TW202223039A - Liquid adhesive, laminate, and method of producing semiconductor chip - Google Patents

Abstract

A liquid adhesive of an embodiment includes 60 mass% or greater of at least one ester compound represented by Formula (1) is described:

wherein total molar concentration of a polar functional group in the liquid adhesive is from 1 × 10-6 to 1.5 × 10-5 mol/g, and a storage modulus at 150℃ to 220℃ of a cured product of the liquid adhesive is from 15 to 35 MPa. Such a liquid adhesive may have sufficient adhesive force (holding force) even in a high temperature environment, low outgas properties in a high temperature environment, and can form a cured product that can be peeled easily after heat treatment.

Description

Liquid adhesive, laminate, and method of producing semiconductor wafers

The present disclosure relates to a liquid adhesive, a laminate, and a method of producing a semiconductor wafer.

In the semiconductor industry, in order to meet the demand for thinner packages and higher densities in die lamination technology, the thickness of semiconductor wafers has been reduced by so-called backside grinding, in which grinding and patterning surface opposite to the surface. The related art of supporting the wafer by a separate protective tape during backside grinding is not sufficient for the newly proposed various manufacturing steps. Therefore, what is proposed is a technique in which a semiconductor wafer is supported via an adhesive on a rigid transparent support (such as including light-to-heat-conversion, during backside grinding and, if necessary, subsequent steps) LTHC) layer on the glass substrate), and finally destroy the light-to-heat conversion layer by laser scanning to separate the semiconductor wafer or the semiconductor wafer obtained by stress-free singulation of the semiconductor wafer from the support.

Patent Document 1 (JP 2004-064040 A) describes a "laminate comprising a substrate to be ground; a bonding layer that is in contact with the substrate to be ground; a light-to-heat conversion layer that is The conversion layer includes a light absorber and a thermally decomposable resin; and an optically transparent support, wherein the light-to-heat conversion layer is formed by grinding the substrate to be ground. The surface opposite the bonding layer is formed, and then the light-to-heat conversion layer is decomposed by irradiation with radiant energy, and the ground substrate is separated from the optically transparent support".

Patent Document 2 (JP 2005-159155 A) describes a "method of producing a semiconductor wafer, the method comprising the steps of: applying a light-to-heat conversion layer containing a light absorbing agent and a thermally decomposable resin on an optically transparent support, and using When radiant energy irradiates the light-to-heat conversion layer, the light-to-heat conversion layer converts the radiant energy into heat, which is then decomposed by the heat; by preparing a semiconductor including a circuit surface with a circuit pattern and a non-circuit surface opposite to the circuit surface The wafer forms a laminate including a non-circuit surface in the outer side, the semiconductor wafer and the optically transparent support are bonded via a photocurable adhesive so that the circuit surface and the light-to-heat conversion layer face each other, and light is passed from the optically transparent support component side irradiation to cure the photocurable adhesive layer; grinding the non-circuit surface of the semiconductor wafer until the semiconductor wafer has the desired thickness; singulating the ground semiconductor wafer from the non-circuit surface side to Cut into a plurality of semiconductor wafers; irradiate with radiant energy from the optically transparent support side and decompose and separate the light-to-heat conversion layer into semiconductor wafers with an adhesive layer and the optically transparent support".

As an adhesive that can be used in the techniques described in Patent Documents 1 and 2, for example, Patent Document 3 (JP 2015-224316 A) describes a "temporary fastening adhesive composition containing Regarding (A) 100 parts by mass of (meth)acrylates in total, the (meth)acrylates contain monofunctional (meth)acrylates and polyfunctional (meth)acrylates; (B) 0.01 parts by mass to 5 parts by mass of a photopolymerization initiator, wherein the mass reduction rate is 10% by mass when the temperature is raised at a rate of 10°C/min under a nitrogen stream at a temperature greater than or equal to 250°C; and (C) 0.01 parts by mass to 1 Parts by mass of carbon black having a specific surface area of 30 m ² /g to 100 m ² /g".

The techniques described in Patent Documents 1 and 2 can address issues such as substrate thickness non-uniformity during backside grinding, warpage of thinned wafers after backside grinding, and problems caused by stress applied during backside grinding. caused by wafer damage.

Due to the rapid development in the field of power semiconductor and advanced packaging technology, the adhesive used to temporarily bond the wafer to the support is intended to continue to be used in the steps after the backside grinding and is therefore expected to have compatibility with those steps , such as thermal stability. Examples of steps following backside polishing include chemical mechanical polishing (CMP), physical vapor deposition (PVD) such as resin molding, wet etching, dry etching, vapor deposition, and sputtering electroplating), chemical vapor deposition (CVD), electroplating, electroless plating, and patterning by photolithography, and oxide film formation in the surface of silicon wafers.

In PVD such as vapor deposition and sputtering, films are typically formed at about 150°C, and resin molding using thermosetting resins typically involves heat treatment at about 220°C for several hours. During these high temperature steps, the cured adhesive is required to hold the wafer on the support. The internal stress created in the wafer by backside grinding causes the wafer to warp toward the ground surface side. Adhesives, on the other hand, also build up stress internally through a curing step by, for example, UV irradiation. Therefore, the cured adhesive must be thermally stable, It is also necessary to have sufficient adhesion (holding force) to overcome internal stresses, such as those separating the wafer from the cured adhesive, even during high temperature steps.

In addition, in vacuum processes such as vapor deposition, sputtering, or dry etching, when outgassing is generated by volatilizing or decomposing the cured adhesive at high temperature and reduced pressure, there are devices due to reduced vacuum Risk of internal fouling and deterioration of membrane quality. Therefore, it is desirable for the cured adhesive to have low outgassing properties in high temperature environments, eg, the mass loss of the cured adhesive is small.

Desirably, the cured adhesive is eventually removed from the wafer without residue. Adhesion control additives, such as polysiloxanes, can be added to the liquid adhesive to facilitate release of the cured adhesive. However, such polysiloxanes are not compatible with other components in the liquid adhesive, such as (meth)acrylic compounds, and thus aggregates of polysiloxane may remain on the wafer, or between different batches. The adhesion between them may vary widely. Furthermore, from the viewpoint of avoiding or reducing siloxane contamination on the wafer surface, it is desirable to avoid the use of polysiloxanes.

The inventors have discovered that several requirements for an adhesive used to temporarily bond two substrates, such as a wafer and a support, can be achieved by selecting raw materials with specific chemical structures, introducing appropriate amounts of polar functional groups, and adjusting curing The storage modulus in the rubbery flat area of the adhesive is achieved.

The present disclosure provides a liquid adhesive that has sufficient adhesion (holding force) even in a high temperature environment, has low outgassing properties in a high temperature environment, and can form a cure that can be easily peeled off after heat treatment product.

An embodiment provides a liquid adhesive comprising 60% by mass or more of at least one ester compound represented by formula (1):

in

R is independently a divalent group including a substituted or unsubstituted alicyclic group,

Q is independently a divalent group selected from the group consisting of a substituted or unsubstituted divalent aliphatic group, a substituted or unsubstituted divalent aromatic group, a substituted or unsubstituted divalent aromatic group substituted divalent heteroaryl, and combinations of two or more thereof,

E is independently a free radical polymerizable group selected from the group consisting of acryloxy and methacryloyloxy, and

n is an integer from 1 to 10,

in

The total molar concentration of polar functional groups in the liquid adhesive is 1×10 ^-6 mol/g to 1.5×10 ^-5 mol/g,

The polar functional groups are -OH, -COOH, groups represented by formula (2):

[Chemical formula 2]

-Si(OR ² ) _3-n (OH) _n , wherein R ² is an organic group and n is an integer from 1 to 3; -P(O)(OR ² ) _2-n (OH) _n , wherein R ² is an organic group and n is an integer of 1 to 2; -OP(O)(OR ² ) _2-n (OH) _n , wherein R ² is an organic group and n is an integer of 1 to 2; -SH, ring oxy, or -NH ₂ , and

The storage modulus of the cured product of the liquid adhesive at 150° C. to 220° C. is 15 MPa to 35 Mpa.

Another embodiment provides a laminate comprising a substrate, a bonding layer in contact with the substrate, and a cured product of the liquid adhesive; a light-to-heat conversion layer, the light-to-heat conversion layer comprising a light absorber and thermally decomposable resins, and optically transparent supports.

Yet another embodiment provides a method of producing a semiconductor wafer, the method comprising:

applying a light-to-heat conversion layer on the optically transparent support, the light-to-heat conversion layer comprising a light absorbing agent and a thermally decomposable resin;

providing a semiconductor wafer including a circuit surface having a circuit pattern and a non-circuit surface opposite the circuit surface;

Applying a layer of liquid adhesive including a photopolymerization initiator to the circuit surface of the semiconductor wafer and the optically transparent support so that the layer of the liquid adhesive and the circuit surface of the semiconductor wafer and the optically transparent support contact;

curing the liquid adhesive by ultraviolet radiation through the optically transparent support to form a tie layer and form a laminate including the non-circuit surface in an outer surface;

grinding the non-circuit surface of the semiconductor wafer until the semiconductor wafer has a desired thickness;

The ground semiconductor wafer is diced from the non-circuit surface side, and the ground semiconductor wafer is diced into a plurality of semiconductor wafers;

irradiating through the optically transparent support with radiant energy to decompose and separate the light-to-heat conversion layer into the plurality of semiconductor wafers including the bonding layer and the optically transparent support; and

The bonding layer is removed from the semiconductor wafers as needed.

The present disclosure can provide a liquid adhesive that has sufficient adhesive force (holding force) even in a high temperature environment, has low outgassing properties in a high temperature environment, and can form a cure that can be easily peeled off after heat treatment product.

It should be noted that the above description is not to be construed as intended to disclose all embodiments of the invention and all advantages associated with the invention.

1: Laminate

2: Substrate

3: Bonding layer

4: Light-to-heat conversion layer

5: Optically transparent support

[ Fig. 1 ] is a schematic cross-sectional view of a laminate of an example.

Hereinafter, for illustrative purposes, representative embodiments of the present invention will be described in more detail with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

The liquid adhesive of one embodiment contains 60% by mass or more of at least one ester compound represented by the formula (1):

In formula (1),

R is independently a divalent group including a substituted or unsubstituted alicyclic group,

Q is independently a divalent group selected from the group consisting of a substituted or unsubstituted divalent aliphatic group, a substituted or unsubstituted divalent aromatic group, a substituted or unsubstituted divalent aromatic group substituted divalent heteroaryl, and combinations of two or more thereof,

E is independently a free radical polymerizable group selected from the group consisting of acryloxy and methacryloyloxy, and

n is an integer from 1 to 10.

The ester compound represented by the formula (1) is excellent in thermal stability and miscibility with other components. Therefore, since the liquid adhesive includes 60% by mass or more of the ester compound represented by the formula (1), it is possible to impart stability (resistance to thermal decomposition) in a high temperature environment to the cured product of the liquid adhesive, That is, low outgassing characteristics. In addition, since the ester compound of the formula (1) includes an alicyclic group, it is also possible to impart chemical resistance to the cured product of the liquid adhesive suitable for steps using chemical solutions, such as CMP, wet etching, electrolytic plating, electroless plating , and pattern formation by lithographic etching.

R is independently a divalent group including a substituted or unsubstituted alicyclic group. In one embodiment, R is a divalent group having 5 to about 20 carbon atoms and including substituted or unsubstituted cycloalkanediyl. In another embodiment, R is a divalent group having 5 to about 12 carbon atoms and including substituted or unsubstituted cycloalkanediyl. In some embodiments, R is substituted or unsubstituted cyclopentanediyl, substituted or unsubstituted cyclohexanediyl, substituted or unsubstituted norbornanediyl, substituted or unsubstituted Unsubstituted norbornediyl, substituted or unsubstituted tetracyclododecanediyl, or substituted or unsubstituted tetrahydrodicyclopentadiendiyl, or groups including Alkanediyl having 1 to 10 carbon atoms (eg, methylene, ethylidene, propylidene, butanediyl, hexanediyl, heptanediyl, octanediyl, and decanediyl group) combined divalent groups. Examples of the divalent group in which one methylene group is bonded to each of the two terminals of the tetrahydrodicyclopentadiene diyl group include divalent groups having the following structures. In this formula, "*" represents a bonding position having an adjacent group.

Q is independently a divalent group selected from the group consisting of a substituted or unsubstituted divalent aliphatic group, a substituted or unsubstituted divalent aromatic group, a substituted or unsubstituted divalent aromatic group Substituted divalent heteroaryl, and combinations of two or more thereof. In one embodiment, Q is independently a substituted or unsubstituted divalent aliphatic group having 1 to 30 carbon atoms, a substituted or unsubstituted divalent group having 6 to about 14 carbon atoms An aromatic group, a substituted or unsubstituted heteroaromatic group having 3 to about 14 carbon atoms, or a combination thereof.

In another embodiment, Q is a substituted or unsubstituted divalent aliphatic group including a substituted or unsubstituted alicyclic group. In yet another embodiment, Q is substituted or unsubstituted cyclopentanediyl, substituted or unsubstituted cyclohexanediyl, substituted or unsubstituted norbornanediyl, Norbornediyl, substituted or unsubstituted, tetracyclododecanediyl, substituted or unsubstituted, or tetrahydrodicyclopentadienediyl, substituted or unsubstituted, or inclusive groups and alkanediyl groups having 1 to 10 carbon atoms (e.g., methylene, ethylidene, propylidene, butanediyl, hexanediyl, heptanediyl, octanediyl, and decanediyl) alkanediyl) combination of divalent aliphatic groups.

In another embodiment, Q is substituted or unsubstituted phenylene or substituted or unsubstituted naphthylene.

Examples of substituents for R and Q include straight-chain or branched-chain alkyl groups having 1 to 100 carbon atoms, straight-chain or branched-chain alkenyl groups having 2 to 100 carbon atoms, straight-chain or branched chain alkenyl groups having 2 to 100 carbon atoms Chain or branched alkynyl, hydroxyl, pendant oxy, alkoxy with 1 to 100 carbon atoms, mercapto, cycloalkyl with 5 to 20 carbon atoms, aromatic group with 6 to 14 carbon atoms groups, heteroaromatic groups having 3 to 14 carbon atoms, aryloxy groups having 6 to 14 carbon atoms, halogen atoms, straight or branched chain haloalkyl groups having 1 to 100 carbon atoms, cyano groups , nitro, nitrone, amine, amide, -C(O)H, -C(O)-, -S-, -S(O) ₂ -, -OC(O)-O-, -NR ¹ -C(O)-, -NR ¹ -C(O)-NR ¹ -, -OC(O)-NR ¹ - (R ¹ is H or an alkyl group having from 1 to 8 carbon atoms) , acyl group, oxo group, carboxyl group, carbamate group, sulfonyl group, sulfonamide group, and thiol group.

E is independently a free radical polymerizable group selected from the group consisting of acryloxy and methacryloyloxy. In one embodiment, in the ester compound of formula (1), one E is acryloxy, and the other E is methacryloyloxy.

n is an integer from 1 to about 10. In one embodiment, n is an integer from 1 to 7. In another embodiment, n is an integer from 1 to 5. In yet another embodiment, n is an integer from 1 to 3. In yet another embodiment, n is 1 or 2.

In one embodiment, the ester compound of formula (1) does not include ether linkages. The ester compound of the formula (1) having an ether bond has low thermal stability and tends to increase outgassing in a high temperature environment due to the decomposition product of the cured product. The ester compound of formula (1) which does not include an ether bond can advantageously impart low outgassing properties to the cured product of the liquid adhesive.

The number average molecular weight of the ester compound of formula (1) may be about 500 or more, or about 1000 or more. The number average molecular weight of the ester compound of formula (1) may be about 8,000 or less, or about 4,000 or less. Number average molecular weights were obtained by gel permeation chromatography (GPC) measurements calibrated with polystyrene standards.

Some exemplary ester compounds of formula (1) are indicated below.

The liquid adhesive may include the ester compound of formula (1) in an amount of about 62 mass % or more, about 65 mass % or more, or about 70 mass % or more. The liquid adhesive may include the ester compound of formula (1) in an amount of about 95% by mass or less, about 90% by mass or less, or about 85% by mass or less.

In terms of total molar concentration, the liquid adhesive includes x 10 ^-6 mol/g to 1.5 x 10 ^-5 mol/g of polar functional groups. In this disclosure, "polar functional groups" are -OH, -COOH, groups represented by formula (2):

-Si(OR ² ) _3-n (OH) _n (wherein R ² is an organic group, and n is an integer from 1 to 3), -P(O)(OR ² ) _2-n (OH) _n (wherein R ² is an organic group and n is an integer from 1 to 2), -OP(O)(OR ² ) _2-n (OH) _n (wherein R ² is an organic group and n is an integer from 1 to 2), - SH, epoxy, or _-NH2 . Examples of organic groups for R include straight ^- chain or branched-chain alkyl groups having 1 to 30 carbon atoms, straight-chain or branched-chain alkenyl groups having 2 to 30 carbon atoms, straight-chain or branched-chain alkenyl groups having 2 to 30 carbon atoms Chain or branched alkynyl groups, cycloalkyl groups having 5 to 20 carbon atoms, aromatic groups having 6 to 14 carbon atoms, heteroaromatic groups having 3 to 14 carbon atoms, and 1 to 14 carbon atoms Straight or branched chain haloalkyl of 30 carbon atoms. Since the adhesive force (holding force) of the cured product of the liquid adhesive can be precisely controlled, the polar functional group is preferably OH, -COOH, a group represented by the formula (2), and -Si(OR ² ) _{3- n} (OH) _n , and since -OH is readily available in industry, -OH is more preferred.

As described below, in combination with setting the storage modulus of the cured product of the liquid adhesive in a specific temperature range to a specific range, the total molar concentration of polar functional groups in the liquid adhesive was set to 1×10 ⁻⁶ mol /g to 1.5×10 ⁻⁵ mol/g, and thus it is possible to obtain a cured product having adhesive force (holding force) in a high temperature environment and releasability after heat treatment in a compatible manner at a high level.

The total molar concentration of polar functional groups in the liquid adhesive may be greater than or equal to 1.2×10 ⁻⁶ mol/g, or greater than or equal to 1.5×10 ⁻⁶ mol. The total molar concentration of the specific polar functional groups in the liquid adhesive may be less than or equal to 1.2×10 ⁻⁵ mol/g, or less than or equal to 1×10 ⁻⁵ mol/g.

Regarding the total molar concentration of polar functional groups in the liquid adhesive, the amount of carboxylic acid was determined by the neutral titration method specified in JIS K 0070:1992, and the hydroxyl group The amount is determined by potentiometric titration. In addition, with respect to the total molar concentration of polar functional groups in the cured adhesive, the amount of carboxylic acid and the amount of hydroxyl groups were determined by a reactive pyrolysis GC/MS method using tetramethylammonium hydroxide Methyl carboxylic acid and methyl ether derivatives are designated respectively. Regarding the measurement conditions, the terminal carboxylic acid and the terminal were methylated by adding about 5 microliters of tetramethylammonium hydroxide solution as a reaction reagent to several mg of the sample and performing rapid heating derivatization by a thermal decomposition device at 500°C The simultaneous detection of thermal decomposition products of hydroxyl groups, and thus the amount of carboxylic acid and the amount of hydroxyl groups, are determined. As a reaction reagent, a tetraethylammonium hydroxide solution or a tetrabutylammonium hydroxide solution is also effectively used.

Polar functional groups can be derived from ester compounds represented by formula (1), or other components of the liquid adhesive (such as oligomers or polymers), or monofunctional or polyfunctional ( Meth)acrylic acid compound.

In one embodiment, the liquid adhesive also includes a polyfunctional (meth)acrylic compound having polar functional groups. Without being bound by any theory, the polyfunctional (meth)acrylic compound having polar functional groups effectively improves the adhesion (holding force) of the cured product in a high temperature environment. In addition, since the polyfunctional (meth)acrylic compound having a polar functional group has a plurality of polymerizable functional groups, the polyfunctional (meth)acrylic compound having a polar functional group is not as effective as other polymerizable groups during the curing time of the liquid adhesive. Split reaction, and easy to fasten with the cured product. Therefore, outgassing of the cured product in a high temperature environment can be reduced. Examples of the polyfunctional (meth)acrylic compound having a polar functional group include trimethylolpropane di(meth)acrylate, neotaerythritol di(meth)acrylate, neotaerythritol tri(meth)acrylate Acrylates, EO-modified tri(meth)acrylates, ditrimethylolpropane di(meth)acrylates, ditrimethylolpropane triacrylates (Meth)acrylate, Dipiveaerythritol tetra(meth)acrylate, and Dipiveaerythritol penta(meth)acrylate. As the number of polymerizable functional groups increases, even a small amount of addition can easily affect the storage modulus of the adhesive after curing, and thus difunctional (meth)acrylic compounds and trifunctional (meth)acrylic compounds are better. Since neotaerythritol tri(meth)acrylate is easily available in industry, the polyfunctional (meth)acrylic compound having polar functional groups is preferably neotaerythritol tri(meth)acrylate.

The liquid adhesive may contain a polyfunctional (meth)acrylic compound having a polar functional group in an amount of about 0.01 mass % or more, about 0.02 mass % or more large, or about 0.04 mass % or more. The liquid adhesive may include a polyfunctional (meth)acrylic compound having a polar functional group in an amount of about 0.5 mass % or less, about 0.45 mass % or more less, or about 0.4 mass % or less.

The liquid adhesive may include oligomers or polymers other than the ester compound of formula (1). Such oligomers or polymers can be advantageously used to adjust mechanical properties of the cured product, such as storage modulus in high temperature regions. Such oligomers or polymers are preferably formed only by bonds that are stable even in high temperature environments. Examples of such oligomers and polymers include acrylic polymer esters of 1,6-hexanediol.

The liquid adhesive may contain oligomers or polymers other than the ester compound of formula (1) in a total amount of about 5% by mass or more, or about 8% by mass or more. The liquid adhesive may contain oligomers other than the ester compound of formula (1) or polymer, the total amount of the oligomer or polymer is about 20 mass % or less, or about 15 mass % or less.

烷-2-基]-2,2-二甲基乙基丙烯酸酯、及三環[5.2.1.0^2,6]癸二甲醇二(甲基)丙烯酸酯。在本揭露中，具有極性官能基之雙官能(甲基)丙烯酸單體被分類為具有極性官能基之多官能(甲基)丙烯酸化合物。 The liquid adhesive may contain bifunctional (meth)acrylic monomers. Difunctional (meth)acrylic monomers can be used, for example, to introduce a cross-linked structure into the cured product and to adjust the storage modulus in the rubbery flat regions of the cured product. Examples of difunctional (meth)acrylic monomers include 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol(di)methacrylate, bisphenol A di(meth)acrylate Acrylates, Ethoxylated Bisphenol A Diacrylate, Propoxylated Bisphenol A Diacrylate, 2-[5-ethyl-5-[(acryloyloxy)methyl]-1,3- two

Alk-2-yl]-2,2-dimethylethylacrylate, and tricyclo[ ^5.2.1.02,6 ]decanedimethanol di(meth)acrylate. In the present disclosure, bifunctional (meth)acrylic monomers having polar functional groups are classified as polyfunctional (meth)acrylic compounds having polar functional groups.

The liquid adhesive may comprise a difunctional (meth)acrylic monomer in an amount of about 5 mass % or more, about 10 mass % or more, or about 14 mass % or bigger. The liquid adhesive may comprise a difunctional (meth)acrylic monomer in an amount of about 40 mass % or less, about 35 mass % or less, or about 30 mass % or less.

The liquid adhesive may contain monofunctional (meth)acrylic monomers. Monofunctional (meth)acrylic monomers can adjust the viscosity of the liquid adhesive within an appropriate range according to the application. Examples of monofunctional (meth)acrylic monomers include alkyl (meth)acrylates such as butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, (meth)acrylate Heptyl acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate ester; Alicyclic (meth)acrylates such as cyclohexyl (meth)acrylate; aromatic (meth)acrylates such as phenyl (meth)acrylate and phenylethyl (meth)acrylate; and polar Monofunctional (meth)acrylates of functional groups, such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate Esters, 2-(meth)acryloyloxyethyl-2-hydroxyethylphthalic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(methyl) Acryloyloxyethylsuccinic acid, and (meth)acrylooxypropyltrimethoxysilane.

The liquid adhesive may comprise a monofunctional (meth)acrylic monomer in an amount of about 3 mass % or more, about 7 mass % or more, or about 10 mass % or bigger. The liquid adhesive may contain a monofunctional (meth)acrylic monomer in an amount of about 40 mass % or less, about 30 mass % or less, or about 20 mass % or less.

In one embodiment, the liquid adhesive includes a polymerization initiator. Examples of the polymerization initiator include photopolymerization initiators and thermal polymerization initiators.

Photopolymerization initiators are used in applications where liquid adhesives are cured by UV light irradiation. Examples of photopolymerization initiators include benzoin derivatives, benzyl ketals, α,α-dialkoxyacetoxybenzene, α-hydroxyalkylphenone, α-aminoalkyl Benzophenones, monoacylphosphine oxides, titanosen compounds, combinations of benzophenones and amines, and Michler's ketones.

The liquid adhesive may contain a photopolymerization initiator in an amount of about 0.1 mass % or more, about 0.2 mass % or more, or about 0.5 mass % or larger. The liquid adhesive may contain a photopolymerization initiator in an amount of about 5% by mass or less, about 3% by mass or less, or about 2% by mass or less.

Thermal polymerization initiators are used in applications where liquid adhesives are cured by heating. Examples of thermal polymerization initiators include peroxides such as dicumyl peroxide, dibenzoyl peroxide, 2-butanone peroxide, tertiary butyl perbenzoate, ditertiary butyl peroxide , 2,5-bis(tertiarybutylperoxy)-2,5-dimethylhexane, bis(tertiarybutylperoxyisopropyl)benzene, and tertiarybutylhydroperoxide; and Nitrogen compounds such as 2,2'-azobis(2-methyl-propionitrile), 2,2'-azobis(2-methylbutyronitrile), and 1,1'-azobis(cyclo hexanecarbonitrile).

Liquid adhesives may include solvents. Examples of solvents include ketones such as acetone, methyl ethyl ketone, cyclohexanone; esters such as ethyl acetate and butyl acetate; and alcohols such as ethanol and butanol.

In one embodiment, the liquid adhesive is solvent-free. Solvent-free liquid adhesives are suitable for applications where the liquid adhesive cures in enclosed spaces.

In one embodiment, the liquid adhesive is substantially free of low surface energy compounds selected from the group consisting of polysiloxanes and fluorine compounds. The liquid adhesive of the present disclosure can impart peelability to the cured product after heat treatment by combining a predetermined amount of the ester compound represented by the formula (1), the content of the polar functional group, and the viscoelastic property of the cured product without requiring Use such low surface energy compounds. Therefore, in this embodiment, it is possible to inhibit or prevent precipitation as aggregated species of low surface energy compounds in the cured product, which aggregated species are immiscible with the components in the liquid adhesive. In the present disclosure, "substantially not including" means that the content of the low surface energy compound in the liquid adhesive is small At about 5 mass %, less than about 2 mass %, less than about 1 mass %, or less than about 0.1 mass %. In another embodiment, the liquid adhesive does not include low surface energy compounds.

Liquid adhesives may also include thickeners, plasticizers, dispersants, fillers, flame retardants, or heat aging inhibitors as optional additives.

Liquid adhesives can be produced by mixing the above components. Oligomers or polymers that do not flow at room temperature can be heated and then mixed with the other components.

In one embodiment, the viscosity of the liquid adhesive at 25°C is about greater than or equal to 100mPa. s and about less than or equal to 10000mPa. s. In the case where the liquid adhesive is applied by spin coating, the viscosity of the liquid adhesive at 25° C. can be set to be about greater than or equal to 1000 mPa. s, or about greater than or equal to 2000mPa. s and about less than or equal to 8000mPa. s, or about less than or equal to 5000mPa. s to uniformly apply the liquid adhesive to the wafer with the desired thickness. The viscosity is a value obtained by using a cone-plate viscometer (HAAKE (trade name) under the conditions of a temperature of 25° C., a cone diameter of 35 mm, a cone angle of 1 degree, and a rotation speed of 1 degree/min. Leometer, Thermo Fisher Scientific K.K. (Minato-ku, Tokyo, Japan), set the liquid adhesive between the cone and the plate and wait 60 seconds, then read the value within 30 seconds after the start of the measurement.

In one embodiment, the turbidity of the liquid adhesive is about less than or equal to 1500 NTU. The turbidity of the liquid adhesive can be used as an index indicating whether the insoluble components precipitate or aggregate when the liquid adhesive is cured. From this perspective, the haze of the liquid adhesive is preferably about 1000 NTU or less, and more preferably about 500 NTU or less. The turbidity of the liquid adhesive is determined by using the table top turbidity Meter 2100N (Hach), where the unit is set to NTU, the measurement range is automated, the signal averaging is on, and the ratio processing is on; and the marking line for adding liquid adhesive to the sample well; setting the sample well at on a benchtop turbidimeter; and read the value within 20 seconds of setting after the value has stabilized.

The liquid adhesive is disposed between two substrates, such as a semiconductor wafer and an optically transparent support, in contact with the substrates, and can be applied by heating or by irradiation with radiation (such as ultraviolet light) and electron beams cured. Thus, the two substrates can be joined via the cured product of the liquid adhesive. Applying, heating and irradiating the liquid adhesive with radiation can be performed by known methods.

The storage modulus of the cured product of the liquid adhesive at 150° C. to 220° C. is 15 MPa to 35 Mpa. The storage modulus of the cured product of the liquid adhesive at 150°C to 220°C is in the above range, indicating that at least in this temperature range, the viscoelastic properties of the cured product are in a rubber-like flat region, that is, the cured product has sufficient wettability to adhere to the adherend. In addition, in combination with setting the molar concentration of the polar functional group in the liquid adhesive to the above range, the storage modulus of the cured product of the liquid adhesive at 150°C to 220°C is set to the above range, so that it can be ensured when heat treatment is performed. The cured product is then peeled off with sufficient strength to prevent cracking of the cured product to ensure peelability after heat treatment while imparting flexibility to the cured product to exert adhesive force (holding force) in a high temperature environment. The storage modulus of the cured product of the liquid adhesive at 150°C to 220°C may be greater than or equal to 16 MPa, or greater than or equal to 17 MPa, and less than or equal to 26 MPa, or less than or equal to 24 MPa. The storage modulus of the cured product of the liquid adhesive was determined by using a dynamic viscoelasticity measuring device RSA3 (TA Instruments Japan Inc., Shinagawa-ku, Tokyo, Japan) was judged under the conditions of a modification of 0.03%, a frequency of 1 kHz, an initial temperature of 0°C, a final temperature of 250°C, and a heating rate of 5°C/min.

In one embodiment, when the cured product in the shape of a strip of 10mm×50mm×0.2mm is heated in air at 300°C for 30 minutes, the mass loss of the cured product of the liquid adhesive is about less than or equal to 9%, about less than or equal to 8%, or about less than or equal to 7%. Mass loss is defined by the following equation:

Mass loss (%) = (Initial mass of strip (g) - Mass of strip after heat treatment (g))/Initial mass of strip (g)

An embodiment provides a laminate comprising: a substrate; a bonding layer, the bonding layer being in contact with the substrate and comprising a cured product of a liquid adhesive; and a light-to-heat conversion layer comprising a light-absorbing layer agent and thermally decomposable resin; and an optically transparent support. The light-to-heat conversion layer is decomposed by irradiation with radiant energy, such as laser light, and enables separation from the optically transparent support without damaging the substrate.

Figure 1 shows a schematic cross-sectional view of the laminate of this embodiment. In FIG. 1 , the laminate 1 includes a substrate 2 , a bonding layer 3 , a light-to-heat conversion layer 4 , and an optically transparent support 5 in this order.

Examples of the substrate include substrates comprising Group III to Group V compound semiconductors such as silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbide (SiC), and gallium arsenide (GaAs); Or a substrate comprising a Group II to Group VI compound semiconductor such as zinc sulfide (ZnS). The substrate can be in the shape of a semiconductor wafer and can be bonded to Structures, such as circuit patterns, are formed in the surfaces where the layers contact. In one embodiment, the substrate is intended to be thinned by backside grinding in the state of the laminate.

The bonding layer is arranged in contact with the substrate, contains the cured product of the liquid adhesive, and is used to fasten the substrate and the optically transparent support together via the light-to-heat conversion layer. After the substrate and the optically transparent support are separated due to the decomposition of the light-to-heat conversion layer, the substrate to which the bonding layer is attached is obtained. Therefore, it is desirable that the bonding layer can be easily peeled off from the substrate. The tie layer has sufficient adhesion (holding force) to secure the substrate and optically clear support together, but desirably the tie layer has low adhesion to the extent that the tie layer can be peeled off after heat treatment. A bonding layer satisfying the above requirements can be obtained by using a bonding layer containing a cured product of a liquid adhesive.

The thickness of the tie layer is preferably set to such an extent that non-uniformities in the substrate surface are absorbed, and to ensure the thickness uniformity required for steps (such as backside grinding) and the tear strength required to peel the tie layer. degree. In one embodiment, the thickness of the bonding layer is about 10 μm or more, or about 25 μm or more, and about 150 μm or less, or about 100 μm or less.

The light-to-heat conversion layer contains a light absorber and a thermally decomposable resin. The radiant energy used to irradiate the light-to-heat conversion layer in the form of laser light or the like is absorbed by the light absorber and converted into heat energy. The generated thermal energy rapidly increases the temperature of the photothermal conversion layer, and when the temperature reaches the thermal decomposition temperature of the thermally decomposable resin in the photothermal conversion layer, the resin is thermally decomposed. The gas generated by thermal decomposition forms a void layer in the light-to-heat conversion layer, separates the light-to-heat conversion layer into two, and separates the substrate from the optically transparent support.

The light absorber absorbs radiant energy at the wavelengths used. As the radiant energy, laser light having a wavelength generally from 300 nm to 2000 nm, preferably from 300 nm to 1100 nm can be used, and specific examples of the radiant energy include a YAG laser that generates light having a wavelength of 1064 nm, a double harmonic wave having a wavelength of 532 nm Wave YAG lasers, and semiconductor lasers with wavelengths from 780nm to 1300nm. Examples of light absorbers include particulate metal powders, such as carbon black, graphite powder, iron, aluminum, copper, nickel, cobalt, manganese, chromium, zinc, and tellurium; metal oxide powders, such as black titanium oxide; and dyes or pigments , such as aromatic diamine metal complexes, aliphatic diamine metal complexes, aromatic dithiol metal complexes, mercaptophenol metal complexes, squarylium compounds, cyanine dyes, secondary Methyl dyes, naphthoquinone dyes, and allium quinone dyes. The light absorber may be in the form of a film comprising a vapor deposited metal film. The light absorber is preferably carbon black. Carbon black can significantly reduce the force required to separate the substrate and optically transparent support after irradiation with radiant energy. The combined use of carbon black with dyes that selectively absorb wavelengths of laser light and transmit other wavelength ranges can be used to form a light-to-heat conversion layer that selectively transmits alignment light during the singulation step.

The concentration of the light absorbing agent in the light-to-heat conversion layer varies depending on the type of the light absorbing agent, particle morphology and degree of dispersion, but in the case of general carbon black having a particle size of about 5 nm to 500 nm, the concentration may be about greater than or equal to 5 vol%, about 20 vol% or more, or about 35 vol% or more, and about 70 vol% or less, about 60 vol% or less, or about 55 vol% or less. The concentration of carbon black is set to be about 5% by volume or more, so that the decomposition of the thermally decomposable resin can be accelerated. The concentration of carbon black is set to be less than or equal to about 70% by volume, so The film-forming properties of the light-to-heat conversion layer and the adhesion properties to adjacent layers can be ensured. In the case where the liquid adhesive used to form the bonding layer is UV-curable and irradiated with ultraviolet light passing through the photothermal conversion layer, the concentration of carbon black is preferably less than or equal to 60% by volume so that the UV Light transmittance is sufficient for curing liquid adhesives.

Examples of thermally decomposable resins include cellulose esters such as gelatin, cellulose, cellulose acetate, and nitrocellulose, polyphenols, polyvinyl butyral, polyvinyl acetate, polycarbonate, polyurethane, Polyester, polyorthoester, polyacetal, polyvinyl alcohol, polyvinylpyrrolidone, copolymer of vinylidene chloride and acrylonitrile, poly(meth)acrylate, polyvinyl chloride, polysiloxane, and block copolymers comprising polyurethane units. In addition, the thermally decomposable resin may be used alone or in combination of two or more. The glass transition temperature (Tg) of the thermally decomposable resin is desirably greater than or equal to 20°C, and more desirably greater than or equal to 100°C, to prevent the light-to-heat conversion layer from thermally decomposing the thermally decomposable resin to form a void layer. Disengage from engagement again. In the case where the optically transparent support is glass, in order to enhance the adhesion between the glass and the light-to-heat conversion layer, a polar group (for example, -COOH) capable of hydrogen bonding with the silanol groups on the glass surface can be used or -OH) heat can decompose the resin. In applications using chemical solutions such as wet etching, thermally decomposable resins having functional groups in the molecule capable of self-crosslinking by heat treatment, or thermally decomposable resins capable of being crosslinked by ultraviolet light or visible light may also be used or its precursor to impart chemical resistance to the light-to-heat conversion layer.

The light-to-heat conversion layer may also include transparent fillers as required. The transparent filler acts to prevent the light-to-heat conversion layer from being separated from the bond again by thermally decomposing the thermally decomposable resin to form a void layer. Examples of transparent fillers include silica, talc, and barium sulfate. The transparent filler can enhance the releasability between the substrate and the optically transparent support after irradiation with radiant energy without hindering the curing of the UV-curable liquid adhesive.

The light-to-heat conversion layer may also contain other additives as required. Examples of other additives include low temperature gas generating agents such as photopolymerization initiators, coupling agents, crosslinking agents, foaming agents, and subliming agents.

The light-to-heat conversion layer may be formed by mixing a light absorber, a thermally decomposable resin, and a solvent as necessary to form a precursor coating liquid; applying the coating liquid on the optically transparent support; and drying. The light-to-heat conversion layer can also be formed by mixing a light absorber, a monomer or oligomer that is a raw material of a thermally decomposable resin, an additive as needed (such as a photopolymerization initiator), and a solvent as needed to form and applying the precursor coating liquid to the optically transparent support; drying; and polymerizing, or curing. Examples of coating methods include spin coating, die coating, and roll coating.

The thickness of the light-to-heat conversion layer is generally greater than or equal to about 0.1 μm and less than or equal to about 5 μm. When the thickness of the light-to-heat conversion layer is about 0.1 μm or more, it is not necessary to excessively increase the concentration of the light absorber, and thus the film-forming properties and the adhesion properties of the light-to-heat conversion layer can be maintained. When the thickness of the light-to-heat conversion layer is about 5 μm or less, it is possible to ensure the ultraviolet light transmittance required for forming the bonding layer by using a UV-curable liquid adhesive. From these viewpoints, the thickness of the light-to-heat conversion layer is preferably about 0.3 μm to about 3 μm, more preferably about 0.5 μm to about 2.0 μm.

The optically transparent support is made of a material capable of transmitting radiant energy such as laser light and, if necessary, radiation (eg, ultraviolet light) used to cure the liquid adhesive form. An optically clear support is a material that desirably maintains the substrate in a flat state and does not damage the substrate during steps such as backside grinding and shipping. The transmittance of the optically transparent support is desirably, eg, about greater than or equal to 50% of the target radiant energy or radiation.

Desirably, the optically transparent support is sufficiently rigid to prevent warping of the substrate (eg, semiconductor wafer) during backside grinding. The optically transparent support preferably has a Young's modulus of from 1 MPa to 10 MPa and a thickness of greater than or equal to 500 μm.

Suitable examples of optically transparent supports include glass plates and acrylic plates. To enhance adhesion to adjacent layers, such as the light-to-heat conversion layer, the optically transparent support may need to be surface-treated with a silane coupling agent or the like as needed.

Optically transparent supports may be exposed to high temperatures due to heat generated in the light-to-heat conversion layer upon irradiation with radiant energy, frictional heat at the time of backside grinding, and the like. Alternatively, additional steps such as CMP, PVD (such as resin molding, wet etching, dry etching, vapor deposition, and sputtering), CVD, electrolytic plating, PVD (such as resin molding, wet etching, dry etching, vapor deposition, and sputtering), CVD, electrolytic plating, Electroplating, patterning by photolithography, and high temperature processing to form oxide films in the surface of silicon wafers. An optically transparent support with heat resistance, chemical resistance, or a low expansion coefficient can be selected according to these steps. Examples of optically transparent supports with heat resistance, chemical resistance, and low coefficient of expansion include glass such as synthetic glass, borosilicate glass, and sapphire glass, especially Pyrex (trade name), Corning No. 1737 and No. 7059 (available Available from Corning Incorporated), and Tempax (available from Schott AG).

After the backside grinding step and before singulation, the surface of the semiconductor wafer may be chemically etched with a chemical solution as an intermediate step. This step is performed to remove grinding-damaged layers in the back surface of the semiconductor wafer and to increase the lateral strength of the wafer. Alternatively, as a final step in the semiconductor wafer thinning step, a thickness of tens of μm of the semiconductor wafer may be removed by chemical etching. In the case of a single crystal of silicon (Si) on a semiconductor wafer, a mixed acid containing hydrogen fluoride is generally used as an etching chemical solution. At this time, in the case where the optically transparent supporter is a glass substrate (excluding sapphire glass), the end portion of the optically transparent supporter is also etched by a chemical solution. Therefore, in the case of repeated use of the optically transparent support, the glass can be protected from being corroded by hydrogen fluoride by providing an acid-resistant (etching chemical solution-resistant) protective film on the glass substrate in advance. Acid-resistant resins can be used as protective films. Desirably, the acid-resistant resin can be fastened to the glass substrate by dissolving the acid-resistant resin in an organic solvent; applying it as a solution; and drying. Furthermore, it is desirable that the acid-resistant resin transmits sufficient light having the wavelength of the radiant laser to separate the glass substrate from the semiconductor wafer. From this point of view, suitable examples of the acid-resistant resin include amorphous polyolefins, cyclic olefin copolymers, and polyvinyl chloride, which do not include a condensation system bonded in a molecule.

In order to obtain thickness uniformity after grinding the substrate, it is desirable that the thickness of the optically transparent support be uniform. For example, in order to thin silicon wafers to less than or equal to 50 μm and to reduce the uniformity of polysilicon wafers to less than or equal to ±10%, it is desirable that the optically transparent support has a thickness variation of less than or equal to ±2 μm. In the case of repeated use of the optically transparent support, it is desirable that the optically transparent support has scratch resistance. In the case of repeated use of the optically transparent support, it is desirable to take into account the radiant energy The material of the optically transparent support is selected by wavelength to inhibit damage to the optically transparent support due to the radiant energy. For example, in the case of using Pyrex (trade name) glass as the optically transparent support and performing irradiation with a third harmonic YAG laser (355 nm), it is possible to separate the optically transparent support from the semiconductor wafer or semiconductor wafer, However, the optically transparent support may absorb radiant energy and receive thermal damage, and there are cases where the optically transparent support cannot be reused.

Where the substrate is a semiconductor wafer with a circuit pattern, the circuit may be damaged by radiant energy such as laser light passing through the optically transparent support, the light-to-heat conversion layer, and the bonding layer and reaching the semiconductor wafer. To avoid such damage, either a dye that absorbs light at wavelengths of radiant energy or a pigment that reflects the light may be incorporated into any of the layers forming the laminate, or a layer containing a Layers of such dyes or pigments. Examples of laser light absorbing dyes include dyes having absorption peaks close to the wavelength of the laser light used (eg, phthalocyanine dyes and cyanine dyes). Examples of pigments that reflect laser light include inorganic white pigments such as titanium oxide.

The laminate can be produced, for example, by the following method. First, the precursor coating liquid of the light-to-heat conversion layer is applied on the optically transparent support, dried, and irradiated with ultraviolet light to cure. Next, a liquid adhesive is applied to either or both of the surface of the cured light-to-heat conversion layer and the surface of the unpolished side of the substrate. The light-to-heat conversion layer and the substrate are bonded together via a liquid adhesive, and heated or irradiated with ultraviolet light through the optically transparent support to cure the liquid adhesive, and thereby form a bonding layer. Thus, a laminate having the structure depicted in FIG. 1 can be produced. It is desirable that the lamination system is formed under vacuum to prevent the inclusion of air between the layers.

One embodiment provides a method of producing a semiconductor wafer, the method comprising: applying a light-to-heat conversion layer on an optically transparent support, the light-to-heat conversion layer comprising a light absorber and a thermally decomposable resin; providing a semiconductor wafer, the semiconductor wafer Including a circuit surface with a circuit pattern and a non-circuit surface opposite to the circuit surface; applying a layer of liquid adhesive including a photopolymerization initiator to the circuit surface of the semiconductor wafer and the optically transparent support to make the liquid adhere the layer of adhesive is in contact with the circuit surface of the semiconductor wafer and the optically transparent support; the liquid adhesive is cured by ultraviolet radiation through the optically transparent support to form a bonding layer and a laminate is formed , the laminate includes the non-circuit surface in the outer surface; grind the non-circuit surface of the semiconductor wafer until the semiconductor wafer has the desired thickness; cut the ground semiconductor wafer from the non-circuit surface side single, and dicing the ground semiconductor wafer into a plurality of semiconductor wafers; irradiating with radiant energy through the optically transparent support to decompose and separate the light-to-heat conversion layer into the plurality of semiconductor wafers including the bonding layer and the optically transparent support; and removing the bonding layer from the semiconductor wafers as needed.

A method of producing a semiconductor wafer according to this embodiment includes a series of steps of performing backside grinding of the semiconductor wafer on an optically transparent support and subsequent singulation to divide the semiconductor wafer into semiconductor wafers. The semiconductor wafer is fastened on the optically transparent support via the bonding layer, and thus the semiconductor wafer can be subjected to grinding without damage and can be singulated without spalling. The light-to-heat conversion layer disposed between the semiconductor wafer and the optically transparent support is decomposed by irradiation with radiant energy, such as laser light, and can be separated from the optically transparent support without damaging the semiconductor wafer. In this way, according to With this embodiment, it is possible to produce high quality thinned semiconductor wafers with few or no spalling defects.

In the production method of this embodiment, as a step of forming a laminate that sequentially includes a semiconductor wafer, a bonding layer, a light-to-heat conversion layer, and an optically transparent support and includes a non-circuit surface of the semiconductor wafer in the outer surface, The steps of the method described above for producing laminates can be used. That is, first, the precursor coating liquid of the light-to-heat conversion layer is applied on the optically transparent support, dried, and irradiated with ultraviolet light to be cured. Next, a liquid adhesive containing a photopolymerization initiator is applied to either or both of the surface of the cured light-to-heat conversion layer and the circuit surface (surface on the unpolished side) of the semiconductor wafer. The light-to-heat conversion layer and the semiconductor wafer are bonded to each other via a liquid adhesive, and the liquid adhesive is cured by using ultraviolet light irradiation through the optically transparent support to form a bonding layer. Thus, a laminate can be formed. Desirably, the formation of the laminate is performed under vacuum to prevent the inclusion of air between the layers.

The grinding of the non-circuit surfaces of semiconductor wafers can be performed by using a grinding apparatus comprising a base capable of clamping and securing the object to be ground, a mandrel, and a grinding wheel rotatably attached. connected to the lower end portion of the mandrel. The optically transparent support side of the laminate was mounted on the base of the grinding device, and the laminate was clamped and fastened with the base. Subsequently, the semiconductor wafer is ground by rotating the grinding wheel into contact with the laminate while a water stream is supplied to the laminate. Grinding may be performed until the thickness of the semiconductor wafer is about 150 μm or less, preferably about 50 μm or less, and more preferably about 25 μm or less.

After grinding the semiconductor wafer to the desired thickness, steps such as chemical mechanical polishing (CMP), physical vapor deposition (PVD) (such as resin molding, wet etching, dry etching, vapor deposition) may be performed as desired , and sputtering), chemical vapor deposition (CVD), electroplating, electroless plating, patterning by photolithography, forming oxide films in the surface of silicon wafers. Subsequently, the polished semiconductor wafer is singulated from the non-circuit surface side and cut into a plurality of semiconductor wafers. Since the circuit surface of the semiconductor wafer of the ground laminate is in the bonding layer side, the dicing lines (lines to be diced) in the circuit surface cannot be directly observed from the outside. Therefore, it is desirable for the singulation device to have a function that enables observation of the circuit surface on the inside (eg, an image recognition device including a charge-coupled device (CCD) and a light source emitting infrared, visible, or ultraviolet light) combination). After the die bond tape is attached to the ground semiconductor wafer, singulation may be performed to form a semiconductor wafer with the die bond tape.

After singulation, irradiation with radiant energy through the optically transparent support is performed to decompose and separate the light-to-heat conversion layer into a semiconductor wafer with a bonding layer and an optically transparent support. For example, an adhesive tape is provided on the semiconductor wafer side of a laminate including a plurality of semiconductor wafers. The adhesive tape is usually fastened in a flat with a ring-shaped metal frame. Next, irradiation with, for example, laser light as radiant energy is performed from the optically transparent support side of the laminate. After being irradiated with laser light, the optically transparent support is pulled up to separate the optically transparent support from the semiconductor wafer. The adhesive tape has sufficient adhesive strength to secure the individual semiconductor chips when the bonding layer is removed, but allows easy peeling of the adhesive tape after the bonding layer is removed.

Irradiation with laser light may be performed in a state in which the laminate is sandwiched and fastened with the fastening base so that the optically transparent support is tied to the upper surface. A laser light source is selected that has an output sufficient to decompose the thermally decomposable resin of the photothermal conversion layer at the wavelength of light absorbed by the photothermal conversion layer to generate decomposed gas and separate the optically transparent support from the semiconductor wafer. Examples of laser light include YAG laser (wavelength 1064 nm), double harmonic YAG laser (wavelength 532 nm), and semiconductor laser (wavelength from 780 nm to 1300 nm). The depth of focus of the laser light is desirably as deep as about greater than or equal to 30 μm to stably separate the semiconductor wafer from the optically transparent support. The laser output can be 0.3W to 100W, the scanning speed can be 0.1m/sec to 40m/sec, and the beam diameter can be 5μm to 300μm. The processing speed can be increased by increasing the laser output and increasing the scanning speed. In the case of limited laser output, the processing speed can be increased by increasing the beam diameter and reducing the number of scans. Laser light scanning is performed desirably from the end portion of the laminate without any gaps. For example, the laser light scanning may be performed linearly reciprocally in the tangential direction of the semiconductor wafer (single plural semiconductor wafers) from the end portion, or may be performed spirally from the end portion toward the center.

After irradiation with laser light, the optically transparent support is separated from the semiconductor wafer by using a vacuum pickup or the like.

After separating the optically transparent support from the semiconductor wafer, the bonding layer is removed from the semiconductor wafer if necessary. In order to remove the bonding layer, an adhesive tape for removing the bonding layer can be used, which can form an adhesive force with the bonding layer which is higher than the adhesion force between the semiconductor chip and the bonding layer. An adhesive tape for removing the bonding layer can be bonded on the bonding layer to peel the bonding layer from the semiconductor wafer. in this way formula, a plurality of semiconductor wafers attached to the adhesive tape can be obtained. Subsequently, the individual semiconductor wafers can be picked up one by one with the self-adhesive tape and used at the next steps such as wire bonding and packaging.

The liquid adhesives of the present disclosure can be used in a variety of applications, including temporary fastening applications. Liquid adhesives are suitable for securing wafers with supports (specifically, laminated chip size packages (CSPs) mounted at high density), threading requiring high functionality and high speed. Transmissive CSPs, ultra-thin compound semiconductors (eg, GaAs) requiring improved heat dissipation efficiency, electrical properties, and stability, semiconductor wafers including large wafers (eg, 16-inch silicon wafers), and ultra-thin crystal wafer applications middle.

Example

In the following examples, specific examples of the present disclosure will be illustrated, but the present invention is not limited to these examples. All parts and percentages are based on mass unless otherwise indicated. The values basically include errors derived from the measuring principle and the measuring device. Numerical values are usually expressed in normal rounded significands.

Table 1 indicates the reagents, materials, and the like used in this example.

The structural formula of PEAM-1769 is shown below. In this structural formula, n is 1 to 5.

Examples 1 to 6 and Comparative Examples 2 to 11

The monomers (polyfunctional (meth)acrylic compound and bifunctional monomer) and the photopolymerization initiator were placed in a light-shielding plastic bottle, and stirred until the photopolymerization initiator was completely dissolved. Next, oligomers or polymers (ester compounds of formula (1) and other (meth)acrylate oligomers/polymers) are added to the bottle and stirred. In oligomers or polymers, oligomers or polymers that do not flow at room temperature are preheated to 60°C and then mixed to obtain a liquid adhesive. Table 2 indicates the composition of the liquid adhesives of Examples 1 to 6 and Comparative Examples 2 to 11.

Comparative Example 1

LC-5320F00 (3M Japan Ltd., (Shinagawa-ku, Tokyo, Japan)) was used as the liquid adhesive of Comparative Example 1.

Viscoelastic properties

Samples for measuring viscoelastic properties were produced by the following procedure. Films with a thickness of 50 μm to 100 μm were formed by spin coating or knife coating (Comparative Example 8 only). The film was cured by irradiating the film with ultraviolet light for 30 seconds through a glass substrate coated with a light-to-heat conversion layer having a transmittance of 10%. The amounts of irradiation with UVA and UVV were 3000 mJ/cm ² and 4000 mJ/cm ² , respectively.

The storage modulus of the cured film was determined by using a dynamic viscoelasticity measuring device RSA3 (TA Instruments Japan Inc., (Shinagawa-ku, Tokyo, Japan)) at a modification of 0.03%, a frequency of 1 kHz, an initial temperature of 0° C., 250 Measured under the conditions of a final temperature of °C, and a heating rate of 5 °C/min, and obtained storage elastic moduli at 150 °C, 200 °C, and 220 °C.

viscosity

The viscosity of the liquid adhesive was measured by using a cone-plate viscometer (HAAKE (commercial product) under the conditions of a temperature of 25°C, a cone diameter of 35mm, a cone angle of 1 degree, and a rotation speed of 1 degree/min. Name) Leometer, Thermo Fisher Scientific K.K. (Minato-ku, Tokyo)), set the liquid adhesive between the cone and the plate and wait 60 seconds, then read the value within 30 seconds after the start of the measurement.

Peel (delamination) test

Samples for peel (delamination) testing were produced by the following procedure. About 0.4 g of liquid adhesive was dispensed into the center of a float glass plate (80 mm x 50 mm x 1 mm). Next, carefully place another float glass plate on top of the liquid adhesive, taking care not to trap air bubbles between the non-float glass plates. Subsequently, the liquid adhesive began to spread in circles. The obtained laminate was placed under UV-LED. When the diameter of the liquid adhesive reached 50 mm, the laminate was irradiated with ultraviolet light for 20 seconds. The amounts of irradiation with UVA, UVB, UVC, and UVV were 22351 mJ/cm ² , 841 mJ/cm ² , 87 mJ/cm ² , and 2198 mJ/cm ² , respectively. The liquid adhesive formed an approximately 200 μm thick bonding layer comprising the cured product sandwiched between two float glass sheets.

Heat the hot plate to 200°C. The laminates were placed on a hot plate and observed in detail during the test. The laminate was kept on the hot plate for 5 minutes. A sample in which peeling was not observed between the bonding layer and the float glass plate was evaluated as OK, and a sample in which peeling occurred was evaluated as NG.

Measurement of peel strength

Samples for measuring peel strength were produced by the following procedure. A PET film (initial peel strength) or aluminum foil (peel strength after heat treatment) was placed on a vacuum chuck as a liner. Two strands of nylon yarn (74 μm in diameter) were placed side by side on the pad spaced 45 mm apart to serve as spacers. About 0.4 g of liquid adhesive was dropped onto the liner between the two spacers. Next, carefully place the float glass plate on the liquid adhesive, taking care not to trap air bubbles between the float glass plate and the liner. After the liquid adhesive was sufficiently wet and spread, the laminate was moved to a UV chamber and irradiated with UV light for 30 seconds. The irradiation dose was 3000 mJ/cm ² . The liquid adhesive forms a bonding layer containing the cured product sandwiched between the liner and the float glass sheet.

(A) Initial peel strength

The bonding layer was cut into a width of 10 mm on a float glass plate by using a razor blade in a state where the bonding layer was covered with a liner (PET film). Next, the 180-degree peel strength between the float glass plate and the bonding layer was measured using a digital dynamometer (ZTS-20N, Imada Co., Ltd., (Toyohashi-shi, Aichi, Japan)).

(B) Peel strength after heat treatment

The laminate was placed in an oven preheated to 200°C for 30 minutes. Next, the laminate is taken out and placed in a room temperature atmosphere for 5 minutes to 10 minutes. The bonding layer was cut to a width of 10 mm on a float glass plate by using a razor blade in a state where the bonding layer was covered with a liner (aluminum foil). Next, remove the aluminum foil. Subsequently, the 180-degree peel strength between the float glass plate and the bonding layer was measured using a digital dynamometer (ZTS-20N, Imada Co., Ltd., (Toyohashi-shi, Aichi, Japan)).

Mass loss (assessment of thermal stability)

The cured product of the liquid adhesive was cut into strips of 10 mm x 50 mm x 0.2 mm. Measure the quality of the bars. Next, the strip was placed in a muffle furnace preheated to 300°C and held for 30 minutes. The strip was removed from the muffle furnace and cooled in a room temperature atmosphere. Subsequently, the mass of the strip is measured. The mass loss of the cured product of the liquid adhesive was calculated by the following equation.

Mass loss (%) = (Initial mass of strip (g) - Mass of strip after heat treatment (g))/Initial mass of strip (g)

Table 2 indicates the properties and evaluation results of the liquid adhesive. Note that the liquid adhesives of all Examples and Comparative Examples do not contain polysiloxanes. Since peeling was observed in a part of the bonding layer, the peeling test result of Comparative Example 4 is described as "(NG)". In Table 2, "N/A" means that the evaluation could not be performed.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention.

1: Laminate

2: Substrate

3: Bonding layer

4: Light-to-heat conversion layer

5: Optically transparent support

Claims (12)

A liquid adhesive comprising 60% by mass or more of at least one ester compound represented by formula (1):

in R is independently a divalent group including a substituted or unsubstituted alicyclic group, Q is independently a divalent group selected from the group consisting of a substituted or unsubstituted divalent aliphatic group, a substituted or unsubstituted divalent aromatic group, a substituted or unsubstituted divalent aromatic group substituted divalent heteroaryl, and combinations of two or more thereof, E is independently a free radical polymerizable group selected from the group consisting of acryloxy and methacryloyloxy, and n is an integer from 1 to 10, in The total molar concentration of polar functional groups in the liquid adhesive is 1×10 ^-6 mol/g to 1.5×10 ^-5 mol/g, The polar functional groups are -OH, -COOH, groups represented by formula (2): [Chemical formula 2]

-Si(OR ² ) _3-n (OH) _n , wherein R ² is an organic group and n is an integer from 1 to 3; -P(O)(OR ² ) _2-n (OH) _n , wherein R ² is an organic group and n is an integer of 1 to 2; -OP(O)(OR ² ) _2-n (OH) _n , wherein R ² is an organic group and n is an integer of 1 to 2; -SH, ring oxy, or -NH ₂ , and The storage modulus of the cured product of the liquid adhesive at 150° C. to 220° C. is 15 MPa to 35 MPa. Such as the liquid adhesive of claim 1, wherein the viscosity of the liquid adhesive at 25 ℃ is 100mPa. s to 10000mPa. s. The liquid adhesive of claim 1, wherein the liquid adhesive comprises a polymerization initiator. The liquid adhesive of claim 3, wherein the polymerization initiator is a photopolymerization initiator. The liquid adhesive of claim 1, wherein the liquid adhesive does not substantially include low surface energy compounds selected from the group consisting of polysiloxanes and fluorine compounds. The liquid adhesive of claim 1, wherein the turbidity of the liquid adhesive is less than or equal to at 1500NTU. The liquid adhesive of claim 1, wherein the ester compound does not include an ether bond. The liquid adhesive of claim 1, wherein Q is a substituted or unsubstituted divalent aliphatic group, and the substituted or unsubstituted divalent aliphatic group includes a substituted or unsubstituted alicyclic group base. The liquid adhesive of claim 1, further comprising a polyfunctional (meth)acrylic compound having a polar functional group. A laminate comprising: substrate; A bonding layer, which is in contact with the substrate and includes a cured product of the liquid adhesive as claimed in claim 1; a light-to-heat conversion layer comprising a light absorber and a thermally decomposable resin; and Optically transparent support. The laminate of claim 10, wherein the substrate comprises silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbide (SiC), Group III to Group V compound semiconductors, or Group II to Group VI compound semiconductors. A method of producing a semiconductor wafer, the method comprising: A light-to-heat conversion layer is applied on the optically transparent support, the light-to-heat conversion layer comprising Light absorbers and thermally decomposable resins; providing a semiconductor wafer comprising a circuit surface having a circuit pattern and a non-circuit surface opposite the circuit surface; Applying a layer of the liquid adhesive of any one of claims 4 to 9 to the circuit surface of the semiconductor wafer and the optically transparent support so that the layer of the liquid adhesive and the circuit surface of the semiconductor wafer and The optically transparent support contacts, curing the liquid adhesive by UV irradiation through the optically transparent support to form a tie layer and form a laminate including the non-circuit surface in an outer surface; grinding the non-circuit surface of the semiconductor wafer until the semiconductor wafer has a desired thickness; The ground semiconductor wafer is diced from the non-circuit surface side, and the ground semiconductor wafer is diced into a plurality of semiconductor wafers; irradiating through the optically transparent support with radiant energy to decompose and separate the light-to-heat conversion layer into the plurality of semiconductor wafers including the bonding layer and the optically transparent support; and The bonding layer is removed from the semiconductor wafers as needed.

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