JP6717484B2 - Adhesive sheet - Google Patents

Description

The present invention relates to an adhesive sheet that is attached to an adherend such as a semiconductor wafer and used to protect the adherend, and more particularly to a back grind sheet.

Along with the rapid progress of thinning, downsizing and multi-functionality of information terminal equipment, semiconductor devices mounted therein are also required to be thin and high density. In order to reduce the thickness of the device, it is required to reduce the thickness of a semiconductor wafer on which semiconductors are integrated. In order to meet the demand, the back surface of a semiconductor wafer is ground to reduce its thickness.
In recent years, bumps made of solder or the like having a height of about 30 to 100 μm are formed on the front surface of the wafer, and the back surface of the semiconductor wafer having irregularities may be ground. When such a semiconductor wafer with bumps is back-ground, an adhesive sheet called a back grind sheet is attached to the surface of the wafer on which the bumps are formed in order to protect the bumps.

The pressure-sensitive adhesive sheet used for the back-grinding sheet may include an intermediate layer between the base material and the pressure-sensitive adhesive layer in order to embed the bumps and absorb and reduce the height difference on the surface of the semiconductor wafer. The intermediate layer has a low storage elastic modulus at a high temperature and a high room temperature at a room temperature in order to improve the embedding property of the bumps at the bonding temperature, enhance the holding property of the wafer surface at room temperature, and improve the shape stability when formed into a roll. It is known that energy ray-curable resins, which become higher below, are used.
However, if only the energy ray-curable resin is used, the intermediate layer may be excessively softened at the application temperature, and the intermediate layer may seep out during application, and the intermediate layer may provide sufficient bump height difference. Sometimes it can't be absorbed. In order to solve these problems, as disclosed in Patent Document 1, an intermediate layer in which a heat melting resin having crystallinity is dispersed in a matrix resin made of an energy ray curable resin is also known.

JP, 2013-87131, A

However, when the heat-melting resin having crystallinity is dispersed in the intermediate layer as in Patent Document 1, the film forming property of the intermediate layer may be deteriorated. Therefore, there is a demand for an intermediate layer that can appropriately fill bumps to sufficiently reduce the height difference without using a heat-melting resin and can prevent exudation during sticking.

The present invention has been made in view of the above problems, and when it is adhered to an adherend such as a semiconductor wafer even when the intermediate layer does not contain a crystalline heat-melting resin, An object of the present invention is to provide a pressure-sensitive adhesive sheet that can prevent bleeding of an intermediate layer at the time of sticking, while improving the embeddability in the irregularities formed on the body.

As a result of earnest studies, the inventors of the present invention, by curing a monofunctional monomer containing a crystalline monomer and a polyfunctional compound contained in a predetermined ratio or more with respect to the monofunctional monomer to form an intermediate layer, The inventors have found that the above problems can be solved and completed the following inventions.
(1) A pressure-sensitive adhesive sheet comprising a base material, an intermediate layer, and a pressure-sensitive adhesive layer in this order,
Composition for intermediate layer, wherein the intermediate layer contains a polyfunctional compound having at least two polymerizable functional groups and a monofunctional monomer containing at least a crystalline monomer having a linear carbon chain having 14 to 22 carbon atoms. Is a cured product of
In the composition for the intermediate layer, a pressure-sensitive adhesive sheet, wherein the polyfunctional compound is contained in an amount of 25% by mass or more based on the monofunctional monomer.
(2) The pressure-sensitive adhesive sheet according to (1) above, wherein 40% by mass or more of the monofunctional monomer is the crystalline monomer.
(3) The pressure-sensitive adhesive sheet according to (1) or (2), wherein the polyfunctional compound is a polyfunctional oligomer having a weight average molecular weight of 3,000 to 60,000.
(4) The pressure-sensitive adhesive sheet according to any one of (1) to (3), wherein the polymerizable functional group of the polyfunctional compound is a group having an ethylenic double bond.
(5) Any of the above (1) to (4), wherein the polyfunctional compound is at least one selected from the group consisting of urethane (meth)acrylate oligomers, acrylic polymers, and butadiene polymers. The adhesive sheet described.
(6) The pressure-sensitive adhesive sheet according to any one of (1) to (5), wherein the crystalline monomer is contained in an amount of 25 to 70 mass% with respect to the total amount of the intermediate layer composition.
(7) The pressure-sensitive adhesive sheet according to any one of (1) to (6), wherein the intermediate layer composition is an energy ray-curable composition.
(8) The pressure-sensitive adhesive sheet according to any one of (1) to (7), wherein the intermediate layer has a thickness of 150 to 700 μm.
(9) The pressure-sensitive adhesive sheet according to any one of (1) to (8), which is a semiconductor wafer protection tape.

The present invention provides a pressure-sensitive adhesive sheet which, when applied to an adherend such as a semiconductor wafer, has a good embedding property for the irregularities of the adherend and can prevent the intermediate layer from seeping out at the time of attachment. be able to.

It is sectional drawing which shows the adhesive sheet which concerns on one Embodiment of this invention. It is sectional drawing which shows the adhesive sheet which concerns on other embodiment of this invention.

Hereinafter, the present invention will be described using embodiments. In the following description, the “weight average molecular weight (Mw)” is a polystyrene conversion value measured by a gel permeation chromatography (GPC) method, and specifically, based on the method described in Examples. It is the measured value.
In addition, in the description in the present specification, for example, “(meth)acrylate” is used as a word indicating both “acrylate” and “methacrylate”, and the same applies to other similar terms.

1 and 2 show an adhesive sheet according to an embodiment of the present invention. The pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as the pressure-sensitive adhesive sheet 10A shown in FIG. 1 is such that the intermediate layer 12 is provided on the base material 11 and the pressure-sensitive adhesive layer 13 is further provided on the intermediate layer 12. There is no. The pressure-sensitive adhesive sheet may be composed of these three layers, or may be provided with another layer. For example, like the pressure-sensitive adhesive sheet 10B shown in FIG. 2, a release material 14 may be further provided on the pressure-sensitive adhesive layer 13.

Hereinafter, each member constituting the adhesive sheet will be described in more detail.
[Middle layer]
The intermediate layer is a composition for an intermediate layer containing a polyfunctional compound having at least two polymerizable functional groups and a monofunctional monomer containing at least a crystalline monomer having a linear carbon chain having 14 to 22 carbon atoms. It is a cured product.
In the present invention, the intermediate layer composition forming the intermediate layer contains a polyfunctional compound and a monofunctional monomer, and at least a part of the monofunctional monomer is a crystalline monomer, the pressure-sensitive adhesive sheet is a semiconductor. It is possible to improve the embedding property for the unevenness of the adherend surface such as the bump of the wafer. Further, when the pressure-sensitive adhesive sheet is attached to an adherend such as a semiconductor wafer at a high temperature, it becomes possible to prevent the intermediate layer from seeping out.
The composition for the intermediate layer is a composition that is cured by polymerizing a polyfunctional compound and a monofunctional monomer to form an intermediate layer. The intermediate layer composition is preferably an energy ray curable type that is cured by energy rays. The energy ray refers to an electromagnetic wave or a charged particle beam that has energy quantum, and refers to active light such as ultraviolet rays or an electron beam, but it is preferable to use ultraviolet rays.

<Polyfunctional compound>
The polyfunctional compound is contained in the intermediate layer composition in an amount of more than 25% by mass based on the total amount of monofunctional monomers. When the content of the polyfunctional compound is 25% by mass or less, it becomes difficult to secure the embedding property. The content of the polyfunctional compound is preferably 30% by mass or more, more preferably 50% by mass or more. When the content is 30% by mass or more, the embedding property is likely to be improved. The upper limit of this content is preferably 250% by mass or less, more preferably 200% by mass or less in order to secure the content of the monofunctional monomer to some extent.

The polymerizable functional group contained in the polyfunctional compound is preferably a group having an ethylenic double bond. The polyfunctional compound having an ethylenic double bond can be cured by energy rays such as ultraviolet rays. Here, specific examples of the group having an ethylenic double bond include a (meth)acryloyl group and a vinyl group, and a (meth)acryloyl group is preferable.
The polyfunctional compound may be either a polyfunctional monomer or a polyfunctional oligomer, but it is preferable to use the polyfunctional oligomer because the interaction with the crystalline monomer becomes stronger when cured. As the polyfunctional compound, one type may be used alone, or two or more types may be used in combination. When two or more polyfunctional compounds are used, either one of the polyfunctional monomer and the polyfunctional oligomer may be used, or both the polyfunctional monomer and the polyfunctional oligomer may be used.

(Polyfunctional oligomer)
The weight average molecular weight of the polyfunctional oligomer is preferably 3,000 to 60,000, and more preferably 5,000 to 50,000. By setting the weight average molecular weight in the above range, the embedding property of the intermediate layer can be improved and the exudation of the intermediate layer can be easily prevented. Further, while the polyfunctional oligomer is in a liquid state, its viscosity is in an appropriate range, and it becomes easy to improve the film forming property.
Specific examples of polyfunctional oligomers that can be used in the intermediate layer include urethane (meth)acrylate oligomers, acrylic polymers, butadiene polymers, and polyisoprene. Among these, urethane (meth)acrylate oligomers, acrylic polymers, and butadiene polymers are preferable. As the oligomer, a monofunctional oligomer having only one polymerizable functional group is known, but in the present invention, when a monofunctional oligomer is used instead of the polyfunctional oligomer, the intermediate layer is excessively softened at high temperature. Therefore, it becomes difficult to prevent the intermediate layer from seeping out.
Hereinafter, the urethane (meth)acrylate oligomer, the acrylic polymer, and the butadiene polymer that can be used as the polyfunctional oligomer will be specifically described.

<Urethane (meth)acrylate oligomer>
The urethane (meth)acrylate oligomer is a compound having at least a (meth)acryloyl group and a urethane bond, and has a property of being polymerized by irradiation with energy rays.
The number of (meth)acryloyl groups (that is, polymerizable functional groups) in the urethane (meth)acrylate oligomer may be two or three or more, but is preferably two. The urethane (meth)acrylate oligomer can be obtained, for example, by reacting a hydroxyl group-containing (meth)acrylate with a terminal isocyanate urethane prepolymer obtained by reacting a polyol compound with a polyvalent isocyanate compound.
In addition, you may use a urethane (meth)acrylate oligomer individually or in combination of 2 or more types.

a. Polyol Compound A polyol compound is a compound having two or more hydroxy groups, and specific polyol compounds include, for example, polyether type polyols, polyester type polyols, polycarbonate type polyols and the like. Ether-type polyols are preferred. The polyol compound may be any of a bifunctional diol, a trifunctional triol, and a tetrafunctional or higher functional polyol, but a bifunctional diol is preferable.

上記式（１）中、Ｒは、２価の炭化水素基であるが、アルキレン基が好ましく、炭素数１〜６のアルキレン基がより好ましい。炭素数１〜６のアルキレン基の中でも、エチレン基、プロピレン基、テトラメチレン基が好ましく、プロピレン基、テトラメチレン基がより好ましい。For example, the polyether type polyol is preferably a compound represented by the following formula (1).

In the above formula (1), R is a divalent hydrocarbon group, preferably an alkylene group, and more preferably an alkylene group having 1 to 6 carbon atoms. Among the alkylene groups having 1 to 6 carbon atoms, ethylene group, propylene group and tetramethylene group are preferable, and propylene group and tetramethylene group are more preferable.

Further, n is the number of repeating units of alkylene oxide and is usually 10 to 250, preferably 25 to 205, more preferably 40 to 185. When n is in the above range, the urethane bond concentration of the obtained urethane (meth)acrylate oligomer is moderated, and the flexibility of the intermediate layer is easily increased.
Among the compounds represented by the above formula (1), polyethylene glycol, polypropylene glycol and polytetramethylene glycol are preferable, and polypropylene glycol and polytetramethylene glycol are more preferable.

The polyester type polyol is obtained by polycondensing a polyol component and a polybasic acid component. Examples of the polyol component 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 include known various glycols such as -butyl-1,3-propanediol, 1,4-cyclohexanedimethanol, and ethylene glycol or propylene glycol adduct of bisphenol A.
As the polybasic acid component used for producing the polyester type polyol, a compound generally known as a polybasic acid component of polyester can be used.
Specific polybasic acid components include, for example, adipic acid, maleic acid, succinic acid, oxalic acid, fumaric acid, malonic acid, glutaric acid, pimelic acid, azelaic acid, sebacic acid, suberic acid and the like. Acids: dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, and 2,6-naphthalenedicarboxylic acid; aromatic polybasic acids such as polybasic acids such as trimellitic acid and pyromellitic acid; and their corresponding anhydrides. Examples thereof include substances and their derivatives, dimer acid, hydrogenated dimer acid and the like.

The polycarbonate type polyol is not particularly limited, but a polyalkylene carbonate diol is exemplified. The polyalkylene carbonate diol is a polytetramethylene carbonate diol, a polypentamethylene carbonate diol, a polyhexamethylene carbonate diol, or a copolymer having a mixed alkylene chain of two or more kinds selected from tetramethylene, pentamethylene and hexamethylene. Examples thereof include those having a linear alkylene group having about 4 to 8 carbon atoms as a repeating unit, which is exemplified by a combination and the like.

b. Polyvalent isocyanate 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, Alicyclic diisocyanates such as dicyclohexylmethane-2,4'-diisocyanate, ω,ω'-diisocyanate dimethylcyclohexane; 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, tetramethylene xylylene diisocyanate Examples thereof include aromatic diisocyanates such as isocyanate and naphthalene-1,5-diisocyanate.
Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferable from the viewpoint of handleability.

c. (Meth) Acrylate Having Hydroxy Group Urethane (meth) acrylate oligomer by reacting (meth) acrylate having a hydroxy group with a terminal isocyanate urethane prepolymer obtained by reacting the above-mentioned polyol compound with a polyvalent isocyanate compound. Can be obtained.
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 at least one molecule.

Specific examples of the (meth)acrylate having a hydroxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 4-hydroxycyclohexyl (meth). Acrylate, 5-hydroxycyclooctyl (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, etc. Hydroxyalkyl (meth)acrylate; hydroxy group-containing (meth)acrylamide such as N-methylol (meth)acrylamide; reaction obtained by reacting diglycidyl ester of vinyl alcohol, vinylphenol, bisphenol A with (meth)acrylic acid Things etc. are mentioned.
Among these, hydroxyalkyl (meth)acrylate is preferable, and 2-hydroxyethyl (meth)acrylate is more preferable.

<Acrylic polymer>
Examples of the acrylic polymer used as the polyfunctional compound include those obtained by polymerizing a (meth)acrylic acid ester, and preferably the alkyl group has 1 to 10 carbon atoms, more preferably the alkyl group has 3 to 10 carbon atoms. The thing which polymerized the alkyl (meth)acrylate of 8 is mentioned.
Here, the alkyl group in the alkyl (meth)acrylate may be branched or linear. Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-. Butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate and the like can be mentioned. The acrylic polymer has a polymerizable functional group at both ends, and the polymerizable functional group is usually a (meth)acryloyl group.

<<Butadiene polymer>>
Examples of the butadiene-based polymer include those having two or more vinyl groups in the side chain. In this butadiene-based polymer, the vinyl group on the side chain becomes a polymerizable functional group and can react with a monofunctional monomer to be cured. The butadiene-based polymer is obtained by polymerizing butadiene as a monomer unit, and usually contains 1,4 bond units and 1,2 vinyl bond units.

(Polyfunctional monomer)
Further, examples of the polyfunctional monomer that can be used as the polyfunctional compound include (meth)acrylic acid-based polyfunctional monomers, and the (meth)acrylic acid-based polyfunctional monomer is specifically pentaerythritol tri(meth)acrylate. ) Acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene oxide-added glycerin (meth)acrylate, dipropylene glycol di (Meth)acrylate and the like.

<Monofunctional monomer>
(Crystalline monomer)
The monofunctional monomer is a monomer having one ethylenic double bond. The monofunctional monomer contained in the intermediate layer composition contains at least a crystalline monomer. The crystalline monomer has a linear carbon chain having 14 to 22 carbon atoms, and imparts crystallinity to the side chain of the obtained polymer when the composition for intermediate layer is polymerized by a curing reaction. Is. In the present invention, since the composition for intermediate layer contains the crystalline monomer, the intermediate layer has a low elastic modulus and is deformed at the time of sticking by heating, and the embeddability is easily improved. The crystalline monomer is a monomer having an ethylenic double bond and having crystallinity in its side chain due to the above-mentioned linear carbon chain having 14 to 22 carbon atoms.

It is preferable that 40% by mass or more of the monofunctional monomer contained in the composition for the intermediate layer becomes the crystalline monomer. In the present invention, when the content of the crystalline monomer is 40% by mass or more, the elastic modulus becomes better at the time of sticking by heating, and the embeddability becomes good while preventing the exudation of the intermediate layer when sticking the pressure-sensitive adhesive sheet. It becomes possible to do.
Further, the monofunctional monomer is more preferably 45 to 100% by mass of the crystalline monomer, and further preferably 77 to 100% by mass of the crystalline monomer. As described above, when the content of the crystalline monomer in the monofunctional monomer is increased, the elastic modulus of the intermediate layer is significantly decreased during heating and sticking, and thus it is possible to exhibit better embedding property. It is possible to prevent the resin from seeping out from the intermediate layer of the pressure-sensitive adhesive sheet during storage.

The crystalline monomer has one ethylenic double bond. Specifically, it preferably has a (meth)acryloyl group or a vinyl group as a functional group, and more preferably has a (meth)acryloyl group. preferable. Since the crystalline monomer has an ethylenic double bond, it can be easily polymerized by irradiation with energy rays. Further, by having a (meth)acryloyl group, the curing reaction can easily proceed.
The crystalline monomer preferably has a linear alkyl group having 14 to 22 carbon atoms. Since the crystalline monomer has such a straight chain alkyl group having a long carbon chain, it becomes possible to impart crystallinity to the side chain of the polymer obtained by curing the composition for intermediate layer. The linear alkyl group preferably has 16 to 20 carbon atoms.

Specific examples of the crystalline monomer include an alkyl (meth)acrylate having a linear alkyl group having 14 to 22 carbon atoms and an alkyl vinyl ether having a linear alkyl group having 14 to 22 carbon atoms. Alkyl (meth)acrylates having 22 linear alkyl groups are preferred. By using the alkyl (meth)acrylate, the curing reaction can be easily progressed well.
Examples of the alkyl (meth)acrylate having a linear alkyl group having 14 to 22 carbon atoms include myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, araquinyl (meth)acrylate, and behenyl (meth). ) Acrylate is mentioned, and among these, stearyl (meth)acrylate is preferable from the viewpoint of easy availability and the like.
Examples of the alkyl vinyl ether having a linear alkyl group having 14 to 22 carbon atoms include myristyl vinyl ether, palmityl vinyl ether, stearyl vinyl ether, araquinyl vinyl ether, behenyl vinyl ether and the like.

The crystalline monomer is preferably contained in an amount of 25 to 70% by mass, more preferably 40 to 60% by mass, based on the total amount of the composition for intermediate layer. When the content is 25% by mass or more, the portion having crystallinity in the intermediate layer increases, the elastic modulus of the intermediate layer decreases at high temperature, and it becomes easy to improve the embedding property. Further, when the content is 70% by mass or less, it becomes easy to secure the flexibility required for the intermediate layer.

(Other monofunctional monomers)
The monofunctional monomer contained in the composition for the intermediate layer may consist of only the above-mentioned crystalline monomer, but may contain a monofunctional monomer other than the crystalline monomer.
The monofunctional monomer other than the crystalline monomer contains a group having an ethylenic double bond such as a (meth)acryloyl group and a vinyl group, and specifically, a (meth)acrylate having an alicyclic structure. A functional group-containing (meth)acrylate, an alkyl group having an alkyl group having less than 14 carbon atoms (meth)acrylate, an amide group-containing compound, an aromatic structure-containing (meth)acrylate, a heterocyclic structure-containing (meth)acrylate, Other vinyl compounds and the like can be mentioned, but among these, it is preferable to use at least one of a (meth)acrylate having an alicyclic structure and a functional group-containing (meth)acrylate.

Examples of the (meth)acrylate having an alicyclic structure include isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, cyclohexyl (meth)acrylate. , Adamantane (meth)acrylate and the like, and of these, isobornyl (meth)acrylate is preferable.

Examples of the functional group used in the functional group-containing (meth)acrylate include a hydroxyl group, an amino group, and an epoxy group. Specific examples of the functional group-containing (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate and 3 -Hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate and other hydroxyl group-containing (meth)acrylates; primary amino group-containing (meth)acrylates, Amino group-containing (meth)acrylates such as secondary amino group-containing (meth)acrylates and tertiary amino group-containing (meth)acrylates; epoxy groups such as glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, allyl glycidyl ether Examples include contained (meth)acrylates. Among these, hydroxyl group-containing (meth)acrylates are preferable, and 2-hydroxy-3-phenoxypropyl (meth)acrylate is more preferable.

Examples of the alkyl(meth)acrylate whose alkyl group has less than 14 carbon atoms include methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate. , Isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (Meth)acrylate, n-decyl (meth)acrylate, etc. are mentioned.

Examples of the amide group-containing compound include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxy. Examples thereof include (meth)acrylamide compounds such as methyl(meth)acrylamide and N-butoxymethyl(meth)acrylamide.
Examples of the (meth)acrylate having an aromatic structure include benzyl (meth)acrylate. Examples of the (meth)acrylate having a heterocyclic structure include tetrahydrofurfuryl (meth)acrylate and morpholine acrylate. Examples of other vinyl compounds include styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylformamide, N-vinylpyrrolidone and N-vinylcaprolactam.

<Photopolymerization initiator>
The composition for the intermediate layer preferably contains a photopolymerization initiator so that it can be easily cured by being irradiated with active light such as ultraviolet rays.
Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and other photopolymerization initiators. More specifically, for example, 1 -Hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, 2,4,6-trimethylbenzoyl-diphenyl-phos Examples include fin oxide. Also, depending on the type of polyfunctional compound or monofunctional monomer, aromatic diazonium salts, aromatic halonium salts, onium salts of aromatic sulfonium salts, nitrobenzyl esters, sulfonic acid derivatives, phosphoric acid esters, sulfonic acids may be used in addition to the above. It is also possible to use a cationic photopolymerization initiator such as a derivative, or an anionic photopolymerization initiator such as a catalyst system of alkoxytitanium and p-chlorophenyl-o-nitrobenzyl ether. The photopolymerization initiator can be used alone or in combination of two or more kinds.
The content of the photopolymerization initiator is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and still more preferably 100 parts by mass of the polyfunctional compound and the monofunctional monomer. It is 0.3 to 5 parts by mass. Further, the intermediate layer composition may contain a photosensitizer such as amine and quinone.

The composition for the intermediate layer may contain other additives as long as the effects of the present invention are not impaired. Examples of other additives include antioxidants, antistatic agents, softening agents (plasticizers), fillers, rust preventives, pigments, dyes and the like.

Moreover, it is preferable that the composition for the intermediate layer does not substantially contain the heat-meltable resin. The composition for an intermediate layer of the present invention contains a crystalline monomer component, thereby preventing the exudation of the intermediate layer at the time of sticking and substantially improving the embedding property even when the composition does not substantially contain a heat-meltable resin. Can be good. The heat-meltable resin is one in which a clear and sharp melting peak is observed in DSC measurement, and specifically, the difference between the melting start temperature and the melting peak temperature (melting point (Tm)) is 8° C. or less. The melting point (Tm) is, for example, 45 to 90°C. Examples of the heat-meltable resin include an acrylic polymer that becomes a wax at room temperature, an α-olefin polymer having 14 to 30 carbon atoms, and the like.
The term "substantially free of heat-meltable resin" means that the intermediate layer composition may contain a heat-meltable resin to the extent that the film-forming property of the intermediate layer is not affected, For example, it means that it may be contained in an amount of less than 2% by mass based on the total amount of the composition for intermediate layer, but the content is preferably less than 1% by mass, and more preferably not contained. By substantially not containing the heat-meltable resin, it becomes possible to suppress the occurrence of agglomeration and the increase in viscosity due to the solid polymer material in the intermediate layer composition.
The composition for the intermediate layer usually contains the above-mentioned polyfunctional compound and a monofunctional monomer as main components, and the total amount thereof is usually 70% by mass or more, preferably the total amount of the composition for the intermediate layer, Is 80% by mass or more, and more preferably 90% by mass or more. Further, the total amount thereof may be 100% by mass or less with respect to the total amount of the composition for the intermediate layer, but in order to mix an additive such as a photopolymerization initiator, preferably 99.9% by mass or less, It is preferably 99.7 mass% or less. The total amount of the composition for the intermediate layer is an amount excluding volatile components such as the diluent solvent when the composition is diluted with a solvent or the like that is volatilized in the manufacturing process.

The thickness of the intermediate layer is appropriately adjusted according to the height of the pump or the like to be protected, but it is preferably 150 to 700 μm, more preferably 200 to 300 μm. When the thickness of the intermediate layer is 150 μm or more, even an adherend such as a wafer having a high bump and a relatively high difference in height can be appropriately protected. Further, when the thickness is 700 μm or less, the strain generated when the pressure-sensitive adhesive sheet is bent can be reduced.

[Base material]
The base material used for the pressure-sensitive adhesive sheet is not particularly limited, but is preferably a resin film. A resin film is suitable for a processed member of an electronic component because it generates less dust than paper or a non-woven fabric and is easily available. The base material may be a single-layer film made of one resin film or a multi-layer film in which a plurality of resin films are laminated.
Examples of the resin film used as the base material include a polyolefin film, a vinyl halide polymer film, an acrylic resin film, a rubber film, a cellulose film, a polyester film, a polycarbonate film, a polystyrene film, and a polyphenylene sulfide. Examples of the film include a system film and a cycloolefin polymer film.
Among these, a polyester film is preferable from the viewpoint that the wafer can be stably held when it is ground to an extremely thin thickness, and from the viewpoint that the film has high thickness accuracy, and among the polyester films, A polyethylene terephthalate film is preferable from the viewpoints of easy availability and high thickness accuracy.
The thickness of the base material is not particularly limited, but is preferably 10 to 250 μm, more preferably 20 to 200 μm.

From the viewpoint of improving the adhesiveness between the base material and the intermediate layer, a base material in which an easily adhesive layer or the like is further laminated on the surface of the resin film may be used. Further, the base material may contain a filler, a colorant, an antistatic agent, an antioxidant, an organic lubricant, a catalyst and the like within a range that does not impair the effects of the present invention.
The substrate may be transparent or opaque. However, when the pressure-sensitive adhesive or the composition for the intermediate layer constituting the pressure-sensitive adhesive layer is an energy ray-curable type, the base material preferably transmits energy rays.

[Adhesive layer]
Examples of the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer include acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives, silicone pressure-sensitive adhesives, polyvinyl ether pressure-sensitive adhesives and urethane pressure-sensitive adhesives. Agents are preferred. The pressure-sensitive adhesive may also include energy ray-curable, energy ray-foaming pressure-sensitive adhesive, heat-foaming type, and water-swelling type, among which energy ray such as ultraviolet ray-curing type or electron beam-curing type. A curable adhesive is preferable, and an ultraviolet curable adhesive is more preferable.

By using the energy ray-curable pressure-sensitive adhesive, the pressure-sensitive adhesive sheet can be surely adhered to the semiconductor wafer before the energy ray irradiation, and the adherend such as the semiconductor wafer can be surely protected. On the other hand, when peeling off the pressure-sensitive adhesive sheet, it is possible to reduce the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer by irradiating energy rays, so that the adherend such as a semiconductor wafer is not damaged and the pressure-sensitive adhesive is The adhesive sheet can be peeled off from the adherend without leaving it on the adherend.

The energy ray-curable pressure-sensitive adhesive may be an addition-type energy ray-curable pressure-sensitive adhesive containing a base polymer such as an acrylic copolymer and an energy ray-curable resin. A so-called intrinsic type energy ray-curable pressure-sensitive adhesive may be used in which a polymer having a heavy bond in the side chain of the polymer or in the main chain or at the end of the main chain is used as a base polymer such as an acrylic copolymer.
The pressure-sensitive adhesive contains, in addition to a base polymer such as an acrylic copolymer, a crosslinking agent, a photopolymerization initiator, and the like, if necessary.
The thickness of the pressure-sensitive adhesive layer is adjusted according to the height difference of the adherend surface such as a semiconductor wafer and the performance required for the pressure-sensitive adhesive sheet, and is usually 3 to 200 μm, preferably 7 to 150 μm, more preferably 10 to 100 μm. Is.

[Release material]
The release material constituting the pressure-sensitive adhesive sheet, and the release material used in the step of the manufacturing method described later, a release sheet subjected to a single-sided release treatment, a release sheet subjected to a double-sided release treatment, or the like is used, and a release material base. Examples thereof include a material coated with a release agent.
Examples of the base material for the release material include polyester films such as polyethylene terephthalate resin, polybutylene terephthalate resin and polyethylene naphthalate resin, and plastic films such as polypropylene resin and polyolefin resin film such as polyethylene resin.
Examples of the release agent include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, and fluorine-based resins.
The thickness of the release material is not particularly limited, but is preferably 5 to 200 μm, more preferably 10 to 120 μm.

[Production method of adhesive sheet]
The method for producing the pressure-sensitive adhesive sheet of the present invention is not particularly limited, and the pressure-sensitive adhesive sheet can be produced by a known method.
For example, the intermediate layer can be formed by directly applying the intermediate layer composition to one surface of the substrate to form a coating film, and then performing a curing treatment. The intermediate layer may be formed by directly applying the intermediate layer composition to the release-treated surface of the release material, performing the curing treatment, and then bonding the base material onto the coating film. At this time, the release material may be appropriately removed, for example, after the curing process is completed. The intermediate layer is preferably cured by irradiating the formed coating film with energy rays such as ultraviolet rays to polymerize and cure. At this time, the irradiation amount of energy rays is appropriately changed depending on the type of energy rays, the thickness of the coating film, and the like. For example, when ultraviolet rays are used, the illuminance of the ultraviolet rays to be irradiated is preferably 50 to 500 mW/cm ² . The amount of ultraviolet light is preferably 100 to 2500 mJ/cm ² .
The pressure-sensitive adhesive layer can be formed, for example, by directly coating the pressure-sensitive adhesive composition on the intermediate layer formed as described above and drying it. In addition, the pressure-sensitive adhesive composition is applied to the release-treated surface of the release material and dried to form a pressure-sensitive adhesive layer on the release material, and then the pressure-sensitive adhesive layer on the release material and the intermediate layer are bonded together. Alternatively, an adhesive sheet provided with an intermediate layer, an adhesive layer, and a release material may be formed on a substrate. After that, the release material in the pressure-sensitive adhesive sheet may be released as necessary.

When forming the intermediate layer or the pressure-sensitive adhesive layer, an organic solvent may be further added to the intermediate-layer composition or the pressure-sensitive adhesive composition to prepare a diluted solution of the intermediate-layer composition or the pressure-sensitive adhesive composition.
Examples of the organic solvent used include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, isopropanol and the like.
As these organic solvents, the organic solvent used at the time of synthesizing each component contained in the intermediate layer composition or the pressure-sensitive adhesive composition may be used as it is, or one or more other organic solvents may be used. You may add.

The composition for the intermediate layer or the pressure-sensitive adhesive composition can be applied by a known application method. Examples of the coating method include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.
In addition, when the composition for intermediate layer or the pressure-sensitive adhesive composition contains an organic solvent, it is preferable to apply this and then heat it for drying treatment.

[How to use adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention can be used for various purposes, but it is preferably attached to a semiconductor wafer and used as a semiconductor wafer protection tape. Further, it is more preferable that the pressure-sensitive adhesive sheet is attached to the front surface of the semiconductor wafer and used as a bag grind tape for protecting the circuit formed on the front surface of the wafer during the subsequent wafer back surface grinding.
Since the pressure-sensitive adhesive sheet of the present invention has a good embedding property even if there is a difference in height due to bumps or the like on the wafer surface, the performance of protecting the wafer surface is good. Further, when the pressure-sensitive adhesive sheet is attached to the wafer, the pressure-sensitive adhesive sheet is heated, but even if the pressure-sensitive adhesive sheet is heated and attached, the intermediate layer does not exude.
The height of the bumps formed on the surface of the wafer is not particularly limited, but by appropriately selecting the thickness of the intermediate layer or the adhesive layer of the pressure-sensitive adhesive sheet of the present invention, the embeddability of bumps of various heights can be improved. It is possible to
The temperature of the adhesive sheet when it is attached to a semiconductor wafer is, for example, about 40 to 80°C, preferably 50 to 60°C.
The pressure-sensitive adhesive sheet is not limited to the back grind sheet, and can be used for other purposes. For example, the adhesive sheet may be attached to the back surface of the wafer and used as a dicing sheet that protects the back surface of the wafer when dicing the wafer.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

The measuring method and the evaluating method in the present invention are as follows.
[Weight average molecular weight (Mw)]
A gel permeation chromatograph (product name "HLC-8020", manufactured by Tosoh Corporation) was used to measure under the following conditions, and the value measured in terms of standard polystyrene was used.
(Measurement condition)
Column: "TSK guard column HXL-H""TSK gel GMHXL (x2)""TSK gel G2000HXL" (all manufactured by Tosoh Corporation)
Column temperature: 40°C Developing solvent: Tetrahydrofuran Flow rate: 1.0 mL/min
[Embedding property evaluation]
The pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples were applied to a bumped wafer (Waltz 8-inch wafer) having a bump height of 80 μm, a pitch of 200 μm, and a diameter of 100 μm. 12 was used for attachment. The laminating table of the device was set to 60° C. and the laminating roll was set to 60° C. at the time of sticking. After lamination, the diameter of the circular void generated around the bump from the substrate side was measured using a digital optical microscope (product name “VHX-1000”, manufactured by KEYENCE CORPORATION). It is shown that the smaller the diameter of the void, the higher the embeddability of the adhesive sheet to the bump. The embeddability of bumps was evaluated based on the following criteria. The results are shown in Table 1.
A: The diameter of the void is less than 120 μm.
B: The diameter of the void is 120 μm to 130 μm.
C: Bubbles are connected to adjacent bumps.
[Evaluation of seepage]
A 25 mm×50 mm adhesive sheet was laminated on the silicon mirror wafer. The lamination conditions used were the same as those used when evaluating the embedding property. After lamination, visual observation was carried out, and the case where the resin of the intermediate layer did not bleed was designated as A, and the case where bleeding was confirmed was designated as C.

[Example 1]
(Formation of intermediate layer)
40 parts by mass (solid content ratio) of bifunctional urethane acrylate oligomer (product name “CN9018”, manufactured by Arkema, weight average molecular weight 45000) as a polyfunctional compound, and 60 parts by mass (solid) of stearyl acrylate (STA) as a crystalline monomer. Ratio), and 2.0 parts by mass (solid content ratio) of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (product name “Darocur TPO”, manufactured by BASF) as a photopolymerization initiator, A UV curable intermediate layer composition was obtained. The composition for the intermediate layer was formed on a polyethylene terephthalate (PET) film-based release film (product name "SP-PET381031", manufactured by Lintec Co., Ltd., thickness: 38 µm) by a fountain die method to give a thickness of 200 µm after curing. And the coating film was formed.
Then, ultraviolet rays are irradiated from the coating film side to cure the coating film, and a 50 μm-thick polyethylene terephthalate (PET) film base material is laminated on the coating film to form a 200 μm-thick intermediate layer on the base material. Layers were formed. For the ultraviolet irradiation, a belt conveyor type ultraviolet irradiation device (product name “ECS-401GX”, manufactured by Eye Graphics Co., Ltd.) was used as an ultraviolet irradiation device, and a high pressure mercury lamp (product name “H04-L41” was used as an ultraviolet source. ”, manufactured by Eye Graphics Co., Ltd., and used as irradiation conditions with an illuminance of 365 nm at an illuminance of 190 mW/cm ² and a light amount of 113 mJ/cm ² (ultraviolet light meter (product name “UVPF-A1”, manufactured by Eye Graphics Co., Ltd.) Measurement).

(Formation of adhesive sheet)
A copolymer (Mw: 1.3 million) obtained by copolymerizing 94% by mass of 2-ethylhexyl acrylate and 6% by mass of 2-hydroxyethyl acrylate was reacted with 50 mol% of 2-isocyanatoethyl methacrylate based on all hydroxyl groups. 100 parts by mass (solid content ratio) of the acrylic copolymer thus obtained, and 0.19 parts by mass (solid content ratio) of a TDI isocyanate cross-linking agent (product name “BHS-8515”, manufactured by Toyochem Co., Ltd.), A photopolymerization initiator (product name “IRGACURE 184”, manufactured by BASF) 0.748 parts by mass (solid content ratio) was mixed in a solvent to prepare an acrylic pressure-sensitive adhesive coating solution.
This was applied to a release film and dried by heating to obtain a pressure-sensitive adhesive layer having a thickness of 10 μm on the release film. By sticking this to the intermediate layer obtained above, a pressure-sensitive adhesive sheet was obtained.

[Example 2]
Adhesion was performed in the same manner as in Example 1 except that a liquid butadiene polymer having a plurality of vinyl groups in the side chain (product name “Ricon154”, manufactured by Clay Valley Co., Ltd., weight average molecular weight 5200) was used as the polyfunctional compound. Got the sheet.

[Example 3]
The same procedure as in Example 1 was performed except that a bifunctional polyalkyl acrylate having a polymerizable functional group at both ends (product name “RC100C”, manufactured by Kaneka Corporation, weight average molecular weight 20000) was used as the polyfunctional compound. ..

[Examples 4 to 6]
Example 1 was carried out in the same manner as in Example 1 except that the type of polyfunctional compound, the polyfunctional compound, and the mass parts of the monofunctional monomer were changed as shown in Table 1.

[Examples 7 to 9]
In addition to stearyl acrylate as a monofunctional monomer, isobornyl acrylate (IBXA) or 2-hydroxy-3-phenoxypropyl acrylate (HPPA) is blended in the composition for the intermediate layer, and a polyfunctional compound and a monofunctional monomer are blended. Example 1 was repeated except that the amount was changed as shown in Table 1.

[Comparative Example 1]
As shown in Table 1, the same procedure as in Example 1 was performed except that a monofunctional acrylate resin (product name “MM110C”, manufactured by Kaneka Corporation, weight average molecular weight 9930) was used instead of the bifunctional urethane acrylate. did.

[Comparative example 2]
Example 1 was carried out in the same manner as in Example 1 except that the composition for intermediate layer was not blended with stearyl acrylate, and the blending amounts of the bifunctional urethane acrylate oligomer and the photopolymerization initiator were changed as shown in Table 1.

[Comparative Examples 3 and 4]
Except that in addition to stearyl acrylate as a monofunctional monomer, isobornyl acrylate (IBXA) was blended in the composition for the intermediate layer, and the blending amounts of the polyfunctional compound and the monofunctional monomer were changed as shown in Table 1. Was carried out in the same manner as in Example 1.

* In addition, in Table 1, the parts by mass of each compound are represented by the solid content. In addition, the blank column indicates that it is not blended.
* Each compound in the table is as follows.
(1) Polyfunctional compound UA: Bifunctional urethane acrylate oligomer (product name "CN9018", manufactured by Arkema)
PB: Liquid butadiene polymer (Product name "Ricon154", manufactured by Clay Valley)
PAA: Bifunctional polyalkyl acrylate (Product name "RC100C", manufactured by Kaneka Corporation)
(2) Monofunctional A
Monofunctional acrylate resin (Product name "MM110C", manufactured by Kaneka Corporation)
(3) Monofunctional monomer STA: Stearyl acrylate IBXA: Isobornyl acrylate HPPA: 2-Hydroxy-3-phenoxypropyl acrylate

In each of the above examples, the composition for intermediate layer contains at least a polyfunctional compound and a crystalline monomer, and the content of the polyfunctional compound is more than 25% by mass with respect to the monofunctional monomer, and the monofunctional monomer is contained. By using 40% by mass or more of the crystalline monomer, the bumps formed on the surface of the wafer can be properly embedded with the adhesive sheet, and no bleeding occurs when the adhesive sheet is attached to the wafer. It was
On the other hand, in Comparative Example 1, although the composition for the intermediate layer contained the crystalline monomer, since the monofunctional acrylate resin was used instead of the polyfunctional compound, the embeddability in the bump was sufficient. The exudation of the layers could not be prevented. Further, as in Comparative Examples 2 to 4, when the monofunctional monomer was not blended and the content of the polyfunctional compound was small, the embeddability in the bump was insufficient.

10A, 10B Adhesive sheet 11 Base material 12 Intermediate layer 13 Adhesive layer 14 Release material

Claims (6)

A pressure-sensitive adhesive sheet comprising a base material, an intermediate layer, and a pressure-sensitive adhesive layer in this order,
It said intermediate layer is crystalline having a weight-average molecular weight having at least two functional groups having one polyfunctional compound of from 3,000 to 60,000, a carbon chain and an ethylenic double bond with a carbon number of 1 6-2 0 linear A cured product of an intermediate layer composition containing at least a monomer and a monofunctional monomer having one ethylenic double bond,
The polyfunctional compound is at least one selected from the group consisting of a urethane (meth)acrylate oligomer, an acrylic polymer, and a butadiene polymer,
The composition for an intermediate layer contains no heat-meltable resin or contains less than 2%,
40% by mass or more of the monofunctional monomer is the crystalline monomer,
In the composition for the intermediate layer, a pressure-sensitive adhesive sheet, wherein the polyfunctional compound is contained in an amount of 25% by mass or more based on the monofunctional monomer. The pressure-sensitive adhesive sheet according to claim 1, wherein the polymerizable functional group of the polyfunctional compound is a group having an ethylenic double bond. The pressure-sensitive adhesive sheet according to claim 1 or 2 , wherein the crystalline monomer is contained in an amount of 25 to 70 mass% with respect to the total amount of the intermediate layer composition. The intermediate layer composition is, pressure-sensitive adhesive sheet according to any one of claims 1 to 3, an energy ray curable. The thickness of the intermediate layer is pressure-sensitive adhesive sheet according to any one of claims 1 to 4 which is a 150～700Myuemu. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5 which is a semiconductor wafer protective tape.

Images