JP2823883B2 - Adhesive sheet for attaching wafer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet, and more particularly, to a pressure-sensitive adhesive sheet for attaching a wafer to be used for cutting and separating a semiconductor wafer into small pieces.

TECHNICAL BACKGROUND AND PROBLEMS OF THE INVENTION Semiconductor wafers such as silicon and gallium arsenide are manufactured in a large diameter state, and this wafer is cut and separated (diced) into element pieces and then transferred to the next step, a mounting step. ing. At this time, dicing, washing, drying, expanding, pickup, and mounting steps are added to the semiconductor wafer in a state in which the semiconductor wafer is attached to the adhesive sheet in advance.

As the pressure-sensitive adhesive sheet used in the dicing process of such a semiconductor wafer, a pressure-sensitive adhesive layer such as an acrylic-based pressure-sensitive adhesive layer provided on a base material surface made of a polyvinyl chloride film has been used. However, the pressure-sensitive adhesive sheet having such an acrylic pressure-sensitive adhesive layer has a problem that when picking up each chip of the diced semiconductor wafer, the pressure-sensitive adhesive remains on the chip surface and the chip is contaminated. .

In order to solve such a problem, there has been conventionally proposed a method of reducing the amount of the pressure-sensitive adhesive by partially applying the pressure-sensitive adhesive to the surface of the base material instead of applying the pressure-sensitive adhesive entirely. According to this method, although the amount of the adhesive with respect to the total number of chips can be reduced and the contamination of the chip surface with the adhesive can be reduced to some extent, the adhesive force between the wafer chip and the adhesive sheet is reduced, so that the dicing step is performed. A new problem arises in that the wafer chips are detached from the adhesive sheet during each of the washing, drying, and expanding steps performed subsequently.

Such an adhesive sheet used in a process from a dicing process to a pickup process of a semiconductor wafer has a sufficient adhesive force to a wafer chip from a dicing process to an expanding process, and has a sufficient adhesive force to a wafer chip at the time of pickup. It is desired to have an adhesive strength such that an adhesive does not adhere.

Such an adhesive sheet is disclosed in JP-A-60-196,956.
JP-A-60-223,139 and JP-A-60-223,139, on the substrate surface,
There has been proposed a pressure-sensitive adhesive sheet coated with a pressure-sensitive adhesive comprising a low molecular weight compound having at least two or more photopolymerizable carbon-carbon double bonds in a molecule, which can be three-dimensionally reticulated by light irradiation. And in this publication, the photopolymerizable carbon
Examples of low molecular weight compounds having at least two carbon double bonds include trimethylolpropane triacrylate, tetramethylol methanetetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, and dipentaerythritol hexaacrylate. Acrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, commercially available oligoester acrylate and the like are exemplified.

A pressure-sensitive adhesive layer composed of a low-molecular-weight compound having at least two or more photopolymerizable carbon-carbon double bonds in a molecule is applied on a substrate composed of a polyvinyl chloride (PVC) film as exemplified above. The inventors have found that the pressure-sensitive adhesive sheet has the following problems.

That is, when the pressure-sensitive adhesive sheet to be attached to a wafer is used after being stored for a long period of time, the plasticizer is often transferred from the polyvinyl chloride base into the pressure-sensitive adhesive, and the pressure-sensitive adhesive is often softened. Therefore, when such an adhesive sheet is used, there is a problem that the chip cannot be reliably picked up even if an attempt is made to pick up the chip from the adhesive sheet after a dicing step, a UV irradiation step, and the like.

Also, by the softening of the adhesive as described above,
Apparently, the pressure-sensitive adhesive sheet is in a softened state, and the pressure-sensitive adhesive sheet is displaced from the holding position of the flat frame and loosened, and the pressure-sensitive adhesive sheet is gradually detached from the flat frame, so that the next step of die bonding cannot be performed.

On the other hand, a wafer pressure-sensitive adhesive sheet using a base sheet containing no plasticizer is also known, and as such a base sheet, an ethylene / methacrylic acid copolymer sheet is used. The wafer bonding sheet using the ethylene / methacrylic acid copolymer sheet as the base sheet is different from the wafer bonding adhesive sheet using the polyvinyl chloride sheet as the base sheet, and does not include a plasticizer in the base material. For,
The plasticizer does not migrate to the adhesive and the pressure-sensitive adhesive layer is not softened. However, the wafer sticking sheet using the ethylene-methacrylic acid copolymer sheet as a base sheet is inferior in stress relaxation property as compared with a wafer sticking adhesive sheet using a polyvinyl chloride sheet as a base sheet (in other words, If the base material is expanded, the force of the base material to return to the original state, that is, the restoring force is large), and the elongation is small, so that when the sheet is expanded on the flat frame, Since the sheet end is shifted from the holding portion of the ring of the frame due to the restoring force, the chip interval on the sheet is reduced. Further, if the deviation of the sheet edge is large, the sheet is separated from the flat frame similarly to the case of the polyvinyl chloride sheet, so that there is a problem that the die bonding in the next step cannot be performed.

The present inventors have intensively studied to solve such problems associated with the conventional technology, and when the specific polymer film is used as the base sheet of the pressure-sensitive adhesive sheet, the above problems can be solved at once. The present invention has been completed.

Object of the invention The present invention is to solve the problems associated with the prior art as described above, without the pressure-sensitive adhesive is softened, it is possible to maintain stable adhesive properties for a long time, Moreover, it is an object of the present invention to provide a pressure-sensitive adhesive sheet for attaching a wafer, which is excellent in stress relaxation property, has a large elongation, and does not loosen.

More specifically, an object of the present invention is to provide a pressure-sensitive adhesive sheet for wafer adhesion as described above, which is less likely to be detached from a flat frame during expanding. .

SUMMARY OF THE INVENTION The pressure-sensitive adhesive sheet for wafer bonding according to the present invention is a pressure-sensitive adhesive sheet for wafer bonding obtained by applying a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive and a radiation-polymerizable compound on a substrate surface, wherein the base material comprises: A] Polymerization of (i) a vinyl chloride monomer or (ii) a monomer mixture of a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer in an aqueous medium containing a polyol soluble in the vinyl chloride monomer. The film is characterized by being a film comprising a polymer composition obtained by reacting the polyol-containing vinyl chloride polymer obtained with [B] isocyanate.

In the pressure-sensitive adhesive sheet for attaching a wafer according to the present invention, since a film made of the polymer composition as described above is used as the base material, the pressure-sensitive adhesive does not soften and maintains stable pressure-sensitive adhesive properties for a long time. And has excellent stress relaxation, large elongation, and no loosening. Therefore, the pressure-sensitive adhesive sheet for attaching a wafer according to the present invention is less likely to be detached from the flat frame during expanding.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the pressure-sensitive adhesive sheet for attaching a wafer according to the present invention will be specifically described.

The pressure-sensitive adhesive sheet 1 according to the present invention comprises a substrate 2 and a pressure-sensitive adhesive layer 3 coated on the surface thereof, as shown in FIG. In order to protect the adhesive 3, it is preferable to temporarily adhere the releasable sheet 4 to the upper surface of the adhesive 3 as shown in FIG.

The shape of the pressure-sensitive adhesive sheet according to the present invention can take any shape such as a tape shape and a label shape.

In the present invention, [A] (i) a vinyl chloride monomer or (ii) a monomer mixture of a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer, A sheet formed from a polymer composition obtained by reacting a polyol-containing vinyl chloride polymer obtained by polymerization in an aqueous medium containing the same and [B] an isocyanate compound is used.

Examples of monomers copolymerizable with vinyl chloride used for preparing the polymer composition as described above include vinylidene chloride and vinylidene monomers such as vinylidene fluoride;
Acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, cyanoethyl acrylate, methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, styrene, methyl styrene, vinyl Examples include styrene derivatives such as toluene and chlorostyrene, vinyl monomers such as acrylonitrile, ethylvinylbenzene, and vinylnaphthalene, and dialkenes monomers such as butadiene, isoprene, and chloroprene.

When a mixture of vinyl chloride and a monomer as described above is used, vinyl chloride can be used in any amount.

When preparing a polyol-containing vinyl chloride polymer, a short-chain or long-chain polyol is used.As the short-chain polyol, aliphatic, alicyclic, aromatic-substituted aliphatic or heterocyclic are used. Dihydroxy compounds, trihydroxy compounds, tetrahydroxy compounds, and specifically, 1,2-ethanediol, 1,2-propanediol,
1,4-butanediol, 1,3-butenediol, 1,6-hexanediol, 1,10-decamethylenediol, 2,5-
Dimethyl-2,5-hexanediol, neopentyl glycol, diethylene glycol, 1,4-cyclohexanedimethanol, bis (β = hydroxyethoxy) benzene, p-xylene diol, dihydroxyethyltetrahydrophthalate, trimethylolpropane, glycerin, -Methylpropane-1,2,3-triol, 1,2,6
-Hexanetriol, pentaerythritol and the like are used.

As long-chain polyols, polyester polyols, polyether polyols, polycarbonate polyols, vinyl polyols, diene polyols, castor oil polyols, silicone polyols, polyolefin polyols, and copolymers thereof are used. Such long-chain polyols have a molecular weight of 30.
It is desirably from 0 to 10,000, preferably from 500 to 8000.

Polyester polyols include, for example, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleic anhydride, fumaric acid, itaconic acid Polyester polyols obtained by reacting a dicarboxylic acid selected from the above with a hydroxy compound selected from the short-chain polyols described above are used.

Polyester polyols are β-propiolactone, bivalolactone, δ-valerolactone, ε-caprolactone, methyl-ε-caprolactone, dimethyl-ε.
It can also be obtained by reacting a lactone compound such as -caprolactone or trimethyl-ε-caprolactone with a hydroxy compound selected from the above-mentioned short-chain polyols and the like.

As the polyether polyol, specifically, polytetramethylene glycol, polyethylene glycol,
Polypropylene glycol, polyoxypropylene glycol and the like are used.

As the polycarbonate polyol, specifically,
Use is made of a hydroxy compound selected from the above short-chain polyols and the like, which is obtained by transesterification of diallyl carbonate, dialkyl carbonate or ethylene carbonate. Specifically, poly-1,6-hexamethylene carbonate, poly-2,2'-bis (4-hydroxyhexyl) propane carbonate and the like are industrially produced and easily available.

Further, the polycarbonate polyol can also be produced by a so-called phosgene method (or a solvent method).

In addition, vinyl-based polyols such as acrylic polyols obtained by copolymerizing acrylic monomers having hydroxyl groups such as β-hydroxyethyl acrylate and β-hydroxylethyl methacrylate with acrylic acid esters, poly (1,4-butadiene) , Poly (1,2
-Butadiene), castor oil-based polyols such as polypropylene glycol ricinoleate, silicone polyols, and polyolefin-based polyols.

These polyols can be used in combination of two or more.

(I) a vinyl chloride monomer as described above or (ii)
When a mixture of a vinyl chloride monomer and another monomer is polymerized in an aqueous medium containing a polyol as described above, a polyol-containing vinyl chloride polymer is obtained. In this case, the polyol is preferably used in an amount of 5 to 200% or less based on the vinyl chloride monomer. The polymerization reaction is carried out in a temperature range of 30 to 70 ° C, preferably 40 to 70 ° C.

When performing the above-mentioned polymerization reaction, it is preferable that a suspending agent is present in an aqueous medium.

In conducting the above polymerization reaction, a polymerization initiator is usually used.

In conducting the polymerization reaction, it is desirable that the polyol be present in the aqueous medium before the addition of the vinyl chloride monomer. In the aqueous medium, a processing stabilizer for vinyl chloride monomer, metal soap and the like can be added.

When the polyol-containing vinyl chloride polymer prepared as described above is reacted with an isocyanate compound, and if necessary, an additive is blended, a polymer composition for forming a base material used in the present invention is formed. Things are obtained.

As the isocyanate compound, specifically, 2,4-
Tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 1-chlorophenylene-2,4-
Diisocyanate, 1,5-naphthalene diisocyanate, methylene bisphenylene-4,4'-diisocyanate, m-xylene diisocyanate, p-xylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, 4,4'-methylene bis (cyclohexyl isocyanate), isophorone diisocyanate Diisocyanates such as trimethylhexamethylene diisocyanate, triisocyanates such as 1,6,11-undecane triisocyanate, lysine ester triisocyanate, 4-isocyanatomethyl-1,8-octamethyl diisocyanate, and polyphenylmethane polyisocyanate Of polyfunctional isocyanates and dimers or trimers of these isocyanate compounds, as described above. Short chain, long chain polyols or water, isocyanate compounds such as isocyanate compound having a terminal isocyanate group obtained by reacting an active hydrogen compound such as an amino compound and the isocyanate compound is used.

In addition, as the isocyanate compound, active methylene compounds, oximes, lactams, phenols, alkylphenols, blocking stabilization of the above isocyanate compound by a blocking agent such as a basic nitrogen-containing compound, block by regenerating the isocyanate group by heating. Isocyanate compounds can also be used.

Furthermore, as the isocyanate compound, it is also possible to use the above-mentioned isocyanate compound as a mixture of several kinds, and it is also possible to use a solution in which the above-mentioned isocyanate compound is dissolved in a solvent.

To blend additives such as isocyanate compounds and, if necessary, stabilizers, lubricants, coloring agents, and fillers into the polyol-containing vinyl chloride polymer, use a ribbon blender, a Warner-type kneader, a Bonnie mixer, a Henschel mixer, or the like. Mixers can be used. Blending is performed by cold blending at room temperature or hot blending by heating to 70 to 150 ° C by a jacketed blender.

At the time of blending, a part of the isocyanate group of the compounded isocyanate compound reacts with the hydroxyl group of the polyol to form a urethane bond. This phenomenon is particularly noticeable in the case of hot blending, where isocyanate groups form urethane bonds by reacting with hydroxyl groups of polyols and simultaneously form dimerization by allophanate bonds and uretidinedione bonds or biuret bonds by reaction with moisture. However, a composition containing no apparently active isocyanate groups is obtained.

Isocyanate compounds due to these side reactions are 120
The ring is opened and dissociated at a high temperature of not less than ° C., so that it acts as an effective isocyanate group at the time of thermoforming, participates in the reaction with the polyol in the composition, and is reorganized by urethane bonding.

Such a polyol-containing vinyl chloride polymer [A]
The base material sheet of the pressure-sensitive adhesive sheet for attaching a wafer according to the present invention can be obtained by molding a polymer composition containing a reaction product of the compound and the isocyanate compound [B] and, if necessary, an additive into a sheet. .

Such a base sheet, when the sheet thickness is 80 μm, the initial modulus is preferably 100 kg / cm ² or more, the breaking elongation is preferably 300% or more, and the breaking strength is preferably 220 kg / cm ^2. cm ² or more, with a stress relaxation of 70
% (After 3 minutes). The UV transmittance of the substrate sheet is preferably 50% or more at 270 to 450 nm.

The thickness of the substrate film of the pressure-sensitive adhesive sheet used in the present invention is desirably 30 to 300 μm, preferably 60 to 200 μm, and more preferably 80 to 100 μm.

In the pressure-sensitive adhesive sheet of the present invention, as described below, upon use thereof, radiation irradiation such as EB or UV is performed, so that the base film used in the present invention is transparent when used with EB irradiation It is not necessary, but when using with UV irradiation, it must be a transparent material.

Since the polymer film 2 used as such a base material does not contain a plasticizer, the plasticizer does not migrate to the pressure-sensitive adhesive to soften the pressure-sensitive adhesive layer, and is excellent in stress relaxation, The adhesive sheet does not bend due to the elongation of the adhesive sheet, and exhibits sufficient extensibility at the time of expanding, so that the wafer chips can be reliably picked up.

The pressure-sensitive adhesive layer 3 is provided on the substrate 2 as described above, and the pressure-sensitive adhesive layer 3 is formed including a pressure-sensitive adhesive and a radiation polymerizable compound.

As the pressure-sensitive adhesive, conventionally known pressure-sensitive adhesives can be widely used, but an acrylic pressure-sensitive adhesive is preferable, and specifically, selected from a homopolymer and a copolymer having an acrylate ester as a main constituent monomer unit. Copolymers with acrylic polymers and other functional monomers and mixtures of these polymers are used. For example, acrylates include ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, and the like. Can be preferably used.

In order to further enhance the compatibility with the oligomer described below,
Acrylic acid or methacrylic acid, acrylonitrile,
A monomer such as vinyl acetate may be copolymerized. The molecular weight of the acrylic polymer obtained by polymerizing from these monomers is 2.0 × 10 ^{5 to} 10.0 × 10 ⁵ , preferably,
It is 4.0 × 10 ^{5 to} 8.0 × 10 ⁵ .

As the radiation polymerizable compound, for example,
-196,956 and low molecular weight compounds having at least two or more photopolymerizable carbon-carbon double bonds in a molecule capable of forming a three-dimensional network by irradiation as disclosed in JP-A-60-223,139. Widely used, specifically,
Trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate or 1,4-butylene glycol diacrylate, 1,6-hexane Diol diacrylate, polyethylene glycol diacrylate, commercially available oligoester acrylate and the like are used.

Further, as the radiation polymerizable compound, a urethane acrylate oligomer can be used in addition to the acrylate compound as described above. The urethane acrylate oligomer is a polyol compound such as a polyester type or a polyether type, and a polyvalent isocyanate compound such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4 -Acrylate or methacrylate having a hydroxyl group, such as 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, on a terminal isocyanate urethane prepolymer obtained by reacting xylylene diisocyanate, diphenylmethane 4,4-diisocyanate, or the like. , 2-hydroxypropyl methacrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, and the like. This urethane acrylate oligomer has a carbon-
It is a radiation polymerizable compound having at least one carbon double bond.

As such a urethane acrylate-based oligomer, in particular, when those having a molecular weight of 3,000 to 30,000, preferably 3,000 to 10,000, and more preferably 4,000 to 8,000 are used, even when the surface of the semiconductor wafer is rough, the chip surface is picked up when the wafer chip is picked up. It is preferable because the adhesive does not adhere. When a urethane acrylate oligomer is used as the radiation polymerizable compound, JP-A-60-19
As compared with the case of using a low molecular weight compound having at least two photopolymerizable carbon-carbon double bonds in the molecule as disclosed in US Pat. No. 6,956, an extremely excellent pressure-sensitive adhesive sheet can be obtained. That is, the adhesive force of the pressure-sensitive adhesive sheet before the irradiation is sufficiently large, and the adhesive force is sufficiently reduced after the radiation irradiation, so that the pressure-sensitive adhesive does not remain on the chip surface when the wafer chip is picked up.

The mixing ratio of the acrylic pressure-sensitive adhesive and the urethane acrylate-based oligomer in the pressure-sensitive adhesive of the present invention may be such that the urethane acrylate-based oligomer is used in an amount of 50 to 900 parts by weight based on 100 parts by weight of the acrylic pressure-sensitive adhesive. preferable. In this case, the resulting pressure-sensitive adhesive sheet has a large initial adhesive strength, and the adhesive strength is significantly reduced after irradiation, so that wafer chips can be easily picked up from the pressure-sensitive adhesive sheet.

If necessary, the pressure-sensitive adhesive layer 3 may contain, in addition to the pressure-sensitive adhesive and the radiation-polymerizable compound, a compound that is colored by irradiation with radiation. By including a compound to be colored in the pressure-sensitive adhesive 3 by such radiation irradiation, the sheet is colored after the pressure-sensitive adhesive sheet is irradiated with the radiation, and therefore, the detection accuracy when detecting a wafer chip by an optical sensor is improved. As a result, malfunction does not occur when picking up a wafer chip. In addition, an effect is obtained that it is immediately possible to visually determine whether or not radiation has been applied to the adhesive sheet.

The compound that is colored by irradiation with radiation is a compound that is colorless or pale before irradiation with radiation, but is a compound that becomes colored by irradiation with radiation. A preferred specific example of this compound is a leuco dye. As leuco dyes,
Conventional triphenylmethane, fluoran, phenothiazine, auramine, and spiropyran compounds are preferably used. Specifically, 3- [N- (p-tolylamino)]-7-anilinofluoran, 3- [N- (p-
Tolyl) -N-methylamino] -7-anilianofluoran, 3- [N- (p-tolyl) -N-ethylamino]
-7-anilinofluoran, 3-diethylamino-6
Methyl-7-anilinofluoran, crystal violet lactone, 4,4 ', 4 "-trisdimethylaminotriphenylmethanol, 4,4', 4" -trisdimethylaminotriphenylmethane and the like.

Developers preferably used with these carp dyes include conventionally used phenol-formalin resin prepolymers, aromatic carboxylic acid derivatives, electron acceptors such as activated clay, and further change the color tone. In this case, various known color formers can be used in combination.

Such a compound which is colored by irradiation with radiation may be once dissolved in an organic solvent or the like and then included in the adhesive layer, or may be finely powdered and included in the pressure-sensitive adhesive layer. This compound is desirably used in an amount of 0.01 to 10% by weight, preferably 0.5 to 5% by weight in the pressure-sensitive adhesive layer.
When the compound is used in an amount exceeding 10% by weight, the radiation applied to the pressure-sensitive adhesive sheet is excessively absorbed by the compound, and thus the curing of the pressure-sensitive adhesive layer may be insufficient. When used in an amount of less than 0.01% by weight, the pressure-sensitive adhesive sheet may not be sufficiently colored during irradiation, and malfunction may easily occur when picking up a wafer chip.

In some cases, the light-scattering inorganic compound powder may be contained in the pressure-sensitive adhesive layer 3 in addition to the pressure-sensitive adhesive and the radiation-polymerizable compound as described above.

By including such a light-scattering inorganic compound powder in the pressure-sensitive adhesive layer 3, even if the surface of an adherend such as a semiconductor wafer becomes gray or black for some reason, the pressure-sensitive adhesive sheet is irradiated with radiation such as ultraviolet rays. Then
Even in the grayed or blackened portion, the adhesive force is sufficiently reduced, so that the adhesive does not adhere to the wafer chip surface when picking up the wafer chip,
In addition, the effect of having a sufficient adhesive strength before the irradiation of radiation can be obtained.

The light-scattering inorganic compound is a compound capable of irregularly reflecting the radiation when irradiated with radiation such as ultraviolet (UV) or electron beam (EB). , Alumina powder, silica alumina powder, mica powder and the like. The light-scattering inorganic compound preferably reflects the above-described radiation almost completely, but of course, a compound that absorbs the radiation to some extent can also be used.

The light-scattering inorganic compound is preferably in a powder form,
The particle size is desirably about 1 to 100 μm, preferably about 1 to 20 μm. It is desirable that the light-scattering inorganic compound is used in an amount of 0.1 to 10% by weight, preferably 1 to 4% by weight in the pressure-sensitive adhesive layer. When the compound is used in an amount of more than 10% by weight in the pressure-sensitive adhesive layer, the adhesive strength of the pressure-sensitive adhesive layer may be reduced. On the other hand, when the compound is less than 0.1% by weight, the surface of the semiconductor wafer becomes gray or In the case of blackening, even if the part is irradiated with radiation, the adhesive strength may not be sufficiently reduced and the adhesive may remain on the wafer surface during pickup.

The pressure-sensitive adhesive sheet obtained by adding the light-scattering inorganic compound powder to the adhesive layer is used even when the semiconductor wafer surface is grayed or blackened for some reason. It is considered that the reason why the adhesive strength is sufficiently reduced even in this portion when the radiation is applied to the substrate is as follows. That is, the pressure-sensitive adhesive sheet 1 according to the present invention has the pressure-sensitive adhesive layer 3
However, when the pressure-sensitive adhesive layer 3 is irradiated with radiation, the radiation-polymerizable compound contained in the pressure-sensitive adhesive layer 3 is cured and its adhesive strength is reduced. However, a gray or black portion may be formed on the semiconductor wafer surface for some reason. In such a case, when the adhesive layer 3 is irradiated with radiation, the radiation passes through the adhesive layer 3 and reaches the wafer surface. However, if there is a gray or black portion on the wafer surface, the radiation is applied to this portion. It is absorbed and no longer reflected. For this reason, the radiation that should be used for curing the pressure-sensitive adhesive layer 3 is absorbed in the grayed or blackened portions, and the curing of the pressure-sensitive adhesive layer 3 becomes insufficient, and the adhesive strength is not sufficiently reduced. become. Therefore, it is considered that the adhesive may adhere to the chip surface when the wafer chip is picked up.

However, when the light-scattering inorganic compound powder is added to the pressure-sensitive adhesive layer 3, the irradiated radiation collides with the compound before reaching the wafer surface and changes its direction. Therefore, even if there is a grayed or blackened part on the wafer chip surface, the diffusely reflected radiation penetrates sufficiently into the area above this part, and the grayed or blackened part is also sufficiently cured. I do. For this reason, by adding the light-scattering inorganic compound powder to the pressure-sensitive adhesive layer, even if there is a grayed or blackened portion on the semiconductor wafer surface for any reason, the pressure-sensitive adhesive layer does not cure at this portion. Therefore, the adhesive does not adhere to the chip surface when the wafer chip is picked up.

In the present invention, a heat-expandable compound may be added to the pressure-sensitive adhesive layer 3 in addition to the pressure-sensitive adhesive and the radiation-polymerizable compound as described above.

The term "thermally expandable compound" means a compound whose volume is greatly expanded by heating, and is usually heated to about 50 to 200 ° C, preferably about 80 to 140 ° C, 1.5 to 10 times the initial volume, preferably about 3 to 10 times the initial volume. A compound that swells up to 5-fold is meant.

As such a heat-expandable compound, for example, a foamable resin is preferably used, and specifically, a product name “Expancel” sold by Nippon Ferrite Co., Ltd. is used.

This heat-expandable compound is preferably dispersed in the pressure-sensitive adhesive layer 3 in the form of a powder having a particle size of about 5 to 30 μm. At this time, an organic solvent such as ethyl acetate can be used. The heat-expandable compound is preferably used in the pressure-sensitive adhesive layer 3 in an amount of 1 to 20% by weight, preferably 3 to 10% by weight. When the thermal expandable compound is used in such an amount, even if the surface of the semiconductor wafer is slightly rough or a blackened portion is formed on the wafer surface for some reason, the adhesive is applied to the wafer chip after irradiation. The wafer chip can be picked up without the adhesion of the wafer chip. In addition, when the heat-expandable compound is used in an amount exceeding 20% by weight, the adhesive strength of the adhesive before irradiation decreases, and
This compound may adhere to the wafer surface.
When used in an amount of less than% by weight, the effect of adding the thermally expandable compound may be insufficient.

Further, in the present invention, abrasive grains may be dispersed in the base material. This abrasive has a particle size of 0.5 to 100 μm, preferably 1 to 100 μm.
50 μm and a Mohs hardness of 6 to 10, preferably 7 to 10
It is. Specifically, green carborundum, artificial corundum, optical emery, white alundum, boron carbide, chromium (III) oxide, cerium oxide,
Diamond powder or the like is used. Such abrasive grains are preferably colorless or white. Such paper particles are present in the substrate 2 in an amount of 0.5 to 70% by weight, preferably 5 to 50% by weight.
It is present in an amount of% by weight.

Such abrasive grains are particularly preferably used when the cutting blade is used at such a depth as to cut not only into the wafer but also into the substrate 2.

By including such abrasive grains in the base material,
Even if the cutting blade cuts into the base material and the adhesive adheres to the cutting blade, clogging can be easily removed by the polishing effect of the abrasive grains.

Furthermore, in the present invention, an expanding agent may be added to the adhesive layer 3 in addition to the adhesive.

The following compounds are specifically used as such an expanding agent.

(A) higher fatty acids or derivatives thereof stearic acid, lauric acid, ricinoleic acid, naphthenic acid, 2-ethylhexoylic acid, oleic acid, linoleic acid, myristic acid, palmitic acid, isostearic acid,
Esters of the above acids, such as hydroxystearic acid and behenic acid.

Metal salts of the above acids such as Li, Mg, Ca, Sr, Ba, Cd,
Zn, Pb, Sn, K, and Na salts, or multiple metal salts containing two or more of the above metals.

(B) Compounds having a Si or siloxane structure.

 Silicone oil and the like.

(C) a compound containing fluorine.

(D) an epoxy compound.

Epoxy methyl stearate, butyl epoxy stearate, epoxidized linseed oil, butyl fatty acid, epoxidized tetrahydronaphthalate, bisphenol A diglycidyl ether, epoxidized butadiene.

(E) Polyol compounds or derivatives thereof Glycerin, diglycerin, sorbitol, mannitol, xylitol, pentaerythritol, dipentaerythritol, trimethylolpropane, polyethylene glycol, polyvinyl alcohol and the like.

 A nitrogen-containing or sulfur-containing or metal complex of the above compound.

(F) β-diketo compounds or derivatives thereof acetoacetate, dehydroacetic acid, acetylacetone, benzoylacetone, trifluoroacetylacetone, stearoylbenzoylmethane, dibenzylmethane.

 Metal complexes of the above compounds.

(G) phosphites triphenylphosphine, diphenylphosphine,
Phenyl acid, hydrogenated bisphenol A phosphite polymer, ( _Where R is C _n H _{2n + 1} ) (In the formula, R is C _n H _{2n + 1.} ) When such an expanding agent is incorporated into the pressure-sensitive adhesive layer 3, a sufficient space can be provided between the chips provided on the base sheet, Therefore, adjacent chips do not come into contact with each other or a positional shift does not occur, and therefore, malfunction does not occur during chip pickup. In particular, when a radiation polymerizable compound is allowed to coexist in the pressure-sensitive adhesive layer, a remarkable effect is observed.

The expanding agent as described above is desirably used in the adhesive layer 3 in an amount of 0.1 to 10% by weight, preferably 0.5 to 6% by weight.

By mixing an isocyanate-based curing agent in the above-mentioned pressure-sensitive adhesive, the initial adhesive strength can be set to an arbitrary value. As such a curing agent, specifically, a polyvalent isocyanate compound such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-
Xylylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate,
3-Methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, lysine isocyanate and the like are used.

Furthermore, in the case of UV irradiation in the above-mentioned pressure-sensitive adhesive, by mixing a UV initiator, the polymerization curing time by UV irradiation and the UV irradiation can be reduced.

Specific examples of such a UV initiator include benzoin, benzoin methyl ether, and benzoin ethyl ether. Benzoin isopropyl ether, benzyl diphenyl sulfide, tetramethyl thiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloranthraquinone and the like.

Hereinafter, a method for using the pressure-sensitive adhesive sheet according to the present invention will be described.

When the release sheet 4 is provided on the upper surface of the pressure-sensitive adhesive sheet 1 according to the present invention, the release sheet 4 is removed, and then the pressure-sensitive adhesive layer 3 of the pressure-sensitive adhesive sheet 1 is placed on the pressure-sensitive adhesive sheet 1 so as to face up.
As shown in the figure, a semiconductor wafer A to be diced is attached to the upper surface of the pressure-sensitive adhesive layer 3. Various processes such as dicing, cleaning, drying, and expanding are added to the wafer A in this state. At this time, the wafer chips are sufficiently adhered and held on the pressure-sensitive adhesive sheet by the pressure-sensitive adhesive layer 3, so that the wafer chips do not fall off during the respective steps.

Next, each wafer chip is picked up from the adhesive sheet and mounted on a predetermined base.
As shown in the figure, the adhesive layer 3 of the adhesive sheet 1 is irradiated with ionizing radiation B such as ultraviolet (UV) or electron beam (EB), and the radiation polymerizable compound contained in the adhesive layer 3 is polymerized and cured. Let me know. When the pressure-sensitive adhesive layer 3 is irradiated with radiation to polymerize and cure the radiation-polymerizable compound, the adhesive force of the pressure-sensitive adhesive is greatly reduced, and only a slight adhesive force remains.

Irradiation to the pressure-sensitive adhesive sheet 1 is performed by the pressure-sensitive adhesive layer 3 of the substrate 2.
It is preferable to perform the process from the surface on which is not provided. Therefore, as described above, when UV is used as the radiation, the substrate 2 needs to be light-transmitting, but when EB is used as the radiation, the substrate 2 does not necessarily need to be light-transmitting. Absent.

After irradiating the adhesive layer 3 in the portion where the wafer chips A ₁ , A ₂ ... Are provided with radiation to reduce the adhesive strength of the adhesive layer 3, the adhesive sheet 1 is removed from the pickup station ( 5), and as shown in FIG. 5, chips A ₁ ... To be picked up by the push-up needle rod 5 from the lower surface of the substrate 2 are pushed up according to a conventional method.
The chips A ₁ are picked up by, for example, air tweezers 6, and are mounted on a predetermined base. When the wafer chips A ₁ , A _2, ... Are picked up in this manner, the chips can be easily picked up without any adhesive on the wafer chip surface, and chips of good quality without contamination can be obtained. can get. Irradiation is
It can also be performed at the pickup station.

Irradiation is performed over the entire surface of the wafer A
It is not always necessary to irradiate each time. Irradiation may be partially performed several times. For example, each of the wafer chips A ₁ , A _2, ... To be picked up corresponds to this. After irradiating with a radiation irradiating tube that irradiates only the back surface to reduce the adhesive force of only the adhesive at that portion, the wafer chips A ₁ , A _2, ... . FIG. 6 shows a modification of the above-described radiation irradiation method. In this case,
The inside of the push-up needle rod 5 is hollow, and a radiation source 7 is provided in the hollow part so that radiation irradiation and pickup can be performed at the same time, so that the apparatus can be simplified and the pickup operation time can be reduced. Can be shortened.

Effect of the Invention In the wafer pressure-sensitive adhesive sheet according to the present invention, [A] a monomer mixture of (i) a vinyl chloride monomer or (ii) a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer is used as a base material. A film comprising a polymer composition obtained by reacting a polyol-containing vinyl chloride polymer obtained by polymerization in an aqueous medium containing a polyol soluble in a vinyl monomer with [B] isocyanate is used. Therefore, the plasticizer does not migrate to the surface of the pressure-sensitive adhesive and softens the pressure-sensitive adhesive layer, is excellent in stress relaxation property, and does not cause bending of the pressure-sensitive adhesive sheet due to elongation of the pressure-sensitive adhesive sheet. In addition, since the base sheet is sufficiently stretched at the time of expanding, a sufficient space is provided between the chips, so that the wafer chips can be reliably picked up.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 100 parts by weight of an acrylic pressure-sensitive adhesive (copolymer of n-butyl acrylate and acrylic acid), 100 parts by weight of a urethane acrylate oligomer having a molecular weight of 8000, 10 parts by weight of a curing agent (diisocyanate), and UV curing 10 parts by weight of a reaction initiator (benzophenone-based) was mixed to form a pressure-sensitive adhesive composition.

This pressure-sensitive adhesive composition was prepared by mixing 50% by weight of a polyol-containing vinyl chloride polymer having a thickness of 100 μm as a base material with isocyanate.
The adhesive sheet of the present invention was prepared by applying a coating amount of 15 g / m ² to one surface of a film formed from the polymer composition obtained by reacting with 50% by weight and heating at 100 ° C. for 1 minute.

A 5-inch silicon wafer is stuck on the obtained pressure-sensitive adhesive sheet and adhered to a flat frame, and then diced into a 5 mm square with a diamond blade having a thickness of 50 μm, and then diced into a wafer portion only for 2 seconds from the base material surface. The adhesive sheet was irradiated with ultraviolet rays (illuminance: 200 mW / cm ² ), and then expanded by 80% using an expanding jig. After a lapse of 48 hours, the pressure-sensitive adhesive sheet did not come off the flat frame, and no slack was generated.

Example 2 After the dicing tape of Example 1 was left in an environment of 70 ° C. and a relative humidity of 60% for 7 days, wafer dicing, UV irradiation, and 80% expansion were performed in the same manner as in Example 1. The die bonding in the next step could be carried out without any problem without separation or sagging.

Comparative Example 1 The same operation was performed except that the base material of Example 1 was changed to soft PVC (containing 30% of a plasticizer). After 12 hours with 80% expansion,
The tape came off the flat frame.

In the same manner as in Example 2, the tape was left at 70 ° C. and 60% RH for 7 days, and then subjected to dicing, UV irradiation, and 80% expansion. Immediately after being mounted on the die bonder and picking up, chips were often left behind, probably due to softening of the adhesive.

[Brief description of the drawings]

1 and 2 are cross-sectional views of the pressure-sensitive adhesive sheet according to the present invention, and FIGS. 3 to 6 are explanatory diagrams when the pressure-sensitive adhesive sheet is used from a dicing step to a pickup step of a semiconductor wafer. . DESCRIPTION OF SYMBOLS 1 ... adhesive sheet, 2 ... base material, 3 ... adhesive layer, 4 ... release sheet, A ... wafer, B ... radiation.

Continuation of the front page (56) References JP-A-60-196956 (JP, A) JP-A-60-223139 (JP, A) JP-A-59-74178 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) C09J 7/00-7/04 H01L 21/68

Claims (1)

(57) [Claims] A pressure-sensitive adhesive sheet for attaching a wafer, comprising a pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive and a radiation-polymerizable compound applied on a substrate surface, wherein the substrate comprises: [A] (i) a vinyl chloride monomer or (Ii) a polyol-containing vinyl chloride-based polymer obtained by polymerizing a monomer mixture of a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer in an aqueous medium containing a polyol soluble in the vinyl chloride monomer; [B] A pressure-sensitive adhesive sheet for attaching a wafer, which is a film comprising a polymer composition obtained by reacting with an isocyanate.