing the tackiness of the wafer processing adhesive tape after radiation exposure. This allows for good pick-up even without a release agent. If the polypropylene content is less than 45% by weight, the adhesive tape for wafer processing will remain attached to the chip when the pickup pin is pushed up, causing the base film in the kerf area to stretch, which may prevent the chip and the adhesive tape for wafer processing from peeling off, resulting in a deterioration in pickup performance.

[0025] Examples of polypropylene resins include propylene homopolymers, propylene-ethylene random copolymers, propylene-α-olefin random copolymers, propylene-ethylene-α-olefin copolymers, propylene block copolymers (composed of a propylene homopolymer component or a copolymer component mainly composed of propylene, and a copolymer obtained by copolymerizing propylene with at least one monomer selected from ethylene and α-olefins), etc. These polypropylene resins may be used alone or in combination of two or more.

[0026] The α-olefin used in the polypropylene resin is preferably 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, or 1-decene, and more preferably 1-butene, 1-hexene, or 1-octene.

[0027] Examples of the propylene-α-olefin random copolymer include a propylene-1-butene random copolymer, a propylene-1-hexene random copolymer, and a propylene-1-octene random copolymer.

[0028] Examples of the propylene-ethylene-α-olefin copolymer include a propylene-ethylene-1-butene copolymer, a propylene-ethylene-1-hexene copolymer, and a propylene-ethylene-1-octene copolymer.

[0029] Examples of propylene block copolymers include (propylene)-(propylene-ethylene) copolymer, (propylene)-(propylene-ethylene-1-butene) copolymer, (propylene)-(propylene-ethylene-1-hexene) copolymer, (propylene)-(propylene-1-butene) copolymer, (propylene)-(propylene-1-hexene) copolymer, (propylene-ethylene)-(propylene-ethylene) copolymer, (propylene-ethylene)-(propylene-ethylene-1-butene) copolymer, (propylene-ethylene)-(propylene-ethylene- (propylene-ethylene)-(propylene-1-butene) copolymer, (propylene-ethylene)-(propylene-1-hexene) copolymer, (propylene-1-butene)-(propylene-ethylene) copolymer, (propylene-1-butene)-(propylene-ethylene-1-butene) copolymer, (propylene-1-butene)-(propylene-ethylene-1-hexene) copolymer, (propylene-1-butene)-(propylene-1-butene) copolymer, (propylene-1-butene)-(propylene-ethylene-1-hexene) copolymer, (propylene-1-butene)-(propylene-1-butene) copolymer, (propylene-1-butene)-(propylene-1-hexene) copolymer, and the like.

[0030] Of these polypropylene resins, propylene homopolymer, propylene-ethylene random copolymer, propylene-1-butene random copolymer, propylene-ethylene-1-butene copolymer, and propylene block copolymer are preferred.

[0031] The base film preferably contains a thermoplastic elastomer as a resin other than polypropylene from the viewpoint of uniform and isotropic extensibility.

[0032] The thermoplastic elastomer is not particularly limited, but an olefin-based elastomer and a styrene-based elastomer are preferred. The thermoplastic elastomer may be an olefin-based elastomer alone, a styrene-based elastomer alone, or a mixture thereof.

[0033] Examples of olefin-based elastomers include copolymers of α-olefins having 2 to 20 carbon atoms, such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-octene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene, as well as copolymers of the above α-olefins or copolymers further copolymerized with monomers such as styrene, non-conjugated dienes, and vinyl acetate.

[0034] Specific examples include amorphous elastic copolymers containing olefins as a main component, such as ethylene-propylene copolymer elastomers, ethylene-1-butene copolymer elastomers, ethylene-propylene-1-butene copolymer elastomers, ethylene-1-hexene copolymer elastomers, ethylene-1-octene copolymer elastomers, ethylene-styrene copolymer elastomers, ethylene-norbornene copolymer elastomers, propylene-1-butene copolymer elastomers, ethylene-propylene-non-conjugated diene copolymer elastomers, ethylene-1-butene-non-conjugated diene copolymer elastomers, and ethylene-propylene-1-butene-non-conjugated diene copolymer elastomers, as well as derivatives and acid-modified derivatives thereof. Preferred are ethylene-propylene copolymer elastomers, ethylene-1-butene copolymer elastomers, and ethylene-propylene-1-butene copolymer elastomers.

[0035] The styrene elastomer is preferably a block copolymer represented by the following formula (I) or (II). X-(YX)n…(I) (XY)n…(II)

[0036] In general formulas (I) and (II), X represents an aromatic vinyl polymer block, and in formula (I), the degrees of polymerization at both ends of the molecular chain may be the same or different. Y represents at least one selected from the group consisting of a butadiene polymer block, an isoprene polymer block, a butadiene / isoprene copolymer block, a hydrogenated butadiene polymer block, a hydrogenated isoprene polymer block, a hydrogenated butadiene / isoprene copolymer block, a partially hydrogenated butadiene polymer block, a partially hydrogenated isoprene polymer block, and a partially hydrogenated butadiene / isoprene copolymer block. n represents an integer of 1 or greater.

[0037] Specific examples include styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, styrene-ethylene-ethylene-propylene-styrene copolymer, styrene-butadiene-butene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, styrene-hydrogenated butadiene diblock copolymer, styrene-hydrogenated isoprene diblock copolymer, styrene-butadiene diblock copolymer, and styrene-isoprene diblock copolymer.

[0038] Among these, the base film is preferably a mixture of polypropylene and a hydrogenated styrene-based thermoplastic elastomer.

[0039] The base film preferably contains 20% or more biomass components. This reduces greenhouse gas emissions when used adhesive tape for wafer processing is disposed of. Furthermore, a high content of biomass components can reduce the amount of fossil resource materials used, such as oil, which is also beneficial in terms of sustainable resource use.

[0040] Biomass components refer to components derived from renewable organic resources. Typically, they refer to components derived from biological resources (typically plants that perform photosynthesis) that can be sustainably reproduced in the presence of sunlight, water, and carbon dioxide. Therefore, they exclude components derived from fossil resources that are depleted through use after mining. Biomass components may be, for example, the renewable organic resources themselves, or materials obtained by chemically or biologically synthesizing the organic resources (typically biological constituents). For example, biomass components may be components obtained from ethanol produced from sugarcane or sugars produced from corn.

[0041] To ensure that the base film contains 20% or more biomass components, a biomass material containing a biomass component may be used. The biomass material is not particularly limited, but examples include polylactic acid; biomass polyethylenes such as biomass high-density polyethylene (biomass HDPE), biomass low-density polyethylene (biomass LDPE), and biomass linear low-density polyethylene (biomass LLDPE); biomass polyolefins such as biomass polypropylene (biomass PP); biomass polyesters such as biomass PET and biomass polytrimethylene terephthalate (biomass PTT); biomass poly(3-hydroxybutyrate-co-3-hydroxyhexanoate); biomass polyamides such as polyhexamethylene sebacamide and poly(xylylene sebacamide); biomass polyurethanes such as biomass polyester ether urethane and biomass polyether urethane; and cellulose-based resins. These materials can be used alone or in combination.

[0042] The biomass material may have a biomass component content of substantially 100% by weight (e.g., 99 to 100% by weight, typically 99.9 to 100% by weight), 80 to 100% by weight (e.g., 85 to 100% by weight, typically 90 to 100% by weight), or less than 80% by weight. The biomass component content of the substrate film can be calculated by multiplying the blending ratio of each biomass material by the biomass ratio of the biomass material. The biomass component content of a biomass material can be determined using accelerator mass spectrometry (AMS) or liquid scintillation counter (LSC). Typically, it can be measured in accordance with ASTM D6866:2008.

[0043] In particular, it is preferable that the base film uses biomass PP containing 40% or more of a biomass component as the polypropylene.

[0044] The thickness of the base film is preferably 60 to 200 μm, and more preferably 70 to 150 μm. If it exceeds 200 μm, it may be impossible to pick up the chip from the adhesive tape for wafer processing, and if it is thinner than 60 μm, the adhesive tape for wafer processing may tear during expansion.

[0045] The surface of the substrate film that comes into contact with the pressure-sensitive adhesive layer may be subjected to a corona treatment or a treatment such as a primer in order to improve adhesion.

[0046] (Adhesive layer) The adhesive layer is not particularly limited as long as it has the properties of not peeling off from the wafer during the dicing process, holding power to the extent that defects such as chip flying do not occur, transmitting stress due to expansion to the wafer, and being able to be peeled off from the wafer when picked up.

[0047] The main component polymer (adhesive polymer, also called base polymer) of the adhesive can be selected from various types of polymers such as (meth)acrylic resin, epoxy resin, natural rubber resin, and synthetic rubber resin, but among these, (meth)acrylic resin is preferred, as the adhesive strength of (meth)acrylic resin is easy to control.

[0048] The pressure-sensitive adhesive layer is a radiation-curable type that is cured by irradiation with radiation. The pressure-sensitive adhesive composition constituting the radiation-curable 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.

[0049] The resin used in the pressure-sensitive adhesive layer is not particularly limited, and known pressure-sensitive adhesive resins such as chlorinated polypropylene resin, acrylic resin, polyester resin, polyurethane resin, and epoxy resin can be used, but an acrylic pressure-sensitive adhesive having an acrylic polymer as the base polymer is preferred.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] In addition, various methods can be used to control the crosslink density of the pressure-sensitive adhesive layer and improve its pick-up properties, including crosslinking 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 crosslinking 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, 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. 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, if necessary, to prevent deterioration.

[0055] Examples of the radiation-curable adhesive include additive-type radiation-curable adhesives obtained by blending a radiation-curable monomer component or a radiation-curable oligomer component with the above-mentioned adhesive.

[0056] 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.

[0057] 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 adhesive layer, so as to reduce the adhesive strength of the 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 adhesive.

[0058]

[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 of such components, and are therefore preferred because they do not allow the oligomer components to migrate within the adhesive over time, allowing the formation of an adhesive layer with a stable layer structure.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] When the radiation-curable adhesive is cured by ultraviolet light or the like, it is preferable that the adhesive contains a photopolymerization initiator.

[0064] Among the above-mentioned acrylic polymers, a (meth)acrylic acid ester copolymer comprising an acrylic acid ester represented by CH2=CHCOOR (wherein R is an alkyl group having 4 to 18 carbon atoms), a hydroxyl group-containing monomer, and an isocyanate compound having a radical-reactive carbon-carbon double bond in the molecule is particularly preferred.

[0065] The carbon-carbon double bond content is preferably 0.5 meq / g or more and 1.0 meq / g or less, and more preferably 0.6 meq / g or more and 0.9 meq / g or less. If the carbon-carbon double bond content is less than 0.5 meq / g, there is a risk that when a chip-shaped electronic component is peeled from the adhesive tape for electronic components 1, a residue of the adhesive from the adhesive tape for electronic components 1 may adhere to the surface of the electronic component, resulting in so-called adhesive residue. If the carbon-carbon double bond content is more than 1.0 meq / g, the adhesive may bite into unevenness in the adherend due to cure shrinkage, making it difficult to pick up the component properly. The carbon-carbon double bond content can be quantitatively measured by a weight increase method using bromine addition reaction in a dark place under vacuum for approximately 10 g of heat-dried adhesive.

[0066] The (meth)acrylic acid ester copolymer may contain units corresponding to other monomer components, if necessary.

[0067] 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.

[0068] 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.

[0069] The method for forming the pressure-sensitive adhesive layer on the base film is not particularly limited. For example, the 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.

[0070] The thickness of the adhesive layer is preferably 5 to 100 μm, and more preferably 20 μm or less. If the adhesive is too thick, the pushing-up stress of the pin during pickup is absorbed, making it impossible to achieve good pickup properties. Furthermore, if the adhesive is too thick during blade dicing, the vibration of the chip increases, which is undesirable from the viewpoint of chip chipping.

[0071] The adhesive layer may have a structure in which multiple layers are laminated. When multiple layers are present, it is preferable to use the above-mentioned radiation-curable adhesive for the layer to which the electronic component is attached, but heat-foamable adhesives can also be used for the other layers. Radiation-curable adhesives are cured by ultraviolet light, electron beams, etc., and make them easy to peel, while heat-foamable adhesives are made easy to peel by the use of a foaming agent or an expanding agent. Furthermore, an intermediate layer such as a primer layer may be provided between the substrate film and the adhesive layer as needed.

[0072] The tensile modulus of the wafer processing adhesive tape is 90 to 400 MPa. The tensile modulus of the wafer processing adhesive tape can be measured as follows: A test piece cut to a width of 25 mm is prepared, and a tensile test is performed at 25°C with a chuck distance of 50 mm and a speed of 300 mm / min to measure the change in elongation (mm) of the test piece. A tangent is drawn to the initial rising portion of the obtained SS curve (stress-strain curve), and the slope of the tangent is divided by the cross-sectional area of ​​the test piece to determine the tensile modulus. The tensile modulus is the average value of the tensile modulus when the wafer processing adhesive tape is stretched in the MD direction and the tensile modulus when it is stretched in the TD direction. Here, "MD direction" refers to the machine direction of the film, and "TD direction" refers to the direction perpendicular to the MD direction and parallel to the main surface of the film.

[0073] If the tensile modulus of the wafer processing adhesive tape is less than 90 MPa, the base film in the kerf area may stretch while the wafer processing adhesive tape remains attached to the chip when the pickup pin is pushed up, which may prevent the chip from peeling from the wafer processing adhesive tape and result in poor pickup performance.If the tensile modulus of the wafer processing adhesive tape is more than 400 MPa, the tape may not be able to stretch sufficiently when expanded by the pickup device, causing the tape to peel off from the ring frame.

[0074] The pressure-sensitive adhesive tape for wafer processing has a peak value of 3.2 kPa or less in a probe tack test after irradiation. The peak value in a probe tack test of the pressure-sensitive adhesive tape for wafer processing can be measured as follows: With a release film attached to the adhesive layer of the pressure-sensitive adhesive tape for wafer processing, a metal halide lamp is used to measure the peak value with an integrated light intensity of 200 mJ / cm. 2 After the ultraviolet irradiation treatment, the release film is peeled off, and a 5 mm diameter SUS304 (stainless steel) probe is brought into contact with the surface of the adhesive layer at 25°C for 1 second at a speed of 30 mm / min and a contact load of 100 gf, and then the force required to peel the probe upward at a peeling speed of 600 mm / min is measured and the peak value is determined.

[0075] If the peak value of the adhesive tape for wafer processing in the probe tack test after irradiation exceeds 3.2 kPa, it becomes difficult to pick up the chip from the adhesive tape for wafer processing.

[0076] 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.

[0077] The adhesive tape for wafer processing can be suitably used for dicing wafers having steps on the surface such as through electrodes, etc. After the adhesive tape for wafer processing is attached to the wafer, it is subjected to dicing in a conventional manner, irradiated with radiation, and then transferred to a pick-up process.

[0078] The pick-up method is not particularly limited, and various conventionally known pick-up methods can be used, such as a method in which each cut piece is pushed up from the adhesive tape for wafer processing by a jig such as a push-up pin, and the pushed-up cut piece is then picked up by a pick-up device.

[0079] The pressure-sensitive adhesive tape for electronic components according to the present invention includes the following aspects.

[0080] [1] An adhesive tape for wafer processing, comprising a substrate film and at least one radiation-curable adhesive layer formed on the substrate film, which has a tensile modulus of 90 to 400 MPa when a test piece processed to a width of 25 mm is pulled at 25°C with a chuck distance of 50 mm and a speed of 300 mm / min, and has an integrated light dose of 200 mJ / cm when a release film is attached to the adhesive layer. 2 and after the ultraviolet irradiation treatment, the release film is peeled off, and a probe made of SUS304 and having a diameter of 5 mm is brought into contact with the surface of the pressure-sensitive adhesive layer at 25°C for 1 second at a speed of 30 mm / min and a contact load of 100 gf, and the force required to peel the probe upward at a peeling speed of 600 mm / min is measured. The peak value in the probe tack test is 3.2 kPa or less; the pressure-sensitive adhesive layer contains a base polymer having a carbon-carbon double bond, and the base polymer has a carbon-carbon double bond content of 1.0 meq / g or less; and the substrate film contains 45 to 85 wt% polypropylene.

[0081] [2] The adhesive tape for wafer processing according to [1], which is used in a pick-up process for picking up diced chips.

[0082] [3] The adhesive tape for wafer processing according to [1] or [2], wherein the base film contains a hydrogenated styrene-based thermoplastic elastomer.

[0083] [4] The adhesive tape for wafer processing according to any one of [1] to [3], wherein the base film contains 20% or more of biomass components.

[0084] [5] The adhesive tape for wafer processing according to any one of [1] to [4], wherein the polypropylene contains 40% or more of biomass components.

[0085] 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.

[0086] (1) The following polypropylene resins were prepared: Polypropylene A: C14HP456J (manufactured by LyondellBasell, biomass content 50%) Polypropylene B: C14HP640J (manufactured by LyondellBasell, biomass content 50%) Polypropylene C: Novatec PPFG3DC (manufactured by Mitsubishi Chemical Corporation, biomass content 0%)

[0087] (2) The following thermoplastic elastomers were prepared. Thermoplastic elastomer A: Hybrar 7311F (manufactured by Kuraray Co., Ltd.)

[0088] (3) Preparation of adhesive <Adhesive 1> An acrylic copolymer consisting of ethyl acrylate (78 wt%), methacrylic acid (1 wt%), and 2-hydroxyethyl acrylate (21 wt%) was prepared. 2-Methacryloyloxyethyl isocyanate was then added to the copolymer, and the terminal OH groups of the 2-hydroxyethyl acrylate side chain reacted with the NCO groups of the 2-methacryloyloxyethyl isocyanate to obtain an acrylic polymer with 0.90 meq / g of radiation-curable carbon-carbon double bond-containing groups per repeating unit of the main chain. Acrylic pressure-sensitive adhesive 1 was obtained by adding 1 part by weight of a polyisocyanate compound (manufactured by Tosoh Corporation, product name "Coronate L") and 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. <Adhesive 2> An acrylic copolymer consisting of ethyl acrylate (64 wt%), methacrylic acid (1 wt%), and 2-hydroxyethyl acrylate (35 wt%) was prepared. 2-Methacryloyloxyethyl isocyanate was then added to the copolymer, and the terminal OH groups of the 2-hydroxyethyl acrylate side chain reacted with the NCO groups of the 2-methacryloyloxyethyl isocyanate to obtain an acrylic polymer with 1.50 meq / g of radiation-curable carbon-carbon double bond-containing groups per repeating unit of the main chain. Acrylic pressure-sensitive adhesive 2 was obtained by adding 1 part by weight of a polyisocyanate compound (manufactured by Tosoh Corporation, product name "Coronate L") and 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.

[0089] (4) Preparation of adhesive tape for wafer processing Example 1 A base film was prepared by kneading 65% by weight of polypropylene A and 35% by weight of thermoplastic elastomer and molding it to a thickness of 100 μm. The base film had a biomass component content of 32.5%. The adhesive composition was prepared by dissolving adhesive 1 in ethyl acetate and stirring the mixture. The adhesive composition was then coated onto a release film made of a release-treated polyethylene terephthalate film so that the thickness after drying would be 15 μm. The film was then dried at 110°C for 3 minutes, and then bonded to the above-mentioned base film to produce an adhesive tape for wafer processing according to Example 1, in which an adhesive layer was formed on the base film.

[0090] <Examples 2 to 5 and Comparative Examples 1 to 8> Adhesive tapes for wafer processing according to Examples 2 to 5 and Comparative Examples 1 to 8 were produced in the same manner as in Example 1, except that the base film and adhesive were combined and mixed in the proportions shown in Table 1.

[0091] <Measurement of tack strength> The tack strength was measured using a tacking tester TAC-II manufactured by Rhesca Corporation. The measurement mode used was Constant Load, which pushes the probe in to a set pressure value and continues to control the pressure value to be maintained until a set time has elapsed. The wafer processing adhesive tape was placed on a plate, and the back side of the wafer processing adhesive tape was not fixed to the plate. A circular jig with an inner diameter of 8 mm was used as a holding jig to press the wafer processing adhesive tape against the plate, and the probe was pressed into the wafer processing adhesive tape exposed through the hole in the holding jig. With the release film attached to the wafer processing adhesive tape according to the examples and comparative examples, a metal halide lamp was used to measure the tack strength. 2 After the UV irradiation treatment, the release film was peeled off. The adhesive layer was placed facing up, and a 5 mm diameter SUS304 probe was contacted from above. The probe was brought into contact with the measurement sample at a speed of 30 mm / min, with a contact load of 100 gf and a contact time of 1 second. The probe was then peeled upward at a peeling speed of 600 mm / min, and the force required to peel was measured, with the peak value being the tack force. The probe temperature and plate temperature were 25°C. The results are shown in Tables 1 and 2.

[0092] <Measurement of tensile modulus> Test pieces of 25 mm x 150 mm were cut from the wafer processing adhesive tapes of the Examples and Comparative Examples to prepare test pieces, and the tensile modulus was measured at a temperature of 25°C and a relative humidity of 50% in accordance with JIS K7161:2014. Specifically, the test pieces were subjected to a tensile test at a speed of 300 mm / min using a tensile tester (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name "S50-F / S50") with a chuck distance of 50 mm, to measure the tensile modulus. Measurements were performed in both the MD and TD directions, and the average of these measurement results was recorded as the tensile modulus. The results are shown in Tables 1 and 2.

[0093] Using an OMN-12 inch laminating machine (manufactured by Omiya Kogyo Co., Ltd.), the adhesive tapes for electronic components according to the Examples and Comparative Examples were laminated to a glass wafer as a stepped chip. The glass wafer was laminated to a 10 μm-high masked optical filter (manufactured by Tanaka Giken Co., Ltd.). The glass wafer was laminated to the adhesive tape for electronic components so that the dividing lines of the glass wafer were aligned with the MD and TD directions of the base film.

[0094] Thereafter, dicing was carried out using a dicing machine (manufactured by DISCO Corporation, product name: DFD-6340) under the following conditions so that the chip size would be 4.1 mm x 4.1 mm square. (Dicing conditions) Blade: DISCO Corporation "KR15-SD400-BAA501-60" Blade rotation speed: 15,000 rpm Dicing speed: 5mm / sec Blade height: 80μm Cutting mode: Down cutting

[0095] <Ring frame peeling evaluation> The semiconductor processing tapes of the examples and comparative examples were checked for peeling from the ring frame when expanding to secure the semiconductor processing tape during dicing. Products that did not peel from the ring frame were evaluated as good products with a "○" and products that did peel were evaluated as defective with a "×". The results are shown in Tables 1 and 2.

[0096] <Evaluation of chipping> The backsides of the 64 chips obtained by the above dicing were checked for the presence or absence of chippings of 20 μm or more using an automatic visual inspection device (manufactured by Camtek, product name: Eagle-T). Products with 30 or fewer chips were evaluated as good products with a "◯" and those with more than 30 chips were evaluated as defective products with a "X". The results are shown in Tables 1 and 2.

[0097] <Evaluation of pick-up ability> UV rays were applied at 200mJ / mm from the base film side of the wafer processing adhesive tape. 2 After irradiating the adhesive layer to harden, the individual chips were picked up using a die picker (Canon Machinery, Inc., product name: CAP-300II). Twenty random chips were picked up, and the number of chips that were successfully picked up was counted. A good product was rated as "◎" if all 20 chips were successfully picked up with a pin height of 80 μm, a good product was rated as "◯" if all 20 chips were successfully picked up with a pin height of 100 μm, and an unsatisfactory product was rated as "×" otherwise. The results are shown in Tables 1 and 2. Note that pick-up performance was not evaluated for chips in which the ring frame peeled off after dicing.

[0098] [Table 1]

[0099] [Table 2]

[0100] As shown in Table 1, the adhesive tape for wafer processing according to the embodiment has a tensile modulus of 90 to 400 MPa, a peak value in the probe tack test of 3.2 kPa or less, a carbon-carbon double bond content in the base polymer of the adhesive layer of 1.0 meq / g or less, and a base film containing 45 to 85 wt% polypropylene, and therefore achieved excellent results in all evaluations of ring frame peeling, chipping, and pick-up properties.

[0101] On the other hand, as shown in Table 2, the wafer processing adhesive tapes according to the comparative examples in Comparative Examples 1 to 3 and 5 had a tensile modulus of elasticity exceeding 400 MPa, resulting in insufficient extensibility of the wafer processing adhesive tape, resulting in peeling of the ring frame and chipping. In Comparative Examples 4, 5 and 7, the tensile modulus was less than 90 MPa, resulting in insufficient rigidity of the wafer processing adhesive tape, causing the base film of the pushed-up tip portion to stretch and failing to pick up well. Furthermore, in Comparative Examples 4 and 5, the peak value in the probe tack test exceeded 3.2 kPa, which also resulted in poor pick-up ability. In Comparative Examples 7 and 8, the carbon-carbon double bond content in the adhesive layer was greater than 1.0, resulting in jamming into the mask portion and failing to pick up.

Claims

1. An adhesive tape for wafer processing comprising a base film and at least one radiation-curable adhesive layer formed on the base film, A test piece processed to a width of 25 mm is used, and when pulled at 25°C with a chuck distance of 50 mm and a pulling speed of 300 mm / min, the tensile modulus is 90 to 400 MPa. With a release film attached to the pressure-sensitive adhesive layer, the integrated light intensity is 200 mJ / cm 2 the release film is peeled off after the ultraviolet irradiation treatment of the present invention, and a probe made of SUS304 and having a diameter of 5 mm is brought into contact with the surface of the pressure-sensitive adhesive layer at 25°C for 1 second at a speed of 30 mm / min and a contact load of 100 gf, and then the force required to peel the probe upward at a peeling speed of 600 mm / min is measured. The peak value in a probe tack test is 3.2 kPa or less, the PSA layer contains a base polymer having a carbon-carbon double bond, and the base polymer has a carbon-carbon double bond content of 1.0 meq / g or less; The adhesive tape for wafer processing is characterized in that the base film contains 45 to 85% by weight of polypropylene.

2. 2. The adhesive tape for wafer processing according to claim 1, which is used in a pick-up process for picking up diced chips.

3. 3. The adhesive tape for wafer processing according to claim 1, wherein the base film contains a hydrogenated styrene-based thermoplastic elastomer.

4. 3. The adhesive tape for wafer processing according to claim 1, wherein the base film contains 20% or more of a biomass component.

5. 3. The adhesive tape for wafer processing according to claim 1, wherein the polypropylene contains 40% or more of a biomass component.

6. 4. The adhesive tape for wafer processing according to claim 3, wherein the polypropylene contains 40% or more of a biomass component.

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