Adhesive tape and method of processing

Abstract

An adhesive tape having a substrate layer, and an adhesive layer provided on the substrate layer, the aforementioned adhesive layer containing a photoradical initiator, and a polymer A having a polymerizable carbon double bond, the difference |R0-R1| between the contact angle R0 of a silicon wafer surface against water, and the contact angle R1 of the silicon wafer surface against water after the aforementioned adhesive layer is irradiated with ultraviolet rays after the aforementioned adhesive layer is attached to the aforementioned silicon wafer and left for 24 hours, and the aforementioned adhesive layer is peeled off, is 20° or less.

Description

Technical Field

[0001] This invention relates to adhesive tape and processing methods. Background Technology

[0002] When unibodying semiconductor packages and semiconductor wafers (hereinafter also referred to as "attached objects"), semiconductor wafer processing tape is attached to the attached object to temporarily fix it in place during dicing. This prevents the chip from scattering during unibodying. After dicing, the semiconductor wafer processing tape is expanded, and the unibody attached object is picked up (peeled) from the tape.

[0003] This type of semiconductor wafer processing tape is primarily used on adhesive tapes coated with an adhesive layer that cures upon exposure to ultraviolet light onto a film substrate that is transparent to ultraviolet light. In this ultraviolet-curable processing tape, the curing reaction is carried out by irradiating the adhesive layer with ultraviolet light after dicing, thereby reducing the adhesive strength of the adhesive layer and making it easier to pick up monolithically bonded substrates.

[0004] In such adhesive tapes for semiconductor wafer processing, there is a need for technologies that minimize adhesive residue on the adhered material during pickup and enable the manufacture of high-quality electronic components.

[0005] Regarding this point, in the case of the aforementioned UV-irradiated processing tape, when the adhesive tape is applied to the substrate, if air bubbles or the like enter between the adhesive tape and the substrate, the adhesive may not cure properly due to oxygen resistance during UV irradiation, leaving uncured adhesive residue on the substrate. Furthermore, if the adhesion to the substrate is insufficient, cutting water can seep between the substrate and the adhesive tape during dicing, contaminating the substrate and causing the individual pieces of the substrate to scatter.

[0006] Therefore, to compensate for adhesive force, methods such as increasing the thickness of the adhesive layer and decreasing the elastic modulus of the adhesive layer can be considered to improve adhesive force. However, in this case, sometimes the adhesive melts and is scraped off due to the frictional heat generated by the rotation of the blade during dicing. As a result, adhesive residue adheres to the adhered objects, and the monolithic adhered objects are fixed to the adhesive tape. This causes the adhesive to be unable to be peeled off at the interface with the adhered objects during pickup, resulting in the destruction of the adhesive itself and the problem of adhesive residue remaining on the adhered objects.

[0007] For example, Patent Document 1 discloses a method for suppressing residual adhesive by using a radiopolymerizable compound having 5 to 6 acryloyl groups to achieve a gel fraction of 90 wt% or more after ultraviolet irradiation and / or electron beam irradiation.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2000-281993 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] However, in the method described in Patent Document 1, although residual adhesive can be suppressed to some extent, there is a tendency to reduce the adhesive strength. When dicing, the cutting water seeps between the adhered material and the adhesive tape, which may cause backside contamination and the scattering of the single-piece adhered material.

[0013] Furthermore, due to the increasing demands for higher density and performance in semiconductor wafers and devices in recent years, even surfaces that appear to be free of adhesive residue can sometimes be contaminated by organic matter originating from adhesives. This contamination is gradually becoming a problem. It should be noted that in this specification, when referred to as "contamination," it refers to this type of contamination that is not visible to the naked eye; for those that are visible, it is referred to as "adhesive residue."

[0014] The present invention was made in view of the above-mentioned problems, and its object is to provide an adhesive tape capable of reducing contamination from the adhesive layer and a processing method using the adhesive tape.

[0015] Methods for solving problems

[0016] To address the aforementioned issues, the inventors of this application conducted in-depth research on the adhesive design of adhesive tapes. As a result, they discovered that the aforementioned issues could be resolved by using an adhesive layer constructed to exhibit specified contact angle characteristics before and after UV curing, thus completing this invention.

[0017] That is, the present invention is as follows.

[0018] [1]

[0019] An adhesive tape having a substrate layer and an adhesive layer disposed on the substrate layer.

[0020] The aforementioned adhesive layer comprises a photoradical initiator and a polymer A having polymerizable carbon double bonds.

[0021] The difference between the water contact angle R0 of the silicon wafer surface and the water contact angle R1 of the silicon wafer surface after the adhesive layer is attached to the silicon wafer and left for 24 hours, the adhesive layer is irradiated with ultraviolet light, and the adhesive layer is then peeled off, |R0-R1|, is less than 20°.

[0022] [2]

[0023] The adhesive tape of claim 1, wherein the content of component A1, which has a weight average molecular weight of 20,000 or less, contained in the aforementioned polymer A is 15% or less of the total area of ​​the gel permeation chromatography chromatogram.

[0024] [3]

[0025] The adhesive tape as described in [1] or [2], wherein the 180° peel strength of the aforementioned adhesive layer to the silicon wafer before ultraviolet irradiation is 2.0 to 20.0 N / 20 mm at 23°C.

[0026] [4]

[0027] The adhesive tape as described in any one of [1] to [3], wherein polymer A has hydroxyl groups.

[0028] [5]

[0029] The adhesive tape as described in any one of [1] to [4], wherein the weight-average molecular weight of the aforementioned polymer A is 1.0 × 10⁻⁶. 5 ~2.0×10 6 .

[0030] [6]

[0031] The adhesive tape as described in any one of [1] to [5], wherein the glass transition point of the aforementioned polymer A is -80 to 23°C.

[0032] [7]

[0033] The adhesive tape as described in any one of [1] to [6], wherein the aforementioned polymer A comprises a (meth)acrylate copolymer,

[0034] The (meth)acrylate copolymer has a linear, branched, or cross-linked shape.

[0035] [8]

[0036] The adhesive tape as described in any one of [1] to [7], wherein the aforementioned adhesive layer further comprises a curing agent.

[0037] [9]

[0038] The adhesive tape as described in [8], wherein the aforementioned curing agent comprises an isocyanate compound.

[0039]

[10]

[0040] The adhesive tape as described in [9], wherein the aforementioned isocyanate compound comprises a polyfunctional isocyanate compound with two or more functions.

[0041]

[11]

[0042] The adhesive tape as described in any one of [8] to

[10] , wherein the content of the aforementioned curing agent is 0.1 to 5.0 parts by weight relative to 100 parts by weight of polymer A.

[0043]

[12]

[0044] The adhesive tape as described in any one of [1] to

[11] is used for semiconductor wafers, semiconductor devices, and various semiconductor packaging processes.

[0045]

[13]

[0046] The processing method has the following characteristics:

[0047] A bonding process in which the adhesive tape described in any one of [1] to

[12] is bonded to the substrate; and

[0048] The process of cutting the aforementioned adhesive tape into individual pieces while the adhesive tape is bonded to the aforementioned object.

[0049] The aforementioned adhered objects are semiconductor wafers, semiconductor devices, or various semiconductor packages.

[0050] Invention Effects

[0051] According to the present invention, an adhesive tape capable of reducing contamination from the adhesive layer and a processing method using the adhesive tape can be provided. Detailed Implementation

[0052] Hereinafter, embodiments of the present invention (hereinafter referred to as "this embodiment") will be described in detail, but the present invention is not limited thereto, and various modifications can be made without departing from its spirit.

[0053] (Adhesive tape)

[0054] The adhesive tape of this embodiment has a substrate layer and an adhesive layer disposed on the substrate layer. The adhesive layer contains a photoradical initiator and a polymer A having polymerizable carbon double bonds. The difference between the contact angle R0 of the silicon wafer surface to water and the contact angle R1 of the silicon wafer surface to water after the adhesive layer is attached to the silicon wafer and left for 24 hours, the adhesive layer is irradiated with ultraviolet light, and the adhesive layer is peeled off, |R0-R1|, is less than 20°.

[0055] Conventional adhesive layers are typically composed of a base polymer that does not cure under UV light and a low molecular weight component that does cure under UV light. Therefore, after UV irradiation, the unreacted low molecular weight components and polymer components may contaminate the surface of the adhered objects.

[0056] In contrast, in this embodiment, polymer A, which has polymerizable carbon double bonds, is used, and ultraviolet light irradiation is used to further polymerize and crosslink polymer A with each other. Therefore, the problem of low molecular weight components contaminating the surface of the adhered objects can be avoided. Furthermore, even if a portion of the polymerizable carbon double bonds in polymer A remains unreacted, surface contamination can still be avoided compared to low molecular weight components. Moreover, when using low molecular weight components with polymerizable carbon double bonds, these components can also bond with polymer A, thus becoming easier to remain in the adhesive and suppressing contamination of the adhered object surface.

[0057] Furthermore, in this embodiment, the UV-based curing characteristics of the adhesive layer containing polymer A are defined using the contact angle characteristic represented by the difference between contact angles R0 and R1, |R0-R1|. By using an adhesive layer with such contact angle characteristics, contamination from the adhesive layer can be further reduced. The present invention will now be described in detail.

[0058] (Contact Angle)

[0059] In this embodiment, the low contamination level of the adhesive layer on the silicon wafer after ultraviolet irradiation is defined by using the difference between the contact angle R0 of the silicon wafer surface to water and the contact angle R1 of the silicon wafer surface to water after the adhesive layer is attached to the silicon wafer and left for 24 hours, the adhesive layer is irradiated with ultraviolet light, and the adhesive layer is peeled off, |R0-R1|.

[0060] More specifically, the difference |R0-R1| is 20° or less, preferably 0 to 17.5°, more preferably 0 to 15°, and even more preferably 0 to 12.5°. The smaller the difference |R0-R1|, the less contamination occurs from the adhered material.

[0061] In particular, by keeping |R0-R1| below 20°, contamination is significantly reduced, and the yield rate of subsequent manufacturing steps and final assembly of the adhered objects is improved. On the other hand, when the difference |R0-R1| is greater than 20°, the surface of the adhered objects is easily contaminated, and even residual adhesive may be generated on the adhered objects.

[0062] It should be noted that silicon wafers typically exhibit high hydrophilicity because their outermost surface is exposed to hydroxyl groups due to oxidation by oxygen in the air. Therefore, a small water contact angle R1 indicates a state close to that of a clean silicon wafer surface before the adhesive tape was applied. Conversely, if the silicon wafer is contaminated by organic components contained in the adhesive layer, the hydrophilicity of the silicon wafer surface decreases, and the water contact angle increases.

[0063] Furthermore, the contact angle R1 is preferably 5–25°, more preferably 5–28°, and even more preferably 5–32°. By keeping the contact angle R1 within the above range, contamination of the silicon wafer by the adhesive layer after ultraviolet irradiation can be further suppressed.

[0064] There are no particular limitations on methods for ensuring that the difference |R0-R1| and the contact angle R1 are within the aforementioned ranges. Examples include reducing the low molecular weight components in the adhesive, reducing the low molecular weight components of polymer A, and increasing the crosslinking density under ultraviolet irradiation. There are no particular limitations on methods for reducing low molecular weight components. Examples include forming an adhesive layer on a substrate layer and then aging it at a heated temperature, or using polymer A with a low content of low molecular weight components. Furthermore, there are no particular limitations on methods for increasing the crosslinking density. Examples include adjusting the number of polymeric carbon double bonds and the content of photoradical initiators.

[0065] The "contact angle" described in this specification is: after attaching the adhesive tape to the silicon wafer and placing it at 23°C for 24 hours, the contact angle is measured using a high-pressure mercury lamp at 150 mJ / cm². 2 The contact angle is obtained by irradiating with ultraviolet light to perform peeling and measuring the contact angle with water using the droplet method.

[0066] (180° peel strength)

[0067] The 180° peel strength S of the adhesive layer to the silicon wafer before ultraviolet irradiation is preferably 2.0 to 20.0 N / 20 mm at 23°C, more preferably 4.0 to 16.0 N / 20 mm, and even more preferably 6.0 to 12.0 N / 20 mm.

[0068] By achieving a 180° peel strength S of 2.0 N / 20 mm or higher, it tends to exhibit superior adhesion before UV irradiation. Therefore, the adhesive tape is less likely to peel off from the ring frame, and chip scattering is less likely to occur during the dicing process.

[0069] Furthermore, by setting the 180° peel strength S to 20 N / 20 mm or less, there is a tendency for the adhesive to be scraped off by the blade during the dicing process, and for the scraped adhesive to not easily adhere to the side of the substrate. Therefore, there is a tendency to further suppress the scraped adhesive from remaining as residue on the substrate, to allow UV curing to occur in this state to fix the chip, to cause pick-up defects, and to generate defects on the fixed chip.

[0070] The "180° peel strength to silicon wafer" described in this specification can be measured according to the adhesive strength test method of JIS Z0237 (2009). Specifically, the adhesive layer is pressed onto the cleaned substrate (silicon wafer) using a pressing device (roller mass 2 kg), and the adhesive strength when peeled from the substrate at 180° is measured using a universal tensile testing machine at an environment of 23°C and 50% humidity.

[0071] (Adhesive layer)

[0072] The adhesive layer contains a photoradical initiator and a polymer A with polymerizable carbon double bonds, and may also contain a curing agent and other components as needed.

[0073] (Polymer A)

[0074] Polymer A is a polymer with polymerizable carbon double bonds and is the main component constituting the adhesive layer. When the adhesive layer is irradiated with ultraviolet light, a photoradical initiator generates free radicals, thereby causing the polymerizable carbon double bonds of polymer A to polymerize individually. Thus, after ultraviolet irradiation, polymer A becomes cross-linked.

[0075] From the perspective of reducing pollution, it is preferable that polymer A contains fewer low molecular weight components. More specifically, the content of component A1, which has a weight average molecular weight of 20,000 or less, in polymer A is preferably 15 area% or less relative to the total area of ​​the gel permeation chromatography chromatogram, more preferably 10 area% or less, further preferably 8 area% or less, and even more preferably 5 area% or less. There is no particular limitation on the lower limit of the content of component A1, which is 0 area%. By keeping the content of component A1 at 15 area% or less, fewer low molecular weight components remain on the surface of the adhered object after ultraviolet irradiation, which tends to further reduce pollution.

[0076] In addition, the weight-average molecular weight of polymer A is preferably 1.0 × 10⁻⁶. 5 ~2.0×10 6 More preferably 2.0×10 5 ~1.0×10 6 More preferably 2.5×10 5 ~8.0×10 5 The weight-average molecular weight of polymer A is 1.0 × 10⁻⁶. 5 In addition to the increased presence of high molecular weight components, higher molecular weight also increases the likelihood of polymer A polymerizing with other polymers A via polymeric double bonds, thus potentially leading to further pollution reduction. The weight-average molecular weight of polymer A is 2.0 × 10⁻⁶. 6The following points highlight the advantages of polymer A: Firstly, polymer A is more mobile, increasing the chances of one polymer A polymerizing with others, thus further reducing contamination. Secondly, a smaller molecular weight prevents the adhesive's elastic modulus from becoming excessively high, leading to a tendency for improved adhesion under normal conditions. Thirdly, better conformability to the adhered surfaces, including height differences, avoids contamination caused by poor UV curing due to oxygen inhibition. Finally, the soft adhesive readily cures and shrinks under UV irradiation, significantly reducing post-curing adhesion.

[0077] The "weight-average molecular weight" stated in this specification is the molecular weight obtained by measuring a sample prepared by dissolving polymer A in tetrahydrofuran using a gel permeation chromatography analyzer. The content of component A1 can be determined by setting the chromatographic area of ​​polymer A to 100% and calculating the proportion of the chromatographic area of ​​the retention time for polymers with a weight-average molecular weight below 20,000 from the calibration curve of the molecular weight converted from standard polystyrene.

[0078] Furthermore, the glass transition point of polymer A is preferably -80 to 23°C, more preferably -70 to 10°C, and even more preferably -60 to 0°C. With a glass transition point of -80°C or higher, there is a tendency to further reduce contamination. Additionally, with a glass transition point of 23°C or lower, there is a tendency to further improve the adhesion to the adhered material.

[0079] There are no particular limitations on polymer A; for example, (meth)acrylate copolymers having polymerizable double bonds can be cited. The shape of the (meth)acrylate copolymer is not particularly limited; for example, linear, branched, or cross-linked shapes can be cited. A cross-linked shape is preferred. By using such a polymer A, the cohesive strength of the adhesive layer is increased, the adhesion to the adhered objects is further improved, and contamination is further reduced. Polymer A having a cross-linked or branched shape can be a polymer in which a portion of the polymerizable double bonds of a linear polymer A are bonded through aging or the like.

[0080] There are no particular limitations on the monomers of (meth)acrylates that constitute (meth)acrylate copolymers. Examples include alkyl (meth)acrylates having straight-chain or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, pentyl, isopentyl, hexyl, heptyl, cyclohexyl, 2-ethylhexyl, octyl, isooctyl, nonyl, isononyl, decyl, isodecyl, undecyl, lauryl, tridecyl, tetradecyl, stearyl, octadecyl, and dodecyl. These alkyl (meth)acrylates can be used alone or in combination with two or more.

[0081] In addition, there are no particular limitations on monomer components other than the aforementioned alkyl methacrylates, and examples include, for instance, acrylic acid, methacrylic acid, carboxyethyl methacrylate, carboxypentyl methacrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid, which contain carboxyl groups; anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl methacrylate, and so on. Hydroxyl monomers such as 1-hydroxydecyl methacrylate, 12-hydroxylaurate methacrylate, and (4-hydroxymethylcyclohexyl)methyl methacrylate; sulfonic acid monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamide propanesulfonic acid, (meth)acrylic acid sulfonyl propane, and (meth)acryloyloxynaphthalene sulfonic acid; and phosphate monomers such as 2-hydroxyethylacryloyl phosphate, preferably copolymers of 2-ethylhexyl methacrylate and methacrylic acid. These other monomers may be used alone or in combination of two or more.

[0082] Preferably, there are (meth)acrylate copolymers containing alkyl (meth)acrylates and hydroxyl-containing monomers, and (meth)acrylate copolymers containing alkyl (meth)acrylates and carboxyl-containing monomers.

[0083] There are no particular limitations on the methods for introducing polymerizable double bonds into (meth)acrylate copolymers. For example, methods can be described by reacting a modifier with polymerizable double bonds with the carboxyl group of a carboxyl-containing monomer, the anhydride carboxyl group of an anhydride monomer, or the hydroxyl group of a hydroxyl-containing monomer.

[0084] For example, by reacting an isocyanate compound having polymerizable double bonds as a modifier with a (meth)acrylate copolymer containing hydroxyl-containing monomer units, polymerizable double bonds can be introduced into the hydroxyl-containing monomer units via urethane bonds. Alternatively, as another example, by reacting an epoxy compound having polymerizable double bonds as a modifier with a (meth)acrylate copolymer containing hydroxyl-containing monomer units, polymerizable double bonds can be introduced into the hydroxyl-containing monomer units via ether bonds.

[0085] It should be noted that, as a modifier, any substance that has functional groups that react with the functional groups of (meth)acrylate copolymers and has polymerizable double bonds is acceptable, without any particular limitation. Examples include isocyanate compounds and epoxy compounds with polymerizable double bonds.

[0086] Furthermore, the amount of polymeric double bonds introduced is preferably 20 to 80 mol% relative to 100 mol% of the reactive monomer units constituting polymer A, more preferably 30 to 75 mol%, and even more preferably 40 to 70 mol%. It should be noted that, here, "reactive monomer units" refers to carboxyl-containing monomers, anhydride monomers, and hydroxyl-containing monomers. By introducing polymeric double bonds at 20 mol% or more, unreacted polymer A is less likely to remain after ultraviolet irradiation, thus further suppressing contamination. Additionally, by introducing polymeric double bonds at 80 mol% or less, excessive cross-linking can be suppressed, thus preventing the adhesive layer from deforming and breaking into a pin shape due to the pin's lifting action during pickup, thereby preventing adhesive residue. Furthermore, by introducing polymeric double bonds at 80 mol% or less, unreacted polar groups such as carboxyl groups are more likely to remain, further increasing the adhesive strength to the adhered objects before ultraviolet irradiation.

[0087] Polymer A preferably has hydroxyl groups. It should be noted that these hydroxyl groups can be derived from hydroxyl-containing monomers, hydroxyl groups from modifiers, or hydroxyl groups generated by reacting hydroxyl-containing monomers with modifiers. For example, a hydroxyl group generated by reacting a monomer unit such as a hydroxyl-containing monomer with a modifier can be described as a reaction between an epoxy compound having polymerizable double bonds and a hydroxyl-containing monomer.

[0088] Because polymer A has hydroxyl groups, when combined with the curing agent described later, the hydroxyl groups can be used to further crosslink multiple polymers, tending to further improve the cohesive strength of the adhesive layer. In addition, the anchoring strength between the substrate film and the adhesive layer is further improved, cohesive failure and anchoring failure are suppressed, and there is a tendency to obtain more stable adhesive properties.

[0089] The content of polymer A relative to the total amount of the adhesive layer is preferably 80 to 99.5% by mass, more preferably 85 to 99.5% by mass, and even more preferably 90 to 99.5% by mass. With the content of polymer A within the above range, there is a tendency to further suppress contamination.

[0090] (Photoradical initiator)

[0091] There are no particular limitations on photoradical initiators. Examples include alkylphenyl ketone photopolymerization initiators, acylphosphine oxide photopolymerization initiators, thioxanone photopolymerization initiators, aromatic ketones, aromatic ononium salts, organic peroxides, thiolated compounds (compounds containing phenyl thio groups, etc.), α-aminoalkylphenyl ketone compounds, hexaaryl biimidazole compounds, ketoxime esters, borate compounds, azadinium compounds, metallocene compounds, active ester compounds, compounds with carbon-halogen bonds, and alkylamine compounds.

[0092] Among them, alkylphenyl ketone-based photopolymerization initiators are preferred.

[0093] The content of the photoradical initiator relative to the total amount of the adhesive layer is preferably 0.1 to 5.0% by mass, more preferably 0.2 to 4.0% by mass, and even more preferably 0.3 to 3.0% by mass. With the content of the photoradical initiator within the above range, there is a tendency to further suppress contamination.

[0094] (Curing agent)

[0095] There are no particular limitations on the curing agent; examples include isocyanate compounds, epoxy compounds, and amine compounds. Isocyanate compounds are preferred. Using such a curing agent tends to further enhance the cohesive strength of the adhesive layer. These curing agents can be used alone or in combination of two or more.

[0096] As isocyanate compounds, there are no particular limitations. Examples include aromatic diisocyanates such as toluene diisocyanate, 4,4-diphenylmethane diisocyanate, and phenyl diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate and methylene bis(4-cyclohexyl) isocyanate; and aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate. They can be used individually or in combination of two or more.

[0097] The curing agent is preferably a polyfunctional isocyanate compound with two or more functional groups. By using such a curing agent, multiple polymers A can also crosslink through the curing agent, thus tending to further improve the cohesive strength of the adhesive layer. Furthermore, the anchoring strength between the substrate layer and the adhesive layer is also improved, tending to result in more stable adhesive properties.

[0098] The content of the curing agent relative to 100 parts by weight of polymer A is preferably 0.1 to 5.0 parts by weight, more preferably 0.3 to 4.0 parts by weight, and even more preferably 0.3 to 3.0 parts by weight. By having a curing agent content of 0.1 parts by weight or more, the crosslinking density of the adhesive layer is further increased, cohesive failure during peeling is further suppressed, and contamination caused by cohesive failure is further suppressed. Furthermore, by having a curing agent content of 5.0 parts by weight or less, the crosslinking density is further reduced, the elastic modulus is reduced, and therefore there is a tendency to further increase the adhesive strength.

[0099] Furthermore, the content of the curing agent relative to the total amount of the adhesive layer is preferably 0.1 to 2.0% by mass, more preferably 0.2 to 1.5% by mass, and even more preferably 0.3 to 1.0% by mass. By keeping the content of the curing agent within the above range, there is a tendency to further suppress contamination.

[0100] (Other additives)

[0101] In this embodiment, the adhesive layer may be supplemented with other additives such as tackifiers, crosslinking delay agents, and antioxidants as needed.

[0102] There are no particular limitations on what can be used as a tackifier. Examples include petroleum-based resins, terpene resins, terpene-phenolic resins, aromatic modified terpene resins, coumarone-indene resins, natural resin rosin, modified rosin, glycerol ester rosin, pentaerythritol ester rosin, phenolic resins, xylene resins, alicyclic petroleum resins, styrene-based resins, and dicyclopentadiene resins.

[0103] There are no particular limitations on the crosslinking retarder. For example, it can be a compound that, in an adhesive composition containing an isocyanate-based curing agent, can suppress excessive viscosity increase of the adhesive composition by end-capping the isocyanate groups of the curing agent. Examples of such crosslinking retarders include β-diketones such as acetylacetone, hexane-2,4-dione, heptane-2,4-dione, and octane-2,4-dione; β-keto esters such as methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, butyl acetoacetate, octyl acetoacetate, oleic acid acetoacetate, lauryl acetoacetate, and stearyl acetoacetate; and benzoylacetone.

[0104] As antioxidants, there are no particular limitations; examples include methyl hydroquinone, hydroquinone, 2,2-methylene-bis(4-methyl-6-tert-butylphenol), catechol, hydroquinone monomethyl ether, monotert-butyl hydroquinone, 2,5-ditert-butyl hydroquinone, p-benzoquinone, 2,5-diphenyl-p-benzoquinone, 2,5-ditert-butyl-p-benzoquinone, picric acid, citric acid, phenothiazine, tert-butylcatechol, 2-butyl-4-hydroxyanisole, 2,6-ditert-butyl-p-cresol, and 4-[[4,6-bis(octylthio)-1,3,5-triazin-2-yl]amino]-2,6-ditert-butylphenol.

[0105] (thickness)

[0106] The thickness of the adhesive layer is typically 1.0 to 250 μm, preferably 2.0 to 50 μm. More preferably 5.0 to 40 μm. By making the thickness of the adhesive layer 1.0 μm or more, sufficient adhesion can be ensured, thus easily suppressing the scattering of semiconductor chips separated by expansion. In addition, by making the thickness of the adhesive layer 250 μm or less, there is a tendency to further reduce costs.

[0107] When used as a tape for semiconductor wafer processing, the thickness of the substrate layer and the adhesive layer is preferably adjusted within the above-mentioned range so that the total thickness of the tape is preferably in the range of 60 to 250 μm. More preferably, the thickness of the tape for semiconductor wafer processing is in the range of 70 to 200 μm, and even more preferably, in the range of 80 to 180 μm.

[0108] (Substrate layer)

[0109] There are no particular limitations on the materials constituting the substrate layer. Examples include polyvinyl chloride, polyethylene terephthalate, ethylene-vinyl acetate copolymer, ethylene-acrylate-acrylate film, ethylene-ethyl acrylate copolymer, polyethylene, polypropylene, propylene copolymers, ethylene-acrylate copolymers, and ionomer resins obtained by crosslinking ethylene-(meth)acrylate copolymers and ethylene-(meth)acrylate-(meth)acrylate copolymers with metal ions. The substrate film constituting the substrate layer can be a single resin, a mixture of two or more of these resins, a copolymer, or a laminate thereof.

[0110] The thickness of the substrate layer can be appropriately selected within a range that does not impair operability. The thickness of the substrate layer is typically 10–500 μm, preferably 50–200 μm, and more preferably 70–150 μm. Adjusting the thickness of the substrate layer within the above range is practically feasible and economically effective. When the substrate layer is composed of multiple substrate films, it is preferable to adjust the thickness so that the overall thickness of the substrate layer falls within the above range.

[0111] To improve adhesion to the adhesive layer, the substrate layer may be subjected to chemical or physical surface treatments as needed. Examples of such surface treatments include corona treatment, chromic acid treatment, ozone exposure, flame exposure, high-voltage electric shock exposure, and ionization radiation treatment.

[0112] (Protective film)

[0113] For the adhesive tape of this embodiment, a protective film may also be attached to the adhesive layer to protect the adhesive layer. Since the protective film is peeled off during use of the adhesive tape, a protective film with excellent peelability is preferred. There are no particular limitations on the protective film; for example, films with low surface energy formed of fluororesin or films whose surface of polyethylene terephthalate has been treated with an organosilicon-based release agent can be cited.

[0114] (use)

[0115] The adhesive tape of this embodiment is preferably used for processing semiconductor wafers, semiconductor devices, or various semiconductor packages. A semiconductor wafer can also be a wafer before it is formed into a single piece, such as an electronic circuit. Furthermore, a semiconductor device refers to various monolithically formed semiconductor chips or components containing them, and a semiconductor package refers to a package on which a resin for protection and connection terminals for connecting the semiconductor chip to the outside are attached.

[0116] (Manufacturing method of adhesive tape)

[0117] There are no particular limitations on the manufacturing method of adhesive tape; for example, a method of forming an adhesive layer on a substrate layer can be cited.

[0118] The substrate layer of the adhesive tape in this embodiment can be manufactured according to known techniques. There are no particular limitations on the method for forming the substrate layer; various mixing devices (single-screw or two-screw extruders, rollers, Banbury mixers, various kneaders, etc.) are used to mix the aforementioned materials in a manner that ensures uniform dispersion of each component. This mixture is then formed into a substrate using a T-die method, calendering, or blow molding. A film-forming method using a T-die extruder with high thickness accuracy is preferred.

[0119] The adhesive layer of the adhesive tape in this embodiment can be manufactured according to known techniques. The method for forming the adhesive layer is not particularly limited; the various materials described above are dissolved in a solvent such as an organic solvent to form a resin liquid, which is then applied to a protective film using methods such as doctor blade coating, roller coating, spraying, gravure coating, bar coating, or curtain coating. The solvent is then removed, thereby forming the adhesive layer. The adhesive tape is then manufactured by bonding it to a substrate layer.

[0120] In this embodiment, an aging treatment can be performed after the adhesive layer is formed. During the aging treatment, the formed adhesive layer is stored at a specified temperature. The temperature conditions are not particularly limited, but are preferably 30–50°C, more preferably 35–45°C. Furthermore, the storage time is not particularly limited, but is preferably 24–150 hours, more preferably 48–100 hours. Through this aging treatment, the adhesive strength and curing characteristics of the adhesive layer change. Additionally, the tensile modulus of elasticity and elongation at break after ultraviolet irradiation can also be controlled within the aforementioned preferred ranges.

[0121] [Processing Method]

[0122] The processing method of this embodiment includes a bonding step of bonding the adhesive tape to the substrate and a dicing step of processing the substrate while the adhesive tape and the substrate are bonded together. It is a method for processing semiconductor wafers, semiconductor devices, or various semiconductor packages that are the substrates. Furthermore, the processing method of this embodiment may, as needed, include an ultraviolet irradiation step of irradiating the adhesive tape with ultraviolet light after the dicing step, and a pick-up step of picking up the monolithized chip from the ultraviolet-irradiated adhesive tape.

[0123] There are no particular limitations on the method of wafer dicing; previously known methods can be used. For example, silicon wafers can be diced into semiconductor chips by using a dicing device to rotate a dicing blade containing diamond abrasive grains at high speed.

[0124] There are no particular limitations on the ultraviolet irradiation method; previously known methods can be used. For example, an ultraviolet irradiation device can be used to irradiate the adhesive tape in the dicing process with ultraviolet light.

[0125] Then, there are no particular restrictions on the picking method, and previously known methods can be used. For example, an extension device can be used to stretch the UV-irradiated adhesive tape along the surface direction, and the chips can be picked up by the picking device while the chips are separated.

[0126] Example

[0127] The present invention will now be described in more detail using examples and comparative examples, but the present invention is not limited to these examples.

[0128] (Example 1)

[0129] 63 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of 2-hydroxyethyl acrylate, 22 parts by weight of ethoxyethoxyethyl acrylate, and 0.03 parts by weight of initiator (azobisisobutyronitrile) were copolymerized in ethyl acetate at 65°C for 24 hours to obtain a solution containing an acrylic polymer.

[0130] The hydroxyl group of the 2-hydroxyethyl acrylate unit in the acrylic polymer is reacted with 2-methacryloyloxyethyl isocyanate to obtain a side-chain double-bond-introduced acrylic polymer. In this case, the reaction is carried out with the amount of 2-methacryloyloxyethyl isocyanate introduced being 50 moles (50 mol%) relative to 100 moles of the 2-hydroxyethyl acrylate unit in the acrylic polymer.

[0131] Next, to a solution containing 100 parts by weight of a side-chain double-bond introduced acrylic polymer, 0.5 parts by weight of a trimethylolpropane-modified toluene diisocyanate curing agent (Coronate L-45E, Nippon Polyurethane Co., Ltd.) and 2.1 parts by weight of a photoradical initiator (2,2-dimethoxy-2-phenylacetophenone (BASF Omnirad 651)) were added to prepare a resin composition as a UV-curable adhesive.

[0132] The resin composition was applied to the release-treated surface of a pre-treated polyethylene terephthalate protective film, such that the dried adhesive layer had a thickness of 20 μm. After drying at 100°C for 1 minute, it was bonded to the corona-treated surface of an ionomer film (substrate resin film) of an ethylene-methacrylate-acrylate copolymer, on which the adhesive layer had been pre-corona-treated, thus transferring the adhesive onto the substrate resin film. The film was then aged at 40°C for 72 hours to obtain the adhesive tape.

[0133] (Example 2)

[0134] 67 parts by weight of butyl acrylate, 28 parts by weight of methyl acrylate, 5 parts by weight of 2-hydroxyethyl acrylate, and 0.03 parts by weight of initiator (azobisisobutyronitrile) were copolymerized in toluene at 65°C for 24 hours to obtain a solution containing an acrylic polymer. The hydroxyl groups of the 2-hydroxyethyl acrylate units in this acrylic polymer were reacted with 2-methacryloyloxyethyl isocyanate to obtain a side-chain double-bond-introduced acrylic polymer. In this case, the reaction was carried out with the amount of 2-methacryloyloxyethyl isocyanate introduced at 70 mol (70 mol%) relative to 100 mol of the 2-hydroxyethyl acrylate units in the acrylic polymer. The acrylic polymer was dissolved in a solution of ethyl acetate:methanol = 1:20 and washed with a solids concentration of 20% to remove low molecular weight components. An adhesive tape was then obtained in the same manner as in Example 1.

[0135] (Example 3)

[0136] The cleaning step for the acrylic polymer is omitted; otherwise, the procedure is the same as in Example 2 to obtain the adhesive tape.

[0137] (Example 4)

[0138] The two were reacted in such a way that the amount of 2-methacryloyloxyethyl isocyanate introduced was 30 moles (30 mol%) relative to 100 moles of 2-hydroxyethyl acrylate units of the acrylic polymer, and otherwise the same procedure as in Example 1 was followed to obtain the adhesive tape.

[0139] (Example 5)

[0140] Except for adjusting the amount of initiator to make the weight-average molecular weight of the side-chain double-bond-introduced acrylic polymer 800,000, the same procedure as in Example 1 was followed to obtain the adhesive tape.

[0141] (Example 6)

[0142] 92 parts by weight of 2-ethylhexyl acrylate, 8 parts by weight of acrylic acid, and 0.05 parts by weight of initiator (azobisisobutyronitrile) were copolymerized in ethyl acetate at 65°C for 24 hours to obtain a solution containing an acrylic polymer.

[0143] Glycidyl methacrylate is reacted with the carboxyl groups of the acrylic units in the acrylic polymer to obtain a side-chain double-bond-introduced acrylic polymer. In this case, the reaction is carried out with the amount of glycidyl methacrylate introduced being 80 moles (80 mol%) relative to 100 moles of the acrylic units in the acrylic polymer. The acrylic polymer is then dissolved in a solution of ethyl acetate:methanol = 1:20 and washed with a solids concentration of 20% to remove low molecular weight components.

[0144] Next, 0.1 parts by weight of trimethylolpropane-modified toluene diisocyanate curing agent (Coronate L-45E, Nippon Polyurethane Co., Ltd.) and 2.1 parts by weight of 2,2-dimethoxy-2-phenylacetophenone (Omnirad 651, BASF) as photoradical initiators were added to a solution containing 100 parts by weight of a side-chain double-bond introduced acrylic polymer to prepare a resin composition as a UV-curable adhesive. An adhesive tape was then obtained in the same manner as in Example 1.

[0145] (Example 7)

[0146] When reacting the carboxyl groups of the acrylic units in the acrylic polymer with glycidyl methacrylate to obtain a side-chain double-bond introduced acrylic polymer, the reaction was carried out in such a way that the amount of glycidyl methacrylate introduced was 60 moles (60 mol%) relative to 100 moles of the acrylic units in the acrylic polymer; the trimethylolpropane-modified toluene diisocyanate curing agent (Coronate L-45E, Nippon Polyurethane Co., Ltd.) as a polyisocyanate compound was 0.5 parts by weight, and the same procedure as in Example 6 was followed to obtain the adhesive tape.

[0147] (Comparative Example 1)

[0148] The cleaning step of the acrylic polymer was omitted, and the trimethylolpropane-modified toluene diisocyanate curing agent (Coronate L-45E, Nippon Polyurethane Co., Ltd.) was used as a polyisocyanate compound in a quantity of 0.5 parts by weight. Otherwise, the same procedure as in Example 6 was followed to obtain the adhesive tape.

[0149] (Comparative Example 2)

[0150] 45 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of 2-hydroxyethyl acrylate, 40 parts by weight of methyl acrylate, 5.0 parts by weight of acrylic acid, and 0.03 parts by weight of initiator (azobisisobutyronitrile) were copolymerized in ethyl acetate at 65°C for 24 hours to obtain a solution containing an acrylic polymer.

[0151] An adhesive tape was prepared by adding a UV-polymerizable urethane acrylate to the acrylic polymer and adjusting the amounts of curing agent and initiator, otherwise following the same procedure as in Example 1.

[0152] For the samples prepared as described above, the following evaluation tests were conducted to assess organic contamination, contact angle, molecular weight, adhesion to silicon wafers after 180° peel, dicing, and pick-up. The results are summarized in Table 1 below.

[0153] <Organic Pollution>

[0154] The adhesive tape prepared as described above is attached to the prime wafer. After 24 hours, it is irradiated with a high-pressure mercury lamp at 150 mJ / cm². 2 Ultraviolet light was used for stripping. Then, the volatile organic compounds on the surface of the original wafer were determined by TD-GC / MS. The determination conditions for TD-GC / MS are shown below.

[0155] (Measurement conditions)

[0156] Sample pretreatment: The organic adsorbed material on the wafer is recovered into the TENAX tube using the following device.

[0157] • Device: “WA2560M” (manufactured by GL Sciences)

[0158] Heating conditions: Room temperature → approximately 25℃ / min increase → 400℃ (hold for 15 minutes)

[0159] • Adsorption conditions: Tenax tube (room temperature)

[0160] TD-GC / MS

[0161] • Measuring device: "TD2530" (manufactured by GL Sciences)

[0162] ·Agilent Technologies 7890B GC System

[0163] ·Agilent Technologies 5977A MSD

[0164] • TENAX tube desorption temperature: 270℃

[0165] • GC introduction method: After a -130℃ cold trap, heat to 270℃

[0166] • Column: InertCap 1MS (Length: 60m, Diameter: 0.25mm, Film: 0.25μm)

[0167] Carrier gas: He

[0168] • Ionization method: EI method

[0169] GC heating conditions: 40℃ (hold for 5 min) → 10℃ / min increase → 280℃ (hold for 11 min)

[0170] Original wafer used: 6 inches, particles: ≤15 particles with a diameter of 0.3μm

[0171] <Contact Angle>

[0172] The adhesive tape prepared as described above is attached to a silicon wafer. After being placed at 23°C for 24 hours, it is irradiated with a high-pressure mercury lamp at 150 mJ / cm². 2 The silicon wafer was subjected to ultraviolet light for peeling. Then, the contact angle R1 of the silicon wafer surface with distilled water was measured using the droplet method. The contact angle R0 of the silicon wafer with distilled water before the adhesive tape was applied was also measured, and the difference |R0-R1| was calculated. The measurement conditions for the droplet method are shown below.

[0173] (Measurement conditions)

[0174] • Water droplets: 3mL

[0175] • 30 measurements per second, use the value of the 30th measurement × n³

[0176] <Weight-average molecular weight>

[0177] 10 mg of the synthesized side-chain double-bond-directed acrylic polymer was dissolved in 10 mL of tetrahydrofuran (THF, stabilizer-free, manufactured by Wako Pharmaceutical Co., Ltd.), filtered through a PTFE 0.50 μm membrane filter, and the resulting product was used for analysis. The conditions for determining the weight-average molecular weight are shown below.

[0178] (Analytical apparatus)

[0179] Gel permeation chromatography analysis apparatus (DGU-20AC, etc., manufactured by Shimadzu Corporation)

[0180] (Measurement conditions)

[0181] Standard material: Shodex STANDARD (Type: SM-105, manufactured by Showa Denko Co., Ltd.)

[0182] Sample introduction volume: 20 μL

[0183] Mobile phase: THF

[0184] Flow rate: 1 mL / min

[0185] Column: Shim-pack GPC-80M (300mm × 8.0mm I.D.)

[0186] Column temperature: 40℃

[0187] Detector: Differential Refractive Index Detector (RID)

[0188] It should be noted that the content of component A1, which has a weight average molecular weight of less than 20,000, is determined by calculating the proportion of the area of ​​the chromatogram of the retention time of the component with a weight average molecular weight of less than 20,000 using a calibration curve with the area of ​​the chromatogram of the side chain double bond introduced acrylic polymer as 100% of the area and the molecular weight converted from standard polystyrene.

[0189] <Glass transition point>

[0190] The glass transition point of polymer A was determined according to JIS K7121 by differential scanning calorimetry (DSC).

[0191] <180° peel strength>

[0192] The adhesive strength of the adhesive tape was determined according to the method for determining adhesive strength in JIS Z0237 (2009) (Method 1: Test method of peeling tape and sheet relative to a stainless steel test plate at 180°). Specifically, the adhesive tape was pressed onto a cleaned silicon wafer using a pressing device (roller mass 2 kg), and the test was performed using a universal tensile testing machine (Orientec Tensilon model: RTG-1210) at an environment of 23°C and 50% humidity.

[0193] (Measurement conditions)

[0194] Measurement mode: Tension

[0195] Stretching speed: 300mm / min

[0196] Chuck spacing: 50mm

[0197] Sample width measured: 20 mm

[0198] <Slicing Process>

[0199] Using a tape mounting device with rollers, apply the adhesive tape prepared above to the back of an 8-inch diameter × 0.1mm thick silicon wafer. Next, use a dicing blade to dice the silicon wafer into 0.49mm × 0.3mm semiconductor chips. The main dicing settings are as follows.

[0200] (Setting conditions)

[0201] Dividing device: DISCO DAD341

[0202] Dicing blade: DISCO NBC-ZH205O-27HEEE

[0203] Dicing blade speed: 40,000 rpm

[0204] Dividing blade feed rate: 50 mm / s

[0205] Cutting water temperature: 25℃

[0206] Cutting water flow rate: 1.0 liters / minute

[0207] <Pickup Process>

[0208] After the scribing process, irradiate with 150 mJ / cm 2 Ultraviolet light is used to cure the adhesive layer. Then, the semiconductor chip is picked up from the adhesive tape and peeled off. The main setup conditions for picking are as follows.

[0209] (Setting conditions)

[0210] Pickup device: CAP-300II manufactured by Canon Machinery

[0211] Pin shape: 250μmR

[0212] Pin lifting height: 0.5mm

[0213] Extension range: 8mm

[0214] Lifting speed: 10,000 μm / s

[0215] <Pickup Rate>

[0216] For the pin height during pickup, pickup tests were conducted in 0.1mm increments from 0.1mm to 1.5mm. More specifically, 100 chips were picked up at each pin height, and the percentage of chips that could be picked up at each pin height (pickup yield) was determined. Furthermore, the minimum pin height at which the chip pickup yield reached 95% or higher was recorded in a table.

[0217] [Table 1]

[0218] ※R0 is 5.0.

[0219] Industrial availability

[0220] The adhesive tape of the present invention is industrially applicable as an adhesive tape for semiconductor wafer processing, particularly as an adhesive tape used in the dicing process.

Claims

1. An adhesive tape having a substrate layer and an adhesive layer disposed thereon, The adhesive layer comprises a photoradical initiator, a curing agent, and a polymer A having polymerizable carbon double bonds. The difference between the water contact angle R0 of the silicon wafer surface and the water contact angle R1 of the silicon wafer surface after the adhesive layer is attached to the silicon wafer and left for 24 hours, the adhesive layer is irradiated with ultraviolet light, and the adhesive layer is then peeled off, |R0-R1|, is less than 20°. The content of component A1, which has a weight average molecular weight of less than 20,000, in polymer A is less than 8% of the total area of ​​the gel permeation chromatography chromatogram. The polymer A, which has polymerizable carbon double bonds, comprises a copolymer of (meth)acrylate alkyl esters and (meth)acrylate monomers containing hydroxyl groups. The polymerizable double bond is introduced into the unit of the hydroxyl-containing monomer by reacting an isocyanate compound with the (meth)acrylate copolymer. The amount of the polymeric double bond introduced is 20-70 mol% relative to 100 mol% of the hydroxyl-containing monomer unit of the polymer A having a polymeric carbon double bond. The content of the photoradical initiator is 0.1~5.0% by mass relative to the total amount of the adhesive layer. The content of the curing agent is 0.1 to 2.0% by mass relative to the total amount of the adhesive layer.

2. The adhesive tape according to claim 1, wherein, The 180° peel strength of the adhesive layer to the silicon wafer before ultraviolet irradiation is 2.0 to 20.0 N / 20 mm at 23°C.

3. The adhesive tape according to claim 1 or 2, wherein, The weight-average molecular weight of polymer A is 1.0 × 10⁻⁶. 5 ~2.0×10 6 .

4. The adhesive tape according to claim 1 or 2, wherein, The glass transition point of polymer A is -80 to 23°C.

5. The adhesive tape according to claim 1 or 2, wherein, The (meth)acrylate copolymer has a linear, branched, or cross-linked shape.

6. The adhesive tape according to claim 1 or 2, wherein, The curing agent contains isocyanate compounds.

7. The adhesive tape according to claim 6, wherein, The isocyanate compounds include polyfunctional isocyanate compounds with two or more functions.

8. The adhesive tape according to any one of claims 1, 2, and 7, wherein, The content of the curing agent is 0.1 to 5.0 parts by weight relative to 100 parts by weight of polymer A.

9. The adhesive tape according to any one of claims 1, 2 and 7, used for processing semiconductor wafers, semiconductor devices or various semiconductor packages.

10. The processing method, which has the following characteristics: The bonding process of attaching the adhesive tape according to any one of claims 1 to 9 to the substrate; and A dicing process in which the adhesive tape is bonded to the substrate and the substrate is individually cut into pieces. The adhered object is a semiconductor wafer, semiconductor device, or various semiconductor packages.