JP4805549B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to an adhesive sheet used for, for example, cutting and separating (dicing) a wafer on which a circuit is formed for each circuit, and sticking and fixing the wafer in a pick-up process.

  Semiconductor wafers such as silicon and gallium arsenide, which are manufactured in a large diameter state, are cut and separated (diced) into element pieces, and then transferred to the next mounting step. At this time, the semiconductor wafer is subjected to dicing, cleaning, drying, pick-up, and mounting processes in a state of being previously attached to the pressure-sensitive adhesive sheet (pressure-sensitive adhesive sheet for dicing).

As this dicing pressure-sensitive adhesive sheet, a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer on a base film has been used. And the adhesive for forming the adhesive layer of the adhesive sheet for dicing is calculated | required by moderate adhesive force and elastic modulus.
In other words, this dicing adhesive sheet requires an adhesive force to securely hold the wafer when dicing the wafer, and if the holding is not complete, “chip scattering” occurs in which chips are peeled off during dicing. It becomes easy. However, when the adhesive force increases, a large force is required when picking up the diced chip, and picking up becomes impossible, or the chip breaks the chip or damages the back surface of the chip, causing a package crack.

Therefore, radiation-polymerizable monomers and oligomers are blended into the pressure-sensitive adhesive composition, or radiation-polymerizable polymers having a radiation-polymerizable functional group introduced into the side chain or main chain of the acrylic polymer are used alone or other acrylic polymers. It is used as a pressure-sensitive adhesive, and has sufficient adhesive strength to the wafer from the dicing process to the drying process. A dicing pressure-sensitive adhesive sheet capable of reducing the adhesive strength as much as possible is used. (For example, refer to Patent Documents 1 and 2.)
In general, since the adhesive has a low elastic modulus, the adhesive layer of the dicing adhesive sheet cannot suppress minute vibrations of the wafer (chip). This vibration affects between the dicing blade and the cut surface of the chip and causes chipping on the cut surface of the chip. This chipping reduces the bending strength of the chip itself, or entraps air in the package of the sealed IC, and easily causes package cracks.

In recent years, semiconductor wafers have been made thinner, but the thinner the thickness, the higher the possibility of chipping and cracking as described above. Rate and adhesive strength are required.
Furthermore, there is a demand that an adhesive used for bonding the chip to the chip substrate is formed into a sheet, and that the sheet-like adhesive is cut at the same time as the dicing of the wafer. When dicing a wafer with a sheet adhesive adhered, the adhesive layer of the dicing adhesive sheet is adhered to the sheet adhesive, from the interface between the adhesive layer of the dicing adhesive sheet and the sheet adhesive. A chip is picked up. In general, the adhesive strength of an adhesive tends to increase with respect to a resin film such as an adhesive, and therefore, a dicing adhesive sheet is required to have a wider margin in pick-up properties and adhesive strength.

In this way, the dicing adhesive sheet holds the chip with sufficient adhesive force when dicing the wafer to prevent chip scattering, suppresses wafer (chip) vibration and prevents chipping, and further dicing Whether the adhesive sheet is directly attached to the back surface (grind surface) of the wafer or the case where the adhesive sheet is attached via a resin film such as an adhesive, the pickup is performed reliably. There is a demand for minimizing the damage to the chips caused by.
However, it is difficult to make these properties coexist in the dicing pressure-sensitive adhesive sheet, and a plurality of dicing pressure-sensitive adhesive sheets that sacrifice any of the properties are selected and used depending on the situation.

JP-A-5-32946 JP-A-8-27239

  The present invention has been made in view of the prior art as described above. For example, when a wafer is diced, the chip is held with a sufficient adhesive force to prevent chip scattering and suppress vibration of the wafer (chip). An object of the present invention is to provide an adhesive sheet that can prevent chipping. In addition, even if it is directly attached to the wafer back surface (grind surface) as a pressure-sensitive adhesive sheet for dicing, it is adhered by energy ray irradiation even when it is attached via a resin film such as an adhesive. It is an object of the present invention to provide an adhesive sheet that can be reliably picked up after reducing the force and that can minimize damage to the chip due to the pickup.

  As a result of intensive studies to achieve the above object, the present inventors have developed a pressure-sensitive adhesive composition mainly composed of a conventional adhesive acrylic copolymer and an energy ray-curable monomer or oligomer. Furthermore, it has been found that by adding a vinyl acetate copolymer, the pick-up force is extremely low while the chipping resistance is excellent. The present invention has been completed based on such findings.

That is, the present invention
(1) A pressure-sensitive adhesive sheet comprising a base film and a pressure-sensitive adhesive layer formed thereon, wherein the pressure-sensitive adhesive layer does not contain a structural unit derived from an adhesive vinyl acetate monomer. [Component (A)], vinyl acetate copolymer [component (B)] containing 50 to 99.99% by mass of structural units derived from vinyl acetate monomer, and energy ray-curable monomer or oligomer [component (C) ], A pressure-sensitive adhesive sheet formed of a pressure-sensitive adhesive composition containing as a main component,
(2) The pressure-sensitive adhesive sheet according to the above (1), wherein the glass transition temperature (Tg) of the component (A) is −10 ° C. or lower,
(3) The compounding ratio (A) / (B) of the component (A) and the component (B) is 5-70 parts by mass / 95-30 parts by mass, and the compounding ratio of the component (C) is the component (A). The pressure-sensitive adhesive sheet according to (1) or (2), wherein the pressure-sensitive adhesive sheet is 1-1000 parts by mass with respect to 100 parts by mass in total with the component (B),
(4) Component (A) is a structural unit derived from a (meth) acrylic acid alkyl ester monomer having 4 or more alkyl groups [Component (A1)], a crosslinkable functional group-containing monomer [Component (A2)] And a polymer containing a structural unit derived from a polymerizable monomer (A3) other than components (A1) and (A2), and the content ratio of each structural unit (A1) / (A2) / ( A3) is 40 to 95% by mass / 0.01 to 30% by mass / 5 to 40% by mass, The pressure-sensitive adhesive sheet according to any one of the above (1) to (3),
(5) Component (A) is a structural unit derived from a (meth) acrylic acid alkyl ester monomer having an alkyl group having 4 or more carbon atoms [component (A1)] and a crosslinkable functional group-containing monomer [component (A2)]. (1), wherein the content ratio (A1) / (A2) of each structural unit is 40 to 95% by mass / 0.01 to 30% by mass. Or the pressure-sensitive adhesive sheet according to (2),
(6) Component (B) other than structural units derived from vinyl acetate [component (B1)], structural units derived from crosslinkable functional group-containing monomer [component (B2)], and components (B1) and (B2) It is a polymer containing a structural unit derived from the polymerizable monomer (B3), and the content ratio (B1) / (B2) / (B3) of each structural unit is 50 to 99.5% by mass / 0.01 to 30 The pressure-sensitive adhesive sheet according to any one of the above (1) to (3), wherein the pressure-sensitive adhesive sheet is mass% / 1 to 40 mass%, and
(7) Component (B) is a polymer containing a structural unit derived from vinyl acetate [component (B1)] and a structural unit derived from a crosslinkable functional group-containing monomer [component (B2)], and each structural unit The pressure-sensitive adhesive sheet according to any one of the above (1) to (3), wherein the content ratio (B1) / (B2) is 50 to 99.5% by mass / 0.01 to 30% by mass <<br/>

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive sheet which hold | maintains a chip | tip with sufficient adhesive force at the time of dicing of a wafer, prevents chip scattering, suppresses the vibration of a wear (chip | tip), and can prevent a chipping can be provided. In addition, even if it is directly attached to the wafer back surface (grind surface) as a pressure-sensitive adhesive sheet for dicing, it is adhered by energy ray irradiation even when it is attached via a resin film such as an adhesive. It is possible to provide an adhesive sheet that can be reliably picked up after the force is reduced and that can minimize damage to the chip due to the pickup.

  In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer contains a tacky acrylic copolymer as the component (A) and 50 to 99.99 mass% of structural units derived from the vinyl acetate monomer as the component (B). It is formed of a pressure-sensitive adhesive composition containing a vinyl acetate copolymer and an energy ray-curable monomer or oligomer as component (C).

Component (A) is an adhesive acrylic copolymer.
Here, the adhesive means that the glass transition temperature (Tg) is −10 ° C. or lower, and the adhesive layer in which the component (A) and the component (B) are mixed is used for the wafer in the dicing process. It is necessary to have this Tg in order to produce the necessary tackiness for holding. Preferred Tg is −50 to −10 ° C.
The glass transition temperature (Tg) can be calculated from the monomer ratio of the monomer to be copolymerized and the value of Tg of the homopolymer by the monomer using the Fox equation.
Such an adhesive acrylic copolymer can be produced by a combination of various monomers, and has a crosslinkable property with a (meth) acrylic acid alkyl ester [component (A1)] having an alkyl group having 4 or more carbon atoms. What was obtained by copolymerizing a functional group-containing monomer [component (A2)] with a polymerizable monomer [component (A3)] other than components (A1) and (A2) as necessary is preferable.

  Here, (meth) acrylic acid alkyl ester having 4 or more carbon atoms in the alkyl group of component (A1) includes butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, (meth ) 2-ethylhexyl acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, and the like. Moreover, the alkyl ester which has alicyclic groups or aromatic groups, such as (meth) acrylic-acid cycloalkyl ester and (meth) acrylic-acid benzyl ester, may be sufficient. These may be used alone or in combination of two or more.

The crosslinkable functional group-containing monomer of component (A2) is a monomer having a polymerizable double bond and a functional group such as hydroxyl group, carboxyl group, amino group, substituted amino group, and epoxy group in the molecule. Preferably, a hydroxyl group-containing unsaturated compound or a carboxyl group-containing unsaturated compound is used.
Specific examples of such functional group-containing monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and (meth) acrylic. (Meth) acrylic acid hydroxyalkyl esters such as 2-hydroxybutyl acid, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate; acetoacetoxymethyl (meth) acrylate; (meth) acrylic acid Monoalkylaminoalkyl (meth) acrylates such as monomethylaminoethyl, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate, monoethylaminopropyl (meth) acrylate; acrylic acid, methacrylic acid, Crotonic acid, maleic acid, octopus Acid, ethylenically unsaturated carboxylic acids such as citraconic acid. These monomers may be used alone or in combination of two or more.

As the copolymerizable monomer of the component (A3), a (meth) acrylic acid alkyl ester having an alkyl group having 3 or less carbon atoms, specifically, methyl (meth) acrylate, ethyl (meth) acrylate and (meth) ) Vinyl esters such as propyl acrylate, acrylonitrile, acrylamide, vinyl acetate and vinyl butyrate.
These may be used alone or in combination of two or more.

In the component (A), the content ratio of the constituent unit derived from the (meth) acrylic acid alkyl ester monomer having 4 or more carbon atoms in the alkyl group [component (A1)] is such that the wafer is firmly fixed and the chips are not scattered by dicing. For this purpose, the content is preferably 40% by mass or more, and preferably 95% by mass or less in order to prevent picking up due to excessive adhesive force.
That is, the range of the content ratio of the structural unit derived from the component (A1) in the component (A) is preferably 40 to 95% by mass, particularly preferably 50 to 90% by mass.

  The structural unit derived from the crosslinkable functional group-containing monomer in the component (A) forms a three-dimensional cross-linking bond with the cross-linking agent and contributes to a reduction in chipping frequency and a reduction in pick-up force. For this reason, the content rate of a crosslinkable functional group containing monomer becomes like this. Preferably it is 0.01-30 mass%, Most preferably, it is 0.1-25 mass%.

  By introducing a copolymerizable monomer [component (A3)] into the component (A), the glass transition point (Tg) of the component (A) can be controlled, and the adhesive strength and cohesive strength of the adhesive layer itself can be controlled. By changing, it is possible to adjust the holding force and pick-up property of the chip. The content ratio of the structural unit derived from the component (A3) is preferably 40% by mass or less, and particularly preferably 5 to 30% by mass.

The mass average molecular weight of the component (A) is preferably 100,000 or more in order to eliminate adverse effects such as odor due to residual monomers and contamination on the adherend, and in order to obtain the viscosity necessary for applying the adhesive. 2 million or less is preferable.
That is, the mass average molecular weight of the component (A) is preferably 10 to 2 million, particularly preferably 200 to 1.5 million.

Component (B) comprises a vinyl acetate monomer [component (B1)] and a crosslinkable functional group-containing monomer [component (B2)], if necessary, polymerizable monomers other than components (B1) and (B2) It can be obtained by copolymerizing with [Component (B3)].
As the crosslinkable functional group-containing monomer of the component (B2), those exemplified above as the crosslinkable functional group-containing monomer [component (A2)] used for the production of the component (A) can be used.

The polymerizable monomer other than the components (B1) and (B2) in the component (B3) is used for improving the compatibility with the component (A), and is a (meth) acrylic acid ester, acrylonitrile, acrylamide. And vinyl esters such as vinyl acetate and vinyl butyrate.
Among these, (meth) acrylic acid alkyl esters are particularly preferable. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, ( Examples include pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and decyl (meth) acrylate.
These may be used alone or in combination of two or more.

If the content ratio of the structural unit derived from the vinyl acetate monomer [component (B1)] in the component (B) is 50% by mass or more, a reduction in chip pick-up force and a reduction in chipping frequency can be expected. However, in order to prevent the compatibility with the component (A) and the gel fraction from decreasing, the upper limit is 99.99% by mass.
That is, the range of the content ratio of the structural unit derived from the component (B1) in the component (B) needs to be 50 to 99.99% by mass, preferably 50 to 99.5% by mass, Preferably it is 60-95 mass%.

  In the component (B), the structural unit derived from the crosslinkable functional group-containing monomer forms a three-dimensional cross-linking with a cross-linking agent in the same manner as the component (A), thereby reducing the frequency of chipping and picking up. Contributes to reducing power. For this reason, the crosslinkable functional group-containing monomer content is preferably 0.01 to 30% by mass, and particularly preferably 0.1 to 25% by mass.

  The copolymerizable monomer [component (B3)] in the component (B) is preferably a content of 0 to 40% by mass, particularly preferably, in order to satisfy the compatibility between the component (A) and the component (B). Is a content ratio of 1 to 30% by mass.

The glass transition temperature (Tg) of the component (B) is preferably −10 ° C. or higher in order to prevent picking up due to excessive adhesive force, and in order to prevent the chips from being scattered by dicing and fixing the wafer firmly. 100 degrees C or less is preferable.
That is, the glass transition temperature (Tg) of the component (B) is preferably −10 to + 100 ° C., particularly preferably 0 to + 50 ° C.

The mass average molecular weight of the component (B) is preferably 10,000 or more in order to eliminate adverse effects such as odor due to residual monomers and contamination to the adherend, and in order to obtain a viscosity necessary for applying the adhesive. Therefore, 1 million or less is preferable.
That is, the mass average molecular weight of the component (B) is preferably 1 to 1,000,000, particularly preferably 100 to 800,000.

  The energy ray-curable monomer and oligomer of component (C) are polymerizable compounds having at least one carbon-carbon double bond in the molecule, such as acrylate monomers and acrylate oligomers. Specific examples of acrylate monomers include , Trimethylolpropane triacrylate, tetramethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate or 1,4-butylene glycol diacrylate, 1,6- Hexanediol diacrylate and the like can be mentioned. Specific examples of the acrylate oligomer include urethane acrylate and polyester acrylate. Epoxy acrylate, and polyethylene glycol diacrylate.

As for the compounding ratio (A) / (B) of a component (A) and a component (B) in an adhesive composition, it is desirable that it is 5-70 mass parts / 95-30 mass parts.
When the compounding ratio of the component (A) is excessive, the chipping property becomes inferior, and the adhesive force is increased, which may make it difficult to pick up. If the component (B) is excessive, the adhesiveness is inferior and the wafer cannot be fixed firmly, and the chips are likely to be scattered.
A particularly preferable blending ratio (A) / (B) is 10 to 60 parts by mass / 90 to 40 parts by mass.

As for the compounding ratio of a component (C) in an adhesive composition, it is desirable that it is 1-1000 mass parts with respect to a total of 100 mass parts of a component (A) and a component (B).
If the blending ratio of the component (C) is less than this range, there is a risk that the adhesive force does not decrease even if energy beam irradiation is performed and pickup may not be possible. There is a possibility that the layer becomes too brittle and an expansion for picking up cannot be performed.
A particularly preferable blending ratio of the component (C) is 10 to 200 parts by mass with respect to a total of 100 parts by mass of the component (A) and the component (B).

A crosslinking agent is mix | blended with an adhesive composition in order to add cohesion force with the said component (A), a component (B), and a component (C).
Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, metal chelate crosslinking agents, aziridine crosslinking agents, and amine resins.

  Here, examples of the isocyanate-based crosslinking agent include tolylene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), hydrogenated tolylene diisocyanate, diphenylmethane diisocyanate and the like. And polyhydric isocyanates and adducts of these polyisocyanates and polyhydric alcohols such as trimethylolpropane-modified TDI (TDI-TMP), trimethylolpropane-modified XDI (XDI-TMP), and the like.

  Examples of the epoxy-based crosslinking agent include ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine and the like. Examples of metal chelate crosslinking agents include chelate compounds composed of acetylacetone and acetone esters of divalent or higher metals such as aluminum, copper, iron, tin, zinc, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. Is mentioned.

  Examples of the metal chelate crosslinking agent include ethyl acetoacetate aluminum diisopropionate, aluminum tris (ethyl acetoacetate) and the like.

  Examples of the aziridine-based crosslinking agent include trimethylolpropane-tri-β-aziridinylpropionate, bisisophthaloyl-1- (2-methylaziridine), and the like.

These crosslinking agents may be used individually by 1 type, and may be used in combination of 2 or more types.
0.1-20 mass parts is preferable with respect to 100 mass parts of total amounts of a component (A) and a component (B), and, as for the quantity of a crosslinking agent, 0.5-10 mass parts is especially preferable.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention cures the energy line by irradiation and loses the adhesive force, and ultraviolet rays, electron beams, etc. are used as the energy rays.
The amount of irradiation varies depending on the type of energy beam, for example, about 50 to 200 mJ / cm ² is preferable in the case of ultraviolet rays, and about 10 to 1000 krad is preferable when an electron beam is used.

When ultraviolet rays are used as energy rays, the polymerization curing time and the amount of light irradiation can be reduced by mixing a photopolymerization initiator.
Specific examples of such photopolymerization initiators include 1-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyrate. Ronitrile, benzyl, dibenzyl, diacetyl, β-chloranthraquinone, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, 2,4,6-trimethylzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) ) -2,4,4-trimethyl-pentylphosphine oxide.

The blending amount of the photopolymerization initiator is preferably 0.1 parts by mass or more for obtaining sufficient curability with respect to 100 parts by mass of the component (C), and 10 parts by mass for obtaining sufficient storage stability. The following is preferred.
That is, the range of the blending amount of the photopolymerization initiator is preferably 0.1 to 10 parts by mass, particularly preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the component (C).

  In the pressure-sensitive adhesive composition, various additive components conventionally used in acrylic pressure-sensitive adhesive compositions can be contained as desired within a range that does not impair the object of the present invention.

The pressure-sensitive adhesive sheet of the present invention has a base film and a pressure-sensitive adhesive layer formed on the one surface using the pressure-sensitive adhesive composition described above.
The base film is not particularly limited, and any one conventionally used as a base film for an adhesive sheet can be appropriately selected and used. However, a plastic sheet such as a polyethylene film or a polypropylene film can be used. Polyolefin film such as polybutene film, polybutadiene film and polymethylpentene film; Polyester film such as polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film and polybutylene naphthalate film; Ethylene / vinyl acetate copolymer film , Ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, etc .; Cycloalkenyl film, vinyl chloride copolymer film, polyurethane film, ionomer resin film, polystyrene film, polycarbonate film, fluorine resin film is used.
The base film may be a multilayer film of these plastic sheets or a crosslinked film. Further, the base film may be colored or colorless as long as it has transparency to the energy rays to be used.

The thickness of the base film may be appropriately determined according to the purpose of use and the situation, but is usually in the range of 40 to 300 μm, preferably 60 to 200 μm.
In addition, when using a plastic sheet as the base film, for the purpose of improving the adhesiveness with the pressure-sensitive adhesive layer provided on the plastic sheet, it is possible to perform unevenness treatment by sandblasting or solvent treatment, or corona discharge treatment, as desired. , Oxidation treatment such as plasma treatment, ozone / ultraviolet irradiation treatment, flame treatment, chromic acid treatment, and hot air treatment can be performed. Moreover, primer treatment can also be performed.

In the pressure-sensitive adhesive sheet of the present invention, the above pressure-sensitive adhesive composition is used on one surface of the base film, and the thickness is usually in the range of 1 to 100 μm, preferably 2 to 60 μm, particularly preferably 3 to 30 μm. An adhesive layer is provided.
As a method of providing this pressure-sensitive adhesive layer, for example, a method of providing the pressure-sensitive adhesive layer by directly applying the pressure-sensitive adhesive composition on one surface of a base film by a known method, or the pressure-sensitive adhesive on a release sheet. A method of applying the composition by a known method to provide a pressure-sensitive adhesive layer, sticking it to one surface of a substrate film, and transferring the pressure-sensitive adhesive layer can be used.
In addition, as a coating method of an adhesive composition, the method of using a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater etc. can be mentioned, for example.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In addition, the performance of the adhesive sheet obtained in each example was evaluated according to the following procedure.
(1) Adhesive strength (SUS surface)
The adhesive sheet was attached to a mirror-finished stainless steel plate (SUS304) using a 2 kg rubber roller in an environment of 23 ° C. and 50% RH, left for 20 minutes, and then a universal tensile tester (Orion Tech Co., Ltd.). 180 degree peel strength was measured at a peel rate of 300 mm / min in accordance with JIS Z0237 adhesive strength measurement method using Tensilon UTM-4-100).
The adhesive strength of the adhesive sheet after ultraviolet irradiation (irradiation amount 70 mJ / cm ² ) was similarly measured.

(2) Adhesive strength (resin surface)
Except for changing the stainless steel plate to a 6-inch silicon wafer with a die attach sheet adhesive (DF-400 manufactured by Hitachi Chemical Co., Ltd.) laminated on the back, and sticking the adhesive sheet in contact with the adhesive surface The 180 degree peel strength was measured in exactly the same manner as (1) above.
The adhesive strength of the adhesive sheet after ultraviolet irradiation (irradiation amount 70 mJ / cm ² ) was similarly measured.

(3) Pickup force (grinding surface)
A 6-inch silicon wafer ground with a # 2000 grindstone was mounted on an adhesive sheet so that the ground surface and the adhesive layer were in contact with each other, fixed to a ring frame, and dicer (Tokyo Seimitsu Co., Ltd., AWD-4000, Disco). Using a dicing blade 27HECC manufactured by the company), dicing was performed to 5 mm × 5 mm under the conditions of a cutting speed of 80 mm / sec, a rotational speed of 40,000 rpm, and a cutting depth of 25 μm into the adhesive sheet.
Next, a needle was attached to the tip of the push-pull gauge, the tip was pushed down from the back side of the adhesive sheet turned upside down, and the force required to peel the tip was measured at 10 points, and the average value was taken as the pick-up force.

(4) Pickup force (resin surface)
A wafer in which a die attach sheet adhesive (DF-400 manufactured by Hitachi Chemical Co., Ltd.) is laminated on the ground surface of a 6 inch wafer is placed on the adhesive sheet so that the adhesive surface and the adhesive layer are in contact with each other. The pick-up force was measured in the same manner as in (4) above except that it was mounted.

(5) Chip scattering When dicing is performed in the same manner as in the above (4) pickup force (grinding surface) measurement, the number of chips that are peeled off from the adhesive layer during dicing is counted. The percentage (%) was chip scattering.

(6) Chipping Chips picked up by the same operation as in (4) Pickup force (grinding surface) measurement were observed, and chipping with a length of 50 μm or more in the depth direction toward the center on four sides occurred. The number of chips was counted, and the ratio (%) in the whole was defined as chipping.

In the following Examples and Comparative Examples, the following were used as the component (A), the component (B), the component (C), the photopolymerization initiator, and the crosslinking agent.
Adhesive acrylic copolymer (component (A))
(A1): The weight average molecular weight obtained by reacting 75% by mass of butyl acrylate, 10% by mass of methyl methacrylate, 10% by mass of acrylic acid and 5% by mass of 2-hydroxyethyl acrylate was 500,000 (Tg: -32 ° C) polymer.

Vinyl acetate copolymer [component (B)]
(B1): 80 mass% vinyl acetate, 18 mass% 2-ethylhexyl acrylate, 1 mass% acrylic acid and 1 mass% 2-hydroxyethyl methacrylate were reacted, and the mass average molecular weight was 440,000 (Tg : + 5 ° C) polymer.
(B2): 60 mass% vinyl acetate, 38 mass% 2-ethylhexyl acrylate, 1 mass% acrylic acid and 1 mass% 2-hydroxyethyl methacrylate were reacted, and the mass average molecular weight was 480,000 (Tg : -7 ° C) polymer.

Energy ray curable oligomer [component (C)]
(C1): Urethane acrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: ultraviolet UV1700B)

Photopolymerization initiator (d1): 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Specialty Chemicals, trade name: Irgacure 184)
Cross-linking agent (e1): Polyisocyanate-based cross-linking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate L)

Example 1
20 parts by mass of the component (a1), 80 parts by mass of the component (b1), 30 parts by mass of the component (c1), 0.28 parts by mass of the photopolymerization initiator and 3% by mass of the crosslinking agent are mixed to obtain a pressure-sensitive adhesive composition. It was.
This pressure-sensitive adhesive composition was applied to a release-treated surface of a peeled 38 μm-thick polyethylene terephthalate film so that the coating thickness after drying was 10 μm to form a pressure-sensitive adhesive layer. This pressure-sensitive adhesive layer was transferred to an 80 μm thick ethylene / methacrylic acid copolymer film to obtain a pressure-sensitive adhesive sheet.
Using the obtained adhesive sheet, adhesive force (SUS surface), adhesive force (resin surface), pickup force (grind surface), pickup force (resin surface), chip scattering, and chipping were evaluated, and the results are shown. It is shown in 2.

Examples 2 to 5 and Comparative Example 1
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the types and blending amounts of the components (A) to (E) were changed as shown in Table 1. Using the obtained adhesive sheet, it evaluated similarly to Example 1, and shows the result in Table 2.

The pressure-sensitive adhesive sheet of the present invention suppresses minute vibrations of the wafer during dicing and can prevent chipping (chipping) on the cut surface of the wafer, both for the semiconductor wafer itself and the resin film of the semiconductor wafer having a resin film, Adhesive strength is sufficient to hold the wafer while dicing and prevent the chips from scattering, and to reduce the adhesive strength sufficiently by energy irradiation to prevent chip cracking during pick-up It is suitable for use as a pressure-sensitive adhesive sheet for dicing.
Further, since the pressure-sensitive adhesive sheet of the present invention is excellent in pick-up property, it is also suitable for use as a pick-up sheet used only in the pick-up process. That is, since a wafer that has been chipped without using a ring frame is in a form that cannot be picked up by a pickup device, a pickup sheet is used. The pickup sheet is attached to the entire surface of the wafer, the outer periphery thereof is fixed to the ring frame, and all chips are transferred to the pickup sheet, so that supply to the pickup device is possible. Even in such applications, the pressure-sensitive adhesive sheet of the present invention is suitable.
The pressure-sensitive adhesive sheet of the present invention can be applied not only to semiconductor wafers such as glass, ceramics, green ceramics, and lump-sealed IC packages as adherends, but also to materials and materials for dicing and pickup. Furthermore, the pressure-sensitive adhesive sheet of the present invention is not limited to dicing and pickup, and is suitable for applications including a step of finally peeling and removing the pressure-sensitive adhesive sheet.

Claims (7)

  A pressure-sensitive adhesive sheet comprising a base film and a pressure-sensitive adhesive layer formed thereon, wherein the pressure-sensitive adhesive layer is an adhesive copolymer containing no structural unit derived from a vinyl acetate monomer [component ( A)], vinyl acetate copolymer [component (B)] containing 50 to 99.99% by mass of structural units derived from vinyl acetate monomer and energy ray curable monomer or oligomer [component (C)]. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive composition as a component. The pressure-sensitive adhesive sheet according to claim 1, wherein the glass transition temperature (Tg) of the component (A) is -10 ° C or lower. The compounding ratio (A) / (B) of the component (A) and the component (B) is 5 to 70 parts by mass / 95 to 30 parts by mass, and the compounding ratio of the component (C) is the component (A) and the component (B The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive sheet is 1-1000 parts by mass with respect to 100 parts by mass in total. The component (A) is derived from a structural unit derived from a (meth) acrylic acid alkyl ester monomer having 4 or more carbon atoms in the alkyl group [component (A1)], a crosslinkable functional group-containing monomer [component (A2)]. A polymer containing a structural unit and a structural unit derived from a polymerizable monomer (A3) other than the component (A1) and the component (A2), and the content ratio of each structural unit (A1) / (A2) / (A3) It is 40-95 mass% / 0.01-30 mass% / 5-40 mass%, The adhesive sheet of Claim 1 or 2 characterized by the above-mentioned. The component (A) is derived from a structural unit derived from a (meth) acrylic acid alkyl ester monomer having 4 or more carbon atoms in the alkyl group [component (A1)] and a crosslinkable functional group-containing monomer [component (A2)]. a polymer containing a constitutional unit, according to claim 1 or 2 content ratio of the respective structural units (A1) / (A2) is characterized in that 40 to 95 mass% / 0.01 to 30 mass% Adhesive sheet. Component (B) is a structural unit derived from vinyl acetate [component (B1)], a structural unit derived from a crosslinkable functional group-containing monomer [component (B2)], and polymerization other than component (B1) and component (B2) Polymer containing a structural unit derived from the functional monomer (B3), and the content ratio (B1) / (B2) / (B3) of each structural unit is 50 to 99.5% by mass / 0.01 to 30% by mass It is / 1-40 mass%, The adhesive sheet in any one of Claims 1-3 characterized by the above-mentioned. Component (B) is a polymer containing a structural unit derived from vinyl acetate [component (B1)] and a structural unit derived from a crosslinkable functional group-containing monomer [component (B2)], and the content ratio of each structural unit (B1) / (B2) is 50-99.5 mass% / 0.01-30 mass%, The adhesive sheet in any one of Claims 1-3 characterized by the above-mentioned.