KR102460037B1 - Pressure-sensitive adhesive sheet - Google Patents

Abstract

The pressure-sensitive adhesive sheet 10A of the present invention is a pressure-sensitive adhesive sheet including a base material 11, an intermediate layer 12, and an pressure-sensitive adhesive layer 13 in this order, wherein the intermediate layer 12 has at least two polymerizable functional groups. A composition for an intermediate layer comprising a compound and a monofunctional monomer containing at least a crystalline monomer having a straight-chain carbon number of 14 to 22 carbon atoms is cured, and in the composition for an intermediate layer, the polyfunctional compound is added to the monofunctional monomer It contains more than 25 mass % with respect to.

Description

Adhesive sheet {PRESSURE-SENSITIVE ADHESIVE SHEET}

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a pressure-sensitive adhesive sheet that is attached to an adherend such as a semiconductor wafer and is used to protect the adherend, and more particularly to a back grind sheet.

While thinning, miniaturization, and multifunctionalization of information terminal devices are rapidly progressing, semiconductor devices mounted thereon are similarly required to be thin and dense. In order to reduce the thickness of the device, it is desired to reduce the thickness of the semiconductor wafer on which the semiconductor is integrated. In order to respond to the request, the back surface of a semiconductor wafer is ground and thinned is performed.

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

In the adhesive sheet used for a back grind sheet, an intermediate|middle layer may be provided between a base material and an adhesive layer in order to bury bump and absorb and relieve|moderate the height difference of the semiconductor wafer surface. The intermediate layer has a low storage modulus at high temperature and high at room temperature, in order to improve the embedding of bumps at the adhesion temperature, improve the holding performance of the wafer surface at room temperature, and increase the shape stability when the intermediate layer is made into a roll. is known to be used.

However, only when an energy ray-curable resin is used, the intermediate layer is excessively softened at the adhesion temperature, and exudation of the intermediate layer may occur at the time of adhesion. In some cases. In order to solve these problems, the intermediate|middle layer which disperse|distributed the thermally meltable resin which has crystallinity in the matrix resin containing energy-beam curable resin is also known as disclosed by patent document 1.

Japanese Patent Laid-Open No. 2013-87131

However, like Patent Document 1, when a thermally meltable resin having crystallinity is dispersed in an intermediate layer, the film formability of the intermediate layer may be lowered. Therefore, even if it does not use a heat-meltable resin, while being able to fully relieve a height difference by filling a bump appropriately, the intermediate|middle layer which can prevent the seepage at the time of adhesion is calculated|required.

The present invention has been made in view of the above problems, and even if the intermediate layer does not contain a thermally fusible resin having crystallinity, when it is adhered to an adherend such as a semiconductor wafer, the embedding property to the unevenness formed on the adherend is improved. An object of the present invention is to provide an adhesive sheet capable of preventing seepage of the intermediate layer during adhesion.

As a result of earnest examination, the present inventors found that the above problems can be solved 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. and completed the following inventions.

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

The intermediate layer is a polyfunctional compound having at least two polymerizable functional groups, and a monofunctional monomer containing at least a crystalline monomer having a straight-chain carbon number of 14 to 22 carbon atoms is cured of a composition for an intermediate layer,

The said composition for intermediate|middle layer WHEREIN: The adhesive sheet in which the said polyfunctional compound contains more than 25 mass % with respect to the said monofunctional monomer.

(2) The adhesive sheet as described in said (1) whose 40 mass % or more of the said monofunctional monomer is the said 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 3000 to 60000.

(4) The 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) The adhesive sheet according to any one of (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.

(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% 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), wherein the composition for an intermediate layer is an energy ray-curable type.

(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 adhesive sheet in any one of said (1)-(8) which is a tape for semiconductor wafer protection.

In the present invention, when the pressure-sensitive adhesive sheet is attached to an adherend such as a semiconductor wafer, it is possible to provide a pressure-sensitive adhesive sheet capable of preventing the seepage of the intermediate layer during adhesion while improving the embedding property of the adherend to irregularities. .

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the adhesive sheet which concerns on one Embodiment of this invention.
2 : is sectional drawing which shows the adhesive sheet which concerns on another one Embodiment of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated using embodiment. In addition, in the following description, "weight average molecular weight (Mw)" is a polystyrene conversion value measured by the gel permeation chromatography (GPC) method, It is a value specifically measured based on the method described in the Example.

In addition, description in this specification WHEREIN: For example, "(meth)acrylate" is used as a term 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, like the pressure-sensitive adhesive sheet 10A shown in FIG. 1 , an intermediate layer 12 is provided on a base material 11 , and a pressure-sensitive adhesive layer 13 is further provided on the intermediate layer 12 . If it is, there is no particular limitation. The adhesive sheet may be comprised by these three layers, and another layer may be provided further. For example, like the adhesive sheet 10B shown in FIG. 2, on the adhesive layer 13, you may have the peeling material 14 further.

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

[middle floor]

The intermediate layer is obtained by curing 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.

In this invention, since the composition for intermediate|middle layer which forms an intermediate|middle layer contains a polyfunctional compound and a monofunctional monomer, and at least a part of monofunctional monomer is a crystalline monomer, an adhesive sheet is to-be-adhered, such as a bump of a semiconductor wafer. The embedding property with respect to the unevenness|corrugation of the surface can be made favorable. Moreover, when affixing an adhesive sheet to to-be-adhered bodies, such as a semiconductor wafer, under high temperature, it also becomes possible to prevent seeping of an intermediate|middle layer.

The composition for an intermediate|middle layer hardens|cures by superposing|polymerizing a polyfunctional compound and a monofunctional monomer, and forms an intermediate|middle layer. It is preferable that the composition for intermediate|middle layer is an energy-beam hardening type hardened|cured with an energy-beam. In addition, although an energy beam has an energy proton among an electromagnetic wave or a charged particle beam, and refers to actinic light, such as an ultraviolet-ray, an electron beam, etc., it is preferable to use an ultraviolet-ray.

<Polyfunctional compound>

The polyfunctional compound is contained more than 25 mass % with respect to monofunctional monomer whole quantity in the composition for intermediate|middle layers. As for a polyfunctional compound, when the said content will be 25 mass % or less, it will become difficult to ensure embedding property. Moreover, the said content of a polyfunctional compound becomes like this. Preferably it is 30 mass % or more, More preferably, it is 50 mass % or more. When content will be 30 mass % or more, it will become easy to make embedding property more favorable. Moreover, in order to ensure content of a monofunctional monomer to some extent, as for the upper limit of this content, Preferably it is 250 mass % or less, More preferably, it is 200 mass % or less.

Moreover, it is preferable that the polymerizable functional group contained in a polyfunctional compound is group which has an ethylenic double bond. By having an ethylenic double bond, hardening by energy rays, such as an ultraviolet-ray, becomes possible for a polyfunctional compound. Here, although a (meth)acryloyl group, a vinyl group, etc. are mentioned as a specific example of group which has an ethylenic double bond, A (meth)acryloyl group is preferable.

Although any of a polyfunctional monomer and a polyfunctional oligomer may be sufficient as a polyfunctional compound, since interaction with a crystalline monomer becomes a stronger thing when hardened|cured, it is preferable to use a polyfunctional oligomer. As a polyfunctional compound, you may use individually by 1 type, and may use it in combination of 2 or more type. When using 2 or more types of polyfunctional compounds, either 2 types of either a polyfunctional monomer and a polyfunctional oligomer may be used, and both a polyfunctional monomer and a polyfunctional oligomer may be used.

(polyfunctional oligomer)

It is preferable that the weight average molecular weights are 3000-60000, and, as for a polyfunctional oligomer, it is more preferable that it is 5000-50000. By making the weight average molecular weight into the above range, it becomes easy to prevent also exudation of an intermediate|middle layer, making embedding property of an intermediate|middle layer more favorable. Moreover, while the polyfunctional oligomer is liquid, its viscosity is in an appropriate range, and it becomes easy to improve film-forming properties.

As a polyfunctional oligomer which can be used for an intermediate|middle layer, a urethane (meth)acrylate oligomer, an acrylic polymer, a butadiene polymer, polyisoprene etc. are mentioned specifically,. Among these, a urethane (meth)acrylate oligomer, an acrylic polymer, and a butadiene polymer are preferable. In addition, as the oligomer, a monofunctional oligomer having only one polymerizable functional group is also known. However, in the present invention, when a monofunctional oligomer is used instead of a polyfunctional oligomer, the intermediate layer becomes too soft under high temperature, and it is difficult to prevent seepage of the intermediate layer. lose

Hereinafter, urethane (meth)acrylate oligomers, acrylic polymers, and butadiene polymers that can be used for polyfunctional oligomers will be described in detail.

<< Urethane (meth)acrylate oligomer >>

A urethane (meth)acrylate oligomer is a compound which has at least a (meth)acryloyl group and a urethane bond, and has the property of superposing|polymerizing by energy-beam irradiation.

Although two or three or more may be sufficient as the number of (meth)acryloyl groups (that is, polymerizable functional group) in a urethane (meth)acrylate oligomer, it is preferable that it is two. A urethane (meth)acrylate oligomer can be obtained by making the (meth)acrylate which has a hydroxyl group react with the terminal isocyanate urethane prepolymer obtained by making a polyol compound and a polyhydric isocyanate compound react, for example.

In addition, a urethane (meth)acrylate oligomer may be used individually or in combination of 2 or more type.

a. polyol compounds

The polyol compound is a compound having two or more hydroxyl groups, and specific examples of the polyol compound include polyether-type polyols, polyester-type polyols, polycarbonate-type polyols and the like. Among these, polyether-type polyols This is preferable. Moreover, although any of a bifunctional diol, a trifunctional triol, and a tetrafunctional or more than a polyol may be sufficient as a polyol compound, a bifunctional diol is preferable.

For example, as for a polyether type polyol, the compound represented by following formula (1) is preferable.

In said formula (1), although R is a divalent hydrocarbon group, an alkylene group is preferable and a C1-C6 alkylene group is more preferable. Among the C1-C6 alkylene group, an ethylene group, a propylene group, and a tetramethylene group are preferable, and a propylene group and a tetramethylene group are more preferable.

Moreover, n is the number of repeating units of an alkylene oxide, and although it is 10-250 normally, Preferably it is 25-205, More preferably, it is 40-185. When n is the said range, the urethane bond density|concentration of the urethane (meth)acrylate oligomer obtained can be made moderate, and it will become easy to raise the flexibility of an intermediate|middle layer.

Among the compounds represented by the formula (1), polyethylene glycol, polypropylene glycol and polytetramethylene glycol are preferable, and polypropylene glycol and polytetramethylene glycol are more preferable.

A 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-butyl and various known glycols such as -1,3-propanediol, 1,4-cyclohexanedimethanol, and ethylene glycol or propylene glycol adduct of bisphenol A.

As a polybasic acid component used for manufacture of a polyester-type polyol, the compound generally known as a polybasic acid component of polyester can be used.

Specific examples of the polybasic acid component include aliphatic dibasic acids such as adipic acid, maleic acid, succinic acid, oxalic acid, fumaric acid, malonic acid, glutaric acid, pimelic acid, azelaic acid, sebacic acid, and suberic acid; 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; corresponding anhydrides and derivatives thereof; dimer acid; hydrogen Addition dimer acid etc. are mentioned.

Although the polycarbonate type polyol is not specifically limited, Polyalkylene carbonate diol is illustrated. The polyalkylene carbonate diol is polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyhexamethylene carbonate diol, or a mixed alkyl of two or more types selected from tetramethylene, pentamethylene and hexamethylene. What has a C4-C8 linear alkylene group as a repeating unit is mentioned as a C4-8 exemplified copolymer etc. which have a ren chain.

b. Polyvalent Isocyanate Compounds

As a polyhydric isocyanate compound, For example, Aliphatic polyisocyanate, such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethyl hexamethylene diisocyanate; Alicyclic type such as isophorone diisocyanate, norbornane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, ω,ω'-diisocyanate dimethylcyclohexane diisocyanates; Aromatic diisocyanates, such as 4,4'- diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, tetramethylene xylylene diisocyanate, and naphthalene-1,5-diisocyanate, etc. are mentioned. have.

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

c. (meth)acrylate having a hydroxyl group

A urethane (meth)acrylate oligomer can be obtained by making the (meth)acrylate which has a hydroxyl group react with the terminal isocyanate urethane prepolymer obtained by making the polyol compound mentioned above and a polyhydric isocyanate compound react.

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.

As (meth)acrylate which has a specific hydroxyl group, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxy Oxycyclohexyl (meth) acrylate, 5-hydroxycyclooctyl (meth) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, pentaerythritol tri (meth) acrylate, polyethylene glycol mono hydroxyalkyl (meth)acrylates such as (meth)acrylate and polypropylene glycol mono(meth)acrylate; Hydroxyl group-containing (meth)acrylamide, such as N-methylol (meth)acrylamide; The reaction product obtained by making (meth)acrylic acid react with the diglycidyl ester of vinyl alcohol, vinyl phenol, and bisphenol A, 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 (meth)acrylic acid ester, preferably alkyl (meth) having 1 to 10 carbon atoms in the alkyl group, and more preferably 3 to 8 carbon atoms in the alkyl group. What polymerized the acrylate is mentioned.

Here, the alkyl group in alkyl (meth)acrylate may be branched or linear may be sufficient as it. 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, etc. are mentioned. The acrylic polymer has a polymerizable functional group at both terminals, and the polymerizable functional group is usually a (meth)acryloyl group.

<<Butadiene-Based Polymer>>

Examples of the butadiene polymer include those having two or more vinyl groups in the side chain. In this butadiene-type polymer, the vinyl group of a side chain becomes a polymerizable functional group, and it can react with a monofunctional monomer and harden|cure. A butadiene-type polymer is what polymerized|polymerized using butadiene as a monomer unit, and contains a 1, 4 bond unit and a 1,2 vinyl bond unit normally.

(polyfunctional monomer)

In addition, as the polyfunctional monomer usable as the polyfunctional compound, for example, (meth) acrylic acid-based polyfunctional monomer is mentioned, (meth) acrylic acid-based polyfunctional monomer is specifically pentaerythritol tri (meth) acrylic rate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropanetetra(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)

A monofunctional monomer is a monomer which has one ethylenic double bond. The monofunctional monomer contained in the composition for intermediate|middle layer contains a crystalline monomer at least. A crystalline monomer is what has a C14-C22 linear carbon chain, and, when superposing|polymerizing the composition for intermediate|middle layer by hardening reaction, it provides crystallinity to the side chain of the obtained polymer. In the present invention, when the composition for an intermediate layer contains a crystalline monomer, the elastic modulus of the intermediate layer is lowered and deformed at the time of heating and adhesion, and it becomes easy to improve embedding property. In addition, a crystalline monomer is a monomer which has an ethylenic double bond and has crystallinity in a side chain by the said linear C14-C22 carbon chain when it is set as a polymer.

It is preferable that 40 mass % or more of the monofunctional monomer contained in the composition for intermediate|middle layer becomes a crystalline monomer. In this invention, when a crystalline monomer becomes 40 mass % or more, the elasticity modulus becomes more favorable at the time of heat bonding, and it becomes possible to make embedding property favorable, preventing the seepage of the intermediate|middle layer at the time of sticking an adhesive sheet. .

Moreover, it is more preferable that 45-100 mass % of the monofunctional monomers are 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 decrease in the elastic modulus of the intermediate layer at the time of heating and adhesion becomes remarkable, so that better embedding properties can be expressed, and the intermediate layer of the pressure-sensitive adhesive sheet during storage It becomes possible to suppress the seepage of resin from the.

A crystalline monomer has one ethylenic double bond, Specifically, it is preferable to have a (meth)acryloyl group or a vinyl group as a functional group, and it is more preferable to have a (meth)acryloyl group. By having an ethylenic double bond, a crystalline monomer becomes superposable|polymerizable by irradiation of an energy-beam easily. Moreover, it becomes easy to advance hardening reaction easily by having a (meth)acryloyl group.

It is preferable that a crystalline monomer has a C14-C22 linear alkyl group. When a crystalline monomer has such a long straight-chain alkyl group, it becomes possible to provide crystallinity to the side chain of the polymer obtained by hardening|curing the composition for intermediate|middle layer. Moreover, as for carbon number of a linear alkyl group, it is more preferable that it is 16-20.

Specific examples of the crystalline monomer include alkyl (meth) acrylate having a straight-chain alkyl group having 14 to 22 carbon atoms, and alkylvinyl ether having a straight-chain alkyl group having 14 to 22 carbon atoms. (meth)acrylates are preferred. By using an alkyl (meth)acrylate, it becomes easy to advance hardening reaction favorably.

Examples of the alkyl (meth) acrylate having a straight-chain alkyl group having 14 to 22 carbon atoms include myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, arachidyl (meth) acrylate, and be Although henyl (meth)acrylate is mentioned, From a viewpoint, such as availability, among these, stearyl (meth)acrylate is preferable.

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, arachidyl vinyl ether, and behenyl vinyl ether.

Moreover, it is preferable to contain 25-70 mass % with respect to the composition whole quantity for intermediate|middle layers, and, as for a crystalline monomer, it is more preferable to contain 40-60 mass %. When content is 25 mass % or more, the part which has crystallinity in an intermediate|middle layer increases, the elasticity modulus of an intermediate|middle layer when it is set at high temperature falls, and it becomes easy to make embedding property favorable. Moreover, if it is 70 mass % or less, it will become easy to ensure the softness|flexibility required as an intermediate|middle layer.

(Other monofunctional monomers)

Although the monofunctional monomer contained in the composition for intermediate|middle layer may contain only the above-mentioned crystalline monomer, it may contain monofunctional monomers other than a crystalline monomer.

Monofunctional monomers other than the crystalline monomer contain a group having an ethylenic double bond, such as a (meth)acryloyl group and a vinyl group, specifically (meth)acrylate having an alicyclic structure, a functional group containing (meth) acrylates, alkyl (meth) acrylates having less than 14 carbon atoms in the alkyl group, amide group-containing compounds, (meth) acrylates having an aromatic structure, (meth) acrylates having a heterocyclic structure, and other vinyl compounds. However, among these, it is preferable to use at least any one of (meth)acrylate which has an alicyclic structure, and functional group containing (meth)acrylate.

Examples of the (meth)acrylate having an alicyclic structure include isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyloxy (meth)acrylate. , cyclohexyl (meth)acrylate, adamantane (meth)acrylate, etc. are mentioned, Among these, isobornyl (meth)acrylate is preferable.

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

Examples of the alkyl (meth) acrylate having less than 14 carbon atoms in the alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate ) 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.

As the amide group-containing compound, (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylolpropane (meth) (meth)acrylamide compounds, such as acrylamide, N-methoxymethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide, are mentioned.

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. Examples of other vinyl compounds include styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylformamide, N-vinylpyrrolidone, and N-vinylcaprolactam.

<Photoinitiator>

It is preferable that the composition for intermediate|middle layer contains a photoinitiator so that actinic light, such as an ultraviolet-ray, may be irradiated and it may harden|cure easily.

Examples of the photoinitiator include photoinitiators such as a benzoin compound, an acetophenone compound, an acylphosphine oxide compound, a titanocene compound, a thioxanthone compound, and a peroxide compound. More specifically, examples For example, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, 2 and 4,6-trimethylbenzoyl-diphenyl-phosphine oxide. In addition, depending on the type of polyfunctional compound or monofunctional monomer, in addition to the above, aromatic diazonium salts, aromatic halonium salts, onium salts of aromatic sulfonium salts, nitrobenzyl esters, sulfonic acid derivatives, phosphoric acid esters, sulfonic acid derivatives, etc. It is also possible to use an anionic photopolymerization initiator such as a polymerization initiator, a catalyst system of alkoxytitanium and p-chlorophenyl-o-nitrobenzyl ether. A photoinitiator can be used individually or in combination of 2 or more types.

To [ content of a photoinitiator / a total of 100 mass parts of the said polyfunctional compound and a monofunctional monomer / ], Preferably 0.05-15 mass parts, More preferably, 0.1-10 mass parts, More preferably, 0.3-5 mass is wealth Moreover, the composition for intermediate|middle layers may contain photosensitizers, such as an amine and a quinone.

The composition for intermediate|middle layer may contain other additives in the range which does not impair the effect of this invention. Examples of other additives include antioxidants, antistatic agents, softeners (plasticizers), fillers, rust inhibitors, pigments, and dyes.

Moreover, it is preferable that the composition for intermediate|middle layer does not contain a heat-meltable resin substantially. By containing a crystalline monomer component, the composition for intermediate|middle layer of this invention can make embedding property favorable, preventing seepage of an intermediate|middle layer at the time of adhesion, even if it does not contain a heat-meltable resin substantially. In addition, the thermomeltable resin is a thing in which a clear and sharp melting peak is observed in DSC measurement, specifically, the difference between the melting initiation temperature and the melting peak temperature (melting point (Tm)) is 8 ° C. or less, for example, It has a melting point (Tm) of 45 to 90°C. Examples of the thermally meltable resin include an acrylic polymer that becomes waxy at room temperature, a polymer of α-olefin having 14 to 30 carbon atoms, and the like.

In addition, substantially not containing a heat-meltable resin means that the composition for intermediate|middle layer may contain a heat-meltable resin to such an extent that the film-formability of an intermediate|middle layer is not affected, For example, with respect to the whole amount of the composition for intermediate|middle layer, Although it means that you may contain about less than 2 mass %, it is preferable that the content is less than 1 mass %, and it is more preferable not to contain. By not containing a heat-meltable resin substantially, it becomes possible to suppress generation|occurrence|production of aggregation and a viscosity raise by the polymeric material of a solid state in the composition for intermediate|middle layer.

The composition for an intermediate layer usually contains the above polyfunctional compound and a monofunctional monomer as main components, and the total amount thereof is usually 70% by mass or more, preferably 80% by mass or more, and more preferably, based on the total amount of the composition for an intermediate layer. It will be 90 mass % or more. In addition, these total amounts should just be 100 mass % or less with respect to the whole amount of the composition for intermediate|middle layer, but in order to mix|blend additives, such as a photoinitiator, Preferably it is 99.9 mass % or less, More preferably, it becomes 99.7 mass % or less. . In addition, when a composition is diluted with the solvent etc. which volatilize in the manufacturing process, the composition whole quantity for intermediate|middle layer is the quantity except the volatile component, such as the dilution solvent.

Although the thickness of an intermediate|middle layer is suitably adjusted according to the height of bumps etc. used as a protection object, Preferably it is 150-700 micrometers, More preferably, it is 200-300 micrometers. When the thickness of the intermediate layer is 150 µm or more, even an adherend such as a wafer having a relatively high bump due to a high bump can be properly protected. Moreover, the distortion which arises when the said thickness is 700 micrometers or less when an adhesive sheet bends can be reduced.

[write]

Although the base material in particular used for an adhesive sheet is not restrict|limited, It is preferable that it is a resin film. Since there is little dust generation|occurrence|production compared with paper or a nonwoven fabric, a resin film is suitable for the processing member of an electronic component, and since an acquisition is easy, it is preferable. A single layer film containing one resin film may be sufficient as a base material, and the multilayer film which several resin film laminated|stacked may be sufficient as it.

Examples of the resin film used as the substrate include a polyolefin-based film, a vinyl halide polymer-based film, an acrylic resin-based film, a rubber-based film, a cellulose-based film, a polyester-based film, a polycarbonate-based film, a polystyrene-based film, and a polyphenyl A lensulfide-type film, a cycloolefin polymer-type film, etc. are mentioned.

Among these, a polyester film is preferable from a viewpoint of being able to hold a wafer stably when grinding a wafer to ultra-thin, and a viewpoint of being a film with high thickness precision, and, among a polyester film, A polyethylene terephthalate film is preferable from a viewpoint that an acquisition is easy and thickness precision is high.

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

Moreover, you may use the base material which laminated|stacked the easily bonding layer etc. on the surface of the resin film from a viewpoint of improving the adhesiveness of a base material and an intermediate|middle layer. Moreover, you may make a base material contain a filler, a coloring agent, an antistatic agent, antioxidant, an organic lubricant, a catalyst, etc. in the range which does not impair the effect of this invention.

The substrate may be transparent or opaque. However, when the pressure-sensitive adhesive or the composition for an intermediate layer constituting the pressure-sensitive adhesive layer is an energy ray-curable type, it is preferable that the substrate transmits an energy ray.

[Adhesive layer]

Examples of the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer include an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, a polyvinyl ether-based pressure-sensitive adhesive, and a urethane pressure-sensitive adhesive. In addition, as the pressure-sensitive adhesive, energy ray-curable pressure-sensitive adhesives, energy-beam foaming pressure-sensitive adhesives, heat-foaming pressure-sensitive adhesives, and water-swelling pressure-sensitive adhesives may be presented. of the adhesive is more preferable.

By using an energy-beam-curable adhesive, before energy-beam irradiation, an adhesive sheet adheres reliably to a semiconductor wafer, and it is possible to reliably protect to-be-adhered bodies, such as a semiconductor wafer. On the other hand, since it is possible to reduce the adhesive force of an adhesive layer by irradiating an energy ray when peeling an adhesive sheet, without damaging to-be-adhered bodies, such as a semiconductor wafer, and leaving an adhesive on a to-be-adhered body, the adhesive sheet can be peeled from the adherend.

The energy ray-curable adhesive may be an additive-type energy ray-curable adhesive comprising a base polymer such as an acrylic copolymer and an energy ray-curable resin, but has a radically reactive carbon-carbon double bond in the polymer side chain or main chain or at the end of the main chain The so-called built-in type energy ray-curable pressure-sensitive adhesive using a polymer as a base polymer such as an acrylic copolymer may be used.

Moreover, an adhesive contains a crosslinking agent, a photoinitiator, etc. other than base polymers, such as an acrylic copolymer, as needed.

The thickness of the pressure-sensitive adhesive layer is adjusted according to the difference in height of the surface of the adherend such as a semiconductor wafer or 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. .

[Releasable material]

As the release material constituting the pressure-sensitive adhesive sheet or the release material used in the process of the manufacturing method described later, a release sheet subjected to single-sided release treatment, a release sheet subjected to double-sided release treatment, etc. are used, and the release agent is applied on a base material for release material and the like.

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

Examples of the release agent include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins and butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, and fluorine-based resins.

Moreover, although the thickness of a peeling material is not specifically limited, Preferably it is 5-200 micrometers, More preferably, it is 10-120 micrometers.

[Method for Producing Adhesive Sheet]

There is no restriction|limiting in particular in the manufacturing method of the adhesive sheet of this invention, The adhesive sheet can be manufactured by a well-known method.

For example, an intermediate|middle layer can apply|coat the composition for intermediate|middle layer directly to one surface of a base material, and form a coating film, Then, it can harden and form it. In addition, an intermediate|middle layer may apply|coat the composition for intermediate|middle layer directly to the peeling process surface of a release material, perform a hardening process, and may bond and form a base material on the coating film. Under the present circumstances, what is necessary is just to peel suitably a peeling material, for example, after hardening process is complete|finished. Moreover, it is preferable to irradiate energy rays, such as an ultraviolet-ray, to the formed coating film, and to harden|polymerize hardening of an intermediate|middle layer. At this time, the irradiation amount of the energy ray is appropriately changed depending on the type of the energy ray, the thickness of the coating film, and the like. For example, when using an ultraviolet-ray, the illuminance of the ultraviolet-ray to irradiate becomes like this. Preferably it is 50-500 mW/cm<2>. In addition, the light quantity of an ultraviolet-ray becomes like this. Preferably it is 100-2500 mJ/cm<2>.

In addition, the pressure-sensitive adhesive layer can be formed by, for example, directly applying the pressure-sensitive adhesive composition on the intermediate layer formed as described above and drying it. Further, the pressure-sensitive adhesive composition is applied to the release-treated surface of the release material, dried to form a pressure-sensitive adhesive layer on the release material, and then the pressure-sensitive adhesive layer and the intermediate layer on the release material are bonded to each other, and on the substrate, the intermediate layer, the pressure-sensitive adhesive layer , an adhesive sheet provided with a release material may be formed. After this, you may peel the peeling material in an adhesive sheet as needed.

When forming an intermediate|middle layer or an adhesive layer, an organic solvent is further mix|blended with the composition for intermediate|middle layers, or an adhesive composition, and it is good also as a diluent of the composition for intermediate|middle layers or an adhesive composition.

Examples of the organic solvent to be used include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol.

In addition, as for these organic solvents, the organic solvent used at the time of the synthesis|combination of each component contained in the composition for intermediate|middle layer or an adhesive composition may be used as it is, and may add 1 or more types of organic solvents other than that.

The composition for intermediate|middle layer or adhesive composition can be apply|coated by a well-known coating method. Examples of the coating method include a spin coating method, a spray coating method, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, and a gravure coating method.

Moreover, when the composition for intermediate|middle layer or the adhesive composition is what mix|blended the organic solvent, after apply|coating this, it is preferable to heat and dry-process.

[How to use the adhesive sheet]

Although the adhesive sheet of this invention can be used for various uses, It is preferable to stick to a semiconductor wafer and to use it as a tape for semiconductor wafer protection. Moreover, it is more preferable to use an adhesive sheet as a back grind tape which adheres to the semiconductor wafer surface and protects the circuit formed in the wafer surface at the time of the subsequent wafer back surface grinding.

Since the adhesive sheet of this invention has favorable embedding property even if there is a height difference by bump etc. on a wafer surface, the protective performance of a wafer surface becomes favorable. Moreover, although an adhesive sheet is heated when affixing an adhesive sheet to a wafer, even if it heats and adheres, seepage of an intermediate|middle layer does not generate|occur|produce.

In addition, although the height of the bump formed in the wafer surface is not specifically limited, By selecting suitably the thickness of the intermediate|middle layer and adhesive layer of the adhesive sheet of this invention, it is possible to make the bump embedding property of various heights favorable.

Moreover, the temperature of the adhesive sheet at the time of affixing an adhesive sheet on a semiconductor wafer is about 40-80 degreeC, for example, Preferably it is 50-60 degreeC.

In addition, the adhesive sheet is not limited to a back grind sheet, It is also possible to use for another use. For example, the pressure-sensitive adhesive sheet may be used as a dicing sheet that is adhered to the back surface of the wafer and protects 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 by these Examples.

The measuring method and evaluation method in this invention are as follows.

[Weight Average Molecular Weight (Mw)]

It measured under the following conditions using the gel permeation chromatography apparatus (Product name "HLC-8020", Tosoh Corporation make), and the value measured by standard polystyrene conversion was used.

(Measuring conditions)

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

Column temperature: 40°C Developing solvent: tetrahydrofuran Flow rate: 1.0 mL/min

[Evaluation of burial property]

After peeling the release material from the adhesive sheets prepared in Examples and Comparative Examples on a wafer with bumps of 80 µm in height, 200 µm in pitch, and 100 µm in diameter (8 inch wafers made by Waltz), Lintec Co., Ltd. It was attached using a laminator RAD-3510F/12. In addition, at the time of attaching, the lamination table of the apparatus was 60 degreeC, and the lamination roll was 60 degreeC. After lamination, using a digital optical microscope (product name "VHX-1000", manufactured by KEYENCE Corporation), the circular pore diameter generated from the base material side around the bumps was measured. It shows that the embedding property with respect to the bump by an adhesive sheet is so high that the diameter of a space|gap is small. The embedding property of a bump was evaluated from the following criteria. The results are shown in Table 1.

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

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

C: The bubble is connected to the adjacent bump.

[Evaluation of seepage]

A 25 mm x 50 mm pressure-sensitive adhesive sheet was laminated on a silicon mirror wafer. The lamination conditions were the same as those in the embedding evaluation. After lamination, it was observed visually, and the case where there was no seepage of resin of an intermediate|middle layer was made into A, and the case where seepage was confirmed was made into C.

[Example 1]

(Formation of intermediate layer)

40 parts by mass (solid content) of a bifunctional urethane acrylate oligomer (product name "CN9018", manufactured by Arkema Co., Ltd., weight average molecular weight 45000) as a polyfunctional compound, and 60 parts by mass of stearyl acrylate (STA) as a crystalline monomer ( 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (product name "Darocure TPO", manufactured by BASF) as a photopolymerization initiator and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (product name "Darocure TPO", manufactured by BASF) are blended in 2.0 parts by mass (solid content), for UV-curable intermediate layer A composition was obtained. The composition for the intermediate layer was placed on a polyethylene terephthalate (PET) film-based release film (product name "SP-PET381031", manufactured by Lintec Co., Ltd., thickness 38 µm) in a fountain die method so that the thickness after curing was 200 µm. It was applied to form a coating film.

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

(Formation of adhesive sheet)

To the copolymer (Mw: 1.3 million) which copolymerized 94 mass % of 2-ethylhexyl acrylate and 6 mass % of 2-hydroxyethyl acrylate, 2-isocyanatoethyl methacrylate with respect to all the hydroxyl groups 100 parts by mass (solid content) of the acrylic copolymer obtained by reacting 50 mol%, 0.19 parts by mass (solid content) of a TDI-based isocyanate crosslinking agent (product name "BHS-8515", manufactured by Toyochem Corporation), and a photopolymerization initiator ( Product name "IRGACURE 184", manufactured by BASF) 0.748 parts by mass (solid content) was mixed in a solvent to prepare an acrylic pressure-sensitive adhesive coating solution.

This was coated on a peeling film, it heat-dried, and the 10 micrometers-thick adhesive layer was obtained on the peeling film. An adhesive sheet was obtained by bonding this to the intermediate|middle layer obtained above.

[Example 2]

As the polyfunctional compound, a liquid butadiene polymer having a plurality of vinyl groups in the side chain (product name "Ricon 154", manufactured by Cray Valley, weight average molecular weight 5200) was used, except that it carried out similarly to Example 1, and obtained the adhesive sheet.

[Example 3]

As the polyfunctional compound, a bifunctional polyalkyl acrylate having a polymerizable functional group at both terminals (product name "RC100C", manufactured by Kaneka Co., Ltd., weight average molecular weight 20000) was used, except that it was carried out in the same manner as in Example 1 .

[Examples 4 to 6]

It implemented similarly to Example 1 except having changed the kind of polyfunctional compound and the mass part of a polyfunctional compound and a monofunctional monomer 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 an intermediate layer, and a polyfunctional compound and a monofunctional monomer Except for changing the compounding amount as shown in Table 1, it was carried out in the same manner as in Example 1.

[Comparative Example 1]

As shown in Table 1, it was carried out in the same manner as in Example 1, 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]

It was carried out in the same manner as in Example 1, except that stearyl acrylate was not blended in the composition for the intermediate layer, 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]

In addition to stearyl acrylate as a monofunctional monomer, isobornyl acrylate (IBXA) was blended in the composition for the intermediate layer, and the blending amount of the polyfunctional compound and the monofunctional monomer was changed as shown in Table 1 It was carried out in the same manner as in Example 1.

※In addition, in Table 1, the mass part of each compound is shown by solid content.

In addition, a blank indicates that it is unmixed.

※Each compound in a table|surface is as follows.

(1) polyfunctional compounds

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

PB: liquid butadiene polymer (product name "Ricon 154", manufactured by Cray 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 an intermediate layer contains at least a polyfunctional compound and a crystalline monomer, the content of the polyfunctional compound is greater than 25% by mass relative to the monofunctional monomer, and 40% by mass or more of the monofunctional monomer By being a crystalline monomer, while being able to fill in the bump formed in the wafer surface suitably with the adhesive sheet, the seepage at the time of affixing an adhesive sheet to a wafer did not generate|occur|produce.

On the other hand, in Comparative Example 1, although the composition for an intermediate layer contained a crystalline monomer, since a monofunctional acrylate resin was used instead of a polyfunctional compound, the embedding property to the bump was sufficient, but the seepage of the intermediate layer could not be prevented. . Moreover, like Comparative Examples 2 to 4, when the monofunctional monomer was not mix|blended and there was little content of a polyfunctional compound, the embedding property with respect to a bump was inadequate.

10A, 10B: adhesive sheet
11: Write
12: middle layer
13: adhesive layer
14: release material

Claims (9)

It is an adhesive sheet provided with a base material, an intermediate layer, and an adhesive layer in this order,
The intermediate layer is a polyfunctional compound having at least two polymerizable functional groups, and a monofunctional monomer containing at least a crystalline monomer having a straight-chain carbon number of 14 to 22 carbon atoms is cured of a composition for an intermediate layer,
In the composition for an intermediate layer, the polyfunctional compound is contained in an amount greater than 25% by mass based on the monofunctional monomer,
The pressure-sensitive adhesive sheet in which the composition for an intermediate layer does not contain a heat-melting resin or contains less than 2% by mass. The pressure-sensitive adhesive sheet according to claim 1, wherein 40% by mass or more of the monofunctional monomer is the crystalline monomer. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the polyfunctional compound is a polyfunctional oligomer having a weight average molecular weight of 3000 to 60000. The adhesive sheet according to claim 1 or 2, 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 polyfunctional compound is at least one selected from the group consisting of urethane (meth)acrylate oligomers, acrylic polymers, and butadiene polymers. The pressure-sensitive adhesive sheet according to claim 1 or 2, 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. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the composition for an intermediate layer is an energy ray-curable type. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the intermediate layer has a thickness of 150 to 700 µm. The adhesive sheet according to claim 1 or 2, which is a tape for protecting semiconductor wafers.

Images