JP2013159692A - Sheet and self-adhesive sheet obtained by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet obtained by curing an energy ray-curable composition containing urethane acrylate oligomers and a compound having a thiol group in one molecule thereof, to provide a self-adhesive sheet obtained by using the sheet as a constituent layer, and to improve preservation stability of raw materials of the sheet.SOLUTION: The sheet comprises a cured product obtained by curing a blended product, which contains urethane (meth)acrylate oligomers, the compound having the thiol group in one molecule thereof and an N-nitrosoamine-based polymerization inhibitor and/or an N-oxyl compound-based polymerization inhibitor, by using an energy ray.

Description

  The present invention relates to a sheet used as a constituent layer of a base material of a surface protective pressure-sensitive adhesive sheet preferably used for protecting a circuit surface of a semiconductor wafer having a circuit formed on the surface, and in particular, a difference in height on the circuit surface. The present invention relates to a sheet preferably used as an intermediate layer of an adhesive sheet for surface protection of a semiconductor wafer on which large bumps are formed. The present invention also relates to a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer on a base material comprising the sheet as a constituent layer and preferably used as a surface-protective pressure-sensitive adhesive sheet for semiconductor wafers.

  As information terminal devices are rapidly becoming thinner, smaller, and multifunctional, semiconductor devices mounted on them are also required to be thinner and denser. In order to reduce the thickness of an apparatus, it is desired to reduce the thickness of a semiconductor wafer on which semiconductors are integrated. In addition, with the increase in circuit density, there is a need for further improvement in semiconductor chip mounting technology in which spherical bumps made of solder, etc., having a diameter of about several hundred μm, which are used for joining semiconductor chips and substrates, are mounted on the circuit surface. Yes. Usually, the bumps are bonded to the semiconductor wafer at a high density in advance. When the back surface of such a wafer with bumps is ground, the pressure difference caused by the difference in height between the portion where the bumps are present and the portion where the bumps are not present directly affects the back surface of the wafer. Will eventually break the semiconductor wafer.

  Therefore, Patent Document 1 (Japanese Patent Laid-Open No. 11-343469) discloses a surface protective pressure-sensitive adhesive sheet for backside processing, in which a pressure-sensitive adhesive layer is provided on a base material having a predetermined viscoelastic property obtained by polymerizing a urethane acrylate oligomer. Is disclosed. In the surface protective pressure-sensitive adhesive sheet having such a base material, the base material follows the irregularities on the surface of the adherend, so that dimples and cracks are not easily generated.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2011-68727) discloses a sheet formed by curing an energy ray curable composition containing a urethane acrylate oligomer and a compound having a thiol group in the molecule. . By curing this energy beam curable composition, it is possible to provide an inexpensive sheet that can suppress outgassing and a pressure-sensitive adhesive sheet using the sheet even when used in a semiconductor device manufacturing process involving heating.

  Moreover, back surface grinding may be performed in a state where the circuit surface is protected by the surface protection sheet, and further, back surface processing such as etching may be performed. During such back surface processing, the wafer often generates heat or is heated. For this reason, at the time of back surface processing, a surface protection sheet may be heated and outgas may be generated. Therefore, it is considered to use a sheet having excellent heat resistance disclosed in Patent Document 2 and capable of suppressing the generation of outgas as a constituent layer of the adhesive sheet for holding and protecting a wafer disclosed in Patent Document 1.

  By the way, in the surface protection of the wafer whose bumps are increased in size and densified as described above, the unevenness followability of the base material may be insufficient, and the surface protection sheet between the base material and the adhesive layer may be insufficient. In addition, it has been proposed to provide an intermediate layer for absorbing and mitigating bump height differences. For example, Patent Document 3 (Japanese Patent Laid-Open No. 2001-203255) is an adhesive sheet for protecting a semiconductor by being attached to a semiconductor wafer surface, and an intermediate layer is provided on one side of a base material layer. A pressure-sensitive adhesive sheet for holding and protecting a semiconductor wafer is disclosed in which a pressure-sensitive adhesive layer is formed on the surface. According to the present invention, it becomes possible to follow the unevenness of the wafer surface well by appropriate deformation of the intermediate layer and the pressure-sensitive adhesive layer, and as a result, it is possible to prevent water intrusion and wafer cracking during wafer back surface processing.

Japanese Patent Laid-Open No. 11-343469 JP 2011-68727 A JP 2001-203255 A

  However, the energy beam curable composition for preparing the sheet described in Patent Document 2 is not sufficiently stable in storage, and a part of the compound containing a thiol group in the molecule may be deactivated. is there. This invention is made | formed in view of the above prior arts, and the sheet | seat formed by hardening | curing the energy-beam curable composition containing a urethane acrylate oligomer and the compound which has a thiol group in a molecule | numerator is obtained. The pressure-sensitive adhesive sheet used as the constituent layer is intended to improve the storage stability of the sheet raw material. Another object of the present invention is to provide a pressure-sensitive adhesive sheet that exhibits an excellent function as an intermediate layer for embedding irregularities in the sheet.

The present invention for solving the above problems includes the following gist.
[1] Curing obtained by energy ray curing of a composition containing a urethane (meth) acrylate oligomer, a compound having a thiol group in the molecule, and an N-nitrosamine polymerization inhibitor and / or an N-oxyl polymerization inhibitor A sheet consisting of things.

[2] The content of the N-nitrosamine polymerization inhibitor and / or N-oxyl polymerization inhibitor in the blend is 0.5 to 5 g with respect to 100 g of the compound having a thiol group in the molecule. 1].

[3] A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer on a substrate composed of the sheet according to the above [1] or [2] and a sheet made of a thermoplastic resin.

[4] A method for processing a semiconductor wafer, comprising attaching a circuit surface of a semiconductor wafer having a circuit formed on the surface thereof to the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to [3], and grinding the back surface of the semiconductor wafer.

[5] forming a groove having a depth of cut shallower than the wafer thickness from the surface of the semiconductor wafer on which a circuit having bumps is formed;
Affixing the adhesive sheet according to [3] on the circuit forming surface,
Then, the semiconductor wafer manufacturing method includes a step of reducing the thickness of the wafer by grinding the back surface of the semiconductor wafer, and finally dividing the wafer into individual chips and picking up the chips.

  According to this invention, since the special polymerization inhibitor is mix | blended with the raw material of the sheet | seat which can be used as a structural layer of a surface protection sheet, there is little deterioration of a raw material and it is excellent in storage stability. In addition, because of the presence of the compound having a thiol group, the flexibility of the sheet is high, and deterioration of the raw material during storage is suppressed, so even a sheet prepared after long-term storage in the raw material state, High flexibility. Therefore, according to the surface protection sheet containing such a sheet as an intermediate layer, excellent back surface grinding suitability can be realized.

  Hereinafter, the present invention will be described more specifically, including its best mode. The sheet according to the present invention comprises a urethane (meth) acrylate oligomer, a compound having a thiol group in the molecule (hereinafter also referred to as “thiol group-containing compound”), an N-nitrosamine polymerization inhibitor and / or an N-oxyl polymerization. It consists of the hardened | cured material which hardened the formulation containing an inhibitor with energy rays. Such a sheet of the invention is excellent in the storage stability of the raw material, and the outgassing suppression effect when made into a sheet is easily maintained even after being prepared after storage of the raw material, and the thermoplastic resin layer and the adhesive layer described later It is particularly preferably used as an intermediate layer of a pressure-sensitive adhesive sheet for protecting the surface.

[Sheet (energy ray hardened layer)]
The sheet of the present invention comprises a urethane (meth) acrylate oligomer, a thiol group-containing compound, an N-nitrosamine polymerization inhibitor and / or an N-oxyl polymerization inhibitor, and an energy ray-curable monomer as necessary. Is a cured product obtained by curing with energy rays. Hereinafter, the sheet of the present invention may be particularly referred to as an “energy ray cured layer”.

  The urethane (meth) acrylate oligomer is a compound having a (meth) acryloyl group and having a urethane bond. Such a urethane (meth) acrylate oligomer can be obtained by reacting a (meth) acrylate having a hydroxyl group with a terminal isocyanate urethane prepolymer obtained by reacting a polyol compound and a polyvalent isocyanate compound. In addition, in this specification, (meth) acryl is used in the meaning including both acryl and methacryl.

  The polyol compound is not particularly limited as long as it is a compound having two or more hydroxy groups, and known compounds can be used. Specifically, for example, any of alkylene diol, polyether type polyol, polyester type polyol, and polycarbonate type polyol may be used, but a better effect can be obtained by using the polyether type polyol. The polyol is not particularly limited, and may be a bifunctional diol, a trifunctional triol, or a tetrafunctional or higher polyol. From the viewpoint of availability, versatility, and reactivity, It is particularly preferred to use a diol. Among these, polyether type diol is preferably used.

  A polyether type diol, which is a typical example of a polyether type polyol, is generally represented by HO — (— R—O—) n—H. Here, R is a divalent hydrocarbon group, preferably an alkylene group, more preferably an alkylene group having 1 to 6 carbon atoms, and particularly preferably an alkylene group having 2 or 3 carbon atoms. Among the alkylene groups having 1 to 6 carbon atoms, ethylene, propylene, or tetramethylene is preferable, and ethylene or propylene is particularly preferable. Therefore, particularly preferred polyether type diols include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and more particularly preferred polyether type diols include polyethylene glycol and polypropylene glycol. n is the number of repetitions of R, preferably about 10 to 250, more preferably about 25 to 205, and particularly preferably about 40 to 185. When n is smaller than 10, the urethane bond concentration of the urethane (meth) acrylate oligomer increases, the elasticity of the cured product increases, and the compressive stress of the pressure-sensitive adhesive sheet described later increases. When n is larger than 250, there is a concern that the compressive stress is hardly lowered.

  A terminal isocyanate urethane prepolymer having an ether bond (-(-R-O-) n-) introduced therein is produced by the reaction between the polyether-type diol and the polyvalent isocyanate compound. By using such a polyether type diol, the urethane (meth) acrylate oligomer contains a structural unit derived from the polyether type diol.

  The polyester type polyol is obtained by polycondensation of a polyol compound and a polybasic acid component. Examples of the polyol compound include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3 -Methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, hexanediol, octanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2- Examples thereof include various known glycols such as butyl-1,3-propanediol, 1,4-cyclohexanedimethanol, and bisphenol A ethylene glycol or propylene glycol adduct. As the polybasic acid component used for the production of the polyester type polyol, various known ones generally known as polyester polybasic acid components can be used. Specifically, for example, dibasic acids such as adipic acid, maleic acid, succinic acid, oxalic acid, fumaric acid, malonic acid, glutaric acid, pimelic acid, azelaic acid, sebacic acid and suberic acid, aromatic polybasic acids And the corresponding anhydrides and derivatives thereof, dimer acid, hydrogenated dimer acid and the like. In addition, in order to provide moderate hardness to a coating film, it is preferable to use an aromatic polybasic acid. Examples of the aromatic polybasic acid include dibasic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, and 2,6-naphthalenedicarboxylic acid, polybasic acids such as trimellitic acid and pyromellitic acid, and the like. And corresponding acid anhydrides and derivatives thereof. In addition, you may use various well-known catalysts for the said esterification reaction as needed. Examples of the catalyst include tin compounds such as dibutyltin oxide and stannous octylate, and alkoxytitanium such as tetrabutyl titanate and tetrapropyl titanate.

  It does not specifically limit as a polycarbonate type polyol, A well-known thing can be used. Specifically, for example, a reaction product of the above-described glycols and alkylene carbonate can be used.

  The molecular weight of the polyol compound is preferably about 1000 to 10,000, and more preferably about 2000 to 9000. When molecular weight is lower than 1000, the urethane bond density | concentration of a urethane (meth) acrylate oligomer will become high, and the compressive stress of the adhesive sheet mentioned later may become high. If the molecular weight is too high, the compressive stress may be difficult to decrease.

  The molecular weight of the polyol compound is polyol functional group number × 56.11 × 1000 / hydroxyl value [mgKOH / g], and is calculated from the hydroxyl value of the polyol compound.

  Examples of the polyvalent isocyanate compound include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate, isophorone diisocyanate, norbornane diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, and dicyclohexylmethane-2,4. Aliphatic diisocyanates such as' -diisocyanate, ω, ω'-diisocyanate dimethylcyclohexane, 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, tetramethylene xylylene diisocyanate, naphthalene-1, And aromatic diisocyanates such as 5-diisocyanate. Among these, it is preferable to use isophorone diisocyanate, hexamethylene diisocyanate, or xylylene diisocyanate because the viscosity of the urethane (meth) acrylate oligomer can be kept low and the handleability becomes good.

  The terminal isocyanate urethane prepolymer obtained by reacting the above polyol compound and the polyvalent isocyanate compound is reacted with a (meth) acrylate having a hydroxy group to obtain a urethane (meth) acrylate oligomer.

  The (meth) acrylate having a hydroxy group is not particularly limited as long as it is a compound having a hydroxy group and a (meth) acryloyl group in one molecule, and known ones can be used. Specifically, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 4-hydroxycyclohexyl (meth) acrylate, 5-hydroxycyclooctyl (meta ) Acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, pentaerythritol tri (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate and other hydroxyalkyl (meth) acrylates, N -Reaction products obtained by reacting (meth) acrylic acid with diglycidyl ester of hydroxy group-containing (meth) acrylamide such as methylol (meth) acrylamide and bisphenol A And the like.

  As conditions for reacting the terminal isocyanate urethane prepolymer and the hydroxy group-containing (meth) acrylate, the terminal isocyanate urethane prepolymer and the hydroxy group-containing (meth) acrylate may be reacted in the presence of a solvent and a catalyst, if necessary. The reaction may be performed at about 60 to 100 ° C. for about 1 to 4 hours.

  The weight average molecular weight of the urethane (meth) acrylate oligomer thus obtained (referred to as polystyrene equivalent by gel permeation chromatography, hereinafter the same) is not particularly limited, but the weight average molecular weight is usually 1000 to 1000. It is preferable to set it as about 100,000, and it is more preferable to set it as 2000-80000. By setting the weight average molecular weight to 1000 or more, the breaking elongation of the energy ray cured layer can be improved, and by setting the weight average molecular weight to 100000 or less, the viscosity of the urethane (meth) acrylate oligomer can be lowered. The handling property of the coating liquid for use is improved.

  The obtained urethane (meth) acrylate oligomer has a photopolymerizable double bond in the molecule, and has a property of being polymerized and cured by irradiation with energy rays to form a film. Said urethane (meth) acrylate oligomer can be used individually by 1 type or in combination of 2 or more types.

  As a thiol group containing compound, if it is a compound which has at least 1 thiol group in a molecule | numerator, it will not specifically limit and a well-known thing can be used. Specifically, for example, nonyl mercaptan, 1-dodecanethiol, 1,2-ethanedithiol, 1,3-propanedithiol, triazinethiol, triazinedithiol, triazinetrithiol, 1,2,3-propanetrithiol, tetra Ethylene glycol-bis (3-mercaptopropionate), trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptopropionate), pentaerythritol tetrakisthioglucorate, dipentaerythritol hexakis (3-mercaptopropionate), tris [(3-mercaptopropionyloxy) -ethyl] -isocyanurate, 1,4-bis (3-mercaptobutyryloxy) butane, pentaerythritol Lakis (3-mercaptobutyrate), 1,3,5-tris (3-mercaptobutyloxyethyl) -1,3,5-triazine-2,4,6- (1H, 3H, 5H) -trione, etc. Can be mentioned.

  The content of the thiol group-containing compound is preferably 2 mmol or more, more preferably 3 to 100 mmol, and particularly preferably 4 to 85 mmol with respect to 100 g (solid content) of the urethane (meth) acrylate oligomer. By setting the content of the thiol group-containing compound to 2 mmol or more, an effect of suppressing outgas generation occurs in the energy ray cured layer. Furthermore, the energy ray cured layer exhibits specific viscoelasticity as described later, and has a high bump. The height difference of the wafer surface can be sufficiently relaxed. On the other hand, when the amount of the thiol group-containing compound is excessive, the elastic modulus of the energy ray-cured layer is remarkably lowered, and when the pressure-sensitive adhesive sheet using the base material is wound into a roll shape, The constituent resin may ooze out, and long-term storage in a roll form may be difficult. By setting the content of the thiol group-containing compound to 100 mmol or less, it is possible to suppress the compound from remaining as an uncured product, and to prevent the resin from bleeding from the end of the roll.

  The molecular weight of the thiol group-containing compound is preferably 200 to 3000, and more preferably 300 to 2000. When the molecular weight of the thiol group-containing compound exceeds 3000, the compatibility with the urethane (meth) acrylate oligomer is lowered, and the film forming property of the energy ray cured layer may be lowered.

  The energy ray curable resin composition composed of the urethane (meth) acrylate oligomer and the thiol group-containing compound as described above is unstable (thiol group-containing) due to the thermal addition reaction of thiol groups and double bonds. Reduction of the chain transfer action of compounds and generation of aggregates is a major issue. For this reason, the storage stability is usually poor, and there is a difference in the outgassing suppression effect or the physical properties of the cured energy beam cured immediately after compounding and the cured energy beam cured after long-term storage of the compound. There is a problem.

  Therefore, in the present invention, this storage stability is improved by further blending an N-nitrosamine polymerization inhibitor and / or an N-oxyl polymerization inhibitor.

  Specific examples of the N-nitrosamine polymerization inhibitor include N-nitrosophenylhydroxylamine ammonium salt and N-nitrosophenylhydroxylamine aluminum salt.

  Specific examples of the N-oxyl polymerization inhibitor include 2,2,6,6-tetramethyl-4-hydroxypiperazine-1-oxyl, bis (1-oxyl-2,2,6,6-tetra Methyl-4-piperidyl) sebacate, bis (1-oxyl-2,2,6,6-tetramethyl-4-piperidyl) terephthalate, bis (1-oxyl-2,2,6,6-tetramethyl-4- Piperidyl) phthalate, tetra (1-oxyl-2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate and the like.

  The content of the N-nitrosamine polymerization inhibitor and / or the N-oxyl polymerization inhibitor is preferably 0.5 to 5 g, particularly preferably 1 to 2 g with respect to 100 g of the thiol group-containing compound. By setting the content of the N-nitrosamine polymerization inhibitor and / or N-oxyl polymerization inhibitor to 0.5 g or more with respect to the thiol group-containing compound, the stability of the energy beam curable composition is improved, The effect of suppressing outgas generation is maintained between the cured energy beam immediately after blending and the cured energy beam after long-term storage after blending, or the difference in physical properties of the cured energy beam is not observed before and after storage. On the other hand, if the amount of the N-nitrosamine polymerization inhibitor and / or the N-oxyl polymerization inhibitor is excessive, the curability of the energy beam curable composition is remarkably lowered, and a large amount of energy is required to obtain a cured product. Irradiation is required, resulting in decreased productivity. In addition, when the produced pressure-sensitive adhesive sheet is rolled up and stored for a long time (for example, about one week), the constituent resin of the energy ray cured layer may ooze out from the end of the roll.

  In the blended composition of the urethane (meth) acrylate oligomer, the thiol group-containing compound, and the N-nitrosamine polymerization inhibitor and / or the N-oxyl polymerization inhibitor as described above, film formation is difficult due to high viscosity. There are many cases. For this reason, normally, an energy ray polymerizable monomer is mixed to lower the viscosity. After film-forming such a compounding composition, this is hardened and an energy ray hardening layer is obtained. The energy ray curable monomer has an energy ray polymerizable double bond in the molecule, and particularly in the present invention, an acrylate ester compound having a relatively bulky group is preferably used.

  Specific examples of energy ray curable monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) acrylate. , T-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meta ) Acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, eikoshi (Meth) acrylates such as (meth) acrylates having 1 to 30 carbon atoms in the alkyl group; isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxy (meta ) (Meth) acrylate having an alicyclic structure such as acrylate, cyclohexyl (meth) acrylate, adamantane (meth) acrylate, etc .; (meth) having an aromatic structure such as phenylhydroxypropyl (meth) acrylate or benzyl (meth) acrylate Acrylate, or (meth) acrylate having a heterocyclic structure such as tetrahydrofurfuryl (meth) acrylate, morpholine (meth) acrylate, styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl Ethers, N- vinylformamide, vinyl compounds such as N- vinyl pyrrolidone or N- vinyl caprolactam. Moreover, you may use polyfunctional (meth) acrylate as needed.

  Among these, from the point of compatibility with urethane (meth) acrylate oligomer, (meth) acrylate having an alicyclic structure having a relatively bulky group, (meth) acrylate having an aromatic structure, and heterocyclic structure (Meth) acrylate having

  10-500 weight part is preferable with respect to 100 weight part (solid content) of a urethane (meth) acrylate oligomer, and, as for the usage-amount of this energy-beam curable monomer, 30-300 weight part is more preferable.

As the film forming method, a technique called casting film formation (cast film formation) can be preferably employed. Specifically, a liquid compound (a liquid product obtained by diluting a mixture of the above components with a solvent if necessary) is cast into a thin film on a process sheet, for example, and then the coating film is irradiated with energy rays for polymerization. Cured to form a film. According to such a manufacturing method, the stress applied to the resin during film formation is small, and the formation of fish eyes is small. Moreover, the uniformity of the film thickness is also high, and the thickness accuracy is usually within 2%. Specifically, ultraviolet rays, electron beams, etc. are used as the energy rays. Further, the irradiation amount is different depending on the type of the energy ray, for example, when ultraviolet rays are used, the ultraviolet intensity is 50~300mW / cm ^2, the amount of ultraviolet irradiation is preferably about 100~1200mJ / cm ^2.

  When performing cast film formation, it is preferable that the viscosity of the film-forming coating solution is 10,000 mPa · s or less. By adjusting to such a range, it is easy to perform cast film formation with normal coating equipment such as a knife coater or a slot die. The viscosity of the coating solution for film formation can be measured, for example, with an E-type viscometer. The viscosity of the coating solution for film formation is more preferably 1000 to 7000 mPa · s.

  When ultraviolet rays are used as energy rays, a photopolymerization initiator is blended in the blend. Examples of such photopolymerization initiators include photoinitiators such as benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, and peroxide compounds, and photosensitizers such as amines and quinones. Specific examples include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether.

  The amount of the photopolymerization initiator used is preferably 0.05 to 15 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the total of the urethane (meth) acrylate oligomer and the energy ray curable monomer. Parts, particularly preferably 0.3 to 5 parts by weight.

  Moreover, you may add metal fillers, such as inorganic fillers, such as a calcium carbonate, a silica, and a mica, iron, and lead, in the above-mentioned compound. In addition to the above components, the sheet may contain additives such as colorants such as pigments and dyes.

  It can be evaluated as follows that the above-mentioned formulation is suitable for long-term storage. That is, outgas generation between the energy ray cured layer formed using the formulation immediately after adjustment and the energy ray cured layer formed by the formulation that has been stored for a period corresponding to a normally assumed storage period such as several months Compare the physical properties and confirm that the change is small. However, since it is not efficient to take such a long period of time for the test, a measure is taken to promote the change over time of the formulation by storing it in a high temperature environment (heat storage). Such heat storage is performed under conditions such as storage at 80 ° C. for 500 hours.

  The sheet | seat (energy-beam cured layer) of this invention is preferably used as a sheet | seat with an adhesive by providing the layer which consists of an adhesive in any one surface. When such a sheet with an adhesive is used as an adhesive sheet for semiconductor processing, even if it is used in a process involving heating, outgas is unlikely to occur. Moreover, the effect is not easily lost even in the sheet with the pressure-sensitive adhesive prepared after the raw material is stored for a long time.

  The energy ray hardened layer is provided between a thermoplastic resin layer and an adhesive layer, which will be described later, and is particularly preferably used as a constituent layer of a surface protective sheet during back grinding of a high bump wafer.

  The resulting energy ray cured layer exhibits unique viscoelasticity, and when the bumps formed on the wafer surface are pressed, it deforms quickly according to the shape of the bumps, and relieves pressure caused by the bump height difference. Even if the bump is pressed, the bump will not be crushed. Further, since the residual stress after deformation is small, the wafer can be stably held and the occurrence of dimples and cracks can be suppressed. Moreover, the effect is not easily lost even in the sheet with the pressure-sensitive adhesive prepared after the raw material is stored for a long time.

  The torsional storage elastic modulus of the energy ray cured layer is preferably in the range of 0.1 to 6 MPa, more preferably 0.3 to 3 MPa, and particularly preferably 0.5 to 2 MPa. When the twist storage elastic modulus is in the above range, the energy ray cured layer can prevent the bumps from being crushed and the dimples to be generated when used as a constituent layer of the pressure-sensitive adhesive sheet.

  The compressive stress of the pressure-sensitive adhesive sheet described later can be adjusted to a desired range by using the thickness of the energy ray cured layer or a specific urethane (meth) acrylate oligomer and a thiol group-containing compound. The thickness of the energy ray cured layer is not particularly limited, but is preferably 10 to 2000 μm, more preferably 20 to 1000 μm, and particularly preferably 50 to 500 μm.

  The energy ray curable layer of the present invention is preferably used for obtaining a pressure sensitive adhesive sheet having a pressure sensitive adhesive layer on a base material composed of the energy ray curable layer and a sheet made of a thermoplastic resin (thermoplastic resin layer). It is done.

[Thermoplastic resin layer]
As the thermoplastic resin layer, 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) ), Thermoplastic resins such as polyvinylidene chloride resins, polyamide resins, polyurethane resins, polystyrene resins, acrylic resins, fluorine resins, cellulose resins, and polycarbonate resins. These thermoplastic resins can be used as a single layer or a multilayer product by laminating. The thermoplastic resin layer is used when there is a possibility of irradiating the compound containing the energy beam curable monomer via the thermoplastic resin layer with an energy beam, as in an example of the substrate manufacturing method described later. Those that are permeable to energy rays are preferred.

  The thermoplastic resin layer is formed on one side of the energy ray cured layer.

  Since the energy ray hardened layer is deformed relatively easily as described above, it is difficult to maintain the shape. Therefore, when the base material is formed only of the energy ray cured layer, handling properties may be poor and work efficiency may be reduced. By laminating a relatively hard thermoplastic resin layer on the energy ray cured layer, a substrate having an appropriate shape retention and excellent handling properties can be obtained.

  Although the thickness of a thermoplastic resin layer is not specifically limited, Preferably it is 10-1000 micrometers, More preferably, it exists in the range of 20-500 micrometers.

[Base material]
As described above, the base material of the pressure-sensitive adhesive sheet is formed by laminating the energy ray cured layer and the thermoplastic resin layer. The energy ray cured layer and the thermoplastic resin layer may be directly laminated, or may be bonded via an adhesive layer.

  The method for producing the substrate is not particularly limited. For example, first, the urethane (meth) acrylate oligomer, the thiol group-containing compound, the N-nitrosamine polymerization inhibitor and / or the N-oxyl polymerization inhibitor and the necessity Accordingly, a blend containing an energy ray curable monomer is cast into a thin film on a process sheet. Then, if necessary, the coating film is dried and irradiated with a small amount of energy rays to partially polymerize and cure the coating film. Furthermore, after laminating a thermoplastic resin layer on the coating film, it is obtained by irradiating energy rays to cure the coating film to obtain an energy beam cured layer and removing the process sheet.

  The pressure-sensitive adhesive sheet according to the present invention has a pressure-sensitive adhesive layer formed on one side of the substrate. In order to improve the adhesiveness with the pressure-sensitive adhesive layer, the surface of the substrate on which the pressure-sensitive adhesive layer is provided, preferably the surface of the energy ray cured layer, is subjected to corona treatment or a primer layer with an ethylene vinyl acetate copolymer or the like. May be provided.

[Adhesive layer]
The type of the pressure-sensitive adhesive layer is not specified as long as it has an appropriate removability to the wafer, and can be formed of various conventionally known pressure-sensitive adhesives. Such an adhesive is not limited at all, but an adhesive such as rubber-based, acrylic-based, silicone-based, or polyvinyl ether is used. In addition, an energy ray curable pressure-sensitive adhesive that is cured by irradiation with energy rays and becomes removable, a heat-foaming type, or a water swelling type pressure-sensitive adhesive can also be used.

  As the energy ray curable (ultraviolet ray curable, electron beam curable) pressure-sensitive adhesive, it is particularly preferable to use an ultraviolet curable pressure-sensitive adhesive. Specific examples of such energy beam curable pressure-sensitive adhesives are described in, for example, JP-A-60-196956 and JP-A-60-223139. Moreover, as a water swelling type adhesive, what is described, for example in Japanese Patent Publication No. 5-77284, Japanese Patent Publication No. 6-101455, etc. is used preferably.

  Although the thickness of an adhesive layer is not specifically limited, Preferably it is 5-200 micrometers, More preferably, it exists in the range of 10-120 micrometers.

  In addition, in order to protect an adhesive layer before the use, the peeling sheet may be laminated | stacked on the adhesive layer. The release sheet is not particularly limited, and a release sheet base material treated with a release agent can be used. Examples of the release sheet substrate include films made of resins such as polyethylene terephthalate, polybutylene terephthalate, polypropylene, and polyethylene, or foamed films thereof, and papers such as glassine paper, coated paper, and laminated paper. Examples of the release agent include release agents such as silicone-based, fluorine-based, and long-chain alkyl group-containing carbamates.

  The method of providing the pressure-sensitive adhesive layer on the surface of the substrate may be to transfer the pressure-sensitive adhesive layer formed by applying on the release sheet so as to have a predetermined film thickness to the surface of the substrate, or to apply directly to the surface of the substrate. A pressure-sensitive adhesive layer may be formed.

[Adhesive sheet]
The pressure-sensitive adhesive sheet according to the present invention has a pressure-sensitive adhesive layer formed on one side of the substrate. When the base material has a two-layer structure in which a thermoplastic resin layer is laminated on one side of the energy ray cured layer, the pressure-sensitive adhesive layer is preferably provided on the surface of the energy ray cured layer. The pressure-sensitive adhesive sheet according to the present invention can take any shape such as a tape shape and a label shape. Moreover, the pre-cut shape by which the adhesive sheet previously die-cut by the shape of the to-be-adhered body was hold | maintained on the peeling sheet may be sufficient. The pre-cut pressure-sensitive adhesive sheet is obtained by a so-called half-cut method in which, after an uncut pressure-sensitive adhesive sheet is provided on the release sheet, only the pressure-sensitive adhesive sheet is completely punched into the adherend shape and the release sheet is not completely cut. . At this time, in order to completely cut the pressure-sensitive adhesive sheet, it is preferable to cut slightly into the release sheet. However, if the release sheet is cut excessively, the strength is lowered and the operability is impaired. Therefore, the depth of cut into the release sheet is 30% or less, more preferably 20% or less of the total thickness of the release sheet.

  The peculiar viscoelasticity of the pressure-sensitive adhesive sheet can be easily evaluated by a compressive stress calculated from a load measured when a test piece having a predetermined-shaped bump is pushed into the pressure-sensitive adhesive sheet at a predetermined speed. Details of the measurement will be described later. The compressive stress at 23 ° C. of the pressure-sensitive adhesive sheet is preferably in the range of 0.05 to 1.0 MPa, more preferably 0.06 to 0.7 MPa, and particularly preferably 0.07 to 0.3 MPa. When the compressive stress is in the above range, the pressure-sensitive adhesive sheet exhibits viscoelasticity as described above, and can prevent the bumps from being crushed and the generation of dimples.

  The total thickness of the energy ray cured layer and the pressure-sensitive adhesive layer is appropriately selected in consideration of the bump height of the wafer surface to which the pressure-sensitive adhesive sheet is adhered, the bump shape, the pitch of the bump interval, and the like. The total thickness of the energy ray cured layer and the pressure-sensitive adhesive layer is desirably selected to be 110% or more, preferably 130 to 500% of the bump height. When the total thickness of the energy ray cured layer and the pressure-sensitive adhesive layer is selected in this manner, the pressure-sensitive adhesive sheet follows the unevenness on the circuit surface, and the unevenness difference can be eliminated. The bump height is the height from the flat surface of the circuit surface (portion where no bump is formed) to the top of the bump, and is defined by the arithmetic average of the heights of a plurality of bumps.

[Semiconductor wafer processing method]
The pressure-sensitive adhesive sheet of the present invention can be used for processing semiconductor wafers as described below.
(Wafer back grinding method)
In wafer backside grinding, an adhesive sheet is applied to the circuit surface of a semiconductor wafer having a circuit formed on the surface to protect the circuit surface and grind the backside of the wafer to obtain a wafer having a predetermined thickness.

  The semiconductor wafer may be a silicon wafer or a compound semiconductor wafer such as gallium / arsenic. Formation of a circuit on the wafer surface can be performed by various methods including conventionally used methods such as an etching method and a lift-off method. In the semiconductor wafer circuit forming step, a predetermined circuit is formed. The thickness of such a wafer before grinding is not particularly limited, but is usually about 500 to 1000 μm. The surface shape of the semiconductor wafer is not particularly limited, but the pressure-sensitive adhesive sheet of the present invention is preferably used for protecting the surface of a wafer having bumps formed on the circuit surface.

  The pressure-sensitive adhesive sheet of the present invention has the energy ray cured layer and the pressure-sensitive adhesive layer as described above, and has viscoelasticity that can sufficiently follow the bumps. For this reason, it is embedded in the wafer surface on which the bump is formed, the unevenness difference is eliminated, and the wafer can be held in a flat state. In addition, because of the high followability to the surface shape of the wafer, even if a strong shearing force is applied to the wafer when grinding the wafer back surface, the wafer can be prevented from vibrating and misaligned, and the wafer back surface can be ground to a flat and extremely thin thickness. Can do. Moreover, since a base material contains an energy ray hardening layer, even if a bump is pressed on a base material, a bump will not be crushed.

  The back surface grinding is performed by a known method using a grinder, a suction table for fixing the wafer, or the like with the adhesive sheet attached. After the back grinding process, a process of removing the crushed layer generated by grinding may be performed. The thickness of the semiconductor wafer after back grinding is not particularly limited, but is preferably 10 to 300 μm, and particularly preferably about 25 to 200 μm.

  After the back grinding process, the adhesive sheet is peeled off from the circuit surface. According to the pressure-sensitive adhesive sheet of the present invention, it is possible to securely hold the wafer during backside grinding of the wafer and to prevent cutting water from entering the circuit surface.

(Pre-dicing method)
Furthermore, the pressure-sensitive adhesive sheet of the present invention is preferably used in making a wafer with a high bump by a so-called tip dicing method, specifically,
A groove having a depth of cut shallower than the wafer thickness is formed from the surface of the semiconductor wafer on which a circuit having bumps is formed,
Affixing the adhesive sheet as a surface protective sheet on the circuit forming surface,
Then, the semiconductor wafer is preferably used in a semiconductor chip manufacturing method in which the thickness of the wafer is reduced by grinding the back surface of the semiconductor wafer and finally dividing into individual chips.
By using the pressure-sensitive adhesive sheet of the present invention, high adhesion can be obtained between the chip and the pressure-sensitive adhesive layer, so that there is no infiltration of grinding water into the circuit surface and chip contamination can be prevented.

  Thereafter, the chip is picked up by a predetermined method. In addition, prior to chip pickup, the chips in a wafer shape may be transferred to another pressure-sensitive adhesive sheet, and then chip pickup may be performed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. In the following examples and comparative examples, various physical properties were evaluated as follows.

(viscosity)
As a viscometer, an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., RE-85U) was used to measure the viscosity of the energy ray-curable composition at 25 ° C. and 10 rpm.

(Torsion storage elastic modulus)
An energy ray cured layer having a diameter of 8 mm and a thickness of 6 mm was prepared using a viscoelasticity measuring device (manufactured by Rheometrics, device name: DYNAMIC ANALYZER RDA II), and the torsional storage elastic modulus at 23 ° C. was measured at 1 Hz.

(Compressive stress)
A pressure-sensitive adhesive sheet composed of an energy ray cured layer, a thermoplastic resin layer and an acrylic pressure-sensitive adhesive layer is cut into a shape having a length of 15 mm × width of 15 mm, and is left to stand on a sample table of a universal tensile compression tester to be described later. remove. The bump forming surface (10 mm × 10 mm square) of a chip with bumps (bump height 250 μm, bump pitch 500 μm) made of a silicon wafer 10 mm long × 10 mm wide × 200 μm thick with respect to the adhesive layer surface exposed upward The whole was brought into contact with the surface of the energy ray cured layer from above, and was pushed to a depth of 140 μm at a speed of 0.6 mm / min with a universal tensile compression tester [Instron, product name “Instron 5581 type”]. At that time, a load (compressive load) applied to the silicon wafer chip from the adhesive sheet was measured. The measurement was performed in an environment of a temperature of 23 ° C. and a relative humidity of 50%. The compressive stress was calculated from the measured compressive load and the surface area of the pressed bump.
It was assumed that the bump diameter was 280 μm and the load when the bump was pushed in half was measured. The bump surface area (39.9 mm ² ) of the entire chip plane when 140 μm is pushed in is calculated from the surface area of one bump and the number of bumps (324), and the compressive stress is calculated from the following equation (1). .
Compressive stress = Compressive load / Bump surface area over the entire chip plane (1)

(Dimple and crack generation)
Solder bumped wafer (8 inch silicon wafer with chip size 10mm x 10mm wide, 8mm silicon wafer, bump height 250μm, bump pitch 500μm, total thickness 720μm) is affixed to adhesive sheet, fixed and ground to 250μm thickness After that (using a grinder DGP8760 manufactured by DISCO Corporation), the back surface of the wafer was visually observed to confirm whether dimples were generated in the portion corresponding to the bumps on the back surface of the wafer. The case where no dimples were generated was designated as A, the case where slight dimples were confirmed to be produced but B which was not practically problematic was designated as C, and the case where obvious dimples were produced was designated as C.
Also, the presence or absence of wafer cracks (wafer cracks) was visually confirmed.

(Difference in height)
Adhesive sheet is affixed to a bumped wafer with a bump height of 250 μm using Lintec's laminator “RAD3510”. Immediately after that, the total thickness of the portion with bumps is measured with TECKLOCK's constant pressure thickness measuring instrument: PG-02. “A” (distance from the back surface of the wafer to the base material surface of the adhesive sheet) and the total thickness “B” of the portion without the bump were measured, and “A−B” was calculated as the height difference. It means that the unevenness | corrugation resulting from bump height is eased by the adhesive sheet, so that a height difference is small.

(Infiltration of grinding water)
After sticking the adhesive sheet on the wafer surface, the wafer back surface is ground to a total thickness of 250 μm while spraying water, the adhesive sheet is peeled off from the wafer surface, and the presence or absence of intrusion of grinding water into the wafer surface is checked with an optical digital microscope (magnification 100) Times).

(Embeddability)
An adhesive sheet was attached to the circuit surface of the wafer with bumps using a Rintec Co., Ltd. laminator “RAD3510”. Immediately after that, it was observed with an optical digital microscope (magnification 300 times), and the embedding distance between the bumps was measured. The embedding distance between the bumps is defined as follows.

  Four adjacent bump tops are connected by a straight line to create a virtual square. The square diagonal is measured, and the bump diameter is subtracted from the diagonal length to obtain the bump interval. The distance at which the pressure-sensitive adhesive layer and the wafer surface are in close contact with each other on the diagonal line is measured and used as the embedding distance between bumps.

  (Embedding distance / bump interval) × 100 is calculated and set as embeddability (%). The embedding property is an index of the adhesiveness of the adhesive sheet with respect to the gap between the bumps. The higher the embedding property, the more closely the adhesive sheet and the bumped wafer are in close contact with each other. When the embedding property is low, it means that the adhesion of the adhesive sheet is insufficient at the base portion of the bump.

Example 1
The terminal isocyanate urethane prepolymer obtained by polymerizing polypropylene glycol having a molecular weight of 8000 and isophorone diisocyanate (hereinafter referred to as IPDI) is reacted with 2-hydroxyethyl methacrylate (hereinafter referred to as HEMA) to give a weight average molecular weight of 55,000. A polyether polyol urethane (meth) acrylate oligomer was obtained. The weight average molecular weight was measured using a commercially available molecular weight measuring instrument (main product name “HLC-8220GPC”, manufactured by Tosoh Corporation; column product name “TSKGel SuperHZM-M”, manufactured by Tosoh Corporation; developing solvent tetrahydrofuran). It is the value obtained by using (hereinafter the same).

  100 g (solid content) of the obtained polyether polyol-based urethane (meth) acrylate oligomer, 140 g (solid content) of isobornyl acrylate as an energy ray curable monomer, 160 g (solid content) of 2-hydroxy-3-phenoxypropyl acrylate, Trimethylolpropane tris (3-mercaptopropionate) (manufactured by SC Organic Chemical Co., Ltd., solid content concentration: 100% by mass) (hereinafter sometimes referred to as TMMP) 4.0 g, N -0.04 g of nitrosophenylhydroxylamine aluminum salt and 4 g of 2-hydroxy-2-methyl-1-phenyl-propan-1-one (manufactured by BASF: Darocur 1173, solid concentration 100% by mass) as a photopolymerization initiator Addition, room temperature liquid energy ray curing type It was obtained Narubutsu (viscosity η = 3060mPa · s, 25 ℃).

On the polyethylene terephthalate (PET) film-based release film (product name “SP-PET3811”, thickness 38 μm, manufactured by Lintec Co., Ltd.) which is a process sheet for casting, the energy ray curable composition is 300 μm in thickness by a fountain die method. The coating layer which consists of an energy-beam curable composition was formed in this way, and it irradiated with the ultraviolet-ray from this coating layer side after that. As the ultraviolet irradiation device, a belt conveyor type ultraviolet irradiation device (manufactured by Eye Graphics: ECS-401GX) and a high pressure mercury lamp (manufactured by Eye Graphics: H04-L41) were used as the ultraviolet light source {irradiation conditions: lamp height 150 mm, Lamp output 3 kW (converted output 120 mW / cm), illuminance 271 mW / cm ^{2 with} a light wavelength of 365 nm, light quantity 177 mJ / cm ² (UV light quantity meter: UV-351 manufactured by Oak Manufacturing Co., Ltd.)}. Then, a polyethylene terephthalate (PET) film (Mitsubishi Chemical Polyester Co., Ltd .: T-100, thickness 75 μm) was laminated as a thermoplastic resin layer on the semi-cured coating layer immediately after irradiation, and from the laminated PET film side. Further, UV irradiation {Irradiation conditions: lamp height 150 mm, lamp output 3 kW (converted output 120 mW / cm), illuminance 271 mW / cm ^{2 with} a light wavelength of 365 nm, light quantity 1200 mJ / cm ² (Oak Manufacturing UV light meter: UV-351) )} Was performed four times, the composition was crosslinked and cured to obtain an energy ray cured layer, the casting process sheet was removed, and an energy ray cured layer (300 μm) and a thermoplastic resin layer (75 μm) were laminated. A base material having a total thickness of 375 μm was obtained.

  Separately from the above, an acrylic copolymer having a weight average molecular weight of 500,000 and a glass transition temperature of −7 ° C. is obtained by solution polymerization in an ethyl acetate solvent using 70 parts by weight of butyl acrylate and 30 parts by weight of 2-hydroxyethyl acrylate. Was generated. 100 parts by weight of the solid content of this acrylic copolymer and 8 parts by weight of methacryloyloxyethyl isocyanate (80 equivalents with respect to 100 equivalents of hydroxyl groups in the acrylic copolymer) are reacted to form a polymerizable two molecule in the molecule. An ethyl acetate solution (30% solution) of an ultraviolet curable acrylic copolymer having a heavy bond was obtained.

For 100 parts by weight (solid content) of this ultraviolet curable acrylic copolymer, 2.0 parts by weight (solid ratio) of a polyisocyanate compound (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) and a photopolymerization initiator are used. (Irgacure 184, manufactured by BASF) 3.3 parts by weight (solid ratio) were mixed to obtain an ultraviolet curable pressure-sensitive adhesive composition. On the energy ray cured layer of the substrate, the ultraviolet curable pressure-sensitive adhesive composition was applied and dried to form a pressure-sensitive adhesive layer having a thickness of 50 μm to obtain a pressure-sensitive adhesive sheet.
Table 2 shows the evaluation results of the pressure-sensitive adhesive sheet. Separately from this, a pressure-sensitive adhesive sheet was prepared in the same manner as the pressure-sensitive adhesive sheet, except that the energy ray-curable composition was heated and stored at 80 ° C. for 500 hours and used as a raw material for the energy ray-curable layer. Went. The results are shown in Table 2. In Table 2, the result of the pressure-sensitive adhesive sheet prepared without heating and storing the energy ray curable composition was shown before heating and the result of the pressure-sensitive adhesive sheet prepared by heating and storage after heating. The same applies to other examples and comparative examples (in Comparative Example 2, since there was no energy beam curable composition, it was described in the column before heating for convenience). The composition of the energy beam curable composition is shown in Table 1.

(Example 2)
In place of TMMP 4.0 g used as the thiol group-containing compound in Example 1, 1,4-bis (3-mercaptobutyryloxy) butane (manufactured by Showa Denko KK: Karenz MT BD1, solid concentration 100 mass% ) A pressure-sensitive adhesive sheet was obtained and evaluated in the same manner as in Example 1 except that 0.8 g was used. The results are shown in Table 2. The composition of the energy beam curable composition is shown in Table 1.

(Example 3)
A pressure-sensitive adhesive sheet was obtained and evaluated in the same manner as in Example 1 except that the amount of Karenz MT BD1 used as the thiol group-containing compound in Example 2 was changed to 4.0 g. The results are shown in Table 2. The composition of the energy beam curable composition is shown in Table 1.

Example 4
A pressure-sensitive adhesive sheet was obtained and evaluated in the same manner as in Example 1 except that the addition amount of Karenz MT BD1 used as the thiol group-containing compound in Example 2 was changed to 6.0 g. The results are shown in Table 2. The composition of the energy beam curable composition is shown in Table 1.

(Example 5)
A pressure-sensitive adhesive sheet was obtained and evaluated in the same manner as in Example 1 except that the addition amount of Karenz MT BD1 used as the thiol group-containing compound in Example 2 was changed to 8.0 g. The results are shown in Table 2. The composition of the energy beam curable composition is shown in Table 1.

(Example 6)
The same as Example 1 except that 0.04 g of 2,2,6,6-tetramethyl-4-hydroxypiperazine-1-oxyl was used instead of N-nitrosophenylhydroxylamine aluminum salt in Example 3. An adhesive sheet was obtained by the method described above and evaluated. The results are shown in Table 2. The composition of the energy beam curable composition is shown in Table 1.

(Example 7)
In Example 3, a pressure-sensitive adhesive sheet was obtained and evaluated in the same manner as in Example 1 except that the amount of N-nitrosophenylhydroxylamine aluminum salt added was changed to 0.015 g. The results are shown in Table 2. The composition of the energy beam curable composition is shown in Table 1.

(Example 8)
In Example 3, a pressure-sensitive adhesive sheet was obtained and evaluated in the same manner as in Example 1 except that the amount of N-nitrosophenylhydroxylamine aluminum salt added was changed to 0.10 g. The results are shown in Table 2. The composition of the energy beam curable composition is shown in Table 1.

(Comparative Example 1)
In Example 1, except having not added N-nitrosophenylhydroxylamine aluminum salt, the adhesive sheet was obtained by the method similar to Example 1, and evaluated. The results are shown in Table 2. The composition of the energy beam curable composition is shown in Table 1.

(Comparative Example 2)
The same as Example 1 except that a single layer film of a polyethylene terephthalate (PET) film (Mitsubishi Chemical Polyester Co., Ltd .: T-100, thickness 188 μm) was used as the substrate without forming an energy ray cured layer. A pressure-sensitive adhesive sheet was obtained by the method and evaluated. The results are shown in Table 2. The composition of the energy beam curable composition is shown in Table 1.

  As can be seen from Table 2, the sheets of Examples 1 to 8 show almost no change in the compressive load and compressive stress before and after heating as compared with the sheets of Comparative Examples 1 and 2. Further, the sheets of Examples 1 to 8 hardly generate dimples after heating.

Claims (5)

  It consists of a cured product obtained by energy ray curing a compound containing a urethane (meth) acrylate oligomer, a compound having a thiol group in the molecule, and an N-nitrosamine polymerization inhibitor and / or an N-oxyl polymerization inhibitor. Sheet.   The content of the N-nitrosamine polymerization inhibitor and / or the N-oxyl polymerization inhibitor in the blend is 0.5 to 5 g with respect to 100 g of the compound having a thiol group in the molecule. The described sheet.   A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer on a substrate composed of the sheet according to claim 1 and a sheet made of a thermoplastic resin.   A method for processing a semiconductor wafer, comprising attaching a circuit surface of a semiconductor wafer having a circuit formed on the surface thereof to the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to claim 3 and grinding the back surface of the semiconductor wafer. A groove having a depth of cut shallower than the wafer thickness is formed from the surface of the semiconductor wafer on which a circuit having bumps is formed,
Affixing the adhesive sheet according to claim 3 on the circuit forming surface,
Then, the semiconductor wafer manufacturing method includes a step of reducing the thickness of the wafer by grinding the back surface of the semiconductor wafer, and finally dividing the wafer into individual chips and picking up the chips.