KR20070019572A - Pressure-sensitive adhesive sheet, production method thereof and method of processing articles - Google Patents

Abstract

The present invention is to provide an adhesive sheet which can be used to process products such as wafers, which can follow the unevenness even if the generation of cutting chips is small and the height difference of the unevenness on the wafer surface is large. The adhesive sheet of this invention is an adhesive sheet which has an intermediate | middle layer and an adhesive layer in this order in one side of a base material, and an intermediate | middle layer has an initial elastic modulus of 0.5 N / mm <^2> or less, and loss tangent (tan delta) in 20 degreeC-70 degreeC The value of is 0.4 or more and the gel content is 30% or more.

Description

Adhesion sheet, its manufacturing method, and the processing method of the product TECHNICAL FIELD

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically the adhesive sheet which concerns on 1st Embodiment of this invention.

TECHNICAL FIELD The present invention relates to an adhesive sheet, and more particularly, to an adhesive sheet used for retaining or protecting a product in a process of precisely processing a semiconductor product such as a semiconductor wafer, an optical system product, or the like. Moreover, it is related with the manufacturing method of the adhesive sheet which manufactures this adhesive sheet, and the processing method of the product which processes a product using this adhesive sheet.

In the optical industry, the semiconductor industry, or the like, an adhesive sheet is used to precisely process an optical component such as a lens or a semiconductor product such as a semiconductor wafer to protect the surface of the wafer or the like and prevent damage.

For example, in the manufacturing process of a semiconductor chip, after slicing high-purity silicon single crystals or the like into wafers, predetermined circuit patterns such as ICs are etched and formed on the wafer surfaces to assemble integrated circuits, and then the back surface of the wafer is subjected to abrasion reduction. It has been produced by dicing into chips through the backgrinding process, or by dicing and polishing the back surface of the wafer after dicing by a dicing process. Since the semiconductor wafer itself is thin and soft, and the circuit pattern has irregularities, it is easy to be damaged when an external force is applied during the transfer to the backgrinding process or the dicing process. In addition, in the backgrinding step, the polishing process is performed while cleaning the back surface of the wafer with purified water in order to remove the generated abrasive sludge or to remove the heat generated during polishing. You need to stop it. Therefore, in order to protect a circuit pattern surface etc. and to prevent a breakage of a semiconductor wafer, operation | movement by adhering an adhesive sheet to a circuit pattern surface is performed. At the time of dicing, an adhesive sheet is attached to the wafer back side, the wafer is diced in an adhesive fixed state, and the formed chips are pushed up from the film substrate side to the needle to be picked up and fixed on the die pad. Let's do it. As an adhesive sheet used here, for example, Unexamined-Japanese-Patent No. 86-10242 discloses the film for silicon wafer processing which provided the adhesion layer in the surface of the base sheet of Shore D-type hardness of 40 or less. In addition, Japanese Patent Application Laid-Open No. 86-260629 discloses that an auxiliary film having a Shore D-type hardness greater than 40 is laminated on one surface of a base film having a Shore D-type hardness of 40 or less, and on the other surface of the base film. Disclosed is a film for processing a silicon wafer on which an adhesive layer is provided.

However, recently, the height difference of the unevenness | corrugation of the pattern surface of a semiconductor wafer becomes large, for example, in the wafer with a polyimide film, the height difference of the unevenness | corrugation is about 1-20 micrometers. In addition, a bad mark (bad mark) for recognizing a bad semiconductor chip has an unevenness having a height difference of about 10 to 70 μm, and a bump height formed on a patterned electrode is about 20 to 250 μm. . Therefore, when using a conventionally well-known adhesive sheet, an adhesive sheet cannot follow these unevenness | corrugation, and adhesion between an adhesive layer and a wafer surface becomes inadequate, As a result, peeling of an adhesive sheet at the time of wafer processing becomes In some cases, the number of debris or foreign matters enters into the pattern surface, processing errors, dimples, etc., chip scattering of the cut chips may occur, or the wafer may be broken.

For example, Japanese Patent Laid-Open No. 2001-203255 discloses a semiconductor wafer holding protective adhesive sheet having an intermediate layer having a specific elastic modulus and a specific gel fraction, but a semiconductor wafer having high irregularities having a high level difference. In the case of, the thickness of the intermediate layer had to be thickened in order to absorb the large irregularities.

However, there was a problem with the thick adhesive sheet. That is, the backgrinding process includes a step of cutting the adhesive sheet along the outer circumference of the wafer with a cutting blade after attaching the adhesive sheet to the pattern surface of the wafer, but applying heat to the cutting blade to facilitate cutting. The temperature is raised. Usually, the tip part temperature of a cutting blade is heated so that it may become 20 degreeC-70 degreeC. Therefore, after bonding an adhesive sheet to a wafer, when cutting an adhesive sheet along the outer periphery of a wafer, in the adhesive sheet with a thick thickness of an intermediate | middle layer, an intermediate | middle layer protruded from the side surface, and formed the lump (cutting debris).

The present invention has been made to solve the above problems, and the present invention is, for example, an adhesive sheet capable of following the unevenness even when the unevenness of the uneven surface of the semiconductor wafer surface is large. An object of the present invention is to provide an adhesive sheet with little occurrence of cutting chips of the adhesive sheet. Moreover, another object of this invention is to provide the manufacturing method of the adhesive sheet which manufactures this adhesive sheet, and the processing method of the product which processes a product etc. using this adhesive sheet.

The adhesive sheet of this invention is an adhesive sheet which has an intermediate | middle layer and an adhesive layer in this order in one side of a base material, The said intermediate | middle layer has an initial elasticity modulus of 0.5 N / mm <^2> or less, and loss tangent in 20 degreeC-70 degreeC (tan δ) value is 0.4 or more, and the gel content is 30% or more.

Here, the intermediate layer is preferably formed using an acrylic polymer.

In addition, the intermediate layer is preferably formed by irradiating radiation. In this invention, it is preferable that the said irradiation amount of the said ultraviolet-ray is 100 mJ / cm <^2> or more and 5000mJ / cm <^2> or less.

In the present invention, the pressure-sensitive adhesive layer is preferably formed using a radiation-curable acrylic polymer having a carbon-carbon double bond in the molecule.

Moreover, it is preferable that ratio (t1 / t2) of the thickness t1 of the said intermediate | middle layer and the thickness t2 of the said adhesive layer is 0.01 or more and 0.5 or less.

In the present invention, the pressure-sensitive adhesive layer may further have a peeling separator.

The adhesive sheet of the present invention can be used for semiconductor wafer processing. The adhesive sheet for semiconductor wafer processing is used for holding and / or protecting a product in a process of precisely processing a semiconductor wafer.

In the method for producing a pressure sensitive adhesive sheet of the present invention, an initial elastic modulus is 0.5 N / mm ² or less, and is applied at one side of the base material by applying a mixture containing a radically polymerizable monomer to one side of the substrate and irradiated with radiation, and at 20 ° C. to 70 ° C. The loss tangent (tan δ) is 0.4 or more, the gel powder is characterized in that an intermediate layer of 30% or more is formed, and an adhesive layer is formed on the intermediate layer.

Here, it is preferable that the said radically polymerizable monomer is an acryl-type monomer.

The method of using the pressure sensitive adhesive sheet of the present invention is characterized in that the pressure sensitive adhesive sheet is attached to a product to be precisely processed and precisely processed in a retained and / or protected state.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The adhesive sheet of this invention is an adhesive sheet which has a base material, an intermediate | middle layer, and an adhesive layer in this order. The intermediate layer has an initial elastic modulus of 0.5 N / mm ² or less, a value of loss tangent (tan δ) at 20 ° C to 70 ° C of 0 or more, and a gel fraction of 30% or more.

When the initial modulus of the intermediate layer exceeds 0.5 N / mm ² , it is impossible to sufficiently follow the unevenness of the surface of the semiconductor wafer, and the semiconductor wafer is easily broken or dimples during the reduction.

In this invention, an initial elastic modulus is calculated | required as follows. That is, a tensile tester (Autograph AGS-50D manufactured by Shimadzu Corporation) was used for a test sample produced so that the cross-sectional area of the test sample (middle layer) was 1 mm ² and the length was 10 mm, and the tensile speed was 300 mm / min. A tensile test is made under the conditions of to create a stress-strain curve. Initial elastic modulus is calculated | required from the first linear part of the stress-strain curve based on the following formula. Here, the stress at break was the breaking strength, and the deformation (elongation) at the break was taken as the breaking elongation. Elongation at break is the elongation required to break the film.

Initial Modulus = (F / A) / (ΔL / L ₀ )

In the formula, F is tensile stress, A is the cross-sectional area of the test sample, ΔL is the amount of change in strain (elongation), and L ₀ is the original length (length before the test) of the test sample.

In the present invention, the intermediate layer of the adhesive sheet needs to have a loss tangent (tan δ) value of 0.4 or more at 20 ° C. to 70 ° C., but when the loss tangent (tan δ) value of the intermediate layer is less than 0.4, conversion efficiency to thermal energy is achieved. Because of this deterioration, many cutting chips are generated when the adhesive sheet is cut along the outer circumference of the semiconductor wafer.

The relationship between the loss tangent (tan δ) and the "cutting debris" is not necessarily clear, but the cutting debris is generated by the force (vibration energy) transmitted from the cutting edge when cutting the adhesive sheet along the outer circumference of the wafer. In the adhesive sheet having an intermediate layer having a large value of (tan δ), it is envisaged that the cutting debris is reduced by efficiently converting and absorbing vibration energy into thermal energy due to intermolecular friction.

In the present invention, the loss tangent tan δ is a ratio of the loss modulus to the storage modulus, which is different depending on the type and temperature of the material. Loss tangent (tan delta) is calculated | required by the measuring method shown below, for example. That is, a test sample having a thickness of about 2.0 mm was set in a jig of a parallel plate having a diameter of 7.9 mm using a dynamic viscoelasticity measuring device ARES manufactured by Rheometric Co., Ltd., and a frequency of 1 Hz and a heating rate of 5 ° C./min. Find the value of the loss tangent under the conditions.

As mentioned above, the adhesive sheet of this invention has 30% or more of gel content of an intermediate | middle layer. If the gel portion of the intermediate layer is less than 30%, the supportability of the intermediate layer is lowered, and the intermediate layer is pushed out from the side surface, and a lot of cutting chips are generated when the adhesive sheet is cut along the outer circumference of the semiconductor wafer.

In this invention, a gel powder is a ratio (% display) with respect to the initial polymer amount of the residual polymer amount which remain | survives after immersing a polymer to be measured in a solvent for a predetermined period. Gel powder can be calculated | required from the quantity of the test sample which remains without dissolving in ethyl acetate, when the test sample (middle layer) is immersed in ethyl acetate solvent at 25 degreeC for 7 days.

It is preferable that the intermediate | middle layer which comprises the adhesive sheet of this invention is formed by irradiating and hardening a mixture containing a radically polymerizable monomer.

As a radically polymerizable monomer, what has a unsaturated double bond which can be radically polymerized is used, and a vinylic monomer etc. are used. In consideration of good reactivity, good adhesion (anchoring property) to the pressure-sensitive adhesive layer, easy adjustment of the elastic modulus, and the like, the vinyl monomer is preferably an acrylic monomer. In addition, in this invention, when it says "film", a sheet is included, and when it says "sheet", let it be a concept containing a film.

As an acryl-type monomer preferably used for this invention, (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, (meth Hexyl acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, (meth Isobornyl acrylate, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and the like.

In addition, vinyl acetate, vinyl propionate, styrene, acrylamide, methacrylamide, mono or diesters of maleic acid and derivatives thereof, N-methylolacrylamide, glycidyl acrylate, glycidyl methacrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminopropylmethacrylamide, 2-hydroxypropyl acrylate, acryloyl morpholine, N, N-dimethylacrylamide, N, N-diethylacrylic Monomers, such as an amide, an imide acrylate, N-vinylpyrrolidone, an oligoester acrylate, (epsilon) -caprolactone acrylate, can be copolymerized. Moreover, the kind and usage-amount of these copolymerized monomers are determined suitably in consideration of the characteristic of an intermediate | middle layer, etc.

In the present invention, polyfunctional monomers such as trimethylolpropane triacrylate and dipentaerythritol hexaacrylate can be used as crosslinking agents as necessary. Gel powder can be adjusted with the compounding quantity of a crosslinking agent.

These radically polymerizable monomers are suitably determined in kind, combination, amount of use, etc. in consideration of the polymerizability at the time of photocuring such as radiation and the properties of the high molecular weight obtained.

It is preferable that the photoinitiator is further contained in the mixture containing a vinylic monomer. Examples of the photoinitiator include benzoin ethers such as benzoin methyl ether and benzoin isopropyl ether, substituted benzoin ethers such as anisole methyl ether, 2,2-diethoxy acetophenone, and 2,2-dimethoxy-. Aromatic sulfonyl chlorides such as substituted acetophenones such as 2-phenylacetophenone, substituted α-ketols such as 1-hydroxycyclohexyl phenyl ketone, 2-methyl-2-hydroxypropiophenone, and 2-naphthalenesulfonyl chloride And photoactive oximes such as 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime and the like.

If necessary, additives commonly used, such as anti-aging agents, fillers, pigments, colorants, flame retardants, antistatic agents, ultraviolet absorbers, and the like may be added to the intermediate layer within a range not impairing the effects of the present invention. These additives are used in a normal amount according to the kind.

In the present invention, as described above, for example, a mixture containing a vinyl monomer is applied onto a substrate or on a stripped sheet (so-called peeled sheet or separator), and according to the type of photopolymerization initiator or the like, α-ray, β-ray, The intermediate layer can be photocured by irradiating ionizing radiation such as γ-rays, neutron beams, electron beams, radiation such as ultraviolet rays, and visible light.

At this time, in order to avoid the inhibition of polymerization by oxygen, the stripped sheet may be placed on a mixture containing the vinyl monomer applied on the substrate to block oxygen, and the substrate may be placed in a container filled with an inert gas to reduce the oxygen concentration. You can also get off.

In the present invention, the kind of radiation or the like and the kind of lamp used for irradiation can be appropriately selected, and can be appropriately selected, and can be selected from low pressure lamps such as fluorescent chemical lamps, black lights and germicidal lamps, and high pressure lamps such as metal halide lamps and high pressure mercury lamps. Etc. can be used.

Irradiation amount, such as an ultraviolet-ray, can be arbitrarily set according to the characteristic of the film calculated | required. In general, the radiation dose is 100 to 5,000 mJ / cm ² , preferably 1,000 to 4,000 mJ / cm ² , more preferably 2,000 to 3,000 mJ / cm ² . When the amount of radiation is less than 100 mJ / cm ² , a sufficient polymerization rate may not be obtained, while when it is more than 5,000 mJ / cm ² , deterioration may occur.

In addition, although the temperature at the time of ultraviolet irradiation is not specifically limited, Although it can set arbitrarily, when temperature is too high, it will become easy to cause a stop reaction and will cause a characteristic fall, and therefore it is usually 70 degreeC or less, Preferably it is 50 degreeC It is below, More preferably, it is 30 degrees C or less.

In the present invention, the intermediate layer may be composed of one layer, but may be a multilayered structure composed of two or more layers. In the case of a multilayer configuration, each layer constituting the intermediate layer may be the same or different.

Although the thickness of an intermediate | middle layer is suitably selected in the range which does not impair the height of the unevenness | corrugation of a wafer surface, the retention of a wafer, the protection of a wafer, etc., it is preferable that it is 20 micrometers-500 micrometers, for example, More preferably, it is 30 micrometers- It is about 200μm. If the thickness of the intermediate layer is less than 20 µm, it may not be sufficiently followable to the unevenness of the pattern surface of the wafer, and cracks or dimples may occur during grinding of the wafer. Moreover, when the thickness of an intermediate | middle layer exceeds 500 micrometers, it may take time also to apply an adhesive sheet, and work efficiency may fall, and it may not enter into a grinding machine. In addition, when peeling an adhesive sheet from a wafer, the wafer which became thin after grinding processing may be damaged by the bending stress of an adhesive sheet.

As a base material which comprises the adhesive sheet of this invention, it is preferable that the value of the loss tangent (tan-delta) in 32 degreeC is 0.1 or less, For example, polyester-based resins, such as polyethylene terephthalate (PET), polyethylene (PE), Polyolefin resins such as polypropylene (PP), polyimide (PI), polyether ether ketones (PEEK), polyvinyl chloride resins such as polyvinyl chloride (PVC), polyvinylidene chloride resins, and polyamide resins Thermosetting resins, metal foils, papers and the like are used in addition to thermoplastic resins such as polystyrene resins, fluorine resins, cellulose resins, and polycarbonate resins. It is preferable to determine suitably the material of a base material according to the use, the kind of adhesive layer provided as needed, etc., For example, when providing an ultraviolet curable adhesive, the base material with high ultraviolet transmittance is preferable.

As a material which comprises a base material, the additive etc. which are normally used as needed can be used within the range which does not impair the effect of this invention. For example, antioxidants, fillers, pigments, colorants, flame retardants, antistatic agents, ultraviolet absorbers and the like can be mentioned.

Although a base material may be single | mono layer structure, the laminated body which consists of two or more layers may be sufficient. When a base material consists of two or more laminated bodies, each layer which comprises may be a layer which consists of materials of the same composition, or the layer which consists of materials of a different composition.

The adhesive sheet of this invention has an adhesive layer on an intermediate | middle layer. It is preferable that the pressure-sensitive adhesive layer has an appropriate adhesive force when processing a product such as a semiconductor wafer and can be securely retained. The pressure-sensitive adhesive layer is preferably adhesive enough to be easily peeled off without applying a load to the product or the like after processing.

It does not specifically limit as an adhesive composition which comprises such an adhesive layer, Well-known adhesive used for adhesive fixation, such as a wafer, etc. can be used, For example, Rubber adhesive which uses rubber-based polymers, such as natural rubber and a styrene-based copolymer, as a base polymer , Acrylic pressure sensitive adhesive, silicone pressure sensitive adhesive, polyvinyl ether pressure sensitive adhesive and the like can be used. Among them, an acrylic pressure-sensitive adhesive having an acrylic polymer as a base polymer is preferable from the viewpoints of easy control of adhesion to the wafer and clean washability by organic solvents such as ultrapure water and alcohol after peeling. Do.

The base polymer constituting the pressure-sensitive adhesive may have a crosslinked structure. Such a polymer is obtained by polymerizing a monomer mixture containing monomers (such as acrylic monomers) having functional groups such as carboxyl groups, hydroxyl groups, epoxy groups, and amino groups in the presence of a crosslinking agent. Since the adhesive sheet provided with the adhesive layer containing the polymer which has a crosslinked structure improves self-retention property, it can prevent deformation | transformation of an adhesive sheet, and can hold | maintain an adhesive sheet in a flat state. Therefore, when this adhesive sheet is used, it can attach easily to a wafer correctly and using an automatic sticking apparatus etc.

It is preferable to use a radiation curable adhesive as an adhesive which comprises an adhesive layer. A radiation hardening type adhesive is obtained by mix | blending the oligomer component which hardens | cures an adhesive substance with radiation and forms a low adhesive substance, for example. When the pressure-sensitive adhesive layer is composed of a radiation-curable pressure-sensitive adhesive, plastic fluidity is imparted to the pressure-sensitive adhesive by the oligomer component, so that the adhesive is easily attached when the pressure-sensitive adhesive sheet is attached, and low adhesiveness is caused by irradiating radiation when peeling off the pressure-sensitive adhesive sheet. Since the substance is produced, it can be easily peeled off from the semiconductor wafer. Examples of the radiation used to cure the pressure-sensitive adhesive layer include X-rays, electron beams, ultraviolet rays, and the like, and since it is easy to handle, it is preferable to use ultraviolet rays, but it is not particularly limited thereto.

As a radiation-curable pressure-sensitive adhesive, in consideration of ease of molecular design, a pressure-sensitive adhesive made of an acrylic polymer having a carbon-carbon double bond in a molecule may be mentioned as a preferable one.

Examples of the acrylic polymer include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, t-butyl group, isobutyl group, amyl group, isoamyl group, hexyl group, heptyl group, cyclohexyl group and 2- Ethylhexyl group, octyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, lauryl group, tridecyl group, tetradecyl group, stearyl group, octadecyl group, dodecyl group One or two of (meth) acrylic acid alkyl esters having a straight or branched alkyl group having 30 or less carbon atoms, in particular 4 to 18 carbon atoms, and (meth) acrylic acid cycloalkyl esters (e.g., cyclopentyl esters, cyclohexyl esters, etc.) Acrylic polymer etc. which were obtained by superposing | polymerizing these, using species or more as a monomer component are mentioned. (Meth) acrylic acid ester means acrylic acid ester and / or methacrylic acid ester. In the present invention, in the case of displaying like (meth), all have the same meaning.

Acrylic polymers are copolymerizable with (meth) acrylic acid alkyl esters or cycloalkyl esters for the purpose of improving adhesiveness by introducing functional groups or polar groups, or modifying cohesion, heat resistance, etc. by controlling the glass transition temperature of the copolymer. It may include a unit corresponding to the component. Examples of such monomer components include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid; Acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, Hydroxyl group-containing monomers such as (meth) acrylic acid 10-hydroxydecyl, (meth) acrylic acid 12-hydroxylauryl, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate; Styrenesulfonic acid, allylsulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, (meth) acrylamidepropane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalenesulfonic acid Sulfonic acid group-containing monomers such as these; Phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate; Acrylamide, acrylonitrile, etc. are mentioned.

These copolymerizable monomer components can use 1 type (s) or 2 or more types. As for the usage-amount of these copolymerizable monomers, it is preferable that the compounding ratio of the (meth) acrylic-acid alkylester which is a main component, and the other monomer copolymerizable with this is 70-100 weight% of alkyl (meth) acrylic acid ester, More preferably, It is preferable that it is 85 to 95 weight%, and the other monomer copolymerizable with this is 30 to 0 weight%, More preferably, it is 15 to 5 weight%.

By mix | blending 70 mass% or more of (meth) acrylic-acid alkylesters and the other copolymerizable monomer in 30 mass% or less, the balance of adhesiveness, cohesion force, etc. can be balanced well.

In addition, the acrylic polymer may contain a polyfunctional monomer for crosslinking or the like. As such a polyfunctional monomer, for example, hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate Pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy (meth) acrylate, Polyester (meth) acrylate, urethane (meth) acrylate, etc. are mentioned. These polyfunctional monomers can also use 1 type (s) or 2 or more types. It is preferable that the usage-amount of a polyfunctional monomer is 30 weight% or less of a shearing-mer component from an adhesive characteristic etc ..

As a polymerization method for forming an acrylic polymer, any method of solution polymerization, emulsion polymerization, block polymerization, suspension polymerization, etc. may be sufficient. It is preferable that an adhesive layer is small in content of a low molecular weight substance so that the adhesive surface of products, such as a wafer, may not be polluted. In this respect, the weight average molecular weight of the acrylic polymer is preferably about 200,000 to 3 million, more preferably about 250,000 to 1.5 million.

The method for introducing a carbon-carbon double bond into an acrylic polymer as a basic skeleton is not particularly limited and various methods can be employed. In this invention, since molecular design becomes easy, it is preferable to introduce a carbon-carbon double bond into the side chain of an acryl-type polymer, and to form the base polymer which has a carbon-carbon double bond. Specifically, for example, after copolymerizing a monomer having a functional group in the acrylic polymer in advance, a compound having a functional group capable of reacting with the functional group and a carbon-carbon double bond is condensed while maintaining the radiation curability of the carbon-carbon double bond. Or by addition reaction to introduce a carbon-carbon double bond into the side chain of the acrylic polymer.

The combination example of the functional group of the monomer copolymerized to an acryl-type polymer, and the functional group which can react with this functional group is shown below. For example, a carboxylic acid group, an epoxy group, a carboxylic acid group, an aziridyl group, a hydroxyl group, and an isocyanate group etc. are mentioned. Among the combinations of these functional groups, the combination of the hydroxyl group and the isocyanate group is preferable because the reaction can be easily traced. In the combination of these functional groups, either functional group may be on the acrylic polymer side of the basic skeleton, but in the combination of the hydroxyl group and the isocyanate group, for example, the acrylic polymer has a hydroxyl group and the monomer It is preferable that the compound containing the functional group which can react with the functional group of has an isocyanate group. In this case, examples of the compound having an isocyanate group include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, m-isopropenyl-α, α-dimethylbenzyl Isocyanate is mentioned. Moreover, as an acryl-type polymer which has a functional group (here, a hydroxyl group), (meth) acrylic-acid 2-hydroxyethyl, (meth) acrylic-acid 2-hydroxypropyl, (meth) acrylic-acid 4-hydroxybutyl, (meth) acrylic acid One having a hydroxyl group-containing monomer such as 6-hydroxyhexyl, and an ester bond in the molecule thereof, a 2-hydroxyethyl vinyl ether compound, a 4-hydroxybutyl vinyl ether compound, a diethylene glycol monovinyl ether compound And the like copolymerized with an acrylic polymer.

Although the radiation hardening type adhesive can use the base polymer which has a carbon-carbon double bond independently, you may mix | blend a radiation curable oligomer component in the range which does not deteriorate a characteristic.

As a radiation curable oligomer used for this invention, various oligomers, such as a urethane type, a polyether type, polyester type, a polycarbonate type, and a polybutadiene type, are mentioned, It can also be used combining these in this invention.

In the case of the pressure-sensitive adhesive in which the radiation-curable oligomer component is blended, the oligomer component may move during storage of the adhesive tape, and change due to storage is likely to occur. Therefore, the compounding quantity of a radiation curable oligomer component etc. is 30 weight part or less with respect to 100 weight part of base polymers normally, Preferably it is the range of 0-10 weight part.

When hardening by the ultraviolet-ray etc., the said radiation curable adhesive contains a photoinitiator. As a photoinitiator, 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2- propyl) ketone, (alpha)-hydroxy- (alpha), (alpha) '-dimethylacetophenone, 2-methyl- 2-, Α-ketol compounds such as hydroxypropiophenone and 1-hydroxycyclohexylphenyl ketone; Methoxy acetophenone, 2,2-dimethoxy-2-phenyl acetophenone, 2,2-diethoxy acetophenone, 2-methyl-1- [4- (methylthio) -phenyl] -2-morphopoly Acetophenone-based compounds such as nopropane-1; Benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether and anisoin methyl ether; Ketal compounds such as benzyl dimethyl ketal; Aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; Photoactive oxime compounds such as 1-phenone-1,1-propanedione-2- (o-ethoxycarbonyl) oxime; Benzophenone compounds such as benzophenone, benzoylbenzoic acid and 3,3'-dimethyl-4-methoxybenzophenone; Thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethyl thioxanthone, isopropyl thioxanthone, 2,4-dichlorothioxanthone, 2,4-diethyl Thioxanthone-based compounds such as thioxanthone and 2,4-diisopropyl thioxanthone; Camphorquinone, halogenated ketones, acylphosphine oxides, acyl phosphonates, and the like.

The compounding quantity of a photoinitiator is 1-10 weight part, Preferably it is about 3-5 weight part with respect to 100 weight part of base polymers, such as an acryl-type polymer which comprises an adhesive.

As the radiation-curable pressure-sensitive adhesive of the present invention, known crosslinking agents such as epoxy crosslinking agents, aziridine crosslinking agents, and isocyanate crosslinking agents such as polyisocyanates can be used.

The pressure-sensitive adhesive layer may contain a component that foams or expands upon heating. As the heat-expandable or expandable component, for example, thermally expandable microspheres in which a substance easily gasified by heating, such as isobutane, propane, or the like, is contained in an elastic shell. Moreover, as such a thermal expansion microsphere, the brand name "microsphere" made by Matsumoto Oil Holding Co., Ltd. can be obtained as a commercial item, for example. By incorporating a heat-expandable or heat-expandable component into the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is expanded by heat treatment after the grinding processing of the wafer, and the adhesion area between the pressure-sensitive adhesive layer and the wafer is significantly reduced, so that the pressure-sensitive adhesive sheet is easily removed from the wafer. It can peel off.

In this invention, although the elasticity modulus of an adhesive layer can be suitably set within the range which does not impair the adhesiveness or retention with respect to a wafer, Preferably it is 10-1,000 kPa. If the elastic modulus of the pressure-sensitive adhesive layer is less than 10 kPa, the pressure-sensitive adhesive layer may be softened, so that the retention and protection of the wafer may be lowered. When the pressure-sensitive adhesive layer exceeds 1,000 kPa, the initial adhesive strength may not be obtained.

Although the thickness of an adhesive layer can be suitably set in the range which does not impair the holding property and protective property of a wafer, Preferably it is 1-100 micrometers, More preferably, it is about 2-60 micrometers. If the thickness of the pressure-sensitive adhesive layer is less than 1 μm, there is a risk of precipitation of the intermediate layer due to the breakdown of the pressure-sensitive adhesive layer. On the other hand, if the thickness of the pressure-sensitive adhesive layer exceeds 100 μm, it becomes difficult to follow the unevenness of the wafer surface when the adhesive sheet is attached to the wafer.

In the present invention, the pressure-sensitive adhesive layer may be formed by directly applying the above-described pressure-sensitive adhesive on a middle layer using a solvent or the like as necessary, or after applying the pressure-sensitive adhesive to a release liner or the like to form the pressure-sensitive adhesive layer in advance, the pressure-sensitive adhesive layer is applied to the middle layer. It may be formed by joining.

The ratio of the thickness t1 of the intermediate | middle layer in the adhesive sheet of this invention and the thickness t2 of an adhesive layer can be suitably selected according to the objective. In particular, when used for the processing of precision parts, the thickness ratio (t2 / t1) to the intermediate layer of the pressure-sensitive adhesive layer is preferably t2 / t1 = 0.01 to 0.5, more preferably from 0.02 to about 0.3. If the thickness ratio (t2 / t1) of the pressure-sensitive adhesive layer and the intermediate layer is less than 0.01, the adhesive force may not be sufficiently reduced after irradiation, and peeling may be difficult. On the other hand, if the thickness ratio (t2 / t1) exceeds 0.5, the intermediate layer This effect is not exerted and the followability to the unevenness of the wafer pattern surface is less likely to be exhibited, so that cracks and dimples are more likely to occur during grinding of the wafer.

Next, an example of embodiment of the adhesive sheet of this invention is demonstrated using drawing. In FIG. 1, the intermediate | middle layer 2 and the adhesive layer 3 are provided on the base material 1. As shown in FIG. Moreover, this base material 1 may be a laminate of two or more layers, or the intermediate layer 2 may be a laminate of two or more layers. In addition, a peeling separator (not shown) may be provided on the pressure-sensitive adhesive layer 3, and is required between the base material 1 and the intermediate layer 2 and / or between the intermediate layer 2 and the pressure-sensitive adhesive layer 3. Other layers may be installed depending on the location.

The adhesive sheet of this invention is used according to the conventional method at the time of processing products, such as a wafer, for example. Here, the example used when grinding the back surface of a semiconductor wafer is shown. First, the semiconductor wafer is placed on a table so that a pattern surface such as an IC circuit is placed on the table, and the adhesive sheet of the present invention is superimposed on the pattern surface so that the pressure-sensitive adhesive layer is in contact with each other, and the pressure means such as a pressing roll is applied. It affixes, while pressing. Alternatively, after placing the semiconductor wafer and the adhesive sheet as described above in a pressurized container (for example, an autoclave), the inside of the container may be pressurized to bond the semiconductor wafer and the adhesive sheet together with a pressing means. You may. Moreover, a semiconductor wafer and an adhesive sheet may be adhere | attached in a vacuum chamber, and it may adhere | attach by heating to the temperature below melting | fusing point of an adhesive sheet base material.

As a back surface grinding processing method of a semiconductor wafer, the normal reduction method can be employ | adopted. For example, the back surface of the semiconductor wafer to which the adhesive sheet is adhered as described above is used as a processing machine for polishing to reduce the thickness to a desired thickness using a pad for back grinding, a CMP (Chemical Mechanical Polishing), or the like. Do it. When using the adhesive sheet which formed the adhesive layer using the radiation-curable adhesive, it is peeled after irradiating a radiation etc. at the time of finishing reduction, to reduce the adhesive force of an adhesive layer.

Example

Although an Example demonstrates this invention in detail below, this invention is not limited to this. In addition, in a following example, a part means a weight part.

(Example 1)

In a reaction vessel equipped with a cooling tube, a thermometer, and a stirring device, 100 parts of 2-ethylhexyl acrylate and 10 parts of acrylic acid as acrylic monomers, and 1-hydroxycyclohexylphenyl ketone as a photopolymerization initiator (registered trademark "IRGACURE (IRGACURE) ) 184, Chiba Specialty Chemical Co., Ltd.) 0.35 parts and 2,2-dimethoxy-1,2-diphenylethan-1-one (registered trademark "irgacure 651", Chiba Specialty Co., Ltd.) 0.35 part of Chemical Co., Ltd. was injected | thrown-in, it exposed to ultraviolet-ray in nitrogen atmosphere, and thickened by partially photopolymerizing, and produced the syrup containing a prepolymer.

Subsequently, 0.2 part of trimethylol propane triacrylate was added to this partially polymerized syrup as a polyfunctional monomer, and it stirred, and apply | coated so that the thickness after hardening might be set to 300 micrometers on the peeling process PET film (38 micrometers in thickness). After the PET film (38 micrometers in thickness) which peeled off was coat | covered on this as a separator, the coated PET film surface was irradiated with ultraviolet-ray (roughness 170mW / cm <^2> , light quantity 2500mJ / cm <^2> ) using a high pressure mercury lamp, After hardening and forming the intermediate | middle layer on a PET film, this PET film and separator were removed and the intermediate | middle layer was obtained. About the obtained intermediate | middle layer, the gel powder was calculated | required based on the method demonstrated previously, the loss tangent (tan-delta) was calculated | required by dynamic viscoelasticity test, and the initial elastic modulus was calculated | required by the tension test. The value is shown in Table 1.

An ethylene-vinyl acetate copolymer (EVA) film having a thickness of 115 µm was used as the substrate layer, and an intermediate layer (300 µm) was provided on the substrate layer as described above.

Next, the compound consisting of 78 parts of ethyl acrylate, 100 parts of butyl acrylate, and 40 parts of 2-hydroxyethyl acrylate was copolymerized in a toluene solution to obtain an acrylic copolymer polymer having a number average molecular weight of 300,000. 43 parts of 2-methacryloyloxyethyl isocyanate were addition-reacted with respect to this acryl-type copolymer polymer, and the carbon-carbon double bond was introduce | transduced into the side chain in a polymer molecule. To 100 parts of the polymer, a UV-curable pressure-sensitive adhesive obtained by mixing 1 part of a polyisocyanate-based crosslinking agent and 3 parts of acetophenone-based photopolymerization initiator was applied onto the intermediate layer surface formed on the substrate to form a pressure-sensitive adhesive layer having a thickness of 30 μm. The adhesive sheet which has the laminated constitution of / intermediate | middle layer / adhesive layer was produced.

The obtained adhesive sheet was evaluated for cutting chips and wafer cracking. That is, the obtained adhesive sheet was affixed on the bumped wafer of 240 micrometers in height, the adhesive sheet was cut | disconnected along the outer periphery of the wafer, and the crumb was evaluated. The results are shown in Table 1.

(Example 2)

In Example 1, except having used 100 parts of lauryl acrylate and 10 parts of acrylic acid as an acryl-type monomer, the intermediate | middle layer was formed like Example 1, and the adhesive sheet which has a base material, an intermediate | middle layer, and an adhesive layer in this order was produced. Moreover, the gel powder of this intermediate | middle layer was 71%. The obtained intermediate layer and the adhesive sheet were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)

In Example 1, except having used 100 parts of butyl acrylates and 10 parts of acrylic acid as an acryl-type monomer, the intermediate | middle layer was formed like Example 1, and the adhesive sheet which has a base material, an intermediate | middle layer, and an adhesive layer in this order was produced. Moreover, the gel powder of this intermediate | middle layer was 66%. The obtained intermediate layer and the adhesive sheet were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)

In Example 1, except having not used a polyfunctional monomer, the intermediate | middle layer was formed like Example 1, and the adhesive sheet which has a base material, an intermediate | middle layer, and an adhesive layer in this order was produced. Moreover, the gel powder of this intermediate | middle layer was 1%. The obtained intermediate layer and the adhesive sheet were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)

In Example 1, except that 70 parts of butyl acrylate, 30 parts of ethyl acrylate, and 10 parts of acrylic acid were used as an acryl-type monomer, the intermediate | middle layer was formed like Example 1, and the adhesive sheet which has a base material, an intermediate | middle layer, and an adhesive layer in this order is carried out. Made. Moreover, the gel powder of this intermediate | middle layer was 75%. The obtained intermediate layer and the adhesive sheet were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Evaluation test

(1) evaluation of cutting chips

An adhesive sheet was bonded to 25 sheets of 625 μm thick (not including bumps) formed with bumps having a height of 240 μm using DR-8500II manufactured by Nitto Seiki Co., Ltd. . Then, the adhesive sheet was cut | disconnected along the outer periphery of the wafer by the cutting blade (edge temperature of 60 degreeC of a blade) heated to 150 degreeC. The side of the adhesive sheet after cutting was observed with respect to any one of 25 wafers using the optical microscope (100 times and 200 times), and the number of the lumps (cutting debris) 100 micrometers or more was counted.

(2) Evaluation of Wafer Cracking

An adhesive sheet was bonded to 25 sheets of 625 μm thick (not including bumps) having a bump of 240 μm in height by using Nitto Seiki Co., Ltd. DR-8500II. The wafer which bonded this adhesive sheet was ground to 200 micrometers in thickness by the silicon wafer reducer by Disco Co., Ltd., and the longevity which the crack generate | occur | produced in the wafer was counted.

As is apparent from Table 1, the adhesive sheets of Examples 1 and 2 of the present invention had a small number of cutting debris, and even when a wafer was polished to a thickness of 200 µm using this adhesive sheet, no crack was generated.

On the other hand, the adhesive sheet of Comparative Example 1 having an intermediate layer having a loss tangent (tan δ) of less than 0.4 and the adhesive sheet of Comparative Example 2 having an intermediate layer having a gel content of less than 30% had a large number of cutting chips and an initial elastic modulus of 0.5 N /. The adhesive sheet of Comparative Example 3 having an intermediate layer larger than ² mm had three cracks in the wafer.

That is, according to this invention, even if the height difference of the unevenness | corrugation of the semiconductor wafer surface is large, it is an adhesive sheet which can follow the unevenness | corrugation, and the semiconductor phase generate | occur | produces the cutting chip | wreckage of the adhesive sheet at the time of cut | disconnecting even if the adhesive sheet is bonded to the surface. This small adhesive sheet can be realized.

Industrial availability

The adhesive sheet of this invention can be used suitably as an adhesive sheet for wafer processing used at the time of reducing the back surface of a wafer, or at the time of dicing. In addition, the surface protection and the damage prevention in the use of various applications involving peeling of the adhesive sheet at the time of use or after the end of use, such as various industrial members, especially semiconductors, circuits, various printed boards, various masks, lead frames, etc. It can be used widely as an adhesive sheet used for the purpose.

According to the present invention, when processing a product such as a semiconductor product or an optical product, it is an adhesive sheet that can follow the unevenness even if the height difference of the unevenness on the product surface is large, and the adhesive sheet of the present invention is bonded to a semiconductor wafer, for example. When the adhesive sheet is cut along the outer circumference of the semiconductor wafer, the adhesive sheet with less generation of cutting chips from the side surface of the adhesive sheet can be provided. Moreover, according to this invention, the method of manufacturing this adhesive sheet, and the method of processing a product etc. using this adhesive sheet can be provided.

Claims (17)

An adhesive sheet having an intermediate layer and an adhesive layer on one surface of a substrate in this order, wherein the intermediate layer has an initial elastic modulus of 0.5 N / mm ² or less and a value of loss tangent (tan δ) of 20 ° C. to 70 ° C. of 0.4 or more. And a gel content of 30% or more. The method of claim 1, The intermediate sheet is formed by irradiating radiation. The method of claim 2, The adhesive sheet of the said ultraviolet-ray irradiation amount is 100mJ / cm <^2> or more and 5000mJ / cm <^2> or less. The method of claim 1, And the pressure-sensitive adhesive layer is formed using a radiation curable acrylic polymer having a carbon-carbon double bond in a molecule. The method of claim 1, The adhesive sheet characterized by the ratio (t1 / t2) of the thickness t1 of the said intermediate | middle layer and the thickness t2 of the said adhesive layer being 0.01 or more and 0.5 or less. The method of claim 1, The adhesive sheet which has a peeling separator on the said adhesive layer. The method of claim 1, A pressure sensitive adhesive sheet, which is used for holding and / or protecting a product in a process of precisely processing a semiconductor wafer. The method of claim 1, The intermediate | middle layer is formed using the acryl-type polymer. The method of claim 8, The intermediate sheet is formed by irradiating radiation. The method of claim 9, The adhesive sheet of the said ultraviolet-ray irradiation amount is 100mJ / cm <^2> or more and 5000mJ / cm <^2> or less. The method of claim 8, And the pressure-sensitive adhesive layer is formed using a radiation curable acrylic polymer having a carbon-carbon double bond in a molecule. The method of claim 8, The adhesive sheet characterized by the ratio (t1 / t2) of the thickness t1 of the said intermediate | middle layer and the thickness t2 of the said adhesive layer being 0.01 or more and 0.5 or less. The method of claim 8, The adhesive sheet which has a peeling separator on the said adhesive layer. The method of claim 8, A pressure sensitive adhesive sheet, which is used for holding and / or protecting a product in a process of precisely processing a semiconductor wafer. By applying a mixture containing a radical polymerizable monomer to one side of the substrate and irradiating and curing, the initial elastic modulus is 0.5 N / mm ² or less, and the value of loss tangent (tan δ) at 20 ° C. to 70 ° C. is obtained. A method for producing a pressure sensitive adhesive sheet, wherein an intermediate layer having 0.4 or more and a gel component of 30% or more is formed, and an adhesive layer is formed on the intermediate layer. The method of claim 15, The said radically polymerizable monomer is an acryl-type monomer, The manufacturing method of the adhesive sheet characterized by the above-mentioned. A method for processing a product, wherein the pressure sensitive adhesive sheet according to claim 1 is bonded to a product to be precision machined and precisely processed in a retained and / or protected state.

Images