JP2009138183A - Adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive sheet that has an excellent followability to the uneven circuit surface of a wafer and the like, an excellent compatibility between its components, and that has excellent tensile physical properties so that it can prevent adhesive residues. <P>SOLUTION: The adhesive sheet includes an energy-ray-curable adhesive layer formed on a substrate. The energy-ray-curable adhesive layer includes an energy-ray-curable acrylic copolymer and an energy-ray-curable urethane acrylate. A polyol unit is formed using PPG and PEG in the energy-ray-curable urethane acrylate. The adhesive sheet particularly has an excellent tensile property so that it can surely prevent the generation of adhesive residues and the like in a peeling step from a wafer, in the case of using about 70% by mole of PPG in polyol. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive sheet, and more particularly to a pressure-sensitive adhesive sheet that protects the surface of a semiconductor wafer during back grinding.

  In a semiconductor wafer, after a circuit is formed on the front surface, a grinding process (back grinding) is applied to 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, it is required that the adhesive does not remain on the circuit (adhesive residue) after the protective sheet is peeled off. 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).

In the DBG process, the wafer is chipped during grinding. For this reason, in order to prevent the penetration of the cleaning water between the chips during grinding, the protective sheet used is required to have excellent adhesion to the wafer surface. Thus, since the adhesive residue tends to increase on the circuit surface after peeling when the adhesiveness of the protective sheet is increased in order to adhere to the circuit surface of the wafer, in the DBG process, particularly the adhesive residue It is necessary to suppress the occurrence. Therefore, in the DBG process, an adhesive sheet having an energy ray curable adhesive such as an ultraviolet curable adhesive may be used as a protective sheet (for example, Patent Document 3).
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, even in the normal process including the DBG process, there is a problem that the adhesion to the circuit (unevenness followability) is insufficient and the infiltration of the grinding water may increase. Furthermore, when the compatibility of the components constituting the energy beam curable pressure sensitive adhesive and the tensile physical properties of the energy beam curable pressure sensitive adhesive layer are not good, there is a problem that the pressure sensitive adhesive residue increases.

  Then, this invention aims at implement | achieving the adhesive sheet which is excellent in the uneven | corrugated followable | trackability with respect to a wafer circuit surface etc., the compatibility of structural components, etc., and is excellent in a tensile physical property and does not produce an adhesive residue.

  The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet in which an energy beam-curable pressure-sensitive adhesive layer is formed on a substrate, and the energy beam-curable pressure-sensitive adhesive layer has an unsaturated group in the side chain. A polymer and an energy ray curable urethane acrylate are included. In the pressure-sensitive adhesive sheet, the energy ray-curable urethane acrylate is a compound having an isocyanate unit, a polyol unit containing two or more kinds of polyols, and a (meth) acryloyl group.

  The polyol preferably contains polypropylene glycol and polyethylene glycol. In this case, the molar ratio of polypropylene glycol to polyethylene glycol is more preferably in the range of 9: 1 to 1: 9, and the molar ratio of polypropylene glycol to polyethylene glycol is 9: 1 to 1: 4. It is particularly preferred.

  Moreover, in an adhesive sheet, it is preferable that the breaking stress of the energy ray hardening-type adhesive layer in the state after energy ray hardening is 10 Mpa or more, and breaking elongation is 15% or more.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive sheet which is excellent in the uneven | corrugated followable | trackability with respect to a wafer circuit surface etc., the compatibility of structural components, etc., and is excellent in a tensile physical property, and does not produce an adhesive residue is realizable.

  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. For example, when the semiconductor wafer is processed by a prior dicing process, the back surface of the semiconductor wafer is ground with the adhesive sheet attached. 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 is mainly composed of an energy ray curable acrylic copolymer and an energy ray curable urethane acrylate (hereinafter also referred to as 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 such as a main monomer and a functional group-containing monomer.

  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.

  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 may further contain dialkyl (meth) acrylamide as a constituent monomer. This is because 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. As the dialkyl (meth) acrylamide, dimethyl (meth) acrylamide, diethyl (meth) acrylamide and the like are used, and dimethyl (meth) acrylamide is particularly preferably 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, dialkyl (meth) acrylamide is contained in the ratio of 1 to 30 weight% as a monomer which comprises an acryl-type copolymer, for example.

  The acrylic copolymer can be obtained by copolymerizing the above main monomer, functional group monomer, preferably dialkyl (meth) acrylamide by a known method, and even if a monomer other than these monomers is contained. good. 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 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 95 equivalents, and more preferably about 50 to 90 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 reacts with the substituent in the unsaturated group-containing compound, and the unsaturated group is introduced into the side chain of the acrylic copolymer. A linear 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.

  The energy ray curable urethane acrylate mixed with the energy ray curable acrylic copolymer will be described below. The energy ray curable urethane acrylate is a compound having an isocyanate unit and a polyol unit and having a (meth) acryloyl group at the terminal. As urethane acrylate, a urethane oligomer is produced by the reaction of a polyol having a hydroxyl group at the terminal, such as an alkylene polyol, a polyether compound, or a polyester compound, and a polyisocyanate, and a functional group at the terminal has a (meth) acryloyl group. Examples thereof include compounds obtained by reacting compounds. Such urethane acrylate has energy ray curability by the action of the (meth) acryloyl group.

  Examples of the polyisocyanate described above include isophorone diisocyanate (IPDI), 1,3-bis- (isocyanatomethyl) -cyclohexane (H6XDI), 4,4′-dicyclohexylmethane diisocyanate (H12MDI) as described later. ) And the like. These polyisocyanates are preferably used in an energy ray-curable urethane acrylate in an amount of 40 to 49 mol%. Further, among these diisocyanates, it is particularly preferable to use isophorone diisocyanate (IPDI) capable of improving the compatibility of the energy beam curable urethane acrylate with the energy beam curable acrylic copolymer.

  Moreover, as a polyol for forming the polyol unit in the energy ray curable urethane acrylate, polypropylene glycol (PPG, number average molecular weight 700), polyethylene glycol (PEG, number average molecular weight 600), polytetramethylene glycol (PTMG, Number average molecular weight 850), polycarbonate diol (PCDL, number average molecular weight 800) and the like are used. The number average molecular weight of these polyols is preferably from 300 to 2,000, particularly preferably from 500 to 1,000. Moreover, when these polyols are contained in energy ray curable urethane acrylate, it is preferable that 20 to 48 mol% is contained in energy ray curable urethane acrylate. The polyol unit contains two or more kinds of polyols, and the polyol preferably contains PPG and PEG. In particular, the polyol is preferably PPG and PEG. The molar ratio of PPG to PEG is preferably 9: 1 to 1: 9, and particularly preferably 9: 1 to 1: 4. Furthermore, the molar ratio of PPG to PEG is preferably 4: 1 to 3: 2, and most preferably 7.5: 2.5 to 6.5: 3.5.

  As the acrylate for forming the (meth) acryloyl group, 2-hydroxypropyl acrylate (2HPA), 2-hydroxyethyl acrylate (2HEA), or the like is used. These acrylates are preferably used in an amount of 4 to 40 mol% in the energy ray curable urethane acrylate.

  The energy ray curable urethane acrylate is preferably 1 to 200 parts by weight, more preferably 5 to 100 parts by weight, and still more preferably 10 to 50 parts by weight with respect to 100 parts by weight of the energy ray curable acrylic copolymer. Used in. The molecular weight of the urethane acrylate is preferably in the range of about 300 to 30,000 as the number average molecular weight from the viewpoints of compatibility with the energy ray curable acrylic copolymer, processability of the energy ray curable pressure-sensitive adhesive layer, and the like. It is. More preferably, it is an oligomer of 20,000 or less, for example 1,000 to 15,000.

  A crosslinking agent may be blended in the energy ray curable pressure-sensitive adhesive layer used in the present invention. 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. Examples of the organic polyvalent isocyanate compound include aromatic organic polyvalent isocyanate compounds, aliphatic organic polyvalent isocyanate compounds, alicyclic organic polyvalent isocyanate compounds, and the like. Specific examples of the organic polyvalent isocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylene diisocyanate, and 1,4-xylene diisocyanate. Narate, diphenylmethane-4,4′-diisocyanate, diphenylmethane-2,4′-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4 ′ -Diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, lysine isocyanate and the like. Moreover, the trimer of these polyvalent isocyanate compounds, the terminal isocyanate urethane prepolymer obtained by making these polyvalent isocyanate compounds and a polyol compound react, etc. are mentioned.

  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-diaminodiphenylmethane and the like. Specific examples of the organic polyvalent imine compound include N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, Examples include tetramethylolmethane-tri-β-aziridinylpropionate, N, N′-toluene-2,4-bis (1-aziridinecarboxamide) triethylenemelamine, and the like. 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, β-chloranthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and the like. 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, in the energy beam curable pressure-sensitive adhesive layer of the present invention, the energy beam curable urethane acrylate having the above composition is excellent in compatibility with the energy beam curable acrylic copolymer. For this reason, the energy beam curable pressure-sensitive adhesive layer exhibits stable adhesive properties. In addition, since a mixture with low compatibility becomes cloudy, the compatibility of an energy-beam curable adhesive layer can be evaluated by a haze value.

  The energy ray-curable pressure-sensitive adhesive layer preferably has a storage elastic modulus G ′ value at 25 ° C. in a state before energy ray curing of 0.15 MPa or less. Further, the loss tangent at 25 ° C. (tan δ = loss elastic modulus / storage elastic modulus) is preferably 0.2 or more. As described above, when the value of the storage elastic modulus G ′ is 0.15 MPa or less and the value of the loss tangent tan δ is 0.2 or more, the energy ray curable pressure-sensitive adhesive layer has the ability to follow the unevenness of the wafer. It is good. In addition, it is possible to reliably prevent the entry of grinding water or the like into the circuit surface.

  Further, the energy ray curable pressure-sensitive adhesive layer has a breaking stress in a state after energy ray curing is preferably 10 MPa or more, and particularly preferably 15 MPa or more. Further, the elongation at break after energy beam curing is preferably 15% or more, and particularly preferably 20% or more. Thus, when the value of the breaking stress is 10 MPa or more and the value of the breaking elongation is 15% or more, the tensile physical properties of the energy ray curable pressure-sensitive adhesive layer are good, and irradiation with ultraviolet rays or the like is insufficient. Even when the energy ray-curable pressure-sensitive adhesive layer is not sufficiently cured, it may be possible to prevent adhesion of the pressure-sensitive adhesive residue on the wafer.

  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, polybutylene 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.

  Hereinafter, the manufacturing method of an energy beam curing type adhesive is demonstrated. Table 1 is a table | surface which shows the mixing | blending of the energy beam curing type urethane acrylate in Examples 1-12 of the energy beam curing type adhesive and Comparative Examples 1-6. That is, Table 1 shows the number average molecular weight of each energy ray curable urethane acrylate and the ratio (molar ratio) of polyisocyanate, polyol, and acrylate used to produce the energy ray curable urethane acrylate.

  Ethyl acetate solvent using 73.2 parts by weight of butyl acrylate (BA) as the main monomer, 10 parts by weight of dimethylacrylamide (DMAA), and 16.8 parts by weight of 2-hydroxyethyl acrylate (2HEA) as the functional group-containing monomer Polymerization was conducted to produce an acrylic copolymer having a weight average molecular weight of 500,000 and a glass transition temperature of -10 ° C. The acrylic copolymer has a solid content of 100 parts by weight and an unsaturated group-containing compound (unsaturated group-containing monomer), methacryloyloxyethyl isocyanate (MOI), 18.7 parts by weight (the acrylic copolymer has 83 equivalents to 100 equivalents of functional groups) and diluted with ethyl acetate to obtain an ethyl acetate solution (30% solution) of energy ray-curable acrylic copolymer 1.

  In the energy ray curable urethane acrylate of Example 1, 3 parts by weight of isophorone diisocyanate (IPDI) forming a polyisocyanate unit, 1.4 parts by weight of polypropylene glycol (PPG) forming a polyol unit, polyethylene Glycol (PEG) was polymerized in 0.6 parts by weight in an ethyl acetate solvent. Thereafter, 2 parts by weight of 2-hydroxypropyl acrylate (2HPA) is mixed as an acrylate, and dibutyltin laurate is added as a reaction accelerator to react, diluted with ethyl acetate, and an energy acetate curable urethane acrylate in ethyl acetate solution (70 % Solution).

  0.37 parts by weight (solid ratio) of a polyvalent isocyanate compound CL (manufactured by Nippon Polyurethane Co., Ltd., Coronate L) as a crosslinking agent with respect to 100 parts by weight of the above-mentioned energy ray curable acrylic copolymer, and a photopolymerization initiator PI (Ciba Specialty Chemicals, Irgacure 184) 3.3 parts by weight (solid ratio) was mixed, and 10 parts by weight (solid ratio) of the above-mentioned energy ray curable urethane acrylate was blended. An energy ray-curable pressure-sensitive adhesive was obtained.

  This energy ray-curable pressure-sensitive adhesive was applied to a silicone release treatment surface, which was a release sheet, using a roll knife coater so that the coating thickness after drying was 40 μm. And after drying at 100 degreeC for 1 minute, it laminates | stacks with the 110-micrometer-thick polyethylene film which is a base material, and obtains the adhesive sheet which contains the energy-beam curable urethane acrylate of the composition of Table 1 in an energy-beam curable adhesive layer. It was.

  About Examples 2-12 and Comparative Examples 1-6, except having changed the composition and mixing | blending of energy-beam curable urethane acrylate according to Table 1, it carried out similarly to Example 1, and obtained the adhesive sheet. In addition, the energy ray-curable acrylic copolymer 2 used in Examples 7 to 12, Comparative Examples 5 and 6 and the like has 52 parts by weight of butyl acrylate (BA) as a main monomer and methyl methacrylate (MMA). ) 20 parts by weight, 28 parts by weight of 2-hydroxyethyl acrylate (2HEA) as a functional group-containing monomer, 33.7 parts by weight of methacryloyloxyethyl isocyanate (MOI) (100 equivalents of functional groups of the acrylic copolymer) It was obtained in the same manner as the energy ray curable acrylic copolymer 1 except that 90 equivalents were used.

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

Haze: For the energy ray-curable pressure-sensitive adhesives of Examples and Comparative Examples, a pressure-sensitive adhesive sheet obtained as a sample for haze measurement by operating in the same manner as above except that a polyester film having a thickness of 100 μm was used instead of the substrate. It was.
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 adhesive sheet for haze measurement.
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, the same operation as above except that the exposed surface was protected with a second release sheet without using a substrate, An adhesive sheet having only an energy ray curable adhesive layer was obtained. This adhesive sheet is laminated until the release sheet is removed and the energy ray curable adhesive is about 4 mm thick, and is cut into a cylindrical shape having a diameter of 8 mm, and viscoelasticity consisting of only the energy ray curable adhesive layer. A sample for measurement was prepared.
The storage elastic modulus G ′ and tan δ of this sample at 25 ° C. were measured using a viscoelasticity measuring apparatus (DYNAMIC ANALYZER RDAII, manufactured by REOMETRIC).

Breaking stress, breaking elongation: in accordance with JIS K7127, after curing with energy rays in Examples and Comparative Examples consisting only of an energy ray-curable adhesive without a base material (ultraviolet irradiation (irradiation conditions: illuminance 350 mW / cm ² , light intensity A test piece having a width of 15 mm, a thickness of 0.2 mm, and a total length of 150 mm (a distance between chucks of 100 mm) was prepared from an energy ray-curable pressure-sensitive adhesive of 200 mJ / cm ² ), and a breaking stress (MPa) as tensile physical properties and The elongation at break (%) was measured.

Adhesive residue: After evaluating the unevenness of the circuit surface to be described later, the wafer thickness is ground to 100 μm using a wafer back surface grinding device (DGP-8760, manufactured by DISCO Corporation), and then with an ultraviolet irradiation / tape peeling device. The adhesive sheet surface was irradiated with ultraviolet rays (irradiation conditions: illuminance: 350 mW / cm ² , light amount: 200 mJ / cm ² ) as an energy ray using a tape mounter (Rintech Co., RAD-2700F / 12). Furthermore, a transfer tape (manufactured by Lintec, Adwill D-175) was attached to the ground surface of the wafer, and the adhesive sheet was peeled off from the circuit surface of the wafer. The exposed uneven circuit surface was observed at a magnification of 2000 using a microscope (manufactured by KEYENCE, digital microscope VHX-200) to evaluate the presence or absence of foreign matter and adhesive residue.
(Double-circle): The adhesive residue was not recognized.
○: The amount of the adhesive residue was small, and it was at a level that could be put to practical use as an adhesive sheet.
(Triangle | delta): The quantity of the adhesive residue was a little large.
X: The amount of the adhesive residue was large.

  Concavity and convexity followability: 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 adhesive sheets of Examples and Comparative Examples were attached to the circuit surface of the dummy wafer using a tape laminator (RADTEC RAD-3500F / 12). Using a microscope (manufactured by Keyence, digital microscope VHX-200), the circuit pattern surface is observed at a magnification of 2000 times through the base material, and follow-up is performed when there is no air (bubbles) in the vicinity of the step in the observation area. Existence (◯), and when there was contamination, it was evaluated as no followability (×).

  About compatibility, the energy ray hardening-type adhesive of Examples 1-12 and Comparative Examples 1 and 2 is superior to Comparative Examples 3-6 as it is clear from Table 2. This is because the visual evaluation result is excellent and the haze value is small. Therefore, it can be said that Examples 1 to 12 and the like are excellent in compatibility between the energy ray curable urethane acrylate and the energy ray curable acrylic copolymer. . In Examples 1 to 12 and the like, PPG and PEG, which are polyol components similar to each other, are adopted (see Table 1), and isophorone diisocyanate (IPDI) is used as an isocyanate unit for forming an energy ray-curable urethane acrylate. ) (See Table 1).

  In all of Examples 1 to 12, the storage elastic modulus G ′ at 25 ° C. is 0.15 MPa or less, and the value of tan δ is 0.2 or more (see Table 2). It can be said that it has elasticity, adhesive strength before curing, and irregularity followability.

  Furthermore, as is clear from Table 2, the energy ray-curable pressure-sensitive adhesives of Examples 1 to 12 are excellent in tensile physical properties after energy ray curing. This is because the rupture stress of the energy beam curable pressure-sensitive adhesive layer in the state after energy beam curing is 10 MPa or more and the rupture elongation is 15% or more, which is larger than these values in Comparative Examples 3 to 6. Hereinafter, the difference in breaking stress and breaking elongation between Examples 1 to 12 will be described.

  FIG. 1 is a graph showing the relationship between the proportion of polypropylene glycol (PPG) in the polyol contained in the energy beam curable urethane acrylate of the example and the breaking stress (MPa) of the energy beam curable adhesive. FIG. 2 is a graph showing the relationship between the proportion of polypropylene glycol (PPG) in the polyol contained in the energy ray-curable urethane acrylate of the example and the breaking elongation (%) of the energy ray-curable pressure-sensitive adhesive layer.

  When the content of PPG in the polyol is 10 to 90 mol%, that is, when PPG and PEG are copolymerized within a molar ratio of 9: 1 to 1: 9 (Examples 1 to 12) Table 1), when only one of them is used (see Comparative Examples 1 and 2 and Table 1), the values of breaking stress (MPa) and breaking elongation (%) tend to be higher. This is considered to be an effect of appropriately combining PEG having high crystallinity with PPG having branching and low crystallinity because it does not have a branched chain.

  1 and 2, when the molar ratio of PPG to PEG is approximately 9: 1 to 1: 4, that is, when the content of PPG is 20 to 90 mol% (Example 1). -5, 7-11, see Table 1), breaking stress (MPa) and elongation at break (%) tend to be large. In particular, when the molar ratio of PPG to PEG is 4: 1 to 3: 2, (Examples 1, 3, 4, 7, 9, 10), that is, the content of PPG is 60 to 80 mol%. In this case, the breaking stress (MPa) and the breaking elongation (%) are large values. Among them, the molar ratio of PPG to PEG is in the range of 7.5: 2.5 to 6.5: 3.5, particularly 7: 3 (see Examples 1 and 7 and Table 1). The breaking stress (MPa) and the breaking elongation (%) are close to the maximum values. For this reason, it can be said that the energy ray-curable pressure-sensitive adhesive using PPG and PEG in combination at this molar ratio is particularly excellent in tensile properties.

  As for the result of the adhesive residue, Examples 1 and 7 are particularly excellent (see Table 2). This is presumably because these examples all have excellent compatibility with the energy ray-curable pressure-sensitive adhesive and also have good tensile properties. That is, when the adhesive sheet of these examples having excellent tensile properties is peeled off from the circuit surface of the wafer, it is prevented that a part of the energy ray curable adhesive layer breaks and remains as a residue on the wafer. This is because it can.

  As described above, according to the present embodiment, by using PPG and PEG in combination for forming a polyol unit contained in the energy ray curable urethane acrylate, unevenness followability with respect to the wafer circuit surface and the like, It is possible to realize a pressure-sensitive adhesive sheet that is excellent in compatibility and the like, has good tensile properties, and does not generate a pressure-sensitive adhesive residue.

The material of each member which comprises an adhesive sheet is not limited to what was illustrated in this embodiment. For example, the polyol unit may be formed by copolymerizing a polyol having a structure similar to each of PPG and PEG at a preferable ratio as described above. Alternatively, it may be formed by copolymerization of PPG and PEG used at a preferred ratio with other polyols shown in, for example, paragraph [0027]. Moreover, the use of the adhesive sheet is not limited to the protection of the semiconductor wafer during processing by the pre-dicing (DBG) process, but the protection of the semiconductor wafer in the conventional processing method or the surface of parts other than the semiconductor wafer is protected. Can also be used.

It is a graph which shows the relationship between the ratio of the polypropylene glycol (PPG) in a polyol, and breaking stress (MPa) in an Example. It is a graph which shows the relationship between the ratio of the polypropylene glycol (PPG) in a polyol, and breaking elongation (%) in an Example.

Claims (5)

An adhesive sheet in which an energy beam curable pressure-sensitive adhesive layer is formed on a substrate, wherein the energy beam curable pressure-sensitive adhesive layer has an energy beam curable acrylic copolymer having an unsaturated group in a side chain, and energy Wire curable urethane acrylate,
The energy ray curable urethane acrylate is
A pressure-sensitive adhesive sheet, which is a compound having an isocyanate unit, a polyol unit containing two or more kinds of polyols, and a (meth) acryloyl group.   The pressure-sensitive adhesive sheet according to claim 1, wherein the polyol contains polypropylene glycol and polyethylene glycol.   The pressure-sensitive adhesive sheet according to claim 2, wherein a molar ratio of the polypropylene glycol and the polyethylene glycol is within a range of 9: 1 to 1: 9.   The pressure-sensitive adhesive sheet according to claim 3, wherein a molar ratio of the polypropylene glycol to the polyethylene glycol is 9: 1 to 1: 4.   The pressure-sensitive adhesive according to any one of claims 1 to 4, wherein the energy beam-curable pressure-sensitive adhesive layer in a state after energy beam curing has a breaking stress of 10 MPa or more and a breaking elongation of 15% or more. Sheet.

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