JP4711698B2 - Adhesive sheet, manufacturing method thereof, and product processing method - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive sheet and a method for producing the same, and a method for processing a product using the pressure-sensitive adhesive sheet, and in particular, in the process of precision processing a semiconductor product such as a semiconductor wafer or an optical system product, The present invention relates to a pressure-sensitive adhesive sheet used for protection, a method for producing the same, and a method for processing a product using the pressure-sensitive adhesive sheet.

In the optical industry, the semiconductor industry, and the like, an adhesive sheet is used for protecting the surface of a wafer or the like and preventing damage when optical parts such as lenses or semiconductor products such as a semiconductor wafer are precision processed.
For example, in a semiconductor chip manufacturing process, after slicing a high-purity silicon single crystal or the like into a wafer, a predetermined circuit pattern such as an IC is etched on the wafer surface to incorporate an integrated circuit, and then the back surface of the wafer is grindered Is manufactured by thinning the wafer to about 100 to 600 μm, and finally dicing into chips. Since the semiconductor wafer itself is thin and fragile, and the circuit pattern has irregularities, it is easily damaged when an external force is applied during conveyance to a grinding process or a dicing process. Also, in the polishing process, polishing processing is performed while cleaning the back surface of the wafer with purified water in order to remove the generated polishing debris or to remove the heat generated during polishing. It is necessary to prevent this. For this purpose, in order to protect the circuit pattern surface and the like and prevent damage to the semiconductor wafer, an operation is performed by attaching an adhesive sheet to the circuit pattern surface. At the time of dicing, adhesive sheets are attached to the back side of the wafer, and the wafer is diced with the wafer bonded and fixed, and the chip to be formed is picked up by a needle from the film substrate side and picked up and fixed on the die pad. Yes. Examples of the pressure-sensitive adhesive sheet used here include a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on a base material sheet such as polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), and ethylene-vinyl acetate copolymer (EVA). It has been known. Japanese Patent Laid-Open No. 61-10242 discloses a silicon wafer processing film in which an adhesive layer is provided on the surface of a base sheet having a Shore D hardness of 40 or less. Japanese Patent Application Laid-Open No. 9-253964 discloses a pressure-sensitive adhesive tape in which a pressure-sensitive adhesive layer is provided on a base material obtained by radiation-curing a compound containing a urethane acrylate oligomer and a reactive diluent monomer. In JP-A-61-266029, an auxiliary film having a Shore D hardness of greater than 40 is laminated on one surface of a substrate film having a Shore D hardness of 40 or less. A silicon wafer processing film having an adhesive layer provided on the other surface is disclosed. JP-A-2002-69396 discloses a low elastic modulus film having a storage elastic modulus (E ′) of 1 × 10 ⁵ to 1 × 10 ⁸ Pa and a thickness of 10 to 150 μm as an outermost layer, and a storage as an inner layer. For protecting a semiconductor wafer formed from a base film of at least three layers having an elastic modulus (E ′) of 2 × 10 ⁸ to 1 × 10 ¹⁰ Pa and a high elastic modulus film having a thickness of ¹⁰ to 150 μm. An adhesive film is disclosed. Japanese Patent Laid-Open No. 2000-38556 discloses a semiconductor wafer protection sheet having a hot melt layer having a melting point of 105 ° C. or lower.

  However, in recent years, the level difference of the unevenness of the circuit pattern surface has increased, and with the miniaturization of the chip, the semiconductor wafer has been required to have a thickness of 100 μm or less. For example, in an adhesive sheet using a rigid base material such as PET, the warpage of the wafer after thin film grinding is suppressed, but it cannot follow the unevenness of the circuit pattern surface of the wafer surface, and the adhesive layer and pattern Adhesion with the surface became insufficient, and peeling of the sheet occurred during wafer processing, or grinding water and foreign matter entered the pattern surface. In addition, an adhesive sheet using a soft base material such as EVA has no problem in following the pattern surface. However, since the base material has insufficient rigidity, warping may occur after wafer grinding, Deflection caused by. Therefore, a base material in which a rigid base material PET and a soft base material EVA are bonded together is assumed, but when mechanically bonded through an adhesive, the stress applied during bonding Will remain in the film and the substrate will curl. Moreover, when forming a laminated body by T-die method, a calendar method, etc., it is difficult to obtain a thick film, and a residual stress will generate | occur | produce in a film by the heat shrink at the time of film forming. As described above, the pressure-sensitive adhesive sheet using the base material in which the residual stress is generated has a problem that the wafer is damaged during the grinding of the wafer or the wafer is warped after the grinding. In addition, when a laminate is formed by a solution coating method, the use of a solvent may cause environmental problems. Further, in order to obtain a thick film, repeated coating is necessary.

  Japanese Patent Application Laid-Open No. 2004-107644 discloses a pressure-sensitive adhesive sheet in which a specific film is laminated, and shows that it is effective for these problems.

  By the way, the pressure-sensitive adhesive sheet used for such a purpose needs to prevent the adherend such as a wafer from being contaminated by particles such as organic matter and adhesive residue resulting from the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer. Conventionally, solvent-type acrylic pressure-sensitive adhesives have been used as pressure-sensitive adhesives, but since solvent-type acrylic pressure-sensitive adhesives are synthesized in organic solvents, there is an environmental problem with the volatilization of solvents during coating. Conversion to a water-dispersed acrylic pressure-sensitive adhesive has been attempted. However, the water-dispersed acrylic pressure-sensitive adhesive uses an emulsifier as compared with the solvent-type acrylic pressure-sensitive adhesive, so that it is difficult to achieve low contamination.

  Further, it is known that contaminants on the wafer surface affect the shear strength of wire bonding. In other words, wire bonding performed when manufacturing a semiconductor chip requires high adhesion strength between the ball and the pad, but organic substances and particles adhering to the aluminum surface on the wafer are transferred to the aluminum surface of the gold wire. When a large amount of contaminants adhere to the aluminum surface, the wire bonding shear strength is reduced.

  Particularly in recent years, with the increase in density and performance of semiconductor integrated circuits, the management of contamination on the circuit surface of semiconductor wafers and semiconductor chips obtained therefrom has become stricter. Therefore, the wafer processing pressure-sensitive adhesive sheet is required to have lower contamination than ever before.

Japanese Patent Application Laid-Open No. 61-10242 Japanese Patent Laid-Open No. 9-253964 Japanese Patent Laid-Open No. 61-260629 JP 2002-69396 A JP 2000-38556 A JP 2004-107644 A

  The present invention has been made to solve the above-described problems. For example, even if the semiconductor wafer after polishing is thin, the wafer is not damaged during the grinding process, and the semiconductor wafer is bent. The present invention provides a pressure-sensitive adhesive sheet that is small and further has low warpage due to residual stress of the pressure-sensitive adhesive sheet, and that can achieve low contamination, and a method for manufacturing the same, and a processing method for processing a product such as a semiconductor wafer using the pressure-sensitive adhesive sheet. For the purpose.

  The pressure-sensitive adhesive sheet of the present invention has an intermediate layer and a pressure-sensitive adhesive layer in this order on one side of a base material having a tensile elastic modulus at 25 ° C. of 600 MPa or higher, and the intermediate layer has a tensile elastic modulus at 25 ° C. of 1 MPa or higher. An acrylic polymer layer of 100 MPa or less.

  Here, the acrylic polymer forming the acrylic polymer layer preferably includes an acrylic polymer into which a nitrogen-containing monomer is introduced by copolymerization.

  In addition, the intermediate layer may be formed by applying a mixture containing a radical polymerizable monomer on a substrate and irradiating and curing the radiation. Here, the radical polymerizable monomer is preferably an acrylic monomer.

  In the pressure-sensitive adhesive sheet of the present invention, the thickness (t1) of the substrate is 10 μm or more and 200 μm or less, the thickness (t2) of the intermediate layer is 10 μm or more and 300 μm or less, and the thickness ratio ( (t1 / t2) can be 0.1 or more and 10 or less.

  Moreover, the adhesive sheet of this invention can have a separator for peeling on the said adhesive layer.

In the method for producing the pressure-sensitive adhesive sheet of the present invention, a mixture containing a radical polymerizable monomer is applied to one surface of a substrate having a tensile elastic modulus at 25 ° C. of 600 MPa or more, and cured by irradiation with radiation. An intermediate layer composed of an acrylic polymer layer having a tensile elastic modulus at 25 ° C. of 1 MPa or more and 100 MPa or less is formed, and an adhesive layer is formed on the intermediate layer.
Here, the radical polymerizable monomer is preferably an acrylic monomer.

  The product processing method of the present invention is characterized in that any one of the above-mentioned pressure-sensitive adhesive sheets is attached to a product to be precisely processed and held and / or protected for precision processing.

  According to the present invention, when processing a product such as a semiconductor product or an optical system product, a pressure-sensitive adhesive sheet that prevents damage to the product, does not cause a large warp in the product, and can achieve low contamination is provided. be able to. For example, even if the pressure-sensitive adhesive sheet of the present invention is adhered to a semiconductor wafer and the semiconductor wafer is thin-film polished, it will not be damaged. In addition, since the warpage of the wafer due to the residual stress of the adhesive sheet can be reduced, it can be stored in a dedicated storage case that is generally used.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.
The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having a substrate, an intermediate layer and a pressure-sensitive adhesive layer in this order. The intermediate layer is a layer made of an acrylic polymer, and has a tensile elastic modulus of 1 MPa or more and 100 MPa or less. In the present invention, the term “film” includes a sheet, and the term “sheet” includes a film.

  The substrate constituting the pressure-sensitive adhesive sheet of the present invention preferably has a tensile elastic modulus at 25 ° C. of 600 MPa or more. If the tensile elastic modulus at 25 ° C. of the substrate is 600 MPa or more, warpage of a semiconductor wafer having a thickness of 100 μm or less can be suppressed.

  Examples of the base material include polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polyethylene (PE) and polypropylene (PP), polyimide (PI), polyether ether ketone (PEEK), polyvinyl chloride ( PVC), polyvinylidene chloride resin, polyamide resin, polyurethane resin, polystyrene resin, acrylic resin, fluorine resin, cellulose resin, polycarbonate resin, and other thermosetting resins used. Among these, PET is suitable because it has an appropriate hardness when used for processing precision parts, and is also preferably used because it is advantageous in terms of variety and cost. The material of the base material is preferably selected on the condition that the tensile elastic modulus at 25 ° C. is within the above range, but is determined appropriately according to the use and the type of the pressure-sensitive adhesive layer provided as necessary. For example, when an ultraviolet curable pressure sensitive adhesive is provided, a substrate having a high ultraviolet transmittance is preferable.

  For the material constituting the substrate, additives or the like that are usually used can be used as necessary within a range that does not impair the effects of the present invention. Examples of additives include anti-aging agents, fillers, pigments, colorants, flame retardants, antistatic agents, and ultraviolet absorbers.

  The substrate may have a single layer structure, but may be a laminate composed of two or more layers. When a base material consists of a laminated body of two or more layers, each layer which comprises may be a layer which consists of a material which consists of a material of the same composition, or a different composition. However, in the case of a laminate, it is sufficient that at least one layer of the tensile elastic modulus is within the above range, and it is further preferable that the tensile elastic modulus of the entire substrate is within the above range.

  The intermediate layer constituting the pressure-sensitive adhesive sheet of the present invention is an acrylic polymer layer. The intermediate layer has a tensile modulus at 25 ° C. of 1 MPa or more and 100 MPa or less, preferably 2 MPa or more and 90 MPa or less, more preferably 5 MPa or more and 80 MPa or less. When the tensile elastic modulus at 25 ° C. of the intermediate layer is less than 1 MPa, the temperature of the intermediate layer is likely to increase due to grinding heat when grinding a product such as a semiconductor wafer, and the elastic modulus decreases when the temperature of the intermediate layer increases. As a result, the holding function of the semiconductor wafer or the like is lowered, and the semiconductor wafer or the like may be damaged. On the other hand, when the tensile elastic modulus of the intermediate layer exceeds 100 MPa, the rigidity of the pressure-sensitive adhesive sheet becomes too large, so that the semiconductor wafer or the like may be damaged in the process of grinding the semiconductor wafer or the like, and the tape is difficult to peel off. It becomes.

  As described above, the intermediate layer is an acrylic polymer layer and does not contain a urethane polymer. Since the urethane-based polymer is inferior in compatibility with the acrylic polymer, the urethane-based polymer component may pass through the pressure-sensitive adhesive layer and reach the surface of an adherend such as a semiconductor wafer (grooming). Therefore, having a urethane polymer as an intermediate layer tends to contaminate the adherend.

  The acrylic polymer forming the intermediate layer can be formed by polymerizing an acrylic monomer by a known polymerization method such as solution polymerization, emulsion polymerization or bulk polymerization.

  In this invention, you may form an intermediate | middle layer by apply | coating the mixture which contains a radically polymerizable monomer as a main component on a base material, and irradiating with radiation and hardening. Moreover, after apply | coating this mixture on a base material, the separator etc. by which peeling processing was further piled up on this, and it can also be made to cure by irradiating a radiation from this separator. Here, as the radically polymerizable monomer, one having an unsaturated double bond capable of radical polymerization is used, and a vinyl monomer or the like is used. From the viewpoint of reactivity, an acrylic monomer is preferable.

  Examples of the acrylic monomer preferably used in the present invention include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, (meth ) Pentyl acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, ( And meth) acrylic acid isobornyl. Along with these esters, monomers having carboxyl groups such as maleic acid and itaconic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, etc. Monomers having hydroxyl groups can be used.

  Further, vinyl acetate, vinyl propionate, styrene, acrylamide, methacrylamide, mono- or diester of maleic acid, and derivatives thereof, N-methylolacrylamide, glycidyl acrylate, glycidyl methacrylate, N, N-dimethylaminoethyl acrylate, N, N -Dimethylaminopropyl methacrylamide, 2-hydroxypropyl acrylate, acryloylmorpholine, N, N-dimethylacrylamide, N, N-diethylacrylamide, imide acrylate, N-vinylpyrrolidone, oligoester acrylate, ε-caprolactone acrylate, dicyclopenta Nyl (meth) acrylate, dicyclopentenyl (meth) acrylate, methoxylated cyclododecatriene acrylate, methoxyethyl Monomers may be copolymerized with such acrylate. Note that the types and amounts of the monomers to be copolymerized are appropriately determined in consideration of the characteristics of the composite film.

  In the present invention, if necessary, a polyfunctional monomer such as trimethylolpropane triacrylate or dipentaerythritol hexaacrylate may be used as a crosslinking agent. These monomers are also included in the radical polymerizable monomer according to the present invention.

  These radical polymerizable monomers are appropriately determined in kind, combination, amount of use, and the like in consideration of polymerizability at the time of photocuring such as radiation and characteristics of the high molecular weight obtained.

  The acrylic polymer used in the present invention preferably contains a nitrogen-containing monomer introduced by copolymerization. It is preferable to introduce a nitrogen-containing monomer into the acrylic polymer by copolymerization because the anchoring property with the pressure-sensitive adhesive layer is improved. As nitrogen-containing monomers, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylate, (meth) acrylamide, N-methyl ( (Meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, Nt-butyl (meth) acrylamide, (meth) acryloylmorpholine, (Meth) acryloylpyrrolidone, (meth) acryloylpiperidine, (meth) acryloylpyrrolidine and the like can be mentioned.

  In the intermediate layer, additives that are usually used, for example, an ultraviolet absorber, an anti-aging agent, a filler, a pigment, a colorant, a flame retardant, an antistatic agent and the like, as necessary, are within a range that does not impair the effects of the present invention. Can be added within. These additives are used in normal amounts depending on the type.

  In the present invention, as described above, for example, a mixture containing a radical polymerizable monomer as a main component is applied onto a substrate, and depending on the type of the photopolymerization initiator, α rays, β rays, γ rays, By irradiating with ionizing radiation such as neutron beam or electron beam, radiation such as ultraviolet rays, visible light or the like, the intermediate layer can be formed by photocuring. In addition, to a mixture in which a photopolymerization initiator is blended with a mixture containing a rigid monomer in a radical as a main component, it is irradiated with radiation such as ultraviolet rays, partially polymerized and thickened, and then applied onto a substrate. The intermediate layer may be formed by irradiation with ultraviolet rays or the like.

  At this time, in order to avoid polymerization inhibition due to oxygen, the release-treated sheet may be put on a mixture mainly composed of radically polymerizable monomers applied on the substrate to block oxygen, or inert. The base material may be put in a container filled with gas to lower the oxygen concentration.

  In the present invention, the type of radiation and the type of lamp used for irradiation can be selected as appropriate, such as a low-pressure lamp such as a fluorescent chemical lamp, a black light and a sterilization lamp, a high-pressure such as a metal halide lamp and a high-pressure mercury lamp. A lamp or the like can be used.

Irradiation amounts such as ultraviolet rays can be arbitrarily set according to required film characteristics. Generally, the dose of ultraviolet rays, 100~5,000mJ / cm ^2, preferably not 1,000~4,000mJ / cm ^2, more preferably a 2,000~3,000mJ / cm ^2. When the irradiation amount of ultraviolet rays is less than 100 mJ / cm ² , a sufficient polymerization rate may not be obtained, and when it is more than 5,000 mJ / cm ² , deterioration may be caused.

  In addition, the temperature at the time of ultraviolet irradiation is not particularly limited and can be arbitrarily set. However, if the temperature is too high, a termination reaction due to the heat of polymerization is likely to occur, which tends to cause deterioration of characteristics. Is 70 ° C. or lower, preferably 50 ° C. or lower, more preferably 30 ° C. or lower.

  The mixture containing a radical polymerizable monomer as a main component contains a photopolymerization initiator. Photopolymerization initiators include benzoin ethers such as benzoin methyl ether and benzoin isopropyl ether, substituted benzoin ethers such as anisole methyl ether, and substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone. 1-hydroxy-cyclohexyl-phenyl-ketone, substituted alpha-ketols such as 2-methyl-2-hydroxypropiophenone, aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride, 1-phenyl-1,1-propanedione- Photoactive oximes such as 2- (o-ethoxycarbonyl) -oxime are preferably used.

  The thickness of the base material and the intermediate layer in the pressure-sensitive adhesive sheet of the present invention can be appropriately selected depending on the purpose and the like. In particular, when used for processing precision parts, the thickness (t1) of the substrate is preferably 10 to 200 μm, more preferably about 30 to 200 μm, and the thickness (t2) of the intermediate layer is 10 to 300 μm. It is preferable that it is about 50-250 micrometers. Moreover, it is preferable that thickness ratio (t1 / t2) with respect to the intermediate | middle layer of a base material is t1 / t2 = 0.1-10.

  The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer on the intermediate layer. This pressure-sensitive adhesive layer has an appropriate adhesive force when processing products such as semiconductor wafers and can be reliably held, and can be easily peeled off without applying load to the products after processing. Adhesive strength that can be used is necessary. For this reason, it is preferable that the 180 degree | times peel adhesive force when peeling after a process is an adhesive layer which is the range of 0.01N / 20mm-1N / 20mm.

  The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer is not particularly limited, and known pressure-sensitive adhesives used for bonding and fixing semiconductor wafers and the like can be used, such as natural rubber and styrene-based copolymers. A rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive, a polyvinyl ether-based pressure-sensitive adhesive, etc. having a rubber-based polymer as a base polymer can be used. Among these, acrylic adhesives based on acrylic polymers are used from the viewpoints of adhesion to semiconductor wafers and cleanability of semiconductor wafers after peeling with organic solvents such as ultrapure water and alcohol. preferable.

  Examples of the acrylic polymer include (meth) acrylic acid alkyl esters (for example, methyl ester, ethyl ester, propyl ester, isopropyl ester, butyl ester, isobutyl ester, s-butyl ester, t-butyl ester, pentyl ester, isopropyl ester). Pentyl ester, hexyl ester, heptyl ester, octyl ester, 2-ethylhexyl ester, isooctyl ester, nonyl ester, decyl ester, isodecyl ester, undecyl ester, dodecyl ester, tridecyl ester, tetradecyl ester, hexadecyl ester , Octadecyl ester, eicosyl ester and the like of alkyl groups having 1 to 30 carbon atoms, in particular, linear or branched alkyl esters having 4 to 18 carbon atoms) and (meta Acrylic acid cycloalkyl esters (e.g., cyclopentyl ester, cyclohexyl ester etc.) with one or more monomer components of the acrylic polymer or the like which is obtained by polymerizing thereof. The (meth) acrylic acid ester refers to an acrylic acid ester and / or a methacrylic acid ester, and in the present invention, when expressed as (meth), all have the same meaning.

  The acrylic polymer can contain units corresponding to other monomer components copolymerizable with (meth) acrylic acid alkyl ester or cycloalkyl ester for the purpose of modifying cohesive strength, heat resistance and the like. Examples of such monomer components include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; maleic anhydride Acid anhydride monomers such as itaconic anhydride; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate , (4-hydroxymethyl Hydroxyl group-containing monomers such as cyclohexyl) methyl (meth) acrylate; styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate And sulfonic acid group-containing monomers such as (meth) acryloyloxynaphthalenesulfonic acid; phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate; acrylamide, acrylonitrile and the like. These copolymerizable monomer components can be used alone or in combination of two or more. The amount of these copolymerizable monomers used is preferably 40% by weight or less of the total monomer components.

  Further, the acrylic polymer can contain a polyfunctional monomer or the like for crosslinking. Examples of such polyfunctional monomers include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, and neopentyl glycol di (meth) acrylate. , Pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, urethane (meth) ) Acrylate and the like. These polyfunctional monomers can also be used alone or in combination of two or more. It is preferable that the usage-amount of a polyfunctional monomer is 30 weight% or less of all the monomer components from points, such as an adhesion characteristic.

  The polymerization method for forming the acrylic polymer may be any method such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization and the like. The pressure-sensitive adhesive layer preferably has a low content of a low molecular weight substance so as not to stain the sticking surface of a product such as a semiconductor wafer. From this point, the weight average molecular weight of the acrylic polymer is preferably 300,000 or more, more preferably about 400,000 to 3 million.

  Further, in order to increase the number average molecular weight of an acrylic polymer or the like, a polyisocyanate compound, an epoxy compound, an aziridine compound, a melamine crosslinking agent, or the like may be added. The amount used is appropriately determined depending on the balance with the base polymer to be crosslinked, and further depending on the intended use as an adhesive. Generally, it is preferable to mix about 1 to 5 parts by weight with respect to 100 parts by weight of the base polymer. Furthermore, you may use additives, such as conventionally well-known various tackifiers and anti-aging agent, other than the said component as needed to an adhesive.

  In the present invention, it is preferable to use a radiation curable adhesive as the adhesive. The radiation-curable pressure-sensitive adhesive is obtained, for example, by blending an adhesive component with an oligomer component that is cured by irradiation with radiation or the like to form a low-adhesion material. If a pressure-sensitive adhesive layer is formed using a radiation-curable pressure-sensitive adhesive, it can be easily applied because the plastic component is imparted to the pressure-sensitive adhesive by the oligomer component when the sheet is applied. Can be easily peeled off from a product such as a semiconductor wafer.

  As the radiation curable pressure-sensitive adhesive, those having a radiation curable functional group such as a carbon-carbon double bond in the molecule and exhibiting adhesiveness can be used. For example, an addition-type radiation-curable pressure-sensitive adhesive in which a radiation-curable monomer component or oligomer component is blended with a general pressure-sensitive adhesive, or a base polymer has a carbon-carbon double bond in the polymer side chain or main chain or the main chain. An intrinsic radiation curable pressure-sensitive adhesive having a chain end can be used. The radiation used for curing the pressure-sensitive adhesive layer includes, for example, X-rays, electron beams, ultraviolet rays, etc., and it is preferable to use ultraviolet rays for ease of handling, but it is particularly limited to these. It is not something.

As a general pressure-sensitive adhesive constituting the addition-type radiation curable pressure-sensitive adhesive, pressure-sensitive pressure-sensitive adhesives such as the above-mentioned acrylic pressure-sensitive adhesives and rubber-based pressure-sensitive adhesives can be used.
Examples of the monomer having a radiation curable functional group include urethane oligomer, urethane (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, pentaerythritol tri (meth) acrylate, and penta. Examples include erythritol tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,4-butanediol di (meth) acrylate, and the like. Examples of the radiation curable oligomer component include various oligomers such as urethane, polyether, polyester, polycarbonate, and polybutadiene, and those having a molecular weight in the range of about 100 to 30,000 are suitable. is there. The amount of the monomer component or oligomer component having a radiation-curable functional group is preferably, for example, 5 to 500 parts by weight with respect to 100 parts by weight of the base polymer such as an acrylic polymer constituting the pressure-sensitive adhesive. More preferably, it is about 40 to 150 parts by weight.

  The intrinsic radiation curable pressure-sensitive adhesive does not need to contain an oligomer component or the like that is a low polymerization component, or does not contain much, so that the situation in which the oligomer component etc. moves in the pressure-sensitive adhesive over time does not occur, A pressure-sensitive adhesive layer having a stable layer structure can be formed.

  In the intrinsic radiation-curable pressure-sensitive adhesive, a base polymer having a carbon-carbon double bond and having adhesiveness can be used without any particular limitation. Such a base polymer preferably has an acrylic polymer as its basic skeleton. As an acrylic polymer used here, the same thing as the acrylic polymer already illustrated in description of an acrylic adhesive is mentioned.

  The method for introducing the carbon-carbon double bond into the acrylic polymer as the basic skeleton is not particularly limited, and various methods can be employed. In the present invention, since the molecular design becomes easy, it is preferable to form a base polymer having a carbon-carbon double bond by introducing a carbon-carbon double bond into the side chain of the acrylic polymer. Specifically, for example, after a monomer having a functional group is copolymerized in advance with an acrylic polymer, a compound having a functional group capable of reacting with the functional group and a carbon-carbon double bond is converted into a carbon-carbon two-carbon compound. A carbon-carbon double bond can be introduced into the side chain of the acrylic polymer by condensation or addition reaction while maintaining the radiation curing property of the heavy bond.

  Examples of combinations of a functional group of a monomer copolymerized with an acrylic polymer and a functional group capable of reacting with the functional group are shown below. Examples thereof include a carboxylic acid group and an epoxy group, a carboxylic acid group and an aziridyl group, a hydroxyl group and an isocyanate group. Among these combinations of functional groups, a combination of a hydroxyl group and an isocyanate group is preferable because of easy tracking of the reaction. In addition, in the combination of these functional groups, any functional group may be on the side of the acrylic polymer of the basic skeleton. For example, in the combination of hydroxyl group and isocyanate group, the acrylic polymer has a hydroxyl group, The compound containing a functional group capable of reacting with a group preferably has an isocyanate group. In this case, examples of the compound having an isocyanate group include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, m-isopropenyl-α, α-dimethylbenzyl isocyanate and the like. Examples of the acrylic polymer having a functional group (here, hydroxyl group) include hydroxyl group-containing monomers, 2-hydroxyethyl vinyl ether compounds, 4-hydroxybutyl vinyl ether compounds already exemplified in the description of the acrylic pressure-sensitive adhesive. And those obtained by copolymerizing a diethylene glycol monovinyl ether compound or the like with an acrylic polymer.

  The internal radiation-curable pressure-sensitive adhesive can use a base polymer having a carbon-carbon double bond alone, but the above-mentioned radiation-curable monomer component and oligomer component are within the range not deteriorating the characteristics. You may mix | blend. The amount of the radiation curable oligomer component or the like is usually 30 parts by weight or less, preferably in the range of 0 to 10 parts by weight with respect to 100 parts by weight of the base polymer.

  The radiation curable pressure-sensitive adhesive contains a photopolymerization initiator when cured by ultraviolet rays or the like. Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α′-dimethylacetophenone, 2-methyl-2-hydroxypropio Α-ketol compounds such as phenone and 1-hydroxycyclohexyl phenyl ketone; methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 2-methyl-1- [4- (methylthio) -Phenyl] -2-morpholinopropane-1 and other acetophenone compounds; benzoin ethyl ether, benzoin isopropyl ether, anisoin methyl ether and other benzoin ether compounds; benzyldimethyl ketal and other ketal compounds; 2-naphthalenesulfonyl chloride Aromatic sulfonyl chloride compounds such as 1; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2- (o-ethoxycarbonyl) oxime; benzophenone, benzoylbenzoic acid, 3,3′-dimethyl- Benzophenone compounds such as 4-methoxybenzophenone; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2, Examples include thioxanthone compounds such as 4-diethylthioxanthone and 2,4-diisopropylthioxanthone; camphorquinone, halogenated ketone, acyl phosphinoxide, and acyl phosphonate.

  The compounding quantity of a photoinitiator is 1-10 weight part with respect to 100 weight part of base polymers, such as an acryl-type polymer which comprises an adhesive, Preferably it is about 3-5 weight part.

  In the present invention, the pressure-sensitive adhesive layer may be formed by applying the above-mentioned pressure-sensitive adhesive as necessary, directly on the intermediate layer, or by applying the pressure-sensitive adhesive to a release liner or the like, After the pressure-sensitive adhesive layer is formed in advance, the pressure-sensitive adhesive layer may be bonded to the intermediate layer.

  Further, the thickness of the pressure-sensitive adhesive layer is not particularly limited and can be arbitrarily set. Usually, it is preferably 3 to 100 μm, and more preferably 10 to 50 μm.

  The pressure-sensitive adhesive sheet of the present invention is used according to a conventional method for processing products such as semiconductor wafers. Here, the example used when grinding the back surface of a semiconductor wafer is shown. First, a semiconductor wafer is placed on a table so that the pattern surface of an IC circuit or the like is on top, and the pressure-sensitive adhesive sheet of the present invention is stacked on the pattern surface so that the pressure-sensitive adhesive layer is in contact with the pressure roll. Affixing while pressing with a pressing means such as. Alternatively, after placing the semiconductor wafer and the pressure-sensitive adhesive sheet as described above in a pressurizable container (for example, an autoclave), the inside of the container is pressurized to adhere the semiconductor wafer and the pressure-sensitive adhesive sheet. Alternatively, pressing means may be used in combination. Further, the semiconductor wafer and the adhesive sheet may be attached in a vacuum chamber, or may be attached by heating at a temperature not higher than the melting point of the base material of the adhesive sheet.

As a method for polishing the back surface of the semiconductor wafer, a normal grinding method can be employed. For example, a grinding machine (back grind), a CMP (Chemical Mechanical Polishing) pad, or the like is used as a processing machine for polishing the back surface of the semiconductor wafer to which the adhesive sheet is adhered as described above to a desired thickness. Grind until When using a pressure-sensitive adhesive sheet with a pressure-sensitive adhesive layer formed using radiation-curable pressure-sensitive adhesive, radiation is irradiated when grinding is completed, and the pressure-sensitive adhesive layer is reduced in adhesive strength before peeling. .

Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited thereto. In the following examples, “part” means “part by weight”.
Example 1
In a reaction vessel equipped with a condenser, a thermometer, and a stirrer, 65 parts of tert-butyl acrylate (t-BA), 25 parts of n-butyl acrylate (BA), acryloylmorpholine (ACMO) as an acrylic monomer 10 parts and 0.3 part of 2,2-dimethoxy-1,2-diphenylethane-1-one (registered trademark “Irgacure 651”, manufactured by Ciba Specialty Chemicals Co., Ltd.) as a photopolymerization initiator The syrup containing the prepolymer was prepared by adding and thickening the film by exposing it to ultraviolet rays under a nitrogen atmosphere and partially photopolymerizing it.

Next, the obtained syrup was applied onto a 75 μm thick polyethylene terephthalate film (PET film) so that the thickness after curing was 100 μm. A PET film (thickness 38 μm) peeled off as a separator was overlaid thereon and then coated with ultraviolet light (illuminance 163 mW / cm ² , light amount 2100 mJ / cm ² ) using a high-pressure mercury lamp on the coated PET film surface. Was cured by irradiation to form an intermediate layer on the PET film, and then the separator was removed. The tensile elastic modulus at 25 ° C. of the PET film was 1000 MPa.

  Next, a copolymer composed of 100 parts of n-butyl acrylate (BA) and 3 parts of acrylic acid (AA) was copolymerized in an ethyl acetate solution to give an acrylic copolymer polymer having a number average molecular weight of 260,000. Got. To 100 parts of this acrylic copolymer polymer, 2 parts of a polyisocyanate crosslinking agent and 2 parts of an epoxy crosslinking agent are mixed and applied to the intermediate layer surface formed on the base material. A pressure-sensitive adhesive layer having a layer structure of substrate / intermediate layer / pressure-sensitive adhesive layer was prepared by forming a 30 μm pressure-sensitive adhesive layer.

(Example 2)
In Example 1, as shown in Table 1, 70 parts of n-butyl acrylate (BA) and 30 parts of acryloylmorpholine (ACMO) were used as acrylic monomers, and trimethylolpropane triacrylate (TMPTA) was used as a polyfunctional monomer. ) An intermediate layer was formed on the substrate in the same manner as in Example 1 except that 0.5 part was used. Next, an adhesive layer was formed on the intermediate layer in the same manner as in Example 1 to produce an adhesive sheet.

(Example 3)
Example 1 is the same as Example 1 except that 60 parts of tert-butyl acrylate (t-BA), 30 parts of n-butyl acrylate (BA), and 10 parts of acrylic acid (AA) were used as the acrylic monomers. Similarly, an intermediate layer was formed on the substrate. Next, an adhesive layer was formed on the intermediate layer in the same manner as in Example 1 to produce an adhesive sheet.

Example 4
Example 1 is the same as Example 1 except that 70 parts of tert-butyl acrylate (t-BA), 20 parts of n-butyl acrylate (BA), and 10 parts of acryloylmorpholine (ACMO) were used as acrylic monomers. Similarly, an intermediate layer was formed on the substrate. Next, an adhesive layer was formed on the intermediate layer in the same manner as in Example 1 to produce an adhesive sheet.

(Example 5)
Example 1 is the same as Example 1 except that 65 parts of tert-butyl acrylate (t-BA), 25 parts of n-butyl acrylate (BA), and 10 parts of dimethylacrylamide (DMAA) were used as the acrylic monomers. Similarly, an intermediate layer was formed on the substrate. Next, an adhesive layer was formed on the intermediate layer in the same manner as in Example 1 to produce an adhesive sheet.

(Example 6)
In Example 1, 65 parts of tert-butyl acrylate (t-BA), 25 parts of n-butyl acrylate (BA) and 10 parts of acryloylmorpholine (ACMO) were used as the acrylic monomer, and trimethylol was used as the polyfunctional monomer. An intermediate layer was formed on the substrate in the same manner as in Example 1 except that 3 parts of propane triacrylate (TMPTA) was used. Next, an adhesive layer was formed on the intermediate layer in the same manner as in Example 1 to produce an adhesive sheet.

(Example 7)
In Example 1, as an acrylic monomer, 65 parts of t-butyl acrylate (t-BA), 25 parts of n-butyl acrylate (BA) and 10 parts of acryloylmorpholine (ACMO) were used. An intermediate layer was formed on the substrate in the same manner as in Example 1 except that the layer was formed. Next, an adhesive layer was formed on the intermediate layer in the same manner as in Example 1 to produce an adhesive sheet.

(Comparative Example 1)
In a reaction vessel equipped with a condenser, a thermometer, and a stirrer, as acrylic monomers, 25 parts of t-butyl acrylate (t-BA), 10 parts of n-butyl acrylate (BA), acrylic acid (AA) 15 parts, 3 parts of trimethylolpropane triacrylate (TMPTA) as a polyfunctional monomer, 35 parts of polytetramethylene glycol (PTMG) (Mitsubishi Chemical Corporation, molecular weight 650) as a polyol, and 2 parts as a photopolymerization initiator , 2-dimethoxy-1,2-diphenylethane-1-one (Registered Trademark “Irgacure 651”, manufactured by Ciba Specialty Chemicals Co., Ltd.), and as a urethane reaction catalyst, dibutyltin dilaurate 0.025 While stirring, 15 parts of xylylene diisocyanate (XDI) was added dropwise. In reacted for 2 hours, a urethane polymer - to obtain an acrylic monomer mixture. In addition, the usage-amount of the polyisocyanate component and the polyol component was NCO / OH (equivalent ratio) = 1.0.

The urethane polymer and acrylic monomer mixture were applied onto a 75 μm thick polyethylene terephthalate film (PET film) so that the thickness after curing was 100 μm. A PET film (thickness 38 μm) peeled off as a separator was overlaid thereon and then coated with ultraviolet light (illuminance 163 mW / cm ² , light amount 2100 mJ / cm ² ) using a high-pressure mercury lamp on the coated PET film surface. Was cured by irradiation to form an intermediate layer on the PET film. Then, the coated release-treated PET film was peeled to obtain a multilayer sheet having a base material / intermediate layer structure.

  Next, a copolymer composed of 100 parts of n-butyl acrylate (BA) and 3 parts of acrylic acid (AA) was copolymerized in an ethyl acetate solution to give an acrylic copolymer polymer having a number average molecular weight of 260,000. Got. A mixture of 2 parts of a polyisocyanate-based crosslinking agent and 2 parts of an epoxy-based crosslinking agent with respect to 100 parts of this acrylic copolymer polymer is applied on the intermediate layer surface of the resulting multilayer sheet to a thickness of 30 μm. The pressure-sensitive adhesive layer was formed to prepare a pressure-sensitive adhesive sheet.

(Comparative Example 2)
In Comparative Example 1, 20 parts of t-butyl acrylate (t-BA), 10 parts of n-butyl acrylate (BA), and 10 parts of acrylic acid (AA) were used as acrylic monomers, and trimethylol was used as a polyfunctional monomer. Using 0.1 part of propane triacrylate (TMPTA), polypropylene glycol having a number average molecular weight of 2000 ("PP-2000", manufactured by Sanyo Chemical Industries) as a polyol, and xylylene diisocyanate (XDI) 10 as a polyisocyanate A multilayer sheet was produced in the same manner as in Comparative Example 1 except that the part (NCO / OH = 1.1) was used. Moreover, the adhesive layer was formed on the intermediate | middle layer surface of the multilayer sheet like the comparative example 1 using the obtained multilayer sheet, and the adhesive sheet was produced.

(Comparative Example 3)
In Example 1, 90 parts of n-butyl acrylate (BA) and 10 parts of acrylic acid (AA) were used as acrylic monomers, and 0.1 part of trimethylolpropane triacrylate (TMPTA) was used as a polyfunctional monomer. A multilayer sheet was produced in the same manner as Example 1 except for the above. Moreover, the adhesive layer was formed on the intermediate | middle layer surface of the multilayer sheet like Example 1 using the obtained multilayer sheet, and the adhesive sheet was produced.

"Evaluation test"
(1) Tensile elasticity modulus The obtained adhesive sheet was cut into a width of 1 cm and a length of 1 cm, and an initial elasticity modulus obtained from an SS curve when only the intermediate layer was pulled in the length direction at a tension speed of 50 mm / min. Was the tensile modulus.

(2) Evaluation of warpage, sagging amount, cracking 20 sheets of 625 μm thick 8-inch silicon wafer were prepared, and the resulting adhesive sheet was used “DR-8500III” manufactured by Nitto Seiki Co., Ltd. Then, grinding was performed with a silicon wafer grinding machine manufactured by DISCO Corporation until the thickness reached 50 μm. About this, evaluation shown below was performed. The results are shown in Table 1.

(I) Warpage amount The silicon wafer after grinding was allowed to stand on the flat plate with the pressure-sensitive adhesive sheet surface facing upward with the pressure-sensitive adhesive sheet adhered. The distance from the flat plate surface of the silicon wafer portion (usually the wafer end portion) that floats most from the flat plate was measured. The average value of the amount of warpage was obtained. However, an average value obtained by averaging measured values of 20 wafers is shown. The average value of the amount of warpage is preferably 5 mm or less, and the average value exceeding 8 mm is defective.

(Ii) Slack amount The silicon wafer after grinding was stored in an 8-inch wafer storage cassette with the adhesive surface attached, with the wafer surface facing upward. For a wafer curved by its own weight, the amount of sag is defined as the distance between the position of the highest part and the position of the lowest part of the wafer that hangs down. However, an average value obtained by averaging measured values of 20 wafers is shown.

(Iii) Cracks The number of cracks in the silicon wafer during grinding was counted. However, the number of wafers ground was evaluated as 5.

(3) Evaluation of contamination The obtained adhesive sheet was attached to a silicon wafer (3 to 4 atomic%) using a tape bonding machine “DR8500” manufactured by Nitto Seiki Co., Ltd. After leaving for one day at 40 ° C. at a speed of 12 m / min), the adhesive sheet was peeled off using a tape peeling machine “HR8500” manufactured by Nitto Seiki Co., Ltd. (peeling speed 12 m / min, peeling angle 180 degrees), and wafer The organic substance transferred above was measured using ESCA “Quantum 2000” manufactured by ULVAC-PHI. Wafers without any adhesive sheet were analyzed in the same manner, and the amount of organic matter transferred was evaluated based on the increase in atomic% of detected carbon atoms.

(4) Throwing force After adhering a 50 μm thick PET tape to the surface of the pressure-sensitive adhesive layer of the obtained pressure-sensitive adhesive sheet, T peeling (at the end of the pressure-sensitive adhesive sheet and the PET tape at the interface between the pressure-sensitive adhesive layer and the intermediate layer) Peeling off at the interface between the pressure-sensitive adhesive layer and the intermediate layer by pulling 180 degrees in the opposite direction, and peeling so that the angle between the peeled adhesive sheet and the PET tape is about 180 degrees). Was measured.

  As is apparent from Table 1, the wafers processed using the adhesive sheets of Examples 1 to 7 of the present invention have a warp amount of 5 mm or less and a sag amount of less than 10 mm, and the subsequent steps. There was no problem when transporting. Moreover, even if it grind | polished the wafer to 50 micrometers in thickness using the adhesive sheet of Examples 1-7, no crack produced. Furthermore, it was found that the adhesive sheets of Examples 1 to 7 gave good results in the anchoring force evaluation and did not cause adhesive residue or the like on the adherend such as a wafer. Moreover, it turned out that the adhesive sheet of Examples 1-7 has little contamination to a wafer, and can implement | achieve low pollution property.

  On the other hand, it was found that the pressure-sensitive adhesive sheets of Comparative Examples 1 and 2 in which the intermediate layer containing the urethane component was formed were highly contaminated with the wafer. Further, the pressure-sensitive adhesive sheet of Comparative Example 3 having an intermediate layer having a tensile modulus of elasticity of less than 1 MPa had a large amount of warpage and sagging and cracks.

The pressure-sensitive adhesive sheet of the present invention can be suitably used as a pressure-sensitive adhesive sheet for processing semiconductor wafers used when grinding or dicing a semiconductor wafer. Further, in wire bonding performed at the time of manufacturing a semiconductor chip, high shear strength can be maintained without causing interface breakdown between the aluminum surface and the gold wire. Furthermore, taking advantage of the feature of low contamination, various uses such as peeling of the adhesive sheet at the time of use or after use, for example, various industrial members, especially semiconductors, circuits, various printed boards, various masks, lead frames, etc. It can be widely used as a pressure-sensitive adhesive sheet used for surface protection and damage prevention in the manufacture of microfabricated parts.

Claims (9)

On one side of a base material having a tensile elastic modulus at 25 ° C. of 600 MPa or more, an intermediate layer and an adhesive layer are provided in this order, and the intermediate layer has an acrylic polymer having a tensile elastic modulus at 25 ° C. of 1 MPa or more and 100 MPa or less. Sodea is, the pressure-sensitive adhesive sheet acrylic polymer forming the acrylic polymer layer, characterized in that it comprises an acrylic polymer was introduced by copolymerizing a nitrogen-containing monomer. The intermediate layer, the pressure-sensitive adhesive sheet according to claim 1, wherein a mixture containing a radical polymerizable monomer is coated on a substrate, the radiation is cured is referred to as being formed by. The pressure-sensitive adhesive sheet according to claim 2, wherein the radical polymerizable monomer is an acrylic monomer. The thickness (t1) of the substrate is 10 μm or more and 200 μm or less, the thickness (t2) of the intermediate layer is 10 μm or more and 300 μm or less, and the thickness ratio (t1 / t2) is 0.00. It is 1 or more and 10 or less, The adhesive sheet of any one of Claim 1 to 3 characterized by the above-mentioned. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4 , further comprising a separation separator on the pressure-sensitive adhesive layer.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein a thickness of the intermediate layer is 10 µm or more and 300 µm or less. A mixture containing a radical polymerizable monomer is applied to one surface of a substrate having a tensile modulus of elasticity of 600 MPa or more at 25 ° C., and cured by irradiation with radiation, whereby the tensile modulus of elasticity at 25 ° C. is 1 MPa or more, 100MPa Ri der hereinafter, nitrogen-containing monomers to form an intermediate layer formed of an acrylic polymer layer ing using an acrylic polymer comprising an acrylic polymer was introduced by copolymerization, the pressure-sensitive adhesive layer on the intermediate layer Forming a pressure-sensitive adhesive sheet.   The method for producing a pressure-sensitive adhesive sheet according to claim 7, wherein the radical polymerizable monomer is an acrylic monomer.   A method for processing a product, characterized in that the pressure-sensitive adhesive sheet according to any one of claims 1 to 6 is adhered to a product to be precisely processed and held and / or protected.