Pressure-sensitive adhesive tape for processing semiconductor wafer

Abstract

The invention relates to a pressure-sensitive adhesive tape for semiconductor wafer processing. The present invention provides a pressure-sensitive adhesive tape for processing a semiconductor wafer, the pressure-sensitive adhesive tape for processing a semiconductor wafer having excellent concave-convex embedding properties and suppressing the occurrence of adhesive residue on the surface of a semiconductor wafer. The pressure-sensitive adhesive tape for semiconductor wafer processing includes: a base material; and a pressure-sensitive adhesive layer formed from an active energy ray-curable pressure-sensitive adhesive. The quotient Y (IA / TA) of the viscosity value TA (gf) of the pressure-sensitive adhesive layer measured by the probe viscosity method and the integral value IA (gf * sec) and the surface free energy X (mN / m) of the pressure-sensitive adhesive layer satisfy the relationship of formula (1): Ygt; and 0.01 X <-0.21 > (1).

Description

[0001] This application claims the benefit of Japanese Patent Application No. 2024-015268, filed on February 2, 2024, which is hereby incorporated by reference herein. Technical Field

[0002] The present invention relates to a pressure-sensitive adhesive tape for semiconductor wafer processing. Background Art

[0003] Semiconductor wafers are used in a variety of applications such as personal computers, smart phones and cars. In the processing steps of semiconductor wafers, pressure-sensitive adhesive tapes are used to protect their surfaces during processing. In recent years, the miniaturization and high functionality of large-scale integrated circuits (LSIs) have been continuously developed, and the surface structure of wafers has become complicated. Its specific example is that the three-dimensional structure of the wafer surface has become complicated by solder bumps, etc. Therefore, the pressure-sensitive adhesive tape used in the semiconductor wafer processing steps is required to have the property of embedding the concavo-convex surface of the wafer therein and strong pressure-sensitive adhesiveness.

[0004] In recent years, with the miniaturization and thinning of products, the thinning of semiconductor wafers has been continuously developed. In the wafer processed into a thin shape, when the pressure-sensitive adhesive strength of the pressure-sensitive adhesive tape is too high, the wafer may be damaged when the pressure-sensitive adhesive tape is peeled off. In view of this, in order to prevent the paste residue on the adherend and the damage to the wafer during peeling, a pressure-sensitive adhesive tape using an ultraviolet curing pressure-sensitive adhesive has been proposed (for example, Japanese Patent Application Laid-Open No. 2020-017758 and Japanese Patent Application Laid-Open No. 2013-213075). In addition, as a pressure-sensitive adhesive tape suitable for processing semiconductor wafers with a concave-convex structure such as a bump, a pressure-sensitive adhesive tape with excellent concave-convex embedding property has been proposed (for example, Japanese Patent Application Laid-Open No. 2022-121480). Summary of the Invention

[0005] Pressure-sensitive adhesive tapes with excellent unevenness and convexity embedding properties may leave adhesive residue on the surface of semiconductor wafers after the tape is peeled off. The present invention is made to solve the above-mentioned problems of the prior art and provides a pressure-sensitive adhesive tape for semiconductor wafer processing that has excellent unevenness and convexity embedding properties and suppresses adhesive residue on the surface of semiconductor wafers.

[0006] 1. According to at least one embodiment of the present invention, there is provided a pressure-sensitive adhesive tape for semiconductor wafer processing, comprising: a substrate; and a pressure-sensitive adhesive layer formed of an active energy ray-curable pressure-sensitive adhesive. The tack value T of the pressure-sensitive adhesive layer measured by a probe tack method is A (gf) and integral value I A (gf·second) quotient Y(I A / T A) and the surface free energy X (mN / m) of the pressure-sensitive adhesive layer satisfy the relationship of formula (1).

[0007] Y>0.01X-0.21(1)

[0008] 2. In the pressure-sensitive adhesive tape for semiconductor wafer processing according to the above item 1, the active energy ray-curable pressure-sensitive adhesive may contain a (meth)acrylic polymer, and the (meth)acrylic polymer may be a polymer obtained by polymerizing a monomer composition containing 60 mol % or more of a (meth)acrylic monomer having a side chain having 8 or more carbon atoms.

[0009] 3. In the pressure-sensitive adhesive tape for semiconductor wafer processing according to item 2 above, the monomer composition may contain 39 mol % or less of at least one member selected from the group consisting of highly polar monomers and monomers having a side chain having 2 or less carbon atoms.

[0010] 4. In the pressure-sensitive adhesive tape for semiconductor wafer processing according to the above item 3, the highly polar monomer may be a hydroxyl group-containing monomer having a side chain with 4 or less carbon atoms.

[0011] 5. In the pressure-sensitive adhesive tape for semiconductor wafer processing according to the above item 4, the monomer composition may contain 10 mol % to 39 mol % of the hydroxyl group-containing monomer having a side chain with 4 or less carbon atoms.

[0012] 6. The pressure-sensitive adhesive tape for semiconductor wafer processing according to any one of items 1 to 5 above may further include an intermediate layer.

[0013] 7. The pressure-sensitive adhesive tape for semiconductor wafer processing according to any one of items 1 to 6 above may be a back grinding tape. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic cross-sectional view of a pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention.

[0015] Figure 2 Schematic cross-sectional view of a pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention. DETAILED DESCRIPTION

[0016] A. Overview of Pressure-Sensitive Adhesive Tapes for Semiconductor Wafer Processing

[0017] A pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention includes a base material and a pressure-sensitive adhesive layer formed of an active energy ray-curable pressure-sensitive adhesive. Figure 11 is a schematic cross-sectional view of a pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention. In the illustrated example, the pressure-sensitive adhesive tape 100 for semiconductor wafer processing includes a substrate 10 and a pressure-sensitive adhesive layer 20. The pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention preferably further includes an intermediate layer. Figure 2 1 is a schematic cross-sectional view of a pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention. In at least one embodiment, the pressure-sensitive adhesive tape 100 for semiconductor wafer processing includes, in this order, a substrate 10, an intermediate layer 30, and a pressure-sensitive adhesive layer 20. In actual use, a release liner may be temporarily and releasably attached to the pressure-sensitive adhesive layer 20 in the pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention until use.

[0018] In the pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention, the tack value T of the pressure-sensitive adhesive layer measured by the probe tack method is A (gf) and integral value I A (gf·second) quotient Y(I A / T A ) and the surface free energy X (mN / m) of the pressure-sensitive adhesive layer satisfy the relationship of formula (1). When the relationship of formula (1) is satisfied, a pressure-sensitive adhesive tape for semiconductor wafer processing can be provided that has excellent concave-convex embeddability and suppresses the occurrence of adhesive residue on the surface of the semiconductor wafer.

[0019] Y>0.01X-0.21(1)

[0020] Here, the tack value T of the pressure-sensitive adhesive layer used in this specification measured by the probe tack method is A and integral value I A This refers to the value measured by the probe viscosity method using a probe viscosity tester using the following operating procedures.

[0021] The pressure-sensitive adhesive tape was fixed to the glass slide by attaching the substrate surface of the pressure-sensitive adhesive tape to the glass slide via double-sided tape. Next, a probe with a probe diameter of 5 mm was pressed against the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape at a contact speed of 120 mm / min, and a load of 10 gf was applied so that the probe and the pressure-sensitive adhesive layer were in contact for 1 second. Next, the probe was lifted at a peeling speed of 600 mm / min, and the peak value at the time of peeling was defined as the tack value T. A (gf), the peak area is defined as the integral value I A (gf·seconds). Each value is determined accordingly.

[0022] In the pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention, the tack value T A(gf) and integral value I A (gf·second) quotient Y(I A / T A ) preferably satisfies the following formula (2). The pressure-sensitive adhesive tape for semiconductor wafer processing that satisfies the relationship of formula (2) has better concave-convex embedding properties and can further suppress the occurrence of adhesive residue on the surface of the semiconductor wafer.

[0023] Y<0.02X-0.33(2)

[0024] In the pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention, the tack value T A (gf) and integral value I A (gf·second) quotient Y(I A / T A ) preferably satisfies the following formula (3). The pressure-sensitive adhesive tape for semiconductor wafer processing that satisfies the relationship of formula (3) has better concave-convex embedding properties and can further suppress the occurrence of adhesive residue on the surface of the semiconductor wafer.

[0025] Y>-0.012X+0.288(3)

[0026] In the pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention, the tack value T A (gf) and integral value I A (gf·second) quotient Y(I A / T A ) preferably satisfies the following formula (4). The pressure-sensitive adhesive tape for semiconductor wafer processing that satisfies the relationship of formula (4) has better concave-convex embedding properties and can further suppress the occurrence of adhesive residue on the surface of the semiconductor wafer.

[0027] Y<0.0107X-0.1861(4)

[0028] The pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention may further include any appropriate layer in addition to the substrate, the intermediate layer, and the pressure-sensitive adhesive layer. The tape may further include, for example, an antistatic layer. The presence of the antistatic layer can prevent electrostatic damage to the semiconductor element caused by static electricity when the pressure-sensitive adhesive tape for semiconductor wafer processing is peeled off.

[0029] The thickness of the pressure-sensitive adhesive tape for semiconductor wafer processing can be set to any appropriate range, and is preferably 10 μm to 1000 μm, more preferably 30 μm to 300 μm, and still more preferably 40 μm to 200 μm.

[0030] B. Substrate

[0031] The substrate may include any suitable resin. Specific examples of substrate-forming resins include polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polybutylene naphthalate (PBN); polyolefin resins such as ethylene-vinyl acetate copolymers, ethylene-methyl methacrylate copolymers, polyethylene, polypropylene, and ethylene-propylene copolymers; polyvinyl alcohol; polyvinylidene chloride; polyvinyl chloride; vinyl chloride-vinyl acetate copolymers; polyvinyl acetate; polyamide; polyimide; cellulose; fluorine-containing resins; polyether; polystyrene resins such as polystyrene; polycarbonate; and polyethersulfone. Among them, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate are preferably used.

[0032] The substrate may further include any other ingredients to the extent that the effects of the present invention are not impaired. Examples of other ingredients include antioxidants, ultraviolet light absorbers, light stabilizers, and heat stabilizers. Other ingredients may be used in any appropriate amount according to the purpose.

[0033] In at least one embodiment of the present invention, the substrate has an antistatic function. When the substrate has an antistatic function, the generation of static electricity when the tape is peeled off is suppressed, and the destruction of the circuit and the attachment of foreign matter caused by static electricity can be prevented. The substrate can have an antistatic function by being formed from a resin containing an antistatic agent, or can have an antistatic function by applying a composition containing an antistatic component such as a conductive polymer, an organic or inorganic conductive substance, or an antistatic agent to any appropriate film to form an antistatic layer. When the substrate includes an antistatic layer, it is preferred that an intermediate layer is laminated on the surface on which the antistatic layer is formed. When the substrate has an antistatic function, the surface resistance value of the substrate is, for example, 1.0×10 2 Ω / □ to 1.0×10 13 Ω / □.

[0034] The thickness of the substrate can be set to any appropriate value. The thickness of the substrate is preferably 10 μm to 200 μm, more preferably 20 μm to 150 μm.

[0035] The elastic modulus of base material can be set to any appropriate value.The elastic modulus of base material is preferably 50MPa to 6000MPa, more preferably 70MPa to 5000MPa.When elastic modulus falls into the above-mentioned scope of mentioning, it is possible to obtain the semiconductor wafer processing pressure-sensitive adhesive tape that can suitably follow the concavo-convex of adherend surface.

[0036] C. Pressure-sensitive adhesive layer

[0037] The pressure-sensitive adhesive layer can be formed by using any appropriate active energy ray-curable pressure-sensitive adhesive. The pressure-sensitive adhesive typically contains a base polymer. When the pressure-sensitive adhesive layer is formed by an active energy ray-curable pressure-sensitive adhesive, a pressure-sensitive adhesive tape for semiconductor wafer processing with excellent light peelability can be obtained.

[0038] The storage elastic modulus of the pressure-sensitive adhesive layer before active energy ray irradiation is preferably 0.020MPa to 0.25MPa, more preferably 0.025MPa to 0.20MPa, and even more preferably 0.03MPa to 0.18MPa. When the storage elastic modulus falls within the above-mentioned range, the pressure-sensitive adhesive layer can satisfactorily adhere closely to the semiconductor wafer used as an adherend. The storage elastic modulus of the pressure-sensitive adhesive layer can be measured, for example, using a viscoelasticity measuring device.

[0039] The contact angle of the pressure-sensitive adhesive layer with water is preferably 95° to 125°, more preferably 100° to 120°. Furthermore, the contact angle of the pressure-sensitive adhesive layer with diiodomethane is preferably 55° to 85°, more preferably 60° to 80°.

[0040] The surface free energy X of the pressure-sensitive adhesive layer can be set to any appropriate value to satisfy formula (1). The surface free energy X is preferably 10mN / m to 40mN / m, more preferably 15mN / m to 30mN / m, and even more preferably 20mN / m to 25mN / m. When the surface free energy of the pressure-sensitive adhesive layer falls within the above-mentioned range, the affinity with the semiconductor wafer surface used as adherend is adjusted to an appropriate range, and when the pressure-sensitive adhesive layer is attached to the adherend, it shows appropriate pressure-sensitive adhesive strength, so it is possible to suppress the paste from remaining on the adherend after peeling off the pressure-sensitive adhesive tape. The surface free energy X of the pressure-sensitive adhesive layer used in this specification refers to the value calculated by the following method. The contact angle of the pressure-sensitive adhesive layer with water and the contact angle of the pressure-sensitive adhesive layer with diiodomethane are measured respectively. The obtained measured values and the surface free energy values (literature values) of the liquid for contact angle measurement (water or diiodomethane) were substituted into the following equation (I) derived from Young's equation and extended Fowkes' equation. The two equations obtained from the contact angle with water and the contact angle with diiodomethane were solved as a linear system of equations to calculate the surface free energy value. The surface free energy γS of the solid is γS d and γS v sum.

[0041] (1+cosθ)γ L =2√(γS d γL d )+2√(γ Sv γ L v ) ···(I)

[0042] The symbols in this equation are as follows.

[0043] θ: contact angle

[0044] γ L :Surface free energy of liquid for contact angle measurement

[0045] γ L d :γ L The dispersion force component in

[0046] γ L v :γ L The polar force component in

[0047] γS d : The dispersion force component in the surface free energy of a solid

[0048] γS v : The polar force component in the surface free energy of a solid

[0049] The tack value T of the pressure-sensitive adhesive layer measured by the probe tack method A It is preferably 150 gf to 900 gf, more preferably 200 gf to 850 gf, and still more preferably 250 gf to 850 gf. When the tack value T of the pressure-sensitive adhesive layer is A When the pressure-sensitive adhesive layer falls within the above-mentioned range, it can satisfactorily adhere closely to the semiconductor wafer serving as an adherend. The tack value T of the pressure-sensitive adhesive layer measured by the probe tack method is A It can be measured by the above-mentioned method.

[0050] The integrated value I of the pressure-sensitive adhesive layer measured by the probe tack method A It is preferably 5 gf·second to 50 gf·second, more preferably 5 gf·second to 45 gf·second. When the integral value I of the pressure-sensitive adhesive layer measured by the probe tack method is A When the pressure-sensitive adhesive layer falls within the above-mentioned range, the deformation energy of the pressure-sensitive adhesive layer may increase. A It can be measured by the above-mentioned method.

[0051] Viscosity value T A (gf) and integral value I A (gf·second) quotient Y(I A / T A) can be set to any appropriate value to satisfy formula (1). Quotient Y is preferably 0.01 to 0.08, more preferably 0.02 to 0.07, and even more preferably 0.03 to 0.06. When quotient Y falls within the above-mentioned scope, it is possible to obtain excellent adhesion and concavo-convex embedding properties with adherend surface, and a pressure-sensitive adhesive layer having reduced paste residue on the semiconductor wafer used as adherend.

[0052] Any suitable pressure-sensitive adhesive can be used as the active energy ray-curable pressure-sensitive adhesive. For example, a pressure-sensitive adhesive obtained by adding an ultraviolet-curable monomer and / or oligomer to any suitable pressure-sensitive adhesive, such as an acrylic pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, or a polyvinyl ether pressure-sensitive adhesive, can be used. Alternatively, a pressure-sensitive adhesive using a polymer having a polymerizable carbon-carbon double bond introduced into its side chain and / or its terminal as a base polymer can be used. Of these, a pressure-sensitive adhesive using a polymer having a polymerizable carbon-carbon double bond introduced into its side chain and / or its terminal as a base polymer is preferably used.

[0053] When using: when using a pressure-sensitive adhesive having a polymer having a polymerizable carbon-carbon double bond introduced into its side chain and / or its end, a polymer having a polymerizable carbon-carbon double bond introduced into its side chain and / or its end and having pressure-sensitive adhesiveness is used as a base polymer. Examples of such polymers include polymers obtained by introducing polymerizable carbon-carbon double bonds into, for example, the following resins: such as acrylic resins, vinyl alkyl ether resins, silicone resins, polyester resins, polyamide resins, polyurethane resins or styrene-diene block copolymers. Among them, it is preferred to use an acrylic resin obtained by introducing polymerizable carbon-carbon double bonds into acrylic resins. When using acrylic resins, it is possible to obtain a pressure-sensitive adhesive tape having an excellent balance between the storage elastic modulus and the tensile elastic modulus of the pressure-sensitive adhesive layer, and pressure-sensitive adhesive strength and releasability. In addition, the contamination of semiconductor wafers by the components from the pressure-sensitive adhesive can be reduced.

[0054] C-1. Base polymer

[0055] Any suitable polymer can be used as the base polymer. The base polymer can be obtained by polymerizing any suitable monomer composition. As mentioned above, it is preferred to use a (meth)acrylic acid polymer as the base polymer. The term "(meth)acrylic acid" as used in this specification refers to "acrylic acid" and / or "methacrylic acid."

[0056] The monomer composition for the polymerization of the base polymer can contain any appropriate monomer. As a monomer component, the monomer composition preferably contains a (meth) acrylic acid monomer having a side chain with more than 8 carbon atoms. Any appropriate monomer can be used as the (meth) acrylic acid monomer having a side chain with more than 8 carbon atoms. Examples thereof include: 2-ethylhexyl acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, and dodecyl (meth) acrylate. Each (meth) acrylic acid monomer having a side chain with more than 8 carbon atoms can be used alone or in combination.

[0057] The content ratio of (meth) acrylic acid monomer with the side chain having more than 8 carbon atoms in monomer composition can be set to any appropriate value.Relative to the whole monomer components of 100 mol %, the content ratio of (meth) acrylic acid monomer with the side chain having more than 8 carbon atoms is preferably more than 60 mol %, more preferably more than 70 mol %, even more preferably more than 80 mol %.The content ratio of (meth) acrylic acid monomer with the side chain having more than 8 carbon atoms is, for example, less than 90 mol %.When the content ratio of (meth) acrylic acid monomer with the side chain having more than 8 carbon atoms falls into the above-mentioned scope, surface energy X can be adjusted to appropriate value, therefore it is possible to provide concavo-convex embedding excellent and suppress the pressure-sensitive adhesive tape for semiconductor wafer processing that causes paste residue on the surface of semiconductor wafer.

[0058] The monomer composition may contain any suitable monomer other than the (meth) acrylic monomer having a side chain with 8 or more carbon atoms. Examples of the other monomers include: highly polar monomers and monomers having a side chain with 2 or less carbon atoms. Any suitable monomer may be used as the monomer having a side chain with 2 or less carbon atoms. Examples include methyl (meth)acrylate and ethyl (meth)acrylate. Monomers each having a side chain with 2 or less carbon atoms may be used alone or in combination.

[0059] Any suitable monomer can be used as the high polarity monomer. Examples thereof include hydroxyl-containing monomers, carboxyl-containing monomers and nitrogen-containing monomers. The high polarity monomer can have more than two polar groups (e.g., hydroxyl and nitrogen-containing groups). The high polarity monomer is preferably a high polarity monomer having a side chain with a carbon number of 4 or less, more preferably a hydroxyl-containing monomer having a side chain with a carbon number of 4 or less. The high polarity monomer can be used alone or in combination.

[0060] Any suitable monomer can be used as the hydroxyl group-containing monomer. Specific examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and N-(2-hydroxyethyl)acrylamide. The hydroxyl group-containing monomer can be used alone or in combination.

[0061] Any suitable monomer can be used as the carboxyl group-containing monomer. Specific examples thereof include (meth) acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The carboxyl group-containing monomer can be used alone or in combination.

[0062] Any suitable monomer can be used as the nitrogen-containing monomer. Specific examples thereof include N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyl The nitrogen-containing monomers may be used alone or in combination.

[0063] In monomer composition, the content ratio (total of these content ratios) of at least one selected from the group consisting of the monomer of high polarity monomer and the side chain with carbon number below 2 can be set to any appropriate value.Relative to the whole monomer components of 100 mol %, in monomer composition, the content ratio of at least one selected from the group consisting of the monomer of high polarity monomer and the side chain with carbon number below 2 is preferably below 39 mol %, more preferably below 30 mol %, even more preferably below 20 mol %.When the content ratio (total of content ratio) of at least one selected from the group consisting of the monomer of high polarity monomer and the side chain with carbon number below 2 falls into the above-mentioned scope of mentioning, surface energy X can be adjusted to appropriate value, therefore it is possible to provide concavo-convex embedding excellence and suppress the pressure-sensitive adhesive tape for semiconductor wafer processing that causes paste residue on the surface of semiconductor wafer.

[0064] In at least one embodiment of the present invention, preferably hydroxyl-containing monomer is used as high polar monomer.When using hydroxyl-containing monomer, by further making hydroxyl-containing monomer react with the compound with isocyanate group as described later, it is possible to obtain the (methyl) acrylic polymer having polymerizable carbon-carbon double bond introduced in its side chain and / or its terminal.Relative to the total monomer components of 100 mol %, the content ratio of hydroxyl-containing monomer is preferably 39 mol % or less, more preferably 10 mol % to 39 mol %.When the content ratio of hydroxyl-containing monomer falls into the above-mentioned scope, after active energy ray irradiation, when peeling off semiconductor wafer processing pressure-sensitive adhesive tape, it is possible to further suppress the glue residue on the semiconductor wafer surface used as adherend.

[0065] The monomer composition may further contain any suitable other monomers. Examples of other monomers include: anhydride monomers such as maleic anhydride and itaconic anhydride; and functional group-containing monomers including sulfonic acid group-containing monomers and phosphoric acid group-containing monomers. For the sulfonic acid group-containing monomers, for example, styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; for the phosphoric acid group-containing monomers, for example, 2-hydroxyethylacryloyl phosphate.

[0066] As mentioned above, a polymer having a polymerizable carbon-carbon double bond introduced into its side chain and / or its terminal can be used as a base polymer. A polymer having a polymerizable carbon-carbon double bond introduced into its side chain and / or its terminal can be obtained by any appropriate method. The polymer can be obtained by, for example, reacting a resin obtained by any appropriate polymerization method with a compound having a polymerizable carbon-carbon double bond (e.g., a condensation reaction or an addition reaction). Specifically, when an acrylic resin is used, a (meth) acrylic polymer having a polymerizable carbon-carbon double bond introduced therein can be obtained by, in any appropriate solvent, polymerizing a (meth) acrylic polymer (copolymer) having a constituent unit derived from a monomer having any appropriate functional group, and then reacting the functional group of the (meth) acrylic polymer with a compound having a polymerizable carbon-carbon double bond capable of reacting with the functional group. The amount of the compound having a polymerizable carbon-carbon double bond reacted is preferably 4 to 30 parts by weight, more preferably 4 to 20 parts by weight, relative to 100 parts by weight of the above-mentioned polymer. Any appropriate solvent can be used as the solvent. Examples thereof include various organic solvents such as ethyl acetate, methyl ethyl ketone, and toluene.

[0067] When reacting a (meth)acrylic polymer with a compound having a polymerizable carbon-carbon double bond as described above, the resin and the compound having a polymerizable carbon-carbon double bond preferably have functional groups that react with each other. Examples of functional group combinations include carboxyl / epoxy, carboxyl / aziridine, and hydroxyl / isocyanate. Of these functional group combinations, a hydroxyl and isocyanate combination is preferred from the perspective of ease of reaction tracking.

[0068] Examples of the compound having a polymerizable carbon-carbon double bond include 2-isocyanatoethyl methacrylate, methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate (2-isocyanatoethyl methacrylate), and m-isopropenyl-α,α-dimethylbenzyl isocyanate.

[0069] The weight-average molecular weight of the (meth)acrylic polymer is preferably 100,000 or greater, more preferably 150,000 or greater, even more preferably 200,000 or greater, and particularly preferably 250,000 to 1,000,000. When the weight-average molecular weight falls within this range, the bleed-out of low-molecular-weight components can be prevented, thereby providing a low-contamination pressure-sensitive adhesive tape for semiconductor wafer processing. The weight-average molecular weight can be determined by gel permeation chromatography (solvent: tetrahydrofuran, polystyrene conversion).

[0070] The gel fraction of the (meth)acrylic polymer is preferably 75% or greater, more preferably 80% or greater, and even more preferably 82% or greater. The gel fraction of the (meth)acrylic polymer is preferably 90% or less. When the gel fraction falls within the above-mentioned range, a pressure-sensitive adhesive tape for semiconductor wafer processing can be provided that has excellent uneven embeddability and suppresses the occurrence of adhesive residue on the surface of the semiconductor wafer.

[0071] (Meth) acrylic polymers can be obtained by polymerizing the above-mentioned monomer composition by any appropriate method. Examples thereof include solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization. The reaction temperature and reaction time can be set to any appropriate value based on the weight average molecular weight and gel fraction of the obtained (meth) acrylic polymer and the type of monomers used. In addition, the weight average molecular weight and / or gel fraction of the obtained (meth) acrylic polymer can be adjusted to any appropriate value by adjusting, for example, reaction conditions such as reaction temperature and reaction time and / or the solid content concentration of the monomer composition used.

[0072] C-2. Photopolymerization initiator

[0073] The active energy ray-curable pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer preferably further contains a photopolymerization initiator. Any appropriate initiator can be used as the photopolymerization initiator. Examples of photopolymerization initiators include: acylphosphine oxide-based photoinitiators such as ethyl 2,4,6-trimethylbenzoylphenylphosphinate and (2,4,6-trimethylbenzoyl)-phenylphosphine oxide; α-ketol compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)methanone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone and 1-hydroxycyclohexylphenyl ketone; acetophenone-based Compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one; benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether and anisole methyl ether; ketal compounds such as benzil dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenyl- 1,2-Propanedione-2-(O-ethoxycarbonyl)oxime; benzophenone compounds such as benzophenone, benzoylbenzoic acid and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone and 2,4-diisopropylthioxanthone; camphorquinone; haloketones; and acylphosphonates and α-hydroxyacetophenones such as 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl-2-methylpropane-1-one. Among them, 2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl-2-methylpropane-1-one can be preferably used. The photopolymerization initiator can be used alone or in combination.

[0074] Commercially available products can also be used as photopolymerization initiators. Examples thereof include products commercially available under the trade names Omnirad 127D, Omnirad 651, Omnirad 369E, and Omnirad 819 from IGM Resins BV.

[0075] The photopolymerization initiator is used in any appropriate amount. The content of the photopolymerization initiator is preferably 0.5 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, relative to 100 parts by weight of the base polymer. When the content of the photopolymerization initiator is less than 0.5 parts by weight, the active energy ray-curable pressure-sensitive adhesive may not be sufficiently cured upon ultraviolet irradiation. When the content of the photopolymerization initiator exceeds 10 parts by weight, the storage stability of the pressure-sensitive adhesive may be reduced.

[0076] C-3. Additives

[0077] As required, the pressure-sensitive adhesive may contain any appropriate additive. Examples of additives include cross-linking agents, catalysts (e.g., platinum catalysts), tackifiers, plasticizers, pigments, dyes, fillers, anti-aging agents, conductive materials, ultraviolet light absorbers, light stabilizers, release regulators, softeners, surfactants, flame retardants, and solvents.

[0078] In at least one embodiment of the present invention, the pressure-sensitive adhesive further comprises a cross-linking agent. Examples of cross-linking agents include isocyanate cross-linking agents, epoxy cross-linking agents, aziridine cross-linking agents, and chelate cross-linking agents. Relative to 100 parts by weight of the base polymer in the pressure-sensitive adhesive, the content ratio of the cross-linking agent is preferably 0.01 to 10 parts by weight, more preferably 0.02 to 5 parts by weight, and even more preferably 0.025 to 0.5 parts by weight. The flexibility of the pressure-sensitive adhesive layer can be controlled by the content ratio of the cross-linking agent. When the content of the cross-linking agent is less than 0.01 parts by weight, the pressure-sensitive adhesive becomes a sol-like state, and therefore a pressure-sensitive adhesive layer may not be formed. When the content of the cross-linking agent is greater than 10 parts by weight, the adhesion of the semiconductor wafer may be reduced, and therefore the semiconductor wafer may not be fully protected.

[0079] In at least one embodiment of the present invention, an isocyanate crosslinking agent is preferably used. Isocyanate crosslinking agents are preferred because they can react with a variety of functional groups. Particularly preferred are crosslinking agents having three or more isocyanate groups. When an isocyanate crosslinking agent is used as the crosslinking agent and the content ratio of the crosslinking agent falls within the above-mentioned range, a pressure-sensitive adhesive layer can be formed that has excellent removability even after heating and significantly reduces adhesive residue.

[0080] The thickness of the pressure-sensitive adhesive layer can be set to any appropriate value. The thickness of the pressure-sensitive adhesive layer is preferably 1 μm to 50 μm, more preferably 2 μm to 40 μm, and even more preferably 4 μm to 30 μm. When the thickness of the pressure-sensitive adhesive layer falls within the above-mentioned range, sufficient pressure-sensitive adhesive strength can be exhibited to the semiconductor wafer.

[0081] The pressure-sensitive adhesive layer may have any appropriate pressure-sensitive adhesive strength. The pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer to the silicon wafer before ultraviolet irradiation is preferably 0.50 N / 20 mm to 30 N / 20 mm, more preferably 2 N / 20 mm to 25 N / 20 mm, and even more preferably 5 N / 20 mm to 25 N / 20 mm. The pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer used in this specification refers to the value measured as follows: the pressure-sensitive adhesive tape for semiconductor wafer processing is cut into a size of 20 mm wide × 80 mm long; the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape for semiconductor wafer processing is pressed onto the mirror surface of the silicon mirror wafer by reciprocating a 2 kg roller once at 23°C; the resultant is allowed to stand at 23°C for 30 minutes; and then measured by a 180° peel test under conditions of a tensile speed of 300 mm / min at 23°C and 50% RH.

[0082] The pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer to the silicon wafer after ultraviolet irradiation is preferably 0.001N / 20mm to 1.000N / 20mm, more preferably 0.005N / 20mm to 0.850N / 20mm, and even more preferably 0.03N / 20mm to 0.40N / 20mm. The pressure-sensitive adhesive strength after ultraviolet irradiation used in this specification refers to a value measured as follows: the pressure-sensitive adhesive tape for semiconductor wafer processing is cut into a size of 20mm wide × 80mm long, and the pressure-sensitive adhesive layer is pressed onto the mirror surface of the silicon mirror wafer by reciprocating a 2 kg roller once in an atmosphere of 23°C; the resultant is allowed to stand at 23°C for 30 minutes; and then the pressure-sensitive adhesive layer is irradiated with ultraviolet rays (UV) from the substrate side of the pressure-sensitive adhesive tape for semiconductor wafer processing so that the cumulative light amount reaches 1000mJ / cm 2 (in terms of 365 nm); and then measured by performing a 180° peel test under the conditions of a tensile speed of 300 mm / min in an atmosphere of 23° C. and 50% RH.

[0083] D. Middle layer

[0084] In at least one embodiment of the present invention, the pressure-sensitive adhesive tape for semiconductor wafer processing preferably further comprises an intermediate layer. If the pressure-sensitive adhesive tape for semiconductor wafer processing further comprises an intermediate layer, the tape can further improve its ability to fit into the uneven surface of the adherend.

[0085] The intermediate layer can be formed from any suitable material. The intermediate layer can be formed from any suitable resin such as an acrylic resin, a polyethylene resin, an ethylene-vinyl alcohol copolymer, an ethylene-vinyl acetate resin, or an ethylene-methyl methacrylate resin, or can be formed from a pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive. Acrylic pressure-sensitive adhesives are preferably used. Acrylic pressure-sensitive adhesives generally contain an acrylic base polymer.

[0086] In at least one embodiment of the present invention, the intermediate layer contains a photopolymerization initiator and does not contain an ultraviolet curable component. That is, although the layer contains a photopolymerization initiator, the intermediate layer itself will not be cured by ultraviolet irradiation. Therefore, the intermediate layer can maintain its flexibility before and after ultraviolet irradiation. In addition, when the intermediate layer contains a photopolymerization initiator, it is possible to suppress the photopolymerization initiator in the pressure-sensitive adhesive layer from migrating to the intermediate layer. As a result, it is possible to suppress the content of the photopolymerization initiator in the pressure-sensitive adhesive layer from decreasing over time. Therefore, the pressure-sensitive adhesive tape for semiconductor wafer processing can show excellent light peelability after ultraviolet irradiation. The ultraviolet curable component used in this specification refers to a component that can be cross-linked by ultraviolet irradiation and shrink by curing. A specific example of such a component is the above-mentioned polymer having an unsaturated carbon double bond in its side chain or at its end.

[0087] The photopolymerization initiator in the composition for forming the intermediate layer (the intermediate layer ultimately formed) may be the same as or different from the photopolymerization initiator in the pressure-sensitive adhesive layer. Preferably, the intermediate layer and the pressure-sensitive adhesive layer contain the same photopolymerization initiator. When the intermediate layer and the pressure-sensitive adhesive layer contain the same photopolymerization initiator, the photopolymerization initiator can be further inhibited from moving from the pressure-sensitive adhesive layer to the intermediate layer. The photopolymerization initiator can use the examples mentioned in the above-mentioned C-2 section as a photopolymerization initiator. The photopolymerization initiator can be used alone or in combination. Relative to 100 parts by weight of the polymer constituent components in the composition for forming the intermediate layer, the content of the photopolymerization initiator in the intermediate layer is preferably 0.1 parts by weight to 10 parts by weight, more preferably 0.5 parts by weight to 8 parts by weight. When the content of the photopolymerization initiator in the intermediate layer falls within the above-mentioned range, a pressure-sensitive adhesive tape for semiconductor wafer processing with excellent light peelability after ultraviolet irradiation can be obtained. In at least one embodiment of the present invention, the amount of the photopolymerization initiator is equal to the amount in the composition for forming the pressure-sensitive adhesive layer.

[0088] In at least one embodiment of the present invention, the intermediate layer forming composition further contains a crosslinking agent. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, Azoline-based crosslinking agent, an aziridine-based crosslinking agent, a melamine-based crosslinking agent, a peroxide-based crosslinking agent, a urea-based crosslinking agent, a metal alkoxide-based crosslinking agent, a metal chelate-based crosslinking agent, a metal salt-based crosslinking agent, a carbodiimide-based crosslinking agent, and an amine-based crosslinking agent. When the intermediate layer-forming composition contains a crosslinking agent, the content of the crosslinking agent is preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight, relative to 100 parts by weight of the polymer components in the intermediate layer-forming composition.

[0089] The intermediate layer-forming composition may further contain any appropriate additives as needed. Examples of additives include active energy ray polymerization accelerators, free radical scavengers, tackifiers, plasticizers (e.g., trimellitate plasticizers or pyromellitate plasticizers), pigments, dyes, fillers, antioxidants, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, release modifiers, softeners, surfactants, flame retardants, and antioxidants.

[0090] The thickness of the intermediate layer can be set to any appropriate value. The thickness of the intermediate layer is preferably 10 μm to 300 μm, more preferably 30 μm to 200 μm, even more preferably 50 μm to 150 μm, and particularly preferably 90 μm to 150 μm. When the thickness of the intermediate layer falls within the above-mentioned range, a pressure-sensitive adhesive tape for semiconductor wafer processing can be obtained in which a concavo-convex surface can be satisfactorily embedded.

[0091] E. Method for manufacturing pressure-sensitive adhesive tape for semiconductor wafer processing

[0092] Semiconductor wafer processing pressure-sensitive adhesive tape can be manufactured by any appropriate method.In at least one embodiment of the present invention, semiconductor wafer processing pressure-sensitive adhesive tape can be manufactured by forming any appropriate intermediate layer on substrate, then forming pressure-sensitive adhesive layer on substrate or any appropriate intermediate layer.Pressure-sensitive adhesive layer and intermediate layer can be formed by respectively forming pressure-sensitive adhesive layer with composition and intermediate layer with composition being coated to substrate or intermediate layer, or can separately form layer and then transfer layer by forming layer on any appropriate release liner.As the method for coating, separately can adopt multiple methods such as rod coater coating, air knife coating, gravure coating, gravure reverse coating, reverse roller coating, lip coating, die coating, dip coating, offset printing, flexographic printing and screen printing.In addition, can adopt for example to be included in the method that pressure-sensitive adhesive layer or intermediate layer are formed separately on release liner, then gained is pasted to substrate.

[0093] F. Applications of Pressure-Sensitive Adhesive Tapes for Semiconductor Wafer Processing

[0094] The pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention can be suitably used in the semiconductor element manufacturing process. The pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention can be suitably used as a back grinding tape. The back grinding tape is required to have such light peeling properties that it can properly hold the silicon wafer during back grinding and can be peeled off without damaging the ground wafer and without causing adhesive residue when peeling it off. The pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention is excellent in concave-convex embedding properties and can suppress the occurrence of adhesive residue on the surface of the semiconductor wafer. Therefore, the pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention can be suitably used as a back grinding tape.

[0095] Example

[0096] The present invention will be described in detail below by way of examples, but the present invention is not limited to these examples. In addition, in the examples, unless otherwise specified, "parts" and "%" are by weight.

[0097] [Example 1]

[0098] 1. Preparation of the intermediate layer-forming composition

[0099] 50 parts by weight of butyl acrylate (BA), 50 parts by weight of ethyl acrylate (EA), 5 parts by weight of acrylic acid (AA), and 0.1 parts by weight of azobisisobutyronitrile (AIBN) were polymerized in toluene under a nitrogen atmosphere at 60° C. for 6 hours to provide a polymer solution containing a (meth)acrylic polymer having a weight average molecular weight of 650,000.

[0100] 1 part by weight of a polyisocyanate compound (manufactured by Mitsui Chemicals, trade name: "TAKENATE D-101A") and 1 part by weight of a photopolymerization initiator (manufactured by IGM Resins BV, trade name: Omnirad 127D) were mixed with 100 parts by weight of the solid content of the resulting polymer solution. This yielded a toluene-containing composition for forming an intermediate layer (solids concentration: 23%).

[0101] 2. Preparation of Pressure-Sensitive Adhesive Composition

[0102] 89% by weight of 2-ethylhexyl acrylate (2EHA) and 11% by weight of 2-hydroxyethyl acrylate (HEA) (manufactured by Toagosei Co., Ltd., trade name: ACRYCS (registered trademark) HEA) were each used as a monomer component. A polymerization initiator (manufactured by Tokyo Chemical Industry Co., Ltd., trade name: 2,2'-azobis(isobutyronitrile) (AIBN)) was mixed with a solvent (ethyl acetate) at a concentration of 0.15% by weight relative to the total weight of the monomer components to prepare a monomer composition (solid concentration: 32%). The obtained monomer composition was charged into a polymerization experimental apparatus obtained by installing a detachable lid, a separatory funnel, a thermometer, a nitrogen inlet tube, a Liebig condenser, a vacuum seal, a stirring rod, and a stirring blade on a 1-liter round-bottom separable flask. While stirring the composition, the apparatus was purged with nitrogen at room temperature for 1 hour. Thereafter, the composition was maintained at 67° C. for 5 hours while being stirred under a nitrogen stream to perform solution polymerization, and then the temperature was increased to 76° C. and maintained at 76° C. for 2 hours to provide a polymer solution.

[0103] The resulting polymer solution was cooled to 35°C or lower and stirred for at least 15 minutes while oxygen was introduced into the flask. 2-Methacryloyloxyethyl isocyanate (hereinafter referred to as "MOI") (manufactured by Resonac Corporation, trade name: "Karenz MOI") was added so that its molar amount relative to the amount of HEA added was 80 mol%. Furthermore, 0.03 wt% of dibutyltin dilaurate was added as a reaction catalyst relative to the amount of MOI added. The contents were then subjected to an addition reaction treatment (urethanization reaction) at 50°C in an air stream for 12 hours to provide an ultraviolet (UV)-curable acrylic copolymer.

[0104] Next, 2 parts by weight of a photopolymerization initiator (manufactured by IGM Resins BV under the trade name: “Omnirad 127D”), 1 part by weight of a polyisocyanate compound (manufactured by Mitsui Chemicals, Inc. under the trade name: “TAKENATE D-101A”), and 0.01 parts by weight of an antioxidant (manufactured by BASF Japan under the trade name: “Irganox 1010”) were added to 100 parts by weight of the ultraviolet-curable acrylic copolymer to provide a pressure-sensitive adhesive composition.

[0105] 3. Manufacturing of adhesive tape

[0106] The composition for forming the intermediate layer obtained in Part 1 was applied to the surface of a 38 μm thick polyester release liner (manufactured by Mitsubishi Chemical Corporation, trade name: "Diafoil (registered trademark)") that had been treated with silicone, and heated at 120°C for 120 seconds to remove the solvent. Thus, an intermediate layer 1 with a thickness of 50 μm was formed. Next, a 50 μm thick PET film (manufactured by Toray Industries, Ltd., trade name: "LUMIRROR (registered trademark)") serving as a substrate was attached to the surface of the intermediate layer 1 thus formed. Separately, the composition for forming the intermediate layer was applied to the surface of a 38 μm thick polyester release liner that had been treated with silicone, and heated at 120°C for 120 seconds to remove the solvent. Thus, an intermediate layer 2 with a thickness of 50 μm was formed. The release liner was peeled off from the intermediate layer 1, and the intermediate layer 2 was attached to the surface of the intermediate layer 1 from which the release liner had been peeled off. Thus, a laminate of the substrate and the intermediate layers (intermediate layer 1 and intermediate layer 2) was obtained.

[0107] Separately, the pressure-sensitive adhesive composition obtained in Part 2 was applied to the surface of a 75 μm-thick silicone-treated polyester release liner and heated at 120° C. for 120 seconds to remove the solvent. Thus, a 20 μm-thick pressure-sensitive adhesive layer was formed.

[0108] Next, the release liner was peeled off from the intermediate layer 2, and a pressure-sensitive adhesive layer was attached to the surface of the intermediate layer from which the release liner was peeled off to transfer the pressure-sensitive adhesive layer, and the resultant was kept at 50° C. for 72 hours. Thus, a pressure-sensitive adhesive tape comprising a substrate, intermediate layers (intermediate layer 1 and intermediate layer 2), and a pressure-sensitive adhesive layer in this order was obtained.

[0109] [Examples 2 to 6]

[0110] Each pressure-sensitive adhesive tape was obtained in the same manner as in Example 1, except that the composition of each monomer, the polymerization conditions of the monomer, and the composition of the pressure-sensitive adhesive composition were changed as shown in Table 1.

[0111] (Comparative Examples 1 to 3)

[0112] Each pressure-sensitive adhesive tape was obtained in the same manner as in Example 1, except that the composition of each monomer, the polymerization conditions of the monomer, and the composition of the pressure-sensitive adhesive composition were changed as shown in Table 1.

[0113]

[0114] <Evaluation>

[0115] The following evaluations were performed using the pressure-sensitive adhesive tapes obtained in Examples and Comparative Examples. The results are shown in Table 1.

[0116] 1. Measurement of weight average molecular weight Mw

[0117] Approximately 0.2 g of a sample was obtained from the resulting UV-curable acrylic copolymer. The collected sample was dissolved in tetrahydrofuran (THF) to prepare a THF solution having a solids concentration of 0.2% by weight, and the solution was allowed to stand overnight. The THF solution, after standing overnight, was filtered through a membrane filter with a pore size of 0.45 μm, and the resulting filtrate was used as the measurement sample.

[0118] The weight average molecular weight Mw of the measurement sample is measured under the following measurement conditions by using HLC-8220GPC manufactured by Tosoh Corporation as an analyzer.

[0119] Columns: One TSKgel guardcolumn SuperHZ-L manufactured by Tosoh Corporation (hereinafter referred to as the "first column") and two TSKgel SuperHZM-M manufactured by Tosoh Corporation (hereinafter referred to as the "second column")

[0120] Each column is arranged on the analyzer in such a manner that two second columns are connected in series on the downstream side of a first column so that the eluent flows in from the first column side.

[0121] Column temperature: 40°C

[0122] Eluent: Tetrahydrofuran (THF)

[0123] Flow rate: Sample pump flow rate: 0.3mL / min, reference pump flow rate: 1.0mL / min

[0124] Injection volume: 100 μL

[0125] Detector: Differential refractive index detector (RI)

[0126] Based on the measurement results of the measurement samples, in order to obtain a molecular weight distribution curve (differential molecular weight distribution curve), each standard polystyrene manufactured by Tosoh Corporation was weighed so as to have a mixed weight shown in Table 2 below, and each weighed standard polystyrene was dissolved in 100 mL of THF to provide a standard polystyrene solution STD1 and a standard polystyrene solution STD2. GPC measurement was performed on each of these solutions in the same manner.

[0127]

[0128] 2. Gel Fraction

[0129] About 0.2 g of sample was collected from the pressure-sensitive adhesive composition before curing by ultraviolet irradiation. Next, the sample was wrapped in a mesh sheet (manufactured by Nitto Denko Corporation, trade name: NTF1122, thickness: 80 μm, average pore size: 0.2 μm) and then immersed in about 30 mL of ethyl acetate at room temperature for 1 week. Thereafter, the mesh sheet was taken out from ethyl acetate and the ethyl acetate insolubles contained in the mesh sheet were recovered. The recovered ethyl acetate insolubles were dried at normal pressure and 130 ° C for about 2 hours. The ethyl acetate insolubles were weighed. The gel fraction was calculated by calculating the weight ratio of the gel component by the following equation.

[0130] Gel fraction (%) = [(weight of ethyl acetate insoluble matter (g)) / (weight of sample obtained (g))] × 100

[0131] 3. Storage elastic modulus

[0132] The pressure-sensitive adhesive compositions used in Examples and Comparative Examples were laminated to a thickness of about 0.8 mm to about 1.0 mm without bubbles to prepare samples. The storage elastic modulus G' at 25° C. was measured under the following conditions using a viscoelasticity measuring device (manufactured by TA Instruments, trade name: "ARES-G2").

[0133] Mode: Torsion mode

[0134] ·Plate diameter: 7.9mmΦ

[0135] Strain: 0.1% (-50℃)

[0136] Frequency: 1Hz

[0137] Measuring range: -50℃ to 150℃

[0138] 4. Contact Angle and Surface Free Energy

[0139] The surface free energy of the pressure-sensitive adhesive layer of each pressure-sensitive adhesive tape obtained in the examples and comparative examples was measured by the following method. Water or diiodomethane was dropped onto the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape, and the contact angle was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., trade name: CA-X). The measured value and the surface free energy value of the liquid (water or diiodomethane) for contact angle measurement (known from the literature) were substituted into the following equation (I) derived from Young's equation and extended Fowkes equation. The two equations obtained were solved as a linear equation system to calculate the surface free energy value. The surface free energy γS of a solid is γS d and γS v sum.

[0140] (1+cosθ)γ L=2√(γS d γL d )+2√(γ S v γ L v ) ···(I)

[0141] The symbols in this equation are as follows.

[0142] θ: contact angle

[0143] γ L :Surface free energy of liquid for contact angle measurement

[0144] γ L d :γ L The dispersion force component in

[0145] γ L v :γ L The polar force component in

[0146] γS d : The dispersion force component in the surface free energy of a solid

[0147] γS v : The polar force component in the surface free energy of a solid

[0148] 5. Peak and integral values

[0149] The tack test of the pressure-sensitive adhesive layer was conducted by a probe tack method under the following measuring conditions using a probe tack tester manufactured by Rhesca Co., Ltd. (trade name: “TAC-II”).

[0150] (Measurement conditions)

[0151] Probe diameter: 5mmΦ

[0152] Contact speed: 120mm / min

[0153] Load: 10gf

[0154] Contact time: 1 second

[0155] Peeling speed: 600mm / min

[0156] Specifically, the substrate surface of each pressure-sensitive adhesive tape and a glass slide were adhered to each other via double-sided tape (manufactured by Nitto Denko Corporation, trade name: "No. 5000NS"), thereby fixing the pressure-sensitive adhesive tape to the glass slide. Next, a probe with a probe diameter of 5 mm was pressed against the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape at a contact speed of 120 mm / min, applying a load of 10 gf so that the probe and the pressure-sensitive adhesive layer were in contact for 1 second. Next, the probe was lifted at a peeling speed of 600 mm / min, and the peak value (peak value [gf]) at the time of peeling was defined as the viscosity value T A (gf), the peak area (integrated [gf·second]) is defined as the integral value I A (gf·seconds). Each value is determined accordingly.

[0157] 6. Embeddability

[0158] Each pressure-sensitive adhesive tape obtained in the Examples and Comparative Examples was cut into 230 cm × 400 cm pieces. The cut pressure-sensitive adhesive tape was then attached to a wafer (8-inch, bump height: 75 μm, diameter: 90 μm, pitch: 200 μm) using a tape attaching device (manufactured by Nitto Seiki Co., Ltd., trade name: DR-3000III). This attachment was performed under the following conditions.

[0159] Roller pressure: 0.27MPa

[0160] Roller speed: 20 mm / s

[0161] Workbench temperature: room temperature (RT)

[0162] After the pasting, the pasting state of the pressure-sensitive adhesive tape and the wafer was observed using a laser microscope (magnification: 100 times).

[0163] In addition, with the pressure-sensitive adhesive tape facing up, an image of the pressure-sensitive adhesive tape and the wafer was taken from the pressure-sensitive adhesive tape side, and the image was binarized (8-bit grayscale, brightness: 0 to 255, threshold: 114) using image analysis software (Image J (free software)). Thereafter, five bumps were randomly selected from the wafer, and the number of points used to display one bump was counted. The image of the bump in the state where only the tape was not pasted had 220 points. The closer the number of points measured in the state where the wafer was pasted with the pressure-sensitive adhesive tape was to 220, the more satisfactory the embedding property was. When a pressure-sensitive adhesive tape was pasted on a semiconductor wafer with bumps, the number of points usually became about 820. The evaluation was performed as follows: the case where the average number of points of the five random bumps was 700 or less was evaluated as "◎" (very satisfactory); the case where the average number of points was 701 to 820 was evaluated as "○" (satisfactory); the case where the average number of points was greater than 820 was evaluated as "Δ" (room for improvement).

[0164] 7. Glue residue

[0165] The silicon wafer was ground under the following conditions to produce a wafer having an exposed active surface.

[0166] Wafer used: 8-inch silicon mirror wafer

[0167] Back grinder: DFG8560 (manufactured by DISCO)

[0168] Z1 wheel: Specifications: "GF01-SD360-VS-100", Size: "300×4W×4T"

[0169] Z2 wheel: Specifications: "BGT-270 IF-01-1-4 / 6-B-K09", Dimensions: "300×5T×3W"

[0170] Thickness after grinding: 500μm

[0171] Grinding water: pure water

[0172] Three sheets of pressure-sensitive adhesive tape (trade name: "BT-315") manufactured by Nitto Denko Corporation were stacked on the wafer to create a height difference. The tape was then applied across the height difference using a tape application device (manufactured by Nitto Seiki Co., Ltd., trade name: "DR-3000III"). The resultant was then heated at 60°C for 24 hours. After heating, an ultraviolet irradiation device (manufactured by Nitto Seiki Co., Ltd., trade name: "UM-810") was used to irradiate the wafer with a high-pressure mercury lamp at 1000 mJ / cm 2 Irradiation was performed from the substrate surface side. After irradiation, the tape was peeled off using a tensile tester at a peeling angle of 180° and a peeling speed of 300 mm / min, and the adhesive residue was visually observed using an optical microscope.

[0173] The conditions for pasting are as follows.

[0174] Pressure: 0.4MPa

[0175] Speed: 5mm / s

[0176] Workbench temperature: room temperature (RT)

[0177] Peripheral workbench height: 400μm

[0178] The evaluation was performed as follows: the case where almost no adhesive residue was observed on the wafer surface after peeling off the pressure-sensitive adhesive tape was evaluated as "◎" (very satisfactory); the case where linear adhesive residue was visible by observation using a microscope was evaluated as "○" (satisfactory); and the case where adhesive residue was observed even without using a microscope was evaluated as "Δ" (room for improvement).

[0179] Each pressure-sensitive adhesive tape of the examples of the present invention has excellent ability to fit into the unevenness of the surface of a semiconductor wafer having unevenness on its surface, and also has suppressed adhesive residue.

[0180] The pressure-sensitive adhesive tape for semiconductor wafer processing according to at least one embodiment of the present invention can be suitably used for semiconductor wafer processing. The pressure-sensitive adhesive tape for semiconductor wafer processing can be suitably used as, for example, a back grinding tape for semiconductor wafer processing.

[0181] According to at least one embodiment of the present invention, it is possible to provide a pressure-sensitive adhesive tape for semiconductor wafer processing that has excellent concavo-convex embeddability and suppresses adhesive residue from occurring on the surface of a semiconductor wafer.

Claims

1. A pressure-sensitive adhesive tape for semiconductor wafer processing, comprising: substrate; and a pressure-sensitive adhesive layer formed of an active energy ray-curable pressure-sensitive adhesive, The tack value T of the pressure-sensitive adhesive layer measured by the probe tack method is A (gf) and integral value I A (gf·second) quotient Y(I A / T A ) and the surface free energy X (mN / m) of the pressure-sensitive adhesive layer satisfy the relationship of formula (1): Y>0.01X-0.21(1).

2. The pressure-sensitive adhesive tape for semiconductor wafer processing according to claim 1, wherein the active energy ray-curable pressure-sensitive adhesive contains a (meth)acrylic polymer, and The (meth)acrylic polymer is a polymer obtained by polymerizing a monomer composition containing 60 mol % or more of a (meth)acrylic monomer having a side chain with 8 or more carbon atoms. 3 . The pressure-sensitive adhesive tape for semiconductor wafer processing according to claim 2 , wherein the monomer composition contains 39 mol % or less of at least one member selected from the group consisting of highly polar monomers and monomers having a side chain having 2 or less carbon atoms. 4 . The pressure-sensitive adhesive tape for semiconductor wafer processing according to claim 3 , wherein the highly polar monomer is a hydroxyl group-containing monomer having a side chain with 4 or less carbon atoms. 5 . The pressure-sensitive adhesive tape for semiconductor wafer processing according to claim 4 , wherein the monomer composition contains 10 mol % to 39 mol % of the hydroxyl group-containing monomer having a side chain with 4 or less carbon atoms. 6 . The pressure-sensitive adhesive tape for semiconductor wafer processing according to claim 1 , further comprising an intermediate layer. 7 . The pressure-sensitive adhesive tape for semiconductor wafer processing according to claim 1 , wherein the pressure-sensitive adhesive tape is a back grinding tape.

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