Adhesive tape for wafer grinding and wafer processing method

Abstract

To provide an adhesive tape for wafer grinding that has excellent followability to the unevenness of a wafer surface, and can perform grounding such that the thickness accuracy of a wafer after grinding is good, and can perform processing without damaging the wafer or a device in a thin film grinding process or a polishing process even when a pre-dicing method or a pre-stealth method is applied, and a wafer processing method.SOLUTION: An adhesive tape 1 for wafer grinding includes: a base resin film 2; an adhesive layer 3 formed on at least one side of the base resin film 2; and an intermediate layer 4 provided between the base resin film 2 and the adhesive layer 3, wherein a double-sided tape is attached to a surface opposite to the adhesive layer 3 of the adhesive tape 1 for wafer grinding and is fixed to a measurement stage, and a measurement terminal is pushed by 20 μm at a temperature of 50°C, and a loss tangent obtained by torsional shear measurement is 0.12 to 0.35.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an adhesive tape for wafer grinding and a method for processing a wafer, and more particularly to an adhesive tape for wafer grinding that can be applied to a thin film grinding process of a wafer and a method for processing a wafer using the adhesive tape for wafer grinding. [Background technology]

[0002] After the pattern is formed, the wafer is usually subjected to a process such as back grinding or etching to reduce its thickness. At this time, an adhesive tape for wafer grinding is applied to the patterned surface of the wafer in order to protect the pattern on the wafer surface. The adhesive tape for wafer grinding is generally formed by laminating an adhesive layer on a base resin film, and is used by applying the adhesive layer to the surface of the wafer.

[0003] In recent years, with the aim of shortening wiring length and miniaturizing devices, the practical application of packaged products in which LSI (Large Scale Integration) chips are arranged three-dimensionally is progressing. LSI chips are obtained by forming a thick insulating film on the surface of a semiconductor wafer, forming through holes in the insulating film, filling the through holes with wiring material such as copper to form through electrodes, and then dicing the result. In such wafers, because a thick insulating film is formed on the surface of the semiconductor wafer, the step of the wafer edge and the depth of the scribe lines that are formed in advance for dicing are large.

[0004] Furthermore, with the trend towards thinner packaging and smaller chip mounting areas, a mounting method called flip-chip mounting has been adopted. In flip-chip mounting, the chip surface and the substrate are electrically connected using ball-shaped or cylindrical bumps formed on the surface of the semiconductor wafer. Some of these bumps have a height (thickness) of over 100 μm.

[0005] As described above, when the adhesive tape for wafer grinding is applied to a wafer having a large surface unevenness due to the steps, scribe lines, bumps, etc. of the wafer edge, the adhesive tape for wafer grinding cannot sufficiently conform to the unevenness of the wafer surface, and the adhesive tape does not adhere sufficiently to the protruding parts. Then, the stress during grinding is concentrated on the protruding parts, causing grinding marks called dimples, or the wafer may be damaged during grinding.

[0006] Therefore, in order to allow the tape to adequately conform to the convex portions of the wafer surface, an adhesive tape for wafer grinding has been proposed in which a highly flexible thermoplastic resin layer is formed between the base film layer and the adhesive layer (see, for example, Patent Documents 1 and 2).

[0007] The elastic modulus is an index for conforming to the protrusions on the wafer surface, and is generally evaluated using a DYNAMIC ANALYZER RDA II or ARES (see, for example, Patent Documents 3 and 4).

[0008] However, with the recent progress in high-density mounting technology, there is a demand for thinner wafers, and in some cases, it is required to process the wafer to a thickness of 50 μm or less, for example, to 25 μm. One such processing method is a pre-dicing method in which a groove of a predetermined depth is formed on the wafer surface before back grinding of the wafer, and then back grinding is performed to separate chips (see, for example, Patent Document 5). In addition, there is a pre-stealth method in which a laser is irradiated inside the wafer before back grinding to form a modified region, and then back grinding is performed to separate chips (see, for example, Patent Document 6). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 3773358 [Patent Document 2] Patent No. 4054113 [Patent Document 3] Patent No. 6059499 [Patent Document 4] JP 2018-100422 A [Patent Document 5] Japanese Patent Application Publication No. 05-335411 [Patent Document 6] JP 2004-001076 A Summary of the Invention [Problem to be solved by the invention]

[0010] However, in the adhesive tape for wafer grinding described in Patent Documents 1 and 2, the flexible thermoplastic resin layer causes the wafer to vibrate during grinding, which may cause the wafer thickness accuracy after grinding to deteriorate. Furthermore, when the wafer is ground to a thickness of 25 μm using the first dicing method or the first stealth method, the adhesive tape for wafer grinding described in Patent Documents 1 and 2 has a flexible thermoplastic resin layer, so that the adhesive layer or thermoplastic resin layer may get into the kerf portion generated when the wafer is half-cut or the crack extended from the modified layer along the cutting line, and may be caught between the wafer and the grinding device when the wafer is ground, which may damage the wafer or the grinding device. In addition, when polishing is performed after grinding the back surface of the wafer, a pressure of more than 200 N / 12 inch is applied to the back surface of the wafer, and polishing heat of more than 60 ° C may be generated. If the thermoplastic resin layer or the adhesive layer is made of a thermoplastic resin, the adhesive layer is more likely to get caught between the wafer and the polishing device, which may increase the risk of damaging the wafer or the polishing device.

[0011] In addition, in order to improve the thickness accuracy of the wafer after grinding, it is desirable to form multiple layers, such as by providing a thermoplastic resin layer in addition to the adhesive layer, as described above. However, the elastic modulus evaluation methods described in Patent Documents 3 and 4 are only capable of measuring a single layer, making it difficult to measure multiple layers.

[0012] Therefore, an object of the present invention is to provide an adhesive tape for wafer grinding which has excellent conformability to irregularities on the wafer surface, can grind the wafer so as to obtain good thickness accuracy after grinding, and can be used for processing without damaging the wafer or equipment in the thin film grinding and polishing processes even when a first-dicing method or a first-stealth method is applied, and a wafer processing method in which this adhesive tape for wafer grinding is used to process a wafer. [Means for solving the problem]

[0013] As a result of intensive research conducted by the present inventors in order to achieve the above object, they discovered a method that enables measurement of the elastic modulus of a multi-layered adhesive tape for wafer grinding, and thus completed the present invention.

[0014] In order to solve the above problems, the adhesive tape for wafer grinding according to the present invention is an adhesive tape for wafer grinding having a base resin film, an adhesive layer formed on at least one side of the base resin film, and an intermediate layer provided between the base resin film and the adhesive layer, wherein a double-sided tape is attached to the side of the adhesive tape for wafer grinding opposite to the adhesive layer, the adhesive tape for wafer grinding is fixed to a measurement stage with the double-sided tape, and a measurement terminal is pressed 20 μm into the adhesive tape for wafer grinding at a temperature of 50° C., and the loss tangent obtained by torsional shear measurement is 0.12 to 0.35.

[0015] The adhesive tape for wafer grinding is preferably such that a double-sided tape is affixed to a surface of the adhesive tape for wafer grinding opposite to the adhesive layer, the adhesive tape for wafer grinding is fixed to a measurement stage with the double-sided tape, and a measurement terminal is pressed 20 μm into the adhesive tape for wafer grinding at a temperature of 50° C., and a storage modulus obtained by torsional shear measurement is 53 kPa to 159 kPa.

[0016] The above adhesive tape for wafer grinding is characterized in that the thickness of the intermediate layer is 20 to 150% of the thickness of the adhesive layer.

[0017] In addition, the above-mentioned adhesive tape for wafer grinding is preferably used in a process of dividing a wafer into chips by grinding the back surface of the wafer after cutting the wafer, or in a process of forming a modified region by irradiating a laser inside the wafer and then grinding the back surface of the wafer to divide the wafer into chips. Effect of the Invention

[0018] The adhesive tape for wafer grinding and the wafer processing method of the present invention have excellent conformability to the irregularities on the wafer surface, and can grind the wafer so that the thickness accuracy after grinding is good. Even when the first dicing method or first stealth method is applied, the wafer can be processed without damaging the wafer or the device in the thin film grinding process or polishing process. [Brief description of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view showing a schematic structure of an adhesive tape for wafer grinding according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing a schematic structure of a modified example of the adhesive tape for wafer grinding according to an embodiment of the present invention. [Diagram 3] 1A to 1C are cross-sectional views illustrating a back-grinding process using an adhesive tape for wafer grinding according to an embodiment of the present invention. [Figure 4] 1A to 1C are cross-sectional views illustrating a back-grinding process using an adhesive tape for wafer grinding according to an embodiment of the present invention. [Diagram 5] FIG. 2 is a cross-sectional view showing a schematic diagram of a singulation process after a back-grinding process using an adhesive tape for wafer grinding according to an embodiment of the present invention. [Figure 6] FIG. 2 is a cross-sectional view showing a schematic diagram of a singulation process after a back-grinding process using an adhesive tape for wafer grinding according to an embodiment of the present invention. [Figure 7] FIG. 2 is a cross-sectional view showing a schematic diagram of an expanding step after a back-grinding step using the adhesive tape for wafer grinding according to an embodiment of the present invention. [Figure 8]FIG. 2 is a cross-sectional view showing a pickup step after a back-grinding step using the adhesive tape for wafer grinding according to an embodiment of the present invention. BEST MODE FOR CARRYING OUT THEINVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view showing a schematic structure of an adhesive tape 1 for wafer grinding according to an embodiment of the present invention.

[0021] 1, the adhesive tape 1 for wafer grinding according to this embodiment has a base resin film 2, and an adhesive layer 3 is provided on at least one side of the base resin film 2. An intermediate layer 4 is provided between the base resin film 2 and the adhesive layer 3. If necessary, a release film (not shown) whose surface has been subjected to a release treatment may be laminated on the adhesive layer 3 so that the release-treated surface faces the adhesive layer 3.

[0022] (Base resin film 2) Known plastics, rubbers, etc. can be used as the base resin film 2 of the adhesive tape 1 for wafer grinding of the present invention. When a radiation-curable composition is used in the adhesive layer 3, it is preferable to select a base resin film 2 that has good transmittance to radiation of a wavelength at which the composition cures. Note that radiation here is a general term for light such as ultraviolet light, laser light, or ionizing radiation such as electron beams, and hereinafter these will be referred to collectively as radiation.

[0023] Examples of materials that can be selected for the base resin film 2 include homopolymers or copolymers of α-olefins such as polyethylene, polypropylene, ethylene-propylene copolymers, polybutene-1, poly-4-methylpentene-1, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, ethylene-methyl acrylate copolymers, ethylene-acrylic acid copolymers, ionomers, or mixtures thereof, engineering plastics such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, and polymethyl methacrylate, thermoplastic elastomers such as polyurethane, styrene-ethylene-butene or pentene copolymers, and polyamide-polyol copolymers, and mixtures thereof. Also, a multilayer of these may be used.

[0024] As a method for laminating the layers to form the base resin film 2, a known method such as lamination using a pressure sensitive adhesive, adhesive, co-extrusion, etc. can be applied. For example, as shown in Fig. 2, the base resin film 2 can be obtained by laminating one base resin film 21 made of the above-mentioned material and another base resin film 23 made of the above-mentioned material via an adhesive layer 22.

[0025] The surface of the base resin film 2 on which the intermediate layer 4 is provided may be appropriately subjected to treatment such as corona treatment or provision of a primer layer in order to improve adhesion to the intermediate layer 4. It is also preferable to texture or coat the surface of the base resin film 2 on which the intermediate layer 4 is not provided, which can provide effects such as prevention of blocking during storage of the adhesive tape 1 for wafer grinding of the present invention.

[0026] (Adhesive layer 3) As shown in FIG. 1, an adhesive tape 1 for wafer grinding according to this embodiment has an adhesive layer 3 formed on one surface side of a base resin film 2.

[0027] The adhesive composition constituting the adhesive layer 3 is not particularly limited as long as it can adequately maintain adhesion to the wafer 5 when the wafer 5 is ground and does not cause damage to the wafer 5 when the wafer grinding adhesive tape 1 is peeled off, but it is preferable to select one that has a low peel force at a low angle as described below. The main component polymer (adhesive base resin) is preferably a (meth)acrylic resin. By using a (meth)acrylic resin as the main component polymer, it becomes easier to control the adhesive force and the elastic modulus, etc.

[0028] From the viewpoint of peelability, it is preferable to use a radiation-curable adhesive as the adhesive composition constituting the adhesive layer 3. To cure by irradiation with radiation, a resin such as an adhesive base resin has an ethylenically unsaturated group (a non-aromatic carbon-carbon double bond), or a compound having an ethylenically unsaturated group is used in combination with the adhesive base resin. In the present invention, it is particularly preferable to use a resin such as an adhesive base resin having an ethylenically unsaturated group in its side chain from the viewpoint of peelability. In addition, it is preferable that the adhesive composition contains a photopolymerization initiator and a crosslinking agent, and it is preferable to contain a crosslinking agent to adjust the elastic modulus and adhesive strength of the adhesive layer 3.

[0029] When a so-called pressure-sensitive adhesive that does not harden upon irradiation with radiation is used as the adhesive composition constituting the adhesive layer 3, it is also possible to reduce the peeling force by applying heat, for example, at about 50° C. during peeling instead of irradiating with radiation. As such a pressure-sensitive adhesive, a copolymer containing a constituent unit derived from a (meth)acrylic acid alkyl ester monomer and a constituent unit derived from 2-hydroxypropyl acrylate, 2-hydroxylethyl (meth)acrylate and / or 2-hydroxybutyl acrylate, and containing the constituent unit derived from the (meth)acrylic acid alkyl ester monomer, crosslinked with an isocyanate compound, can be used.

[0030] [Resin having an ethylenically unsaturated group] Any resin having an ethylenically unsaturated group may be used, but a (meth)acrylic resin is preferred. The iodine value, which is an index of the amount of double bonds contained in the resin, is preferably 0.5 to 20. This iodine value is more preferably 0.8 to 10. When the iodine value is 0.5 or more, the adhesive strength after irradiation can be reduced, and when the iodine value is 20 or less, excessive radiation curing can be prevented. In addition, the resin having an ethylenically unsaturated group preferably has a glass transition temperature (Tg) of -70°C to 0°C. When the glass transition temperature (Tg) is -70°C or more, the heat resistance to heat accompanying the processing step of the wafer 5 is increased.

[0031] The resin having an ethylenically unsaturated group may be produced by any method, but a method of reacting a (meth)acrylic resin having a functional group (α) in a side chain with a compound having an ethylenically unsaturated group and a functional group (β) that reacts with the functional group (α) in the resin, thereby introducing an ethylenically unsaturated group into the side chain of the (meth)acrylic resin, is preferred.

[0032] The ethylenically unsaturated group may be any of the following groups, but is preferably a (meth)acryloyl group, a (meth)acryloyloxy group, a (meth)acryloylamino group, an allyl group, a 1-propenyl group, or a vinyl group (including styrene or a substituted styrene), and more preferably a (meth)acryloyl group or a (meth)acryloyloxy group. Examples of the functional group (β) that reacts with the functional group (α) include a carboxyl group, a hydroxyl group, an amino group, a mercapto group, a cyclic acid anhydride group, an epoxy group, and an isocyanate group.

[0033] Here, when one of the functional groups (α) and (β) is a carboxyl group, a hydroxyl group, an amino group, a mercapto group, or a cyclic acid anhydride group, the other functional group may be an epoxy group or an isocyanate group, and when one functional group is a cyclic acid anhydride group, the other functional group may be a carboxyl group, a hydroxyl group, an amino group, or a mercapto group. Note that when one functional group is an epoxy group, the other functional group may be an epoxy group.

[0034] The (meth)acrylic resin having a functional group (α) in the side chain is obtained by polymerizing a (meth)acrylic acid ester, acrylic acid, or (meth)acrylamide having a functional group (α). Examples of the functional group (α) include a carboxyl group, a hydroxyl group, an amino group, a mercapto group, a cyclic acid anhydride group, an epoxy group, and an isocyanate group, and the like. The carboxyl group and the hydroxyl group are preferred, and the hydroxyl group is particularly preferred.

[0035] Examples of such monomers include acrylic acid, methacrylic acid, cinnamic acid, itaconic acid, fumaric acid, phthalic acid, 2-hydroxyalkyl acrylates, 2-hydroxyalkyl methacrylates, glycol monoacrylates, glycol monomethacrylates, N-methylol acrylamide, N-methylol methacrylamide, allyl alcohol, N-alkylaminoethyl acrylates, N-alkylaminoethyl methacrylates, acrylamides, methacrylamides, maleic anhydride, itaconic anhydride, fumaric anhydride, phthalic anhydride, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, and polyisocyanate compounds in which a portion of the isocyanate groups has been urethanized with a monomer having a hydroxyl group or a carboxyl group and a radiation-curable carbon-carbon double bond. Among these, acrylic acid, methacrylic acid, 2-hydroxyalkyl acrylates, 2-hydroxyalkyl methacrylates, glycidyl acrylate, and glycidyl methacrylate are preferred, acrylic acid, methacrylic acid, 2-hydroxyalkyl acrylates, and 2-hydroxyalkyl methacrylates are more preferred, and 2-hydroxyalkyl acrylates and 2-hydroxyalkyl methacrylates are even more preferred.

[0036] The resin having an ethylenically unsaturated group is preferably a copolymer of the above monomer with other monomers such as (meth)acrylic acid esters. Examples of (meth)acrylic acid esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, decyl acrylate hexyl acrylate, and methacrylates corresponding thereto. The (meth)acrylic acid ester may be one or more, but it is preferable to use one having an alcohol moiety with 5 or less carbon atoms and one having 6 to 12 carbon atoms in combination. The resin having an ethylenically unsaturated group is preferably a copolymer of (meth)acrylic acid and (meth)acrylic acid in addition to (meth)acrylic acid esters.

[0037] The polymerization reaction of the resin having an ethylenically unsaturated group, particularly the resin having an ethylenically unsaturated group, may be any of solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization. When a (meth)acrylic resin having a functional group (α) in a side chain is reacted with a compound having an ethylenically unsaturated group and a functional group (β) that reacts with the functional group (α) in the resin, one of them is reacted in excess, and the functional group is left unreacted, so that the desired adhesive properties and elastic modulus can be adjusted.

[0038] As the polymerization initiator, radical generators such as azobis-based initiators such as α,α'-azobisisobutylnitrile and organic peroxide-based initiators such as benzoyl peroxide are usually used. In this case, a catalyst and a polymerization inhibitor can be used in combination as necessary, and a resin having a desired molecular weight can be obtained by adjusting the polymerization temperature and polymerization time. In addition, it is preferable to use a mercaptan or carbon tetrachloride-based solvent to adjust the molecular weight.

[0039] The average molecular weight of the resin having an ethylenically unsaturated group is preferably about 200,000 to 1,500,000, more preferably 700,000 to 1,200,000. By reducing the amount of low molecular weight components, contamination of the surface of the wafer 5 can be suppressed, and it is preferable that, for example, molecules having a molecular weight of 100,000 or less account for 10% or less of the total. If the molecular weight exceeds 1,500,000, gelation may occur during synthesis and coating. It is preferable that the resin having an ethylenically unsaturated group has an OH group with a hydroxyl value of 5 to 100 mgKOH / g, since this further reduces the risk of tape peeling failure by reducing the adhesive strength after radiation exposure.

[0040] A compound having an ethylenically unsaturated group and a functional group (β) that reacts with the functional group (α) will be described. The ethylenically unsaturated group is preferably the group described above, and the preferred range is also the same. The functional group (β) that reacts with the functional group (α) can be the group described above. As the functional group (β), an isocyanate group is particularly preferred.

[0041] Examples of the compound having a functional group (β) that reacts with an ethylenically unsaturated group and a functional group (α) include a monomer compound having a functional group (α) and a (meth)acrylate having an isocyanate group in the alcohol portion, and a (meth)acrylate having an isocyanate group in the alcohol portion is preferred. Examples of the (meth)acrylate having an isocyanate group in the alcohol portion are preferably those having an isocyanate group at the end of the alcohol portion, and the number of carbon atoms other than the isocyanate group in the alcohol portion is preferably 2 to 8, and the alcohol portion is preferably a linear alkyl group. Examples of the (meth)acrylate having an isocyanate group in the alcohol portion are preferably 2-isocyanatoethyl acrylate and 2-isocyanatoethyl methacrylate.

[0042] [Crosslinking agent] As the crosslinking agent, polyisocyanates, melamine-formaldehyde resins, or epoxy compounds having two or more epoxy groups are preferred, and polyisocyanates are particularly preferred. The crosslinking agent can be used alone or in combination of two or more. The crosslinking agent can crosslink the resin polymer, thereby improving the cohesive strength of the adhesive after application of the adhesive.

[0043] Examples of polyisocyanates include hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, lysine diisocyanate, lysine triisocyanate, 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-[2,2-bis(4-phenoxyphenyl)propane]diisocyanate, and the like. Specifically, a commercially available product such as Coronate L (manufactured by Nippon Polyurethane Co., Ltd.) can be used.

[0044] As the melamine-formaldehyde resin, commercially available products such as Nikalac MX-45 (manufactured by Sanwa Chemical Co., Ltd.) and Melan (manufactured by Showa Denko Materials Co., Ltd.) can be used. Furthermore, as the epoxy resin, TETRAD-X (manufactured by Mitsubishi Chemical Co., Ltd.) can be used.

[0045] The amount of the crosslinking agent added is preferably 0.1 to 20 parts by mass, more preferably 1.0 to 10 parts by mass, per 100 parts by mass of the resin having an ethylenically unsaturated group, and the amount is appropriately adjusted according to the number of functional groups of the resin having an ethylenically unsaturated group, and to obtain the desired adhesive properties and elastic modulus. If the amount of the crosslinking agent is less than 0.1 parts by mass, the effect of improving the cohesive strength tends to be insufficient, and if it exceeds 20 parts by mass, the curing reaction proceeds rapidly during the blending and application of the adhesive, and a crosslinked structure tends to be formed, which may impair workability.

[0046] [Photopolymerization initiator] When a radiation-curable adhesive is selected as the adhesive layer 3, a photopolymerization initiator may be included as necessary. The photopolymerization initiator is not particularly limited as long as it reacts with radiation transmitted through the base resin film 2, and a conventionally known photopolymerization initiator may be used. For example, benzophenone, 4,4'-dimethylaminobenzophenone, 4,4'-diethylaminobenzophenone, 4,4'-dichlorobenzophenone, and other benzophenones, acetophenone, diethoxyacetophenone, and other acetophenones, 2-ethylanthraquinone, t-butylanthraquinone, and other anthraquinones, 2-chlorothioxanthone, benzoin ethyl ether, benzoin isopropyl ether, benzyl, 2,4,5-triaryl-imidazole dimer (lophine dimer), acridine compounds, acylphosphine oxides, and the like may be mentioned, and these may be used alone or in combination of two or more kinds. The amount of the photopolymerization initiator added is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the resin having an ethylenically unsaturated group.

[0047] [Other additives] The adhesive layer 3 may contain a tackifier, an adhesive regulator, a surfactant, or a modifier, if necessary. In addition, an inorganic compound filler may be added as appropriate. In the present invention, it is also preferable to add a modifier from the viewpoint of peelability. Examples of modifiers include silicone compounds, fluorine-based compounds, and compounds containing long-chain alkyl groups. By adding the modifier, the peel force at a low angle can be reduced, and the contact angle with water can be increased, thereby suppressing dust penetration. In order to prevent the transfer of the modifier to the surface of the wafer 5, it is preferable that the modifier is a compound having an ethylenically unsaturated group, and more preferably, the adhesive base resin is a resin having an ethylenically unsaturated group in the side chain. Specific examples of modifiers having an ethylenically unsaturated group include commercially available products such as Ebecryl 360 (manufactured by Daicel-Allnex Corporation), which is a silicone acrylate, and Megafac RS-72-K (manufactured by DIC Corporation), which is a fluorine-based surface modifier. From the viewpoint of the influence on the surface of the wafer 5, a fluorine-based compound is more preferable.

[0048] The adhesive layer 3 can be formed, for example, by applying the above-mentioned adhesive composition onto a release film, drying it, and transferring it onto the intermediate layer 4 described below. The adhesive layer 3 may be composed of multiple layers. In that case, for example, the above-mentioned adhesive composition is applied onto a release film, dried, and transferred onto the intermediate layer 4 to form one adhesive layer 31, and the above-mentioned adhesive composition is separately applied onto a release film, dried, and the resulting adhesive layer 32 is laminated onto the adhesive layer 31 to form the adhesive layer 3. Alternatively, the adhesive composition of the adhesive layer 31 may be applied onto the intermediate layer 4, and the adhesive layer 32 may be laminated thereon, and the adhesive composition may be applied to the adhesive layer 32 and dried.

[0049] (Middle tier 4) Moreover, the adhesive tape 1 for wafer grinding of the present invention has an intermediate layer 4 between the base resin film 2 and the adhesive layer 3. As the intermediate layer 4, a resin or an adhesive can be used.

[0050] Examples of the resin used in the intermediate layer 4 include a resin made of an ethylene-based copolymer, which is a copolymer of ethylene and at least one comonomer selected from a radically polymerizable acid comonomer, an acrylic acid ester comonomer, a methacrylic acid ester comonomer, and a vinyl carboxylate comonomer, a resin made of a homopolymer or copolymer of a monomer containing an ethylenically unsaturated group such as an ionomer, and a resin made of polyethylene (for example, low-density polyethylene). The intermediate layer 4 used in the adhesive tape 1 for wafer grinding of the present invention may use one of these resins alone or two or more of them in combination.

[0051] Specific examples of the radically polymerizable acid comonomer include α,β-unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, and itaconic acid, and anhydrides thereof, and unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, vinylacetic acid, and pentenoic acid. Of these, maleic anhydride, acrylic acid, and methacrylic acid are preferred. Specific examples of the acrylic acid ester comonomer include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate, with methyl acrylate, ethyl acrylate, and butyl acrylate being preferred.

[0052] Specific examples of the methacrylic acid ester comonomer include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate, with methyl methacrylate and ethyl methacrylate being preferred. Specific examples of the vinyl carboxylate comonomer include vinyl formate, vinyl acetate, vinyl propionate, and vinyl butyrate, with vinyl acetate being preferred.

[0053] Specific examples of ethylene-based copolymers include binary copolymers such as ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-maleic anhydride copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl methacrylate copolymer, and ethylene-vinyl acetate copolymer. Examples of ternary copolymers include ethylene-acrylic acid-methyl acrylate copolymer, ethylene-acrylic acid-ethyl acrylate copolymer, ethylene-acrylic acid-vinyl acetate copolymer, ethylene-methacrylic acid-methyl methacrylate copolymer, ethylene-methacrylic acid-ethyl methacrylate copolymer, ethylene-methacrylic acid-vinyl acetate copolymer, ethylene-maleic anhydride-methyl acrylate copolymer, ethylene-maleic anhydride-ethyl acrylate copolymer, ethylene-maleic anhydride-methyl methacrylate copolymer, ethylene-maleic anhydride-ethyl methacrylate copolymer, ethylene-maleic anhydride-methyl methacrylate copolymer, ethylene-maleic anhydride-ethyl methacrylate copolymer, and ethylene-maleic anhydride-vinyl acetate copolymer. Further, multi-component copolymers combining the above comonomers are also included. Among the above copolymers, particularly preferred are ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-maleic anhydride-methyl acrylate copolymer, ethylene-maleic anhydride-ethyl acrylate copolymer, ethylene-maleic anhydride-methyl methacrylate copolymer and ethylene-maleic anhydride-ethyl methacrylate copolymer, and more preferred are ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer and ethylene-butyl acrylate copolymer.

[0054] In the total mass of ethylene and comonomer used in the synthesis of the ethylene-based copolymer, the proportion of the comonomer is preferably from 10% by mass to 50% by mass, and more preferably from 15% by mass to 40% by mass.

[0055] The resin constituting the intermediate layer 4 may be a single layer or multiple layers. Methods for forming multiple layers include film formation by coextrusion and lamination with an adhesive.

[0056] The adhesive used for the intermediate layer 4 may be the adhesive used for the adhesive layer 3 described above, but is preferably a non-radiation curable adhesive.

[0057] Examples of the non-radiation curable adhesive (adhesive resin, base resin) used in the intermediate layer 4 include acrylic adhesives. Examples of the acrylic adhesive include (meth)acrylic acid ester copolymers composed of a (meth)acrylic acid ester monomer or a structural unit derived from a (meth)acrylic acid ester monomer and (meth)acrylic acid. Examples of the (meth)acrylic acid ester monomer include (meth)acrylic acid cycloalkyl ester, (meth)acrylic acid benzyl ester, (meth)acrylic acid alkyl ester having an alkyl group with 1 to 18 carbon atoms, and (meth)acrylic acid ester having a hydroxyl group in the alcohol moiety (e.g., hydroxyethyl acrylate).

[0058] As the other components other than the adhesive component, those having good compatibility with the adhesive component are preferable, and as long as there is no problem with the adhesiveness, a tackifier, an adhesive regulator, a surfactant or other modifiers can be blended as necessary. In addition, an inorganic compound filler may be added as appropriate. In the present invention, the intermediate layer 4 is preferably a non-radiation curable type, but a small amount of a radiation curable oligomer or the like (for example, 1 to 50 parts by mass per 100 parts by mass of the above-mentioned adhesive resin (base resin) of the intermediate layer) may be added for the purpose of improving peelability, improving cohesive force, and improving interlayer adhesion with the radiation curable adhesive layer on the intermediate layer, within a range that does not affect the cure shrinkage.

[0059] The adhesive composition may contain a crosslinking agent as required. The crosslinking agent is a compound selected from polyisocyanates, melamine-formaldehyde resins, and epoxy resins, and may be used alone or in combination of two or more. The crosslinking structure formed as a result of reaction with the (meth)acrylic copolymer can improve the cohesive strength of the adhesive after application. The polyisocyanates are not particularly limited, and examples thereof include hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, lysine diisocyanate, lysine triisocyanate, 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-[2,2-bis(4-phenoxyphenyl)propane]diisocyanate, and the like. Specifically, a commercially available product such as Coronate L (manufactured by Nippon Polyurethane Co., Ltd.) can be used. As the melamine-formaldehyde resin, specifically, commercially available products such as Nikalac MX-45 (manufactured by Sanwa Chemical Co., Ltd.) and Melan (manufactured by Showa Denko Materials Co., Ltd.) can be used. Furthermore, as the epoxy resin, TETRAD-X (manufactured by Mitsubishi Chemical Co., Ltd.) can be used.

[0060] The amount of the crosslinking agent added is preferably 0.1 to 20 parts by mass per 100 parts by mass of the adhesive resin (base resin), and the amount is appropriately adjusted according to the number of functional groups (e.g., hydroxyl groups, carboxyl groups, amino groups, mercapto groups) of the adhesive resin (base resin) that can react with the crosslinking agent, and to obtain the desired adhesive properties and elastic modulus. If the amount added is less than 0.1 parts by mass, the effect of improving the cohesive force tends to be insufficient, and if it exceeds 20 parts by mass, the curing reaction tends to proceed rapidly during the blending and application of the adhesive, and a crosslinked structure tends to be formed, which may impair workability. The amount of the crosslinking agent added is preferably 0.1 to 5 parts by mass in order to achieve the storage modulus as described above.

[0061] The intermediate layer 4 can be formed by applying the above-mentioned pressure-sensitive adhesive composition onto the base resin film 2 and drying it, or by applying it onto a release film, drying it, and transferring it to the base resin film 2. Alternatively, the intermediate layer 4 may be formed by applying a resin or composition constituting the intermediate layer 4, laminating and applying the composition of the pressure-sensitive adhesive layer 3 thereon, and drying it, which is useful in terms of improving interlayer adhesion between the intermediate layer 4 and the pressure-sensitive adhesive layer 3 and improving work efficiency.

[0062] The adhesive tape 1 for wafer grinding of the present invention is prepared by attaching a double-sided tape to the surface of the adhesive tape 1 for wafer grinding opposite to the adhesive layer 3, that is, in this embodiment, the surface of the base resin film 2 opposite to the surface on which the intermediate layer 4 is provided, fixing the adhesive tape 1 for wafer grinding to a measurement stage with the double-sided tape, and pressing a measurement terminal into the adhesive tape 1 for wafer grinding by 20 μm at a temperature of 50° C., and measuring the loss tangent obtained by torsional shear measurement is 0.12 to 0.35. The double-sided tape used is one having a thickness of 5 to 10 μm, conforming to JIS Z0237, and having an adhesive strength of 5 N / 20 mm or more against a polished SUS surface measured at a peel angle of 180° and a peel speed of 300 mm / min using a universal tensile tester under an environment of 23° C. and 50% RH.

[0063] The measurement temperature for the torsional shear measurement is preferably the temperature applied when the adhesive tape 1 for wafer grinding is actually adhered to the wafer 5, and is generally preferably 25 to 90° C., and more preferably 50° C. If the temperature is less than 50° C., the conformability to the uneven pattern of the wafer is insufficient, and if the temperature exceeds 50° C., the adhesive tape 1 for wafer grinding shrinks due to heat during application, raising concerns about warping of the wafer 5 after application of the adhesive tape 1 for wafer grinding, so it is preferable to measure the dynamic viscoelasticity at 50° C.

[0064] If the indentation depth is less than 20 μm, the error in the indentation depth significantly affects the value, making it impossible to obtain an accurate elastic modulus value.If the indentation depth is more than 20 μm, the contribution of the elastic modulus of the base resin film 2 in the adhesive tape 1 for wafer grinding becomes large, and the elastic modulus of the adhesive layer 3, which is greatly involved in the conformability to irregularities, cannot be detected.

[0065] If the loss tangent is less than 0.12, the adhesive tape 1 for wafer grinding cannot adequately conform to the irregularities on the surface of the wafer 5, the adhesive layer 3 cannot adhere sufficiently to the protrusions, and the stress during grinding is concentrated on the protrusions, which may cause grinding marks called dimples or damage to the wafer 5 during grinding. If the loss tangent is more than 0.35, the stress during back grinding is not uniformly transmitted to the wafer 5, which may result in poor thickness accuracy of the wafer 5 after grinding.

[0066] The loss tangent is a value measured using a dynamic viscoelasticity measuring device at a strain of 0.1 and a measuring frequency of 1 Hz.

[0067] The loss tangent can be adjusted by the amount of curing agent in the adhesive layer 3 or intermediate layer 4, the molecular weight of the polymer, or the monomer composition. The loss tangent of the adhesive tape 1 for wafer grinding can be adjusted to the above range by making the loss tangent of the intermediate layer 4 alone higher than the loss tangent of the adhesive layer 3 alone. The loss tangent of the intermediate layer 4 alone and the loss tangent of the adhesive layer 3 alone are measured using a dynamic viscoelasticity measuring device at a temperature rise rate of 5°C / min from 0°C and a measurement frequency of 1 Hz, and are the values ​​when the temperature reaches 25°C.

[0068] In addition, the adhesive tape 1 for wafer grinding is preferably such that a double-sided tape is affixed to the surface of the adhesive tape 1 for wafer grinding opposite to the adhesive layer 3, the adhesive tape 1 for wafer grinding is fixed to a measurement stage with the double-sided tape, and a measurement terminal is pressed 20 μm into the adhesive tape 1 for wafer grinding at a temperature of 50° C., and the storage modulus obtained by torsional shear measurement is 53 kPa to 159 kPa.

[0069] If the storage modulus is less than 53 kPa, the stress during back grinding will not be uniformly transmitted to the wafer 5, which may result in poor thickness accuracy of the wafer 5 after grinding. If the storage modulus exceeds 159 kPa, the adhesive tape 1 for wafer grinding will not be able to adequately conform to the irregularities on the surface of the wafer 5, and the adhesive layer 3 will not adhere sufficiently to the protruding portions, causing the stress during grinding to concentrate on the protruding portions, resulting in the generation of grinding marks called dimples, or the wafer 5 may be damaged during grinding.

[0070] The storage modulus is a value measured by a dynamic viscoelasticity measuring device in the same manner as in the above-mentioned measurement of the loss tangent, at a strain of 0.1 and a measurement frequency of 1 Hz.

[0071] The storage modulus can be adjusted by the amount of curing agent, the molecular weight of the polymer, and the monomer composition in the adhesive layer 3 and the intermediate layer 4. The storage modulus of the adhesive tape 1 for wafer grinding can be adjusted to the above range by making the storage modulus of the intermediate layer 4 alone higher than that of the adhesive layer 3 alone. The storage modulus of the intermediate layer 4 alone and the storage modulus of the adhesive layer 3 alone are measured using a dynamic viscoelasticity measuring device at a temperature rise rate of 5°C / min from 0°C and a measurement frequency of 1 Hz, and are the values ​​when the temperature reaches 25°C.

[0072] The thickness of the intermediate layer 4 is 20 to 150% of the thickness of the adhesive layer 3. If the thickness of the intermediate layer is less than 20% of the thickness of the adhesive layer, the intermediate layer will not adequately relieve stress during grinding, causing chip chipping due to vibration during grinding. If the thickness of the intermediate layer is more than 150% of the thickness of the adhesive layer, the intermediate layer will excessively relieve stress, and the stress during back grinding will not be uniformly transmitted to the wafer 5, which may result in poor thickness accuracy of the wafer 5 after grinding.

[0073] (Release film) In addition, in the adhesive tape 1 for wafer grinding of the present invention, a release film is provided on the adhesive layer 3 as necessary. The release film is also called a separator, release layer, or release liner, and is provided for the purpose of protecting the adhesive layer 3 and for the purpose of smoothing the adhesive. Examples of the material constituting the release film include synthetic resin films such as polyethylene, polypropylene, and polyethylene terephthalate, and paper. In order to enhance the releasability from the adhesive layer 3, the surface of the release film may be subjected to a release treatment such as silicone treatment, long-chain alkyl treatment, and fluorine treatment as necessary. In addition, it is also preferable to perform an ultraviolet protection treatment as necessary so that the adhesive layer 3 does not react due to exposure to unintended ultraviolet rays such as environmental ultraviolet rays. The thickness of the release film is usually 10 to 100 μm, preferably about 25 to 50 μm.

[0074] <Application> The adhesive tape 1 for wafer grinding of the present invention can be suitably used in a method for processing a wafer 5 using a pre-dicing method or a pre-stealth method, for example, in the following methods for processing a wafer 5 (A) to (B).

[0075] Manufacturing method of wafer 5 (A) (a) forming a groove 7 on a line along which the wafer 5 is to be cut, the groove 7 being formed from the surface of the wafer 5 to a thickness less than the thickness of the wafer 5; (b) a step of laminating the above-mentioned adhesive tape 1 for wafer grinding to the surface of the wafer 5 on which the grooves 7 are formed; (c) grinding the back surface of the wafer 5 to separate the wafer 5 into individual pieces.

[0076] Manufacturing method of wafer 5 (B) (a) forming a modified region inside the wafer 5 along a line to be cut of the wafer 5 by irradiating the wafer 5 with a laser; (b) before or after the step (a), a step of laminating the above-mentioned adhesive tape 1 for wafer grinding to the surface of the wafer 5; (c) A method for producing a wafer 5, comprising the step of grinding a back surface of the wafer 5 to separate the wafer 5 into individual pieces.

[0077] <How to use> Next, a description will be given of an example of a method of using the adhesive tape 1 for wafer grinding of the present invention, i.e., a method of processing a wafer 5. First, as shown in Fig. 3, a blade (not shown) or a laser is used to form grooves 7 in the wafer 5 from the front side thereof, the grooves having a depth equal to or greater than the thickness of the final product (groove cutting step), and then the adhesive layer 3 of the adhesive tape 1 for wafer grinding is attached to the front surface of the wafer 5 on which a circuit pattern has been formed (protective tape attachment step).

[0078] Next, as shown in FIG. 4(A), the wafer 5 with the groove 7 formed thereon is ground by a grinding device 8 in a grinding process for grinding the back surface thereof until the groove 7 is reached as shown in FIG. 4(B). This separates the wafer 5 into chips 11. At this time, the adhesive tape 1 for wafer grinding is fixed to a measurement stage with double-sided tape, and the measurement terminal is pressed in by 20 μm at a temperature of 50° C., and the loss tangent obtained by torsional shear measurement is 0.12 to 0.35. By using the adhesive tape 1 for wafer grinding of the present invention, it is possible to suppress shear page and wafer breakage. If necessary, polishing or etching is performed after the grinding process in order to improve the flexural strength of the wafer 5. Chemical mechanical polishing (CMP) can be used as the polishing.

[0079] After the grinding and polishing steps are completed, as shown in Fig. 5, a dicing tape 6 or a dicing die bonding film is attached to the back surface of the wafer 5, and a ring frame 9 is attached to the outer periphery of the dicing tape 6. Then, as shown in Fig. 6, the adhesive tape 1 for wafer grinding is peeled off.

[0080] Thereafter, for example, as shown in FIG. 7, the dicing tape 6 with the wafer 5 and ring frame 9 bonded together is placed on a stage (not shown) of an expanding device, and with the ring frame 9 fixed, the push-up member 10 of the expanding device is raised to expand the dicing tape 6.

[0081] Then, as shown in FIG. 8, chip 11 is pushed up from the back side of dicing tape 6 by push-up pin 12 and picked up by suction with collet 13, whereby semiconductor chip 11 can be obtained.

[0082] Although the above describes the method of using the adhesive tape 1 for wafer grinding using the first dicing method, the first stealth method may be used instead of the first dicing method. When the first stealth method is used, a modified area forming step is performed in which a modified area is formed by irradiating a laser inside the wafer 5 instead of the groove cutting step. The modified area forming step may be performed after the protective tape laminating step.

[0083] <Example> The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0084] [Preparation of Base Resin Film] A base resin film was prepared as follows.

[0085] [Base resin film 2A] A 50 μm thick PET (polyethylene terephthalate) film that had been corona-treated on both sides and a 25 μm thick PP (polypropylene) film were laminated via a 10 μm thick adhesive layer to obtain a base resin film 2A.

[0086] [Base resin film 2B] A PET film having a thickness of 50 μm and having been corona-treated on one side was prepared as the base resin film 2B.

[0087] [Preparation of Pressure-Sensitive Adhesive Layer Composition] A resin composition for the pressure-sensitive adhesive layer was prepared as follows.

[0088] [Adhesive layer 3A] 100 parts by mass of a copolymer consisting of 86 parts by mass of 2-ethylhexyl acrylate, 13 parts by mass of 2-hydroxyacrylate, and 1 part by mass of methacrylic acid were reacted with 10 parts by mass of methacryloyloxyethyl isocyanate as a radiation reactive group, and 0.9 parts by mass of Coronate L (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) as a polyisocyanate and 5.0 parts by mass of SPEEDCURE BKL (trade name, manufactured by DKSH Japan Co., Ltd.) as a photopolymerization initiator were added and mixed to obtain a resin composition for adhesive layer 3A.

[0089] [Adhesive layer 3B] A composition for pressure-sensitive adhesive layer 3B was obtained in the same manner as the resin composition for pressure-sensitive adhesive layer 3A, except that the blending amount of Coronate L (product name, manufactured by Nippon Polyurethane Industry Co., Ltd.) was changed to 0.5 parts by mass.

[0090] [Adhesive layer 3C] A composition for pressure-sensitive adhesive layer 3C was obtained in the same manner as for the resin composition for pressure-sensitive adhesive layer 3A, except that the blending amount of Coronate L (product name, manufactured by Nippon Polyurethane Industry Co., Ltd.) was changed to 1.3 parts by mass.

[0091] [Adhesive layer 3D] A composition of adhesive 3D was obtained in the same manner as the resin composition of adhesive 3A, except that 86 parts by mass of butyl acrylate was used instead of 86 parts by mass of 2-ethylhexyl acrylate, and the amount of Coronate L (product name, manufactured by Nippon Polyurethane Industry Co., Ltd.) was changed to 0.5 parts by mass.

[0092] [Preparation of resin composition for intermediate layer and preparation of resin] The resin composition for the intermediate layer was adjusted and the resin was prepared as follows.

[0093] [Middle layer 4A] A resin composition for the intermediate layer 4A was obtained by adding and mixing 0.5 parts by mass of Coronate L (product name, manufactured by Nippon Polyurethane Industry Co., Ltd.) as a polyisocyanate to 100 parts by mass of a copolymer consisting of 73 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl acrylate, 2 parts by mass of 2-hydroxyacrylate, and 5 parts by mass of methacrylic acid.

[0094] [Preparation of adhesive tape for wafer grinding] [Example 1] The resin composition of the intermediate layer 4A was applied to a PET separator having a thickness of 38 μm so that the film thickness after drying was 10 μm, and then dried to obtain the intermediate layer 4A. The resin composition of the adhesive layer 3A was applied to a PET separator having a thickness of 38 μm so that the film thickness after drying was 50 μm, and then dried to obtain the adhesive layer 3A. Then, the intermediate layer 4A was attached to the PET surface of the base resin film 2A and the separator was peeled off, and the adhesive layer 3B was attached to the upper surface of the intermediate layer 4A and the separator was peeled off, and the adhesive tape for wafer grinding according to Example 1 was obtained.

[0095] [Example 2] An adhesive tape for wafer grinding according to Example 2 was obtained in the same manner as in Example 1, except that the thickness of the adhesive layer was set to 30 μm.

[0096] [Example 3] An adhesive tape for wafer grinding according to Example 3 was obtained in the same manner as in Example 1, except that the thickness of the intermediate layer was 30 μm and the thickness of the adhesive layer was 20 μm.

[0097] [Example 4] An adhesive tape for wafer grinding according to Example 4 was obtained in the same manner as in Example 1, except that the thickness of the intermediate layer was set to 35 μm and the thickness of the adhesive layer was set to 20 μm.

[0098] [Example 5] An adhesive tape for wafer grinding according to Example 5 was obtained in the same manner as in Example 1, except that the thickness of the intermediate layer was set to 30 μm and the thickness of the adhesive layer was set to 10 μm.

[0099] [Example 6] An adhesive tape for wafer grinding of Example 6 was obtained in the same manner as Example 1, except that the resin composition of adhesive layer 3B was used as the resin composition of the adhesive layer, the thickness of the adhesive layer was 30 μm, and the intermediate layer was omitted.

[0100] [Example 7] An adhesive tape for wafer grinding according to Example 7 was obtained in the same manner as in Example 1, except that the resin composition of the adhesive layer 3D was used as the resin composition of the adhesive layer, and the thickness of the adhesive layer was 30 μm.

[0101] [Example 8] An adhesive tape for wafer grinding according to Example 8 was obtained in the same manner as in Example 1, except that base resin film 2B was used as the base resin film and the thickness of the adhesive layer was set to 50 μm.

[0102] [Comparative Example 1] An adhesive tape for wafer grinding according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the resin composition of adhesive layer 3B was used as the resin composition of the adhesive layer, and the thickness of the adhesive layer was 30 μm.

[0103] [Comparative Example 2] An adhesive tape for wafer grinding according to Comparative Example 2 was obtained in the same manner as in Example 2, except that the resin composition of the adhesive layer 3C was used as the resin composition of the adhesive layer.

[0104] [Characteristics evaluation test] The adhesive tapes for wafer grinding of the above Examples and Comparative Examples were subjected to characteristic evaluation tests as described below.

[0105] (1) Storage modulus and loss tangent The storage modulus (G') and loss tangent (tan δ) of the wafer grinding adhesive tapes of the above examples and comparative examples were measured by the following method. The wafer grinding adhesive tape was prepared, and a viscoelasticity measuring device HAAKE MARS40 (product name) manufactured by Thermo Fisher Scientific was used to attach a double-sided tape to one side of the base resin film on which the adhesive layer of the wafer grinding adhesive tape was not provided, and the wafer grinding adhesive tape was fixed to the measurement stage. A measuring terminal of 8 mmΦ was pressed 20μ into the adhesive layer surface of the wafer grinding adhesive tape at a temperature of 50°C, and dynamic viscoelasticity was measured by torsional shear measurement with a strain amount of 0.1 and a measurement frequency of 1 Hz, and the storage modulus, loss modulus, and loss tangent were obtained. The loss tangent (tan δ) can be calculated using the following formula. Loss tangent (tan δ) = loss modulus (G'') / storage modulus (G') The storage modulus and loss tangent of the adhesive tape for wafer grinding at 50°C are shown in Tables 1 and 2. The double-sided tape used was "PET-based ultra-thin 5 μm double-sided tape No. 5600" (manufactured by Nitto Denko Corporation), which uses a polyester film as a substrate and has an acrylic adhesive applied to both sides.

[0106] (2) Ability to follow uneven surfaces The adhesive layer surface of each of the adhesive tapes for wafer grinding prepared in the Examples and Comparative Examples was attached to a 12-inch mirror wafer having a cutting groove of 30 μm width and 100 μm depth under heating at 50° C., and the unevenness followability was evaluated using a laser microscope. Evaluation was performed according to the following criteria. The evaluation results are shown in Tables 1 and 2. ◯: Adhesion was achieved without generating air at the interface between the adhesive tape for wafer grinding and the mirror wafer, and between the adhesive tape for wafer grinding and the cut groove. Δ: No air was generated at the interface between the adhesive tape for wafer grinding and the mirror wafer, but air was generated between the adhesive tape for wafer grinding and the cut groove, taking up less than 20% of the total area of ​​the cut groove. ×: Air was generated between the adhesive tape for wafer grinding and the cut groove, taking up 20% or more of the total area of ​​the cut groove, and / or air was generated at the interface between the adhesive tape for wafer grinding and the mirror wafer.

[0107] (3) Evaluation of wafer thickness accuracy after grinding The adhesive tape for wafer grinding prepared in the examples and comparative examples was laminated to 25 mirror wafers using DR8500II (trade name) manufactured by Nitto Seiki Co., Ltd. under the conditions of table temperature and roller temperature of 50°C, lamination pressure of 0.35MPa, and lamination speed at a low speed (9mm / sec). Then, using a grinder with an in-line mechanism [DFG8760 (trade name) manufactured by Disco Corporation], back grinding and dry polishing were performed on each of the 25 mirror wafers until the final thickness was 100μm. Then, the thickness accuracy TTV (difference between maximum thickness and minimum thickness) of the wafer was measured using SemDex (thickness accuracy measuring device, manufactured by ISIS Co., Ltd.). The measurement interval was 0.1mm in the X direction and 10mm in the Y direction, and the entire wafer (200mm x 200mm range) was measured. As a result, those with an average TTV of less than 4μm were evaluated as acceptable products with a mark of ○, those with an average TTV of 4μm or more but less than 6μm were evaluated as acceptable products with a mark of △, and those with an average TTV of 6μm or more were evaluated as defective products with a mark of ×. The evaluation results are shown in Tables 1 and 2.

[0108] (4) Evaluation of chipping After the above grinding, a high-pressure mercury lamp was used from the base resin film side, with an accumulated irradiation dose of 500 mJ / cm 2 After irradiating the wafer with ultraviolet light to harden the adhesive layer and reduce the adhesive strength, each chip was peeled off from the wafer grinding adhesive tape and the chip edge was observed under a microscope for chipping. Chips with 10 or fewer chips were evaluated as good products with a circle, those with 11 to 19 chips were evaluated as acceptable products with a triangle, and those with 20 or more chips were evaluated as defective products with a cross. The evaluation results are shown in Tables 1 and 2.

[0109] (5) Evaluation of peelability The adhesive tape for wafer grinding prepared in the examples and comparative examples was cut to a width of 25 mm and a length of 150 mm, the separator on one side was peeled off, and a 2 kg rubber roller was rolled back and forth three times on a stainless steel plate of 1.5 mm thickness specified in JIS G 4305, which had been finished with waterproof abrasive paper No. 280 specified in JIS R 6253, to press the plate. The plate was left to cure for one hour as a measurement sample, and the 90 degree peel strength was measured at a speed of 50 mm / min using a tensile tester. As a result, the peel strength was evaluated as ◯ for less than 4.9 N / 25 mm, △ for 4.9 N / 25 mm or more and less than 5.1 N / 25 mm, and × for 5.1 N / 25 mm or more. The evaluation results are shown in Tables 1 and 2.

[0110] [Table 1] [Table 2]

[0111] As shown in Table 1, the adhesive tapes for wafer grinding according to Examples 1 to 8 have a loss tangent of 0.12 to 0.35, and therefore show good results in the evaluation of the irregularity conformability, the thickness accuracy of the wafer after grinding, and chip chipping. The adhesive tapes for wafer grinding according to Examples 4 and 5 have an intermediate layer thickness exceeding 150% of the thickness of the adhesive layer, and therefore show slightly inferior results in the evaluation of the thickness accuracy of the wafer after grinding, but within the acceptable range. The adhesive tape for wafer grinding according to Example 5 has a storage modulus of more than 159 kPa, and therefore shows slightly inferior results in the evaluation of the irregularity conformability, but within the acceptable range. The thickness of the intermediate layer according to Example 6 is less than 20% of the thickness of the adhesive layer, and therefore shows slightly inferior results in the evaluation of the chip chipping, but within the acceptable range.

[0112] On the other hand, as shown in Table 2, the adhesive tape for wafer grinding according to Comparative Example 1 had a loss tangent exceeding 0.35, and thus was inferior in the evaluation of the thickness precision of the ground wafer. On the other hand, the adhesive tape for wafer grinding according to Comparative Example 2 had a loss tangent less than 0.12, and thus had poor conformability to irregularities. [Explanation of symbols]

[0113] 1: Wafer grinding adhesive tape 2: Base resin film 3: Middle layer 4: Adhesive layer 5: Wafer 6: Dicing tape 7: Groove 8: Grinding device 9: Ring frame 11: Tip

Claims

1. An adhesive tape for wafer grinding comprising a base resin film, a pressure-sensitive adhesive layer formed on at least one side of the base resin film, and an intermediate layer provided between the base resin film and the pressure-sensitive adhesive layer, the intermediate layer is formed of a pressure-sensitive adhesive composition, The adhesive tape for wafer grinding is characterized in that a double-sided tape is affixed to a surface of the adhesive tape for wafer grinding opposite to the adhesive layer, the adhesive tape for wafer grinding is fixed to a measurement stage with the double-sided tape, and a measurement terminal is pressed 20 μm into the adhesive tape for wafer grinding at a temperature of 50° C., and a loss tangent obtained by torsional shear measurement is 0.12 to 0.

35.

2. The adhesive tape for wafer grinding according to claim 1, characterized in that a double-sided tape is affixed to a surface of the adhesive tape for wafer grinding opposite to the adhesive layer, the adhesive tape for wafer grinding is fixed to a measurement stage with the double-sided tape, and a measurement terminal is pressed 20 μm into the adhesive tape for wafer grinding at a temperature of 50° C., and a storage modulus obtained by torsional shear measurement is 53 kPa to 159 kPa.

3. 3. The adhesive tape for wafer grinding according to claim 1, wherein the thickness of the intermediate layer is 20 to 150% of the thickness of the adhesive layer.

4. 4. The adhesive tape for wafer grinding according to claim 1, which is used in a process in which a wafer is cut and then the back surface of the wafer is ground to divide it into chips, or in a process in which a modified region is formed by irradiating a laser inside the wafer and then the back surface of the wafer is ground to divide it into chips.

Images