CN107001872A - adhesive sheet - Google Patents

Abstract

The bonding sheet (10A) of the present invention possesses successively：Base material (11), intermediate layer (12) and adhesive phase (13), wherein, intermediate layer (12) is to solidify the intermediate layer composition containing polyfunctional compound and monofunctional monomer, the polyfunctional compound has at least two polymerizable functional group, the monofunctional monomer comprises at least the crystallinity monomer of the linear carbon chain with carbon number 14~22, in the composition of intermediate layer, contain the polyfunctional compound for being more than 25 mass % relative to the monofunctional monomer.

Description

adhesive sheet

technical field

The present invention relates to an adhesive sheet that is attached to an adherend such as a semiconductor wafer and used for protecting the adherend, and particularly relates to a backgrinding sheet.

Background technique

In the process of rapid thinning, miniaturization, and multifunctionalization of information terminal equipment, semiconductor devices mounted therein are also required to be thinner and higher in density. In order to reduce the thickness of devices, it is desired to reduce the thickness of semiconductor wafers on which semiconductors are integrated. In order to meet this demand, studies are underway to reduce the thickness of semiconductor wafers by grinding them.

In addition, in recent years, bumps made of solder or the like having a height of about 30 to 100 μm are sometimes formed on the wafer surface, and the back surface of the semiconductor wafer having irregularities is sometimes ground. When back grinding such a bumped semiconductor wafer, an adhesive sheet called a back grinding sheet is attached to the surface of the wafer on which the bumps are formed in order to protect the bump portion.

In the adhesive sheet used for the backgrinding sheet, an intermediate layer may be provided between the base material and the adhesive layer in order to embed bumps to absorb and relax the level difference on the surface of the semiconductor wafer. It is known that the storage modulus can be used for the intermediate layer in order to improve the embedment of the bump at the bonding temperature, to improve the retention performance of the wafer surface at room temperature, and to improve the shape stability when it is made into a roll. An energy ray curable resin that decreases at high temperatures and increases at room temperature.

However, when only the energy ray curable resin is used, the intermediate layer may soften excessively at the bonding temperature, causing bleeding of the intermediate layer during bonding, and the intermediate layer may not be able to sufficiently absorb the height difference of the bumps. In order to solve these problems, as disclosed in Patent Document 1, an intermediate layer formed by dispersing a crystalline heat-melt resin in a matrix resin made of an energy ray-curable resin is known.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2013-87131

Contents of the invention

The problem to be solved by the invention

However, when the crystalline heat-melt resin is dispersed in the intermediate layer as in Patent Document 1, the film-forming property of the intermediate layer may decrease. Therefore, there is a demand for an intermediate layer that can properly embed bumps without using a hot-melt resin, sufficiently alleviate the level difference, and prevent bleeding at the time of bonding.

The present invention was made in view of the above problems, and its object is to provide an adhesive sheet that can be adhered to a semiconductor wafer or the like even if the intermediate layer does not contain a crystalline hot-melt resin. In the case of an adherend, the embedding property for the unevenness formed on the adherend can be improved, and the intermediate layer can be prevented from bleeding out when sticking.

method used to solve the problem

The inventors of the present invention conducted intensive studies and found that the above-mentioned problem can be solved by forming an intermediate layer by curing a monofunctional monomer containing a crystalline monomer and a polyfunctional compound contained in a predetermined ratio or more relative to the monofunctional monomer. Problem, thus completed the following invention.

(1) An adhesive sheet comprising: a base material, an intermediate layer, and an adhesive layer in this order, wherein,

The intermediate layer is formed by curing an intermediate layer composition containing a polyfunctional compound and a monofunctional monomer, the polyfunctional compound has at least two polymerizable functional groups, and the monofunctional monomer contains at least A crystalline monomer with a linear carbon chain of 14 to 22,

The composition for an intermediate layer contains more than 25% by mass of the polyfunctional compound relative to the monofunctional monomer.

(2) The pressure-sensitive adhesive sheet according to the above (1), wherein 40% by mass or more of the monofunctional monomer is the crystalline monomer.

(3) The pressure-sensitive adhesive sheet according to the above (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) above, wherein the polymerizable functional group of the polyfunctional compound is a group having an ethylenic double bond.

(5) The adhesive sheet according to any one of the above (1) to (4), wherein the polyfunctional compound is selected from urethane (meth)acrylate oligomers, acrylic polymers and at least one of butadiene-based polymers.

(6) The pressure-sensitive adhesive sheet according to any one of (1) to (5) above, wherein the crystalline monomer is contained in an amount of 25 to 70% by mass based on the total amount of the composition for an intermediate layer. .

(7) The pressure-sensitive adhesive sheet according to any one of (1) to (6) above, wherein the composition for an intermediate layer is an energy-ray-curable composition.

(8) The pressure-sensitive adhesive sheet according to any one of (1) to (7) above, 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) above, which is an adhesive tape for semiconductor wafer protection.

Invention effect

According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet which, when sticking the pressure-sensitive adhesive sheet to an adherend such as a semiconductor wafer, can improve the embedding property of the unevenness of the adherend and can prevent sticking. The middle layer seeps out.

Description of drawings

FIG. 1 is a cross-sectional view showing an adhesive sheet according to one embodiment of the present invention.

Fig. 2 is a cross-sectional view showing an adhesive sheet according to another embodiment of the present invention.

Symbol Description

10A, 10B adhesive sheet

11 Substrate

12 middle layer

13 adhesive layer

14 Stripping material

detailed description

Hereinafter, the present invention will be described using embodiments. In addition, in the following description, "weight average molecular weight (Mw)" is the value converted into polystyrene measured by the gel permeation chromatography (GPC) method, and is specifically based on what was described in the Example The value determined by the method.

In addition, in the description in this specification, for example, "(meth)acrylate" is used as a term indicating both "acrylate" and "methacrylate", and other similar terms are handled in the same manner.

1 and 2 show a PSA sheet according to one embodiment of the present invention. As long as the adhesive sheet of the present invention is formed by providing an intermediate layer 12 on a substrate 11 and an adhesive layer 13 on the intermediate layer 12 as in the adhesive sheet 10A shown in FIG. Special restrictions. The pressure-sensitive adhesive sheet may be composed of these three layers, and another layer may be further provided. For example, like the adhesive sheet 10B shown in FIG. 2 , the release material 14 may be further provided on the adhesive layer 13 .

Hereinafter, each member which comprises an adhesive sheet is demonstrated in more detail.

[middle layer]

The intermediate layer is formed by curing an intermediate layer composition containing a polyfunctional compound and a monofunctional monomer, the polyfunctional compound has at least 2 polymerizable functional groups, and the monofunctional monomer contains at least 14 carbon atoms. A crystalline monomer with a linear carbon chain of ~22.

In the present invention, the composition for the intermediate layer that forms 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 embedding property of surface irregularities of the adherend such as bumps is good. In addition, when the pressure-sensitive adhesive sheet is attached to an adherend such as a semiconductor wafer at high temperature, bleeding of the intermediate layer can also be prevented.

The composition for the intermediate layer is cured by polymerizing the polyfunctional compound and the monofunctional monomer to form the intermediate layer. The composition for an intermediate layer is preferably an energy-ray-curable type that is cured by energy rays. It should be noted that energy rays are rays having energy quanta in electromagnetic waves or charged particle beams, and refer to active light such as ultraviolet rays or electron beams, etc., but ultraviolet rays are preferably used.

＜Multifunctional compound＞

The composition for an intermediate layer contains more than 25% by mass of a polyfunctional compound based on the total amount of monofunctional monomers. When the said content of a polyfunctional compound is 25 mass % or less, it becomes difficult to ensure embedding property. In addition, the above-mentioned content of the polyfunctional compound is preferably 30% by mass or more, more preferably 50% by mass or more. When content is 30 mass % or more, it becomes easy to make embedding property more favorable. In addition, in order to ensure the content of a monofunctional monomer to some extent, the upper limit of this content is preferably 250 mass % or less, More preferably, it is 200 mass % or less.

In addition, the polymerizable functional group contained in the polyfunctional compound is preferably a group having an ethylenic double bond. By having an ethylenic double bond, the polyfunctional compound can be cured by energy rays such as ultraviolet rays. Here, as a specific example of the group which has an ethylenic double bond, a (meth)acryloyl group, a vinyl group, etc. are mentioned, Preferably it is a (meth)acryloyl group.

The polyfunctional compound may be any of a polyfunctional monomer and a polyfunctional oligomer, and it is preferable to use a polyfunctional oligomer because the interaction with the crystalline monomer is stronger during curing. As the polyfunctional compound, one type may be used alone, or two or more types may be used in combination. When using 2 or more types of polyfunctional compounds, either 2 types of polyfunctional monomers and polyfunctional oligomers may be used, and both polyfunctional monomers and polyfunctional oligomers may be used.

(multifunctional oligomer)

The weight average molecular weight of the polyfunctional oligomer is preferably 3,000 to 60,000, more preferably 5,000 to 50,000. By setting the weight average molecular weight within the above range, the embedding property of the intermediate layer can be further improved, and bleeding of the intermediate layer can also be easily prevented. In addition, it is easy to make the film-forming property good by making the polyfunctional oligomer into a liquid state and making the viscosity into an appropriate range.

Examples of polyfunctional oligomers that can be used in the intermediate layer include, specifically, urethane (meth)acrylate oligomers, acrylic polymers, butadiene polymers, polyisoprene ene etc. Among them, urethane (meth)acrylate oligomers, acrylic polymers, and butadiene polymers are preferable. It should be noted that, as an oligomer, although a monofunctional oligomer having only one polymerizable functional group is known, in the present invention, when a monofunctional oligomer is used instead of a polyfunctional oligomer, in The middle layer is too softened at high temperature, and it is difficult to prevent the seepage of the middle layer.

Hereinafter, urethane (meth)acrylate oligomers, acrylic polymers, and butadiene-based polymers that can be used as polyfunctional oligomers will be specifically described.

"Urethane (meth)acrylate oligomers"

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 energy ray irradiation.

The number of (meth)acryloyl groups (that is, polymerizable functional groups) in the urethane (meth)acrylate oligomer may be 2 or 3 or more, preferably 2. The urethane (meth)acrylate oligomer can be obtained, for example, by reacting a (meth)acrylate having a hydroxyl group with a terminal isocyanate urethane prepolymer. The terminal isocyanate urethane prepolymer It is obtained by reacting a polyol compound with a polyisocyanate compound.

In addition, the urethane (meth)acrylate oligomer can be used individually or in combination of 2 or more types.

a. Polyol compound

A polyol compound is a compound having two or more hydroxyl groups. Specific polyol compounds include, for example, polyether polyols, polyester polyols, and polycarbonate polyols, among which polyether polyols are preferred. Polyol. In addition, as a polyol compound, any of bifunctional diol, trifunctional triol, and tetrafunctional or more polyhydric alcohol may be sufficient, and bifunctional diol is preferable.

For example, the polyether polyol is preferably a compound represented by the following formula (1).

[chemical formula 1]

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

In addition, n is the number of repeating units of alkylene oxide, and is usually 10-250, preferably 25-205, and more preferably 40-185. When n is the said range, the urethane bond density|concentration of the obtained urethane (meth)acrylate oligomer is appropriate, and it becomes easy to improve the flexibility of an intermediate layer.

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.

A polyester polyol is obtained by polycondensing a polyhydric alcohol component and a polybasic acid component. Examples of the polyol component include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 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-butyl-1,3-propanediol, 1,4-cyclohexanedimethanol, ethylene glycol or propylene glycol adducts of bisphenol A Various known diols, etc.

As a polybasic acid component used for manufacture of a polyester polyol, the 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, Aliphatic dibasic acids such as acid; dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid, polyacids such as trimellitic acid and pyromellitic acid, etc. Polybasic acids, their corresponding anhydrides, their derivatives, dimer acids, hydrogenated dimer acids, etc.

The polycarbonate polyol is not particularly limited, and polyalkylene carbonate diol is exemplified. Polyalkylene carbonate diol can enumerate: polytetramethylene carbonate diol, polypentylene carbonate diol, polyhexamethylene carbonate diol, or have be selected from tetramethylene, pentamethylene and hexamethylene A substance having a linear alkylene group having about 4 to 8 carbon atoms as a repeating unit represented by a copolymer of two or more kinds of mixed alkylene chains in a methyl group.

b. Polyisocyanate compound

Examples of the polyisocyanate compound include: aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; isophorone diisocyanate, norbornane diisocyanate; Alicyclic diisocyanates such as isocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, ω,ω'-diisocyanate dimethylcyclohexane; 4 ,4'-Diphenylmethane diisocyanate, toluene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, tetramethylene xylylene diisocyanate, naphthalene-1,5 -Aromatic diisocyanates, such as diisocyanate, etc.

Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferable from the viewpoint of handleability.

c. (meth)acrylates with hydroxyl groups

A urethane (meth)acrylate oligomer can be obtained by reacting a (meth)acrylate having a hydroxyl group with a terminal isocyanate urethane prepolymer which is It is obtained by reacting the above-mentioned polyol compound and polyisocyanate compound.

It will not specifically limit if it is a compound which has a hydroxyl group and a (meth)acryloyl group in at least 1 molecule as (meth)acrylate which has a hydroxyl group.

Specific (meth)acrylates having a hydroxyl group include, for example: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-Hydroxycyclohexyl (meth)acrylate, 5-Hydroxycyclohexyl (meth)acrylate, 2-Hydroxy-3-phenoxypropyl (meth)acrylate, Pentaerythritol tri(meth)acrylate, Polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, etc. Hydroxyalkyl (meth)acrylates; N-methylol (meth)acrylamide, etc. containing hydroxyl (methyl) Acrylamide; a reactant obtained by reacting (meth)acrylic acid with vinyl alcohol, vinylphenol, or diglycidyl ester of bisphenol A; and the like.

Among them, hydroxyalkyl (meth)acrylate is preferable, and 2-hydroxyethyl (meth)acrylate is more preferable.

"Acrylic Polymer"

Acrylic polymers used as polyfunctional compounds include polymers obtained by polymerizing (meth)acrylic acid esters, and examples include: preferably (meth)acrylic acid alkyl groups having 1 to 10 carbon atoms in the alkyl group The polymer obtained by ester polymerization is more preferably a polymer obtained by polymerizing an alkyl (meth)acrylate having 3 to 8 alkyl carbon atoms.

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, (meth)acrylate ) n-butyl acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethyl (meth) acrylate Hexyl ester etc. An acrylic polymer has a polymerizable functional group at both terminals, and the polymerizable functional group is usually a (meth)acryloyl group.

"Butadiene Polymers"

As a butadiene polymer, the polymer which has 2 or more vinyl groups in a side chain is mentioned. The side-chain vinyl group of the butadiene-based polymer is a polymerizable functional group, and can be cured by reacting with a monofunctional monomer. Butadiene-based polymers are polymers polymerized from butadiene as a monomer unit, and generally contain 1,4-bonded units and 1,2-vinyl-bonded units.

(multifunctional monomer)

In addition, examples of polyfunctional monomers usable as the polyfunctional compound include (meth)acrylic polyfunctional monomers, specifically pentaerythritol tri(meth)acrylic acid ester, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy Ethane addition glycerin (meth)acrylate, dipropylene glycol di(meth)acrylate, etc.

＜Monofunctional monomer＞

(crystalline monomer)

A monofunctional monomer is a monomer which has one ethylenic double bond. The monofunctional monomer contained in the composition for an intermediate layer includes at least a crystalline monomer. The crystalline monomer is a monomer having a straight carbon chain having 14 to 22 carbon atoms, and when the composition for an intermediate layer is polymerized by a curing reaction, it imparts crystallinity to the side chain of the polymer obtained. In the present invention, by including the crystalline monomer in the composition for the intermediate layer, the elastic modulus of the intermediate layer is lowered and deformed during heat bonding, and the embedding property can be easily improved. In addition, a crystalline monomer is a monomer which has an ethylenic double bond, and has crystallinity in a side chain through the said linear carbon chain of 14-22 carbon atoms when forming a polymer.

It is preferable that 40% by mass or more of the monofunctional monomer contained in the composition for an intermediate layer is a crystalline monomer. In the present invention, by making the crystalline monomer content 40% by mass or more, the modulus of elasticity becomes better during hot bonding, prevents bleeding of the intermediate layer during bonding of the PSA sheet, and improves embedding property.

Moreover, it is more preferable that 45-100 mass % of a monofunctional monomer is a crystalline monomer, and it is still more preferable that 77-100 mass % is a crystalline monomer. In this way, when the content of the crystalline monomer in the monofunctional monomer is increased, the reduction in the elastic modulus of the intermediate layer during heat bonding becomes significant, so that better embedding properties can be exhibited, and at the same time, Suppresses resin bleeding from the intermediate layer of the PSA sheet during storage.

The crystalline monomer is a monomer having one ethylenic double bond, and specifically, preferably has a (meth)acryloyl group or a vinyl group as a functional group, and more preferably has a (meth)acryloyl group. When the crystalline monomer has an ethylenic double bond, it can be easily polymerized by irradiation with energy rays. Moreover, it becomes easy to make hardening reaction progress smoothly by having a (meth)acryloyl group.

The crystalline monomer preferably has a linear alkyl group having 14 to 22 carbon atoms. When the crystalline monomer has such a long carbon-chain straight-chain alkyl group, crystallinity can be imparted to the side chain of the polymer obtained by curing the composition for an intermediate layer. In addition, it is more preferable that the number of carbon atoms of a linear alkyl group is 16-20.

Specific crystalline monomers include alkyl (meth)acrylates having a straight-chain alkyl group having 14 to 22 carbon atoms, alkyl vinyl ethers having a straight-chain alkyl group having 14 to 22 carbon atoms, and the like. , preferably an alkyl (meth)acrylate having a linear alkyl group having 14 to 22 carbon atoms. By using an alkyl (meth)acrylate, it becomes easy to make hardening reaction progress smoothly.

Examples of the alkyl (meth)acrylate having a linear alkyl group having 14 to 22 carbon atoms include tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, ( Octadecyl methacrylate, eicosyl (meth)acrylate, and behenyl (meth)acrylate, among them, (meth)acrylic acid is preferable from the viewpoint of easy availability and the like. octadecyl ester.

In addition, examples of the alkyl vinyl ether having a linear alkyl group having 14 to 22 carbon atoms include myristyl vinyl ether, hexadecyl vinyl ether, octadecyl vinyl ether, Decyl vinyl ether, behenyl vinyl ether, etc.

In addition, it is preferable to contain 25-70 mass % of crystalline monomers with respect to the whole composition for intermediate layers, and it is more preferable to contain 40-60 mass %. When the content is 25% by mass or more, the portion having crystallinity in the intermediate layer increases, and when this is heated to a high temperature, the elastic modulus of the intermediate layer decreases, and the embedding property tends to be improved. Moreover, when content is 70 mass % or less, it becomes easy to ensure the flexibility required as an intermediate layer.

(other monofunctional monomers)

The monofunctional monomer contained in the composition for an intermediate layer may consist of only the above-mentioned crystalline monomer, or may contain a monofunctional monomer other than the crystalline monomer.

Monofunctional monomers other than crystalline monomers are monomers containing a group having an ethylenic double bond such as a (meth)acryloyl group and a vinyl group. Specifically, (methyl) Acrylates, (meth)acrylates containing functional groups, alkyl (meth)acrylates with alkyl carbon atoms less than 14, amido-containing compounds, (meth)acrylates with aromatic structures, heterocyclic structures Among them, at least one of (meth)acrylates having an alicyclic structure and (meth)acrylates containing functional groups is preferably used.

Examples of (meth)acrylates having an alicyclic structure include: isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentyl (meth)acrylate, (meth)acrylate ) dicyclopentenyloxy acrylate, cyclohexyl (meth)acrylate, adamantyl (meth)acrylate, etc., among them, isobornyl (meth)acrylate is preferable.

As a functional group used for a functional group containing (meth)acrylate, a hydroxyl group, an amino group, an epoxy group etc. are mentioned. Specific examples of functional group-containing (meth)acrylates include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, etc. Hydroxyl-containing (meth)acrylates; primary amino-containing (meth)acrylates, secondary amino-containing (meth)acrylates, tertiary amino-containing (meth)acrylates, etc. Acrylic esters; epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether, etc. Among them, hydroxyl group-containing (meth)acrylates are preferable, and among them, 2-hydroxy-3-phenoxypropyl (meth)acrylate is more preferable.

Examples of alkyl (meth)acrylates having an alkyl group having less than 14 carbon atoms include: methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, (meth)acrylate Isopropyl acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-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.

Examples of compounds containing amide groups include: (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-methylol (methyl) ) acrylamide, N-methylolpropane (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, etc. (meth)acrylamide Amide compounds.

As (meth)acrylate which has an aromatic structure, benzyl (meth)acrylate etc. are mentioned, for example. As (meth)acrylate which has a heterocyclic structure, tetrahydrofurfuryl (meth)acrylate, morpholine acrylate, etc. are mentioned, for example. Moreover, examples of other vinyl compounds include styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylformamide, N-vinylpyrrolidone, N-vinylcaprolactam, and the like.

＜Photopolymerization Initiator＞

The composition for an intermediate layer preferably contains a photopolymerization initiator so that it can be easily cured by irradiation with active light such as ultraviolet rays.

As the photopolymerization initiator, for example: photopolymerization initiators such as benzoin compound, acetophenone compound, acyl phosphine oxide compound, titanocene compound, thioxanthone compound, peroxide compound, etc., more specifically, For example, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzene Azoin isopropyl ether, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc. In addition, depending on the types of polyfunctional compounds and monofunctional monomers, other than the above, aromatic diazonium salts, aromatic halides, Salt, aromatic sulfonium salt, etc. Cationic photopolymerization initiators such as salts, nitrobenzyl esters, sulfonic acid derivatives, phosphoric acid esters, sulfonic acid derivatives, etc., catalysts such as titanium alkoxide and p-chlorophenyl o-nitrobenzyl ether, etc. Anionic photopolymerization Initiator. A photoinitiator can be used individually or in combination of 2 or more types.

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 0.3 to 5 parts by mass, based on 100 parts by mass of the polyfunctional compound and monofunctional monomer in total. In addition, the composition for an intermediate layer may contain photosensitizers such as amines and quinones, and the like.

The composition for an intermediate layer may contain other additives within the range that does not impair the effect of the present invention. Examples of other additives include antioxidants, antistatic agents, softeners (plasticizers), fillers, antirust agents, pigments, and dyes.

In addition, it is preferable that the composition for an intermediate layer does not substantially contain a heat-melt resin. By making the composition for an intermediate layer of the present invention contain a crystalline monomer component, even if it does not substantially contain a heat-melt resin, it is possible to prevent bleeding of the intermediate layer at the time of sticking and to improve embedding properties. It should be noted that the hot-melt resin is a resin in which a clear and sharp melting peak is observed in DSC measurement, specifically, the difference between the melting start temperature and the melting peak temperature (melting point (Tm)) is 8° C. or less , and, for example, a resin having a melting point (Tm) of 45 to 90°C. Examples of the hot-melt resin include waxy acrylic polymers at room temperature, polymers of α-olefins having 14 to 30 carbon atoms, and the like.

It should be noted that the composition for an intermediate layer may contain a thermally meltable resin to the extent that it does not affect the film-forming properties of the intermediate layer when substantially not containing a thermally meltable resin. The total amount of the composition for an intermediate layer contains less than 2% by mass of the hot-melt resin, preferably less than 1% by mass, and more preferably not contained. By substantially not containing a hot-melt resin, it is possible to suppress the occurrence of aggregation and increase in viscosity due to the solid polymer material in the composition for an intermediate layer.

The composition for the intermediate layer usually contains the above-mentioned polyfunctional compound and monofunctional monomer as main components, and the total amount thereof is usually 70% by mass or more, preferably 80% by mass or more, more preferably 80% by mass or more, based on the total amount of the composition for the intermediate layer. Preferably it is 90% by mass or more. In addition, the total amount of them may be 100% by mass or less based on the total amount of the composition for an intermediate layer, and is preferably 99.9% by mass or less, more preferably 99.7% by mass or less, for blending additives such as a photopolymerization initiator. In addition, the total amount of the composition for an intermediate|middle layer means the quantity which removed the volatile components, such as the dilution solvent, when the composition was diluted with the solvent etc. which volatilized in the manufacturing process.

The thickness of the intermediate layer can be appropriately adjusted according to the height of bumps and the like to be protected, but 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 high bumps and a relative level difference can be properly protected. In addition, when the thickness is 700 μm or less, deformation caused when the pressure-sensitive adhesive sheet is bent can be reduced.

[Substrate]

The substrate used for the pressure-sensitive adhesive sheet is not particularly limited, but is preferably a resin film. Compared with paper and non-woven fabrics, resin films generate less dust, so they are suitable for processing members of electronic components and are easy to obtain, so they are preferable. The substrate may be a single-layer film formed of one type of resin film, or a multi-layer film in which a plurality of resin films are laminated.

As the resin film used as the substrate, for example: polyolefin film, vinyl halide polymer film, acrylic resin film, rubber film, cellulose film, polyester film, polycarbonate film, Polystyrene film, polyphenylene sulfide film, cycloolefin polymer film, etc.

Among them, polyester-based films are preferred from the viewpoint of stably holding the wafer even when the wafer is ground to an extremely thin thickness, and from the viewpoint of forming a film with high thickness accuracy. From the viewpoint of high precision, a polyethylene terephthalate film is preferable.

Moreover, the thickness of a base material is not specifically limited, Preferably it is 10-250 micrometers, More preferably, it is 20-200 micrometers.

In addition, from a viewpoint of improving the adhesiveness of a base material and an intermediate|middle layer, the base material which laminated|stacked an easily bonding layer etc. further on the surface of a resin film can be used. In addition, fillers, colorants, antistatic agents, antioxidants, organic lubricants, catalysts, and the like may be contained in the substrate within the range that does not impair the effects of the present invention.

The substrate may be a transparent substrate or an opaque substrate. Among them, when the adhesive constituting the adhesive layer and the composition for the intermediate layer are energy-ray-curable, the substrate is preferably a substrate that transmits energy rays.

[adhesive layer]

Examples of the adhesive forming the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, polyvinyl ether adhesives, and urethane adhesives. Among them, an acrylic adhesive is preferable. In addition, examples of adhesives include: energy ray curing type, energy ray foaming type adhesives, heat foaming type, water swelling type adhesives, among them, energy ray curing type or electron beam curing type are preferred. The line-curable adhesive is more preferably an ultraviolet-curable adhesive.

By using an energy ray-curable adhesive, the adhesive sheet can be reliably bonded to the semiconductor wafer before energy ray irradiation, and an adherend such as a semiconductor wafer can be reliably protected. On the other hand, since the adhesive force of the adhesive layer can be reduced by irradiating energy rays when the adhesive sheet is peeled off, the adhesive sheet can be peeled off from the adherend without causing damage to the adherend such as a semiconductor wafer. , and does not leave adhesive residue on the adherend.

The energy ray-curable adhesive may be an additive-type energy ray-curable adhesive containing a base polymer such as an acrylic copolymer and an energy ray-curable resin, or it may be an adhesive that will be incorporated in the side chain or main chain of the polymer or A so-called intrinsic energy ray-curable adhesive that uses a polymer having a radically reactive carbon-carbon double bond at the end of the main chain as a base polymer such as an acrylic copolymer.

In addition, an adhesive contains not only base polymers, such as an acryl-type copolymer, but may contain a crosslinking agent, a photoinitiator, etc. as needed.

The thickness of the adhesive layer can be adjusted according to the height difference on the surface of the adherend such as a semiconductor wafer, the performance required for the adhesive sheet, etc., and is usually 3 to 200 μm, preferably 7 to 150 μm, more preferably 10 to 100 μm .

[peeling material]

The above-mentioned release material constituting the pressure-sensitive adhesive sheet and the release material used in the steps of the production method described below can use a release sheet that has undergone a single-side release treatment, a release sheet that has undergone a double-side release treatment, and the like. The base material of the release material is coated with a release agent or the like.

Examples of the base material for the release material include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, polypropylene Resin, plastic films such as polyolefin resin films such as polyethylene resins, etc.

Examples of release agents include rubber-based elastomers such as polysiloxane-based resins, olefin-based resins, isoprene-based resins, and butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, Fluorine resin, etc.

In addition, the thickness of the release material is not particularly limited, but is preferably 5 to 200 μm, more preferably 10 to 120 μm.

[Manufacturing method of adhesive sheet]

The method for producing the PSA sheet of the present invention is not particularly limited, and the PSA sheet can be produced by a known method.

For example, the intermediate layer can be formed by directly coating the composition for the intermediate layer on one surface of the substrate to form a coating film, followed by curing. In addition, the intermediate layer can also be formed by directly applying the composition for the intermediate layer on the release-treated surface of the release material, performing curing treatment, and bonding the base material to the coating film. In this case, for example, the peeling material can be peeled appropriately after the curing treatment is completed or the like. In addition, it is preferable to irradiate energy rays, such as an ultraviolet-ray, to the formed coating film, and to polymerize and harden the hardening of an intermediate layer. At this time, the irradiation amount of energy rays can be appropriately changed according to 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 . In addition, the light quantity of ultraviolet rays is preferably 100 to 2500 mJ/cm ² .

In addition, 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 adhesive composition can be applied to the release-treated surface of the release material, dried to form an adhesive layer on the release material, and then the adhesive layer on the release material can be bonded to the intermediate layer. , forming an adhesive sheet provided with an intermediate layer, an adhesive layer, and a release material on a substrate. Then, the release material in the pressure-sensitive adhesive sheet can be peeled as necessary.

When forming the intermediate layer or the adhesive layer, an organic solvent may be further blended into the intermediate layer composition or the adhesive composition to prepare a diluted solution of the intermediate layer composition or the adhesive composition.

As the organic solvent used, for example: methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dihydrofuran, alkanes, cyclohexane, n-hexane, toluene, xylene, n-propanol, isopropanol, etc.

As these organic solvents, the organic solvents used in the synthesis of the components contained in the intermediate layer composition or the adhesive composition may be used as they are, or one or more other organic solvents may be added thereto.

The composition for an intermediate layer or the adhesive composition can be applied by a known coating method. Examples of coating methods include spin coating, spray coating, bar coating, blade coating, roll coating, blade coating, die coating, and gravure coating.

In addition, when an organic solvent is blended in the composition for an intermediate layer or the adhesive composition, it is preferable to heat and dry it after coating.

[How to use the adhesive sheet]

The pressure-sensitive adhesive sheet of the present invention can be used in various applications, and is preferably used as a semiconductor wafer protective tape by sticking to a semiconductor wafer. In addition, it is more preferable that the pressure-sensitive adhesive sheet is attached to the surface of the semiconductor wafer and used as a back grinding tape for protecting a circuit formed on the surface of the wafer during subsequent wafer back grinding.

Since the pressure-sensitive adhesive sheet of the present invention has good embedability even when there is a difference in height due to bumps or the like on the wafer surface, the protection performance of the wafer surface becomes good. In addition, although the adhesive sheet is heated when the adhesive sheet is attached to the wafer, bleeding of the intermediate layer does not occur even if the adhesive sheet is heated and attached.

It should be noted that the height of the bumps formed on the surface of the wafer is not particularly limited, and the embedding of bumps of various heights can be made by appropriately selecting the thickness of the intermediate layer and the adhesive layer of the adhesive sheet of the present invention. Good penetration.

In addition, the temperature of the pressure-sensitive adhesive sheet when sticking the pressure-sensitive adhesive sheet to the semiconductor wafer is, for example, about 40 to 80°C, preferably 50 to 60°C.

In addition, the adhesive sheet is not limited to a back grinding sheet, and it can also be used for other purposes. For example, an adhesive sheet is attached to the back surface of the wafer and can be used as a dicing sheet for protecting the back surface of the wafer when dicing the wafer.

Example

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

The measurement methods and evaluation methods in the present invention are as follows.

[Weight average molecular weight (Mw)]

Using a gel permeation chromatography device (product name "HLC-8020", manufactured by Tosoh Corporation), the measurement was performed under the following conditions, and the values converted to standard polystyrene were used.

(measurement conditions)

Column: "TSK guard column HXL-H", "TSK gel GMHXL(×2)", "TSK gel G2000HXL" (all manufactured by Tosoh Corporation)

Column temperature: 40°C

Elution solvent: tetrahydrofuran

Flow rate: 1.0mL/min

[embedded evaluation]

After peeling off the release material, the adhesive sheets produced in Examples and Comparative Examples were attached to a tape with a bump height of 80 μm, a pitch of 200 μm, and a diameter of 100 μm using a laminator RAD-3510F/12 manufactured by Lintec Corporation. A bumped wafer (8-inch wafer manufactured by Waltz Corporation). It should be noted that, at the time of pasting, the lamination table of the apparatus was set at 60°C, and the lamination roller was set at 60°C. After lamination, the diameter of the circular void generated near the bump was measured from the substrate side using a digital optical microscope (product name "VHX-1000", manufactured by KEYENCE Corporation). The smaller the diameter of the void, the higher the embedding property in the bump by the adhesive sheet. The embedding properties of the bumps were evaluated according to the following criteria. The results are shown in Table 1.

A: The diameter of voids is less than 120 μm.

B: The diameter of the void is 120 μm to 130 μm.

C: Bubbles are connected to adjacent bumps.

[oozing evaluation]

A 25 mm x 50 mm adhesive sheet was laminated on the silicon mirror wafer. As lamination conditions, the same conditions as those used for embedding evaluation were used. Visual observation was performed after lamination, and the case where there was no interlayer resin oozing out was rated as A, and the case where bleeding out was confirmed was rated as C.

[Example 1]

(formation of middle layer)

40 parts by mass (solid content ratio) of a bifunctional urethane acrylate oligomer (product name "CN9018", manufactured by Arkema Corporation, weight average molecular weight: 45,000) as a polyfunctional compound, and acrylic acid as a crystalline monomer 60 parts by mass of octaalkyl ester (STA) (solid content ratio), and 2,4,6-trimethylbenzoyl diphenylphosphine oxide (product name " DAROCUR TPO ", BASF company Production) 2.0 parts by mass (solid content ratio) were mixed to obtain a UV-curable composition for an intermediate layer. The composition for the intermediate layer was coated on a release film of polyethylene terephthalate (PET) film (product name "SP-PET381031", Lintec Co., Ltd. Co., Ltd., thickness 38 μm), a coating film was formed so that the thickness after curing was 200 μm.

Then, the coating film was cured by irradiating ultraviolet rays from the coating film side, and a substrate formed of a polyethylene terephthalate (PET) film with a thickness of 50 μm was laminated on the coating film to form a thickness of 200 μm intermediate layer. As the ultraviolet irradiation device, a conveyor-type ultraviolet irradiation apparatus (product name "ECS-401GX", manufactured by Eyegraphics Corporation) was used, and a high-pressure mercury lamp (product name "H04-L41", manufactured by Eyegraphics Corporation) was used as the ultraviolet source. , as irradiation conditions, ultraviolet irradiation was carried out under conditions of light wavelength 365nm, illuminance 190mW/cm ² , light intensity 113mJ/cm ² (measured with an ultraviolet light meter (product name "UVPF-A1", manufactured by Eyegraphics Co., Ltd.)).

(Formation of Adhesive Sheet)

100 parts by mass (solid content ratio) of an acrylic copolymer, 0.19 parts by mass (solid content ratio) of a TDI-based isocyanate crosslinking agent (product name "BHS-8515", manufactured by TOYOCHEM Corporation) and a photopolymerization initiator (product name "IRGACURE184 ", manufactured by BASF Corporation) 0.748 parts by mass (solid content ratio) were mixed in a solvent to prepare an acrylic adhesive coating solution in which the acrylic copolymer contained 50 mol% of methyl groups relative to all hydroxyl groups. It was obtained by reacting 2-isocyanatoethyl acrylate with a copolymer (Mw: 1.3 million) of 94% by mass of 2-ethylhexyl acrylate and 6% by mass of 2-hydroxyethyl acrylate.

This was applied to a release film and heated and dried to obtain an adhesive layer with a thickness of 10 μm on the release film. A pressure-sensitive adhesive sheet was obtained by bonding this to the intermediate layer obtained above.

[Example 2]

As a multifunctional compound, a liquid butadiene polymer (product name "Ricon 154", manufactured by Crayvalley Co., Ltd., weight average molecular weight 5200) having a plurality of vinyl groups in the side chain was used, except that it was carried out in the same manner as in Example 1, An adhesive sheet was obtained.

[Example 3]

As the polyfunctional compound, a bifunctional polyalkylacrylate (product name "RC100C", manufactured by Kaneka Co., Ltd., weight average molecular weight: 20,000) having polymerizable functional groups at both ends was used, except that it was the same as in Example 1. implemented.

[Embodiments 4-6]

As shown in Table 1, it implemented similarly to Example 1 except having changed the kind of polyfunctional compound, and the mass parts of a polyfunctional compound and a monofunctional monomer.

[Embodiments 7-9]

As a monofunctional monomer, not only octadecyl acrylate but also isobornyl acrylate (IBXA) or 2-hydroxy-3-phenoxypropyl acrylate (HPPA) are blended in the composition for the intermediate layer, And as shown in Table 1, it implemented similarly to Example 1 except having changed the compounding quantity of a polyfunctional compound and a monofunctional monomer.

[Comparative example 1]

As shown in Table 1, a monofunctional acrylate resin (product name "MM110C", manufactured by Kaneka Co., Ltd., weight average molecular weight 9930) was used instead of a bifunctional urethane acrylate, and the same procedure as in Example 1 was performed. implement.

[Comparative example 2]

Except that stearyl acrylate was not blended in the composition for the intermediate layer, and the compounding amounts of the bifunctional urethane acrylate oligomer and the photopolymerization initiator were changed as shown in Table 1, the same as in the implementation Example 1 was implemented in the same manner.

[Comparative example 3, 4]

As a monofunctional monomer, not only stearyl acrylate but also isobornyl acrylate (IBXA) was blended into the composition for the intermediate layer, and the polyfunctional compound and monofunctional monomer were changed as shown in Table 1. Except the compounding quantity of , it implemented similarly to Example 1.

Table 1

*In addition, in Table 1, the mass part of each compound is shown by the solid content amount. In addition, an empty column indicates that there is no cooperation.

※Each compound in the table is as follows.

(1) Multifunctional compound

UA: Bifunctional urethane acrylate oligomer (product name "CN9018", manufactured by Arkema Corporation)

PB: Liquid butadiene polymer (product name "Ricon 154", manufactured by Crayvalley Corporation)

PAA: Bifunctional polyalkyl acrylate (product name "RC100C", manufactured by Kaneka Co., Ltd.)

(2) Monofunctional A

Monofunctional acrylate resin (product name "MM110C", manufactured by Kaneka Co., Ltd.)

(3) Monofunctional monomer

STA: Octadecyl Acrylate

IBXA: Isobornyl Acrylate

HPPA: 2-Hydroxy-3-phenoxypropyl acrylate

In each of the above embodiments, the composition for the intermediate layer contains at least a polyfunctional compound and a crystalline monomer, and relative to the monofunctional monomer, the content of the polyfunctional compound is greater than 25% by mass, and the content of the monofunctional monomer is 40% by mass. The above is a crystalline monomer, so that the bumps formed on the surface of the wafer can be appropriately embedded with the adhesive sheet, and bleeding does not occur when the adhesive sheet is attached to the wafer.

In contrast, in Comparative Example 1, although the composition for the intermediate layer contained a crystalline monomer, a monofunctional acrylate resin was used instead of a polyfunctional compound, so although the embedding property into bumps was sufficient, Exudation of the interlayer cannot be prevented. In addition, as in Comparative Examples 2 to 4, when no monofunctional monomer was blended or when the content of the polyfunctional compound was small, the embedding property in the bump was insufficient.

Claims (9)

1. a kind of bonding sheet, it possesses successively：Base material, intermediate layer and adhesive phase, wherein,

The intermediate layer is to solidify the intermediate layer composition containing polyfunctional compound and monofunctional monomer, described Polyfunctional compound has at least two polymerizable functional group, and the monofunctional monomer, which is comprised at least, has carbon number 14~22 Linear carbon chain crystallinity monomer,

In the intermediate layer composition, containing described multiple functionalized more than 25 mass % relative to the monofunctional monomer Compound.

2. bonding sheet according to claim 1, wherein, 40 mass % of the monofunctional monomer are above is the crystallinity Monomer.

3. bonding sheet according to claim 1 or 2, wherein, the polyfunctional compound is weight average molecular weight for 3000~ 60000 multifunctional oligomer.

4. according to bonding sheet according to any one of claims 1 to 3, wherein, the polymerism function of the polyfunctional compound Group is the group with olefinic double bond.

5. according to bonding sheet according to any one of claims 1 to 4, wherein, the polyfunctional compound is selected from amino first It is at least one kind of in acid esters (methyl) acrylate oligomer, acrylic polymer and butadiene polymer.

6. according to bonding sheet according to any one of claims 1 to 5, wherein, relative to the intermediate layer total composition, The crystallinity monomer containing 25~70 mass %.

7. according to bonding sheet according to any one of claims 1 to 6, wherein, the intermediate layer is that energy line is consolidated with composition Change type.

8. according to bonding sheet according to any one of claims 1 to 7, wherein, the thickness in the intermediate layer is 150~700 μm.

9. according to bonding sheet according to any one of claims 1 to 8, it is semiconductor wafer protection adhesive tape.