JP4991348B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to an adhesive sheet, and more particularly to an adhesive sheet suitable for use in protecting a semiconductor circuit during processing of a semiconductor wafer on which a high-density wiring pattern is formed.

  In a semiconductor wafer, after a circuit is formed on the front surface, grinding processing is performed on the back surface side of the wafer to adjust the thickness of the wafer. During the grinding process, a protective sheet made of an adhesive sheet is attached to the circuit surface formed on the surface to protect the circuit. In such a protective sheet, in addition to preventing damage to the circuit and the wafer body, the adhesive does not remain on the circuit after being peeled (glue residue), and grinding water is used for washing away grinding and cooling. It is required to prevent intrusion into the circuit surface and to maintain sufficient thickness accuracy of the wafer after grinding. As such a protective sheet, it is known to use an adhesive sheet (for example, Patent Document 1) having an ultraviolet curable adhesive.

  In a normal processing process, a semiconductor wafer is formed into chips by a dicing process after a grinding process. In recent semiconductor manufacturing processes, the diameter of semiconductor wafers has become larger and the thickness has been made extremely thin. Therefore, semiconductor wafers are very easily damaged, and handling of the wafers after the grinding process has become difficult. Yes. For this reason, a prior dicing process (DBG process) in which half-cut dicing is performed on the wafer prior to the grinding process and the wafer is chipped simultaneously with grinding is promising. In the DBG process, the protective sheet is attached to the circuit surface of the half-cut wafer (for example, Patent Document 2).

The protective sheet used in the normal process only needs to be in close contact with the circuit surface of the wafer to the extent that intrusion of grinding water can be prevented at the outer periphery of the wafer. On the other hand, in the DBG process, since the wafer is chipped in the middle of grinding, the protective sheet used needs to have sufficient adhesion to the surface to prevent the penetration of cleaning water for each chip. It is said that. Thus, when the adhesiveness of the protective sheet is increased in order to adhere to the circuit surface of the wafer, there is a problem that the adhesive residue tends to increase on the circuit surface after peeling. For this problem, an adhesive sheet having an ultraviolet curable adhesive has been used as a protective sheet (for example, Patent Document 3).
Also, in the DBG process, unlike normal grinding, the chips are divided into small pieces during grinding, so that the original chip interval is destroyed by a large grinding pressure applied to each chip (kerf shift). )there is a possibility. Thus, when the alignment of the chips is lost, there is a problem that a defect occurs due to contact between the chips in the grinding process, the next transport process, and the pickup process.
JP 60-189938 A JP-A-5-335411 JP 2000-68237 A

  As the shape of the semiconductor component changes, elements (electrodes, etc.) having a relatively uneven difference are often incorporated in the outer periphery of the semiconductor chip, so that the large unevenness is concentrated in a narrow area, leading to the outer periphery of the chip. It is difficult to adhere. For this reason, the protective sheet used in the DBG process has a problem that adhesion to the circuit (unevenness followability) is insufficient and there is a risk that infiltration of grinding water may increase. And when uneven | corrugated followable | trackability is improved, there existed a problem that the cohesive force of an adhesive fell and it became easy to produce a kerf shift.

  Therefore, the present invention is excellent in adhesive force, has an uneven surface followability to the wafer circuit surface, etc., can prevent intrusion of grinding water or the like into the wafer circuit surface at the time of grinding, does not cause kerf shift, and is adhesive. It aims at realizing the adhesive sheet which does not produce an agent residue.

  The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet comprising a base material and an energy ray-curable pressure-sensitive adhesive layer formed on the surface of the base material, and the energy ray-curable pressure-sensitive adhesive layer has 4 carbon atoms. An energy ray-curable acrylic copolymer obtained by copolymerizing 1 to 30% by weight of a dialkyl (meth) acrylamide having the following alkyl group and having an unsaturated group in the side chain, and urethane acrylate, To do.

  The energy ray curable acrylic copolymer reacts with a functional group-containing monomer and an acrylic copolymer containing a dialkyl (meth) acrylamide having an alkyl group having 4 or less carbon atoms as a monomer and a functional group of the functional group-containing monomer. It is generated by a reaction with an unsaturated group-containing compound having a substituent, and the unsaturated group-containing compound having a substituent of 20 to 100 equivalents is preferably reacted with 100 equivalents of the functional group.

  The energy ray curable pressure-sensitive adhesive layer is preferably produced by blending 1 to 200 parts by weight of a urethane acrylate oligomer with respect to 100 parts by weight of the energy ray curable acrylic copolymer.

  It is preferable that the storage elastic modulus of the energy ray-curable pressure-sensitive adhesive layer in the state before energy ray curing is 0.04 MPa or more and 0.11 MPa or less at 25 ° C., and the value of tan δ is 0.6 or more at 25 ° C. .

  The adhesive strength in the state before energy beam curing is preferably 7000 mN / 25 mm or more, and the adhesive strength in the state after energy beam curing is preferably 500 mN / 25 mm or less.

  According to the present invention, the adhesive strength is excellent, the concave and convex followability to the wafer circuit surface, etc., it is possible to prevent the intrusion of grinding water or the like into the wafer circuit surface during grinding, and no kerf shift occurs, and An adhesive sheet that does not produce an adhesive residue can be realized.

  Hereinafter, embodiments of the pressure-sensitive adhesive sheet according to the present invention will be described. The pressure-sensitive adhesive sheet includes a base material and an energy ray-curable pressure-sensitive adhesive layer formed on the surface of the base material. The pressure-sensitive adhesive sheet is used by being attached to a semiconductor wafer so that the energy ray-curable pressure-sensitive adhesive layer is in contact with the circuit surface. And when a semiconductor wafer is processed by the tip dicing process mentioned later, the back surface of a semiconductor wafer is ground in the state where the adhesive sheet was stuck. At this time, the pressure-sensitive adhesive sheet protects the semiconductor wafer by preventing grinding water from entering the circuit surface, contacting the divided chips, and the like.

  Hereinafter, the energy ray curable pressure-sensitive adhesive layer will be described. The energy ray curable pressure-sensitive adhesive layer mainly comprises a blend of an energy ray curable acrylic copolymer and an energy ray curable urethane acrylate oligomer (urethane acrylate). The energy ray curable acrylic copolymer comprises a reaction product in which both are chemically bonded by a reaction between the acrylic copolymer and the unsaturated group-containing compound. Furthermore, the energy ray curable pressure-sensitive adhesive layer contains components such as a crosslinking agent in addition to the energy ray curable acrylic copolymer and the urethane acrylate.

  Each component of the energy ray curable pressure-sensitive adhesive layer will be described below. The acrylic copolymer is a copolymer of a main monomer, dialkyl (meth) acrylamide (N, N-dialkyl (meth) acrylamide), a functional group-containing monomer, and the like.

  The main monomer is used because the energy ray-curable pressure-sensitive adhesive layer has basic properties for functioning as a pressure-sensitive adhesive layer. As the main monomer, for example, a structural unit derived from a (meth) acrylic acid ester monomer or a derivative thereof is used. As the (meth) acrylic acid ester monomer, those having 1 to 18 carbon atoms in the alkyl group can be used. Among these, particularly preferred are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and the like. is there. These main monomers are preferably contained in an amount of 50 to 90% by weight as monomers constituting the acrylic copolymer.

  Further, the acrylic copolymer contains dialkyl (meth) acrylamide as a constituent monomer. By using dialkyl (meth) acrylamide as a constituent monomer, the compatibility of the energy ray-curable acrylic copolymer with a highly polar urethane acrylate can be improved. The dialkyl (meth) acrylamide used in the present invention is dialkyl acrylamide or dialkyl methacrylamide having an alkyl group having 4 or less carbon atoms, preferably dimethyl (meth) acrylamide, diethyl (meth) acrylamide, etc., particularly preferably. Dimethyl (meth) acrylamide is used.

  This is because these dialkyl (meth) acrylamides have an amino group whose reactivity is suppressed by an alkyl group and do not adversely affect the polymerization reaction, etc. The most polar dimethylacrylamide is a highly polar one. This is because it is particularly suitable for improving the solubility of the energy ray curable acrylic copolymer in urethane acrylate. In addition, it is preferable that dialkyl (meth) acrylamide is contained in the ratio of 1 to 30 weight% as a monomer which comprises an acryl-type copolymer.

  The functional group-containing monomer is used for bonding the unsaturated group-containing compound to the acrylic copolymer or for providing a functional group necessary for the reaction with a crosslinking agent described later. That is, the functional group-containing monomer is a monomer having a polymerizable double bond and a functional group such as hydroxyl group, carboxyl group, amino group, substituted amino group, and epoxy group in the molecule, preferably a hydroxyl group-containing compound. A carboxyl group-containing compound or the like is used.

  More specific examples of functional group-containing monomers include hydroxyl group-containing (meth) acrylates such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, or acrylic acid, Carboxyl group-containing compounds such as methacrylic acid and itaconic acid, amino group-containing (meth) acrylates such as 2-aminoethylacrylamide and 2-aminoethylmethacrylamide, substituted amino groups such as monomethylaminoethylacrylamide and monomethylaminoethylmethacrylamide Epoxy group-containing (meth) acrylates such as containing (meth) acrylate, glycidyl acrylate and glycidyl methacrylate are included. These functional group-containing monomers are preferably contained in an amount of 1 to 30% by weight as monomers constituting the acrylic copolymer.

  The acrylic copolymer is obtained by copolymerizing the above main monomer, dialkyl (meth) acrylamide, and functional group monomer by a known method, but may contain monomers other than these monomers. For example, vinyl formate, vinyl acetate, styrene, or the like may be copolymerized with an acrylic copolymer at a ratio of up to about 10% by weight.

  Next, the unsaturated group-containing compound will be described. Unsaturated group-containing compounds are used to provide energy ray-curable acrylic copolymers with energy ray-curing properties, and by adding unsaturated group-containing compounds that cause a polymerization reaction upon irradiation with ultraviolet rays or the like, energy ray curing is achieved. The type acrylic copolymer has energy ray curability. That is, an energy ray curable acrylic is obtained by a reaction between an acrylic copolymer having a functional group generated as described above and an unsaturated group-containing compound having a substituent that reacts with the functional group of the acrylic copolymer. A copolymer is produced.

  The substituent of the unsaturated group-containing compound varies depending on the functional group of the acrylic copolymer, that is, the type of the functional group of the monomer used in the acrylic copolymer. For example, the functional group is a hydroxyl group or a carboxyl group. In the case of a group, an isocyanate group, an epoxy group or the like is preferable as a substituent. When the functional group is an amino group or a substituted amino group, an isocyanate group or the like is preferable as a substituent, and the functional group is an epoxy group. In addition, a carboxyl group or the like is preferable as the substituent. One such substituent is contained in each molecule of the unsaturated group-containing compound.

  Further, the unsaturated group-containing compound contains about 1 to 5, preferably 1, or 2 double bonds for polymerization reaction in one molecule. Examples of such unsaturated group-containing compounds include, for example, methacryloyloxyethyl isocyanate, meta-isopropenyl-α, α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, glycidyl (meth) acrylate, (meth ) Acrylic acid and the like.

  The unsaturated group-containing compound is used in a proportion of about 20 to 100 equivalents, preferably 40 to 90 equivalents, and more preferably about 50 to 80 equivalents with respect to 100 equivalents of the functional group of the acrylic copolymer. The reaction between the acrylic copolymer and the unsaturated group-containing compound is carried out under normal conditions, for example, using a catalyst in a solvent such as ethyl acetate and stirring at room temperature and normal pressure for 24 hours. .

  As a result of this reaction, the functional group present in the side chain of the acrylic copolymer and the substituent in the unsaturated group-containing compound reacted, and the unsaturated group was introduced into the side chain of the acrylic copolymer. An energy ray curable acrylic copolymer is produced. The reaction rate with the substituent in the functional group by this reaction is 70% or more, preferably 80% or more, and a part of the unreacted unsaturated group-containing compound remains in the energy ray-curable acrylic copolymer. Also good. The weight average molecular weight of the energy ray curable acrylic copolymer thus produced is preferably 100,000 or more, more preferably 200,000 to 2,000,000, and the glass transition temperature is preferably −70 to 10 ° C. Degree.

  On the other hand, the urethane acrylate mixed with the energy ray curable acrylic copolymer is an oligomer having a diisocyanate molecule, a urethane bond in the structural unit, and a (meth) acryloyl group at the terminal. Urethane acrylate is a compound having a (meth) acryloyl group at its terminal functional group, such as an alkylene diol or polyether compound, which produces a urethane oligomer by reaction of a diol molecule having a hydroxyl group at the terminal with a diisocyanate molecule. And an oligomer obtained by reacting a polyether compound or polyester compound having a hydroxyl group at the terminal with a compound having a (meth) acryloyl group and an isocyanate group. Such urethane acrylate has energy ray curability by the action of the (meth) acryloyl group.

  The urethane acrylate is preferably used in a proportion of 1 to 200 parts by weight, more preferably 5 to 150 parts by weight, with respect to 100 parts by weight of the energy ray curable acrylic copolymer. The molecular weight of the urethane acrylate molecule is preferably in the range of about 300 to 30,000, from the viewpoint of compatibility with the energy ray curable acrylic copolymer, processability of the energy ray curable pressure-sensitive adhesive layer, and the like. More preferably, it is 1,000-15,000.

  A crosslinking agent may be blended in the energy ray curable pressure-sensitive adhesive layer used in the present invention. By blending the cross-linking agent, the energy ray-curable pressure-sensitive adhesive layer is partially cross-linked, and has resistance to the force applied to the energy ray-curable pressure-sensitive adhesive layer. As a result, when the pressure-sensitive adhesive sheet of the present invention is used in the previous dicing step, the chip is not easily displaced due to the shearing force of the rotating grindstone in the grinding process, that is, the kerf shift is prevented, and the end portions of the chips are Collision and damage are prevented. In the energy ray curable pressure-sensitive adhesive layer of the present application, as will be described later, the storage elastic modulus is low enough to cope with large unevenness provided on the circuit surface of the wafer. Usually, in such a pressure-sensitive adhesive layer having a low storage elastic modulus, suppression of kerf shift is insufficient even when a crosslinking agent is added. However, in this pressure-sensitive adhesive layer, the cohesive force is improved by copolymerizing a highly polar dialkyl (meth) acrylamide, and it is possible to prevent the occurrence of kerf shift while having excellent uneven followability.

  The cross-linking agent is selected so as to bind to the functional group derived from the functional group monomer. For example, when the functional group is a functional group having active hydrogen such as a hydroxyl group, a carboxyl group or an amino group, an organic polyvalent isocyanate compound, an organic polyvalent epoxy compound, an organic polyvalent imine compound, a metal chelate compound, etc. Is selected. Specifically, as organic polyvalent isocyanate compounds, for example, aromatic organic polyvalent isocyanate compounds, aliphatic organic polyvalent isocyanate compounds, alicyclic organic polyvalent isocyanate compounds, and these polyvalent isocyanate compounds Examples include trimers and terminal isocyanate urethane prepolymers obtained by reacting these polyvalent isocyanate compounds with polyol compounds. More specific examples of the organic polyvalent isocyanate compound include, for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, and 1,4-xylene diene. Isocyanate, diphenylmethane-4,4′-diisocyanate, diphenylmethane-2,4′-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4 Examples include '-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and lysine isocyanate.

  Specific examples of organic polyvalent epoxy compounds include, for example, bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, 1,3-bis (N, N diglycidylaminomethyl) benzene, 1,3-bis ( N, N diglycidylaminomethyl) toluene, N, N, N ′, N′-tetraglycidyl-4,4-diamidiphenylmethane and the like. Specific examples of the organic polyvalent imine compound include N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, Tetramethylolmethane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate, N, N′-toluene-2,4-bis (1-aziridinecarboxyamide) tri Ethylene melamine etc. are mentioned. In addition, the compounding quantity of a crosslinking agent becomes like this. Preferably it is 0.01-20 weight part with respect to 100 weight part of energy-beam curable acrylic copolymers, More preferably, it is about 0.1-10 weight part.

  When ultraviolet rays are used for curing the energy beam curable acrylic copolymer, a photopolymerization initiator is added to the energy beam curable pressure-sensitive adhesive layer. This is because the polymerization reaction time is shortened and the amount of ultraviolet irradiation is reduced. Examples of the photopolymerization initiator include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, methyl benzoin benzoate, benzoin dimethyl ketal, and 2,4-diethylthioxan. Son, α-hydroxycyclohexyl phenyl ketone, benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloranthraquinone, or 2,4,6-trimethylbenzoyldiphenylphosphine Examples include oxides. In addition, the usage-amount of a photoinitiator becomes like this. Preferably it is 0.1-10 weight part with respect to 100 weight part of energy-beam curable acrylic copolymers, More preferably, it is about 0.5-5 weight part.

  In addition, in order to satisfy various performance requirements for the energy beam curable pressure-sensitive adhesive layer, additives such as an anti-aging agent, a stabilizer, a plasticizer, and a colorant are added to the energy beam curable pressure-sensitive adhesive layer in the present invention. It is possible to mix | blend in the ratio of the grade which does not change the objective of this.

  The energy ray-curable pressure-sensitive adhesive having such a composition is a mixture of different components having a relatively high molecular weight. In general, a mixture of high molecular weights has low compatibility and various physical properties tend to be unstable. Moreover, if the compatibility is low, the pressure-sensitive adhesive tends to remain on the adherend even after energy ray curing. On the other hand, the energy ray curable pressure-sensitive adhesive layer of the present invention is copolymerized with an energy ray curable acrylic copolymer with dialkyl (meth) acrylamide, so it has excellent compatibility with urethane acrylate and has a wide range of compounding. Shows stable adhesive properties at a ratio. Since the mixture with low compatibility becomes turbid, the compatibility of the energy ray curable pressure-sensitive adhesive layer can be evaluated by the haze value.

  The energy beam curable pressure-sensitive adhesive of the present invention can achieve a low storage elastic modulus and a high tan δ value before energy beam curing by the composition and formulation as described above. That is, in the energy beam curable pressure-sensitive adhesive layer of the present invention, the value of the storage elastic modulus G ′ at 25 ° C. in the state before energy beam curing is preferably 0.04 to 0.11 MPa, particularly preferably. 0.05 to 0.1 MPa. The loss tangent at 25 ° C. (tan δ = loss elastic modulus / storage elastic modulus) is preferably 0.6 or more, and particularly preferably 0.6 to 3.

If the energy ray curable pressure-sensitive adhesive layer is in these physical property ranges, the pressure-sensitive adhesive sheet has good followability to an adherend having irregularities. If the storage elastic modulus is small, the pressure-sensitive adhesive layer is likely to be deformed even when the pressure on the pressure-sensitive adhesive sheet is weak, and if the value of tan δ is large, the deformed pressure-sensitive adhesive layer tends to return to its original shape. Becomes weaker. Therefore, when the storage elastic modulus is small and the value of tan δ is large, the adhesive sheet maintains adhesion to the surface circuit during the grinding process of the semiconductor wafer or the like, and can prevent the grinding water from entering the circuit surface of the chip. .
Further, in the energy ray curable acrylic copolymer, since dialkyl (meth) acrylamide is copolymerized, the cohesive force of the energy ray curable pressure-sensitive adhesive layer is high. As a result, when the pressure-sensitive adhesive sheet of the present invention is used in the previous dicing process, kerf shift due to the shearing force of the rotating grindstone during grinding is less likely to occur, and the ends of the chips may collide and be damaged. Is prevented.

  The thickness of the energy ray curable pressure-sensitive adhesive layer is determined according to the required surface protection performance of a semiconductor wafer or the like, and is preferably 10 to 200 μm, and particularly preferably 20 to 100 μm.

  Next, the base material will be described. There is no particular limitation on the material of the substrate, polyethylene film, polypropylene film, polybutyne film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, Polyurethane films, ethylene vinyl acetate films, ionomer resin films, ethylene / (meth) acrylic acid copolymer films, polystyrene films, polycarbonate films, fluororesin films and the like can be used. These crosslinked films and laminated films may also be used.

  In addition, a base material needs to have transparency with respect to the wavelength of the energy ray to be used. That is, when ultraviolet rays are used as the energy rays, a light transmissive film is used as the substrate. Moreover, when using an electron beam as an energy beam, the base material does not need to be light-transmitting, and a colored film may be used. Moreover, the thickness of a base material is adjusted according to the performance etc. which are requested | required of an adhesive sheet, Preferably it is 20-300 micrometers, Most preferably, it is 50-150 micrometers.

  In the pressure-sensitive adhesive sheet of the present invention, a release film may be laminated to protect the energy ray-curable pressure-sensitive adhesive layer. As the release film, a film such as polyethylene terephthalate, polyethylene naphthalate, polypropylene, polyethylene, etc., which has been subjected to a release treatment with a release agent such as a silicone resin can be used, but is not limited thereto.

  Next, the properties of the pressure-sensitive adhesive sheet will be described. The pressure-sensitive adhesive strength of the pressure-sensitive adhesive sheet of the present invention is preferably 7000 mN / 25 mm or more before energy beam curing and 500 mN / 25 mm or less after energy beam curing. Particularly preferably, it is 10000 mN / 25 mm or more before energy beam curing and 10 to 300 mN / 25 mm or less after energy beam curing. With such adhesive strength, the adhesive sheet can be maintained in close contact with the surface circuit during the grinding process of the semiconductor wafer and the like, and the adhesive sheet can be peeled without damaging the semiconductor wafer.

  Subsequently, the method for producing the pressure-sensitive adhesive sheet of the present invention will be described. The pressure-sensitive adhesive sheet contains an energy ray curable acrylic copolymer and urethane acrylate, and if necessary, a crosslinking agent, a photopolymerization initiator, and other additives, and adjusts the concentration and viscosity with an appropriate solvent to adjust the energy. A coating solution for the wire curable pressure-sensitive adhesive layer is applied to the release-treated surface of the release film and dried to form an energy beam-curable pressure-sensitive adhesive layer having a predetermined thickness. It can be manufactured by laminating on one side. Examples of the coating method include a method using a known coating apparatus such as a gravure coater, a die coder, a roll coater, a knife coater, a roll knife coater, and a curtain coater. Moreover, you may manufacture an adhesive sheet by the method of apply | coating a coating liquid directly to a base material, making it dry, and laminating | stacking a peeling film.

  A DBG process in processing a semiconductor wafer will be described. In the DBG process, a groove having a depth of cut shallower than the wafer thickness is formed from the wafer surface on which the semiconductor circuit is formed, and the back surface of the semiconductor wafer is ground to thin the wafer. Divide into chips. In such a DBG process, the adhesive sheet can be used as a means for protecting the wafer surface and a means for temporarily fixing the wafer.

  Specifically, the pressure-sensitive adhesive sheet is used in a DBG process including the following steps. First, a groove having a predetermined depth is cut from the wafer surface along a street for partitioning a plurality of circuits. Next, an adhesive sheet is bonded to the wafer so as to cover the entire surface of the wafer provided with the grooves. At this time, an electrode, a protective film, and the like are incorporated on the wafer surface by a circuit forming process, and the wafer has complicated irregularities. The pressure-sensitive adhesive sheet of the present invention can sufficiently follow the unevenness of the circuit surface because the storage elastic modulus of the pressure-sensitive adhesive layer before curing with energy rays can be reduced and the value of tan δ and the adhesiveness can be set large. Then, in order to divide the wafer into a plurality of chips, the adhesive sheet of the present invention has the above-mentioned physical properties during the grinding process in which the bottom surface of the groove is removed by grinding the back surface of the wafer until a predetermined thickness is reached. It is possible to keep following the surface irregularities and reliably prevent the grinding water from entering the circuit surface of the chip.

  Thereafter, the adhesive sheet is irradiated with energy rays to reduce the adhesive force, a mounting sheet is attached to the ground surface side of the chip, and the adhesive sheet is peeled off. Here, since the adhesiveness is sufficiently lowered by curing the energy ray curable acrylic copolymer and the urethane acrylate, the adhesive sheet can be peeled without damaging the wafer due to adhesive residue or the like.

  The chips are finally picked up from the mounting sheet. Thus, by using the pressure-sensitive adhesive sheet of the present invention in the DBG process, chips can be manufactured with high yield.

  As described above, the pressure-sensitive adhesive sheet of the present invention is suitable as a protective sheet in the DBG process in the manufacturing process of a semiconductor device, but is not limited to this, and is for primary adhesion to a material having a large uneven surface. It is also suitable as an adhesive sheet. For example, it is also suitable as a protective sheet for a semiconductor wafer in a normal process. Moreover, it is also suitable for use for temporary sticking to an adherend having a smooth surface.

  Table 1 is a blending table in Examples and Comparative Examples of energy ray curable pressure-sensitive adhesives.

  The energy beam curable pressure-sensitive adhesives of Examples 1 to 8 and Comparative Examples 1 to 6 shown in Table 1 are produced as follows.

  Solution polymerization in ethyl acetate solvent using 67 parts by weight of butyl acrylate (BA) as the main monomer, 5 parts by weight of dimethylacrylamide (DMAA), and 28 parts by weight of 2-hydroxyethyl acrylate (HEA) as the functional group-containing monomer Thus, an acrylic copolymer (A1) having a weight average molecular weight of 500,000 and a glass transition temperature of −10 ° C. was produced. 100 parts by weight of the solid content of this acrylic copolymer and 8 parts by weight of methacryloyloxyethyl isocyanate (MOI) as the unsaturated group-containing compound (unsaturated group-containing monomer) (hydroxyl which is a functional group of the acrylic copolymer) 71.3 equivalents) with respect to 100 equivalents of the group to obtain an ethyl acetate solution (30% solution) of an energy ray-curable acrylic copolymer.

  With respect to 100 parts by weight of this energy ray curable acrylic copolymer, 0.625 parts by weight (solid ratio) of a polyvalent isocyanate compound CL (manufactured by Nippon Polyurethane Co., Ltd., Coronate L) and a photopolymerization initiator PI (Ciba Specialty Chemicals Co., Ltd., Irgacure 184) 3.3 parts by weight (solid ratio) were mixed, and further bifunctional urethane acrylate UA (Nihon Gosei Chemical Industry Co., Ltd., Shiku UV-3210EA, weight average molecular weight 9,000) 40 parts by weight (solid ratio) was blended to obtain the energy ray-curable pressure-sensitive adhesive of Example 1.

  This energy ray curable pressure-sensitive adhesive was applied to the release-treated surface of a polyethylene terephthalate film (thickness 38 μm) subjected to silicone release treatment as a release sheet, using a roll knife coater, so that the coating thickness after drying was 40 μm. After drying at 100 ° C. for 1 minute, it was laminated with a 110 μm-thick polyethylene film to obtain a pressure-sensitive adhesive sheet having an energy ray-curable pressure-sensitive adhesive layer having the composition and formulation shown in Table 1.

  In addition, about Examples 2-8 and Comparative Examples 1-3, the adhesive sheet was obtained like Example 1 except having changed the composition and mixing | blending of the energy-beam curable adhesive layer according to Table 1. FIG. And the energy-beam curable adhesive of Comparative Examples 4-6 is produced | generated as follows.

  84 parts by weight of butyl acrylate (BA) as main monomers, 10 parts by weight of methyl methacrylate (MMA), 1 part by weight of acrylic acid (AA), and 5 of 2-hydroxyethyl acrylate (HEA) as a functional group-containing monomer Using an amount of parts by weight, solution polymerization was carried out in an ethyl acetate solvent to produce an acrylic copolymer (A1) having a weight average molecular weight of 500,000 and a glass transition temperature of -10 ° C.

  With respect to 100 parts by weight of this acrylic copolymer, 0.625 parts by weight (solid ratio) of a polyvalent isocyanate compound CL (manufactured by Nippon Polyurethane Co., Ltd., Coronate L) and a photopolymerization initiator PI (Ciba Specialty Chemicals Co., Ltd., Irgacure 184) 3.3 parts by weight (solid ratio) is mixed, and further bifunctional urethane acrylate UA (Nippon Gosei Kagaku Co., Ltd., Shikou UV-3210EA, weight average molecular weight 9,000) is 100. The energy beam curing type adhesive of the comparative example 4 was obtained by mix | blending a weight part (solid ratio).

  The energy ray-curable pressure-sensitive adhesive layer was subjected to the same treatment as in Examples 1 to 8 and Comparative Examples 1 to 3 (see paragraph [0053]), and the energy ray-curable pressure-sensitive adhesive layer having the composition and formulation shown in Table 1 A pressure-sensitive adhesive sheet was obtained.

  In Comparative Examples 5 and 6, a pressure-sensitive adhesive sheet was obtained in the same manner as in Comparative Example 4 except that the composition and composition of the energy ray-curable pressure-sensitive adhesive layer were changed according to Table 1.

  Next, the energy ray curable pressure-sensitive adhesives of Examples and Comparative Examples and evaluation tests of pressure-sensitive adhesive sheets will be described. Table 2 is a table | surface which shows the evaluation test result in the Example and comparative example of an energy-beam curable adhesive which forms an energy-beam curable adhesive layer.

Haze: For the energy ray curable pressure-sensitive adhesives of Examples and Comparative Examples, a haze measurement was performed in the same manner except that a 100 μm thick polyester film (Toyobo Co., Ltd., Cosmo Shine A4100) was used instead of the base material. A pressure-sensitive adhesive sheet as a sample was obtained.
The release sheet of this pressure-sensitive adhesive sheet was removed, and haze was measured from the energy ray-curable pressure-sensitive adhesive surface based on JIS K7105.
Visual observation: The energy ray-curable pressure-sensitive adhesive layer was visually observed from the appearance of the pressure-sensitive adhesive sheet.
A: No separation or suspension (white turbidity) was observed in the energy ray-curable pressure-sensitive adhesive layer.
○: Slight suspension was observed in the energy ray-curable pressure-sensitive adhesive layer.
X: Clear suspension or separation was observed in the energy ray-curable pressure-sensitive adhesive layer.

Storage elastic modulus G ′, tan δ: For the energy ray-curable pressure-sensitive adhesives of Examples and Comparative Examples, energy was obtained by operating in the same manner as above except that the exposed surface was protected with a second release sheet without using a substrate. A pressure-sensitive adhesive sheet having only a line-curable pressure-sensitive adhesive layer was obtained. This pressure-sensitive adhesive sheet was laminated until the energy ray-curable pressure-sensitive adhesive had a thickness of about 4 mm, and was cut into a cylindrical shape having a diameter of 8 mm to prepare a sample for measuring viscoelasticity.
The storage elastic modulus and tan δ of this sample at 25 ° C. were measured using a viscoelasticity measuring apparatus (DYNAMIC ANALYZER RDAII, manufactured by REOMETRIC).

Adhesive strength: Examples and comparative examples using a universal tensile testing machine (Orientic Co., Ltd., TENSILON / UTM-4-100) according to JIS Z0237 except that the adherend was a mirror surface of a silicon wafer. The adhesive strength of the adhesive sheet was measured and used as the adhesive strength before energy ray curing.
Moreover, after sticking the adhesive sheet on the mirror surface of the silicon wafer and leaving it in an atmosphere of 23 ° C. and 50% RH for 20 minutes, an ultraviolet irradiation device (RAD-2000, manufactured by Lintec Co., Ltd.) is applied from the substrate side of the adhesive sheet. It was used to irradiate ultraviolet rays as energy rays (irradiation conditions: illuminance 350 mW / cm ² , light amount 200 mJ / cm ² ). About the adhesive sheet after ultraviolet irradiation, adhesive force was measured like the above, and it was set as the adhesive force after energy ray hardening.

  Holding force (cohesive force): A region occupying an area of 25 mm × 25 mm in an adhesive sheet cut to 25 mm × 100 mm was attached to a stainless steel plate, and a 2 kg roll was reciprocated 5 times on the adhesive sheet for pressure bonding. After pressure bonding, the pressure-sensitive adhesive sheet was left in an atmosphere of 23 ° C. and 50% Rh for 20 minutes, set in a creep tester at 40 ° C. and left for 15 minutes. Thereafter, a load of 1 kg was applied in the shear direction of the pressure-sensitive adhesive sheet, and measurement was started (according to JIS Z0237). A sample in which the adhesive sheet was not completely displaced from the stainless steel plate after 70,000 seconds was marked with ◯, and a sample in which the adhesive sheet was completely displaced was marked with ×.

  Followability to the circuit surface: A dummy wafer having a circuit pattern with a maximum step of 20 μm on a silicon wafer (200 mm diameter, 750 μm thickness) was prepared. The wafer was subjected to half-cut dicing from a circuit surface side to a kerf width of 40 μm and a depth of 130 μm at a pitch of 2 mm × 2 mm using a dicing apparatus (DED6361 manufactured by Disco Corporation). The adhesive sheets of Examples and Comparative Examples were attached to the circuit surface of the dummy wafer using a tape laminator (Rintech Co., RAD3500F12). Follow up when there is no air (bubbles) mixing near the step in the observation area through the substrate using a microscope (Keyence, Digital Microscope VHX-200) and observing the circuit pattern surface at a magnification of 2000x. When there was a property and mixing, it was evaluated that there was no follow-up property.

Water intrusion, adhesive residue: After evaluating the followability of the circuit surface, the wafer thickness was back ground to 100 μm using a wafer back surface grinding apparatus (DGP-8760, manufactured by Disco Corporation) and separated into chips. Next, ultraviolet rays (irradiation conditions: illuminance 350 mW / cm ² , light amount 200 mJ / cm ² ) are irradiated as energy rays using an ultraviolet irradiation apparatus (RAD-2000, manufactured by Lintec Corporation), and further a tape mounter with a tape peeling device (Adhesive tape was peeled off by Rintech Co., Ltd., RAD-2700F / 12). The exposed circuit pattern was observed with a microscope (Keyence, Digital Microscope VHX-200) for foreign matters at a magnification of 2000 times, and the presence or absence of surface contamination and adhesive residue due to the penetration of cleaning water was evaluated.

Calf shift: The amount of kerf shift of the singulated chip was observed using a microscope (manufactured by Keyence, digital microscope VHX-200). The kerf shift was evaluated based on the amount of deviation of the four chips in the central portion of the dummy wafer illustrated in FIG. That is, first, as shown in FIG. 1 (a), among the four sides of the first chip CA, sides A ₁ close to the center point P of the dummy wafer, the second chip CB adjacent to the first chip CA Of the four sides, the amount of deviation G ₁ was measured to determine how much it deviates from the extension line of side B ₁ located near the center point P of the dummy wafer and corresponding to side A ₁ . Further, among the four sides of the first chip CA, in the side A ₂ close to the center point P and adjacent to the side A ₁ , and in the third chip CC, which is another chip adjacent to the first chip CA. The shift amount G ₂ between the corresponding sides C ₂ was measured in the same manner. Then, as shown in FIG. 1 (b) ~ (d) , for also the second to fourth chips CB～CD, were similarly each measured deviation amount _G 3 ~G _8. Note that when the deviation amounts G _{1 to} G ₈ in FIG. 1 are summed, the same deviation is added twice (for example, the deviation amount G ₁ in FIG. 1A and the deviation amount in FIG. 1B). G ₄ ) Therefore, the total value of the illustrated shift amounts G _{1 to} G ₈ is divided by 2 to obtain a final total shift amount (μm) (see Table 1). Furthermore, the kerf shift was evaluated as follows based on the total value (μm) of the deviation amounts thus calculated.
◯: When the total value of the above deviations is 11 (μm) or less and the chips are not in contact with each other.
X: When the total value of the above deviations exceeds 11 (μm), or the chips are in contact with each other.

  As described above, according to the present embodiment, a dipolar (meth) acrylamide that is a highly polar monomer and does not adversely affect the polymerization reaction, the energy ray curable acrylic copolymer, and the polar By using together with high urethane acrylate, it is excellent in uneven tracking performance and adhesion to the wafer circuit surface etc., it can prevent intrusion into the wafer circuit surface of grinding water etc. during grinding and does not cause kerf shift, In addition, a pressure-sensitive adhesive sheet that does not cause a pressure-sensitive adhesive residue can be realized.

  The material of each member which comprises an adhesive sheet is not limited to what was illustrated in this embodiment. The application of the adhesive sheet is not limited to the protection of semiconductor wafers during processing by the prior dicing process, but is also used to protect semiconductor wafers in conventional processing methods or to protect the surface of parts other than semiconductor wafers. it can.

It is a figure which shows roughly the evaluation method of a kerf shift.

Claims (5)

A pressure-sensitive adhesive sheet comprising a substrate and an energy ray-curable pressure-sensitive adhesive layer formed on the surface of the substrate, wherein the energy-ray-curable pressure-sensitive adhesive layer is
An energy ray-curable acrylic copolymer obtained by copolymerizing 1 to 30% by weight of a dialkyl (meth) acrylamide having an alkyl group having 4 or less carbon atoms and having an unsaturated group in the side chain;
A pressure-sensitive adhesive sheet comprising urethane acrylate.   The energy ray-curable acrylic copolymer is an acrylic copolymer containing a functional group-containing monomer and a dialkyl (meth) acrylamide having an alkyl group having 4 or less carbon atoms as monomers, and the functional group-containing monomer functionality. It is produced by a reaction with an unsaturated group-containing compound having a substituent that reacts with a group, and 20 to 100 equivalents of the unsaturated group-containing compound is reacted with 100 equivalents of the functional group. The pressure-sensitive adhesive sheet according to claim 1.   2. The energy ray curable pressure-sensitive adhesive layer is produced by blending 1 to 200 parts by weight of a urethane acrylate oligomer with respect to 100 parts by weight of the energy ray curable acrylic copolymer. 2. The adhesive sheet according to 2.   The storage modulus of the energy beam curable pressure-sensitive adhesive layer in a state before energy beam curing is 0.04 MPa or more and 0.11 MPa or less at 25 ° C., and the value of tan δ is 0.6 or more at 25 ° C. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3.   The adhesive strength in a state before energy beam curing is 7000 mN / 25 mm or more, and the adhesive strength in a state after energy beam curing is 500 mN / 25 mm or less. Adhesive sheet.